JP2009214353A - Laminated optical polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a useful film which is excellent in visibility when used as a display member, black color taste reproducibility in particular, damage preventing properties, workability, adhesion to a hard coat layer, and durability when used outdoors. <P>SOLUTION: In a laminated optical polyester film, particles are contained in both outermost layers, an ultraviolet absorber is contained in one layer excluding both outermost layers, on at least one side of a laminated film composed of at least three polyester layers, a coating layer installed in a laminated film forming process is provided, and the SCE value of 550 nm of the surface of the coating layer is 0.60% or below. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical laminated polyester film, and in particular, is excellent in visibility when used as a display member such as a display, in particular, black color reproducibility, prevention of scratches, workability, productivity, hard coat layer In addition, the present invention relates to a laminated polyester film for optics that is excellent in durability in outdoor use.

  Biaxially stretched polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, chemical resistance, etc., packaging materials, electrical insulation materials, metal deposition materials, plate making materials, magnetic recording materials, It is used in many applications such as display materials, transfer materials, and window paste materials.

  In particular, for anti-static, anti-reflection, and electromagnetic wave shields for pasting front panel glass surfaces of so-called flat displays such as transparent touch panels and base films for prism sheets used in liquid crystal display devices, cathode ray tubes, LCDs, and PDPs. Although it is widely used for various optical uses such as for a base film of a protective film provided with a functional layer such as a polyester film, since a polyester film is easily scratched, there is a drawback that appearance and optical characteristics are easily impaired. In addition, in portable information terminals, mobile phones, and portable game machines, which have recently been increasing in demand, light weight and downsizing and high functionality such as TV function and video playback display are remarkable, optical defects such as scratches are less, and high definition. In addition, high-quality color reproducibility is required.

  Conventionally, a method of adding lubricant particles has been used to prevent scratches on the film surface, but when the amount of lubricant particles added increases, the clearness of the display member disappears, and the black color reproducibility decreases. It is a problem.

In addition, PDAs, mobile phones, portable game machines, and the like have increased opportunities to use outdoors, and the time for direct exposure to sunlight has increased. Sun rays contain ultraviolet rays that degrade the thermoplastic resin film, and when exposed to sunlight for a long time, the films deteriorate, causing problems in visibility and adhesion of the laminate, and the film substrate itself is yellow. A changing problem arises.
JP 2003-48289 A

  The present invention has been made in view of the above circumstances, and its solution is excellent in visibility when used as a display member, particularly black color reproduction, scratch prevention, workability, and hard coat layer. It is to provide a useful film excellent in adhesiveness and durability in outdoor use.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problems can be easily solved by a polyester film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is that at least one side of a laminated film composed of at least three or more polyester layers containing particles in both outermost layers and containing an ultraviolet absorber in one of the layers other than both outermost layers, It has the coating layer provided in the film forming process of the said laminated | multilayer film, and exists in the laminated polyester film for optics characterized by the SCE value of wavelength 550nm of the said coating layer surface being 0.60% or less.

Hereinafter, the present invention will be described in detail.
The optical laminated polyester film of the present invention is preferably a multilayer film having at least 3 layers. The laminated polyester film for optics referred to in the present invention is a polyester film extruded by a so-called extrusion method that is melt-extruded from an extrusion die, and is oriented in the biaxial direction of the vertical direction and the horizontal direction as necessary. Film.

  In the present invention, the polyester is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. 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 polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN) and the like.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a copolyester, it is a copolymer containing 30 mol% or less of the third component. Examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acids (for example, P-oxybenzoic acid). Or 2 or more types are mentioned, As a glycol component, 1 type, or 2 or more types, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, are mentioned.

  As will be described later, the film of the present invention has a coating layer on at least one surface of the film, and the SCE value at a wavelength of 550 nm on the surface of the coating layer needs to be 0.60% or less, preferably 0.59. % Or less, more preferably 0.58% or less. The film of the present invention is widely used in optical applications because of its excellent transparency. However, when the SCE value exceeds 0.60%, black color reproducibility is inferior, and it is not suitable as an optical display member. It becomes appropriate.

  The film of the present invention contains an ultraviolet absorber in an amount of usually 0.20 to 10.0% by weight, preferably 0.30 to 1.8% by weight in order to improve durability when used outdoors. To do. When the ultraviolet absorber is less than 0.10% by weight, the polyester film may be deteriorated by ultraviolet rays, and the life of the optical product may be shortened. On the other hand, when an ultraviolet absorber in an amount exceeding 10.0% by weight is contained, the ultraviolet absorber migrates or bleeds out on the surface, and the adhesiveness with the functional layer formed on the surface of the polyester film decreases, The surface functionality may be deteriorated due to white turbidity.

  In the film of the present invention, the light transmittance at a wavelength of 380 nm is usually 5.0% or less, preferably 2.0% or less, more preferably 1.0% or less. When the light transmittance at a wavelength of 380 nm is greater than 5.0%, the effect of preventing deterioration of the electronic ink layer and the pressure-sensitive adhesive layer that bonds the functional sheets to each other due to ultraviolet rays transmitted through the polyester film is not sufficiently exhibited. Sometimes.

  Examples of ultraviolet absorbers include benzophenone compounds, 1,3,5-triazine compounds, benzoxazinone compounds, and the like, which can be used alone or in combination of two or more. In consideration of this, a benzoxazinone-based compound that is difficult to be yellowed is preferably used.

  An example of a benzoxazine-based compound used as an ultraviolet absorber is 2,2- (1,4-phenylene) bis [4H-3,1-benzoxazin-4-one].

  The total film thickness of the film of the present invention is usually 50 to 300 μm or more, preferably 75 to 250 μm. If the total film thickness is less than 50 μm, the film is weak, so after punching into a single sheet, the workability at the time of final inspection performed for each sheet or sticking to a display tends to be worse, from 300 μm If it is thick, workability may deteriorate due to its rigidity.

The film of the present invention preferably has an oligomer precipitation amount of 15.0 mg / m ² or less on the film surface in order to improve the durable adhesion of the hard coat layer.

  In order to make the oligomer precipitation amount on the film surface by heat processing into said range, the method of using polyester with little oligomer content is mentioned. Moreover, in the case of the laminated film by coextrusion, the oligomer precipitation amount on the film surface after heat processing can be suppressed to said range by using polyester with little oligomer content for outermost layer. Specifically, by setting the amount of oligomer contained in the polyester film to 5000 ppm or less, further 4000 ppm, particularly 3000 ppm or less, oligomers that deposit on the film surface when heated can be prevented.

  It is known that the oligomer in the polymer increases due to the melting step in film formation, and the increase is strongly influenced by the water content in the polymer, the temperature at the time of melting, the residence time, etc. It is considered to increase by about ˜5000 ppm.

  As a method for reducing the amount of oligomer in the polyester, conventionally known solid phase polymerization can be used.

  In the case of a film having a laminated structure, the outermost layer thickness is a thickness on one side only, usually 3 μm or more, and preferably ¼ or less of the total thickness. When the thickness is less than 3 μm, oligomers (cyclic trimers) and UV absorbers contained in the inner layer are deposited on the film surface due to heat history during processing, etc., and production line contamination and film haze deteriorate. If the thickness is more than 1/4 of the total thickness, the haze value (especially the internal haze value) due to the lubricant particles blended in the outermost layer film is increased to improve the winding property of the film, and the film is transparent. There is a tendency to deteriorate.

  Particles are blended in the polyester layer of the film of the present invention mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. 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, etc. These series of particles may be used in combination of two or more as required.

  The average particle size of the particles to be blended in the polyester film is not particularly limited, but is usually in the range of 0.02 μm to 3 μm, preferably 0.02 μm to 2.5 μm, more preferably 0.02 μm to 2 μm. It is. When particles having an average particle size of less than 0.02 μm are used, sufficient slipperiness cannot be imparted, so that the winding characteristics in the film production process tend to be inferior. On the other hand, when the average particle diameter exceeds 3 μm, the degree of roughening of the film surface becomes too large and the film may become hazy.

  Furthermore, the particle content in the polyester layer is usually in the range of 0.0005 to 0.5% by weight, preferably 0.001 to 0.3% by weight. When the particle content is less than 0.0005% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 0.5% by weight, the transparency of the film is insufficient. There are cases.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage of producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction, The polycondensation reaction may proceed. 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.

  Hereinafter, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

  Polyester chips dried by a known method are supplied to a melt extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer to melt. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  The polyester film of the present invention is used with a hard coat layer provided for improving the surface hardness. In this case, since the polyester film is generally inactive, the adhesiveness is poor, and in order to improve the adhesiveness with the hard coat layer, it is necessary to provide a coating layer for improving the adhesiveness in advance. is there.

As a method for forming such a coating layer, a so-called in-line coating method in which coating is performed before the tenter entrance (before completion of orientation crystallization) and drying is performed in the tenter is preferable.
The coating layer for improving the adhesion with the hard coat layer is not particularly limited as long as it improves the adhesion, but a binder resin as described in JP-A-2003-201357. A combination of and a crosslinking agent is preferred.

  In the present invention, it is preferable to contain inorganic particles or organic particles in the coating layer in order to further improve the slipperiness, adhesion and the like. The amount of the particles in the coating agent is usually 0.5 to 10% by weight, preferably 1 to 5% by weight. When the blending amount is less than 0.5% by weight, the blocking resistance may be insufficient. When the blending amount exceeds 10% by weight, the transparency of the film is hindered and the sharpness of the image tends to be lowered.

  Examples of the inorganic particles include silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black, molybdenum sulfide, and antimony oxide. Among these, silicon dioxide is easy to use because it is inexpensive and has various particle sizes.

  Examples of the organic particles include polystyrene or polyacrylate polymethacrylate in which a crosslinked structure is achieved by a compound (for example, divinylbenzene) containing two or more carbon-carbon double bonds in one molecule.

  The above inorganic particles and organic particles may be surface-treated. Examples of the surface treatment agent include a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, and the like. The content of the particles in the coating layer is preferably 10% by weight or less, more preferably 5% by weight or less as an appropriate addition amount that does not impair the transparency.

  The coating layer may contain an antifoaming agent, a coating property improving agent, a thickener, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like.

  As long as water is the main medium, the coating agent may contain a small amount of an organic solvent for the purpose of improving dispersion in water or improving the film-forming performance. It is necessary to use the organic solvent as long as it is soluble in water. Examples of the organic solvent include aliphatic or alicyclic alcohols such as n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, and methyl alcohol, glycols such as propylene glycol, ethylene glycol, and diethylene glycol, n-butyl cellosolve, Examples include glycol derivatives such as ethyl cellosolve, methyl cellosolve, propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and amyl acetate, ketones such as methyl ethyl ketone and acetone, and amides such as N-methylpyrrolidone. Can be mentioned. These organic solvents may be used in combination of two or more as required.

  Moreover, you may perform various coatings by offline coating after manufacture of a film as needed. Such a coat may be either single-sided or double-sided. The coating material may be either water-based and / or solvent-based for off-line coating, but is preferably water-based or water-dispersed for in-line coating.

  In addition, when the polyester film of the present invention is used for optics, an antistatic agent, a colorant, a conductive material, etc. may be added for the purpose of imparting other functionality to the hard coat layer provided for improving the surface hardness. In addition, a functional multilayer thin film may be formed thereon for the purpose of reflection of external light, electric shock due to static electricity, dust adhesion prevention, and electromagnetic wave shielding.

  The coating liquid used in the present invention is preferably an aqueous solution or an aqueous dispersion in terms of handling and working environment, but contains water as the main medium and contains an organic solvent as long as it does not exceed the gist of the present invention. You may do it.

  Although there is no restriction | limiting in particular in the solid content density | concentration of a coating liquid, Usually, 0.3 to 65 weight%, Preferably it is 0.5 to 30 weight%, More preferably, it is 1 to 20 weight%. When the concentration is too high or too low than these ranges, it may be difficult to provide a coating layer having a thickness necessary for fully expressing the function.

  The thickness of a coating layer is dry thickness, and is 0.003-1.5 micrometers normally, Preferably it is 0.01-0.5 micrometer, More preferably, it is 0.01-0.3 micrometer. If the thickness of the coating layer is less than 0.003 μm, sufficient performance may not be obtained, and if it exceeds 1.5 μm, blocking between films tends to occur.

  As a coating method of the coating agent, for example, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating apparatus other than these as shown in Yuji Harasaki, Tsuji Shoten, published in 1979, “Coating Method” Can be used.

  The polyester film of the present invention can be mixed with other thermoplastic resins such as polyethylene naphthalate and polytrimethylene terephthalate as long as the effects of the present invention are not impaired. Moreover, you may mix | blend coloring agents, such as a ultraviolet absorber, antioxidant, surfactant, a fluorescent whitening agent, a lubricant agent, a light-shielding agent, a matting agent, and a dye, a pigment. In addition, for the purpose of improving the slipperiness and abrasion resistance of the film, inert inorganic or organic fine particles can be blended with the polyester as necessary.

  According to the polyester film of the present invention, a useful film having excellent visibility as a display member, black color reproducibility, less damage to the film surface, excellent workability, and weather resistance for outdoor use. 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. In the examples and comparative examples, “parts” means “parts by weight”. The measuring method used in the present invention is 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) Average particle diameter (d50)
The particle size was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation.

(3) Content of oligomer (cyclic trimer) in polyester After a predetermined amount of polyester raw material or polyester film was dissolved in o-chlorophenol, it was reprecipitated with tetrahydrofuran and filtered to remove linear polyethylene terephthalate. After that, the filtrate obtained was supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer (cyclic trimer) contained in the polyester, and this value was divided by the amount of polyester used for the measurement. The amount of oligomer contained in the polyester (cyclic trimer). 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 accurately weighing an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF (dimethylformamide).

The conditions of 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) Thickness of Laminated Polyester Layer After fixing a small piece of film with an epoxy resin, it was cut with a microtome, and the cross section of the film was observed with a transmission electron micrograph. Two of the cross-sections are observed in parallel with the film surface, and the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was defined as the laminated thickness.

(5) Hard coat adhesion The hard coat resin was applied on the coating layer of the obtained film so that the thickness after curing was 3 μm, and the irradiation distance was 150 mm using a high-pressure mercury lamp with an energy of 120 W / cm. Was irradiated for about 15 seconds to obtain a hard coat film. As the hard coat layer resin, a composition comprising 30 parts of dipentaerythritol hexaacrylate, 40 parts of tetrafunctional urethane acrylate, 27 parts of bisphenol A type epoxy acrylate and 3 parts of 1-hydroxycyclohexyl phenyl ketone was used. The hard coat layer was cross-cut so that there were 100 grids in a 1-inch width. Immediately after that, a rapid peel test with a cello tape (registered trademark) was performed three times at the same location, and the peel area was evaluated. The judgment criteria are as follows.

○: Number of cross cuts = 0
Δ: 1 ≦ number of cross-cuts ≦ 20
×: 21 <Number of cross-cuts peeled

(6) Film haze Turbidity was measured with an integrating sphere turbidimeter NDH manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K 7136.

(7) SCE value A black tape manufactured by Nichiban Co., Ltd. was attached to the back surface of the measurement surface, and an SCE value of 550 nm was measured using a spectrocolorimeter CM-3700d manufactured by Konica Minolta.

(8) Black color evaluation A black tape manufactured by Nichiban Co., Ltd. was applied to the back of the hard coat layer of the hard coat film obtained by the same method as in (5) above, and the black on the hard coat surface side under an indoor fluorescent lamp. The color was visually judged according to the following criteria.
○: Clear feeling and vivid black color ×: No clear feeling, black color is blurred

(9) Light Transmittance Using a spectrophotometer UV3100 manufactured by Shimadzu Corporation, the light transmittance is measured continuously at a scanning speed of 2 nm, a sampling pitch of 2 nm, and a wavelength range of 300 to 700 nm. Detected.

(10) Weather resistance Ultraviolet long life fade meter (FAL-3 type) manufactured by Suga Test Instruments Co., Ltd. was used and irradiated with ultraviolet rays at 63 ± 3 ° C. for 1000 hours. The appearance of the film after the test was observed and evaluated according to the following criteria.
○: No deterioration △: Slightly yellow ×: Yellowing deterioration is conspicuous

The production method of the polyester used in the following examples and comparative examples is as follows.
<Manufacture of polyester>
[Method for producing ester (A)]
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out 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 tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (A) was 0.63, and the content of the oligomer (cyclic trimer) was 0.83% by weight.

[Production method of polyester (B)]
Polyester (A) is pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C., and has an intrinsic viscosity of 0.75 and an oligomer (cyclic trimer) content of 0.24% by weight. Polyester (B) was obtained.

[Production method of polyester (C)]
In the method for producing polyester (A), after adding 0.04 part of ethyl acid phosphate, 0.2 part of silica particles dispersed in ethylene glycol having an average particle diameter of 1.6 μm and 0.04 part of antimony trioxide are added. In addition, polyester (C) was obtained using the same method as the production method of polyester (A) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.65. The obtained polyester (C) had an intrinsic viscosity of 0.65 and an oligomer (cyclic trimer) content of 0.82% by weight.

<Method for producing polyester (D)>
The polyester (A) was subjected to a twin-screw extruder with a vent, and 2,2- (1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] (CYTECOR manufactured by CYTEC Co., Ltd.) as an ultraviolet absorber. UV-3638 (molecular weight 369 benzoxazine) was supplied to a concentration of 10% by weight and melt-kneaded to form chips, thereby preparing an ultraviolet absorbent master batch polyester (D). The intrinsic viscosity of the obtained polyester (D) was 0.59.

(Coating agent adjustment)
Aqueous coating solution a
(Terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / ethylene glycol / 1,4-butanediol / diethylene glycol = polyester dispersion at 28/20/2/35/10/5 molar ratio) / (methyl methacrylate / Emulsion polymer of ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 molar ratio [emulsifier = anionic surfactant] / hexamethoxymethylmelamine / silica sol having an average particle size of 0.08 μm as a solid content An aqueous coating solution containing 47/20/30/3 in terms of weight ratio in terms of weight.

Example 1:
A mixed raw material in which the polyesters (B) and (C) were mixed at a ratio of 95% and 5%, respectively, was used as a raw material for the A layer, and the polyesters (A) and (D) were mixed at a ratio of 94% and 6%, respectively. Casting drums with the raw material as the raw material for layer B, each supplied to two extruders, melted at 285 ° C., and then cooled to 40 ° C. with layer A as the outermost layer (surface layer) and layer B as the intermediate layer Above, it was coextruded so as to have a thickness composition ratio of A: B: A = 5: 90: 5 with two types and three layers (ABA), and cooled and solidified to obtain an unoriented sheet. Next, the film is stretched 3.4 times in the machine direction at a film temperature of 82 ° C. using the roll peripheral speed difference, and then the coating amount after transverse stretching and drying is 0.1 g / m ^{2 on} both surfaces of the machined film. After applying the aqueous coating agent a with the adjusted concentration of the solution, it was led to a tenter, stretched 3.7 times at 120 ° C in the transverse direction, heat treated at 230 ° C, and then relaxed at 0% in the transverse direction. The rail width was fixed, and the film was rolled up at a production rate of 30 m / min to obtain a laminated polyester film having a thickness of 125 μm and a film haze of 0.5% having coating layers on both sides. The surface of the obtained film had almost no scratches visible under a three-wavelength fluorescent lamp. The evaluation results are shown in Table 1 below.

Example 2:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the raw material for the A layer was polyester (B) / polyester (C) = 97.5 / 2.5. The film obtained had a film haze value of 0.4%, and the surface had almost no scratches visible under a three-wavelength fluorescent lamp.

Comparative Example 1:
In Example 1, the polyester film was obtained by the same method as Example 1 except having made the raw material of the A layer into polyester (B) / polyester (C) = 80/20. The obtained film had a film haze of 1.1%, and the surface had almost no scratches visible under a three-wavelength fluorescent lamp.

Comparative Example 2:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the raw material for the A layer was polyester (B) / polyester (C) = 87.5 / 12.5. The film obtained had a film haze of 0.7%, and the surface had almost no scratches visible under a three-wavelength fluorescent lamp.

Comparative Example 3:
In Example 1, the polyester film was obtained by the same method as Example 1 except having made only the polyester (B) the raw material of A layer. The film obtained had a film haze of 0.3%, and had many scratches visible on the surface under a three-wavelength fluorescent lamp, making it inferior as an optical film.

Comparative Example 4:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the raw material for layer B was 100% polyester (A). The obtained film had a film haze of 0.5%, and the surface had almost no scratches visible under a three-wavelength fluorescent lamp.

Comparative Example 5:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating liquid a was not applied. The obtained film had a film haze of 0.5%, and the surface had almost no scratches visible under a three-wavelength fluorescent lamp.
<Table 1>

  The film of the present invention can be suitably used as a display member such as a display, for example.

Claims (1)

In the film forming process of the laminated film on at least one side of a laminated film comprising at least three polyester layers containing particles in both outermost layers and containing an ultraviolet absorber in one of the layers other than both outermost layers. A laminated polyester film for optics, which has a coating layer provided in (1) and has an SCE value at a wavelength of 550 nm on the surface of the coating layer of 0.60% or less.