JP5726925B2 - Laminated polyester film - Google Patents

Description

The present invention relates to a laminated polyester film, for example, a substrate with a transparent electrode such as a solar cell, a flexible display, an organic EL lighting, a touch panel, etc., and has high transparency and heat resistance excellent in dimensional stability after heat treatment. It is related with the laminated polyester film suitable for the use for which is required.

  In recent years, polyester films are often used for various optical films and molding films. Transparent electrodes such as touch panels, which are members of various displays, antireflection films, prism sheets, light diffusion sheets, electromagnetic wave shielding films, It is used for applications such as mold transfer films, in-mold label films, and back sheet films for solar cells.

  In addition, for substrates used in lighting, display members, solar cells, flexible displays, organic EL lighting, touch panels, etc., front sheets, back sheets, etc., in addition to transparency, lightness, flexibility, high heat resistance, etc. Various performances are required.

  Conventionally, glass has been used as a substrate material such as a solar cell and various display elements such as an organic EL. However, glass not only has drawbacks such as being easily broken, heavy, and difficult to reduce the thickness, but the glass does not have a sufficient material for reducing the thickness and weight of the display in recent years and making the display flexible. Therefore, a thin and lightweight transparent resin-made film-like substrate has been studied as an alternative material to replace glass.

  In such an application, when a film-like resin substrate is used, the film is required to have high heat resistance. For example, when a circuit such as a TFT is formed on a film, the film is required to have high dimensional stability at around 200 ° C., which is the heat treatment temperature of the TFT, in order not to cause a pattern shift during circuit formation. However, the conventional normal polyester film has insufficient dimensional stability in a high temperature atmosphere of 150 ° C. or higher (specifically, 150 ° C. to 200 ° C.).

  In order to solve these problems, a method for forming a heat-resistant resin layer on a film (Patent Document 1) and a method for forming a cured resin coating film (Patent Document 2) have been proposed. However, the dimensional stability may not be sufficient in a high temperature and long-time atmosphere, and cannot be used for applications that require higher dimensional stability.

  In recent years, in order to improve the performance of the film such as curling prevention, damage prevention, and surface hardness, hard coating is often used. In order to improve the adhesion between the polyester film used as a substrate and the hard coat layer, an easily adhesive coating layer is generally provided as an intermediate layer. Therefore, interference unevenness occurs without considering the refractive index of the three layers of the polyester film, the easy-adhesion coating layer, and the hard coat layer, which may result in a film with poor visibility.

  If a film with interference unevenness is used, the visibility becomes poor and it is difficult to use. Therefore, it is required to take measures against interference unevenness. In general, the refractive index of the coating layer for reducing interference unevenness is considered to be around the geometric mean of the refractive index of the polyester film of the substrate and the refractive index of the hard coat layer, and is adjusted to the refractive index around this. Ideally.

JP 2001-277455 A Japanese Patent No. 2952769

  This invention is made | formed in view of the said situation, The solution subject is providing the laminated polyester film which is excellent in the dimensional stability after heat processing, and there is little interference nonuniformity by external light reflection.

  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-described problems, and have completed the present invention.

That is, the gist of the present invention is an active energy ray-curable material having a coating layer having a film thickness of 0.04 to 0.20 μm on at least one surface of a polyester film, and having fine particles and a cyclic structure on the coating layer . It exists in the laminated polyester film characterized by having the layer containing the polymeric hardened | cured material of the composition containing (meth) acrylate more than bifunctional .

  According to the laminated polyester film of the present invention, it is possible to provide a film having high transparency, good dimensional stability after heat treatment, and less interference unevenness due to external light reflection, and its industrial value is high.

  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, 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 acid (for example, p-oxybenzoic acid). 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.

  In consideration of dimensional stability due to heating, it is preferable that the amount of components to be copolymerized is small, and the ratio thereof is 20% by weight or less, more preferably 10% by weight or less, and further preferably 5% by weight or less in the polyester film. It is. More preferable polyester films are a polyethylene terephthalate film and a polyethylene naphthalate film, and among them, a polyethylene terephthalate film is more preferable in view of ease of manufacture and cost.

  There is no restriction | limiting in particular as a polymerization catalyst of polyester, A conventionally well-known compound can be used, For example, an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, a calcium compound etc. are mentioned. Among these, antimony compounds have the advantage of being inexpensive and having high catalytic activity. Titanium compounds and germanium compounds are preferable because they have high catalytic activity and can be polymerized in a small amount, and since the amount of metal remaining in the film is small, the brightness of the film is increased. Furthermore, since a germanium compound is expensive, it is more preferable to use a titanium compound.

  The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film and to prevent deterioration of the liquid crystal of a liquid crystal display used for a touch panel or the like. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can withstand the heat applied in the production process of the polyester film.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a cyclic imino ester type, a benzotriazole type, a benzophenone type etc. are mentioned. From the viewpoint of durability, a cyclic imino ester type and a benzotriazole type are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

  In the polyester layer of the film of the present invention, particles can be blended mainly for the purpose of imparting slidability and preventing scratches in each step, but from the viewpoint of transparency, particles are not blended. It is preferable that When the particles are blended, the kind of the particles to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples thereof include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, sulfuric acid. Examples thereof include inorganic particles such as calcium, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. 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.

  Moreover, the average particle diameter of particle | grains is 5 micrometers or less normally, Preferably it is 0.01-3 micrometers, More preferably, it is the range of 0.05-2 micrometers. When the average particle diameter exceeds 5 μm, the surface roughness of the film becomes too rough, and a problem may occur when various surface functional layers are formed in the subsequent process.

  Further, the content of particles in the polyester layer is usually less than 5% by weight, preferably in the range of 0.0003 to 3% by weight. When there are no or few particles, the transparency of the film becomes high and the film becomes a good film, but the slipperiness may be insufficient. There are cases where improvement is required. Further, when the particle content exceeds 5% by weight, the transparency of the film may be insufficient.

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 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.

  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.

  The thickness of the polyester film in the present invention is not particularly limited as long as it can be formed as a film, but is usually 2 to 300 μm, preferably 5 to 250 μm, and more preferably 10 to 100 μm.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, when producing a biaxially stretched polyester film, the polyester raw material described above is first melt extruded from a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an unstretched 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, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained 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-stage stretching direction at usually 70 to 170 ° C. and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, a method of obtaining a biaxially oriented film by performing heat treatment at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% can be mentioned. 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 270 ° C. under tension or relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  From the viewpoint of improving the dimensional stability after heat treatment, the polyester film is preferably a biaxially stretched polyester film rather than unstretched or uniaxially stretched.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. More preferably, it is formed by in-line coating.

  In-line coating is a method of coating within the process of manufacturing a polyester film, and specifically, a method of coating at any stage from melt extrusion of a polyester to heat setting after stretching and winding up. Usually, it is coated on any of an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, and a film after heat setting and before winding. Although not limited to the following, for example, in sequential biaxial stretching, a method of stretching in the transverse direction after coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) is particularly excellent. According to such a method, film formation and coating layer formation can be performed at the same time, so there is an advantage in manufacturing cost. In addition, in order to perform stretching after coating, the thickness of the coating layer can be changed by the stretching ratio. Compared to offline coating, thin film coating can be performed more easily. Further, by providing the coating layer on the film before stretching, the coating layer can be stretched together with the base film, whereby the coating layer can be firmly adhered to the base film. Furthermore, in the production of a biaxially stretched polyester film, the film can be restrained in the longitudinal and lateral directions by stretching while gripping the film end with a clip, etc. High temperature can be applied while maintaining the properties. Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer can be improved, and the coating layer and the base film can be more firmly adhered to each other. Furthermore, it can be set as a firm coating layer, and performances such as adhesion to various functional layers that can be formed on the coating layer and wet heat resistance can be improved.

  In the present invention, the polyester film has a coating layer having a film thickness of 0.04 to 0.20 μm on at least one surface, and has a layer containing a compound having fine particles and a cyclic structure on the coating layer. It is an essential requirement.

  The coating layer of the film of the present invention is an interference caused by external light reflection when a layer containing a compound having fine particles and a cyclic structure (hereinafter sometimes referred to as a functional layer) is provided on a polyester film as a substrate. It is provided to reduce unevenness and improve adhesion. If a film with strong interference unevenness is used, the visibility becomes poor and it is difficult to use. In the case of a film having poor adhesion, the functional layer may be peeled off in the heat treatment step or the wet heat treatment step, or cracks or bubbles may enter the functional layer and the appearance may deteriorate. Further, there is a concern that the dimensional stability after the heat treatment is deteriorated.

  In order to reduce interference unevenness, the thickness of the coating layer is usually in the range of 0.04 to 0.20 μm, preferably in the range of 0.05 to 0.16 μm, more preferably in the range of 0.07 to 0.13 μm. is there. When outside the above range, even if the refractive index of the coating layer is devised, interference unevenness due to external light reflection may not be reduced.

  Various polymers are usually used for forming the coating layer. Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like. . Among these, polyester resin, acrylic resin, and urethane resin are preferable from the viewpoint of improving adhesion with the functional layer and improving the appearance of coating.

  The polyester resin includes, for example, those composed of the following polyvalent carboxylic acid and polyvalent hydroxy compound as main constituent components. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. As the polyvalent hydroxy compound, ethylene Recall, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol , Neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol Polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, and the like can be used. One or more compounds may be appropriately selected from these compounds, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  The acrylic resin is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included. Moreover, in order to improve adhesiveness, it is also possible to contain a hydroxyl group and an amino group.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

  The urethane resin is a polymer compound having a urethane bond in the molecule. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.).

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Among the above polyols, polycarbonate polyols and polyester polyols are more preferably used in order to improve adhesion to the functional layer.

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexa And alicyclic diamines such as

  The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the structure of a urethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency, and adhesion of the resulting coating layer.

Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred.
For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  Among the above-mentioned polymers, in particular, from the viewpoint that a large number of aromatic compounds such as a benzene ring can be contained in the molecule, the refractive index can be increased, and the refractive index of the coating layer can be easily adjusted. Polyester resins are preferred.

  Further, the refractive index of the coating layer is further increased in order to make it easier to adjust, for example, naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c It is preferable to use a compound having a condensed polycyclic aromatic structure such as phenanthrene or perylene.

  In consideration of applicability on the polyester film, the compound having a condensed polycyclic aromatic is preferably a polymer compound such as a polyester resin, an acrylic resin, or a urethane resin. In particular, polyester resins are more preferable because more condensed polycyclic aromatics can be introduced.

  As a method of incorporating the condensed polycyclic aromatic into the polyester resin, for example, two or more hydroxyl groups are introduced into the condensed polycyclic aromatic as a substituent to form a diol component or a polyvalent hydroxyl component, or There is a method in which two or more acid groups are introduced to prepare a dicarboxylic acid component or a polyvalent carboxylic acid component.

  In the laminated polyester film manufacturing process, the condensed polycyclic aromatic used for forming the coating layer is preferably a compound having a naphthalene structure in that it is difficult to be colored. In addition, a resin in which a naphthalene structure is incorporated as a polyester component is preferably used in terms of good adhesion to a functional layer formed on the coating layer and transparency. Representative examples of the naphthalene structure include 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

  In addition to the hydroxyl group and the carboxylic acid group, the condensed polycyclic aromatic has a refractive index of a refractive index by introducing a substituent containing a sulfur element, an aromatic substituent such as a phenyl group, a halogen element group, and the like. Improvements can be expected, and substituents such as alkyl groups, ester groups, amide groups, sulfonic acid groups, carboxylic acid groups, and hydroxyl groups may be introduced from the viewpoint of coating properties and adhesion.

  Moreover, it is preferable to use a crosslinking agent in combination in order to strengthen the coating layer and improve adhesion and heat and heat resistance. A conventionally well-known material can be used with a crosslinking agent, For example, an oxazoline compound, an isocyanate type compound, a carbodiimide type compound, an epoxy compound, a melamine compound, a silane coupling compound etc. are mentioned. Among these crosslinking agents, an oxazoline compound, an isocyanate compound, a carbodiimide compound, and an epoxy compound are preferable from the viewpoint that adhesion after heat-resistant heat treatment is improved. Moreover, adhesiveness may improve more by using 2 or more types of crosslinking agents together. On the other hand, a melamine compound is preferable from the viewpoint of increasing the refractive index of the coating layer.

  The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  The content of the oxazoline group contained in the oxazoline compound is usually 0.5 to 10 mmol / g, preferably 1 to 9 mmol / g, more preferably 3 to 8 mmol / g, and further preferably 4 to 6 mmol in terms of the amount of the oxazoline group. / G. Use in the above range is preferable because adhesion to the prism layer and the microlens layer is improved.

  The isocyanate compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When used in the state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compound, methyl isobutanoyl acetate, ethyl isobutanoyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, ethyl acetoacetate, mercaptan compounds such as butyl mercaptan, dodecyl mercaptan, ε-caprolactam, δ -Lactam compounds such as valerolactam, amine compounds such as diphenylaniline, aniline, and ethyleneimine, acetanilide, acetic acid acetate Examples include amide acid amide compounds, formaldehyde, acetoaldoxime, acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, and other oxime compounds, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is used for improving adhesion with a surface functional layer such as a hard coat layer that can be formed on a coating layer, and for improving wet heat resistance of the coating layer. It is what The carbodiimide compound is a compound having one or more carbodiimide or carbodiimide derivative structures in the molecule, but a polycarbodiimide compound having two or more in the molecule is more preferable for better adhesion and the like.

  The carbodiimide compound can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

  Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.

  The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight of the carbodiimide compound to give 1 mol of carbodiimide group [g]) and is usually 100 to 1000, preferably 250 to 800, more preferably 300. It is -700, More preferably, it is the range of 350-650. Use within the above range is preferable because adhesion to the functional layer is improved.

  The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin with ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and the like hydroxyl groups and amino groups, There are polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, poly Examples of tetramethylene glycol diglycidyl ether and monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N′-tetraglycidyl-m-xylyl. Examples include range amine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  The melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylolized melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and these Mixtures can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  These cross-linking agents are used in a design that improves the performance of the coating layer by reacting in the drying process or film forming process. It can be inferred that unreacted products of these crosslinking agents, compounds after the reaction, or mixtures thereof exist in the finished coating layer.

  In addition, particles can be used in combination for the purpose of blocking and improving slipperiness in forming the coating layer. The average particle diameter is preferably 1.0 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less from the viewpoint of transparency of the film. The lower limit is preferably in the range of 0.03 μm or more, more preferably 0.05 μm or more in order to improve the slipperiness more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles. Among these, silica is preferable from the viewpoint of transparency.

  Further, in the range not impairing the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant are formed as necessary for forming the coating layer. It is also possible to use a foaming agent, a dye, a pigment and the like in combination.

  As a ratio with respect to the total nonvolatile components in the coating solution for forming the coating layer of the present invention, the polymer is usually in the range of 10% by weight or more, preferably in the range of 20 to 97% by weight, more preferably in the range of 30 to 90% by weight. It is. When outside the above range, the adhesion with the functional layer may be lowered.

  As a ratio with respect to the total nonvolatile components in the coating liquid for forming the coating layer of the present invention, the crosslinking agent is usually in the range of 90% by weight or less, preferably in the range of 3 to 80% by weight, more preferably in the range of 10 to 70% by weight. It is a range. When it is out of the above range, when the adhesion with the functional layer is deteriorated, the heat and moisture resistance may not be good.

  Analysis of the components in the coating layer can be performed by analysis of TOF-SIMS, ESCA, fluorescent X-rays, and the like, for example.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. In addition, 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.

  Examples of the method for forming the coating layer of the present invention include gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze coating, and impregnation. Conventionally known coating methods such as coat, kiss coat, spray coat, calendar coat, and extrusion coat can be used.

  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 270 ° 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.

  A layer (functional layer) containing fine particles and a compound having a cyclic structure, which is formed on the coating layer in the film of the present invention, is provided for imparting dimensional stability by heat treatment.

  By containing the fine particles and the compound having a cyclic structure, it is possible to reduce the dimensional change due to shrinkage caused by the orientation of the base film during heat treatment by the elastic modulus of the functional layer, and to improve the dimensional stability. It was found that it can be secured. Further, it has been found that even when the film thickness of the base film is thin (for example, 50 μm or less), it is possible to ensure dimensional stability by heat treatment.

  It has been found that the amount of fine particles contained in the functional layer can ensure dimensional stability by being highly contained, preferably in the range of 30% by volume or more, more preferably in the range of 50% by volume or more, and still more preferably. It is in the range of 55 to 90% by volume, particularly preferably in the range of 60 to 80% by volume, and most preferably in the range of 60 to 72% by volume. When the amount is less than 30% by volume, the dimensional stability due to heat treatment may be inferior, and when the amount is too large, there is a concern that the transparency and the handleability are deteriorated.

  From the viewpoint of transparency of the film, the fine particles contained in the functional layer preferably have an average particle size in the range of 1 to 200 nm, more preferably in the range of 1 to 100 nm, still more preferably in the range of 4 to 50 nm, particularly preferably. The range is 5 to 20 nm. By using in the above range, it is possible to ensure the transparency of the film without causing a scattering phenomenon to incident light due to the Mie scattering phenomenon. The average particle diameter means the number average particle diameter. When the shape of the fine particles is spherical, it can be calculated by “the sum of the equivalent circle diameters of the measurement particles / the number of measurement particles”. When the shape of the fine particles is not spherical, it can be calculated by “the sum of the short diameter and the long diameter / number of measured particles”. Further, when two or more kinds of fine particles are contained, the average particle size of the mixed particles becomes the average particle size.

  Examples of the fine particles contained in the functional layer include transparent inorganic fine particles such as silica, alumina, titania, soda glass, diamond, and zirconia. Among these, from the point of being able to improve the storage elastic modulus of the functional layer, easy to adjust the refractive index of the coating layer and functional layer for reducing interference unevenness due to external light reflection, specific gravity, price, etc. Silica fine particles are preferred.

  Many silica fine particles whose surface is modified have been developed, are highly dispersible in various resins, and can form a uniform functional film. Specific examples of the silica fine particles include dried powdery silica fine particles, colloidal silica (silica sol) dispersed in various solvents, and the like.

  For the purpose of improving dispersibility, silane coupling agents, titanate coupling agents, alumina, etc., as long as the properties such as transparency, solvent resistance, liquid crystal resistance and heat resistance are not significantly impaired. It is also possible to use surface-treated silica fine particles.

  The compound having a cyclic structure is used for ensuring the dimensional stability by heat treatment together with the fine particles. In order to further ensure dimensional stability, it has been found that it is preferable to use not only fine particles but also a compound having a rigid structure in the functional layer, and a compound having a cyclic structure is used for that purpose.

  Examples of the compound having a cyclic structure include a cyclic aliphatic structure, an aromatic structure, a cyclic acetal structure, a cyclic ketone structure, and a cyclic silicon-containing structure. Among them, polycyclic aliphatic structures having a structure such as tricyclodecane, norbornane and adamantane (preferably condensed polycyclic and bridged polycyclic rings), condensed polycyclic aromatic structures having a structure such as naphthalene and anthracene, fluorene A cyclic siloxane structure having a polyaromatic structure having a structure such as silsesquioxane or the like is preferable. Among these, a polycyclic aliphatic structure and a fluorene structure are more preferable from the viewpoint of transparency and handleability.

  The functional layer containing the fine particles and the compound having a cyclic structure can form a conventionally known layer, but is preferably a cured layer from the viewpoint of dimensional stability by heat treatment and prevention of scratches. Examples of the cured layer include a layer formed from a curable compound by active energy rays such as ultraviolet rays and electron beams, and a layer formed from a thermosetting compound. More preferred.

  The compound used for forming the functional layer may be a conventionally known material and is not particularly limited. For example, reactive silicon such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane Examples include cured products such as compounds. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an active energy ray-curable (meth) acrylate is particularly preferable. In addition, the description of (meth) acrylate in this specification represents an acrylate and a methacrylate.

  The composition containing the active energy ray-curable (meth) acrylate is not particularly limited. For example, a mixture of one or more known active energy ray-curable monofunctional (meth) acrylates, bifunctional (meth) acrylates, polyfunctional (meth) acrylates, and commercially available as an active energy ray-curable hard coat resin material In addition, those other than these may be used as long as the object of the present embodiment is not impaired.

  The active energy ray-curable monofunctional (meth) acrylate is not particularly limited. For example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) ) Acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, alkyl (meth) acrylate such as isobornyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc. Alkyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate, etc. Amino group-containing (meth) acrylates such as xylalkyl (meth) acrylate, benzyl (meth) acrylate, aromatic (meth) acrylate such as phenoxyethyl (meth) acrylate, diaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, Methoxyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, ethylene oxide modified (meth) acrylate such as phenylphenol ethylene oxide modified (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, Examples include (meth) acrylic acid.

  The active energy ray-curable difunctional (meth) acrylate is not particularly limited, and for example, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6- Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, alkanediol di (meth) acrylate such as tricyclodecane dimethylol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate Bisphenol F ethylene oxide modified di (meth) acrylate and other bisphenol modified di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, urethane di (meth) acrylate And epoxy di (meth) acrylate.

  The active energy ray-curable polyfunctional (meth) acrylate is not particularly limited, and examples thereof include dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, and ditrimethylolpropane tetra (meth) acrylate. , Pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ε-caprolactone modified tris (acryloxyethyl) isocyanurate Acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urea Down prepolymers, urethane acrylates such as dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, and the like.

  Among these (meth) acrylates, a functional layer having a highly crosslinked structure can be formed, and the functional layer can maintain a high storage elastic modulus, and therefore has a good dimensional stability after heat treatment. Therefore, bifunctional or higher (meth) acrylates are preferred. Moreover, what has a cyclic structure in these (meth) acrylate compounds is more preferable.

  In addition, the above-mentioned compound may be used independently and may be used together 2 or more types.

  The most preferable form for forming the functional layer of the present invention is a cured layer using silica fine particles and an active energy ray-curable bifunctional or higher (meth) acrylate having a cyclic structure.

  Other components contained in the functional layer are not particularly limited. Examples thereof include a polymerization initiator, a polymerization inhibitor, an antioxidant, a sensitizer, an antistatic agent, a dispersant, a surfactant, a light stabilizer, and a leveling agent. In addition, when the film is dried after film formation in the wet coating method, an arbitrary amount of solvent can be added.

  As a ratio to the total nonvolatile components in the compound excluding the fine particles forming the functional layer of the present invention, the compound having a cyclic structure is usually in the range of 20% by weight or more, preferably in the range of 30% by weight or more, more preferably 50% by weight. % Or more, and more preferably 70% by weight or more. When outside the above range, the dimensional stability after the heat treatment may not be sufficient.

  The analysis of the components in the functional layer can be performed, for example, by analysis of TOF-SIMS, ESCA, fluorescent X-rays and the like.

  As a method for forming the functional layer, conventionally known coating methods such as gravure coating, die coating, bar coating, air knife coating, offset printing, flexographic printing, screen printing, dip coating, etc. can be used. Moreover, after forming a functional layer on glass or a film, the method of transferring a functional layer to a base film is also possible.

  In the present invention, after forming the functional layer, it is necessary that there is little interference unevenness due to external light reflection. In order to obtain such a film, it is necessary to adjust the refractive index of the polyester film, the coating layer, and the functional layer of the base material. Specifically, the refractive index of the coating layer is adjusted to the vicinity of the geometric mean of the refractive index of the polyester film and the refractive index of the functional layer.

  When a polyethylene terephthalate film is used as the polyester film, the refractive index of the biaxially stretched film is about 1.65, which is a high value as a general organic compound. In order to match the refractive index, it is necessary to adjust the refractive indexes of the coating layer and the functional layer within a certain range. For example, if the refractive index of the functional layer is too high, it is necessary to increase the refractive index of the coating layer in order to reduce interference unevenness, and this may not be achieved with only an organic compound having good adhesion. If the coating layer contains a large amount of inferior material such as an inorganic compound, the adhesion with the functional layer may be lowered. On the other hand, if the functional layer is composed only of a compound having a low refractive index, the rigidity of the functional layer may be lowered, and the dimensional stability after the heat treatment may be deteriorated.

  In view of the above, the preferable range as the refractive index of the functional layer is in the range of 1.44 to 1.52, more preferably in the range of 1.46 to 1.50, and still more preferably in the range of 1.47 to 1.49. is there.

  Moreover, the preferable range of the refractive index of a coating layer is the range of 1.53-1.59, More preferably, it is the range of 1.54-1.58, More preferably, it is the range of 1.55-1.57.

  By the way, the film thickness and refractive index of the coating layer are closely related to the reflectance of the coating layer. In the film thickness within the scope of the present invention, when a graph showing the wavelength on the horizontal axis and the reflectance on the vertical axis is drawn, the wavelength of the minimum value is related to the film thickness, and the reflectance of the minimum value is the refractive index. There is a relationship. When the minimum value of the reflectance is a short wavelength, the film thickness is thin. When the reflectance is a long wavelength, the film thickness is large. If the minimum value appears at the same wavelength, the reflectance of the minimum value is a high value when the refractive index is high, and a low value when the refractive index is low. In the present invention, the reflectance of the minimum value varies depending on the wavelength range of the minimum value even if the material design of the coating layer is exactly the same. Specifically, comparing the case where the wavelength range of the minimum value exists in the short wavelength region and the case where it exists in the long wavelength region, the reflectance is lower in the case where it exists in the long wavelength region.

  In the present invention, the favorable reflectance of the coating layer is preferably the case where one absolute value appears in the wavelength range of 400 to 800 nm, more preferably one in the range of 500 to 700 nm in absolute reflectance. is there. The minimum value of absolute reflectance is preferably in the range of 2.8 to 4.5%, more preferably in the range of 3.1 to 4.0%, and still more preferably in the range of 3.2 to 3.9%. Range. When outside the above range, interference unevenness occurs, and there is a concern that the visibility of the film is lowered.

  The absolute reflectance of the coating layer can be measured by peeling off the functional layer at the interface between the coating layer and the functional layer.

  From the viewpoint of dimensional stability by heat treatment, the shrinkage rate in the film of the present invention is preferably 1.0% or less in both the vertical direction and the horizontal direction by heat treatment at 180 degrees for 30 minutes, and more preferably in the vertical direction of 0.1%. The range is 7% or less and the horizontal direction is 0.5% or less.

  Moreover, in order to improve the dimensional stability by heat processing, or to prevent the curvature of the film by heat processing, it is preferable to provide a functional layer on both surfaces of a polyester film. Therefore, it is preferable to provide a coating layer on both sides of the polyester film. Moreover, in order to prevent generation | occurrence | production of curvature more, it is more preferable that the functional layer provided in both surfaces is the same.

  The haze in the film of the present invention is preferably a small value from the viewpoint of transparency, preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less. It is. Further, the total light transmittance is preferably a high value, preferably in the range of 80% or more, more preferably in the range of 85% or more, and further preferably in the range of 90% or more.

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

(2) Measuring method of average particle diameter Using TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100V), the average value of the particle diameters of 10 particles was defined as the average particle diameter.

(3) Method for measuring film thickness of coating layer The film surface in a state where the coating layer was formed on the polyester film (before forming the functional layer) was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V).

(4) Method for measuring refractive index of functional layer Using an Abbe refractometer (SL-Na-B, manufactured by Atago Co., Ltd.), the measurement light (sodium D line) is incident on the functional layer, The measurement was performed by the specified measurement method shown on the refractometer.

(5) Measuring method of volume% of fine particles TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100V) is used to observe the cross section of the functional layer, and the area ratio of the cross section of the particle to the entire functional layer Was volume%.

(6) Method for measuring shrinkage The film on which the functional layer is formed is cut into a size of 100 mm in the vertical direction and 10 mm in the horizontal direction, and after heat treatment in an oven set at 200 ° C. for 30 minutes, the film is taken out of the oven and returned to room temperature. After that, the amount of contraction in the vertical direction was measured with a precision of 0.1 mm using a caliper. Similarly, the laminated polyester film is cut into a size of 10 mm in the vertical direction and 100 mm in the horizontal direction, placed in an oven set at 200 ° C. for 30 minutes, heat-treated for 30 minutes, taken out of the oven and returned to room temperature, and then horizontal using a caliper. The amount of shrinkage in the direction was measured with an accuracy of 0.1 mm. Using the measured values, the ratio of the shrinkage to the original size before shrinkage was calculated as a% value in the longitudinal direction and the transverse direction.

(7) Haze measuring method The haze based on JISK7136 was measured for the film in which the functional layer was formed using the reflectance / transmittance meter (Murakami Color Research Laboratory HR-100).

(8) Measuring method of total light transmittance The total light transmittance based on JISK7361 was measured for the film in which the functional layer was formed using the reflection and transmittance meter (Murakami Color Research Laboratory HR-100). .

(9) Method for evaluating the absolute reflectance from the surface of the coating layer in the polyester film 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 before forming the functional layer, and the spectrophotometer Meter (Nippon Bunko UV-Vis spectrophotometer V-570 and automatic absolute reflectance measuring device ARM-500N) using synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval The absolute reflectance in the wavelength range of 400 to 800 nm was measured on the coating layer surface at 0 nm, the bandwidth was 10 nm, and the scanning speed was 1000 m / min, and the wavelength (bottom wavelength) and reflectance at the minimum value were evaluated.

(10) Method for evaluating interference unevenness Visually observe the interference unevenness of the film on which the functional layer is formed under a three-wavelength fluorescent lamp. If the interference unevenness cannot be confirmed, ◎, thin and sparse interference unevenness is confirmed. ◯, thin, but linear interference unevenness can be confirmed Δ, and clear interference unevenness is confirmed ×.

(11) Adhesion evaluation method The film on which the functional layer is formed is treated in an environment of 60 ° C. and 90% RH for 100 hours, then 10 × 10 cross-cut is performed, and an 18 mm width tape (Nichiban Co., Ltd.) Company-made cello tape (registered trademark) CT-18) was applied and the peeled surface was observed after abrupt peeling at a 180 degree peel angle. If the peeled area was less than 5%, ◎ 5% or more and less than 10% If it was ◯, 10% or more and less than 50%, Δ, and 50% or more, ×

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the resulting polyester, and 100 ppm of magnesium acetate tetrahydrate with respect to the resulting polyester as the catalyst at 260 ° C. in a nitrogen atmosphere at 260 ° C. The reaction was allowed to proceed. Subsequently, 50 ppm of tetrabutyl titanate was added to the produced polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to 0.3 kPa in absolute pressure, and melt polycondensation was further performed for 80 minutes to obtain the intrinsic viscosity. 0.63 polyester (A) was obtained.

<Method for producing polyester (B)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, and magnesium acetate tetrahydrate as a catalyst were subjected to an esterification reaction at 225 ° C. in a nitrogen atmosphere at 900 ppm with respect to the produced polyester. Subsequently, 3500 ppm of orthophosphoric acid was added to the produced polyester, and 70 ppm of germanium dioxide was added to the produced polyester. The temperature was raised to 280 ° C. over 2 hours and 30 minutes, and the pressure was reduced to an absolute pressure of 0.4 kPa. After 85 minutes of melt polycondensation, polyester (B) having an intrinsic viscosity of 0.64 was obtained.

<Method for producing polyester (C)>
In the production method of the polyester (A), the polyester (C) is produced using the same method as the production method of the polyester (A) except that 0.2 parts by weight of silica particles having an average particle diameter of 1.6 μm is added before the melt polymerization. Got.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
・ Condensed polycyclic aromatic polyester resin: (IA)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / diethylene glycol = 92/8 // 80/20 (mol%)

・ Polyester resin: (IB)
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%)

Acrylic resin: (IC) Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)

-Urethane resin: (ID)
Water of polyester polyurethane resin formed from isophorone diisocyanate unit: terephthalic acid unit: isophthalic acid unit: ethylene glycol unit: diethylene glycol unit: dimethylolpropanoic acid unit = 12: 19: 18: 21: 25: 5 (mol%) Dispersion.

・ Oxazoline compounds: (IIA)
Acrylic polymer having an oxazoline group and a polyalkylene oxide chain Epocros WS-500 (Oxazoline group amount = 4.5 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)

・ Isocyanate compounds: (IIB)
158 parts by weight of hexamethylene diisocyanate trimer, 26 parts by weight of methoxypolyethylene glycol (OH value = 81 mg KOH / g), 27.8 parts by weight of diethyl diethylene glycol and 0.001 part by weight of dioctyltin laurate were reacted at 85 ° C. Thereafter, the mixture was allowed to cool, and 66 parts by weight of methyl ethyl ketone oxime was added dropwise to react. Subsequently, 115 parts by weight of 1,6-hexamethylenediol-based polycarbonate diol (OH value = 56 mgKOH / g), 1.2 parts by weight of trimethylolpropane (OH value = 1254 mgKOH / g), dimethylolpropionic acid (OH value = 837 mgKOH) / G) 7.6 parts by weight and 50 parts by weight of dimethyldipropylene glycol were added, and after stirring, 40.3 parts by weight of isophorone diisocyanate was added and reacted. After allowing to cool, 8.2 parts by weight of hexamethylene diisocyanate trimer was added, and after stirring, 5.8 parts by weight of triethylamine was added and stirred. A block isocyanate compound obtained by dropping 450 parts by weight of water into this mixed solution and dropping and stirring 21 parts by weight of a 15% aqueous diethylenetriamine solution.

・ Carbodiimide compounds: (IIC)
Polycarbodiimide compound Carbodilite V-02 (carbodiimide equivalent = 600, manufactured by Nisshinbo Co., Ltd.)

・ Epoxy compounds: (IID) polyglycerol polyglycidyl ether

・ Hexamethoxymethylolmelamine (IIE)

Particles: (III) Silica particles having an average particle size of 0.07 μm

Example 1:
A mixed raw material obtained by mixing polyesters (A), (B), and (C) at a ratio of 85%, 5%, and 10%, respectively, is used as a raw material of the outermost layer (surface layer), and polyesters (A) and (B) are each 95 %, 5% mixed raw materials were used as intermediate layer raw materials, each was supplied to two extruders, melted at 285 ° C., and then on a cooling roll set at 40 ° C. Coextruded with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 3: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the aqueous coating solution 1 shown in Table 1 below was applied to both sides of the longitudinally stretched film. Then, the film is stretched 4.0 times at 120 ° C. in the transverse direction, heat treated at 225 ° C., relaxed by 2% in the transverse direction, and has a coating layer with a coating layer thickness (after drying) of 0.10 μm. A polyester film having a thickness of 23 μm was obtained.

  On the coating layer of the obtained polyester film, 14.4 parts by mass of a photocurable bifunctional acrylate monomer / oligomer having a tricyclodecane structure (Shin-Nakamura Chemical Co., Ltd., A-DCP, refractive index 1.50) Silica fine particles (manufactured by Admatechs Co., Ltd., YA010C-SM1, refractive index 1.46, average particle size 10 nm) 51.1 parts by mass, photocuring agent (manufactured by BASF Ltd., 1-hydroxycyclohexyl-phenyl ketone). After coating and drying a curable resin composition in which 44 parts by mass and 34.1 parts by mass of a solvent (manufactured by Arakawa Chemical Co., Ltd., methyl ethyl ketone) were uniformly mixed so that the thickness after curing was 3 μm, Irradiation and curing with a high-pressure mercury lamp (160 W / cm) gave a film having a functional layer on one side. A similar operation was performed on the opposite side to obtain a film having functional layers on both sides. The refractive index of the functional layer was 1.48, and the volume fraction of silica fine particles in the functional layer was 63% by volume.

  When the obtained film was evaluated, the shrinkage ratio was as low as 0.6% in the vertical direction and 0.3% in the horizontal direction. Moreover, the interference nonuniformity characteristic was also favorable and the adhesiveness of a functional layer and a base film was also favorable. The properties of this film are shown in Tables 2 and 3 below.

Examples 2-17:
In Example 1, it manufactured like Example 1 except changing a coating agent composition and a film thickness as shown in Table 1 and 2, and the laminated polyester film which has a functional layer was obtained. As shown in Table 3, the completed polyester film had good shrinkage, interference interference characteristics, and adhesion.

Comparative Example 1:
In Example 1, it manufactured like Example 1 except not providing a functional layer, and obtained the polyester film which has an application layer. When the finished polyester film was evaluated, as shown in Table 3 below, the shrinkage in the vertical direction was high and the dimensional stability by heat treatment was poor.

Comparative Examples 2 and 3:
In Example 1, it manufactured like Example 1 except changing a coating agent composition and a film thickness as shown in Table 1 and 2, and the laminated polyester film which has a functional layer was obtained. In addition, the absolute reflectance of the coating layer had no minimum value. As shown in Table 3, the finished polyester film showed clear interference unevenness.

Comparative Example 4:
In Example 1, it manufactured similarly to Example 1 except not providing an application layer, and obtained the laminated polyester film which has a functional layer. When the completed polyester film was evaluated, as shown in Table 3 below, clear interference unevenness was observed and adhesion was inferior.

  The film of the present invention is used for solar cells, flexible displays, organic EL lighting, substrates with transparent electrodes such as touch panels, etc., where high transparency, dimensional stability after heat treatment, and reduction of interference unevenness due to reflection of external light are required. Can be suitably used.

Claims (8)

An active energy ray-curable bifunctional or higher functional (meth) acrylate having a coating layer having a film thickness of 0.04 to 0.20 μm on at least one surface of the polyester film, and having fine particles and a cyclic structure on the coating layer. A laminated polyester film comprising a layer containing a polymerized cured product of a composition comprising: The laminated polyester film according to claim 1, wherein the refractive index of the layer containing the fine particles and the compound having a cyclic structure is in the range of 1.44 to 1.52. The laminated polyester film according to claim 1 or 2, wherein the proportion of the fine particles contained in the layer containing the fine particles and the compound having a cyclic structure is 30% by volume or more. The laminated polyester film according to any one of claims 1 to 3, wherein the average particle diameter of the fine particles is in the range of 1 nm to 200 nm. Laminated polyester film according to claim 1 or Re not gall containing polymer in the coating layer. The minimum value of the absolute reflectance of the coating layer appears one in the wavelength range of 400 to 800 nm, and the minimum value is in the range of 2.8 to 4.5%. The laminated polyester film described. The laminated polyester film according to any one of claims 1 to 6, wherein a shrinkage ratio in a longitudinal direction and a transverse direction by heat treatment at 180 degrees for 30 minutes is 1.0% or less. The laminated polyester film according to any one of claims 1 to 7, wherein the haze is 3.0% or less and the total light transmittance is 80% or more.