JP2014014992A - Laminate polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate polyester film that has excellent adhesiveness even with respect to a solventless resin that does not have sufficient adhesiveness and corresponds to high luminance, and is adequately used as a member for a microlens and prism sheet to be used in a backlight unit and the like of a liquid crystal display, for instance.SOLUTION: The laminate polyester film has a coating layer formed on at least one face of a polyester film, which is formed of a coating liquid containing a polyurethane resin, a carbodiimide compound and an oxazoline compound.

Description

  The present invention relates to a polyester film having a coating layer having excellent adhesion to various topcoats, and in particular, a high-brightness prism sheet having a coating layer having excellent adhesion to an active energy ray-curable resin. And a polyester film suitably used as a substrate for processing microlenses.

  In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. Since these liquid crystal displays do not have a light emitting function by a liquid crystal display unit alone, a method of displaying by irradiating light using a backlight from the back side is widespread.

  The backlight system has a structure called an edge light type or a direct type. Recently, there is a tendency to reduce the thickness of liquid crystal displays, and an edge light type is increasingly used. The edge light type is generally configured in the order of a reflection sheet, a light guide plate, a light diffusion sheet, and a prism sheet. As the flow of light, the light incident on the light guide plate from the backlight is reflected by the reflection sheet and emitted from the surface of the light guide plate. The light beam emitted from the light guide plate enters the light diffusion sheet, is diffused and emitted by the light diffusion sheet, and then enters the next existing prism sheet or microlens sheet.

  The prism sheet and the microlens sheet used in this configuration are for improving the optical efficiency of the backlight and improving the luminance. As the transparent base film, a polyester film is generally used in consideration of transparency and mechanical properties. In order to improve the adhesion between the base polyester film and the prism layer, these intermediate layers are easily bonded. In general, a conductive coating layer is provided. As an easily adhesive coating layer, for example, polyester resins, acrylic resins, and polyurethane resins are known (Patent Documents 1 to 3).

  As a method for forming the prism layer and the microlens layer, for example, an active energy ray-curable coating material is introduced into a mold, irradiated with active energy rays in a state of being sandwiched between polyester films, the resin is cured, and the mold is removed. The method of forming on a polyester film is mentioned. In the case of such a method, it is necessary to use a solventless active energy ray-curable coating material in order to form the prism type with precision. However, solventless paints are less permeable and swellable to the easy-adhesion layer laminated on the polyester film than solvent-based paints, and tend to have insufficient adhesion. A coating layer made of a specific polyurethane resin has been proposed to improve the adhesion, but even with such a coating layer, the adhesion has not always been sufficient for solventless paints. (Patent Document 4).

  In order to improve adhesion to a solventless resin, a coating layer mainly composed of a polyurethane resin and an oxazoline compound has been proposed. (Patent Document 5). However, it is derived from the current decrease in the number of backlights and the demand for lower power consumption, etc., and solvent-free resins corresponding to higher brightness of prism sheets and microlens sheets, that is, resins with a higher refractive index. Adhesion may not be sufficient.

JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092 JP 2000-229395 A JP-A-2-158633 JP 2010-13550 A

  The present invention has been made in view of the above circumstances, and the solution to the problem is that it has good adhesion even to a high-brightness, solvent-free resin that is difficult to produce adhesion. An object of the present invention is to provide a laminated polyester film that can be suitably used as a microlens or prism sheet member used in a backlight unit or the like.

  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 resides in a laminated polyester film having a coating layer formed from a coating solution containing a polyurethane resin, a carbodiimide compound, and an oxazoline compound on at least one surface of the polyester film.

  According to the laminated polyester film of the present invention, when a microlens layer, a prism layer or the like is formed, a laminated polyester film having excellent adhesion can be provided, 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, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  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, titanium compounds and germanium compounds are preferable because they have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film becomes high. 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 for improving the weather resistance of the film and preventing deterioration of the liquid crystal. 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, and an organic ultraviolet absorber is preferable from the viewpoint of transparency. 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 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 include inorganic particles such as magnesium, 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.

  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.

  Moreover, the average particle diameter of the particle | grains to be used is 5 micrometers or less normally, Preferably it is the range of 0.01-3 micrometers. When the thickness exceeds 5 μm, the surface roughness of the film becomes too rough, which may cause problems when various surface functional layers such as a hard coat layer are formed in a 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 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 in the range of 10 to 350 μm, preferably 25 to 250 μm.

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

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

  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. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore inline coating is preferably used. The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with offline coating, thin film coating can be performed more easily. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  The polyester film in the present invention has a coating layer on at least one surface, but even if a similar or other coating layer or functional layer is provided on the opposite surface of the film, it is naturally included in the concept of the present invention.

  Next, the coating layer provided on the film in the present invention will be described. In the present invention, it is an essential requirement to have a coating layer formed from a coating solution containing a polyurethane resin, a carbodiimide compound and an oxazoline compound on at least one surface of the polyester film.

  The coating layer in the film of the present invention can improve the adhesion to various surface functional layers, but it is particularly a solventless active energy ray-curable layer, and more particularly, high brightness that hardly exhibits adhesion. Adhesiveness with such a solventless active energy ray-curable layer can be improved. For example, a microlens layer or a prism layer can be formed.

The polyurethane resin used for forming the coating layer in the film of the present invention is a polymer compound having a urethane bond in the molecule, and is usually prepared by the reaction of a polyol and an 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. Polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, trimethylolpropane, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, , 5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, , 10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like. 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.) and those having derivative units of lactone compounds such as polycaprolactone.

  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 preferable in order to improve adhesion with various topcoat layers.
Examples of the polyisocyanates constituting the polyurethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α′-tetra. Aliphatic diisocyanates having an aromatic ring such as methylxylylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4 -Cyclohexyl And alicyclic diisocyanates such as dicyclohexylmethane diisocyanate and isopropylidene dicyclohexyl diisocyanate. These may be used alone or in combination of two or more. These polyisocyanate compounds may be a dimer, a trimer represented by an isocyanuric ring, or a polymer higher than that. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates from the viewpoint of improving adhesion to the active energy ray-curable coating material and preventing yellowing due to ultraviolet rays.

  A chain extender may be used when synthesizing the polyurethane 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, butanediol and pentanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, neopentyl glycol and neopentyl. Examples include glycols such as ester glycols such as glycol hydroxypivalate. 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 isophorone diamine.

  The polyurethane resin used for forming the coating layer in the film of the present invention may be one using a solvent as a medium, but is preferably one containing water as a medium. In order to disperse or dissolve the polyurethane 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 polyurethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into a skeleton of a polyurethane 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, and quaternary ammonium salt, and a carboxyl group is preferred. As a method for introducing a carboxyl group into a polyurethane 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 polyurethane 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, the carboxyl group from which the neutralizing agent is removed in the drying step of the coating solution can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  The polyurethane resin used for forming the coating layer in the film of the present invention has a glass transition point (hereinafter sometimes referred to as Tg) of preferably 10 ° C. or lower, more preferably −10 ° C. or lower. When Tg is higher than 10 ° C., easy adhesion may be insufficient. Tg said here refers to the temperature which created the dry film | membrane of the polyurethane resin and measured using the differential scanning calorimeter (DSC).

  Moreover, it is also possible to use the compound which has a carbon-carbon double bond for the polyurethane resin used for formation of the coating layer in the film of this invention. The said carbon-carbon double bond is for improving adhesiveness with the layer formed on a coating layer. When the layer formed on the coating layer is a resin that is cured by a radical reaction of a carbon-carbon double bond, it reacts with the carbon-carbon double bond in the coating layer to provide stronger adhesion. Can be issued. In this case, since the coating layer and the layer formed thereon form a strong bond between carbon and carbon, even when the Tg of the polyurethane resin described above is not low, it is possible to effectively provide adhesion. It is.

  As the carbon-carbon double bond, a conventionally known material can be used as long as it reacts with the carbon-carbon double bond contained in the compound forming the prism layer or the microlens layer. For example, it may be introduced into the resin in the form of acrylate group, methacrylate group, vinyl group, allyl group or the like.

  Various substituents can be introduced into the carbon-carbon double bond, such as an alkyl group such as a methyl group or an ethyl group, a phenyl group, a halogen group, an ester group, an amide group, or a conjugated double bond. You may have such a structure. Further, the amount of the substituent is not particularly limited, and any of a 1-substituted product, a 2-substituted product, a 3-substituted product, or a 4-substituted product can be used. A 2-substituted product is preferable, and a 1-substituted product is more preferable.

In view of the ease of introduction into the polyurethane resin and the reactivity with the carbon-carbon double bond contained in the compound that forms the prism layer or the microlens layer, an acrylate group or a methacrylate group having no substituent is preferable. More preferred are acrylate groups without groups.
In the formation of the coating layer in the film of the present invention, a polymer other than the polyurethane resin can be used in combination in order to improve the appearance of the coating layer and the adhesion to various prism layers, microlens layers, and the like. .

  Specific examples of the polymer include acrylic resin, polyester resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches, and the like. It is done.

  In the formation of the coating layer in the film of the present invention, the coating layer of the coating layer is strengthened, has sufficient adhesion with various overcoating layers such as a prism layer and a microlens layer, and improves moisture and heat resistance. A carbodiimide compound and an oxazoline compound are used as a crosslinking agent.

  A carbodiimide compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. For better adhesion and the like, a polycarbodiimide compound having two or more in the molecule is more preferable.

  The carbodiimide compound used for forming the coating layer in the film of the present invention 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.

  Further, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound as long as the effects of the present invention are not lost, a surfactant is added, a polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, a hydroxy A hydrophilic monomer such as an alkyl sulfonate may be added and used.

  The oxazoline compound used for forming the coating layer in the film of the present invention is a compound having an oxazoline group in the molecule, particularly a polymer containing an oxazoline group, and an addition polymerizable oxazoline group-containing monomer alone or other Can be made by polymerization with monomers. 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 and vinylidene chloride; styrene, An α, β-unsaturated aromatic monomer such as α-methylstyrene can be used, and one or more of these monomers can be used. Furthermore, in the coating layer in this invention, it is also possible to use together crosslinking agents other than a carbodiimide compound and an oxazoline compound in the range which does not impair the meaning of invention. Known resins can be used, and examples thereof include an epoxy compound, an isocyanate compound, an alkoxysilane compound, and a melamine compound.

  The crosslinking agent used for the coating layer in the film of the present invention is used in a design that improves the performance of the coating layer by reacting in the drying process or the 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 forming the coating layer in the film of the present invention, it is preferable to use particles as a constituent component of the coating layer in order to improve slipperiness and blocking. Examples of the particles used include inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  Furthermore, as long as it does not impair the gist of the present invention, the coating layer has an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, A pigment or the like may be contained. These additives may be used independently and may use 2 or more types together as needed.

  The polyurethane resin is generally 20 to 90% by weight, preferably 25 to 80% by weight, more preferably 40 to 75% by weight as a ratio to the total nonvolatile components in the coating liquid forming the coating layer in the film of the present invention. . If the amount is less than 20% by weight, the adhesion may not be sufficient due to the small amount of polyurethane resin component. If the amount exceeds 90% by weight, the coating layer becomes brittle due to a decrease in the crosslinking agent, and the adhesion is not sufficient. In some cases, the heat and humidity resistance may not be sufficient.

  The ratio of the carbodiimide compound is usually 3 to 40% by weight, preferably 8 to 35% by weight, as a ratio to the total nonvolatile components in the coating liquid forming the coating layer in the film of the present invention. When the amount is less than 3% by weight, the coating layer becomes brittle due to the small amount of the carbodiimide compound, and the adhesion may not be sufficient or the heat and moisture resistance may not be sufficient. When the amount exceeds 40% by weight, the adhesion is sufficient. It may not be.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the coating layer in the film of the present invention, the amount of the oxazoline compound is usually 3 to 40% by weight, preferably 8 to 35% by weight. When the amount is less than 3% by weight, the coating layer becomes brittle due to the small amount of the oxazoline compound, and the adhesion may not be sufficient or the heat and humidity resistance may not be sufficient. If the amount exceeds 40% by weight, the adhesion is sufficient. It may not be.

  As a ratio with respect to all the non-volatile components in the coating solution for forming the coating layer in the film of the present invention, the particle content is preferably in the range of 0.3 to 25% by weight, and in the range of 0.4 to 15% by weight It is more preferable that it is in the range of 0.5 to 10% by weight. If it is less than 0.3% by weight, the effect of imparting slipperiness or preventing blocking may be insufficient. Moreover, when it exceeds 25 weight%, there exists a concern about the fall of the transparency of a coating layer, the fall of the coating film strength by the continuity of a coating layer being impaired, or the fall of adhesiveness easily.

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

  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. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  The film thickness of the coating layer in the film of the present invention is usually 0.002 to 1.0 μm, preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.2 μm, and particularly preferably 0.01 to 0. The range is 1 μm. When the film thickness is below the above range, the adhesion may be insufficient, and when it exceeds the above range, the blocking characteristics may be deteriorated.

  In the film of 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.

  In the film of 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 at 80 to 200 ° C. The heat treatment may be performed for ˜40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

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

  On the coating layer of the film of the present invention, it is common to provide a prism layer, a microlens layer, etc. in order to improve the brightness, and it is particularly difficult to ensure adhesion, which is necessary for increasing the brightness. A resin layer having a high refractive index can be provided. In recent years, various shapes have been proposed for the prism layer in order to improve the luminance efficiently. Generally, prism layers are formed by arranging prism rows having a triangular cross section in parallel. Similarly, various shapes of the microlens layer have been proposed, but in general, a large number of hemispherical convex lenses are provided on the film. Any layer can have a conventionally known shape.

  Examples of the shape of the prism layer include a triangular cross section having a thickness of 10 to 500 μm, a pitch of prism rows of 10 to 500 μm, and an apex angle of 40 ° to 100 °. As the material used for the prism layer, conventionally known materials can be used, and examples thereof include materials made of an active energy ray-curable resin, and (meth) acrylate-based resins are typical examples. As a constituent compound of the resin, generally, for example, it has a polyhydric alcohol component such as ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, bisphenol A structure, polyurethane structure, polyester structure, epoxy structure and the like ( Examples include meth) acrylate compounds.

  Examples of the prescription for increasing the refractive index for increasing the brightness include a method using a compound having a large aromatic structure, a sulfur atom, a halogen atom, and a metal compound in addition to the above general compound. Among them, a method using a compound having a large aromatic structure or a sulfur atom is particularly preferable from the viewpoint of the environment because the refractive index of the prism layer and the microlens layer can be made uniform.

Examples of the compound having a large aromatic structure include condensed polycyclic aromatic structures such as naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c] phenanthrene, and perylene. , A compound having a biphenyl structure, a compound having a fluorene structure, and the like.
Examples of the shape of the microlens layer include a hemispherical shape having a thickness of 10 to 500 μm and a diameter of 10 to 500 μm, but may have a shape such as a cone or a polygonal pyramid. As the material used for the microlens layer, conventionally known materials can be used as in the prism layer, and examples thereof include an active energy ray curable resin.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example in the range which does not exceed the summary. 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 precisely weighed, 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 The coating layer was observed using TEM (H-7650 made by Hitachi, acceleration voltage 100V), and 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 surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by the ultrathin section method was stained with RuO _4, and the cross section of the coating layer was measured using TEM (H-7650 manufactured by Hitachi, accelerating voltage 100 V).

(4) Evaluation method of adhesion of coating layer Active energy ray curing comprising the coating composition shown below on a mold member in which a large number of prism rows with a pitch of 50 μm and apex angle of 65 ° are arranged in parallel to form a prism layer. A layered polyester film is placed in such a direction that the coating layer comes into contact with the active energy ray curable resin, and the active energy ray curable resin is uniformly stretched by a roller. Then, the resin was cured by irradiating with ultraviolet rays so that the integrated light amount became 200 mj / cm ² . Subsequently, the film was peeled off from the mold member to obtain a film on which a prism layer was formed. The obtained prism layer was scratched at 5 mm intervals with a cutter knife, a 24 mm wide tape (Cello Tape (registered trademark) CT-24 manufactured by Nichiban Co., Ltd.) was applied, and it was peeled off rapidly at a peeling angle of 180 degrees. Thereafter, the peeled surface was observed. When the peeled area was 5% or less, ◎ was marked when it exceeded 5% and 20% or less, Δ when it exceeded 20% and 50% or less, and × when it exceeded 50%.

Active energy ray curable resin composition:
2-Biphenoxyethyl acrylate 20 parts 4,4 ′-(9-fluorenylidene) bis (2-phenoxyethyl acrylate) 27 parts Ethylene glycol modified bisphenol A acrylate (ethylene glycol chain = 8) 50 parts Diphenyl (2,4,6 -Trimethylbenzoyl) phosphine oxide 3 parts

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 resulting 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 carried out for 80 minutes. 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 polyester (A), polyester (C) is obtained using the same method as the production method of polyester (A), except that 0.3 part by weight of silica particles having an average particle diameter of 2 μm is added before melt polymerization. It was.

The following was used as the coating composition.
(Example compounds)
Polyurethane resin (U1): aqueous dispersion of polyurethane resin polymerized with the following composition: 400 parts of polycarbonate polyol having a number average molecular weight of 2000 consisting of 1,6-hexanediol and diethyl carbonate, 10.4 parts of neopentyl glycol, cyclohexane diisocyanate A polyurethane resin having a polycarbonate structure having a Tg of −30 ° C. obtained by neutralizing a prepolymer comprising 58.4 parts and 74.3 parts of dimethylolbutanoic acid with triethylamine and extending the chain with isophoronediamine.

-Polyurethane resin (U2): aqueous dispersion of polyurethane resin polymerized with the following composition: 400 parts of polycarbonate polyol having a number average molecular weight of 2000 consisting of 1,6-hexanediol and diethyl carbonate, 14 parts of butanediol, 15 parts of pentaethylene glycol A polyurethane resin having a polycarbonate structure with a Tg of −3 ° C., obtained by neutralizing a urethane resin composed of 100 parts of isophorone diisocyanate and 75 parts of dimethylolpropionic acid with triethylamine.

-Polyurethane resin (U3): Water dispersion of a polyurethane resin having a carbon-carbon double bond polymerized with the following composition Hydroxyethyl acrylate unit: Dicyclohexylmethane diisocyanate unit: Hexamethylene diisocyanate trimer unit: Caprolactone unit: Ethylene glycol unit : Polyurethane resin in which the weight of the carbon-carbon double bond portion formed from dimethylolpropanoic acid units = 18: 12: 22: 26: 18: 4 (mol%) is 2.0% by weight.

Acrylic resin (A1): Aqueous dispersion of acrylic resin polymerized with the following composition: Monomer 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)

Polyester resin (E1): A water dispersion of a 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%)

・ Carbodiimide compound (C1A)
Polycarbodiimide compound Carbodilite E-02 (Nisshinbo Co., Ltd.)
・ Carbodiimide compounds (C1B)
Polycarbodiimide compound Carbodilite SV-02 (Nisshinbo Co., Ltd.)

・ Oxazoline compounds (C2)
Oxazoline group-containing acrylic polymer, Epocross WS-500 (manufactured by Nippon Shokubai Co., Ltd.)
Epoxy compound (C3)
Denacol EX-521 (manufactured by Nagase ChemteX Corporation), which is polyglycerol polyglycidyl ether
・ Particle (F1)
Silica sol with an average particle size of 0.07 μm

Example 1:
A mixed raw material in which polyesters (A), (B), and (C) are mixed at a ratio of 89%, 5%, and 6%, respectively, is used as a raw material for 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: 18: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating solution 1 shown in the following Table 1 was applied to one side of the longitudinally stretched film, guided to a tenter, Polyester with a thickness of 125 μm having a coating layer with a coating layer thickness of 0.03 μm after being stretched 4.0 times at 120 ° C. and heat-treated at 225 ° C. A film was obtained. When the adhesiveness of the obtained film was evaluated, the adhesiveness was good. The properties of this film are shown in Table 2 below.

Examples 2-10:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. These characteristics are shown in Table 2 below.

Comparative Examples 1-5:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. When the adhesiveness of the completed film was evaluated, as shown in Table 2, the adhesiveness was inferior.

  The film of the present invention includes, for example, a resin layer such as a prism layer or a microlens layer that has a high refractive index necessary for high brightness, such as adhesion to various surface functional layers such as liquid crystal and plasma display members. Can be suitably used for applications that require high adhesion.

Claims (1)

A laminated polyester film comprising a coating layer formed from a coating solution containing a polyurethane resin, a carbodiimide compound, and an oxazoline compound on at least one side of the polyester film.