JP2012036286A - Polypropylene-based resin film and polarizing plate using the same, and liquid crystal panel and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a propylene-based resin film having excellent adhesiveness with the other resin film and a polarizing plate, and a liquid crystal panel and a liquid crystal display.SOLUTION: In the propylene-based resin film 25, a surface orientation parameter obtained by a Raman spectroscopy measurement by attenuated total reflection about at least one surface out of film surfaces lies in the range of 0.66 to 1.50. Further, the surface orientation parameter preferably lies in the range of 0.95 to 1.05. Further, the propylene-based resin film 25 can be used as a polarizing plate by laminating a polarizing film made of a uniaxially stretched polyvinyl alcohol resin film on which iodine or dichromatic dye is adsorbed and oriented on the one surface through intermediary of an adhesive layer.

Description

  The present invention relates to a polypropylene resin film, a polarizing plate using the same, a liquid crystal panel and a liquid crystal display device, and in particular, a polypropylene resin film bonded to another film via an adhesive, a polarizing plate using the same, and The present invention relates to a liquid crystal panel and a liquid crystal display device.

  A liquid crystal display device has features such as low power consumption, operation at a low voltage, and light weight and thinness. Therefore, the liquid crystal display device is used in various display devices by taking advantage of these features. In particular, the market for liquid crystal televisions is remarkably expanding, and the demand for cost reduction is also significant.

  Usually, the polarizing plate has a structure in which a transparent protective film is laminated on both sides or one side of a polarizing film made of a polyvinyl alcohol-based resin having a dichroic dye adsorbed and oriented. As the protective film, a cellulose acetate resin film typified by triacetylrose is often used. In addition, an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is often used for laminating the protective film.

  A polarizing plate in which a protective film made of triacetyl cellulose is laminated on both sides or one side of a polarizing film via an adhesive, when used for a long time under wet heat conditions, the polarizing performance is reduced, or the protective film and the polarizer are There was a problem that it was easy to peel off.

  Therefore, there is an attempt to configure at least one protective film with a resin other than cellulose acetate. For example, in a polarizing plate in which protective films are laminated on both sides of a polarizer (polarizing film), a technique is known in which at least one of the protective films is made of a propylene-based resin (see, for example, Patent Document 1). A protective film made of a propylene-based resin is excellent in wet heat resistance and dimensional stability because it has small dimensional change and moisture permeability and high resistance to organic solvents. For this reason, there exists an advantage that the adhesiveness between a polarizing film and a protective film cannot fall easily by using the protective film which consists of propylene-type resin.

  By the way, as one of indexes indicating the characteristics of the resin film, there is a degree of surface orientation (also referred to as “surface orientation parameter”). For example, a technique using a biaxially stretched polyester film having a surface orientation parameter of 1 to 3 in an image receiving paper used in a thermal transfer type printing apparatus is known (see Patent Document 2). According to this technology, by setting the surface orientation parameter within the above range, it is difficult to cause defects such as streaks and pinholes in the dye receiving layer when forming the image receiving layer, and it is possible to avoid a decrease in yield. Become.

JP 2007-334295 A JP-A-2005-350615

  As described above, it has been known that the adhesion between the protective film and the polarizing film is improved by using a polypropylene resin as the protective film. However, no studies have been conducted so far to further improve the adhesion between the protective film made of polypropylene resin and the polarizing film. In particular, the relationship between the surface orientation parameter and the adhesiveness of a polypropylene resin film has not been known so far.

  An object of the present invention is to provide a polypropylene resin film having good adhesiveness.

  Another object of the present invention is to provide a polarizing plate, a liquid crystal panel, and a liquid crystal display device that have good adhesion between the polypropylene resin film and the polarizing film and are difficult to peel off.

  As a result of intensive studies to solve the above problems, the inventors have found that the adhesiveness of the polypropylene resin film can be improved by setting the surface orientation parameter of the polypropylene resin film within a certain range. The headline and the present invention have been completed.

  That is, according to the polypropylene resin film of the present invention, the above-mentioned problem is that the surface orientation parameter obtained by Raman spectroscopy measurement by attenuated total reflection method is 0.66 to 1.50 on at least one of the film surfaces. Solved by being within range.

  In this case, the surface orientation parameter is preferably in the range of 0.95 to 1.05.

  Further, according to the polarizing plate of the present invention, the above-mentioned problem is laminated on the polarizing film through a polarizing film composed of a uniaxially stretched polyvinyl alcohol resin film in which iodine or a dichroic dye is adsorbed and oriented, and an adhesive layer. A polypropylene-based resin film according to any one of the above, wherein the polypropylene-based resin film is solved by being laminated so that the one surface is in contact with the adhesive layer. The

  In this case, it is preferable that the polarizing film further includes a protective film or an optical compensation film laminated on a surface opposite to the surface on which the polypropylene resin film is laminated.

  According to the liquid crystal panel of the present invention, the above problem is solved by including a liquid crystal cell and the polarizing plate according to any one of the above laminated on the liquid crystal cell.

  Furthermore, according to the liquid crystal display device of the present invention, the above problem is solved by including the surface light source element and the liquid crystal panel described above.

  According to the polypropylene resin film of the present invention, since the surface orientation parameter is in the range of 0.66 to 1.50, the adhesiveness with the resin film when laminated on another resin film via an adhesive. Becomes better. Moreover, according to the polarizing plate of this invention, it becomes possible to provide the polarizing plate which is hard to peel from a polarizing film by providing such a polypropylene resin film with favorable adhesiveness. Furthermore, according to the liquid crystal panel and the liquid crystal display device of the present invention, it is possible to provide a highly durable liquid crystal panel and liquid crystal display device by including such a polarizing plate that is difficult to peel off.

It is the perspective view which showed the Raman spectroscopy measuring method typically. It is a cross-sectional schematic diagram of the polarizing plate in one Embodiment of this invention. It is a cross-sectional schematic diagram of a liquid crystal panel using a polarizing plate and a liquid crystal display device. It is the cross-sectional schematic diagram which showed the manufacturing apparatus of the polarizing plate. It is the cross-sectional schematic diagram which showed the manufacturing apparatus of the polarizing plate. It is the cross-sectional schematic diagram which showed the manufacturing apparatus of the polarizing plate. 1 is a spectrum diagram of a sample of Example 1. FIG. 6 is a spectrum diagram of a sample of Comparative Example 1. FIG. It is a cross-sectional schematic diagram of the sample for a peel test. It is a top view which shows the embodiment of a peel test.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the member, arrangement | positioning, etc. which are demonstrated below, These members etc. can be suitably changed in accordance with the meaning of this invention. Hereinafter, a polarizing plate, a liquid crystal panel provided with the same, and a liquid crystal display device will be described.

<Polarizing plate>
Fig.2 (a) is drawing which shows the polarizing plate in one Embodiment of this invention, and has shown the cross-sectional schematic diagram of the polarizing plate. As shown in this figure, the polarizing plate 20 includes at least a polarizing film 21 and a polypropylene resin film 25 laminated on one surface of the polarizing film 21. The polarizing film 21 and the polypropylene resin film 25 are bonded and laminated via an adhesive layer 29.

  Furthermore, in this embodiment, it has the layer structure by which the transparent resin film 23 was laminated | stacked on the surface on the opposite side to the side by which the polypropylene resin film 25 is laminated | stacked among the surfaces of the polarizing film 21. FIG. In the present invention, the transparent resin film 23 is not an essential component.

<Liquid crystal panel and liquid crystal display device>
FIG. 3 is a schematic sectional view showing an example of a basic layer configuration of the liquid crystal panel 2 of the present invention and the liquid crystal display device 1 to which the liquid crystal panel 2 is applied. As shown in this figure, the polarizing plate 20 is bonded to the liquid crystal cell 40 and used as a component of the liquid crystal panel 2. The liquid crystal panel 2 is a constituent member of the liquid crystal display device 1. The liquid crystal panel 2 includes a liquid crystal cell 40, a polarizing plate 20 bonded to the back side of the liquid crystal cell 40, and a polarizing plate 30 bonded to the viewing side of the liquid crystal cell 40. The liquid crystal display device 1 includes a liquid crystal panel 2, a backlight 10, and a light diffusion plate 50. In the liquid crystal display device 1, the liquid crystal panel 2 is disposed so that the polarizing plate 20 is on the backlight 10 side, that is, the polypropylene resin film 25 faces the light diffusion plate 50. The polarizing plate 20 and the polarizing plate 30 are bonded to the liquid crystal cell 40 through the adhesive layer 27, respectively. Here, the back side means the backlight 10 side when the liquid crystal panel 2 is mounted on the liquid crystal display device 1. The viewing side means the side opposite to the backlight 10 when the liquid crystal panel 2 is mounted on the liquid crystal display device 1.

  The light diffusion plate 50 is a member having a function of diffusing light from the backlight 10. Examples of the light diffusing plate 50 include those obtained by dispersing particles as a light diffusing agent in a thermoplastic resin to impart light diffusibility, and those having irregularities formed on the surface of a thermoplastic resin film to impart light diffusibility. In addition, a resin composition coating layer in which particles are dispersed may be provided on the surface of a thermoplastic resin film to impart light diffusibility. The thickness of the light diffusion plate 50 can be about 0.1 to 5 mm.

  Between the light diffusing plate 50 and the liquid crystal panel 2, a sheet or film exhibiting other optical functionality such as a brightness enhancement sheet (a reflective polarizing film (such as “DBEF”)) or a light diffusing sheet is disposed. You can also Two or more sheets or films exhibiting other optical functionalities can be arranged as needed. Below, each film which comprises the polarizing plate 20 of the back side is demonstrated.

(1) Polarizing film The polarizing film 21 is a member having a function of converting natural light into linearly polarized light. As the polarizing film 21, a film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film can be used. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. As the polyvinyl acetate resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, polyvinyl acetate and Examples thereof include copolymers with other copolymerizable monomers. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of the polarizing film 21. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the thickness of a polyvinyl alcohol-type raw film is not specifically limited, For example, it is about 10-150 micrometers.

  The polarizing film 21 usually has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, and a dichroic dye It is manufactured through a step of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, uniaxial stretching can also be performed in a plurality of stages shown here. For uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which a polyvinyl alcohol-based resin film is swollen using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The stretching direction of the polyvinyl alcohol-based resin film is a direction parallel to the longitudinal direction of the long polarizing film 21. For this reason, the absorption axis of the polarizing film 21 is a direction parallel to the stretching direction of the polyvinyl alcohol-based resin film, that is, the longitudinal direction of the long polarizing film 21.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain the polarizing film 21. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment, and the polarizing film 21 is obtained. The thickness of the polarizing film 21 can be about 2-40 micrometers, for example.

(2) Polypropylene resin film The polypropylene resin film 25 is mainly composed of a polypropylene resin and has a function of protecting the polarizing film 21.

  The polypropylene resin film 25 of the present invention has an attenuated total reflection method (hereinafter referred to as “ATR”) on the surface (bonding surface) on which the polarizing film 21 is laminated via the adhesive layer 29 in the film surface. The method is characterized in that the surface orientation parameter obtained by Raman spectroscopy measurement by the “method” is in the range of 0.66 to 1.50. The polypropylene resin film 25 having such a bonding surface is excellent in adhesiveness when laminated on the polarizing film 21 via the adhesive layer 29 so that the bonding surface faces the adhesive layer 29. ing. Therefore, by using the polypropylene resin film 25 as a protective film for the polarizing plate 20, it is possible to obtain a polarizing plate having excellent adhesive strength with the polarizing film 21 and high durability. The surface orientation parameter of the surface of the polypropylene resin film 25 is more preferably in the range of 0.95 to 1.05, and ideally 1.00. As the surface orientation parameter is closer to 1.00, the molecular orientation of the surface of the polypropylene resin film 25 becomes random (non-oriented), and the adhesiveness with the polarizing film 21 becomes better. Hereinafter, the Raman spectroscopy measurement method by the ATR method is referred to as “ATR-Raman spectroscopy”.

  The surface orientation parameter can be measured using a Raman spectrophotometer. For measurement of the surface orientation parameter, first, the Raman spectrum of the surface of the polypropylene resin film 25 is measured by the ATR method. Here, the ATR method is a method in which the bonding surface of the polypropylene resin film 25 is used as a measurement surface, and this is directly adhered to a prism having a high refractive index such as high refractive index glass for spectroscopic measurement. Specifically, the incident angle of the measurement light is set larger than the critical angle so that the measurement light is totally reflected between the bonding surface of the polypropylene resin film 25 and the prism. And a measurement light is irradiated to a bonding surface, and the total reflection light reflected from the surface of a bonding surface is measured. At this time, the total reflected light is light that has penetrated slightly from the surface of the polypropylene resin film 25 and reflected. For this reason, according to ATR-Raman spectroscopy, an absorption spectrum can be obtained for a layer from the surface of the polypropylene resin film 25 to a depth of about 100 nm.

（ここで、Ｉ_１１５３は１１５３ｃｍ^−１における強度、Ｉ_１１６９は１１６９ｃｍ^−１における強度を意味する。また、「平行」は平行偏光による測定値、「垂直」は垂直偏光による測定値を意味する。） Here, the surface orientation parameter means an orientation parameter in a shallow region near the surface of the polypropylene resin film 25. The measurement of the orientation parameter is the same as the measurement of the absorption spectrum by the ATR-Raman spectroscopy described above with respect to the “parallel polarized light” parallel to the plane including the incident light and the reflected light as the measurement light and the plane including the incident light and the reflected light. This is performed by a method of irradiating vertical “vertically polarized light”. FIG. 1 is a diagram schematically showing the parallel polarized light and the vertical polarized light, where P represents the parallel polarized light and S represents the vertical polarized light. Orientation parameter of the polypropylene resin film 25 can be calculated in each of the parallel polarization and vertical polarization, the peak intensity of 1153cm ^-1 and 1169cm ^-1 which is characteristic band crystal of polypropylene, by the following equation. In addition, 1153 cm ⁻¹ is a fundamental vibration of polypropylene, which is a vibration perpendicular to the molecular chain, and 1169 cm ⁻¹ is a vibration derived from a polypropylene crystal, which indicates a vibration parallel to the molecular chain.

_{(Here, I 1153} is intensity at 1153cm _{^-1, I 1169} denotes an intensity at 1169cm ^-1. Further, "parallel" measurements by the parallel polarization, "vertical" means the value measured by vertical polarization. )

  When the surface of the polypropylene resin film 25 is non-oriented, the surface orientation parameter is 1.00. Further, when the polypropylene resin film 25 is oriented in the longitudinal direction (machine direction: MD), the surface orientation parameter shows a value larger than 1.00. On the other hand, when the polypropylene resin film 25 is oriented in the short direction (vertical direction: TD), the surface orientation parameter shows a value smaller than 1.00.

  It is not clear why the surface orientation parameter is close to the above range, particularly 1.00 and the molecular orientation of the surface is close to non-orientation, so that the adhesive force is excellent, but the polypropylene resin film 25 and the adhesive layer The mechanical strength of the film surface at the interface may affect the adhesion. That is, if the surface of the polypropylene resin film 25 is stretched in a certain direction and the molecules are oriented, the tensile strength in that direction is increased, while the tensile strength in a direction different from that is decreased. For this reason, it is thought that depending on the direction in which the polypropylene resin film 25 is pulled, cohesive failure occurs on the surface of the film and the film surface is easily peeled off. On the other hand, if the surface of the polypropylene resin film 25 is not stretched and the molecules are non-oriented, the tensile strength in any direction is high, the cohesive failure hardly occurs on the surface of the polypropylene resin film 25, and the adhesiveness is good. It is thought that it becomes.

In addition, the following multiple items are mentioned as an evaluation parameter obtained from the result by ATR-Raman spectroscopy, and the item which can be evaluated from it.
(1) Evaluation item: Orientation ... Evaluation parameter: Peak intensity (2) Evaluation item: Order ... Evaluation parameter: Half width of peak (3) Evaluation item: Conformation ... Evaluation parameter: Wave number position (4) Evaluation item: Crystallinity: Evaluation parameter: Peak intensity ratio Among these, the orientation of (1) is an item related to adhesiveness as described above, but the order of (2) And (3) conformation can also be measured. On the other hand, the crystallinity of (4) cannot be evaluated because measurement in the range of 808 to 840 cm ⁻¹ cannot be performed due to restrictions on the apparatus. The present invention focuses on the orientation of (1) among the above (1) to (4), and is characterized in that the adhesiveness is good if the surface orientation parameter is within a predetermined range. .

In this invention, since the protective film laminated | stacked on the polarizing film 21 is a polypropylene resin film, there exist the following advantages. Polypropylene resin has a small photoelastic coefficient of about 2 × 10 ⁻¹³ cm ² / dyne and low moisture permeability. Therefore, by applying the polarizing plate 20 including the polypropylene resin film 25 to the liquid crystal cell 40 The liquid crystal display device 1 having excellent durability under wet heat conditions can be obtained. Furthermore, the adhesiveness of the polypropylene resin film 20 to the polarizing film 21 is good if not as high as that of the triacetylcellulose film, and the polypropylene resin film 25 has sufficient strength when various known adhesives are used. Can be adhered to the polarizing film 21.

  The polypropylene resin may be composed of a propylene homopolymer, or may be a copolymer of propylene as a main component and a small amount of a comonomer copolymerizable therewith. The polypropylene resin comprising a copolymer can be a resin containing a comonomer unit in a range of, for example, 20% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less. Further, the content of the comonomer unit in the copolymer is preferably 1% by weight or more, more preferably 3% by weight or more. By setting the content of the comonomer unit to 1% by weight or more, processability and transparency can be significantly improved. On the other hand, when the content of the comonomer unit exceeds 20% by weight, the melting point of the polypropylene resin is lowered and the heat resistance tends to be lowered. In addition, when setting it as the copolymer of 2 or more types of comonomer, and propylene, it is preferable that the total content of the unit derived from all the comonomer contained in the copolymer is the said range.

  The comonomer copolymerized with propylene may be, for example, ethylene or an α-olefin having 4 to 20 carbon atoms. Specific examples of the α-olefin include the following.

1-butene, 2-methyl-1-propene (above C ₄ );
1-pentene, 2-methyl-1-butene, 3-methyl-1-butene (above C ₅ );
1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3- Dimethyl-1-butene (above C ₆ );
1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene (above C ₇ );
1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4-trimethyl- 1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene (above C ₈ );
1-nonene (C ₉ ); 1-decene (C ₁₀ ); 1-undecene (C ₁₁ );
1-dodecene (C ₁₂ ); 1-tridecene (C ₁₃ ); 1-tetradecene (C ₁₄ );
1-pentadecene (C ₁₅ ); 1-hexadecene (C ₁₆ ); 1-heptadecene (C ₁₇ );
1-octadecene (C ₁₈ ); 1-nonadecene (C ₁₉ ) and the like.

  Among the α-olefins, α-olefins having 4 to 12 carbon atoms are preferable. Specifically, 1-butene, 2-methyl-1-propene; 1-pentene, 2-methyl-1-butene, 3 -Methyl-1-butene; 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1 -Pentene, 3,3-dimethyl-1-butene; 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl -1-butene; 1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3 , 4-Trimethyl-1-pentene 2-propyl-1-pentene, 2,3-diethyl-1-butene; 1-nonene; 1-decene; 1-undecene; 1-dodecene, and the like. From the viewpoint of copolymerizability, 1-butene, 1-pentene, 1-hexene and 1-octene are preferable, and 1-butene and 1-hexene are more preferable.

  The copolymer may be a random copolymer or a block copolymer. Preferred copolymers include propylene / ethylene copolymers and propylene / 1-butene copolymers. In the propylene / ethylene copolymer and the propylene / 1-butene copolymer, the content of the ethylene unit and the content of the 1-butene unit are, for example, those of “Polymer Analysis Handbook” (1995, published by Kinokuniya Shoten) Infrared (IR) spectrum measurement can be performed by the method described on page 616.

  From the viewpoint of improving the transparency and workability of the polypropylene resin film 25 bonded to the polarizing film 21, the copolymer is a random copolymer of propylene mainly composed of propylene and ethylene or the α-olefin. It is preferable that it is a random copolymer of propylene and ethylene. As described above, the content of the ethylene unit in the propylene / ethylene random copolymer is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, and 3 to 7% by weight. Is more preferable.

  The stereoregularity of the polypropylene resin may be any of isotactic, syndiotactic, and atactic. In the present invention, a syndiotactic or isotactic polypropylene resin is preferably used from the viewpoint of heat resistance.

  The polypropylene resin preferably has a melt flow rate (MFR) measured in a temperature of 230 ° C. and a load of 21.18 N within a range of 0.1 to 200 g / 10 minutes in accordance with JIS K 7210. More preferably, it is in the range of 5 to 50 g / 10 min. By using a polypropylene resin having an MFR within this range, a uniform polypropylene resin film 25 can be obtained without imposing a large load on the extruder.

The polypropylene resin can be produced by a method of homopolymerizing propylene using a known polymerization catalyst or a method of copolymerizing propylene and another copolymerizable comonomer. Examples of known polymerization catalysts include the following. (1) Ti—Mg-based catalyst comprising a solid catalyst component containing magnesium, titanium and halogen as essential components,
(2) a catalyst system in which a solid catalyst component containing magnesium, titanium and halogen as essential components is combined with an organoaluminum compound and, if necessary, a third component such as an electron donating compound,
(3) Metallocene catalysts.

  Among these catalyst systems, the catalyst system of the above (2) can be used most generally in the production of polypropylene resins. Preferred examples of the organoaluminum compound in the catalyst system of the above (2) include triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride, tetraethyldialumoxane, etc. Preferred examples of the electron donating compound Examples thereof include cyclohexylethyldimethoxysilane, tert-butylpropyldimethoxysilane, tert-butylethyldimethoxysilane, and dicyclopentyldimethoxysilane.

  Examples of the solid catalyst component (1) and (2) include catalyst systems described in JP-A-61-218606, JP-A-61-287904, JP-A-7-216017, and the like. It is done. Examples of the metallocene catalyst (3) include catalyst systems described in Japanese Patent No. 2587251, Japanese Patent No. 2627669, Japanese Patent No. 2668732, and the like.

  Polypropylene resin is, for example, a solution polymerization method using an inert solvent typified by a hydrocarbon compound such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, and a liquid monomer as a solvent. It can be produced by a bulk polymerization method to be used or a gas phase polymerization method in which a gaseous monomer is polymerized as it is. Polymerization by these methods may be carried out batchwise or continuously.

  A well-known additive may be mix | blended with the polypropylene resin. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, and an antiblocking agent. Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine light stabilizers, and the like, and for example, phenolic antioxidant mechanisms in one molecule. It is also possible to use a composite antioxidant having a unit having both a phosphorus-based antioxidant mechanism and a phosphorus-based antioxidant mechanism. Examples of the UV absorber include UV absorbers such as 2-hydroxybenzophenone and hydroxyphenylbenzotriazole, and benzoate UV blockers. The antistatic agent may be polymer type, oligomer type or monomer type. Examples of the lubricant include higher fatty acid amides such as erucic acid amide and oleic acid amide, higher fatty acids such as stearic acid, and salts thereof. Examples of the nucleating agent include a sorbitol nucleating agent, an organic phosphate nucleating agent, and a polymer nucleating agent such as polyvinylcycloalkane. As the anti-blocking agent, fine particles having a spherical shape or a shape close thereto can be used regardless of inorganic type or organic type. As for said additive, multiple types may be used together.

  The polypropylene resin can be formed into a polypropylene resin film 25 by film formation by an arbitrary method. The polypropylene resin film 25 is preferably transparent and has substantially no in-plane retardation. For example, polypropylene that has substantially no in-plane retardation by extrusion molding from a molten resin or solvent casting that casts a resin dissolved in an organic solvent on a flat plate and removes the solvent to form a film. The resin film 25 can be obtained.

  The thickness of the polypropylene resin film 25 is usually 20 to 200 μm, preferably 20 to 120 μm. When the thickness of the polypropylene resin film 25 is less than 20 μm, the handling properties tend to be inferior, and even when the thickness exceeds 200 μm, the handling properties may be lowered due to the increased rigidity of the film.

The polypropylene resin film 25 needs to be excellent in transparency. Specifically, the haze value measured according to JIS K 7361 is 10% or less, preferably 7% or less. When the haze value exceeds 10%, when the obtained polarizing plate 20 is applied to the liquid crystal display device 1, the white luminance is lowered and the screen tends to be dark. The haze value measured according to JIS K 7361 is the following formula:
(Diffuse transmittance / total light transmittance) × 100 (%)
Defined by

  The surface of the polypropylene resin film 25 opposite to the polarizing film 21 may be formed into a prism or lens shape by shaping and may be used as a light collecting film. FIG. 2B shows a polarizing plate 60 provided with a condensing film 65. The condensing film 65 is a member that has a function of improving the luminance of condensing the light emitted from the backlight 10 onto the liquid crystal cell 40 and also has a protective function of protecting the polarizing film 21. The condensing film 65 changes the angle of the light emitted obliquely from the backlight 10 at the slope portion of the prism shape or lens shape and reflects it toward the liquid crystal cell 40, thereby condensing it on the liquid crystal cell 40.

  Examples of a method for forming a prism shape or a lens shape on the surface of the polypropylene resin film 25 include a method of thermally transferring a prism shape or a lens shape to a thermoplastic resin, or an active energy ray curable resin that is cured by ultraviolet rays or the like into a resin film shape. And a method of shaping a prism shape or a lens shape.

  In addition, the surface of the polypropylene resin film 25 opposite to the polarizing film 21 may be subjected to a hard coat treatment from the viewpoint of preventing scratches in the manufacturing process of the liquid crystal panel 2 and the liquid crystal display device 1 using the same. . Further, from the viewpoint of reducing moire due to interference between the prism sheet and the color filter, anti-glare processing may be performed.

  Further, a protective film or an adhesive layer may be laminated on the surface of the polypropylene resin film 25 opposite to the polarizing film 21. Furthermore, an optical film such as a reflective polarizing film as exemplified in the “DBEF series” sold by 3M Company may be provided through the adhesive layer.

(3) Transparent resin film The transparent resin film 23 is a film that is bonded to the surface of the polarizing film 21, and employs films having various properties depending on the characteristics required for the liquid crystal panel 2 and the liquid crystal display device 1. can do. As an example of the transparent resin film 23, for example, a protective film for protecting the surface of the polarizing film 21, a retardation film for solving the problem of viewing angle characteristics of the liquid crystal display device 1, and the like can be employed. As the protective film, for example, a non-oriented film having a haze value of 0.5% or less and an in-plane retardation value of less than 30 nm can be employed. As the retardation film, a biaxial retardation film having an in-plane retardation value in the range of 30 to 200 nm and a thickness direction retardation value in the range of 30 to 350 nm can be employed. The in-plane retardation value R ₀ and the thickness direction retardation value R _th here are values at a wavelength of 590 nm, and so on.

  The transparent resin film 23 preferably has a Gurley method bending resistance measured in accordance with JIS L 1096 of 350 mgf or less, more preferably 200 mgf or less, and even more preferably 150 mgf or less. Thus, since the rigidity of the obtained polarizing plate 20 is reduced by using the transparent resin film 23 with a low bending resistance, the handling property at the time of bonding to the liquid crystal cell 40 can be improved.

  The resin material which comprises the transparent resin film 23 is not specifically limited. Examples of such resin materials include (meth) acrylic resins such as methyl methacrylate resins ((meth) acrylic resins mean methacrylic resins or acrylic resins), olefin resins, poly Vinyl chloride resin, cellulose resin, styrene resin, acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin Polycarbonate resin, modified polyphenylene ether resin, polyester resin (for example, polybutylene terephthalate resin, polyethylene terephthalate resin, etc.), polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, Polyimide resins, epoxy resins, and oxetane-based resin. These resins can contain additives as long as transparency and adhesiveness with the polarizing film 21 are not impaired.

(3-1) Optical Compensation Film As the transparent resin film 23, an optical compensation film can be adopted as described above. Examples of such an optical compensation film include a retardation film obtained by stretching the unstretched film made of the resin material described above to develop a retardation, and forming a transparent resin film 23. In addition, there is a method of forming a retardation film by applying an orientation material such as liquid crystal to a base material and orienting it to develop a phase difference and fixing it (for example, JP-A-2004-272202). A method for forming an optically anisotropic layer containing a rod-like liquid crystalline compound on a transparent support, as described in Example 4 of the publication or Example 3 of JP-A-2004-233872. In particular, those in which biaxial birefringence is expressed by successive biaxial stretching are preferred. The stretching ratio at this time is approximately 1.1 to 10 times in the direction in which the optical axis is expressed (the direction in which the stretching ratio is large and the slow axis) among the longitudinal direction and the transverse direction, and is orthogonal to that. What is necessary is just to select suitably from the range of about 1.1-7 times by the direction (direction where a draw ratio is small, and becomes a fast axis) according to the required phase difference value. The optical axis may be developed in the lateral direction of the film, or the optical axis may be developed in the longitudinal direction. Examples of commercially available cellulose acetate-based resin films imparted with such retardation characteristics include KC4FR-1 (manufactured by Konica Minolta Opto) and KC4HR-1 (manufactured by Konica Minolta Opto).

Next, the retardation value of the transparent resin film 23 will be described. The refractive index of in-plane slow axis direction n _x of the _film, the refractive index n _y in-plane fast axis direction (direction orthogonal with the slow axis and the _plane), the refractive index in the thickness direction n _z, thickness Where d is the in-plane retardation value R ₀ and the thickness direction retardation value R _th are defined by the following equations (I) and (II), respectively.

_{R 0 = (n x -n y} ) × d (I)
R _th = [(n _x + _ny ) / 2−n _z ] × d (II)

Further, the transparent resin film 23 has the following formula (III):
_nx > _ny > _nz (III)
It satisfies the relationship.

In the present invention, the transparent resin film 23 having an in-plane retardation value R ₀ in the range of 30 to 200 nm and a thickness direction retardation value R _th in the range of 30 to 350 nm is used. The phase difference value may be appropriately selected according to the characteristics required for the applied liquid crystal display device 1. The in-plane retardation value R ₀ is preferably 100 nm or less, and the thickness direction retardation value R _th is preferably 80 nm or more and 200 nm or less.

The accuracy of the in-plane retardation value R ₀ is within the center value ± 7 nm, preferably within the center value ± 5 nm, and the accuracy of the thickness direction retardation value R _th is within the center value ± 15 nm, preferably the center value ± 10 nm. Is within. If the accuracy of these values exceeds the above range, the visual characteristics of the applied liquid crystal display device 1 tend to deteriorate.

  The slow axis angle in the film plane of the transparent resin film 23 is substantially 0 ° or 90 °. If the slow axis deviates from this angle, light leakage occurs when the polarizing plate 20 and the polarizing plate 30 are in a crossed Nicol state, and when applied to the liquid crystal display device 1, visual characteristics such as front contrast are greatly increased. It tends to decrease. The accuracy of the slow axis is preferably within the center value ± 0.7 °, and more preferably within the center value ± 0.5 °. Here, the light leakage means that when the axial accuracy of the polarizing film 21 with respect to the biaxial retardation film 23 or the axial accuracy of the polarizing plate 20 with respect to the liquid crystal cell 40 is poor, the liquid crystal display device 1 starts from the entire display area when displaying black. A phenomenon in which light leaks. As described above, the shift of the slow axis in the transparent resin film 23 is reduced, and accordingly, the shift of the angle between the slow axis and the absorption axis of the polarizing film 21 is also reduced. Light leakage can be reduced by increasing the axial accuracy of the polarizing plates to be bonded (polarizing plate 20 and polarizing plate 30) and by reducing the deviation from 90 ° of the angle formed by the absorption axes of both polarizing plates. .

  In adhering the transparent resin film 23 to the polarizing film 21, the optimum axial relationship between them may be selected in consideration of the viewing angle characteristics and color change characteristics of the target liquid crystal display device 1. In large liquid crystal television applications where front contrast is important, the slow axis of the transparent resin film 23 and the absorption axis of the polarizing film 21 are often arranged in a substantially parallel or substantially orthogonal relationship. Here, “substantially parallel or substantially orthogonal” includes not only the case of being completely parallel or orthogonal but also the case of deviation from the parallel or orthogonal relationship within a range of about ± 10 °. The angle deviation is preferably within ± 5 °, more preferably within ± 2 °. The slow axis of the transparent resin film 23 and the absorption axis of the polarizing film 21 are preferably in a completely parallel or orthogonal relationship.

(3-2) Protective Film As the transparent resin film 23, a protective film can be adopted as described above. As such a protective film, a non-oriented film having substantially no retardation in the plane or thickness direction can be employed. The non-oriented film means an unstretched resin film (unstretched film) obtained by forming a resin material into a film.

  Since the non-oriented film has no retardation, it does not have the function of widening the viewing angle of the liquid crystal display device 1 like the biaxial retardation film. However, the non-oriented film is stretched like the biaxial retardation film. The manufacturing cost is low because it is not necessary to do so. Therefore, compared with the case where a biaxial retardation film is adopted as the transparent resin film 23, the manufacturing cost of the liquid crystal display device 1 can be further reduced.

  Moreover, since a non-oriented film does not perform a extending | stretching process and a film thickness becomes thick, the handleability of the transparent resin film 23 becomes favorable. Such a transparent resin film 23 can be obtained from an unstretched film (raw film) obtained by forming the resin composition.

  The resin material mentioned above is formed into an unstretched film by any method. This unstretched film is preferably transparent and substantially free of in-plane retardation. Examples of the film forming method include an extrusion method in which a molten resin is extruded to form a film, and a solvent cast method in which a solvent dissolved in an organic solvent is cast on a flat plate and then the solvent is removed to form a film. Etc. can be adopted.

From the viewpoint of the retardation value _{Rth in} the thickness direction, it is preferable that the transparent resin film 23 is thinner because the retardation value can be reduced. Specifically, the transparent resin film 23 preferably has a thickness of 15 to 45 μm. Considering not only the handling property of the polarizing plate 20 but also the handling property of the transparent resin film 23 itself, a film having a thickness of 35 to 45 μm is more preferable.

(4) Adhesive layer Bonding and lamination of the polypropylene resin film 25 and the transparent resin film 23 to the polarizing film 21 are usually performed via the adhesive layer 29. The adhesive forming the adhesive layer 29 provided on both surfaces of the polarizing film 21 may be the same or different.

  As the adhesive, an adhesive having an epoxy resin, urethane resin, cyanoacrylate resin, acrylamide resin, or the like as an adhesive component can be used. One of the adhesives preferably used in the present invention is a solventless adhesive. Solventless adhesives do not contain a significant amount of solvent, and are curable compounds (monomers or oligomers) that are reactively cured by heating or irradiation with active energy rays (for example, ultraviolet rays, visible light, electron beams, X-rays, etc.) ), And an adhesive layer is formed by curing of the curable compound, and typically includes a curable compound that is reactively cured by heating or irradiation of active energy rays, and a polymerization initiator. In particular, as described above, since the polypropylene resin film 25 has low moisture permeability, water drainage is poor when an aqueous adhesive described later is used, and the polarizing film 21 is damaged or the polarization performance is deteriorated due to moisture in the adhesive. There is a case. Therefore, when bonding such a resin film with low moisture permeability, a solventless adhesive is preferable.

  As an example of a preferable adhesive for forming the adhesive layer 29 from the viewpoint of rapid curing and productivity improvement of the polarizing plate 20 associated therewith, an active energy ray-curable adhesive that is cured by irradiation with active energy rays is exemplified. Can do. As an example of such an active energy ray-curable adhesive, for example, a photo-curable adhesive that is cured by light energy such as ultraviolet light and visible light can be cited. The photocurable adhesive is preferably one that is cured by cationic polymerization from the viewpoint of reactivity. In particular, the solvent-free epoxy adhesive that uses an epoxy compound as the curable compound includes the polarizing film 21 and the propylene resin. Since it is excellent in adhesiveness with the film 25 and the transparent resin film 23, it is more preferable.

  The epoxy compound, which is a curable compound contained in the solventless epoxy adhesive, is not particularly limited, but is preferably one that is cured by cationic polymerization, and particularly from the viewpoint of weather resistance, refractive index, and the like. It is more preferable to use an epoxy compound that does not contain an aromatic ring. Examples of such epoxy compounds that do not contain an aromatic ring in the molecule include hydrides of aromatic epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. In addition, the epoxy compound that is a curable compound usually has two or more epoxy groups in the molecule.

  First, the hydride of an aromatic epoxy compound will be described. The hydride of an aromatic epoxy compound can be obtained by selectively hydrogenating an aromatic epoxy compound to an aromatic ring under pressure in the presence of a catalyst. Examples of aromatic epoxy compounds include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; phenol novolac epoxy resins, cresol novolac epoxy resins, hydroxybenzaldehyde Examples include novolak-type epoxy resins such as phenol novolac epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol. Especially, it is preferable to use the glycidyl ether of hydrogenated bisphenol A as a hydride of an aromatic epoxy compound.

Next, the alicyclic epoxy compound will be described. An alicyclic epoxy compound means an epoxy compound having one or more epoxy groups bonded to an alicyclic ring, and “having one or more epoxy groups bonded to an alicyclic ring” is represented by the following formula: Means having the structure shown. In formula, m is an integer of 2-5.

Therefore, the alicyclic epoxy compound is a compound having at least one structure represented by the above formula and having a total of two or more epoxy groups in the molecule. More specifically, a compound in which a group in a form in which one or a plurality of hydrogen atoms in (CH ₂ ) _m in the above formula are removed is bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among such alicyclic epoxy compounds, an epoxy compound having an epoxycyclopentane ring (m = 3 in the above formula) or an epoxycyclohexane ring (m = 4 in the above formula) has high adhesion strength. It is more preferably used because an excellent adhesive can be obtained. Although the structure of an alicyclic epoxy compound is specifically illustrated below, it is not limited to these compounds.

  3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, ethylenebis (3,4-epoxycyclohexanecarboxyl Rate), bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, diethylene glycol bis (3,4-epoxycyclohexylmethyl ether), ethylene glycol bis (3 4-epoxycyclohexyl methyl ether), 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro- [5.2.2.5.2.2] henicosane (this compound is 3,4- Poxycyclohexanespiro-2 ′, 6′-dioxanespiro-3 ″, 5 ″ -dioxanespiro-3 ″ ″, 4 ″ ″-a compound that can also be named as epoxycyclohexane), 4- (3,4 -Epoxycyclohexyl) -2,6-dioxa-8,9-epoxyspiro [5.5] undecane, 4-vinylcyclohexene dioxide, bis-2,3-epoxycyclopentyl ether, dicyclopentadiene dioxide and the like.

  Examples of the aliphatic epoxy compound include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. More specifically, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene Polyethers of polyether polyols obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as glycol diglycidyl ether, ethylene glycol, propylene glycol, and glycerin Examples thereof include glycidyl ether.

  In this invention, an epoxy compound may be used individually by 1 type, or may use 2 or more types together.

  The epoxy equivalent of the epoxy compound contained in the solventless epoxy adhesive is usually in the range of 30 to 3,000 g / equivalent, preferably 50 to 1,500 g / equivalent. When the epoxy equivalent is less than 30 g / equivalent, the flexibility of the protective film after curing may be lowered, or the adhesive strength may be reduced. On the other hand, if the epoxy equivalent exceeds 3,000 g / equivalent, the compatibility with other components contained in the epoxy adhesive may be lowered.

  The solventless epoxy adhesive preferably contains a cationic polymerization initiator in order to cationically polymerize the epoxy compound. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, or heating, and initiates an epoxy group polymerization reaction. In the present invention, any type of cationic polymerization initiator may be used. However, it is preferable from the viewpoint of workability that the potential is imparted. In the following, a cationic polymerization initiator that generates a cationic species or a Lewis acid by irradiation of active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams and initiates a polymerization reaction of an epoxy group is referred to as “photocation polymerization initiation”. Also referred to as “agent”.

  When the cationic photopolymerization initiator is used, the adhesive component can be cured at room temperature. Therefore, the need to consider the heat resistance of the polarizing film 21 or distortion due to expansion is reduced, and the polypropylene resin film 25 and the transparent resin film are reduced. 23 can be bonded onto the polarizing film 21 with good adhesion. In addition, when a cationic photopolymerization initiator is used, it acts catalytically by light, so that it is excellent in storage stability and workability even when mixed with an epoxy adhesive.

  Although it does not specifically limit as a photocationic polymerization initiator, For example, aromatic diazonium salt, aromatic iodonium salt, onium salts, such as an aromatic sulfonium salt, an iron- allene complex, etc. can be mentioned. These cationic photopolymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

  These photocationic polymerization initiators can be easily obtained as commercial products. For example, “Kayarad PCI-220” and “Kayarad PCI-620” (Nippon Kayaku Co., Ltd. )), “UVI-6990” (manufactured by Union Carbide), “Adekaoptomer SP-150”, “Adekaoptomer SP-170” (manufactured by ADEKA, Inc.), “CI-5102”, “ "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S" (Nippon Soda Co., Ltd.), "DPI-101", "DPI-102" , “DPI-103”, “DPI-105”, “MPI-103”, “MPI-105”, “BBI-101”, “BBI-102”, “BB -103 "," BBI-105 "," TPS-101 "," TPS-102 "," TPS-103 "," TPS-105 "," MDS-103 "," MDS-105 "," DTS-102 " ", DTS-103" (manufactured by Midori Chemical Co., Ltd.), "PI-2074" (manufactured by Rhodia), and the like.

  The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably it is 15 weight part or less.

  The solventless epoxy adhesive may further contain a photosensitizer as necessary together with the photocationic polymerization initiator. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. When mix | blending a photosensitizer, the quantity is about 0.1-20 weight part with respect to 100 weight part of epoxy compounds.

  In addition, as a thermal cationic polymerization initiator that generates a cationic species or a Lewis acid by heating and initiates a polymerization reaction of an epoxy group, for example, benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium Examples thereof include salts, carboxylic acid esters, sulfonic acid esters, and amine imides. These thermal cationic polymerization initiators can also be easily obtained as commercial products. For example, “Adeka Opton CP77”, “Adeka Opton CP66” (manufactured by ADEKA Corporation), “CI-” 2639 "," CI-2624 "(manufactured by Nippon Soda Co., Ltd.)," Sun-Aid SI-60L "," Sun-Aid SI-80L "," Sun-Aid SI-100L "(manufactured by Sanshin Chemical Industry Co., Ltd.) ) And the like. These thermal cationic polymerization initiators may be used alone or in admixture of two or more. Moreover, it is also preferable to use photocationic polymerization initiator heat and a cationic polymerization initiator together.

  The solventless epoxy adhesive may further contain a compound that promotes cationic polymerization, such as oxetanes and polyols.

  In the case of using a solventless type epoxy adhesive, the polarizing film 21 and the polypropylene resin film 25 or the transparent resin film 23 are bonded to the adhesive surface of the polarizing film 21 or the polypropylene resin film 25, the polarizing film 21 or the like. It can be performed by applying an adhesive to the application surface of the transparent resin film 23 and bonding the respective films together. There is no particular limitation on the method of applying the solventless epoxy adhesive to the polarizing film 21, the polypropylene resin film 25, and the transparent resin film 23. For example, doctor blade, wire bar, die coater, comma coater, gravure Various coating methods such as a coater can be used. Moreover, since each coating method has an optimum viscosity range, the viscosity may be adjusted using a small amount of solvent. The solvent used for this is not particularly limited as long as it can dissolve the epoxy adhesive well without deteriorating the optical performance of the polarizing film 21. For example, hydrocarbons typified by toluene and ethyl acetate are typical. Organic solvents such as esters can be used.

  After bonding the polypropylene resin film 25 and the transparent resin film 23 to the polarizing film 21 through an adhesive layer made of an uncured epoxy adhesive, by irradiating active energy rays or heating, The adhesive layer is cured, and the polypropylene resin film 25, the transparent resin film, or the transparent resin film 23 is fixed on the polarizing film 21. In the case of curing by irradiation with active energy rays, ultraviolet rays are preferably used. Specific examples of the ultraviolet light source include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a black light lamp, and a metal halide lamp. The irradiation intensity and irradiation amount of active energy rays such as ultraviolet rays are appropriately selected so as to sufficiently activate the cationic polymerization initiator and not adversely affect the cured adhesive layer, the polarizing film 21 and the like. . In addition, when cured by heating, it can be heated by a generally known method, and the temperature and time at that time can sufficiently activate the cationic polymerization initiator, and the cured adhesive layer or It is appropriately selected so as not to adversely affect the film such as the polarizing film 21.

  The thickness of the adhesive layer comprising the cured epoxy adhesive obtained as described above is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and usually 1 μm or more.

  Further, from the viewpoint of thinning the adhesive layer 29, an aqueous adhesive, that is, an adhesive in which an adhesive component is dissolved in water or an adhesive component is dispersed in water can be used as the adhesive. For example, an aqueous composition using a polyvinyl alcohol resin or a urethane resin as a main component can be mentioned as a preferred aqueous adhesive.

  Polyvinyl alcohol resins as the main component of the adhesive include partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified polyvinyl alcohol. It may be a modified polyvinyl alcohol resin such as alcohol. An aqueous adhesive whose main component is an polyvinyl alcohol resin is often prepared as an aqueous solution of a polyvinyl alcohol resin. The density | concentration of the polyvinyl alcohol-type resin in a water-system adhesive agent is about 1-10 weight part normally with respect to 100 weight part of water, Preferably it is 1-5 weight part.

  In order to improve the adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to an aqueous adhesive containing a polyvinyl alcohol resin as a main component. Examples of water-soluble epoxy resins include polyamides obtained by reacting epichlorohydrin with polyamide polyamines obtained by reacting polyalkylene polyamines such as diethylenetriamine and triethylenetetramine with dicarboxylic acids such as adipic acid. Mention may be made of polyamine epoxy resins. Commercially available products of such polyamide polyamine epoxy resins include “Smiles Resin 650” and “Smiles Resin 675” sold by Sumika Chemtex Co., Ltd., and “WS-525” sold by Japan PMC Co., Ltd. Etc., and these can be preferably used. The addition amount of these curable components or crosslinking agents is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. If the addition amount is small, the effect of improving the adhesiveness is reduced, while if the addition amount is large, the adhesive layer 29 tends to become brittle.

  When a urethane resin is used as the main component of the adhesive, examples of suitable water-based adhesives include a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. The polyester-based ionomer type urethane resin here is a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer-type urethane resin is suitable as a water-based adhesive because it is emulsified directly into water without using an emulsifier and becomes an emulsion. Polyester ionomer urethane resins are known per se. For example, Japanese Patent Application Laid-Open No. 7-97504 describes a polyester ionomer type urethane resin as an example of a polymer dispersant for dispersing a phenolic resin in an aqueous medium, and Japanese Patent Application Laid-Open No. 2005-070140. In JP-A-2005-181817, a cycloolefin-based resin film is bonded to a polarizing film made of a polyvinyl alcohol-based resin using a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group as an adhesive. The form is shown.

  As a method of bonding the polypropylene resin film 25 and the transparent resin film 23 to the surface of the polarizing film 21 using an adhesive, a conventionally known method can be used. For example, the polarizing film 21 and / or the film to be bonded to it by the casting method, Meyer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method, dip coating method, spraying method, etc. The method of apply | coating an adhesive agent to a surface and superimposing both is mentioned. The casting method is a method of spreading and spreading an adhesive on the surface of a film to be coated while moving the film in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two.

  After apply | coating an adhesive agent by the said method, both are joined by pinching | interposing the polarizing film 21 and the film bonded by it with a nip roll. Moreover, after dripping an adhesive agent between the polarizing film 21 and the film bonded to it, the method of pressing this laminated body with a roll etc. and spreading it uniformly can also be used suitably. In this case, a metal, rubber, or the like can be used as the material of the roll. Furthermore, after dropping an adhesive agent between the polarizing film 21 and the film bonded thereto, a method of passing the laminate between the rolls and pressurizing and spreading is preferably employed. In this case, these rolls may be made of the same material or different materials.

  Note that the thickness of the adhesive layer 29 after being bonded using a nip roll or the like before drying or curing is preferably 5 μm or less, and more preferably 0.01 μm or more.

  In order to improve the adhesiveness, the polarizing film 21 and / or the adhesive surface of the film bonded thereto are subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. You may give suitably. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  The laminated body joined through the water-based adhesive is usually subjected to a drying treatment, and the adhesive layer 29 is dried and cured. The drying process can be performed, for example, by blowing hot air. A drying temperature is normally selected from the range of about 40-100 degreeC, Preferably it is 60-100 degreeC. The drying time is, for example, about 20 to 1,200 seconds. The thickness of the adhesive layer 29 after drying is usually about 0.001 to 5 μm, preferably 0.01 μm or more, preferably 2 μm or less, more preferably 1 μm or less. If the thickness of the adhesive layer 29 is too large, the appearance of the polarizing plate 20 tends to be poor.

  After the drying treatment, sufficient adhesive strength may be obtained by performing curing at a temperature of room temperature or higher for at least half a day, usually 1 day or longer. Such curing is typically performed in a state of being wound into a roll. The preferable curing temperature is in the range of 30 to 50 ° C, more preferably 35 ° C or more and 45 ° C or less. When the curing temperature exceeds 50 ° C., so-called “roll tightening” is likely to occur in the roll winding state. The humidity during curing is not particularly limited, but is preferably selected so that the relative humidity is in the range of about 0% RH to 70% RH. The curing time is preferably about 1 to 10 days, more preferably about 2 to 7 days.

  On the other hand, when the polarizing film 21 and the film bonded thereto are bonded using a photocurable adhesive, the photocurable adhesive is cured by irradiating active energy rays after these films are bonded. Let The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excited mercury lamp, a metal halide lamp, or the like is preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW. / Cm ² is preferable. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the heat is radiated from the light source and the heat generated when the photocurable adhesive is cured. There is little possibility of causing yellowing of the photocurable epoxy resin and deterioration of the polarizing film 21. The light irradiation time to the photocurable adhesive is controlled for each photocurable adhesive to be cured and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is It is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained. The thickness of the adhesive layer 29 after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 μm or more, and more preferably 0.1 μm or more.

  When the photocurable adhesive is cured by irradiation with active energy rays, various functions of the polarizing plate 20 such as the degree of polarization of the polarizing film 21, the transmittance and the hue, and the transparency of the transparent resin film 23 and the polypropylene resin film 25. It is preferable to perform the curing under the condition that does not decrease.

<Production method of polarizing plate>
4-6 is the schematic which shows the example of the film manufacturing apparatus which can be used suitably for manufacture of the polypropylene resin film 25 of this invention. Hereinafter, the configuration of a film manufacturing apparatus that can be suitably used for manufacturing the polypropylene resin film 25 of the present invention and a method for manufacturing the polypropylene resin film 25 using the same will be described with reference to FIGS. To do.

(Extruder)
In the production of the polypropylene resin film 25 using the film production apparatus 100 shown in FIG. 4 (the same applies to the film production apparatuses 200 and 300 shown in FIGS. 5 and 6), first, from a hopper (not shown). The polypropylene resin is put into the extruder 11. At this time, in order to suppress deterioration / decomposition of the polypropylene resin during kneading, before supplying the resin to the extruder 11, the polypropylene is heated at a temperature of 40 ° C. or more and (Tm−20 ° C.) or less in nitrogen gas. It is preferable to pre-dry the pellets of the system resin for about 1 hour to 10 hours (Tm [° C.] is the melting peak temperature of the polypropylene resin in the differential scanning calorimetry specified by JIS K 7121). In addition, it is preferable that the inside of the extruder 11 be replaced with an inert gas such as nitrogen gas or argon gas at 20 ° C to 120 ° C. The extruder 11 is an apparatus that extrudes the supplied polypropylene resin while melting and kneading it, and conveys the molten polypropylene resin to the T-die 12.

  When melt-kneading the polypropylene resin in the extruder 11, a screw is used. As the screw, when the extruder 11 is a single screw extruder, L / D = 24 to 36 and a compression ratio of 1. A type having 5 to 4 full flight type, barrier type, or Maddock type kneading portions can be used. From the viewpoint of suppressing deterioration and decomposition of the polypropylene resin and uniformly melting and kneading, it is preferable to use a barrier type screw having L / D = 28 to 36 and a compression ratio of 2.5 to 3.5.

  Further, in order to remove volatile gas generated when the polypropylene resin is deteriorated or decomposed, it is also preferable to provide an orifice of 1 mm or more and 5 mmφ or less at the tip of the extruder 11 to increase the resin pressure at the tip of the extruder 11. Increasing the resin pressure at the tip of the extruder 11 means increasing the back pressure at the tip, thereby improving the stability of extrusion. The orifice to be used is more preferably 2 mmφ or more and 4 mmφ or less. In addition, it is preferable to attach a gear pump via the adapter between the extruder 11 and the T die 12 from a viewpoint of suppressing the extrusion fluctuation | variation of polypropylene resin. Moreover, it is preferable to attach a leaf disk filter (not shown) in order to remove foreign substances in the polypropylene resin.

(T die)
The T-die 12 is connected to the extruder 11 and has a manifold 12b for spreading the molten polypropylene resin conveyed from the extruder 11 in the lateral direction. In addition, a discharge port 12a that communicates with the manifold 12b and discharges the molten polypropylene resin spread in the lateral direction by the manifold 12b is provided at the lower portion of the T die 12. Therefore, the molten polypropylene resin discharged from the discharge port 12a of the T die 12 is formed into a sheet shape (hereinafter, the molten polypropylene resin formed into a sheet shape is also referred to as a “molten sheet”). ).

  The temperature of the discharged molten sheet is preferably 180 ° C. or higher and 300 ° C. or lower. The temperature of the molten resin is measured using a resin thermometer at the discharge port 12a portion of the T die 12. When the temperature of the molten sheet is less than 180 ° C., the spreadability is inferior, and thus there is a tendency for unevenness in thickness to occur due to non-uniform elongation in the air gap. On the other hand, when the temperature of the molten sheet exceeds 300 ° C., the resin deteriorates and the discharge port 12a is contaminated due to generation of decomposition gas, die line is generated, and the appearance of the polypropylene resin film 25 is poor. Tend to occur.

  The T die 12 is also preferably free from minute steps or scratches on the wall surface of the flow path of the molten polypropylene resin. The discharge port 12a portion (lip portion) of the T die 12 is a material having a small friction coefficient with the molten polypropylene resin, and is plated or coated with a hard material (for example, tungsten carbide-based or fluorine-based special plating). It is preferable that the radius of curvature of the tip portion of the discharge port 12a can be reduced (the tip portion of the discharge port 12a has a shape called a so-called sharp edge).

  The tip of the discharge port 12a of the T die 12 preferably has a sharp edge shape in which the radius of curvature of the opening formed in the wall surface of the flow path of the molten polypropylene resin is 0.1 mm or less. The radius of curvature of the distal end portion of the discharge port 12a is more preferably 0.05 mm or less, and even more preferably 0.03 mm or less. By using such a T die 12, it is possible to suppress the occurrence of “eyes” at the discharge port 12a, and at the same time, it is possible to suppress the die line. For this reason, the uniformity of the external appearance of the polypropylene resin film 25 to be manufactured can be further improved. However, when the radius of curvature is 0.01 mm or less, these effects are improved, but the strength at the distal end portion of the discharge port 12a is reduced, and the discharge port 12a is damaged, thereby causing a large die line or the like. There is a case.

  The length (the length of the air gap) H from the molten resin discharge port 12a in the T-die 12 until the molten sheet is clamped by the elastic roll 13 and the metal roll 14 installed in the lower part thereof, It is preferably about 50 mm to 250 mm, and more preferably about 50 mm to 180 mm. If the length H of the air gap exceeds 250 mm, the cooling efficiency tends to decrease due to exposure to air for a long time, orientation occurs in the air gap, and the produced polypropylene resin film 25 has a large phase difference. Tend to occur. The lower limit of the air gap length H depends on the size of the T-die 12 and the diameters of the elastic roll 13 and the metal roll 14, and is necessarily about 50 mm.

(Elastic roll)
The elastic roll 13 means a metal roll or rubber roll that can be elastically deformed. As an elastically deformable metal roll, an elastic roll 13 having the configuration shown in FIG. 4 can be suitably used. The elastic roll 13 provided in the film manufacturing apparatus 100 shown in FIG. 4 is the same as the forming roll described in Japanese Patent No. 3422798, and specifically, a metal strip having a cylindrical shape. (Also referred to as an endless belt) 13a, a rubber roll 13b (one in the example of FIG. 4) disposed inside the band 13a, and a liquid that fills the space between the band 13a and the rubber roll 13b L is an elastically deformable metal roll having L and temperature adjusting means (not shown) for adjusting the temperature of the liquid L.

  The strip 13a is formed in a cylindrical shape by a metal thin film that can be elastically deformed, such as spring steel, stainless steel, nickel steel, etc., and there is no seam on the surface thereof. Both sides of the belt-like body 13a are closed by a closing member (not shown). As the strip 13a, one having a thickness of about 100 μm to 1500 μm, a diameter of about 200 mm to 600 mm, and a surface roughness of 0.5 S or less can be used, and preferably the surface roughness is 0.2 S or less. It is. The diameter of the strip 13a is set to an appropriate size according to the processing speed of the polypropylene resin film 25. When the diameter of the strip 13a is within the above range, the processing of the polypropylene resin film 25 is performed. The speed can be in the range of several m / min to 100 tens of m / min.

  The rubber roll 13b has a columnar shape, and can be elastically deformed and rotated inside the strip 13a. The rubber roll 13b can be formed of EPDM (ethylene-propylene-diene rubber), neoprene or silicone having a hardness of about 30 to 90. The diameter of the rubber roll 13b can be about 100 mm to 250 mm.

  As the liquid L, for example, water, ethylene glycol, oil or the like can be used. By adjusting the temperature of the liquid L by a temperature adjusting means (not shown), the surface temperature of the strip 13a is indirectly adjusted.

  The thickness of the strip 13a is preferably about 350 to 500 μm, and the hardness of the rubber roll 13b is preferably about 60 to 75. If the thickness of the belt-like body 13a is less than 350 μm and the hardness of the rubber roll 13b is less than 60, the elasticity as the elastic roll 13 becomes too low, and it is difficult to uniformly clamp in the width direction of the elastic roll 13. Tend to be. On the other hand, when the thickness of the strip 13a exceeds 500 μm and the hardness of the rubber roll 13b exceeds 75, the rigidity of the elastic roll 13 becomes too high, and the effect of soft clamping tends to be weakened.

  Moreover, it is also preferable to use the elastic roll 16 of the structure shown by FIG. 5 as an elastic roll. The elastic roll 16 provided in the film manufacturing apparatus 200 shown in this figure is equivalent to the forming belt means described in JP-A-7-40370. Specifically, the elastic rolls 16 are arranged along the outer peripheral surface of the metal roll 14 inside the belt-like body 16a and the metal strip-like body (also referred to as an endless belt) 16a having a cylindrical shape, and the longitudinal direction thereof is It is an elastically deformable metal roll having two rolls 16b and 16c arranged so as to be parallel to each other and a temperature adjusting means (not shown) for adjusting the surface temperature of the strip 16a. The roll 16b is a rubber roll, and the roll 16c is a metal roll. The surface temperature of the strip 16a is adjusted by adjusting the surface temperature of the roll 16c with the temperature adjusting means.

  The strip 16a is formed in a cylindrical shape by a metal thin film that can be elastically deformed, such as spring steel, stainless steel, nickel steel, etc., and there is no seam on the surface thereof. The belt-like body 16a is stretched over a rubber roll 16b and a metal roll 16c, and the tension of the belt-like body 16a can be adjusted by moving the rolls 16b and 16c close to or away from each other. It can be done. As the belt-like body 16a, one having a thickness of about 300 μm to 800 μm and a diameter of about 200 mm to 600 mm when formed into a cylindrical shape can be used, and the surface roughness is preferably 0.2 S or less.

  The rolls 16b and 16c have a columnar shape and are rotatable inside the band-shaped body 16a. The rubber roll 16b can be formed of EPDM (ethylene-propylene-diene rubber), neoprene or silicone having a hardness of about 30 to 90. Moreover, as the rolls 16b and 16c, those having a diameter of about 80 mm to 200 mm can be used.

  When the elastic roll 16 is used, the position where the molten sheet discharged from the discharge port 12a of the T-die 12 is first pinched by the belt-like body 16a and the metal roll 14 becomes the starting point of the pinching pressure, and the pinched resin Is the end point of the pinching pressure.

  The thickness of the strip 16a is preferably about 350 μm to 600 μm, and the hardness of the rubber roll 16 b is preferably about 60 to 80. When the thickness of the belt-like body 16a is less than 350 μm and the hardness of the rubber roll 16b is less than 60, the elasticity of the elastic roll 16 becomes too low, and it is difficult to uniformly pinch the elastic roll 16 in the width direction. It tends to be. Further, if the thickness of the belt-like body 16a exceeds 600 μm and the hardness of the rubber roll 16b exceeds 80, the rigidity as the elastic roll 16 becomes too high, so that it is easy to form a bank (resin pool), There is a tendency that retardation is likely to occur in the obtained polypropylene resin film 25.

  Furthermore, it is also preferable to use the elastic roll 17 having the configuration shown in FIG. 6 as the elastic roll. The elastic roll 17 with which the film manufacturing apparatus 300 shown by FIG. 6 is provided is equivalent to the press roll described in Unexamined-Japanese-Patent No. 11-235747. Specifically, the elastic roll 17 includes a highly rigid metal inner cylinder 17a, a thin metal outer cylinder 17b arranged outside the metal inner cylinder 17a, and a fluid shaft cylinder 17c arranged inside the metal inner cylinder 17a. And a liquid L filling the space between the metal inner cylinder 17a and the thin metal outer cylinder 17b and the fluid shaft cylinder 17c, and a temperature adjusting means (not shown) for adjusting the temperature of the liquid L. It is a deformable metal roll.

  The metal inner cylinder 17a, the thin metal outer cylinder 17b, and the fluid shaft cylinder 17c are arranged so as to be coaxial. The metal inner cylinder 17a is provided with a plurality of through holes 17d along the circumferential direction thereof. Therefore, the liquid L circulates in the elastic roll 17 in the order of the fluid shaft cylinder 17c, the through hole 17d, and the space between the metal inner cylinder 17a and the thin metal outer cylinder 17b.

  The thin metal outer cylinder 17b is made of stainless steel or the like, has no seam on its surface, and has flexibility. The thin metal outer cylinder 17b 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. As the thin metal outer cylinder 17b, one having a thickness of about 2000 μm to 5000 μm, a diameter of about 200 mm to 500 mm, and a surface roughness of 0.5 S or less can be used. 2S or less. If the thickness of the thin metal outer cylinder 17b is less than 2000 μm, the pressure when the molten sheet is sandwiched between the elastic roll 17 and the metal roll 14 tends to be non-uniform, and if it exceeds 5000 μm, the thin metal outer cylinder The elasticity of 17b becomes large, and depending on the thickness of the molten sheet discharged from the discharge port 12a of the T-die 12, there is a tendency that a bank is generated when the molten sheet is pinched.

  As the liquid L, for example, water, ethylene glycol, oil, or the like can be used. By adjusting the temperature of the liquid L by a temperature adjusting means (not shown), the surface temperature of the thin metal outer cylinder 17b is indirectly adjusted.

  Further, as described above, a rubber roll can be used as the elastic roll. When a rubber roll is used as the elastic roll, the surface hardness is preferably 65 to 80, and more preferably 70 to 80. By using a rubber roll having such a surface hardness, it becomes easy to maintain a uniform pressure (linear pressure) when the molten sheet is narrowed, and a bank is formed between the metal roll 14 and the rubber roll. It is easy to form a molten sheet without causing the melting. When the bank is generated, the phase difference of the obtained polypropylene-based resin film 25 tends to be large, and when placed in the liquid crystal display device 1, the visibility may be deteriorated, which is not preferable.

  When a rubber roll is used as the elastic roll, it is preferable to insert a support in the gap between the molten sheet and the rubber roll when the molten sheet is sandwiched between the rubber roll and the metal roll. As the support, for example, a biaxially stretched film made of a thermoplastic resin can be used.

  It is preferable to use a support having excellent smoothness. Since the surface on the opposite side to the surface in contact with the metal roll in the molten sheet is in contact with the support and is sandwiched between the rolls, the surface of the polypropylene resin film 25 obtained has the surface state of the support. Transcribed. Therefore, the smoothness of the obtained surface becomes better as the surface roughness of the support used is smaller and smoother. The surface roughness of the support used is preferably from 0.01 μm to 1.5 μm, more preferably from 0.01 μm to 1.0 μm. Moreover, the thickness of the support body to be used needs to be 5 micrometers or more and less than 50 micrometers, Preferably it is 10 micrometers or more and 30 micrometers or less. If the support to be used is thinner than 5 μm, it is not preferable because it tends to cause wrinkles and causes problems in handling. On the other hand, if it is 50 μm or more, the cooling efficiency of the molten sheet is deteriorated, and the resulting polypropylene system Since the transparency of the resin film 25 deteriorates, it is not preferable. As the thermoplastic resin constituting the support, any resin that does not strongly heat-fuse with a polypropylene resin may be used. Specifically, polyester, polyamide, polyvinyl chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, Such as polyacrylonitrile. Of these, polyesters that undergo little dimensional change due to humidity, heat, etc. are most preferred.

  After the molten sheet sandwiched between the rubber roll and the metal roll together with the support is cooled and solidified, it is laminated with the support, and after slitting the ends as necessary, it is applied to the winder. Thus, a laminate of the polypropylene resin film 25 and the support can be obtained. It is also possible to peel the support in front of the winder and wind only the polypropylene resin film 25. When the support sandwiched between rolls is peeled from the polypropylene resin film 25, the polypropylene resin film 25 may be peeled and removed after the temperature of the polypropylene resin film 25 is cooled to 60 ° C or lower, preferably 40 ° C or lower. preferable. If the support is peeled off in a state where the temperature of the polypropylene resin film 25 is high, the film may be deformed to cause orientation, and the retardation may be increased.

  Among the above-mentioned elastic rolls, it is preferable to use a metal roll that can be elastically deformed because it is excellent in the smoothness of the surface in contact with the elastic roll. The surface of the elastically deformable metal roll is preferably in a mirror state.

(Metal roll)
The metal roll 14 provided in the film manufacturing apparatus 100 shown in FIG. 4 (the same applies to the film manufacturing apparatuses 200 and 300 shown in FIGS. 5 and 6) includes a highly rigid metal outer cylinder 14a and an inner side of the metal outer cylinder 14a. The fluid shaft cylinder 14b disposed in the space, the liquid L filling the space between the metal outer cylinder 14a and the fluid shaft cylinder 14b and the fluid shaft cylinder 14b, and the temperature adjusting means for adjusting the temperature of the liquid L (see FIG. Not shown). The fluid shaft cylinder 14b is provided with a plurality of through holes 14c along the circumferential direction thereof. The diameter of the metal roll 14 can be about 200 mm to 600 mm. In the metal roll 14, similarly to the elastic roll 13, the surface temperature of the metal outer cylinder 14 a is indirectly adjusted by adjusting the temperature of the liquid L by a temperature adjusting means (not shown), and the discharge of the T die 12 together with the elastic roll. The molten sheet discharged from the outlet 12a is cooled and solidified.

  Here, in the case of producing a polypropylene resin film 25 having one surface having a regular uneven surface such as a prism shape or a lens shape, one of the elastic roll 13 and the metal roll 14 has a transfer mold. However, in order to more accurately transfer the shape of the transfer mold, it is preferable to provide the transfer mold on the surface of the metal roll 14. Hereinafter, the metal roll 14 having a transfer mold on the surface is also referred to as a “transfer roll”.

  The transfer mold is provided on the surface of the transfer roll, pressed against the surface of the molten sheet, and transferred to the molten sheet with the surface shape as an inverted mold. The transfer mold is composed of a plurality of recesses provided on the transfer roll surface. The shape of the recess, the groove depth, the pitch interval, and the like are determined according to the desired surface unevenness of the polypropylene resin film 25. The transfer type groove may be parallel to the circumferential direction of the transfer roll, may be parallel to the width direction of the transfer roll, or may form a certain angle with the circumferential direction.

  As a method for producing the transfer mold, a known method can be employed. For example, the surface of a transfer roll made of stainless steel, steel, etc. is subjected to plating treatment such as chrome plating, copper plating, nickel plating, nickel-phosphorus plating, etc. The removal processing used, the laser processing, or the method of processing a shape by performing chemical etching is mentioned.

  Further, the surface of the transfer roll may be subjected to plating treatment such as chromium plating, copper plating, nickel plating, nickel-phosphorous plating, etc. at a level that does not impair the accuracy of the surface shape after the transfer mold is formed.

(Cooling roll)
The cooling roll is a roll for further cooling the molten sheet sandwiched between the elastic roll and the metal roll. The cooling roll 15 provided in the film manufacturing apparatus 100 shown in FIG. 4 (the same applies to the film manufacturing apparatuses 200 and 300 shown in FIGS. 5 and 6) has the same configuration as that of the metal roll 14 described above. Specifically, a highly rigid metal outer cylinder 15a, a fluid shaft cylinder 15b disposed inside the metal outer cylinder 15a, a space between the metal outer cylinder 15a and the fluid shaft cylinder 15b, and the inside of the fluid shaft cylinder 15b. The liquid L to be filled has temperature adjusting means (not shown) for adjusting the temperature of the liquid L. The fluid shaft cylinder 15b is provided with a plurality of through holes 15c along the circumferential direction thereof. As the cooling roll 15, a mirror roll having a diameter of about 200 mm to 600 mm and a surface roughness of 0.2 S or less can be used. Similarly in the cooling roll 15, the surface temperature of the metal outer cylinder 15a is indirectly adjusted by adjusting the temperature of the liquid L by a temperature adjusting means (not shown).

  The polypropylene resin film 25 is manufactured by sandwiching a molten sheet discharged from the discharge port 12a of the T-die 12 between the elastic roll and the metal roll (including a transfer roll) and cooling and solidifying it. The linear pressure is determined by the pressure with which the elastic roll is pressed against the metal roll, and is preferably 1 to 300 N / mm, and more preferably 1 to 200 N / mm. When the linear pressure is less than 1 N / mm, it is difficult to uniformly control the linear pressure on the molten sheet, and when the metal roll is a transfer roll, it tends to be difficult to transfer the transfer mold with high accuracy. . Further, when the linear pressure exceeds 300 N / mm, the molten sheet is strongly pinched, so that the melted sheet is formed into a bank that is formed while collecting in the pinched portion, and the resulting polypropylene type There is a tendency that a large retardation is developed in the resin film 25.

  As a method for controlling the pressure to be pinched (linear pressure), (1) a method of adjusting a roll interval by installing a triangular wedge-shaped “claw” called a cotter in a portion to be pinched, and adjusting the cotter, (2) A method in which both the elastic roll and the metal roll are pressed until they abut against a cotter adjusted at a predetermined pressure using hydraulic pressure, air, or the like. In addition, there are a method in which the number of rotations of the screw is controlled without using a cotter, and the pressure is mechanically steplessly pressed to a predetermined position, and a method in which a servo motor is used in the hydraulic system.

  Moreover, the distance clamped with an elastic roll and a metal roll is 1-30 mm, Preferably it is 1-15 mm. When the clamping distance is within this range, when the metal roll is a transfer roll, the transfer mold can be accurately transferred. As a method of controlling the pinching distance, (1) a method of adjusting a roll interval by installing a triangular wedge-shaped “claw” called a cotter at a pinching portion and adjusting the cotter; (2) an elastic roll The method of adjusting the elasticity of is generally.

  The surface temperature of the elastic roll and the metal roll at the time of sandwiching the molten sheet is not particularly limited, but by rapidly cooling the molten sheet, the polypropylene resin film 25 having high transparency is easily obtained. As a specific surface temperature, it is preferable that the surface temperature of at least one of the elastic roll or the metal roll is 0 to 60 ° C, more preferably the surface temperature of at least one of the rolls is 0 to 40 ° C. More preferably, the surface temperature of at least one roll is 0-30 degreeC.

  The processing speed of the polypropylene resin film 25 increases as the diameter of a metal roll such as a transfer roll increases. For example, when the diameter of the metal roll is 600 mm, the processing speed of the polypropylene resin film 25 can be set to a maximum of about 50 m / min, usually about 30 m / min.

  The elastic roll and the metal roll are generally arranged in a line below the T die 12. The elastic roll and the metal roll are arranged at a predetermined interval, and are discharged from the interval between the elastic roll and the metal roll, the rotational speed of the elastic roll, the metal roll and the cooling roll, and the discharge port 12a of the T die 12. The thickness of the polypropylene resin film 25 is defined by the discharge amount of the molten sheet.

  The polypropylene resin film 25 further cooled by the cooling roll is slit (cut) at the ears as necessary, and is wound up by a winder or cut into single sheets. Temporary protective film for protecting the surface of the polypropylene resin film 25 before or after slitting the ear portion of the polypropylene resin film 25 until it is used. May be laminated.

  The polarizing plate 20 can be manufactured by the above manufacturing method. The manufactured polarizing plate 20 is bonded to the surface of the liquid crystal cell 40 and used as the liquid crystal panel 2. The liquid crystal panel 2 is used as the liquid crystal display device 1 by incorporating the backlight 10 and the light diffusion plate 50 as described above. The mode of the liquid crystal cell 40 to which the polarizing plate 20 is applied is not particularly limited. For example, the liquid crystal cell 40 in various modes such as VA mode, IPS mode, and TN mode can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these examples.

[Example 1]
(A) Preparation of sample Using the film manufacturing apparatus 200 shown in FIG. 5, a polypropylene resin film was prepared according to the following procedure. First, an isotactic polypropylene resin A (propylene homopolymer, MFR = 7 g / 10 min, Tm = 164 ° C.) heated to 270 ° C. 50 mmφ extruder 11 (screw: L / D = 32, full The melt is kneaded by a flight screw) and fed from the extruder 11 to the gear pump, adapter and T-die 12 (all set at 270 ° C.) installed after the extruder 11 in this order, and the discharge of the T-die 12 A molten polypropylene resin sheet (molten resin) was discharged from the outlet 12a (lip port). The temperature of the molten resin at the discharge port 12a of the T die 12 was 270 ° C. The molten resin is sandwiched between an elastic roll 16 (no transfer mold) and a metal roll 14 (no transfer mold) under the manufacturing conditions shown in Table 1, and further cooled by a cooling roll 15 to obtain a polypropylene resin film. Produced.

The thickness, haze, and in-plane retardation value Re of the polypropylene resin film obtained by the above method were measured by the following apparatus. As a result, the thickness of the polypropylene resin film was 107.1 μm, the haze was 1.3%, and the in-plane retardation value Re was 20.6 nm. The results are shown in Table 1.
(Thickness of polypropylene resin film)
Using a contact thickness meter (MS-5C, manufactured by NIKON), the thickness at 5 points was measured, and the average value was taken as the thickness of the polypropylene resin film.
(Haze of polypropylene resin film)
A haze meter “HM” manufactured by Murakami Color Research Laboratory Co., Ltd. in accordance with JIS K 7136
-150 "type was used for measurement.
(In-plane retardation value Re of polypropylene resin film)
It measured using the phase difference measuring apparatus (Oji Scientific Instruments Co., Ltd. product, KOBRA-WPR).

  Note that the “clamping distance” shown in Table 1 indicates the length by which the molten resin is clamped between the elastic roll 16 and the metal roll 14, and there is a sense between the elastic roll 16 and the metal roll 14. The pressure paper (Fuji Film Business Supply Co., Ltd. pre-scale LLW) was sandwiched, and the distance in the MD direction of the colored portion of the pressure-sensitive paper was measured and used as the pressure distance. Moreover, the used elastic roll 16, the metal roll 14, and the cooling roll 15 have the following structures.

(Elastic roll 16)
Strip 16a: made of metal, surface roughness 0.2S, thickness 300 μm
Roll 16b: made of silicone, diameter 160mm, hardness 60
Roll 16c: metal, diameter 160mm
(Metal roll 14)
Metal outer cylinder 14a: metal, diameter 300mm
(Cooling roll 15)
Metal outer cylinder 15a: metal, diameter 300mm, surface roughness 0.1S (mirror surface)

[Comparative example]
(B) Preparation of sample As in Example 1, except that the film production conditions (surface temperature of metal roll 14 and elastic roll 16, pinching distance, linear pressure and line speed) were changed as shown in Table 1. A polypropylene resin film of Comparative Example 1 was produced. As shown in this table, the obtained film had a film thickness of 97.0 μm, a haze of 21.8%, and an in-plane retardation value Re of 55.6 nm.

（ここで、ｖは入射レーザー光の波数の逆数（ｖ＝（１／５１４．５）＝０．００１９４３６３４・・・）、ｎ_ｓはサンプルの屈折率（ｎｓ：約１．５）、ｎ_ｐはプリズムの屈折率（ｎ_ｐ＝１．８８：高屈折率ガラス）、θは入射角度（θ＝５６．５°） (C) Measurement of surface orientation parameter The surface orientation parameter by ATR-Raman spectroscopy was measured for each of the samples of Examples and Comparative Examples obtained in the above (a) and (b). The measurement of the surface orientation parameter was performed with the following apparatus and measurement conditions.
<Measurement device>
Ramanor T-6400 (manufactured by Jobin Yvon / Ehime Bussan)
<Measurement conditions>
Measurement mode: ATR Raman (Ge 30 °),
Prism: High refractive index glass Incident angle: 56.5 ° (ATR), 51.0 ° (bulk)
Beam diameter: 100 μm
Light source: Ar laser / 514.5nm
Laser power: 400mW (At Tube)
Diffraction grating: Single 1800 gr / nm
Slit: 100 μm
Detector: CCD / Jobin Yvon 1024Channel
Number of measurements: n = 3 (Numerical data such as peak intensity used an average value of N = 3)
<Measurement method>
The ATR-Raman spectrum was measured by directly pressing the polypropylene resin film surface against a high refractive index glass prism. Further, the penetration depth of the measurement light was calculated based on the following formula. As a result, it was found that the penetration depth was about 100 nm.

(Where v is the reciprocal of the wave number of the incident laser beam (v = (1 / 514.5) = 0.000143634...), N _s is the refractive index of the sample (ns: about 1.5), n _p Is the refractive index of the prism (n _p = 1.88: high refractive index glass), θ is the incident angle (θ = 56.5 °)

  Using the samples of Example 1 and Comparative Example 1, absorption spectra were measured for each of the parallel polarized light and the vertically polarized light under the measurement apparatus coating measurement conditions described above. The obtained absorption spectra are shown in FIG. 7 (Example 1) and FIG. 8 (Comparative Example 1).

(D) Preparation of samples for adhesion test Samples for adhesion tests were prepared by the following procedure for each of the examples obtained in (a) and the comparative examples obtained in (b). did. In both Example 1 and Comparative Example 1, a polarizing plate having the layer configuration shown in FIG. 9 was used as a sample.
(1) Preparation of polarizing film A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was immersed in pure water at 30 ° C., and then the weight of iodine / potassium iodide / water. It was immersed at 30 ° C. in an aqueous solution having a ratio of 0.02 / 2/100. Then, it was immersed at 56.5 ° C. in an aqueous solution having a potassium iodide / boric acid / water weight ratio of 12/5/100. Subsequently, the film was washed with pure water at 8 ° C. and then dried at 65 ° C. to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching was mainly performed in the iodine staining and boric acid treatment steps, and the total stretching ratio was 5.3 times.

(2) Production of Adhesive Liquid After mixing the following components at the blending ratio (unit: part) shown in Table 2, defoaming was performed to prepare a photocurable adhesive liquid (adhesive A). In addition, a photocationic polymerization initiator (b1) was mix | blended as a 50% propylene carbonate solution, and displayed in Table 2 with the amount of solid content.
(A) Epoxy compound (a1) 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (a2) 1,4-butanediol diglycidyl ether (B) Photocationic polymerization initiator ("Initiator" in the table) Abbreviated)
(B1) 4,4′-bis (diphenylsulfonio) phenyl sulfide bis (hexafluorophosphate) photocationic polymerization initiator [trade name “SP-150”, manufactured by ADEKA Corporation]

(3) Preparation of polarizing plate The polypropylene film obtained in Example 1 and Comparative Example 1 was bonded to one surface of the polarizing film using the active energy ray-curable adhesive, and the other side was bonded. A cyclic olefin film (ZEONOR 75 μm, manufactured by Nippon Zeon Co., Ltd.) was bonded to the surface using the active energy ray-curable adhesive. In addition, a corona treatment device (high frequency power source: CT-0212 manufactured by Kasuga Electric Co., Ltd., transmitter body: CT-0212 manufactured by Kasuga Electric Co., Ltd., high-voltage transformer; Using CT-T022), the polypropylene film surface and the cyclic olefin film surface were adjusted so that the distance from the electrode of the corona treatment device was 3 mm, output 280 W, line speed 1.0 m / min, ambient temperature 23 ° C., ambient The corona treatment was performed three times continuously under the condition of relative humidity 55% RH. Next, by passing it once through a UV irradiation device manufactured by Nippon Battery Co., Ltd. (UV lamp uses “HAL400NL” at 80 W and irradiation distance is 50 cm) at a line speed of 1.0 m / min. The active energy ray-curable adhesive was cured to obtain a polarizing plate.

(E) Measurement of adhesiveness A 90 ° peel test was performed on each of the samples (polarizing plates) of the examples and comparative examples obtained in the above steps using the following apparatus and conditions.
<Evaluation equipment>
Autograph AG-1 (manufactured by Shimadzu Corporation)
<Measurement conditions>
Test speed: 300 mm / min Test piece: 200 mm length x 25 mm width (cyclic olefin resin film side down with sample fixed to glass plate with glue)
<Measurement method>
The end portion of the sample fixed to the glass plate was pinched and, as shown in FIG. The load at the time of peeling was measured with an evaluation device, and the adhesive strength was evaluated.

Table 3 shows the results of the orientation parameter measurement and the adhesion force measurement in Examples and Comparative Examples. For reference, bulk orientation parameters are also shown. The orientation parameter (bulk) is an orientation parameter calculated based on a Raman spectrum by Raman scattered light from the entire polypropylene resin film. This orientation parameter (bulk) is different from the orientation parameter (ATR) indicating the molecular orientation in the vicinity of the surface layer, and indicates the molecular orientation in the entire thickness direction of the polypropylene resin film.

  From the results shown in this table, when the orientation parameter (ATR) is 1.05 as in Example 1, the adhesive strength is as good as 11.6 N / 25 mm. On the other hand, when the orientation parameter (ATR) is 1.82 as in Comparative Example 1, the adhesive force is considerably inferior to that of the example. From these results, as shown in Example 1, when the surface orientation parameter is in the range of 0.95 (= 1 / 1.05) to 1.05, the adhesive force is better than the other ranges. I can say that.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 2 Liquid crystal panel, 10 Backlight, 11 Extruder, 12 T die, 12a Discharge port, 12b Manifold, 13 Elastic roll, 13a Strip body, 13b Rubber roll, 14 Metal roll, 14a Metal outer cylinder, 14b Fluid shaft cylinder, 14c Through hole, 15 Cooling roll, 15a Metal outer cylinder, 15b Fluid shaft cylinder, 15c Through hole, 16 Elastic roll, 16a Strip, 16b, 16c roll, 17 Elastic roll, 17a Metal inner cylinder, 17b Thin metal outer cylinder, 17c Fluid shaft cylinder, 20 Polarizing plate, 21 Polarizing film, 23 Transparent resin film, 25 Polypropylene resin film, 27 Adhesive layer, 29 Adhesive layer, 30 Polarizing plate, 40 Liquid crystal cell, 50 Light diffusion Plate, 60 polarizing plate, 65 condensing film, 100-300 film manufacturing apparatus, The length of the air gap, L liquid

Claims (7)

  A polypropylene-based resin film, wherein a surface orientation parameter obtained by Raman spectroscopy measurement by attenuated total reflection method on at least one of the film surfaces is in a range of 0.66 to 1.50.   A polypropylene resin film, wherein the surface orientation parameter is in the range of 0.95 to 1.05. A polarizing film comprising a uniaxially stretched polyvinyl alcohol-based resin film in which iodine or a dichroic dye is adsorbed and oriented;
A polypropylene-based resin film according to claim 1 or 2, which is laminated on the polarizing film via an adhesive layer,
The polarizing plate, wherein the polypropylene resin film is laminated so that the one surface is in contact with the adhesive layer.   The said adhesive bond layer is a polarizing plate of Claim 3 which consists of a hardened | cured material layer of the active energy ray curable resin composition containing an epoxy resin.   The polarizing plate of Claim 3 or 4 further equipped with the protective film or optical compensation film laminated | stacked on the surface on the opposite side to the surface on which the said polypropylene resin film in the said polarizing film is laminated | stacked.   A liquid crystal panel comprising: a liquid crystal cell; and the polarizing plate according to claim 3, which is laminated on the liquid crystal cell.   A liquid crystal display device comprising: a surface light source element; and the liquid crystal panel according to claim 6.

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