JP2009214354A - Laminated optical polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical laminated polyester excellent in visibility when used as a display member such as a display, particularly in black color reproducibility, excellent in prevention of scratches, workability, productivity, and adhesion to a hard coat layer. Provide film.
SOLUTION: At least one surface of a laminated film comprising at least three or more polyester layers containing particles in both outermost layers has a coating layer provided in the film forming step of the laminated film, and the coating layer An optically laminated polyester film having an absolute reflectance of 4.0% or more for an arbitrary wavelength of 400 to 800 nm and an SCE value of 550 nm of 0.60% or less.
[Selection figure] None

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 It is related with the laminated polyester film for optics excellent in adhesiveness.

  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, including 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. It is widely used in various optical applications such as a protective film for a base film provided with a functional layer.

  As an anti-reflection film, in general, high-refractive index layers and low-reflectance layers are alternately laminated as a surface functional layer to prevent reflection of external light and indoor fluorescent lamps by utilizing the light interference phenomenon. The method to do is adopted.

In recent years, there has been a demand for larger screens, higher image quality, and higher grades in applications such as LCD and PDP display members, 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 are mainly three-wavelength fluorescent lamps due to daylight color reproducibility, making interference unevenness more visible, and the optical design of the coating layer laminated on the polyester film has become important. Yes. Further, it is important to reduce optical defects as a display member. Conventionally, a method of adding lubricant particles has been used to prevent scratches on the film surface. However, as the amount of lubricant particles added increases, Clearness is impaired and black color reproducibility is lowered, which is a problem.
JP 2003-48289 A JP 2007-130956 A

  The present invention has been made in view of the above circumstances, and its solution is less interference unevenness due to reflection of external light when used as a display member, excellent black color reproduction, damage prevention, work It is to provide a useful film having excellent properties and adhesion to a hard coat layer.

  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 comprising at least three polyester layers containing particles in both outermost layers has a coating layer provided in the film-forming process of the laminated film. The laminated polyester film for optics, wherein the coating layer has an absolute reflectance of 4.0% or more with respect to an arbitrary wavelength of 400 to 800 nm, and an SCE value of 550 nm is 0.60% or less. Exist.

Hereinafter, the present invention will be described in detail.
It is an essential requirement that the laminated polyester film for optics of the present invention is a multilayer film having at least three 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.

  The film of the present invention has a coating layer as described later, but the SCE value at a wavelength of 550 nm on the coating layer surface needs to be 0.60% or less, preferably 0.59% or less, more preferably Is 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 absolute reflectance on the side of the coating layer provided on at least one side of the optically laminated polyester film of the present invention is 4.0% or more, preferably 4.5% or more at an arbitrary wavelength of 400 to 800 nm. It is preferably less than the absolute reflectivity of the polyester film without laminating the layers. When the absolute reflectance is less than 4.0%, interference unevenness is caused by deterioration of the antireflection function when a surface functional layer such as a hard coat layer or an antireflection layer is provided on the coating layer of the film. It may become stronger and visibility may be reduced.

  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. If the thickness is less than 3 μm, the oligomer (cyclic trimer) contained in the inner layer may be deposited on the film surface due to heat history during processing, etc., and production line contamination and film haze may deteriorate. If the thickness is more than 1/4 of the thickness, the haze value (particularly the internal haze value) due to the lubricant particles blended in the outermost layer film is increased to improve the roll-up property of the film, and the transparency of the film is deteriorated. Tend.

  In the outermost layer of the polyester film of the present invention, particles are blended 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 content of particles 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 to improve 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 in the present invention, the absolute reflectance is an arbitrary wavelength having a wavelength of 400 to 800 nm. It is an essential requirement to have a coating layer of 4.0% or more at a wavelength of.

  As the coating layer, a binder polymer is used to improve antireflection performance and transparency when various surface functional layers are laminated on the coating layer, and to improve adhesion to various surface functional layers. Is preferred.

  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 defined as a polymer compound having a film forming property of 1000 or more.

  Specific examples of the binder polymer include polyester resin, acrylic resin, urethane resin, polyvinyl, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, and starches. Polyester resin, acrylic resin, and urethane resin are more preferably used in terms of improving adhesion with the surface functional layer, and aromatic compounds are contained in these compounds in that the absolute reflectance can be designed to be high. Is more preferable.

  Furthermore, in the coating layer, a crosslinking agent may be used in combination as long as the gist of the present invention is not impaired, and various known resins can be used, but at least one selected from melamine compounds, epoxy compounds, oxazoline compounds, and isocyanate compounds. Preferably it is a seed. A melamine compound is more preferable in that it can be designed with a high absolute reflectance.

  Examples of the melamine compound in the present invention include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. .

  In addition, a coupling agent such as a metal chelate compound can be used in the coating layer. Specifically, titanium acetylacetonate, titanium ethylacetoacetate, titanium octanediolate, titanium lactate, titanium triethanolaminate. And titanium compounds such as titanium oxalate, or zirconium compounds such as zirconium acetylacetonate, zirconium ethyl acetoacetate, zirconium acetate, and zirconium stearate.

  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 improving agent, a thickener, an organic lubricant, an antistatic agent, an antioxidant, a foaming agent, a dye, and the like are contained as necessary. Also good.

  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. In addition, a small amount of an organic solvent may be contained in the coating solution for the purpose of improving the dispersibility in water, improving the film forming property, and the like within the range not impairing the gist of the present invention. 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.

  Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. 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.

  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.

  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 and 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 added to the polyester as necessary.

  According to the polyester film of the invention, there is little interference unevenness due to reflection of external light when used as a display member, excellent black color reproducibility, scratch prevention, workability, and excellent adhesion to the hard coat layer. A useful film can be provided, 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 a hard coat resin, 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, dried at 80 ° C. for 1 minute, and solvent. Was removed. 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) Method of measuring absolute reflectance minimum value on coating layer surface In advance, a black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) is pasted on the measurement back surface of the polyester film, and a spectrophotometer (UV manufactured by Shimadzu Corporation) is used. -3100PC type) was used to measure the absolute reflectance of the coating layer surface at an incident angle of 5 °, a wavelength range of 400 to 800 nm, a sampling pitch of 1 nm, a slit width of 2 nm, and a low scanning speed, and the minimum value was evaluated.

(10) Evaluation method of interference unevenness As in (5) above, a hard coat layer is provided, and the hard coat surface of the obtained hard coat film is visually observed under a three-wavelength fluorescent lamp, If the visibility was good, it was rated as ◯, and if it was confirmed that the visibility was deteriorated, it was marked as x.

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., limiting viscosity 0.75, oligomer (cyclic trimer) content 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.

The compounds constituting the coating layer are as follows.
(Coating agent adjustment)
Polyester resin: (a1)
Water dispersion of polyester resin copolymerized with the following composition: terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / ethylene glycol / 1,4-butanediol / diethylene glycol = 28/20/2/35/10/5 ( mol%)

Polyester resin: (a2)
Aqueous dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / diethylene glycol = 84 / 13/3 // 80/20 (mol%)

Urethane resin: (b)
A urethane resin water-based paint obtained by the following method was used. That is, first, a polyester polyol comprising 664 parts of terephthalic acid, 631 parts of isophthalic acid, 472 parts of 1,4-butanediol, and 447 parts of neopentyl glycol was obtained. Next, 321 parts of adipic acid and 268 parts of dimethylolpropionic acid were added to the obtained polyester polyol to obtain a pendant carboxyl group-containing polyester polyol A. Further, 160 parts of hexamethylene diisocyanate was added to 1880 parts of the above polyester polyol A to obtain an aqueous urethane resin paint.

Acrylic resin: (c)
Emulsion polymer of methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant)

Hexamethoxymethylmelamine: (d)
Titanium compound: (e1) Titanium triethanolamine Titanium compound: (e2) Titanium lactate Particles: (f) Silica sol having an average particle diameter of 65 nm Coating liquid I: (a1) / (b) / (e1) / (e2) / ( f) = 40/12/30/15/3
Coating liquid II: (a2) / (b) / (d) / (f) = 35/32/30/3
Coating liquid III: (a1) / (c) / (d) / (f) = 47/20/30/3

Example 1:
Two extruders using a mixed raw material in which the polyesters (B) and (C) are mixed at a ratio of 95% and 5%, respectively, as a raw material for the A layer and a raw material of 100% polyester (A) as the raw material for the B layer. Each was supplied to each and melted at 285 ° C., then the A layer was the outermost layer (surface layer), the B layer was the intermediate layer, and the two layers and three layers (ABA) were formed on a casting drum cooled to 40 ° C. A non-oriented sheet was obtained by coextrusion and cooling and solidification so that the composition ratio was A: B: A = 5: 90: 5. 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. Aqueous coating solution I with adjusted concentration of the solution was applied, 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 40 m / min. A laminated polyester film having a thickness of 100 μm and a film haze of 0.5% having coating layers on both sides was obtained. 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, the raw material of layer A was polyester (B) / polyester (C) = 97.5 / 2.5, and the coating liquid was changed to aqueous coating liquid II. A film was obtained. 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 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.

Comparative Example 5:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating liquid I was changed to the coating liquid III. The obtained film had a film haze of 0.5%, and the surface had almost no scratches visible under a three-wavelength fluorescent lamp.

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

Claims (1)

At least one surface of a laminated film comprising at least three or more polyester layers containing particles in both outermost layers has a coating layer provided in the film forming step of the laminated film, and the absolute reflectance of the coating layer Is 4.0% or more with respect to an arbitrary wavelength of 400 to 800 nm, and the SCE value at 550 nm is 0.60% or less.