JP4902844B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film, and in particular, relates to a laminated polyester film having excellent visibility when various surface functional layers are laminated on the coating layer surface of the film and having a small amount of oligomer in the film.

  Conventionally, a laminated polyester film in which coating layers having various functions such as adhesiveness and antistatic properties are provided on a polyester film is a liquid crystal display (hereinafter abbreviated as LCD), a plasma display panel (hereinafter abbreviated as PDP). In addition, it is used for various optical applications such as for producing display members such as organic electroluminescence (hereinafter abbreviated as organic EL). With the diversification of applications, film processing conditions and usage conditions have diversified. When a polyester film is heat-treated, oligomers present inside the film are deposited on the surface, causing contamination and transparency in the manufacturing process. In some cases, problems such as deterioration in brightness and uneven brightness of the display screen may occur.

  In recent years, with the advancement of the IT (Information Technology) field, various problems associated with precipitation of oligomers tend to become more apparent as the quality of laminated polyester films used in the production of LCD, PDP, organic EL display members, etc. .

  Conventionally, as a method for preventing oligomer precipitation, reduction of oligomers contained in the raw material by solid-phase polymerization (Patent Document 1) or improvement of hydrolysis resistance of a polyester film using a terminal blocker The method of doing has been taken. However, even if it is a solid-phase polymerized raw material, depending on the film production conditions, the effect is not seen because the oligomer is produced as a by-product due to heating, etc. Has not reached. In addition, when a terminal blocking agent is used, there is a risk of generation of foreign matters due to the terminal blocking agent, coloration of the polymer, deterioration of solid phase polymerizability, and the like.

  Moreover, excellent transparency and visibility are required for optical films used in LCDs, PDPs, organic ELs, etc., and generally used by laminating surface functional layers such as hard coat layers and antireflection layers. ing. When using a polyester film as a base material, in order to improve adhesiveness with a surface functional layer, the case where an easily adhesive coating layer is provided as an intermediate layer is common.

  In recent years, in applications such as LCD and PDP display members, there has been a demand for larger screens, higher image quality, and higher quality, and accordingly, there is a demand for suppression of iris-like colors (interference unevenness) especially under fluorescent lamps. The level is getting higher. In addition, fluorescent lamps have become a three-wavelength type for daylight color reproducibility, and interference unevenness is more likely to occur. Furthermore, there is an increasing demand for simplification of the antireflection layer in order to achieve cost reduction and the like. Therefore, the optical design of the coating layer laminated on the polyester film has become important.

  On the other hand, as an application layer provided in order to improve adhesiveness with the surface functional layer laminated | stacked on a polyester film, a polyester resin, an acrylic resin, a urethane resin, etc. are mentioned.

  In the conventional resin coating layer as described above, the refractive index is fixed to around 1.50. Therefore, when designing an antireflection film, the antireflection performance is limited, and interference unevenness occurs due to external light reflection. May not be sufficiently suppressed (Patent Documents 2 and 3). When a film in which interference unevenness due to reflection of external light is remarkably generated is used as a display member for LCD, PDP, organic EL, etc., various problems due to deterioration in visibility tend to become more apparent. In addition, the remarkable occurrence of interference unevenness not only deteriorates the visibility, but may also cause eye fatigue and health problems.

In order to reduce interference unevenness, in order to increase the refractive index of the coating layer, a conventional coating layer is provided which is formed from a coating liquid mainly composed of a water-based polyester resin and a chelate or acylate compound of water-soluble titanium or zirconium. In the method (Patent Document 4), the adhesion with various surface functional layers to be laminated may not be sufficient. Further, there is a method (Patent Document 5) for increasing the refractive index of the coating layer by including a metal oxide having a high refractive index in the coating layer. In some cases, sufficient performance as a film cannot be exhibited.
JP 2003-119271 A JP-A-10-119215 JP 2000-246855 A Japanese Patent No. 3632044 JP 2004-54161 A

  The present invention has been made in view of the above-described circumstances, and the solution is to reduce various types of display components such as LCDs, PDPs, organic ELs, and other display members that have reduced interference unevenness due to external light reflection. Another object is to provide a laminated polyester film suitable for various optical applications as well as for material production.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-mentioned problems, and have completed the present invention.

That is, the gist of the present invention is that an aromatic compound is formed on at least one surface of a polyester film stretched in at least a uniaxial direction containing an amount of a titanium compound and a phosphorus compound that simultaneously satisfy the following formulas (1) and (2). It consists in the laminated polyester film characterized by having a coating layer containing Nagy imide compound having the.
1 ≦ W _Ti ≦ 20 (1)
1 ≦ W _P ≦ 300 (2)
(In the _{formula, W Ti} titanium element content in the polyester film (ppm), _{W P} denotes phosphorus element content in the polyester film (ppm))

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  Moreover, it is necessary to contain both a titanium compound and a phosphorus compound in at least one layer of the polyester film of the present invention. The titanium element content needs to be 20 ppm or less, preferably 10 ppm or less, and the lower limit is usually 1 ppm, but is preferably 2 ppm. When there is too much content of a titanium compound, an oligomer byproduces in the process of melt-extruding polyester, and it may be impossible to obtain a film having low transparency and high transparency. On the other hand, phosphorus element content is 1 ppm or more normally, Preferably it is 5 ppm or more, and an upper limit is 300 ppm or less normally, Preferably it is 200 ppm or less. By containing a specific amount of the above-described titanium and containing a phosphorus compound, it is possible to exert a remarkable effect on the reduction of the contained oligomer. When there is too much content of a phosphorus compound, gelatinization will occur and it may become a foreign material and cause the quality of a film to fall. In the present invention, when the titanium compound and the phosphorus compound are contained in the above-described range, the by-product of the oligomer can be prevented, and the effect of the present invention is highly obtained.

  Further, the layer containing the titanium compound and the phosphorus compound preferably contains no antimony element, and is usually 100 ppm or less, preferably 60 ppm or less, and more preferably 10 ppm or less. If the amount of the antimony element is too large, there is a risk that the melt will cause agglomeration and cause foreign matters, or the film will become dark and the transparency may be impaired. In addition, when a polyester obtained by solid-phase polymerization to form a low oligomer is melted to form a film, in the case of a polyester containing a titanium compound, the titanium compound is effectively deactivated by containing a phosphorus compound at the time of melting. Therefore, compared with the polyester containing an antimony compound, the degree of increase due to oligomer regeneration can be reduced.

  The polyester of the present invention may be obtained by a melt polymerization reaction, but if a raw material obtained by solid-phase polymerization of a polyester that has been chipped after melt polymerization is used, the amount of oligomer contained in the raw material Is preferably used because it can be reduced.

  The amount of oligomer contained in the polyester film is preferably 0.70% by weight or less, and more preferably 0.50% by weight or less. When the amount of oligomer in the polyester layer is small, the amount of oligomer contained in the polyester film of the present invention is reduced and the effect of preventing oligomer precipitation on the film surface is particularly high.

  In the present invention, a film having a structure in which a polyester having a low oligomer content is coextruded and laminated on at least one surface of a layer made of polyester having a normal oligomer content may be used. The effect of suppressing oligomer precipitation obtained in the present invention can be exhibited to a high degree.

  In the polyester layer of the film of the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples include, for example, silicon oxide, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, phosphorus Examples thereof include particles of magnesium acid, kaolin, aluminum oxide, and the like. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-5 micrometers normally, Preferably it is the range of 0.01-3 micrometers. When the average particle size is less than 0.01 μm, the particles tend to aggregate and the dispersibility may be insufficient. On the other hand, when the average particle size exceeds 5 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  Although the thickness of the polyester film in this invention will not be specifically limited if it is a range which can be formed into a film as a film, Usually, it is 5-250 micrometers, Preferably it is the range of 10-200 micrometers.

  Although the preferable example of the manufacturing method of polyester of this invention is demonstrated, this invention is not necessarily limited to this. Here, an example in which polyethylene terephthalate is used as the polyester is shown, but the production conditions differ depending on the polyester used.

First, bis-β-hydroxyethyl terephthalate (hereinafter abbreviated as BHT) is obtained by esterification from terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol according to a conventional method. Next, it is transferred to this BHT polymerization tank, the temperature is raised while reducing the pressure, and finally the polymer is heated to 280 ° C. under vacuum to advance the polymerization reaction to obtain a polyester.

  The intrinsic viscosity of the polyester of the present invention is usually in the range of 0.40 to 0.90, preferably 0.45 to 0.80, and more preferably 0.50 to 0.70. When the intrinsic viscosity is less than 0.40, the mechanical strength of the film tends to be weakened. When the intrinsic viscosity is more than 0.90, the melt viscosity becomes high, the load on the extruder is increased, and the production cost is increased. Problems may occur.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the laminated polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

  Furthermore, what is called an in-line coating which processes the film surface during the extending | stretching process of the above-mentioned polyester film can be given. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with stretching, and the thickness of the coating layer can be changed by the stretching ratio, so that a film suitable as a polyester film can be produced. .

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. As for the coating layer, it may be provided on the polyester film by the above-mentioned in-line coating, a so-called off-line coating applied outside the system on the film once manufactured may be employed, or both may be used in combination. In-line coating is preferably used because it can be manufactured at low cost.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

In the present invention, an imide having an aromatic compound in the molecule on at least one surface of a polyester film stretched in at least a uniaxial direction containing an amount of a titanium compound and a phosphorus compound that simultaneously satisfy the following formulas (1) and (2): It is an essential requirement to have a coating layer containing a compound.
1 ≦ W _Ti ≦ 20 (1)
1 ≦ W _P ≦ 300 (2)
(In the _{formula, W Ti} titanium element content in the polyester film (ppm), _{W P} denotes phosphorus element content in the polyester film (ppm))

  The imide compound having an aromatic compound in the molecule is not particularly limited as long as the imide compound has an aromatic compound such as a benzene ring or a naphthalene ring in the molecule. If the aromatic compound is not present in the molecule, the refractory index of the coating layer may not be sufficiently improved only by the imide structure, and interference unevenness when the surface functional layer is laminated may not be sufficiently improved.

  As the imide compound, an imide compound represented by the following general formula (3) is more preferably used in consideration of appropriateness as a coating agent and difficulty in production.

In the above formula, at least one of R ¹ , R ² and R ³ is a group having an aromatic compound, and n represents an integer of 1 or 2.

R ¹ and R ² may be the same or different and each represents a hydrogen atom, an alkyl group, an alkenyl group, or a phenyl group. R ³ is an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 3 to 6 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or a monovalent aromatic having 6 to 12 carbon atoms when n is 1. A group or a benzyl group, or a group-[(C _q H _2q O) _t (C _r H _2r O) _u C _v H _{2v + 1} ] (where q, r and v are each an integer of 2 to 6) T represents an integer of 0 or 1, u represents an integer of 1 to 30) or a group —C ₆ H ₄ —T—C ₆ H ₅ {where T is —CH ₂ —, —C ( Represents CH ₃ ) ₂ —, —CO—, —O—, —S—, —SO ₂ —.

R ³ is an alkylene group having 2 to 20 carbon atoms, a cycloalkylene group having 5 to 8 carbon atoms, a group — [(C _x H _2x O) _y (C _z H _2z O) _w C when n is 2. _b H _2b ]-(wherein x, z and b each represent an integer of 2 to 6, y represents an integer of 0 or 1, and w represents an integer of 1 to 30), 6 to 6 carbon atoms 12 divalent aromatic groups, group —R—C ₆ H ₄ — (R ′) _m — (where m represents an integer of 0 or 1, and R and R ′ may be the same or different. , Represents a C 1-4 alkylene group or a C 5-8 cycloalkylene group) or a group —C ₆ H ₄ —A—C ₆ H ₄ — {where A is —CH ₂ —, —C ( _{CH 3) 2 -, - CO} -, - O -, - OC 6 H 4 C (CH 3) 2 C 6 H 4 O -, - S -, - SO 2 - shows a. }.

In the R ³ group, 1 to 3 hydrogen atoms may be substituted with a hydroxyl group, a carboxyl group, an amino group, a mercapto group, a carbamoyl group, or an isocyano group.

In the general formula (3), examples of the asymmetric alkylene-phenylene group contained in the group —R—C ₆ H ₄ — (R ′) _m — represented by R ³ in the case of n = 2 include, for example, The thing represented by is mentioned.

In order to make the formed coating layer tough, it is preferable that at least one of R ^{1 and} R ² has an alkenyl group, and an alkenyl-substituted nadiimide represented by the following formula (4) is preferably used. .

上記式中、Ｒ^４は水素原子あるいはメチル基を示す。

In the above formula, R ⁴ represents a hydrogen atom or a methyl group.

  The imide compound having an aromatic compound in the molecule used in the present invention is not limited to these. Moreover, the imide compound which has these aromatic compounds in a molecule | numerator may be used independently, may be used in mixture of multiple types, and also may be used as an oligomer.

  In addition, in order to more efficiently cure an imide compound having an aromatic compound in the molecule, for example, an organic peroxide, an inorganic peroxide, an onium salt, a cation catalyst, and an organic group-containing metal compound are used in combination as a curing catalyst. It is also possible to do.

  In the laminated polyester film of the present invention, a binder polymer is used to improve antireflection performance and transparency when various surface functional layers are laminated on the coated surface, and to improve adhesion to various surface functional layers. It is also possible to use together.

  The “binder polymer” used in the present invention is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). ) Is a polymer compound having a molecular weight of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkylene imine, methyl cellulose, hydroxy cellulose, and starch. And the like.

  By including a binder polymer having an aromatic ring skeleton in the above-described binder polymer in the coating layer, the antireflection ability when various surface functional layers are laminated on the coating surface is further improved. preferable.

  Furthermore, a crosslinking agent may be used in combination in the coating layer as long as the gist of the present invention is not impaired, and specific examples include methylolated or alkylolated urea, melamine, guanamine, acrylamide, and polyamide systems. Examples thereof include compounds, oxazoline compounds, epoxy compounds, aziridine compounds, block polyisocyanates, and silane coupling agents. These crosslinking components may be bonded in advance to the binder polymer.

  Further, for the purpose of improving the adhesion and slipperiness of the coating layer, inert particles may be contained, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like.

  Furthermore, as long as it does not impair the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc. May be contained.

  The content of the imide compound having an aromatic compound in the molecule in the coating layer constituting the laminated polyester film in the present invention is preferably in the range of 10 to 100% by weight. If it is out of this range, the adhesion with the surface functional layer may be insufficient, or the visibility after the surface functional layer is laminated may deteriorate. The content of the imide compound having an aromatic compound in the molecule is determined by dissolving and extracting the resin or coating layer with an appropriate solvent or warm water, separating by molecular weight by chromatography, structural analysis by NMR, IR, It can obtain | require by analyzing by pyrolysis GC-MS (gas chromatography mass spectrometry).

  It is preferable to produce a laminated polyester film by coating the above-mentioned series of compounds as a solution or dispersion on a polyester film with a coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight. .

  Furthermore, in the case of in-line coating, the above-described series of compounds is used as an aqueous solution or water dispersion, and the coating solution adjusted with a solid content concentration of about 0.1 to 50% by weight as a guide is laminated on the polyester film. It is preferred to produce a polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

Although there is no restriction | limiting in the application quantity (after drying) of the coating layer provided on a polyester film regarding the lamination | stacking polyester film in this invention, Usually 0.005-1g / m < ² >, Preferably 0.005-0.5g / m ² range. When the coating amount is less than 0.005 g / m ² , the uniformity of the coating thickness may be insufficient. On the other hand, when the coating is applied in excess of 1 g / m ² , problems such as a decrease in slipperiness may occur.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds. On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The specular reflectance on the coating layer side provided on at least one surface of the laminated polyester film of the present invention is 5.0% or more, preferably 5.5% or more at an arbitrary wavelength of 400 to 800 nm. It is preferably less than the absolute reflectance of the polyester film that is not laminated. When the specular reflectance is less than 5.0%, the antireflection performance deteriorates when a surface functional layer such as a hard coat layer or an antireflection layer is laminated on the coating layer of the film. It may become stronger and visibility may be reduced.

  According to the laminated polyester film of the present invention, it is possible to provide a laminated film excellent in antireflection performance when various surface functional layers are laminated, and its industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. It was dissolved and measured at 30 ° C.

(2) Measurement of average particle diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Measurement of oligomer (cyclic trimer) content in polyester film layer Chloroform / 1,1,1,3,3,3-hexafluoro-2-propanol (mixing ratio: 3) / 2) After dissolving in the mixed solution, reprecipitated with chloroform / methanol (mixing ratio: 2/1) and filtered to remove linear polyethylene terephthalate, and then the solvent in the obtained filtrate was removed using an evaporator. The precipitate obtained was dissolved in a predetermined amount of DMF (dimethylformamide). The obtained DMF is supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer (cyclic trimer) contained in the polyester, and this value is divided by the amount of polyester used for measurement to obtain a polyester film. The amount of oligomer (cyclic trimer) contained therein. The amount of oligomer (cyclic trimer) determined by liquid chromatography was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by weighing a preliminarily collected oligomer (cyclic trimer) and dissolving it in a weighed DMF. The conditions for the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) Quantification of the amount of metal element and phosphorus element in the film Using a fluorescent X-ray analyzer (model “XRF-1500” manufactured by Shimadzu Corporation), the amount of element in the film is measured by single film measurement by the film FP method. The detection limit in this method is usually about 1 ppm.

(5) Method of measuring the minimum reflectance value from the surface of one layer in a polyester film A black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) was previously pasted on the measurement back surface of the polyester film, and a spectrophotometer (Shimadzu Corporation). If the coating layer is present at an incident angle of 8 ° using a UV-3100PC type manufactured by Seisakusho Co., Ltd., the surface of the coating layer is mirror-reflected with a wavelength range of 400 to 800 nm, a sampling pitch of 1 nm, a slit width of 20 nm, and a medium scanning speed. The rate was measured and its minimum value was evaluated.

(6) Adhesion measurement method A 2: 1 mixture of KAYARAD (registered trademark) manufactured by Nippon Kayaku Co., Ltd. and Shikko (registered trademark) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. is applied to the coated layer side of the laminated polyester film. It was applied and dried at 80 ° C. for 1 minute to remove the solvent. Next, while running the film at a feeding speed of 10 m / min, ultraviolet rays were irradiated using a mercury lamp under the conditions of irradiation energy of 120 W / cm and irradiation distance of 10 cm to obtain a film having a surface functional layer. A cross cut (100 squares of 1 mm ² ) is applied to the film, and an 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) is applied to the film, and a peeling angle of 180 degrees is applied. After peeling off rapidly, the peeled surface was observed. If the peeled area was less than 20%, it was evaluated as ◯, if it was 20% or more but less than 50%, Δ, and if it was 50% or more, ×.

(7) Evaluation method of antireflection ability On the coating layer side of the laminated polyester film, a 2: 1 mixture of KAYARAD (registered trademark) manufactured by Nippon Kayaku Co., Ltd. and Shikko (registered trademark) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Was applied and dried at 80 ° C. for 1 minute to remove the solvent. Next, while running the film at a feed rate of 10 m / min, ultraviolet rays were irradiated using a mercury lamp under the conditions of irradiation energy of 120 W / cm and irradiation distance of 10 cm to obtain a film having a surface functional layer having a thickness of 10 μm. . The obtained film was visually observed under a three-wavelength light region type fluorescent lamp, and interference unevenness was observed.

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester>
Production Example 1 (Polyester A0)
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, and an ethylene glycol slurry of silica particles having an average particle size of 2.5 μm was added so that the content of the particles with respect to polyester was 0.06% by weight, and a polycondensation reaction was performed for 4 hours. went.
That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.55 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (A0) having an intrinsic viscosity of 0.55.

Production Example 2 (Polyester A1)
Polyester A0 obtained in Production Example 1 was subjected to solid phase polymerization at 220 ° C. under vacuum to obtain polyester (A1) having an intrinsic viscosity of 0.67.

Production Example 3 (Polyester B)
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is set to 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, orthophosphoric acid was added, and germanium dioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power in the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain polyester B having an intrinsic viscosity of 0.63.

Production Example 4 (Polyester C)
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. After adding ethyl acid phosphate to this reaction mixture, it was transferred to a polycondensation tank, and an ethylene glycol slurry of silica particles having an average particle diameter of 2.5 μm was added so that the content of the particles with respect to polyester was 0.06 wt%. Then, antimony trioxide was added and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity of this polyester was 0.63. The obtained polyester chip was subjected to solid phase polymerization at 220 ° C. under vacuum to obtain polyester C having an intrinsic viscosity of 0.63.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Alkenyl-substituted nadiimide (I): A compound represented by the following formula (6) was used.

Polyester resin: (II)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)
Hexamethoxymethylmelamine: (III)
Particles: (IV) Silica sol with an average particle diameter of 65 nm

Example 1:
A raw material prepared by mixing the polyester A1 produced in Production Example 2 and the polyester B produced in Production Example 3 in a ratio of 95: 5 by weight is melted at 290 ° C., extruded from a die, and subjected to an electrostatic application adhesion method. It cooled and solidified on the cooling roll which set temperature to 40 degreeC, and the unstretched sheet was obtained. The film was stretched 3.7 times in the longitudinal direction at a film temperature of 83 ° C., and then the coating liquid 1 shown in Table 1 below was applied to both sides of the longitudinally stretched film, led to a tenter, and successively 3.9 times in the transverse direction. Axial stretching was performed. Thereafter, heat treatment was performed at 220 ° C. to obtain a laminated polyester film having a thickness of 100 μm having a coating layer having a coating amount (after drying) of 0.1 g / m ² . When the reflectance of the finished laminated polyester film was measured in the wavelength range of 400 to 800 nm, the minimum value was 6.1%. When the interference unevenness after laminating the surface functional layer was observed, the visibility was good. The properties of this film are shown in Table 2 below.

Examples 2 and 3:
In Example 1, except having changed a coating agent composition into the coating agent composition shown in Table 1, it manufactured like Example 1 and obtained the laminated polyester film. As shown in Table 2, the finished polyester film had a high reflectance, and when the interference unevenness after laminating the surface functional layer was observed, the visibility was good.

Example 4:
In Example 1, the polyester was changed and manufactured in the same manner as in Example 1 except that the oligomer amount, antimony element amount, titanium element amount, and phosphorus element amount in the obtained film were different as shown in Table 2. A laminated polyester film was obtained.

Comparative Examples 1 and 2:
In Example 1, except having changed a coating agent composition into the coating agent composition shown in Table 1, it manufactured like Example 1 and obtained the laminated polyester film. When the finished laminated polyester film was evaluated, as shown in Table 2, deterioration of visibility due to interference unevenness and deterioration of adhesion with the surface functional layer were observed.

Comparative Example 3:
In Example 1, it manufactured similarly to Example 1 except having not provided the application layer, and obtained the polyester film. When the finished laminated polyester film was evaluated, as shown in Table 2, the visibility was deteriorated due to uneven interference.

Comparative Example 4:
In Example 1, the polyester was changed and manufactured in the same manner as in Example 1 except that the oligomer amount, antimony element amount, titanium element amount, and phosphorus element amount in the obtained film were different as shown in Table 2. A laminated polyester film was obtained.

なお、上記表１中の塗布液の濃度は１０重量％とした。

The concentration of the coating solution in Table 1 was 10% by weight.

The film of the present invention can be suitably used for, for example, LCDs, PDPs, organic ELs, and other optical applications for producing display members, and applications that place importance on visibility.

Claims (1)

Formula (1) and on at least one surface of a polyester film stretched in at least one direction comprising simultaneously satisfying amounts of titanium compound and phosphorus compound (2), containing Nagy imide compound having an aromatic compound in the molecule A laminated polyester film comprising a coating layer.
1 ≦ W _Ti ≦ 20 (1)
1 ≦ W _P ≦ 300 (2)
(In the _{formula, W Ti} titanium element content in the polyester film (ppm), _{W P} denotes phosphorus element content in the polyester film (ppm))