JP5182098B2 - Optical film, and polarizing plate and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to an optical film having a cellulose ester formed by a melt casting method, a polarizing plate using the same, and a liquid crystal display device.

  An optical film having a cellulose ester (hereinafter, also simply referred to as a cellulose ester film) has a high transparency, low birefringence, easy adhesion to a polarizer, and the like. As an optical film for protecting a polarizer used in a liquid crystal display device, it has been often used for a polarizing plate or the like. In addition, as other uses for liquid crystal display devices, various functional films such as retardation films, viewing angle widening films, antireflection films used in plasma displays, and various functional films used in organic EL displays, etc. Can also be used.

  In recent years, the production volume of liquid crystal display devices has greatly increased due to the thinness and lightness of the depth, and the demand for liquid crystal display devices has increased. In addition, televisions using liquid crystal display devices are characterized by being thin and light, and large television sets that have not been achieved with televisions using cathode ray tubes have been produced. There is an increasing demand for constituent polarizers and polarizing plate protective films. As the polarizing plate protective film, a cellulose ester film is generally used because of its excellent optical properties.

  Until now, these cellulose ester films have been produced exclusively by the solution casting method. The solution casting method is a film forming method in which a solution obtained by dissolving cellulose ester in a solvent is cast to obtain a film shape, and then the solvent is evaporated and dried to obtain a film. Since a film formed by the solution casting method has high flatness, a high-quality liquid crystal display device without unevenness can be obtained using the film.

  However, the solution casting method requires a large amount of an organic solvent and has a problem that the environmental load is large. Cellulose ester film is formed using a halogen-based solvent with high environmental impact due to its dissolution characteristics, so it is particularly required to reduce the amount of solvent used, and the production of cellulose ester film is increased by solution casting film formation. It has become difficult to do. For this reason, the film forming method which does not use an organic solvent, for example, the film forming method by heat melting is desired.

  On the other hand, as a cellulose ester film used as a protective film used for a polarizing plate of a liquid crystal display device, a cellulose triacetate film has been conventionally used. The polarizing plate generally has a structure in which both sides of a polarizing film made of a polyvinyl alcohol film or the like on which iodine or dye is adsorbed and oriented are laminated with a transparent resin layer, and the cellulose triacetate film is the transparent resin layer. Has been used as well. However, when cellulose triacetate, which is a cellulose ester generally used in solution casting film formation, is applied to melt film formation, cellulose triacetate is a cellulose ester whose melting start temperature is higher than the decomposition start temperature. It is difficult to use for a film.

  In recent years, by substituting cellulose ester with a specific ratio of propionyl group or butyryl group in addition to acetyl group, for silver salt photography (for example, see Patent Document 1) or for polarizing plate protective film (for example, Patent Document 2). 3)), attempts have been made to melt film-form such cellulose esters. A high substitution degree of propionyl group or butyryl group is advantageous for melt film formation because the viscosity at the time of melting is small, but on the other hand, the mechanical strength as a film after film formation is inferior, for silver salt photography, It became clear that it had the subject that it did not fulfill a function also for polarizing plate protective films. On the other hand, if the substitution degree of propionyl group or butyryl group is low, the mechanical strength increases, but on the other hand, the viscosity at the time of melting increases, and it is difficult to level even if extruded from a die and cast on a cooling drum or cooling belt. Unevenness and pressure unevenness are likely to occur. As a result, it has been found that the obtained film has problems such as poor flatness and curl properties, which are physical characteristics, and also has a problem that the variation of retardation, which is optical characteristics, is large.

  It is known to add a specific deterioration inhibitor when melt-forming a cellulose ester (see, for example, Patent Document 4). It is well known to prevent deterioration of chemical properties (coloring and molecular weight) of polymer materials by adding deterioration inhibitors. However, the combination of polymer materials and deterioration inhibitors is not appropriate. The problem is that the polymer material is deteriorated rather than the effect. By the way, although there is no deterioration of the chemical characteristics, the optical characteristics may be deteriorated. In such a case, when a cellulose ester is used for optical applications, it is fatal, and it is a problem to select an appropriate deterioration preventing agent for the polymer material. On the other hand, not only the stability at the time of melt film formation but also the stability after melt film formation is important for the cellulose ester to be melt-formed. In other words, it is important that there is no problem during the period in which some product is assembled using cellulose ester and the product is delivered to the consumer and used. In the conventionally known technique, there is a problem in achieving both long-term stability at the time of melt film formation and after melt film formation, and the construction of a more advanced stabilization technique has been desired.

  By the way, when making a polarizing plate by laminating a protective film and a polarizer, in order to make it easy to apply a water-soluble adhesive, the triacetyl cellulose film is immersed in a high-temperature, high-concentration alkaline solution, so-called saponification. After the treatment to make the film surface hydrophilic, an adhesive is applied and bonded to the polarizer.

  Triacetyl cellulose has been used exclusively for the transparent resin film for polarizing plate protective film because of its easy adhesion with the polarizer, but as one of the reasons that it is not yet replaced by other films, polyester film, polycarbonate film, Another polymer film such as a cyclic olefin resin film has a reason that easy adhesion with a polarizer cannot be obtained even if it is saponified.

  Attempts have been made to improve various performances of cellulose ester films by defining the degree of substitution of fatty acids such as acyl groups of cellulose esters, such as acetyl, propionyl, or butyryl groups (eg, patents). Reference 5). Cellulose ester films substituted with a specific proportion of propionyl groups and butyryl groups as well as acetyl groups are more adhesive than polymer films other than cellulose esters, but have a degree of substitution of propionyl groups and butyryl groups. If it is too high, it has been found that the saponification treatment is difficult to proceed, and as a result, there is a problem that the adhesiveness is inferior, and that mechanical properties and optical properties are insufficient. In particular, when the propionyl group and the butyryl group were compared, it was found that the mechanical and optical properties were greatly deteriorated by the bonding of the butyryl group, despite the difference in the number of carbon atoms.

  Therefore, instead of the triacetyl cellulose film formed by the solution casting method, it has excellent environmental suitability, high flatness, suitability for saponification treatment, little curling property, and little variation in retardation, and further over a long period of time. The appearance of a melt-formed optical film with good durability is awaited.

  By the way, these cellulose ester films are usually wound around a core to form a film original, which is stored and transported. For this reason, when the melt-formed film is stored for a long time in the state of the film roll wound on the core, the film is used when the horse's spine failure or the core portion of the film roll starts a failure called core transfer and starts winding. It was found that there is a problem that wrinkles are likely to occur.

  The horse's back failure is a failure in which the original film is deformed into a U shape like the horse's back, and a belt-like convex part is formed at a pitch of about 2 to 3 cm near the center, and the film remains deformed. This is a problem because the surface becomes distorted when processed into a polarizing plate. Until now, horse back failure has been reduced by reducing the coefficient of dynamic friction between the bases and adjusting the height of the knurling (embossing) on both sides.

  Further, the core transfer is a failure due to film deformation caused by the irregularities of the core or film.

  These failures did not become a big problem in the film produced by the conventional solution casting, but it was found that the film produced by the melt film formation becomes a big problem because the flatness of the film is low.

In particular, in recent years, with the increase in size of the screen, it is desired that the width of the original film is wide and the winding length is long. For this reason, the original film becomes wide and the original film load tends to increase, and these faults are more likely to occur, and therefore improvement is desired.
Japanese National Patent Publication No. 6-501040 JP 2000-352620 A JP 2006-1111796 A JP 2006-241428 A JP 2006-111842 A

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is an optical film formed by melt film having excellent environmental suitability, good mechanical properties, optical properties, and good durability. Is an optical film that does not cause deformation failure of the original film such as a horse back failure or a convex failure, an optical film that has high flatness and suitability for saponification treatment, and has small fluctuations in curling property and retardation, and the optical film An object of the present invention is to provide a polarizing plate having good durability over a long period of time using a film and a liquid crystal display device in which high contrast is achieved.

  As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that all the problems can be solved by using a film melt-formed by a cellulose ester having a specific type and amount of a certain substituent. The present invention has been completed.

  That is, the said subject of this invention is achieved by the following structures.

1. In an optical film obtained by heating and melting a film-forming material containing at least one plasticizer and a cellulose ester, and forming a film by a melt casting method, the type and degree of substitution of the cellulose ester are represented by the following formula (1). optical film meets ~ conditions (4) simultaneously, and the film forming material, characterized in that further contains at least one alkyl radical scavenger.

Formula (1) 1.25 ≦ X ≦ 1.43
Formula (2) 1.15 ≦ Y ≦ 1.33
Formula (3) 2.40 ≦ X + Y <2.75
Formula (4) -0.05 <= XY <0.20
[Wherein, X represents the degree of substitution with an acetyl group, and Y represents the degree of substitution with a propionyl group. ]
2. 2. The optical film as described in 1 above, wherein a 1% mass reduction temperature Td (1.0) of the cellulose ester in air is 270 ° C. or higher.

  3. 3. The optical film as described in 1 or 2 above, wherein the film-forming material further contains at least one phenolic compound.

4). 4. The optical film according to any one of 1 to 3, wherein the film-forming material further contains at least one phosphorous compound.
5. 5. The optical film as described in 3 or 4 above, wherein the phenolic compound is a hindered phenolic compound.
6). 6. The optical film as described in 4 or 5 above, wherein the phosphorus compound is a phosphonite compound.
7). 7. The optical system according to any one of 1 to 6, wherein the alkyl radical scavenger is a compound represented by the following general formula (1) or a compound represented by the following general formula (2). the film.

[Wherein, R ₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ₂ and R ₃ each independently represents an alkyl group having 1 to 8 carbon atoms. ]

[Wherein, R _{12 to} R ₁₅ each independently represent a hydrogen atom or a substituent, R ₁₆ represents a hydrogen atom or a substituent, and n represents an integer of 1 to 4. When n is 1, R ₁₁ represents a substituent, and when n is an integer of 2 to 4, R ₁₁ represents a bivalent to tetravalent linking group. ]
8). The optical film according to any one of claims 1 to 7, wherein the plasticizer is a polyhydric alcohol ester.
9. 9. The optical film as described in any one of 1 to 8 above, wherein the film-forming material further contains a benzotriazole compound.
10. A polarizing plate comprising the optical film according to any one of 1 to 9 on at least one surface of a polarizer.
11. 11. A liquid crystal display device using the polarizing plate described in 10 above on at least one surface of a liquid crystal cell.

  According to the present invention, an optical film which does not cause deformation failure of the film raw material such as a horse back failure or a convex failure, flatness, high saponification suitability, and an optical film having a small variation in curling property and retardation, and A polarizing plate having good durability over a long period of time and a liquid crystal display device having high contrast achieved using the optical film can be provided.

It is a general | schematic flow sheet which shows one embodiment of the apparatus which enforces the manufacturing method of the cellulose-ester film which concerns on this invention. It is a principal part expansion flow sheet of the manufacturing apparatus of FIG. 3A is an external view of the main part of the casting die, and FIG. 3B is a cross-sectional view of the main part of the casting die. It is sectional drawing of 1st Embodiment of a pinching rotary body. It is sectional drawing in the plane perpendicular | vertical to the rotating shaft of 2nd Embodiment of a pinching rotary body. It is sectional drawing in the plane containing the rotating shaft of 2nd Embodiment of a pinching rotary body. It is a disassembled perspective view which shows the outline of the block diagram of a liquid crystal display device. It is a figure which shows the state of the storage of a cellulose-ester film original fabric.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Cellulose acylate film 12 Stretcher 16 Winding device 21a, 21b Protective film 22a, 22b Retardation film 23a, 23b Film slow axis direction 24a, 24b Transmission of polarizer Axial direction 25a, 25b Polarizers 26a, 26b Polarizer 27 Liquid crystal cell 29 Liquid crystal display device 31 Die body 32 Slit 41 Metal sleeve 42 Elastic roller 43 Metal inner cylinder 44 Rubber 45 Cooling water 51 Outer cylinder 52 Inner cylinder 53 Space 54 Coolant 55a, 55b Rotating shaft 56a, 56b Outer cylinder support flange 60 Fluid shaft cylinder 61a, 61b Inner cylinder support flange 62a, 62b Intermediate passage 110 Winding core body 117 Support plate 118 Base 120 Cellulose ester film original fabric

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The present invention provides an optical film having good mechanical properties and optical properties and good durability. By using such an optical film, it is possible to obtain a high-quality optical film such as a polarizing plate protective film, an antireflection film, a retardation film, and a high-quality liquid crystal display device. .

  The present invention is characterized in that a cellulose ester film formed by melt casting is used as an optical film. In the present invention, the film-forming material is heated to a flowable state without being dissolved in a solvent as in solution casting, and casting is defined as a melt casting method.

  More specifically, the heat melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent.

  The melt casting method of the present invention includes a method in which the film forming material is heated to exhibit its fluidity and then extruded and formed on a drum or an endless belt as a melt casting film forming method.

  The optical film of the present invention is formed by melt-casting a film-forming material containing at least one plasticizer and the following cellulose ester, preferably at a melting temperature of 200 ° C. or more and 270 ° C. or less, and formed by a melt casting method. It is the characteristic that it is made optical film.

  Hereinafter, each film forming material will be described.

《Cellulose ester》
The cellulose ester used in the melt casting method of the present invention is a cellulose ester that simultaneously satisfies the following formulas (1) to (4) when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group is Y. Such cellulose esters are usually called cellulose acetate propionate. Note that satisfying any one, any two, or any three of the following formulas does not solve all of the above problems, but it is important to satisfy all four simultaneously.

Formula (1) 1.25 ≦ X ≦ 1.43
Formula (2) 1.15 ≦ Y ≦ 1.33
Formula (3) 2.40 ≦ X + Y <2.75
Formula (4) -0.05 <= XY <0.20
Among them, it is preferable to satisfy 1.30 ≦ X ≦ 1.42 for the formula (1), and preferably 1.18 ≦ Y ≦ 1.32 for the formula (2). For 3), it is preferable to satisfy 2.50 ≦ X + Y ≦ 2.73, and for Formula (4), 0.01 ≦ X−Y ≦ 0.18 is preferable.

  Next, the substitution degree of the acyl group (acetyl group and propionyl group) of the cellulose ester used in the present invention will be described in detail.

  Cellulose has a total of three hydroxyl groups, one at each of the 2nd, 3rd and 6th positions of a 1-glucose unit. The total degree of substitution is the average number of units per 1-glucose unit. It is a numerical value indicating whether an acyl group is bonded. Accordingly, the maximum degree of substitution is 3.00, and the portion not substituted with the acyl group is usually present as a hydroxyl group. The 2nd and 3rd positions are secondary hydroxyl groups, and the 6th position is a primary hydroxyl group. The higher order structure and physical properties of the cellulose ester depend on which position the acetyl group and propionyl group are substituted in. May vary slightly. However, in the optical film of the present invention, any substitution position and ratio of each of the acetyl group and the propionyl group may be any cellulose ester that simultaneously satisfies the conditions of the above formulas (1) to (4). It can be preferably used. In addition, the substitution degree of an acetyl group and a propionyl group is obtained by a method specified in ASTM D817-96.

  The cellulose ester used in the present invention preferably has a number average molecular weight (Mn) of 50,000 to 150,000, more preferably a number average molecular weight of 55,000 to 120,000, and a number average molecular weight of 60000 to 100,000. Most preferred.

  Further, the cellulose ester used in the present invention preferably has a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 1.3 to 5.5, particularly preferably 1.5 to 5.0. More preferably, it is 1.7-4.0, More preferably, the cellulose ester of 2.0-3.5 is used preferably.

  Mn and Mw / Mn can be calculated by gel permeation chromatography (GPC) in the following manner.

  The measurement conditions are as follows.

Solvent: Tetohydrofuran Equipment: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Injection volume: 10 μl
Flow rate: 0.6 ml / min
Calibration curve: Standard polystyrene: PS-1 (manufactured by Polymer Laboratories) Mw = 2, 560,000 to 580, a calibration curve with 9 samples was used.

  By making the cellulose ester in the film-forming material in the range of 70% by mass to 99% by mass, excellent melt castability and stability in the presence of additives such as deterioration inhibitors, plasticizers and ultraviolet absorbers described later. The obtained film can impart excellent performance as an optical film. When the content of the cellulose ester is 70% by mass or less, the additive bleeds out and the mechanical strength of the film is decreased, which is not preferable. Further, when the amount of other additives necessary as an optical film is 1.0% by mass or less (the content of cellulose ester is 99% or more), it is difficult to satisfy the required physical properties. More preferably, the cellulose ester content is 80 to 95% by mass.

  The cellulose ester raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

  The cellulose ester of the present invention can be synthesized with reference to known methods. For example, the acetyl group and propionyl group can be substituted by acetylating and propionating the hydroxyl group of the raw material cellulose by acetic anhydride and propionic anhydride by a conventional method. The method for synthesizing such a cellulose ester is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040. In addition, the cellulose ester which satisfy | fills said Formula (1)-(4) simultaneously can be synthesize | combined by changing suitably the usage-amount of the acetic anhydride and propionic anhydride to be used.

  The alkaline earth metal content of the cellulose ester used in the present invention is preferably in the range of 1 to 50 ppm. If it exceeds 50 ppm, lip adhesion stains increase or breakage tends to occur at the slitting part during or after hot stretching. Even if it is less than 1 ppm, it tends to break, but the reason is not well understood. Furthermore, the range of 1-30 ppm is preferable. The alkaline earth metal as used herein refers to the total content of Ca and Mg, and can be measured using an X-ray photoelectron spectrometer (XPS).

  The residual sulfuric acid content in the cellulose ester used in the present invention is preferably in the range of 0.1 to 45 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 45 ppm, the deposits on the die lip during heat melting increase, such being undesirable. Moreover, since it becomes easy to fracture | rupture at the time of slitting at the time of hot drawing or after hot drawing, it is not preferable. Less is preferable, but if it is less than 0.1, it tends to break on the contrary, it is not preferable, but the reason is not well understood. Furthermore, the range of 1-30 ppm is preferable. The residual sulfuric acid content can be measured by the method prescribed in ASTM D817-96.

  The free acid content in the cellulose ester used in the present invention is preferably 1 to 500 ppm. If it exceeds 500 ppm, deposits on the die lip will increase and breakage will easily occur. Furthermore, it is preferable that it is the range of 1-100 ppm, and also it becomes difficult to fracture | rupture. A range of 1 to 70 ppm is particularly preferable. The free acid content can be measured by the method prescribed in ASTM D817-96.

  By washing the synthesized cellulose ester more sufficiently than when used in the solution casting method, the residual alkaline earth metal content, residual sulfuric acid content, and residual acid content are within the above ranges. This is preferable. In addition to washing with water, cellulose ester can be washed with a poor solvent such as methanol or ethanol, or as a result, a mixed solvent of a poor solvent and a good solvent can be used as a poor solvent. Low molecular organic impurities can be removed. Further, the washing of the cellulose ester is also preferably performed in the presence of a deterioration inhibitor, and the heat resistance and film forming stability of the cellulose ester are improved. The deterioration preventing agent used is not limited as long as it is a compound that inactivates radicals generated in the cellulose ester or suppresses deterioration of the cellulose ester caused by addition of oxygen to the radical generated in the cellulose ester. be able to.

  In order to improve the heat resistance, mechanical properties, optical properties, etc. of cellulose ester, dissolve it in a good solvent of cellulose ester, reprecipitate it in a poor solvent, filter it, or stir and suspend it in the poor solvent. The low molecular weight component of cellulose ester and other impurities can be removed by filtration. At this time, it is preferable to carry out in the presence of a deterioration preventing agent, similarly to the above-described washing of the cellulose ester.

  The deterioration inhibitor used for washing the cellulose ester may remain in the cellulose ester after washing. The remaining amount is preferably 0.01 to 2000 ppm, more preferably 0.05 to 1000 ppm. More preferably, it is 0.1-100 ppm.

  Furthermore, another polymer or a low molecular weight compound may be added after the cellulose ester reprecipitation treatment.

  Moreover, it is preferable that the cellulose ester used by this invention is a thing with few bright spot foreign materials when it is made into a film. A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose ester film is arranged between them, light from the light source is applied from one side, and the cellulose ester film is applied from the other side. This is the point where the light from the light source appears to leak when observed. At this time, the polarizing plate used for the evaluation is desirably composed of a protective film having no bright spot foreign matter, and a polarizing plate using a glass plate for protecting the polarizer is preferably used. One of the causes of bright spot foreign matter is the unacetylated or low acetylated cellulose contained in the cellulose ester. Use a cellulose ester with less bright spot foreign matter (use a cellulose ester with a small dispersion degree of substitution). And filtering the melted cellulose ester, or removing the bright spot foreign matters through the filtration process in the same way once in the solution state in at least one of the process of synthesizing the cellulose ester and the process of obtaining the precipitate You can also. Since the molten cellulose ester has a high viscosity, the latter method is more efficient.

As the film thickness decreases, the number of bright spot foreign matter per unit area decreases, and as the cellulose ester content in the film decreases, the bright spot foreign matter tends to decrease. 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, and 30 pieces / cm ² or less. More preferably, it is more preferably 10 / cm ² or less, but most preferably none. Moreover, it is preferable that it is 200 pieces / cm < ² > or less also about a bright spot of 0.005-0.01 mm or less, it is more preferable that it is 100 pieces / cm < ² > or less, and it is 50 pieces / cm < ² > or less. More preferably, it is more preferably 30 pieces / cm ² or less, still more preferably 10 pieces / cm ² or less, and most preferably none.

  When removing bright spot foreign matter by melt filtration, filtering the cellulose ester composition to which a deterioration inhibitor, a plasticizer, etc. are added and mixed is more effective than filtering the melted cellulose ester alone. High efficiency is preferable. Of course, the cellulose ester may be dissolved in a solvent during the synthesis and reduced by filtration. What mixed the ultraviolet absorber and other additives suitably can be filtered. Filtration is preferably performed at a viscosity of a melt containing cellulose ester of 10,000 Pa · s or less, more preferably 5000 Pa · s or less, even more preferably 1000 Pa · s or less, and even more preferably 500 Pa · s or less. . As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluorine resins such as tetrafluoroethylene resin are preferably used, and ceramics, metals and the like are particularly preferably used. The absolute filtration accuracy is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less, and even more preferably 5 μm or less. These can be used in combination as appropriate. The filter medium can be either a surface type or a depth type, but the depth type is preferably used because it is relatively less clogged.

  In another embodiment, a cellulose ester obtained by dissolving the raw material cellulose ester at least once in a solvent and then drying the solvent may be used. In that case, a cellulose ester which has been dissolved in a solvent together with at least one of a deterioration inhibitor, a plasticizer, an ultraviolet absorber and a matting agent and then dried is used. As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time. You may cool to -20 degrees C or less in the process of dissolution, or you may heat to 80 degrees C or more. When such a cellulose ester is used, each additive in a molten state can be easily made uniform, and optical characteristics can be made uniform.

  The optical film of the present invention may be appropriately mixed with polymer components other than cellulose ester. The polymer component to be mixed is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more.

  Since the cellulose ester of the present invention is used for melt film formation, it is necessary for the cellulose ester itself to be stable from heat-melting to film formation. In relation to the mechanical properties, optical properties, and durability of the cellulose ester film after melt film formation as well as the stability of the film, it is related to the 1% mass reduction temperature Td (1.0) in the air of the cellulose ester before heating and melting. I found that there is sex. In addition, as long as the cellulose ester which satisfy | fills said Formula (1)-(4) based on this invention simultaneously is used, the said subject can be solved, but the one where Td (1.0) is high is a subject. In order to solve the problem, Td (1.0) is preferably 270 ° C. or higher, more preferably 280 ° C. or higher, and most preferably 290 ° C. or higher. In order to increase the Td (1.0) of the cellulose ester, in the synthesis of the cellulose ester, in the operation of filtering and washing the cellulose ester at the time of the final removal, sufficiently wash with water until the pH of the washing solution becomes neutral It can be improved by doing. By the way, although the detailed reason is not well understood, depending on the type of cellulose ester, if it is washed excessively, some mechanical properties such as easy breakage may be deteriorated. Regarding the cellulose ester that simultaneously satisfies the formulas (1) to (4), it has been found that the mechanical properties are not deteriorated due to washing. The 1% mass decrease temperature Td (1.0) under air can be measured with a commercially available differential thermogravimetric analysis (TG-DTA) apparatus. Generally, cellulose ester is a small amount but has a moisture content. Because it contains, care must be taken when measuring. Specifically, after holding the sample at 100 ° C. for a while and confirming that the mass loss due to the volatilization of water has disappeared, a method of measuring the mass loss accompanying the temperature rise from that point is taken. By the way, there is no upper limit to Td (1.0), and it is estimated that a higher value is preferable. However, in consideration of avoiding an increase in the burden of the cellulose ester washing step, a practical upper limit is 300 to It is about 310 ° C.

  The cellulose ester of the present invention can further improve the stability during heating by a combination with a deterioration preventing agent, but surprisingly, by combining with the deterioration preventing agent described below, the horse's back failure or convex shape It was found that there is no deformation failure of the original film such as failure, and a cellulose ester film excellent in any of flatness, suitability for saponification treatment, curling property, retardation variability, and durability can be obtained. .

<Deterioration preventive agent>
The deterioration preventing agent is a material that suppresses decomposition of a polymer by heat, oxygen, moisture, acid, or the like by a chemical action. Since the optical film of the present invention is molded particularly at a high temperature of 200 ° C. or higher, it is a system in which the polymer is easily decomposed and deteriorated, and it is preferable to contain a deterioration inhibitor in the film-forming material.

  It is represented by coloring and molecular weight reduction, including decomposition reactions that have not been elucidated, such as preventing oxidation of film-forming materials, capturing acid generated by decomposition, and suppressing or prohibiting decomposition reactions caused by radical species due to light or heat. Degradation inhibitors are used to suppress the generation of volatile components due to deterioration and material decomposition.

  Examples of the degradation inhibitor include, but are not limited to, an antioxidant, a hindered amine light stabilizer, an acid scavenger, and a metal deactivator. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. Among these, for the purpose of the present invention, it is preferable to include an antioxidant as a deterioration preventing agent in the film forming material.

  The deterioration preventing agent in the film-forming material used in the present invention can be selected from at least one or more. The amount to be added is 0.01 mass with respect to the mass of the cellulose ester according to the present invention. % To 10% by mass, more preferably 0.1% to 5.0% by mass, and still more preferably 0.2% to 2.0% by mass.

  It should be noted that if the addition amount of the deterioration inhibitor is larger than the range of the above addition amount, it is not preferable because it causes a decrease in transparency as an optical film from the viewpoint of compatibility with cellulose ester, and the film may become brittle. .

  The film-forming material can be stored by dividing the constituent material into one or a plurality of types of pellets for the purpose of avoiding material alteration and hygroscopicity. Pelletization may improve the mixing or compatibility of the melt during heating, or may ensure the optical uniformity of the resulting film.

  When the film-forming material is heat-melted, and when the heat-melted material is used in a post-process, or when used as a product under the consumer, the presence of the above-mentioned deterioration preventive agent It is excellent in terms of reducing the strength and deterioration of optical transparency due to deterioration and decomposition, or maintaining the strength inherent to the material.

  If the film-forming material is significantly deteriorated by heating, coloring may occur and it may not be used as an optical film. In addition, when used as an optical compensation film for a liquid crystal display device, a retardation imparting step (stretching step) is performed after the casting step. If the film-forming material is significantly deteriorated by heating, the formed film May become brittle and may be easily broken in the stretching process, or the retardation value of the target optical compensation film may not be expressed. Furthermore, when used as a polarizing plate protective film for a liquid crystal display device, the deterioration of the film-forming material is not preferable because it may interfere with the bonding with the polarizer.

  Therefore, the presence of the above-mentioned deterioration preventing agent suppresses the generation of a colored material in the visible light region at the time of heating and melting, or a volatile component generated by decomposition of the material constituting the film at the time of heating and melting. It is also excellent in that deterioration unfavorable as an optical film such as a decrease in transmittance and haze value caused by the above can be suppressed or eliminated.

  In the present invention, the display image of the liquid crystal display device is affected when the haze value exceeds 1% when the optical film of the present invention is used. Therefore, the haze value is preferably less than 1%, more preferably less than 0.5%. is there. As an index of colorability, yellowness (yellow index, YI) can be used, preferably 3.0 or less, more preferably 1.0 or less. Yellowness can be measured based on JIS-K7103.

  In the above-described film forming material storage or film forming process, deterioration reactions due to oxygen or moisture in the air may occur simultaneously. In this case, in addition to the stabilizing action of the deterioration preventing agent, reducing the humidity and oxygen concentration in the air can be preferably used in combination for realizing the present invention. This includes the use of nitrogen or argon as an inert gas as a known technique, a degassing operation under reduced pressure to vacuum, and an operation under a sealed environment, and at least one of these three methods includes the above stabilizer. Can be used in combination with the method of By reducing the probability that the film-forming material comes into contact with oxygen in the air, it is preferable because deterioration of the material can be suppressed.

  In addition, since the optical film of the present invention is also used as a polarizing plate protective film, from the viewpoint of improving the storage stability with time with respect to the polarizing plate of the present invention and the polarizer constituting the polarizing plate, The presence of the above-mentioned deterioration preventing agent plays an important role.

  In the liquid crystal display device using the polarizing plate of the present invention, when the above-mentioned deterioration preventing agent is present in the optical film of the present invention, the storage stability of the optical film over time can be improved from the viewpoint of suppressing the above-mentioned deterioration and deterioration, and the liquid crystal Also in improving the display quality of the display device, the optical compensation design is excellent in that the function can be expressed over a long period of time.

"Antioxidant"
Since cellulose ester is decomposed not only by heat but also by oxygen at a high temperature, the optical film of the present invention preferably contains an antioxidant as a deterioration preventing agent.

  The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses deterioration of the film-forming material due to oxygen, and among them, phenolic compounds, phosphorus compounds, sulfur compounds, alkyl radical scavengers. , Peroxide decomposers, oxygen scavengers and the like. Among these, a phenol compound, a phosphorus compound, and an alkyl radical scavenger are preferable, but it is more preferable to use a combination of the phenol compound and the phosphorus compound, and the phenol compound, the phosphorus compound, and the alkyl radical scavenger. It is most preferable to use a combination of the three. By blending these compounds, it is possible to prevent coloring and strength reduction of the molded product due to heat during heat molding or thermal oxidative degradation without lowering transparency and heat resistance. Each of these compounds can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention, but the mass of the cellulose ester according to the present invention is On the other hand, 0.01 mass% or more and 10 mass% or less are preferable, More preferably, it is 0.1 mass% or more and 5.0 mass% or less, More preferably, it is 0.2 mass% or more and 2.0 mass% or less. is there.

(Phenolic compounds)
Phenol compounds are known compounds, and include alkyl group-substituted phenols such as para-t-butylphenol and para- (1,1,3,3-tetramethylbutyl) phenol, for example, U.S. Pat. No. 4,839, Examples include 2,6-dialkylphenol derivative compounds, so-called hindered phenol compounds, described in columns 12 to 14 of No. 405 specification. Among these, hindered phenol compounds are preferable.
Specific examples of the hindered phenol phenol compound include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- (3,5-di-t- Butyl-4-hydroxyphenyl) -acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl β (3,5-di-t- Butyl-4-hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobuty Rate, octadecyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (N-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-phenyl acetate, 2- ( n-octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- ( 2-hydroxyethylthio) ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di -T-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide N, N-bis- [ Ethylene 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino N, N-bis- [ethylene 3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate], 2- (2-stearoyloxyethylthio) ethyl 3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl 7- (3-methyl-5- t-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di-t-butyl- -Hydroxyphenyl) propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentylglycol bis- [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate-2,3-bis- ( 3,5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis- [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 3,9 -Bis- {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1 Dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,1,1-trimethylolethane-tris- [3- (3,5-di-t-butyl-4- Hydroxyphenyl) propionate], sorbitol hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-tbutyl-4-hydroxy Phenyl) propionate, 2-stearoyloxyethyl 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ', 5'-di-t -Butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis (3,5-di-t-butyl-4-hydroxyhydride) Cinnamate) are included. The above type of phenolic compounds are commercially available from Ciba Specialty Chemicals under the trade names “IRGANOX1076” and “IRGANOX1010”, for example.

(Phosphorus compounds)
Examples of phosphorus compounds useful in the present invention include phosphite compounds and phosphonite compounds. Specific examples of the phosphite compound include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di -T-butylphenyl) phosphite, tris (2,4-di-t-butyl-5-methylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 6- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10- Mono such as tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphine, tridecyl phosphite Sphite compounds; 4,4'-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis (phenyl-di-alkyl (C12- And diphosphite compounds such as C15) phosphite). Examples of the phosphite compounds of the above-mentioned types include “Sumizer GP” from Sumitomo Chemical Co., Ltd., ADK STAB PEP-24G from ADEKA Corporation, “ADK STAB PEP-36”, “ADK STAB 3010”, “ADK STAB”. It is commercially available under the trade names “HP-10” and “ADK STAB 2112”.

  Specific examples of the phosphonite compound include dimethyl-phenylphosphonite, di-t-butyl-phenylphosphonite, diphenyl-phenylphosphonite, di- (4-pentyl-phenyl) -phenylphosphonite, di- (2- t-butyl-phenyl) -phenylphosphonite, di- (2-methyl-3-pentyl-phenyl) -phenylphosphonite, di- (2-methyl-4-octyl-phenyl) -phenylphosphonite, di- ( 3-butyl-4-methyl-phenyl) -phenylphosphonite, di- (3-hexyl-4-ethyl-phenyl) -phenylphosphonite, di- (2,4,6-trimethylphenyl) -phenylphosphonite, Di- (2,3-dimethyl-4-ethyl-phenyl) -phenylphosphonite, di- (2,6-diethi -3-butylphenyl) -phenylphosphonite, di- (2,3-dipropyl-5-butylphenyl) -phenylphosphonite, di- (2,4,6-tri-t-butylphenyl) -phenylphosphonite Bis (2,4-di-t-butyl-5-methylphenyl) biphenyl-4-yl-phosphonite, bis (2,4-di-t-butyl-5-methylphenyl) -4 ′-(bis ( 2,4-di-tert-butyl-5-methylphenoxy) phosphino) biphenyl-4-yl-phosphonite, tetrakis (2,4-di-tert-butyl-phenyl) -4,4'-biphenylenediphosphonite, Tetrakis (2,5-di-t-butyl-phenyl) -4,4'-biphenylenediphosphonite, tetrakis (3,5-di-t-butyl-phenyl) -4,4'-biphenyle Diphosphonite, tetrakis (2,3,4-trimethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-dimethyl-5-ethyl-phenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-Dimethyl-4-propylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-dimethyl-5-t-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-Dimethyl-4-t-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-diethyl-5-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-diethyl-4-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis ( , 4,5-triethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-diethyl-4-propylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-diethyl) -6-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-diethyl-5-t-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-diethyl) -6-tert-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-dipropyl-5-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-dipropyl) -4-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-dipropyl-5-ethyl) Phenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-dipropyl-6-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-dipropyl-5-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3-dibutyl-4-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-dibutyl-3-methylphenyl) -4 , 4'-biphenylenediphosphonite, tetrakis (2,6-dibutyl-4-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-di-t-butyl-3-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-di-t-butyl-5-methylphenyl) -4,4 ' Biphenylene diphosphonite, tetrakis (2,4-di-t-butyl-6-methylphenyl) -4,4'-biphenylene diphosphonite, tetrakis (2,5-di-t-butyl-3-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-di-t-butyl-4-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-di-t-butyl) -6-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-di-t-butyl-3-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6 -Di-t-butyl-4-methylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-di-t-butyl-5-methylphenyl) -4 4'-biphenylenediphosphonite, tetrakis (2,3-dibutyl-4-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-dibutyl-3-ethylphenyl) -4,4 ' -Biphenylenediphosphonite, tetrakis (2,5-dibutyl-4-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-di-t-butyl-3-ethylphenyl) -4, 4'-biphenylenediphosphonite, tetrakis (2,4-di-t-butyl-5-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-di-t-butyl-6- Ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-di-t-butyl-3-ethylphenyl) -4,4'-biphe Nylene diphosphonite, tetrakis (2,5-di-t-butyl-4-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,5-di-t-butyl-6-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-di-t-butyl-3-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-di-t-butyl) -4-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,6-di-t-butyl-5-ethylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,3 , 4-tributylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4,6-tri-t-butylphenyl) -4,4'-biphenylenediphos Night and the like. The phosphorus compound of the above type is commercially available from Ciba Specialty Chemicals, Inc. under the trade name “IRGAFOS P-EPQ” and from Sakai Chemical Industry Co., Ltd., as “GSY-P101”.

  As the phosphorus compound useful in the present invention, a phosphonite compound is preferable, and among them, 4,4'-biphenyl such as tetrakis (2,4-di-t-butyl-phenyl) -4,4'-biphenylenediphosphonite. A range phosphonite compound is preferred, and tetrakis (2,4-di-t-butyl-5-methylphenyl) -4,4'-biphenylene diphosphonite is particularly preferred.

(Alkyl radical scavenger)
In the present invention, the “alkyl radical scavenger” means a compound having a group that can react rapidly with an alkyl radical and giving a stable product that does not undergo subsequent reaction after reaction with the alkyl radical.

  Preferred alkyl radical scavengers in the present invention include the compound represented by the general formula (1) and the compound represented by the general formula (2).

  Hereinafter, although the compound represented with the said General formula (1) used for this invention is demonstrated to a specific example, this invention is not limited to these.

In the general formula (1), R ₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, particularly preferably a hydrogen atom or a methyl group. is there.

R ₂ and R ₃ each independently represents an alkyl group having 1 to 8 carbon atoms, and may be linear or have a branched structure or a ring structure. R ₂ and R ₃ are preferably a structure represented by “* —C (CH ₃ ) ₂ —R ′” containing a quaternary carbon (* represents a connecting site to an aromatic ring, and R ′ has 1 carbon atom. Represents an alkyl group of ˜5). R ₂ is more preferably a tert-butyl group or a tert-amyl group. R ₃ is more preferably a tert-butyl group, a tert-amyl group or a tert-octyl group.

  The compound represented by the general formula (1) is commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer GM” and “Sumilizer GS”.

  Specific examples of the compound represented by the general formula (1) are illustrated below, but the present invention is not limited thereto.

  Next, although the compound represented by the said General formula (2) used for this invention is demonstrated to a specific example, this invention is not limited to these.

In General formula (2), R < ₁₂ > -R < ₁₅ > represents a hydrogen atom or a substituent each independently. R ₁₂ and R ₁₃ , R ₁₃ and R ₁₄ , or R ₁₄ and R ₁₅ may be bonded to each other to form a ring. R ₁₆ represents a hydrogen atom or a substituent, n represents an integer of 1 to 4, and when n is 1, R ₁₁ represents a substituent, and when n is an integer of 2 to 4, R ₁₁ is Represents a divalent to tetravalent linking group.
When R _{12 to} R ₁₅ represent a substituent, the substituent is not particularly limited. For example, an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, a pentyl group, Hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), acylamino group (eg, acetylamino) Group, benzoylamino group, etc.), alkylthio group (eg, methylthio group, ethylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkenyl group (eg, vinyl group, 2-propenyl group, 3-butenyl) Group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl Group, 4-hexenyl group, cyclohexenyl group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkynyl group (eg, propargyl group, etc.), heterocyclic group (eg, pyridyl group, etc.) , Thiazolyl group, oxazolyl group, imidazolyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, etc.), arylsulfonyl group (for example, phenylsulfonyl group, naphthylsulfonyl group, etc.), alkylsulfinyl group (for example, Methylsulfinyl group etc.), arylsulfinyl group (eg phenylsulfinyl group etc.), phosphono group, acyl group (eg acetyl group, pivaloyl group, benzoyl group etc.), carbamoyl group (eg aminocarbonyl group, methylaminocarbonyl group) , Dimethylamino Sulfonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, Hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), sulfonamide group (for example, methanesulfonamide group, benzene) Sulfonamide group etc.), cyano group, alkoxy group (eg methoxy group, ethoxy group, propoxy group etc.), aryloxy group (eg phenoxy group, Naphthyloxy group, etc.), heterocyclic oxy group, siloxy group, acyloxy group (eg, acetyloxy group, benzoyloxy group, etc.), sulfonic acid group, sulfonic acid salt, aminocarbonyloxy group, amino group (eg, amino group) , Ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (for example, phenylamino group, chlorophenylamino group, toluidino group, anisidino group, naphthylamino) Group, 2-pyridylamino group, etc.), imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2 -Pyridylami Ureido group etc.), alkoxycarbonylamino group (eg methoxycarbonylamino group, phenoxycarbonylamino group etc.), alkoxycarbonyl group (eg methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl etc.), aryloxycarbonyl group (eg Phenoxycarbonyl group, etc.), heterocyclic thio group, thioureido group, carboxyl group, carboxylic acid salt, hydroxyl group, mercapto group, nitro group and the like. These substituents may be further substituted with the same substituent.

In the general formula (2), R _{12 to} R ₁₅ are preferably a hydrogen atom or an alkyl group.

In the general formula (2), R ₁₆ represents a hydrogen atom or a substituent, and examples of the substituent represented by R ₁₆ include the same groups as the substituents represented by R _{12 to} R ₁₅ . In particular, R ₁₆ is preferably a hydrogen atom.

In the general formula (2), n represents an integer of 1 to 4, but when n is 1, R ₁₁ represents a substituent, and the substituent is the same as the substituent represented by R _{12 to} R _15. Can be mentioned. When n is an integer of 2 to 4, R ₁₁ correspondingly represents a divalent to tetravalent linking group.

When R ₁₁ represents a divalent to tetravalent linking group, examples of the divalent linking group include a divalent alkylene group that may have a substituent, a divalent arylene group that may have a substituent, An oxygen atom, a nitrogen atom, a sulfur atom, or a combination of these linking groups can be exemplified.

  Examples of the trivalent linking group include a trivalent alkylene group which may have a substituent, a trivalent arylene group which may have a substituent, a nitrogen atom, or a combination of these linking groups. Examples of the tetravalent linking group include a tetravalent alkylene group which may have a substituent, a tetravalent arylene group which may have a substituent, or a combination of these linking groups. Can do.

In the general formula (2), n is preferably 1, and R ₁₁ at that time is preferably a substituted or unsubstituted phenyl group. The substituent is an alkyl group having 1 to 18 carbon atoms, or 1 to 18 carbon atoms. Alkoxy groups having 1 to 8 carbon atoms and alkoxy groups having 1 to 8 carbon atoms are more preferable.

  Specific examples of the compound represented by the general formula (2) in the present invention are shown below, but the present invention is not limited thereto.

(Other antioxidants)
Specific examples of the other antioxidants include dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3. -Thiodipropionate, pentaerythritol-tetrakis (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane And sulfur compounds. The above-mentioned types of sulfur compounds are commercially available, for example, from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D”. Furthermore, 3,4-dihydro-2H-1-benzopyran compounds, 3,3′-spirodichroman compounds, 1,1-spiroindane compounds, morpholine, thiomorpholine, thiomorpholine described in JP-B-08-27508 Examples include oxides, thiomorpholine dioxide, compounds having a piperazine skeleton in the partial structure, oxygen scavengers such as dialkoxybenzene compounds described in JP-A-3-174150, and the like. These antioxidant partial structures may be part of the polymer or regularly pendant to the polymer.

《Hindered amine light stabilizer》
In the present invention, a hindered amine light stabilizer (HALS) is used as an anti-deterioration agent during heat melting of a film-forming material, and as an anti-deterioration agent against external light exposed as a polarizer protective film after production or light from a backlight of a liquid crystal display. Compounds, which are known compounds, such as columns 5-11 of US Pat. No. 4,619,956 and columns 3-5 of US Pat. No. 4,839,405. 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds.

  Specific examples of the hindered amine light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis ( 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-benzyloxy-2, 2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6) -Pentamethyl-4-piperidyl) 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acryloyl-2,2,6,6- Tramethyl-4-piperidyl) 2,2-bis (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1,2,2,6,6-pentamethyl-4- Piperidyl) decanedioate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -1- [ 2- (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy) ethyl] -2,2,6,6-tetramethylpiperidine, 2-methyl-2- (2,2, 6,6-tetramethyl-4-piperidyl) amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, and the like.

  Further, it may be a polymer type compound. As specific examples, N, N ′, N ″, N ″ ′-tetrakis- [4,6-bis- [butyl- (N-methyl-2,2,6, 6-tetramethylpiperidin-4-yl) amino] -triazin-2-yl] -4,7-diazadecane-1,10-diamine, dibutylamine and 1,3,5-triazine-N, N′-bis ( 2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate, di Polycondensate of butylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1,1,3,3 -Tetramethylbutyl) amino-1,3,5-tri Gin-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], Weight of 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) and morpholine-2,4,6-trichloro-1,3,5-triazine Condensate, poly [(6-morpholino-s-triazine-2,4-diyl) [(2,2,6,6, -tetramethyl-4-piperidyl) imino] -hexamethylene [(2,2,6 , 6-tetramethyl-4-piperidyl) imino]], etc., high molecular weight HALS in which a plurality of piperidine rings are bonded via a triazine skeleton; dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl- 1-piperidine eta 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1- (Dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane and the like, and the like include compounds in which a piperidine ring is bonded via an ester bond. It is not something.

  Among these, polycondensates of dibutylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1, 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2 , 2,6,6-tetramethyl-4-piperidyl) imino}], a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, etc. Those having a molecular weight (Mn) of 2,000 to 5,000 are preferred.

  Hindered amine compounds of the above type are commercially available, for example, from Ciba Specialty Chemicals under the trade names “TINUVIN 144” and “TINUVIN 770” and from ADEKA Corporation “ADK STAB LA-52”.

  In the present invention, the hindered amine light stabilizer is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, based on the mass of the cellulose ester according to the present invention. Furthermore, it is preferable to add 0.5-2 mass%. Two or more of these may be used in combination.

<Acid scavenger>
The cellulose ester is preferably decomposed by an acid in a high temperature environment in which melt film formation is performed. Therefore, the optical film of the present invention preferably contains an acid scavenger as a deterioration preventing agent. Any acid scavenger useful in the present invention can be used without limitation as long as it is a compound that reacts with an acid to inactivate the acid, and is described in U.S. Pat. No. 4,137,201. A compound having an epoxy group is preferred. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8 to 40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, etc., metal epoxy compounds (such as those conventionally used in and with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (for example, Butyl epoxy stearate) And epoxidized vegetable oils and other unsaturated natural oils (sometimes epoxies) that may be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides and the like (eg, epoxidized soybean oil, epoxidized linseed oil, etc.) Natural fatty glycerides or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms). Moreover, EPON 815C and other epoxidized ether oligomer condensation products can also be preferably used as commercially available epoxy group-containing epoxide resin compounds.

  Furthermore, examples of acid scavengers that can be used other than the above include oxetane compounds, oxazoline compounds, organic earth salts of alkaline earth metals and acetylacetonate complexes, and paragraphs 68 to 105 of JP-A-5-194788. Is included.

  In the present invention, the acid scavenger is preferably added in an amount of 0.1 to 10% by weight, more preferably 0.2 to 5% by weight, based on the weight of the cellulose ester according to the present invention. It is preferable to add 0.5 to 2% by mass. Two or more of these may be used in combination.

  In addition, although an acid scavenger may be called an acid scavenger, an acid capture agent, an acid catcher, etc., in this invention, it can use without a difference by these names.

《Metal deactivator》
A metal deactivator means a metal ion deactivating compound that acts as an initiator or a catalyst in an oxidation reaction, and examples thereof include hydrazide compounds, oxalic acid diamide compounds, triazole compounds, and the like. N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, 2-hydroxyethyl oxalic acid diamide, 2-hydroxy-N- (1H-1,2,4- And triazol-3-yl) benzamide, N- (5-yert-butyl-2-ethoxyphenyl) -N ′-(2-ethylphenyl) oxalic acid amide, and the like.

  In this invention, it is preferable to add a metal deactivator 0.0002-2 mass% with respect to the mass of the cellulose ester which concerns on this invention, Furthermore, it is preferable to add 0.0005-2 mass%, Furthermore, it is preferable to add 0.001-1 mass%. Two or more of these may be used in combination.

《Plasticizer》
In forming the optical film by melt casting according to the present invention, it is necessary to add at least one plasticizer to the film forming material.

  Generally, a plasticizer is an additive having an effect of improving brittleness or imparting flexibility by adding it to a polymer. In the present invention, a plasticizer is melted. It is used as an additive that lowers the temperature or as an additive that lowers the viscosity of the film-forming material at the same temperature. Since it is possible to suppress the degradation of the cellulose ester during the melting process by lowering the melting temperature or lowering the melt viscosity, in the present invention, any material having such an effect can be used as a plasticizer without limitation. Can do. Such a melting point lowering effect / viscosity reduction lowering can be more easily obtained when a plasticizer to be added has a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester.

  In addition, the addition of a plasticizer may improve the mechanical properties of the cellulose ester film, improve the tear strength, impart water resistance resistance, and reduce moisture permeability. It is more preferable to use as a plasticizer.

  In addition, the plasticizer also has an effect of suppressing degradation in the hot melt process of the cellulose ester by adding as described above, but the effect is due to a physical effect and not due to a chemical effect. In the present invention, it is not classified as a deterioration inhibitor.

  Examples of plasticizers that satisfy the above conditions and are used in the present invention include phosphate ester plasticizers, polyhydric alcohol ester plasticizers (ethylene glycol ester plasticizers, glycerin ester plasticizers, diglycerin). Ester plasticizers), polycarboxylic acid ester plasticizers, carbohydrate ester plasticizers, polymer plasticizers, and the like. Of these, polyhydric alcohol ester plasticizers and polycarboxylic acid ester plasticizers are preferred, and polyhydric alcohol ester plasticizers are more preferred. Further, the plasticizer may be a liquid or a solid, and is preferably colorless due to restrictions on the composition. The addition amount may be as long as it does not adversely affect the optical properties and mechanical properties, and the blending amount is appropriately selected within a range not impairing the object of the present invention, and preferably 1 to 25 with respect to the mass of the cellulose ester according to the present invention. It is a cellulose-ester film characterized by containing the mass%. When the content is less than 1% by mass, the effect of improving the flatness is not recognized, and when the content is more than 25% by mass, bleeding out easily occurs and the temporal stability of the film decreases, which is not preferable. More preferred is a cellulose ester film containing 3 to 20% by mass of a plasticizer, and still more preferred is a cellulose ester film containing 5 to 15% by mass.

  Hereinafter, although the plasticizer used for this invention is demonstrated to a specific example, this invention is not limited to these.

  In the present invention, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol are preferred because of their high affinity with the cellulose ester. An ester plasticizer composed of an alcohol and a monovalent carboxylic acid is particularly preferable because the affinity with the cellulose ester is further increased.

  The polyhydric alcohol ester plasticizer is a compound obtained by condensing a compound having a plurality of hydroxyl groups in one molecule and a monovalent organic acid as a polyhydric alcohol ester plasticizer. An ester plasticizer refers to a compound obtained by condensing a compound having a plurality of carboxylic acid groups in one molecule and a plurality of monovalent alcohols or phenols as a polyvalent carboxylic ester plasticizer.

  Examples of the polyhydric alcohol that is a raw material of the ester plasticizer preferably used in the present invention include the following, but the present invention is not limited thereto.

  Adonitol, arabitol, ethylene glycol, glycerin, diglycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, ditrimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, xyl Mention may be made of the toll and the like. In particular, ethylene glycol, glycerin, and trimethylolpropane are preferable.

  Examples of preferred organic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, pivalic acid, acrylic acid, methacrylic acid, cyclohexanecarboxylic acid, benzoic acid, anisic acid, 3,4,5-trimethoxybenzoic acid, toluyl Acid, tert-butylbenzoic acid, naphthoic acid, picolinic acid, etc. are mentioned, but polyhydric alcohol ester is formed by unsaturated carboxylic acid, for example, aromatic carboxylic acid, which is highly effective in reducing moisture permeability of cellulose ester It is preferable.

  One type of organic acid may be used for the polyhydric alcohol ester, or a mixture of two or more types may be used. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Specific examples of ethylene glycol ester plasticizers that are one of the polyhydric alcohol esters include ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, and ethylene glycol dicyclopropyl. Examples thereof include ethylene glycol cycloalkyl ester plasticizers such as carboxylate and ethylene glycol dicyclohexylcarboxylate, and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mix of alkylate group, cycloalkylate group and arylate group, and these substituents may be covalently bonded. Further, the ethylene glycol part may be substituted, and the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

  Specific examples of the glycerin ester plasticizer that is one of the polyhydric alcohol esters include glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, and glycerol tricyclopropylcarboxylate. Glycerol glycerol esters such as glycerol tricyclohexyl carboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol 4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol Tetralaurate, diglycerin alkyl ester, diglycerin tetracyclobutylcarboxylate, diglycerin tet Diglycerol cycloalkyl esters such as cyclopentyl carboxylate diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

  Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A No. 2003-12823.

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

  Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferred. Specifically, the above-mentioned ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, Exemplified compound 16 described in paragraph 31 of JP2003-12823A can be mentioned.

  Specific examples of the dicarboxylic acid ester plasticizer that is one of the polyvalent carboxylic acid esters include alkyl dicarboxylic acid alkyl ester plasticizers such as didodecyl malonate, dioctyl adipate, and dibutyl sebacate. Alkyl dicarboxylic acid cycloalkyl ester type plasticizers such as cyclopentyl succinate and dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester type plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexane Cycloalkyl dicarboxylic acid alkyl ester plasticizers such as dicarboxylate and didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicis Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as ropropyl-1,2-cyclohexyldicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate, etc. Cycloalkyldicarboxylic acid aryl ester plasticizer, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and other aryl dicarboxylic acid alkyl ester plasticizers, dicyclopropyl phthalate, dicyclohexyl phthalate, etc. Aryl dicarboxylic acid cycloalkyl ester plasticizers, and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di-4-methylphenyl phthalate Butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, etc. glycolic acid ester based plasticizers, acetyl trimethyl citrate, acetyl triethyl citrate, a plasticizer and the like citric acid, such as acetyl tributyl citrate. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and it may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Examples of other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizers, alkylpolycarboxylic acid cycloalkyl ester plasticizers such as tricyclohexyltricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy- Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2, 3,4-cyclobutanetetracarboxylate, tetrabu Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as ru-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2, Cycloalkyl polycarboxylic acid aryl ester plasticizers such as 3,4,5,6-cyclohexylhexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4 , 5-tetracarboxylate and other aryl polyvalent Rubinoic acid alkyl ester plasticizers, tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate and other aryl polyvalent carboxylic acid cycloalkyl esters Plasticizers of aryl polyvalent carboxylic acid aryl esters such as plasticizers triphenylbenzene-1,3,5-tetracarboxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Agents. These alkoxy groups and cycloalkoxy groups may be the same or different, and may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant into the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, alkyl dicarboxylic acid alkyl esters are preferable, and specific examples include the dioctyl adipate.

  Examples of other plasticizers used in the present invention include phosphate ester plasticizers, carbohydrate ester plasticizers, and polymer plasticizers.

  Specific examples of the phosphoric acid ester plasticizer include phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclopentyl phosphate and cyclohexyl phosphate, triphenyl phosphate, and trichlorate. Examples thereof include phosphoric acid aryl esters such as zil phosphate, cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl) And phosphate esters such as arylene bis (diaryl phosphate) such as arylene bis (dialkyl phosphate), phenylene bis (diphenyl phosphate), naphthylene bis (ditoluyl phosphate) such as biphenylene bis (dioctyl phosphate). These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Furthermore, the partial structure of phosphate ester may be part of the polymer, or may be regularly pendant, and also introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Next, the carbohydrate ester plasticizer will be described. The carbohydrate means a monosaccharide, disaccharide or trisaccharide in which the saccharide is present in the form of pyranose or furanose (6-membered ring or 5-membered ring). Non-limiting examples of carbohydrates include glucose, saccharose, lactose, cellobiose, mannose, xylose, ribose, galactose, arabinose, fructose, sorbose, cellotriose and raffinose. The carbohydrate ester refers to an ester compound formed by dehydration condensation of a carbohydrate hydroxyl group and a carboxylic acid, and specifically means an aliphatic carboxylic acid ester or an aromatic carboxylic acid ester of a carbohydrate. Examples of the aliphatic carboxylic acid include acetic acid and propionic acid, and examples of the aromatic carboxylic acid include benzoic acid, toluic acid, and anisic acid. Carbohydrates have a number of hydroxyl groups depending on the type, but even if a part of the hydroxyl group reacts with the carboxylic acid to form an ester compound, the whole hydroxyl group reacts with the carboxylic acid to form an ester compound. Also good. In the present invention, it is preferable that all of the hydroxyl groups react with the carboxylic acid to form an ester compound.

  Specific examples of the carbohydrate ester plasticizer include glucose pentaacetate, glucose pentapropionate, glucose pentabylate, saccharose octaacetate, saccharose octabenzoate and the like. Among these, saccharose octaacetate, saccharose Octabenzoate is more preferred, and sucrose octabenzoate is particularly preferred. The above-mentioned type of carbohydrate ester plasticizer is commercially available from Daiichi Kogyo Seiyaku Co., Ltd. under the trade names “Monopet SB” and “Monopet SOA”.

  Specific examples of the polymer plasticizer include aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, polyethyl acrylate, polymethyl methacrylate, methyl methacrylate and 2-hydroxyethyl methacrylate. Polymers, acrylic polymers such as copolymers of methyl methacrylate, methyl acrylate and methacrylate-2-hydroxyethyl, vinyl polymers such as polyvinyl isobutyl ether and poly N-vinyl pyrrolidone, polystyrene, poly 4-hydroxy Examples thereof include styrene polymers such as styrene, polyesters such as polybutylene succinate, polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes and polyureas. The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000. If it is 1000 or less, a problem arises in volatility, and if it exceeds 500000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester film are adversely affected. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination.

  The cellulose ester film according to the present invention may contain 1 to 25% by mass of an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol. Although preferable, it may be used in combination with other plasticizers.

  In the cellulose ester film according to the present invention, an ester plasticizer composed of a polyhydric alcohol and a monovalent carboxylic acid is more preferred, but an ester plasticizer composed of a trivalent or higher alcohol and a monovalent carboxylic acid is suitable for the cellulose ester. Because it is highly compatible and can be added at a high addition rate, it does not cause bleed-out even when other plasticizers and additives are used in combination. Since an additive can be used together easily, it is the most preferable.

<Ultraviolet absorber>
In the present invention, it is preferable that the film-forming material further contains an ultraviolet absorber in terms of improving durability. The ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Those are preferred. Examples of the ultraviolet absorber used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. However, benzophenone compounds, less colored benzotriazole compounds, and triazine compounds are preferable. Further, ultraviolet absorbers described in JP-A Nos. 10-182621 and 8-337574, and polymer ultraviolet absorbers described in JP-A Nos. 6-148430 and 2003-113317 may be used.

  Specific examples of the benzotriazole-based compound include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzo Triazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1 , 1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'- ert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5 '-(2-octyloxycarbonylethyl) -phenyl) -5-chloro Benzotriazole, 2- (2′-hydroxy-3 ′-(1-methyl-1-phenylethyl) -5 ′-(1,1,3,3, -tetramethylbutyl) -phenyl) benzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzo Triazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-) Benzotriazole-2-yl) can be mentioned mixtures of phenyl] propionate, but not limited thereto.

  As commercial products, TINUVIN 326, TINUVIN 109, TINUVIN 171, TINUVIN 900, TINUVIN 928, TINUVIN 928, TINUVIN 360 (all of which are Ciba Specialty Chemicals) Product), LA31 (manufactured by ADEKA), Sumisorb 250 (manufactured by Sumitomo Chemical), and RUVA-100 (manufactured by Otsuka Chemical).

Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but are not limited thereto.
In the present invention, the ultraviolet absorber is preferably a benzotriazole-based compound.

  In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, based on the mass of the cellulose ester according to the present invention. It is preferable to add 0.5-3 mass%. Two or more of these may be used in combination.

  The benzotriazole structure or triazine structure may be part of the polymer, or may be regularly pendant to the polymer, and part of the molecular structure of other additives such as plasticizers, antioxidants, and acid scavengers. May be introduced.

  Although it does not specifically limit as a conventionally well-known ultraviolet absorptive polymer, For example, the polymer which homopolymerized RUVA-93 (made by Otsuka Chemical), the polymer which copolymerized RUVA-93, and another monomer, etc. are mentioned. . Specific examples include PUVA-30M obtained by copolymerization of RUVA-93 and methyl methacrylate at a ratio (mass ratio) of 3: 7, and PUVA-50M obtained by copolymerization at a ratio of 5: 5 (mass ratio). It is done. Furthermore, the polymer etc. which are described in Unexamined-Japanese-Patent No. 2003-113317 are mentioned.

《Other additives》
In the present invention, the cellulose ester can contain various additives in addition to the deterioration inhibitor, the plasticizer and the ultraviolet absorber. For example, matting agents, fillers, inorganic compounds such as silica and silicates, dyes, pigments, phosphors, dichroic dyes, retardation control agents, refractive index regulators, gas permeation inhibitors, antibacterial agents, biodegradable Examples include an imparting agent. Moreover, the additive which is not classified into this can be used if it has the said function.

  Then, as a method of incorporating these additives into the cellulose ester, each material is mixed in a solid or liquid state, heated and melted and kneaded to form a uniform melt, and then cast to form an optical film. Even in this method, after dissolving all the materials in advance using a solvent or the like to obtain a uniform solution, the solvent is removed to form a mixture of the additive and the cellulose ester, and this is heated and melted. It may be cast to form an optical film.

(Matting agent)
In the film according to the present invention, a matting agent can be added to impart slipperiness, optical and mechanical functions. Examples of the matting agent include inorganic compound fine particles and organic compound fine particles.

  The shape of the matting agent is preferably a spherical shape, a rod shape, a needle shape, a layer shape, a flat shape or the like. Examples of the matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples thereof include inorganic fine particles such as oxides, phosphates, silicates, and carbonates, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. These fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.

  The surface treatment is preferably performed with halosilanes, alkoxysilanes, silazane, siloxane, or the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average primary particle size of the fine particles is in the range of 0.01 to 1.0 μm. The average particle size of the primary particles of preferable fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used for generating irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film.

  As the fine particles of silicon dioxide, Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, NAX50, etc. manufactured by Nippon Aerosil Co., Ltd. P10, KE-P30, KE-P100, KE-P150 and the like can be mentioned, and Aerosil 200V, R972V, NAX50, KE-P30 and KE-P100 are preferable. Two or more kinds of these fine particles may be used in combination.

  When using 2 or more types together, it can mix and use in arbitrary ratios. Fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

  These matting agents are preferably added by kneading. Further, as another form, after mixing and dispersing a matting agent and cellulose ester and / or a plasticizer and / or an antioxidant and / or an ultraviolet absorber previously dispersed in a solvent, a solid substance obtained by volatilizing or precipitating the solvent is obtained. Obtaining and using this in the manufacturing process of the cellulose ester melt is preferable from the viewpoint that the matting agent can be uniformly dispersed in the cellulose ester.

  The matting agent can also be added to improve the mechanical, electrical and optical properties of the film.

  In addition, although the slipperiness of the film obtained improves, so that these microparticles | fine-particles are added, since a haze raises, so that it adds, content is preferably 0.001-5 mass%, More preferably, it is 0.00. It is 005-1 mass%, More preferably, it is 0.01-0.5 mass%.

  As the film according to the present invention, if the haze value exceeds 1.0%, the optical material is affected. Therefore, the haze value is preferably less than 1.0%, more preferably less than 0.5%. . The haze value can be measured based on JIS-K7136.

  In the above-described film forming material storage or film forming process, deterioration reactions due to oxygen in the air may occur simultaneously. In this case, the effect of reducing the oxygen concentration in the air can be used together with the stabilizing action of the additive in realizing the present invention. This includes the use of nitrogen or argon as an inert gas as a known technique, degassing operation under reduced pressure to vacuum, and operation under a sealed environment, and at least one of these three methods includes the above additives. Can be used in combination with the method of By reducing the probability that the film-forming material comes into contact with oxygen in the air, deterioration of the material can be suppressed, which is preferable for the purpose of the present invention.

<Optical film>
Next, the details of the optical film of the present invention will be described.

  In this invention, an optical film is a functional film used for various display apparatuses, such as a liquid crystal display, a plasma display, and an organic electroluminescent display. Specifically, it is a polarizing plate protective film for liquid crystal display apparatuses, retardation film, antireflection Films, brightness enhancement films, hard coat films, antiglare films, antistatic films, optical compensation films such as viewing angle expansion, and the like are included.

  In the optical film according to the present invention, in addition to the cellulose ester according to the present invention, a cellulose ester resin, a cellulose ether resin, a vinyl resin (including polyvinyl acetate resin, polyvinyl alcohol resin, etc.) not related to the present invention. , Olefin resin (norbornene resin, monocyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin, etc.), polyester resin (aromatic polyester, aliphatic polyester, or including them) Copolymers), acrylic resins (including copolymers), polycarbonate resins, polystyrene resins, polysulfone resins, polyarylate resins, and the like. As content of resin other than a cellulose ester, 0.1-30 mass% is preferable.

  The optical film according to the present invention is preferably used for a polarizing plate protective film, a retardation film, and an optical compensation film, and particularly preferably used for a polarizing plate protective film.

<Melt casting method>
The optical film according to the present invention is manufactured by melt casting as described above. The molding method by melt casting, which is heated and melted without using the solvent used in the solution casting method (for example, methylene chloride, etc.), more specifically, melt extrusion molding method, press molding method, inflation method, injection molding method And can be classified into blow molding, stretch molding and the like. Among these, in order to obtain a polarizing plate protective film having excellent mechanical strength and surface accuracy, the melt extrusion molding method is excellent.

  The film forming material is required to have little or no volatile component in the melting and film forming process. This is for foaming during heating and melting to reduce or avoid defects inside the film and flatness deterioration of the film surface.

  The content of the volatile component when the film-forming material is melted is 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less. It is desirable that In the present invention, using a differential thermogravimetric measuring device (TG / DTA200 manufactured by Seiko Denshi Kogyo Co., Ltd.), the heating loss from 30 ° C. to the temperature corresponding to the melt casting is obtained, and the amount is used as the content of volatile components. Yes.

  The film-forming material to be used is preferably removed before film formation or heating, when volatile components represented by the moisture, the solvent and the like are formed. A known drying method can be applied to the removal method, and it can be performed by a method such as a heating method, a reduced pressure method, a heated reduced pressure method, or the like, and may be performed in air or in an atmosphere in which nitrogen is selected as an inert gas. When performing these known drying methods, it is preferable in terms of film quality to be performed in a temperature range where the film-forming material does not decompose.

  By drying before film formation, generation of volatile components can be reduced, and cellulose ester alone or cellulose ester and film forming material, divided into at least one mixture or compatible material other than cellulose ester And can be dried. The drying temperature is preferably 70 ° C. or higher. When a material having a glass transition temperature is present in the material to be dried, heating to a drying temperature higher than the glass transition temperature may cause the material to melt and become difficult to handle. It is preferable that it is below the temperature. When a plurality of substances have a glass transition temperature, the glass transition temperature with the lower glass transition temperature is used as a reference. More preferably, it is 70 degreeC or more and (glass transition temperature-5) degreeC or less, More preferably, it is 110 degreeC or more and (glass transition temperature-20) degreeC or less. The drying time is preferably 0.5 to 24 hours, more preferably 1 to 18 hours, still more preferably 1.5 to 12 hours. If the drying temperature is too low, the removal rate of volatile components will be low, and it will take too much time to dry. Further, the drying process may be divided into two or more stages. For example, the drying process includes a preliminary drying process for storage of materials and a just-before drying process performed immediately before film formation to one week before film formation. Also good.

(Melt extrusion method)
Hereinafter, the manufacturing method of the cellulose ester film of the present invention will be described by taking a melt extrusion molding method as an example.

  FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing a cellulose ester film according to the present invention, and FIG. 2 is an enlarged view of a cooling roll portion from a casting die.

  1 and 2, the method for producing a cellulose ester film according to the present invention is performed by mixing a film material such as cellulose resin and then extruding it from a casting die 4 onto a first cooling roll 5 using an extruder 1. In addition to circumscribing the first cooling roll 5, the film is further circumscribed by the total of three cooling rolls of the second cooling roll 7 and the third cooling roll 8 in order, and solidified by cooling to form a film 10. Next, the film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the film by the stretching device 12 and then wound by the winding device 16. In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5. Details of the touch roll 6 will be described later.

  In the method for producing a cellulose ester film according to the present invention, the conditions for melt extrusion can be carried out in the same manner as the conditions used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less by using a vacuum or reduced pressure drier or a dehumidifying hot air drier.

  For example, the cellulose ester dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1 and filtered through a leaf disk type filter 2 to remove foreign matters.

  When introducing into the extruder 1 from a supply hopper (not shown), it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer 3.

  In the present invention, the cellulose ester and other additives such as an anti-degradation agent added if necessary are preferably mixed before melting, and more preferably mixed before heating. . Mixing may be performed by a mixer or the like, or may be mixed in the cellulose resin preparation process as described above. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, a Henschel mixer, or a ribbon mixer can be used.

  After the film-forming material is mixed as described above, the mixture may be directly melted and formed into a film using the extruder 1, but once the film-forming material is pelletized, the pellet is extruded. The film may be melted by the machine 1 to form a film. Further, when the film forming material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is supplied to the extruder 1. It is also possible to form a film by introducing it. If the film-forming material contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, A method of forming a film is preferred.

  As the extruder 1, various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from a film-forming material, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is necessary, but even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When pellets or braided semi-melts are used once as the film forming material, they can be used in either a single screw extruder or a twin screw extruder.

  In the extruder 1 and the cooling step after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  The melting temperature of the film forming material in the extruder 1 varies depending on the viscosity and discharge amount of the film forming material, the thickness of the sheet to be manufactured, etc., but generally, the glass transition temperature Tg of the film, It is Tg or more and Tg + 130 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 120 ° C. or less.

  The temperature during melt extrusion of the present invention is preferably in the range of 200 ° C. or higher and 270 ° C. or lower. Furthermore, it is preferable that it is the range of 230-260 degreeC.

  The melt viscosity at the time of extrusion is 1 to 10000 Pa · s, preferably 10 to 1000 Pa · s. Further, the residence time of the film forming material in the extruder 1 is preferably shorter, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder 1 and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. is there.

  The shape, rotation speed, and the like of the screw of the extruder 1 are appropriately selected depending on the viscosity and the discharge amount of the film forming material. In the present invention, the shear rate in the extruder 1 is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second.

  The extruder 1 that can be used in the present invention is generally available as a plastic molding machine.

  The film forming material extruded from the extruder 1 is sent to the casting die 4 and extruded from the slit of the casting die 4 in the form of a film. The casting die 4 is not particularly limited as long as it is used for producing a sheet or a film. The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing such as buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like. A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

  The slit of the casting die 4 is configured so that the gap can be adjusted. This is shown in FIG. Of the pair of lips forming the slit 32 of the casting die 4, one is a flexible lip 33 having low rigidity and easily deformed, and the other is a fixed lip 34. A large number of heat bolts 35 are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slits 32. Each heat bolt 5 is provided with a block 36 having an embedded electric heater 37 and a cooling medium passage, and each heat bolt 35 penetrates each block 36 vertically. The base of the heat bolt 35 is fixed to the die body 31, and the tip is in contact with the outer surface of the flexible lip 33. While constantly cooling the block 36, the input to the embedded electric heater 37 is increased or decreased to increase or decrease the temperature of the block 36, thereby causing the heat bolt 35 to thermally expand and contract, thereby displacing the flexible lip 33 and thereby increasing the film thickness. adjust. Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected thereby is fed back to the control device. The thickness information is compared with the set thickness information by the control device, and correction control comes from the same device. It is also possible to control the power or the ON rate of the heat bolt heating element by the amount signal. The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm. Instead of the heat bolt, a gap adjusting member mainly composed of a bolt for adjusting the slit gap by manually moving back and forth in the axial direction may be provided. The slit gap adjusted by the gap adjusting member is usually 200 to 1000 μm, preferably 300 to 800 μm, more preferably 400 to 600 μm.

  The first to third cooling rolls are made of seamless steel pipe having a wall thickness of about 20 to 30 mm, and the surface is finished to a mirror surface. Inside, a pipe for flowing a coolant is arranged so that heat can be absorbed from the film on the roll by the coolant flowing through the pipe. Of the first to third cooling rolls, the first cooling roll 5 corresponds to the rotary support of the present invention.

  On the other hand, the touch roll 6 in contact with the first cooling roll 5 has an elastic surface and is deformed along the surface of the first cooling roll 5 by the pressing force to the first cooling roll 5. A nip is formed between the two. That is, the touch roll 6 corresponds to the pinching rotary body of the present invention.

  In FIG. 4, the schematic cross section of one Embodiment (henceforth, touch roll A) of the touch roll 6 is shown. As shown in the drawing, the touch roll A has an elastic roller 42 disposed inside a flexible metal sleeve 41.

  The metal sleeve 41 is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve 41 is too thin, the strength is insufficient, whereas if it is too thick, the elasticity is insufficient. For these reasons, the thickness of the metal sleeve 41 is preferably 0.1 to 1.5 mm. The elastic roller 42 is formed in a roll shape by providing a rubber 44 on the surface of a metal inner cylinder 43 that is rotatable via a bearing. When the touch roll A is pressed toward the first cooling roll 5, the elastic roller 42 presses the metal sleeve 41 against the first cooling roll 5, and the metal sleep 41 and the elastic roller 42 have the shape of the first cooling roll 5. It deforms corresponding to the familiar shape, and forms a nip with the first cooling roll. Cooling water 45 flows in a space formed between the metal sleeve 41 and the elastic roller 42.

  5 and 6 show a touch roll B which is another embodiment of the pinching rotator. The touch roll B includes a flexible, seamless stainless steel pipe (thickness 4 mm) outer cylinder 51, and a highly rigid metal inner cylinder 52 arranged on the same axis as the inner side of the outer cylinder 51. It is roughly composed. A coolant 54 flows in the space 53 between the outer cylinder 51 and the inner cylinder 52. Specifically, in the touch roll B, outer cylinder support flanges 56a and 56b are attached to the rotation shafts 55a and 55b at both ends, and a thin metal outer cylinder 51 is attached between the outer peripheral portions of the both outer cylinder support flanges 56a and 56b. Yes. A fluid supply pipe 59 is disposed in the same axial center in a fluid discharge hole 58 formed in the axial center portion of one rotary shaft 55a and forming a fluid return passage 57. The fluid supply pipe 59 is thin-walled. It is connected and fixed to a fluid shaft cylinder 60 arranged at the axial center in the metal outer cylinder 51. Inner cylinder support flanges 61a and 61b are attached to both ends of the fluid shaft cylinder 60, respectively, and a thickness of about 15 to 20 mm between the outer periphery of the inner cylinder support flanges 61a and 61b and the other outer cylinder support flange 56b. A metal inner cylinder 52 having a thickness is attached. A cooling liquid flow space 53 of, for example, about 10 mm is formed between the metal inner cylinder 52 and the thin metal outer cylinder 51, and the metal inner cylinder 52 has a flow space 53 and an inner space near both ends. An outlet 52a and an inlet 52b are formed to communicate with the intermediate passages 62a and 62b outside the cylinder support flanges 61a and 61b, respectively.

  Further, the outer cylinder 51 is thinned within a range in which the thin cylinder theory of elastic mechanics can be applied in order to have flexibility, flexibility, and resilience close to rubber elasticity. The flexibility evaluated by the thin-walled cylinder theory is expressed by the thickness t / roll radius r, and the flexibility increases as t / r decreases. In this touch roll B, the flexibility is the optimum condition when t / r ≦ 0.03. Usually, the touch roll generally used has a roll diameter R = 200 to 500 mm (roll radius r = R / 2), a roll effective width L = 500 to 1600 mm, and a horizontally long shape with r / L <1. is there. As shown in FIG. 6, for example, when the roll diameter R = 300 mm and the roll effective width L = 1200 mm, the appropriate range of the wall thickness t is 150 × 0.03 = 4.5 mm or less, but the molten sheet width is 1300 mm. On the other hand, when the average linear pressure is clamped at 98 N / cm, the equivalent spring constant is equal by setting the wall thickness of the outer cylinder 51 to 3 mm compared to the rubber roll of the same shape. The nip width k in the roll rotation direction of the nip is also about 9 mm, which is almost the same as the nip width of this rubber roll of about 12 mm. The deflection amount at the nip width k is about 0.05 to 0.1 mm.

  Here, t / r ≦ 0.03. However, in the case of a general roll diameter R = 200 to 500 mm, flexibility is sufficiently obtained especially in the range of 2 mm ≦ t ≦ 5 mm. Thinning by processing can be easily performed, and it is an extremely practical range. If the wall thickness is 2 mm or less, high-precision processing cannot be performed due to elastic deformation during processing.

  The converted value of 2 mm ≦ t ≦ 5 mm is 0.008 ≦ t / r ≦ 0.05 with respect to a general roll diameter, but in practical use, the roll diameter under the condition of t / r≈0.03. The wall thickness should be increased in proportion to For example, when roll diameter: R = 200, t = 2 to 3 mm, and when roll diameter: R = 500, t = 4 to 5 mm.

  The touch rolls A and B are urged toward the first cooling roll by urging means (not shown). The urging force of the urging means is F, and the value F / W (linear pressure) obtained by dividing the width of the film in the nip in the direction along the rotation axis of the first cooling roll 5 is 9.8 to 147 N / cm. Set to According to the present embodiment, a nip is formed between the touch rolls A and B and the first cooling roll 5, and the flatness may be corrected while the film passes through the nip. Accordingly, since the film is sandwiched over a long time with a small linear pressure compared to the case where the touch roll is formed of a rigid body and no nip is formed between the first cooling roll and the flatness is more reliably corrected. Can do. That is, when the linear pressure is smaller than 9.8 N / cm, the die line cannot be sufficiently eliminated. On the other hand, if the linear pressure is greater than 147 N / cm, the film is difficult to pass through the nip, resulting in unevenness in place of the film thickness.

  Moreover, since the surface of the touch rolls A and B can be made smoother than the case where the surface of the touch rolls is made of rubber, the surface of the touch rolls A and B can be made smoother. Can be obtained. In addition, as a material of the elastic body 44 of the elastic roller 42, ethylene propylene rubber, neoprene rubber, silicon rubber, or the like can be used.

  Now, in order to satisfactorily eliminate the die line by the touch roll 6, it is important that the viscosity of the film when the touch roll 6 clamps the film is in an appropriate range. Cellulose esters are known to have a relatively large change in viscosity with temperature. Therefore, in order to set the viscosity when the touch roll 6 clamps the cellulose ester film to an appropriate range, it is important to set the temperature of the film when the touch roll 6 clamps the cellulose film to an appropriate range. It becomes. And when this inventor sets the glass transition temperature of a cellulose-ester film to Tg, if the temperature T of the film just before a film is pinched by the touch roll 6 is set so that Tg <T <Tg + 110 degreeC may be satisfy | filled. I found a good thing. If the film temperature T is lower than Tg, the viscosity of the film is too high and the die line cannot be corrected. On the contrary, if the temperature T of the film is higher than Tg + 110 ° C., the film surface and the roll do not adhere uniformly, and the die line cannot be corrected. Preferably, Tg + 10 ° C. <T2 <Tg + 90 ° C., more preferably Tg + 20 ° C. <T2 <Tg + 70 ° C. In order to set the temperature of the film when the touch roll 6 clamps the cellulose ester film to an appropriate range, the first cooling is performed from the position P1 at which the melt extruded from the casting die 4 contacts the first cooling roll 5. The length L of the nip between the roll 5 and the touch roll 6 along the rotation direction of the first cooling roll 5 may be adjusted.

  In the present invention, preferred materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like. The surface accuracy is preferably increased, and the surface roughness is set to 0.3 S or less, more preferably 0.01 S or less.

  In the present invention, it was discovered that the die line correction effect is more greatly manifested by reducing the pressure from the opening (lip) of the casting die 4 to the first roll 5 to 70 kPa or less. The reduced pressure is preferably 50 to 70 kPa. Although there is no restriction | limiting in particular as a method of keeping the pressure of the part from the opening part (lip | rip) of the casting die 4 to the 1st roll 5 below 70 kPa, Cover the roll periphery from the casting die 4 with a pressure | voltage resistant member, and reduce pressure. There are methods. At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached. In the present invention, if the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure to an appropriate value.

  In the present invention, a film-like cellulose ester in a molten state is transferred from the T die 4 to the first roll (first cooling roll) 5, the second cooling roll 7, and the third cooling roll 8 in order and cooled while being conveyed. Solidifying to obtain an unstretched cellulose ester film 10.

  In the embodiment of the present invention shown in FIG. 1, the cooled and solidified unstretched film 10 peeled from the third cooling roll 8 by the peeling roll 9 is guided to a stretching machine 12 via a dancer roll (film tension adjusting roll) 11. Therefore, the film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  As a method for stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, it is preferable to set the stretching direction to the width direction because lamination with a polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the cellulose ester film made of the cellulose ester film becomes the width direction.

  On the other hand, the transmission axis of the polarizing film is also usually in the width direction. By incorporating a polarizing plate in which the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other into the liquid crystal display device, the display contrast of the liquid crystal display device can be increased and a good viewing angle can be obtained. Is obtained.

  The glass transition temperature Tg of the film forming material can be controlled by varying the material type constituting the film and the ratio of the constituting material. When producing a retardation film as a cellulose ester film, Tg is preferably 120 ° C. or higher, and more preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source. At this time, if the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed. If the Tg of the film is too high, the temperature is increased when the film forming material is made into a film, so that the energy consumption for heating becomes high, and the material itself may be decomposed when it is made into a film, resulting in coloring. Therefore, Tg is preferably 250 ° C. or lower.

  The stretching step may be performed by known heat setting conditions, cooling, and relaxation treatment, and may be appropriately adjusted so as to have the characteristics required for the target optical film.

  In order to provide the physical properties of the retardation film and the function as a retardation film for expanding the viewing angle of the liquid crystal display device, the stretching step and the heat setting treatment are appropriately selected and performed. When such a stretching step and heat setting treatment are included, the heating and pressurizing step is performed before the stretching step and heat setting treatment.

  When producing a retardation film as a cellulose ester film and further combining the functions of a polarizing plate protective film, it is necessary to control the refractive index, but the refractive index can be controlled by a stretching operation. Operation is the preferred method. Hereinafter, the stretching method will be described.

  In the retardation film stretching step, the required litter is obtained by stretching 1.0 to 2.0 times in one direction of the cellulose resin and 1.01 to 2.5 times in the direction perpendicular to the film plane. The foundation Ro and Rt can be controlled. Here, Ro indicates in-plane retardation, and Rt indicates thickness direction retardation.

  Retardation Ro and Rt are calculated | required by a following formula.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film (refractive index is 23 ° C., 55%) (Measured at a wavelength of 590 nm in an RH environment), d represents the thickness (nm) of the film.)
The refractive index of the optical film is an Abbe refractometer (4T), the thickness of the film is a commercially available micrometer, and the retardation value is an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Etc.) can be used for each measurement.

  Stretching can be performed, for example, sequentially or simultaneously in the longitudinal direction of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and film breakage may occur.

  For example, when stretching in the melt casting direction, if the shrinkage in the width direction is too large, the value of nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed in the width direction. This distribution may appear when the tenter method is used. By stretching the film in the width direction, a shrinkage force is generated at the center of the film, and the phenomenon is caused by the end being fixed. It is thought to be called the Boeing phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

  By stretching in the biaxial directions perpendicular to each other, the film thickness variation of the obtained film can be reduced. When the film thickness variation of the retardation film is too large, unevenness of the retardation is caused, and unevenness such as coloring may be a problem when used in a liquid crystal display device.

  The film thickness variation of the cellulose ester film is preferably ± 3%, more preferably ± 1%. For the purposes as described above, the method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratio in the biaxial directions perpendicular to each other is finally 1.0 to 2.0 times in the casting direction. The width direction is preferably 1.01 to 2.5 times, the casting direction is 1.01 to 1.5 times, and the width direction is 1.05 to 2.0 times. It is more preferred to obtain the required retardation value.

  When the absorption axis of the polarizer exists in the longitudinal direction, the transmission axis of the polarizer coincides with the width direction. In order to obtain a long polarizing plate, the retardation film is preferably stretched so as to obtain a slow axis in the width direction.

When cellulose ester that obtains positive birefringence with respect to stress is used, the slow axis of the retardation film can be provided in the width direction by stretching in the width direction from the above configuration. In this case, in order to improve the display quality, the slow axis of the retardation film is preferably in the width direction, and in order to obtain the desired retardation value,
Formula (stretch ratio in the width direction)> (stretch ratio in the casting direction)
It is necessary to satisfy the following conditions.

  After stretching, after slitting the edge of the film to a product width by the slitter 13, the film is subjected to knurling (embossing) on both ends of the film by a knurling device comprising an embossing ring 14 and a back roll 15. By winding with the winder 16, sticking in the cellulose ester film (original winding) F and generation of scratches are prevented. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  Next, in the film winding process, the film is wound on the take-up roll while keeping the shortest distance between the outer peripheral face of the cylindrical roll film and the outer peripheral face of the mobile transport roll immediately before the roll. It is. In addition, a means such as a static elimination blower for removing or reducing the surface potential of the film is provided in front of the winding roll.

  The winder related to the production of the optical film of the present invention may be generally used, and it may be a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up. In addition, it is preferable that the initial winding tension at the time of winding of the optical film is 90.2 to 300.8 N / m.

  In the film winding step in the method of the present invention, the film is preferably wound under environmental conditions of a temperature of 20 to 30 ° C. and a humidity of 20 to 60% RH. Thus, the tolerance of the humidity change of the thickness direction retardation (Rt) improves by prescribing the temperature and humidity in the film winding process.

  If the temperature in the winding process is less than 20 ° C., wrinkles are generated and the film winding quality is deteriorated, which is unpractical. If the temperature in the film winding process exceeds 30 ° C., wrinkles are also generated, and the film winding quality is deteriorated, so that it cannot be put into practical use.

  Moreover, if the humidity in the film winding process is less than 20% RH, it is not preferable because it is easily charged and cannot be put into practical use due to deterioration in film winding quality. If the humidity in the film winding process exceeds 60% RH, the winding quality, sticking failure, and transportability deteriorate, which is not preferable.

  When winding the optical film into a roll, the wound core may be any material as long as it is a cylindrical core, but is preferably a hollow plastic core, and the plastic material is heated. Any heat-resistant plastic that can withstand the processing temperature may be used, and examples thereof include phenol resins, xylene resins, melamine resins, polyester resins, and epoxy resins. A thermosetting resin reinforced with a filler such as glass fiber is preferred. For example, a hollow plastic core: a wound core made of FRP and having an outer diameter of 6 inches (hereinafter, inch represents 2.54 cm) and an inner diameter of 5 inches is used.

  The number of windings to these winding cores is preferably 100 windings or more, more preferably 500 windings or more, the winding thickness is preferably 5 cm or more, and the width of the film substrate is 80 cm or more. It is preferably 1 m or more.

  Although the thickness of the film of the optical film according to the present invention varies depending on the purpose of use, the finished film is preferably 10 to 500 μm. In particular, the lower limit is 20 μm or more, preferably 35 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less. A particularly preferable range is 25 to 90 μm. In the case where the optical film of the present invention is a retardation film and also serves as a polarizing plate protective film, if the film is thick, the polarizing plate after polarizing plate processing becomes too thick, and in a liquid crystal display used for a notebook computer or a mobile electronic device Especially not suitable for thin and lightweight purposes. On the other hand, if the film is thin, it is difficult to develop retardation as a retardation film. In addition, the moisture permeability of the film increases, and the ability to protect the polarizer from humidity decreases, which is not preferable.

  When the slow axis or the fast axis of the retardation film exists in the film plane and the angle formed with the film forming direction is θ1, θ1 is −1 to + 1 °, preferably −0.5 to + 0.5 °. To be.

  This θ1 can be defined as an orientation angle, and the measurement of θ1 can be performed using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments).

  When each θ1 satisfies the above relationship, it contributes to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to faithful color reproduction in a color liquid crystal display device.

  When the retardation film is used for the multi-domain VA mode, the retardation film is arranged in the above region with the fast axis of the retardation film being θ1, which contributes to the improvement of display image quality. When the plate and the liquid crystal display device are in the MVA mode, for example, the configuration shown in FIG. 7 can be adopted.

  In FIG. 7, 21a and 21b are protective films, 22a and 22b are retardation films, 25a and 25b are polarizers, 23a and 23b are slow axis directions of the film, 24a and 24b are transmission axis directions of the polarizer, 26a, Reference numeral 26b denotes a polarizing plate, 27 denotes a liquid crystal cell, and 29 denotes a liquid crystal display device.

  The retardation Ro distribution in the in-plane direction of the cellulose ester film is preferably adjusted to 5% or less, more preferably 2% or less, and particularly preferably 1.5% or less. The retardation Rt distribution in the thickness direction of the film is preferably adjusted to 10% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  In the retardation film, it is preferred that the retardation value distribution fluctuation is small. When a polarizing plate including a retardation film is used in a liquid crystal display device, the retardation distribution fluctuation is preferably small from the viewpoint of preventing color unevenness and the like. .

  The retardation film is adjusted to have a retardation value suitable for improving the display quality of the VA mode or TN mode liquid crystal cell, and is preferably used for the MVA mode by dividing the retardation film into the above multi-domain as the VA mode. To achieve this, it is required to adjust the in-plane retardation Ro to a value greater than 30 nm and 95 nm or less, and a thickness direction retardation Rt greater than 70 nm and 400 nm or less.

  The in-plane retardation Ro is observed from the normal direction of the display surface when the two polarizing plates are arranged in crossed Nicols and the liquid crystal cell is arranged between the polarizing plates, for example, in the configuration shown in FIG. When the light is in the crossed Nicol state with respect to the time when the display is taken, the polarizing plate is displaced from the crossed Nicol state when observed obliquely from the normal of the display surface, and light leakage caused by this is mainly compensated. The retardation in the thickness direction mainly compensates for the birefringence of the liquid crystal cell similarly observed when viewed from an oblique direction when the liquid crystal cell is in a black display state in the TN mode or VA mode, particularly in the MVA mode. To contribute.

  As shown in FIG. 7, in the liquid crystal display device, when two polarizing plates are arranged above and below the liquid crystal cell, 22a and 22b in the figure can select the distribution of the thickness direction retardation Rt. Preferably, the total value of both of the above-mentioned ranges and the thickness direction retardation Rt is larger than 140 nm and 500 nm or less. In this case, in-plane retardation Ro and thickness direction retardation Rt of 22a and 22b are preferably the same for improving productivity of an industrial polarizing plate. Particularly preferably, the in-plane retardation Ro is larger than 35 nm and not larger than 65 nm, and the thickness direction retardation Rt is larger than 90 nm and not larger than 180 nm, and is applied to the MVA mode liquid crystal cell in the configuration of FIG. .

  In a liquid crystal display device, for example, a TAC film having an in-plane retardation Ro = 0 to 4 nm and a thickness direction retardation Rt = 20 to 50 nm and a thickness of 35 to 85 μm as a commercially available polarizing plate protective film is provided on one polarizing plate. 7 is used at the position 22b, the polarizing film disposed on the other polarizing plate, for example, the retardation film disposed on 22a in FIG. 7, has an in-plane retardation Ro of more than 30 nm and not more than 95 nm. In addition, use of a film having a thickness direction retardation Rt of greater than 140 nm and not greater than 400 nm is preferable from the viewpoint of improving the display quality and producing the film.

"recycling"
In the film forming process, the clip gripping portions at both ends of the cut film are pulverized or granulated as necessary, and then used as a film material of the same product type or as a film material of a different product type. It is preferable to reuse.

《Functional layer》
In producing the optical film of the present invention, before and / or after stretching, an antistatic layer, a transparent conductive layer, a hard coat layer, an antireflection layer, an antifouling layer, a slippery layer, an easy adhesion layer, an antiglare layer, and a gas barrier. A functional layer such as a layer or an optical compensation layer may be provided. In particular, it is preferable to provide at least one layer selected from an antistatic layer, a hard coat layer, an antireflection layer, an easy adhesion layer, an antiglare layer and an optical compensation layer. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

"Polarizer"
When using the optical film which concerns on this invention as a polarizing plate protective film, the preparation methods of a polarizing plate are not specifically limited, It can manufacture by a general method. The back side of the optical film of the present invention is subjected to alkali saponification treatment, and a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizing film prepared by immersing and stretching the treated optical film in an iodine solution. It is preferable to bond them together. The optical film of the present invention may be used on the other surface, or another polarizing plate protective film may be used. With respect to the optical film of the present invention, a commercially available cellulose ester film can be used as the polarizing plate protective film used on the other surface. For example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3, KC8UCR-4, KC4FR-1, KC8UY-HA, KC8UX-RHA (manufactured by Konica Minolta Opto, Inc.) Etc.) are preferably used. Alternatively, it is also preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optical anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348. By using in combination with the optical film of the present invention, a polarizing plate having excellent flatness and a stable viewing angle expansion effect can be obtained. Or you may use films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate, as a polarizing plate protective film of the other surface.

  Instead of the alkali treatment, polarizing plate processing may be performed by performing easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232.

 The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. The thickness of the polarizing film is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm. On the surface of the polarizing film, one side of the cellulose ester film of the present invention is bonded to form a polarizing plate. It is preferably bonded with a water-based adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

  Since the polarizing film is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high-temperature and high-humidity environment, the stretching direction (usually the longitudinal direction) shrinks, and the direction perpendicular to the stretching (usually the width direction) ) Will grow. As the thickness of the polarizing plate protective film becomes thinner, the expansion / contraction ratio of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizing film increases. Normally, the stretching direction of the polarizing film is bonded to the casting direction (MD direction) of the polarizing plate protective film. Therefore, when making the polarizing plate protective film thin, it is particularly important to suppress the stretching rate in the casting direction. It is. Since the optical film of the present invention is extremely excellent in dimensional stability, it is suitably used as such a polarizing plate protective film.

  That is, the optical film of the present invention does not increase the wavy unevenness even in the durability test under the conditions of 60 ° C. and 90% RH, and even if it is a polarizing plate having an optical compensation film on the back side. It is possible to provide good visibility without changing the viewing angle characteristics after the test.

  The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and can further be constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal board, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

<Liquid crystal display device>
A polarizing plate including a polarizing plate protective film (including a case where it also serves as a retardation film) using the optical film of the present invention can exhibit high display quality as compared with a normal polarizing plate, particularly a multi-domain type. The liquid crystal display device is more suitable for use in a multi-domain liquid crystal display device, more preferably by a birefringence mode.

  The polarizing plate of the present invention includes an MVA (Multi-domain Vertical Alignment) mode, a PVA (Patterned Vertical Alignment) mode, an OCB (Optical Compensated Bend Mode), an OCB (Optical Compensation Bend mode) It can be used, and is not limited to a specific liquid crystal mode and the arrangement of polarizing plates.

  Liquid crystal display devices are being applied as devices for colorization and moving image display, and the display quality is improved by the present invention, and the improvement of contrast and the resistance of polarizing plates improve the display of moving images that are less fatigued and faithful. It becomes possible.

  In a liquid crystal display device including at least a polarizing plate including a retardation film, one polarizing plate including a polarizing plate protective film as the optical film of the present invention is disposed on the liquid crystal cell, or on both sides of the liquid crystal cell. Place two in a row. At this time, it can contribute to the improvement of display quality by using the polarizing plate protective film side included in the polarizing plate so as to face the liquid crystal cell of the liquid crystal display device. In FIG. 7, the films 22a and 22b face the liquid crystal cell of the liquid crystal display device.

  In such a configuration, the polarizing plate protective film as the optical film of the present invention can optically compensate the liquid crystal cell. When the polarizing plate of the present invention is used in a liquid crystal display device, at least one polarizing plate in the liquid crystal display device may be the polarizing plate of the present invention. By using the polarizing plate of the present invention, a liquid crystal display device with improved display quality and excellent viewing angle characteristics can be provided.

  In the polarizing plate of the present invention, a polarizing plate protective film of a cellulose derivative is used on the surface opposite to the polarizing plate protective film as the optical film of the present invention as viewed from the polarizer, and a general-purpose TAC film or the like is used. Can do. The polarizing plate protective film located on the side far from the liquid crystal cell can be provided with another functional layer in order to improve the quality of the display device.

  For example, it may be affixed to a film containing a known functional layer as a constituent for display in order to prevent reflection, anti-glare, scratch resistance, dust adhesion prevention, brightness improvement, or the polarizing plate surface of the present invention. It is not limited to.

  In general, a retardation film is required to obtain stable optical characteristics that the above-described retardation Ro or Rt does not fluctuate little. In particular, in a liquid crystal display device in a birefringence mode, these fluctuations may cause image unevenness.

  Since the long polarizing plate protective film produced by the melt casting film forming method according to the present invention is mainly composed of cellulose ester, it is possible to utilize an alkali treatment step by utilizing saponification inherent to cellulose ester. it can. When the resin which comprises a polarizer is polyvinyl alcohol, this can be bonded with a polarizing plate protective film using the completely saponified polyvinyl alcohol aqueous solution similarly to the conventional polarizing plate protective film. For this reason, this invention is excellent in the point which can apply the conventional polarizing plate processing method, and is excellent especially in the point from which the roll polarizing plate which is elongate is obtained.

  The production effect obtained by the present invention becomes more remarkable particularly in a long roll of 100 m or more, and the longer the length is 1500 m, 2500 m, or 5000 m, the more the production effect of polarizing plate production is obtained.

  For example, in the production of a polarizing plate protective film, the roll length is 10 to 5000 m, preferably 50 to 4500 m in consideration of productivity and transportability. At this time, the width of the film is the width of the polarizer or the production line. A suitable width can be selected. A film with a width of 0.5 to 4.0 m, preferably 0.6 to 3.0 m, may be wound into a roll shape and used for polarizing plate processing. After being manufactured and wound on a roll, it may be cut to obtain a roll having a desired width, and such a roll may be used for polarizing plate processing.

  In the production of the polarizing plate protective film, functional layers such as an antistatic layer, a hard coat layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer may be coated before and / or after stretching. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

  It is also possible to produce a cellulose ester film having a laminated structure by co-extrusion of a composition containing cellulose esters having different additive concentrations such as the plasticizer, ultraviolet absorber and matting agent. For example, a cellulose ester film having a structure of skin layer / core layer / skin layer can be produced. For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. The glass transition temperature of the skin layer and the core layer may be different, and the glass transition temperature of the core layer is preferably lower than the glass transition temperature of the skin layer. At this time, the glass transition temperatures of both the skin and the core can be measured, and an average value calculated from these volume fractions can be defined as the glass transition temperature Tg and similarly handled. Also, the viscosity of the melt containing the cellulose ester during melt casting may be different between the skin layer and the core layer, and the viscosity of the skin layer> the viscosity of the core layer or the viscosity of the core layer ≧ the viscosity of the skin layer may be used.

  The cellulose ester film according to the present invention has a dimensional stability with a dimensional fluctuation value of ± 2.80 ° C. and 90% RH, based on the dimensions of the film left at 23 ° C. and 55% RH for 24 hours. It is less than 0%, preferably less than 1.0%, more preferably less than 0.5%.

  When the cellulose ester film according to the present invention is used as a retardation film for a polarizing plate protective film, the retardation film itself has fluctuations within the above range, and the retardation retardation value and the orientation angle are initially This setting is preferable because it does not cause a decrease in display quality improvement capability or display quality deterioration.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Synthesis of cellulose ester>
(Synthesis of cellulose ester 1)
80 g of acetic acid and 30 g of propionic acid were added to 30 g of cellulose (dissolved pulp manufactured by Nippon Paper Industries Co., Ltd.), and the mixture was stirred at 54 ° C. for 30 minutes. After the mixture was cooled, esterification was performed by adding 7 g of acetic anhydride, 120 g of propionic anhydride, and 1.2 g of sulfuric acid cooled in an ice bath. Stirring was performed for 150 minutes while adjusting the esterification so as not to exceed 40 ° C. After completion of the reaction, a mixture of 30 g of acetic acid and 10 g of water was added dropwise over 20 minutes to hydrolyze excess anhydride. While maintaining the temperature of the reaction solution at 40 ° C., 90 g of acetic acid and 30 g of water were added and stirred for 1 hour. The mixture was poured into an aqueous solution containing 2 g of magnesium acetate, stirred for a while, filtered, sufficiently washed with water until the pH of the washing solution became neutral, and then dried to obtain cellulose ester 1. With respect to the obtained cellulose ester 1, when the substitution degree (X) of the acetyl group and the substitution degree (Y) of the propionyl group were determined by the method prescribed in ASTM D817-96, X = 1.31, Y = 1.23. Moreover, when the number average molecular weight was calculated | required by the gel permeation chromatography on the above-mentioned conditions, it was 66000, Furthermore, 1% mass reduction | decrease temperature Td (1.0) in the air was used using a differential thermogravimetric analyzer. It was 292 degreeC when measured.

(Synthesis of cellulose esters 2 to 15)
For the synthesis of cellulose ester 1, the same synthetic operation as the synthesis of cellulose ester 1 was carried out except that the amounts of acetic acid, acetic anhydride, propionic acid and propionic anhydride were changed, and cellulose esters 2 to 15 were obtained. It was.

  For each of the cellulose esters 1-15, the degree of substitution of the acetyl group (X), the degree of substitution of the propionyl group (Y), the value of X + Y, the value of XY, the number average molecular weight (Mn), and 1% mass reduction Table 1 shows the value of the temperature Td (1.0).

(Synthesis of comparative cellulose esters 16-25)
Here, the comparative cellulose esters 16 to 23 were the same as the cellulose ester 1 except that the amounts of acetic acid, acetic anhydride, propionic acid, and propionic anhydride were changed with respect to the synthesis of the cellulose ester 1. Was synthesized. On the other hand, the comparative cellulose esters 24 and 25 are the same as the cellulose ester 1 except that a combination of acetic acid, acetic anhydride, butyric acid, and butyric anhydride is used for the synthesis of the cellulose ester 1 and the amount used is further changed. The synthesis was performed by performing the same synthesis operation.

  For each of the obtained comparative cellulose esters 16 to 25, the substitution degree of acetyl group (X), the substitution degree of propionyl group (Y), the value of X + Y, the value of XY or the substitution degree of butyryl group (Z ), X + Z, X-Z, and number average molecular weight (Mn), 1% mass reduction temperature Td (1.0) are shown in Table 1.

Example 1
[Production of Optical Film Having Cellulose Ester (hereinafter, simply referred to as Cellulose Ester Film) Sample 1-1]
As described below, the cellulose ester film 1-1 of the present invention was produced by melt casting using the synthesized cellulose ester and various additives.

Cellulose ester 1 100 parts by weight Plasticizer-A 8 parts by weight IRGANOX 1010 (manufactured by Ciba Specialty Chemicals) 0.50 parts by weight GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.25 parts by weight Sumizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.25 parts by mass TINUVIN 928 (manufactured by Ciba Specialty Chemicals) 1.5 parts by mass The cellulose ester 1 was dried at 130 ° C. under reduced pressure for 4 hours and cooled to room temperature, and then the additives were mixed. The above mixture was melt-mixed at 230 ° C. using a twin-screw extruder and pelletized. In addition, the glass transition temperature Tg of this pellet was 140 degreeC.

  Using this pellet, it was melted at 250 ° C. in a nitrogen atmosphere, extruded from the casting die 4 onto the first cooling roll 5, and formed by pressing the film between the first cooling roll 5 and the touch roll 6. . Further, from the hopper opening in the middle of the extruder 1, 0.2 parts by mass of silica particles, Aerosil NAX50 (manufactured by Nippon Aerosil Co., Ltd.) as a slip agent, and 0.02 parts by mass of KE-P100 (manufactured by Nippon Shokubai Co., Ltd.) Was added.

  The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations. The touch roll A was used as the touch roll, and 80 ° C. water was poured as cooling water therein.

  From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the peripheral surface of the cooling roller 5 was set to 20 mm. Thereafter, the touch roll 6 was separated from the first cooling roll 5, and the temperature T of the melted part immediately before being sandwiched between the first cooling roll 5 and the touch roll 6 was measured. In the present embodiment, the temperature T of the melted part immediately before being sandwiched between the nips of the first cooling roll 5 and the touch roll 6 is 1 mm upstream from the nip upstream end P2, and a thermometer (an independent meter). It was measured by HA-200E manufactured by Co., Ltd. As a result of the measurement in this example, the temperature T was 141 ° C. The linear pressure of the touch roll 6 against the first cooling roll 5 was 14.7 N / cm. Furthermore, after being introduced into a tenter and stretched 1.3 times at 160 ° C in the width direction, it was cooled to 30 ° C while relaxing 3% in the width direction, then released from the clip, the clip gripping part was cut off, and both ends of the film Was subjected to a knurling process with a width of 10 mm and a height of 5 μm, and wound on a winding core with a winding tension of 220 N / m and a taper of 40%. The extrusion amount and the take-up speed were adjusted so that the film had a thickness of 80 μm, and the finished film width was slit and wound up so as to have a width of 1430 mm. The winding core had an inner diameter of 152 mm, an outer diameter of 165 to 180 mm, and a length of 1550 mm. A prepreg resin obtained by impregnating glass fibers and carbon fibers with an epoxy resin was used as the core material for the core. The surface of the core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 μm. The winding length was 2500 m. Let this film original fabric sample of this invention be a cellulose-ester film original fabric 1-1. In addition, a part of the cellulose ester film is cut out from the original film sample, and this is used as the cellulose ester film 1-1 of the present invention.

[Production of Cellulose Ester Film 1-2 to 1-25]
In the production of the cellulose ester film raw fabric 1-1, the cellulose ester film raw fabric 1-2 to 1-15 of the present invention and comparative cellulose were similarly prepared except that the type of cellulose ester was changed as shown in Table 1. Ester film original fabrics 1-16 to 1-25 were produced. In addition, the addition amount of the cellulose ester replaced with the used cellulose ester 1 was the same mass part as the cellulose ester 1. Further, in the same manner as described above, a part of the cellulose ester film is cut out from the cellulose ester film raw fabric 1-2 to 1-15 of the present invention and the comparative cellulose ester film raw fabric 1-16 to 1-25, and each of these is cut into a book. It is set as the cellulose ester film 1-2 to 1-15 of the invention, and the comparative cellulose ester film 1-16 to 1-25.

  The structures of Plasticizer-A, IRGANOX 1010, GSY-P101, Sumilizer GS, and TINUVIN 928 used in Example 1 are as follows. Cellulose esters 1 to 23 are cellulose acetate propionate, and cellulose esters 24 and 25 are cellulose acetate butyrate.

  The obtained cellulose ester film original fabric sample and the cellulose ester film sample were evaluated by the following methods. The results are shown in Table 2.

《Horse spine failure, core transfer》
The wound cellulose ester film original sample is wrapped twice with a polyethylene sheet and stored for 30 days under conditions of 25 ° C. and 50% by the storage method as shown in FIGS. 8 (a), (b) and (c). saved. After that, take it out of the box, open the polyethylene sheet, reflect the reflected fluorescent tube on the film surface, observe the distortion or fine disturbance, and rank it as the following level as an evaluation of horse back failure did.

◎: Fluorescent lamp looks straight △: Fluorescent lamp appears to be bent partially ×: Fluorescent lamp appears to be mottled In addition, the original film sample after storage is rewound to form a spot-shaped deformation of 50 μm or more, Alternatively, it was measured how many meters of the core transfer, in which the strip-shaped deformation in the width direction was clearly visible, from the core portion, and was ranked according to the following levels.

◎: Less than 15 m from the core part ○: Less than 15-30 m from the core part △: Less than 30-50 m from the core part X: 50 m or more from the core part << winding wrinkle >>
An operation of winding the original film on the core was performed, and when wrinkles occurred at the beginning of the winding and it became defective, the original film was removed from the core and the operation of rewinding was performed. The number of defects at this time was counted. This operation was averaged 10 times and ranked to the following levels.

◎: 0 times or more and less than 1 time ○: 1 time or more and less than 3 times △: 3 times or more and less than 5 times ×: 5 times or more << Flatness >>
Cut each cellulose ester film sample into a size of 90cm in width and 100cm in length, and arrange 5 samples of 50W fluorescent lamps at a height of 1.5m so that the sample table can be illuminated from an angle of 45 °. Each film sample was placed on the surface, and the unevenness that appeared to be reflected on the film surface was visually observed and judged as follows. By this method, it is possible to determine “tsun” and “wrinkle”.

◎: All five fluorescent lamps looked straight ○: Some fluorescent lamps appear to be bent slightly △: Fluorescent lamps appear to be slightly bent overall ×: Fluorescent lamps appear to swell largely << Evaluation of curling properties >>
A 5 mm × 5 cm cellulose ester film sample was cut out, left in a constant temperature and humidity chamber at 28 ° C. and 55% RH for 24 hours, placed on a flat plate, and using a curvature scale, a curvature having a curve matching the sample. The radius was determined, and the curl size and ease of handling were ranked as follows.

Curvature radius: 1 / radius of a circle with a curve that matches the sample (1 / m)
◎: Less than 0-5 ◯: Less than 5-10 △: Less than 10-30 x: 30 or more Here, ◎ and ○ are easy to handle, but below △ are extremely difficult to handle.

<Retardation coefficient of variation (CV)>
Retardation is measured at intervals of 1 cm in the width direction of the cellulose ester film, and is represented by a retardation variation coefficient (CV) obtained from the following formula. For measurement, an automatic birefringence meter KOBURA · 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) was used, and it was three-dimensional at 1 cm intervals in the width direction of the sample at a wavelength of 590 nm in an environment of 28 ° C and 55% RH The birefringence was measured and the measured value was substituted into the following equation.

In-plane retardation Ro = (nx−ny) × d
Thickness direction retardation Rt = ((nx + ny) / 2−nz) × d
In the formula, d is the thickness (nm) of the film, the refractive index nx (the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction), ny (the direction perpendicular to the slow axis in the film plane). ) (Refractive index of the film in the thickness direction). The standard deviation by the (n-1) method was calculated | required for the obtained in-plane and thickness direction retardation, respectively. For the retardation distribution, the coefficient of variation (CV) shown below was obtained and used as an index. In actual measurement, n was set to 130 to 140.

Coefficient of variation (CV) = standard deviation / retardation average value ◎: variation (CV) is less than 1.5% ○: variation (CV) is 1.5% or more and less than 5% Δ: variation (CV) is 5% Or more, less than 10% ×: variation (CV) is 10% or more << Saponification Applicability >>
A 120 μm-thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer. The cellulose ester film sample was alkali-treated with a 2.5N aqueous sodium hydroxide solution at 40 ° C. for 60 seconds, further washed with water and dried to saponify the surface. The polarizing plate for evaluation which bonded the protective film to the both sides of the said polarizer by bonding the alkali treatment surface of the said cellulose-ester film from both surfaces by using the completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive agent was produced.

  Next, this polarizing plate for evaluation was treated at 80 ° C. and 90% RH for 1200 hours, and the bonded state of the polarizer and the protective film was observed and ranked according to the following criteria.

◎: No peeling ○: Slight peeling is observed but there is no practical problem △: Slight peeling is recognized and practically problematic ×: Peeling occurs Here, ○ or more is a level where there is no practical problem in saponification suitability It was judged.

《Polarizing plate durability test (whiteout)》
Two 500 mm × 500 mm polarizing plate samples prepared during the saponification suitability evaluation were heat-treated (conditions: left at 90 ° C. for 120 hours) to obtain either the vertical or horizontal center line portion when placed in an orthogonal state. The length of the white part of the larger edge was measured to calculate the ratio to the side length (500 mm), and the following determination was made according to the ratio. Edge blanking can be determined visually by the fact that the edge portion of the polarizing plate that does not transmit light in an orthogonal state passes light. In the state of the polarizing plate, the display of the edge portion becomes invisible.

A: Edge blank is less than 5%. B: Edge blank is not less than 5% and less than 10%. B: Edge blank is not less than 10% and less than 20%. X: Edge blank is not less than 20%. The above was judged to be a practically acceptable level.

  As mentioned above, from the results of Table 2, the cellulose ester film original fabric samples 1-1 to 1-15 of the present invention are stored for a long period of time with respect to the cellulose ester film original fabric samples 1-16 to 1-25 of the comparative example. However, it can be seen that this is a cellulose ester film that is less susceptible to horse back failure and core transfer, and is less prone to deformation failures of the original film such as wrinkles at the beginning of winding. Further, regarding the cellulose ester film itself cut out from the raw fabric, it can be seen that the cellulose ester film of the present invention is a cellulose ester film having high flatness and suitability for saponification treatment, and having small fluctuations in curling properties and retardation. . Furthermore, it can be seen that the polarizing plate produced using the cellulose ester film of the present invention has good durability and is an optical film excellent in practical use.

Example 2
The cellulose ester of the present invention is the same as the cellulose ester film raw fabric 1-1 of Example 1 except that it is changed to the combination of cellulose ester, plasticizer, deterioration inhibitor and ultraviolet absorber shown in Table 3. In the same manner as the original film film 2-1 to 2-18 and the comparative cellulose ester film films 2-19 and 2-20, and the cellulose ester film 1-1 of Example 1, the cellulose ester of the present invention Films 2-1 to 2-18 and comparative cellulose ester films 2-19 and 2-20 were produced. Further, polarizing plates 2-1 to 2-18 of the present invention and comparative polarizing plates 2-19 and 2-20 were produced in the same manner as the polarizing plate 1-1 of Example 1. In addition, the numerical value in the bracket | parenthesis described in the column of the plasticizer in FIG. 3, a deterioration inhibitor, and an ultraviolet absorber represents the mass part of each material used with respect to 100 mass parts of cellulose esters.

  In addition, the plasticizer-B, the plasticizer-C, the plasticizer-D, the plasticizer-E, the plasticizer-F, the plasticizer-G, SumilizerGP (made by Sumitomo Chemical Co., Ltd.), TINUVIN900 (Ciba The structures of Specialty Chemicals), Sumisorb 250 (Sumitomo Chemical), and LA31 (ADEKA) are as follows.

  Evaluation similar to Example 1 was performed with respect to the produced cellulose-ester film original fabric, a cellulose-ester film, and a polarizing plate. The results are shown in Table 4.

  As mentioned above, from the results of Table 4, the cellulose ester film original fabric samples 2-1 to 2-18 of the present invention are stored for a long period of time with respect to the cellulose ester film original fabric samples 2-19 and 2-20 of the comparative examples. However, it can be seen that this is a cellulose ester film that is less susceptible to horse back failure and core transfer, and is less prone to deformation failures of the original film such as wrinkles at the beginning of winding. Further, regarding the cellulose ester film itself cut out from the raw fabric, it can be seen that the cellulose ester film of the present invention is a cellulose ester film having high flatness and suitability for saponification treatment, and having small fluctuations in curling properties and retardation. . Furthermore, it can be seen that the polarizing plate produced using the cellulose ester film of the present invention has good durability and is an optical film excellent in practical use. In addition, in film original fabric sample 2-1, film sample 2-1, and polarizing plate sample 2-1, the example compound (2) -8 is changed to the example compound (2) -3 of the same part by mass, and the same. As a result of evaluation, each of the sample Nos. The result was as good as 2-1. Similar to the above, even if Exemplified Compound (2) -8 was replaced with Exemplified Compound (2) -45 having the same parts by mass, Sample No. The result was as good as 2-1. On the other hand, in the film original fabric sample 2-5, the film sample 2-5, and the polarizing plate sample 2-5, GSY-P101 is replaced by the same part by mass of tetrakis (2,4-di-t-butyl-phenyl) -4, When the same evaluation was performed in place of 4'-biphenylenediphosphonite, each sample No. in Table 4 was tested except that the evaluation result of white spots changed from ◎ to ○. The result was as good as 2-5. Furthermore, in the film original fabric sample 2-7, the film sample 2-7, and the polarizing plate sample 2-7, IRGANOX 1010 is mixed with 1,1,1-trimethylolethane-tris- [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate] was evaluated in the same manner. The result was as good as 2-7.

Example 3
Using the cellulose ester and various additives as described below, the present invention was performed in the same manner as in Example 1 except that the extrusion amount, the take-up speed, and the draw ratio were adjusted so that the film thickness was 40 μm. When the cellulose ester film raw fabric 3-1 was prepared, it was a cellulose ester film that had little horse back failure and core transfer even when stored for a long period of time, and was less prone to deformation failure of the film original fabric such as winding wrinkles. I understood. Further, when the cellulose ester film was cut out and evaluated from this raw fabric, it was a cellulose ester film having high flatness, suitability for saponification treatment, and small fluctuation in curling property and retardation, and the cellulose ester film. It was found that the polarizing plate produced using the film has excellent durability and is an optical film excellent in practical use.

Cellulose ester 1 100 parts by weight Plasticizer-A 8 parts by weight IRGANOX 1010 (manufactured by Ciba Specialty Chemicals) 0.50 parts by weight GSY-P101 (manufactured by Sakai Chemical Industry) 0.25 parts by weight Exemplary compound (2) -8 0.30 parts by mass TINUVIN 928 (manufactured by Ciba Specialty Chemicals) 2.25 parts by mass Example 4
(Characteristic evaluation as a liquid crystal display device)
The polarizing plate of the 32-inch television AQ-32AD5 manufactured by Sharp Corporation, which is a VA type liquid crystal display device, was peeled off, and each polarizing plate prepared in Examples 1 to 3 (the cellulose ester film 3 of the present invention prepared in Example 3). -1 was used in the same manner as the polarizing plate 1-1, and the polarizing plate 3-1 was cut according to the size of the liquid crystal cell. With the liquid crystal cell sandwiched, the two polarizing plates prepared as described above were attached so that the polarizing axes of the polarizing plates were not perpendicular to each other so as to be orthogonal to each other to produce a 32-inch VA color liquid crystal display, and the polarization of the cellulose ester film When the characteristic as a board was evaluated, the liquid crystal display device using the polarizing plates 1-1 to 1-15, 2-1 to 2-18, and 3-1 of the present invention is a comparative polarizing plate 1-16 to 1. Compared with liquid crystal display devices using -25, 2-19, and 2-20, the contrast was high and excellent display properties without color unevenness were exhibited. Thereby, it was confirmed that it is excellent as a polarizing plate for image display apparatuses, such as a liquid crystal display.

Claims (11)

In an optical film obtained by heating and melting a film-forming material containing at least one plasticizer and a cellulose ester, and forming a film by a melt casting method, the type and degree of substitution of the cellulose ester are represented by the following formula (1). optical film meets ~ conditions (4) simultaneously, and the film forming material, characterized in that further contains at least one alkyl radical scavenger.
Formula (1) 1.25 ≦ X ≦ 1.43
Formula (2) 1.15 ≦ Y ≦ 1.33
Formula (3) 2.40 ≦ X + Y <2.75
Formula (4) -0.05 <= XY <0.20
[Wherein, X represents the degree of substitution with an acetyl group, and Y represents the degree of substitution with a propionyl group. ] 2. The optical film according to claim 1 , wherein a 1% mass reduction temperature Td (1.0) of the cellulose ester in air is 270 ° C. or more. The optical film according to claim 1 , wherein the film forming material further contains at least one phenolic compound. The optical film according to any one of claims 1 to 3 , wherein the film-forming material further contains at least one phosphorous compound. The optical film according to claim 3 or 4, wherein the phenolic compound is a hindered phenolic compound. The optical film according to claim 4, wherein the phosphorus compound is a phosphonite compound. The alkyl radical scavenger is a compound represented by the following general formula (1) or a compound represented by the following general formula (2), according to any one of claims 1 to 6. Optical film.
[In the formula, R ₁ Represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ₂ And R ₃ Each independently represents an alkyl group having 1 to 8 carbon atoms. ]
[In the formula, R ₁₂ ~ R ₁₅ Each independently of one another represents a hydrogen atom or a substituent, R ₁₆ Represents a hydrogen atom or a substituent, and n represents an integer of 1 to 4. When n is 1, R ₁₁ Represents a substituent, and when n is an integer of 2 to 4, R ₁₁ Represents a divalent to tetravalent linking group. ] The optical film according to any one of claims 1 to 7, wherein the plasticizer is a polyhydric alcohol ester. The optical film according to any one of claims 1 to 8, wherein the film-forming material further contains a benzotriazole-based compound. A polarizing plate having the optical film according to claim 1 on at least one surface of a polarizer. A liquid crystal display device comprising the polarizing plate according to claim 10 on at least one surface of a liquid crystal cell.