JP6740810B2 - Hard coat polyester film - Google Patents

Description

The present invention relates to a hard coat polyester film, and more specifically, it is mainly used for a display or the like, and has an functionality such as an antireflection film, an antiglare film, a light diffusion sheet, a lens sheet, a near infrared ray shielding film, a transparent conductive film, The present invention relates to a hard coat polyester film useful as a base material for a film.

In general, a transparent thermoplastic resin film made of polyethylene terephthalate (PET), acrylic, polycarbonate (PC), polyolefin or the like is used as a base material of a functional film used as an optical member.

When the thermoplastic resin film is used as the base material of the functional film, functional layers according to various uses are laminated. For example, in a liquid crystal display (LCD), a protective layer for preventing scratches on the surface, an antireflection layer (AR layer) for preventing reflection of external light, a lens layer used for condensing and diffusing light, and improving brightness. A functional layer such as a light diffusion layer may be used. Among such base materials, a polyester film is particularly widely used as a base material for various functional films because it has excellent transparency, dimensional stability, and chemical resistance and is relatively inexpensive.

However, the surface of the polyester film is generally fragile, and there is a drawback that the surface is easily scratched during transportation of the film base material during manufacturing of the optical member.
Further, also in the process of combining various optical members, there is a problem that scratches are generated on the opposite surface of the functional layer when the members are rubbed or conveyed. These scratches affect the quality of the entire display, which causes a decrease in yield in display manufacturing. Therefore, for the purpose of protecting the surface of the film substrate, a method has been proposed in which a protective layer (hard coat layer) having scratch resistance is provided on the opposite surface of the film substrate on which the functional layer is laminated. Hard coat materials used therefor are required to have higher hardness, high adhesion, scratch resistance, and curl of the film when cured.

As the hard coat layer, an ultraviolet curable resin composition is generally used, but there is a problem that curling is likely to occur because the curing shrinkage of the coating film is generally large. In Patent Document 1, high hardness and low curl are improved by using an ethylenically unsaturated group-containing polyester dendrimer. However, in the examples, the thickness of the base polyester film is as thick as 188 μm, and there is no description of a thin base material.

On the other hand, Patent Literature 2 discloses a technique in which curling is suppressed and hardness is improved by heating a UV-curable resin composition after UV-curing it. Further, Patent Document 3 describes a method of obtaining a coating film having high hardness by irradiating with ultraviolet rays in a low oxygen atmosphere to cure and then irradiating with ultraviolet rays in air to cure. However, these have a problem that they are complicated in process.

Further, in Patent Document 4, by providing a functional layer made of a metal halide and/or a metal oxide between a plastic base material and a hard coat layer, a hard layer is obtained by a synergistic effect of hardness and adhesion of the functional layer itself. There is described a technique for developing a hardness equal to or higher than that of the coat itself. However, since the method for forming the functional layer is a dry method such as vapor deposition or sputtering, the control becomes complicated and there is a problem that it causes a cost increase.

Patent Document 5 describes a technique in which an incompletely cured barrier layer (2B to H) is applied on a base material and a hard coat is applied thereon, so that adhesion and high hardness are satisfied even with a thin film. ing. However, in order to form the barrier layer, a solvent for swelling or dissolving the base material is required, and in the examples, there is no cellulose ester film alone and a polyester film as a base material.

JP 2005-76005 A JP, 2009-91544, A JP, 2007-262281, A JP, 2014-121829, A JP, 2009-234052, A

While a hard coat having functionality is required, further improvement in hardness, which is the original purpose of the hard coat, is also required. However, when the thickness of the base material (base film) is limited, the actual situation is that curling occurs due to an increase in the cross-linking density of the hard coating agent, and cracks occur accordingly. If the curl is large, the productivity in the next step and the adhesion durability after being bonded to another film are significantly reduced. Therefore, when a hard coat layer is provided on the film, the coating thickness of the hard coat layer and the crosslinking reaction rate must be limited in order to suppress curling, especially when the substrate thickness is thin. However, the pencil hardness is often limited to about 2H.

Therefore, in the present invention, even if the thickness of the polyester film of the substrate is thin, curling can be suppressed, the hardness of the surface is high, and the hard coat polyester film having good adhesion to the substrate film Providing as an issue.

That is, the present invention has the following configurations.
1. A hard coat polyester film having a hard coat layer on at least one side, wherein an easy-adhesion cured layer containing a reaction product of a water-soluble acrylic polyol and a water-soluble amino resin between the polyester film as a base material and the hard coat layer. And the water-soluble acrylic polyol has 40 to 80 mol% of constituent units having a hydroxy group in 100 mol% of all constituent units, and the reaction product of the water-soluble acrylic polyol and the water-soluble amino resin is A hard coat polyester film, which is a reaction product of 100 parts by mass of a water-soluble acrylic polyol and 10 to 70 parts by mass of a water-soluble amino resin.
2. The hard coat polyester film according to the first aspect, wherein the water-soluble acrylic polyol has a carboxy group.
3. 3. The hard coat polyester film according to the above 1st or 2nd, wherein the water-soluble amino resin is an alkylated melamine resin.
4. The hard coat polyester film according to any one of the above first to third, wherein the easy-adhesion cured layer has a Martens hardness of 280 to 600 N/mm ² .
5. The hard coat polyester film according to any one of the first to fourth aspects, wherein the hard coat layer contains an ionizing radiation-curable compound.

According to the present invention, even when the thickness of the base polyester film is thin, curling is suppressed, the surface hardness is high, and a hard coat polyester film having a hard coat layer excellent in adhesion with the polyester film is provided. It is now possible to provide.

The polyester resin forming the base film of the hard coat polyester film of the present invention has an ethylene terephthalate unit as a main constituent component. The ethylene terephthalate unit is preferably 80 mol% or more, more preferably 90 mol% or more, and most preferably homopolyethylene terephthalate in 100 mol% of polyester constituent units.

Other dicarboxylic acid components constituting the polyester resin of the present invention include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid and 2,6-naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid and the like. Aliphatic dicarboxylic acids and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid can be mentioned.

Examples of the diol component constituting the polyester resin include 1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propane, in addition to ethylene glycol. Diol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 1,4-butanediol, hexanediol, neopentyl glycol, hexanediol, etc. Examples thereof include aliphatic diols, alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols such as bisphenol A.

A well-known method can be adopted as a method for producing the polyester resin, and the above-mentioned reaction product of the first step and the first step in which the dicarboxylic acid and diol are directly esterified or transesterified are combined. It can be produced by a method of producing the condensation reaction in the second step. At this time, as a reaction catalyst, for example, an alkali metal, an alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, a titanium compound or the like can be used.

Among the polyester resins forming the hard coat polyester film of the present invention, various additives such as waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducing agents, and heat stabilizers may be added as necessary. , A coloring pigment, an anti-coloring agent, an ultraviolet absorber and the like can be added.

In the polyester resin forming the hard coat polyester film of the present invention, fine particles as a lubricant for improving workability (sliding property) of the film may be added. As the fine particles, any one can be selected, for example, as the inorganic fine particles, silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, etc., and as the organic fine particles, for example, acrylic resin. Examples thereof include particles, melamine resin particles, silicone resin particles and crosslinked polystyrene particles. The average particle size of the fine particles is within the range of 0.05 to 3.0 μm (when measured with a Coulter counter) and can be appropriately selected as necessary.

The hard coat polyester film of the present invention also includes a laminated polyester film having at least one polyester resin layer. When two or more polyester resin layers are laminated, the polyester resin layers may have the same composition or different compositions. The layer that can be laminated as the other layer is not particularly limited as long as it is a thermoplastic resin layer.

Next, the hard coat layer of the hard coat polyester film of the present invention will be described.

The hard coat layer in the present invention preferably contains an ionizing radiation-curable compound. Unlike a thermosetting resin, heat treatment is not required at the time of curing, and heat shrinkage of the base film due to heat can be reduced, which is preferable. In the present invention, the ionizing radiation-curable compound refers to a compound that polymerizes and/or reacts by irradiating with an electron beam, radiation, or ultraviolet rays, and by such a compound polymerizing and/or reacting. It constitutes a hard coat layer. Examples of the ionizing radiation-curable compound used in the present invention include melamine-based, acrylic-based, and silicone-based ionizing-radiation-curable compounds, and among them, acrylate-based ionizing-radiation-curable compounds are preferable from the viewpoint of obtaining high surface hardness. ..

The ionizing radiation-curable compound may be a radical polymerization system, a cation polymerization system, or a mixed system of cation polymerization and radical polymerization, but a radical polymerization system is particularly preferable because it has a large reaction rate and is excellent in productivity. Examples of the radical polymerization-based ionizing radiation-curable compound include unsaturated monomers, oligomers, resins, and compositions containing them. Specific examples thereof include polyfunctional ionizing radiation curable acrylic compounds having two or more functional groups such as acrylate, urethane acrylate and polyester acrylate, and ethylene glycol di(meth)acrylate and propylene glycol di(meth). Acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth) ) Acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerol tri(meth)acrylate, triallyl(meth)acrylate, bisphenol A ethylene oxide modified di(meth) Acrylate and the like are preferred. The ionizing radiation-curable compounds may be used alone or in combination of two or more.

The ionizing radiation polymerization initiator may be a radical polymerization system, a cation polymerization system, or a mixed system of cation polymerization and radical polymerization, but a radical polymerization system is particularly preferable because it has a high reaction rate and is excellent in productivity. Examples of ionizing radiation radical polymerization initiators include alkylphenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-dialkyldione compounds, Examples thereof include disulfide compounds, fluoroamine compounds, aromatic sulfoniums, titanocenes, and phenyl oxyacetates, which may be used alone or in combination of two or more. Examples of acetophenones include 2,2-diethoxyacetophenone, p-dimethylacetophenone, 1-hydroxydimethylphenylketone, 1-hydroxycyclohexylphenylketone, 2-methyl-4-methylthio-2-morpholinopropiophenone, 2 -Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl ]-2-Hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl -Propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2- Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl) Phenyl]-1-butanone is included. Examples of benzoins include benzoin benzene sulfonate, benzoin toluene sulfonate, benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether. Examples of benzophenones include benzophenone, 2,4-dichlorobenzophenone, 4,4-dichlorobenzophenone and p-chlorobenzophenone. Examples of phosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and bisacylphosphine oxide. Phenyl oxyacetic acid includes 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and 2-(2-hydroxyethoxy)ethyl ester.

The ionizing radiation polymerization initiator has a lower limit of 0.1 part by mass or more, more preferably 1 part by mass or more, and an upper limit of 30 parts by mass or less, more preferably 20 parts by mass or less, with respect to 100 parts by mass of the ionizing radiation-curable compound. Can be used in a range. If the addition amount is too small, the hardness of the hard coat layer may be insufficient. On the other hand, if the amount is too large, the hard coat layer may turn yellow or the hard coat layer may be insufficiently cured.

In addition to the ionizing radiation polymerization initiator, a photosensitizer may be used within the range not impairing the present invention. Specific examples of the photosensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, Michler's ketone and thioxanthone.

When a coating liquid for forming a hard coat layer is applied to the surface of the easy-adhesion cured layer of the substrate film, in order to improve the leveling property, an ionizing radiation-curable compound or the like may be added with a diluent as necessary. You may dilute. Examples of the diluent include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane, heptane, octane, nonane and decane, ketones such as methyl ethyl ketone, diethyl ketone and diisopropyl ketone. The blending amount of the diluent may be appropriately selected so that the viscosity becomes appropriate.

Examples of the inorganic fine particles contained in the hard coat layer include amorphous silica, crystalline glass filler, silica, zirconium oxide, titanium dioxide, alumina, and other inorganic oxides, silica-alumina composite oxide particles, magnesium carbonate. , Aluminum hydroxide, barium sulfate, calcium carbonate, calcium phosphate, kaolin, talc, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, and mica.

When an antireflection layer composed of a high refractive index layer/low refractive index layer or a high refractive index layer/medium refractive index layer/low refractive index layer is laminated on the surface of the hard coat layer, the hard coat layer has a high refractive index. By increasing the index, the high refractive index layer can be omitted from the antireflection layer. As a result, the cost can be reduced. In order to increase the refractive index of the hard coat layer, it is effective to include inorganic fine particles having a high refractive index in the hard coat layer. Examples of the inorganic fine particles having a high refractive index include zirconium oxide and titanium oxide.

It is important that the content of the inorganic fine particles in the hard coat layer is 1% by mass or more and 80% by mass or less. If the content of the inorganic fine particles is less than 1% by mass, scratch resistance is insufficient. On the other hand, when the content of the inorganic fine particles exceeds 80% by mass, the transparency tends to decrease. The average particle size of the inorganic fine particles is preferably 5 to 500 nm from the viewpoint of transparency. However, such inorganic fine particles having a small average particle diameter tend to aggregate and are unstable. Therefore, in order to enhance the dispersion stability of the inorganic fine particles, it is preferable to add a photosensitive group to the surface of the inorganic fine particles to enhance the affinity with the curable resin.

The thickness of the hard coat layer is in the range of 0.1 to 30 μm and may be determined according to the application. More preferably, it is 1 to 15 μm. When the thickness of the hard coat layer is within the above range, the hardness of the surface of the hard coat layer is high and scratches are less likely to occur. Further, the hard coat layer does not easily become brittle, and cracks are unlikely to occur in the hard coat layer when the hard coat film is bent.

Next, the easy-adhesion cured layer provided between the substrate and the hard coat layer of the hard coat polyester film of the present invention will be described.

The easy-adhesion cured layer in the present invention contains a reaction product of a water-soluble acrylic polyol and a water-soluble amino resin.

The acrylic polyol of the present invention is an acrylic resin having a hydroxy group in the molecule. The constituent unit having a hydroxy group is preferably contained in 40 to 80 mol% in 100 mol% of all constituent units. The hydroxy group causes a cross-linking reaction with the water-soluble amino resin to form a three-dimensional cross-linked structure in the hard coat layer. When the constituent unit having a hydroxy group in the acrylic polyol is 40 mol% or more, the amount of the crosslinked structure in the hard coat layer is sufficient, and the pencil hardness of the hard coat layer surface can be efficiently increased, which is preferable. On the other hand, when it is 80 mol% or less, sufficient adhesion to the polyester film substrate is obtained, which is preferable.

To introduce a hydroxy group into an acrylic polyol, monomers having a hydroxy group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and 2-hydroxy group. A ring-opening addition product of γ-butyrolactone or ε-caprolactone to ethyl (meth)acrylate may be used as a copolymerization component. Among them, 2-hydroxyethyl (meth)acrylate is preferable because it does not impair the water solubility. In addition, these may use 2 or more types together.

The acrylic polyol used in the present invention is water-soluble. This is because the environmental load is small. As the monomer imparting water solubility, it is preferable to use a (meth)acrylic monomer containing a polar group or a non-acrylic vinyl monomer containing a polar group as a copolymerization component. The polar group-containing (meth) acrylic monomer, in addition to the hydroxy group-containing monomer described above, (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, a monomer containing a carboxy group such as fumaric acid, Examples thereof include monomers having an acid anhydride group such as maleic anhydride and itaconic anhydride. In addition, monomers having an ether bond such as EO-modified nonylphenol acrylate and methoxypolyoxyethylene glycol acrylate can be used because they contribute to the water solubility of the acrylic polyol. Examples of the non-acrylic vinyl monomer containing a polar group include styrene sulfonic acid and vinyl sulfonic acid. Among these, acrylic acid and methacrylic acid are preferable. Whether it is water-soluble or not can be determined by adopting the solubility evaluation method described in Examples below.

The above-mentioned monomer for imparting water solubility is preferably 8 mol% or more, more preferably 10 mol% or more, in 100 mol% of all constituent units of the acrylic polyol. When the amount is 8 mol%, water solubility can be efficiently imparted to the acrylic polyol, which is preferable. The monomer for imparting water solubility is preferably 35 mol% or less, more preferably 30 mol% or less. When the content is 35 mol% or less, the Tg of the obtained coating film does not become too high with respect to the preferred range described below, and the film-forming property and the stretching suitability in in-line coating are good, which is preferable.

In order to exhibit good water solubility, it is preferable to neutralize the carboxy group introduced into the acrylic polyol by copolymerizing acrylic acid or methacrylic acid. Examples of the basic neutralizing agent include amine compounds such as ammonia, trimethylamine, triethylamine, and dimethylaminoethanol, and inorganic basic substances such as potassium hydroxide and sodium hydroxide. Of these, water-soluble stabilizers are used. In order to express good water solubility, it is preferable to use an inorganic basic substance as a neutralizing agent. The neutralization rate is preferably 30 mol% to 90 mol%, more preferably 40 mol% to 80 mol%. When the neutralization rate is 30 mol% or more, the water solubility of the acrylic polyol is sufficient, the acrylic polyol can be easily dissolved during the preparation of the coating solution, and there is no fear that the coating surface after drying will be whitened. preferable. On the other hand, when the neutralization ratio is 90 mol% or less, the water solubility is not too high, the alcohol and the like can be easily mixed in the preparation of the coating liquid, and the water resistance of the coating film after curing is maintained, which is preferable.

The Tg of the acrylic polyol is preferably 50 to 100°C, more preferably 55 to 90°C. The lower the Tg of the acrylic polyol, the lower the minimum film forming temperature (MFT, Minimum Film Forming Temperature), so that the film forming property tends to be excellent even at a low drying temperature. However, when the Tg of the acrylic polyol is 50° C. or higher, there is no tackiness after drying the coating solution, and there is no risk of roll transfer or peeling of the coating film, which is preferable in the manufacturing process. In addition, there is no fear that the rigidity as the main agent will decrease, and it is preferable to use a cross-linking agent together so that sufficient coating film hardness can be obtained. On the other hand, when the Tg is 100° C. or lower, the MFT does not become too high, and the film-forming property is not likely to deteriorate even if the drying temperature is not particularly increased, which is preferable. The deterioration of the film-forming property is not preferable in the manufacturing process because it may cause a poor appearance after drying the coating solution and a poor followability of the coating film during stretching of the in-line coating.

As the Tg adjusting monomer copolymerized to adjust the Tg to the above range, a (meth)acrylic monomer having no hydroxy group or a non-acrylic vinyl monomer can be used. Specific examples of the (meth)acrylic monomer having no hydroxy group include methyl(meth)acrylate, ethyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, n-amyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, (Meth)acrylic acid alkyl esters such as isobornyl (meth)acrylate and stearyl (meth)acrylate; nitrogen-containing acrylic monomers such as (meth)acrylamide, diacetone acrylamide, n-methylol acrylamide, (meth)acrylonitrile; methacrylic acid Examples thereof include vinyl, and these may be used alone or in combination of two or more.

As the non-acrylic vinyl monomer, styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene (a mixture of m-methylstyrene and p-methylstyrene), chlorostyrene; vinyl acetate, vinyl propionate, vinyl butyrate. , Vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl pivalate, vinyl octylate, vinyl monochloroacetate, divinyl adipate, Examples thereof include vinyl esters such as vinyl crotonate, vinyl sorbate, vinyl benzoate, and vinyl cinnamate; vinyl halide monomers such as vinyl chloride and vinylidene chloride; and one or more types can be used.

The Tg adjusting monomer is preferably the rest of the monomer after determining an appropriate amount of the hydroxyl group-containing monomer and the monomer for imparting water solubility. The Tg of the copolymer is calculated by the following Fox equation.
W _n : Mass fraction of each monomer (mass %)
Tg _n : Tg (K) of homopolymer of each monomer

The acrylic polyol of the present invention can be obtained by known radical polymerization. Any of emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like can be adopted. From the viewpoint of handleability, solution polymerization is preferable. Water-soluble organic solvents that can be used for solution polymerization include ethylene glycol n-butyl ether, isopropanol, ethanol, n-methylpyrrolidone, tetrahydrofuran, 1,4-dioxane, 1,3-oxolane, methyl solosolve, ethyl solosolve. , Ethyl carbitol, butyl carbitol, propylene glycol monopropyl ether, propylene glycol monobutyl ether and the like. You may use these, mixing with water.

The polymerization initiator may be a known compound that generates a radical, but a water-soluble azo polymerization initiator such as 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide is preferable. The temperature and time of polymerization are appropriately selected.

The mass average molecular weight (Mw) of the acrylic polyol is preferably about 10,000 to 80,000. A more preferable range is 20,000 to 60,000. When the Mw is 10,000 or more, there is no fear of thermal decomposition in the tenter, which is preferable. When the Mw is 80,000 or less, the viscosity of the coating liquid does not significantly increase and the coatability is good, which is preferable.

The hydroxyl value of the acrylic polyol is preferably 100 to 380 mgKOH/g. When it is 100 mgKOH/g or more, there is no fear that the crosslink density will decrease, which is preferable. On the other hand, when it is 380 mgKOH/g or less, the crosslinking density does not become too high and the coating film does not become brittle, which is preferable. Further, since the hydroxyl group-containing monomer is not excessively used in order to increase the hydroxyl value, the amount of the monomer imparting water solubility is not insufficient, and the water solubility of the acrylic polyol is maintained, which is preferable.

The acid value of the acrylic polyol is preferably 100 mgKOH/g or less. It is preferable that the acid value is 100 mgKOH/g or less, because it is difficult to undergo hydrolysis and the water resistance in a wet heat environment is not deteriorated. The acid value is more preferably 70 mgKOH/g or less, further preferably 60 mgKOH/g or less. The lower limit of the acid value is preferably about 30 mgKOH/g. This is to maintain water solubility.

The acrylic polyol of the present invention is reacted with a water-soluble amino resin. Therefore, the hard coat layer of the hard coat film of the present invention contains the reaction product of the acrylic polyol and the amino resin. The water-soluble amino resin of the present invention is a compound in which a methylolated melamine obtained by condensing melamine and formaldehyde is reacted with a lower alcohol such as methanol or ethanol to be partially alkyl etherified. It can be said that it is a water-soluble alkylated melamine resin. Such a water-soluble amino resin is available, for example, as "Nikalac (registered trademark of Nippon Carbide Industry Co., Ltd.) MX-035" manufactured by Sanwa Chemical Co., Ltd.

Next, the coating liquid for forming an easily-adhesive cured layer used in the present invention will be described. The coating liquid for forming an easily-adhesive cured layer contains an acrylic polyol, a water-soluble amino resin, water, and the water-soluble organic solvent described above. The water-soluble amino resin is preferably used in the range of 10 to 80 parts by mass, more preferably 30 to 70 parts by mass, still more preferably 40 to 70 parts by mass based on 100 parts by mass of the acrylic polyol. When the amount of the water-soluble amino resin in the coating liquid is 10 parts by mass or more, the adhesion between the hard coat layer and the polyester base film is improved, which is preferable. Moreover, high hardness is obtained, which is preferable. On the other hand, addition of 80 parts by mass or less is preferable because the tack-free property is maintained. The solid content concentration of the coating liquid is not particularly limited, but is preferably about 10 to 30% by mass. In addition, colloidal silica may be added and blended as a lubricant in the coating liquid. The colloidal silica is preferably about 10 to 30 parts by mass with respect to 100 parts by mass of the acrylic polyol. The colloidal silica is preferably a fine one having a primary particle diameter of 10 to 20 nm and a secondary particle diameter of about 30 to 50 nm, and examples thereof include PL-1 manufactured by Fuso Chemical Industry Co., Ltd.

Next, a method for producing the hard coat polyester film of the present invention will be described. The hard coat polyester film is obtained by melt-extruding the above polyester raw material with an extruder to form an unstretched film, and (1) applying a coating liquid for forming an easily adhesive cured layer on one side or both sides of the unstretched film. A method of performing pre-drying and then stretching in at least one direction (in-line method), (2) longitudinally stretching an unstretched film, applying a coating solution to one or both sides of the film after longitudinal stretching, and pre-drying, Then, a method of transverse stretching (in-line method, vertical and horizontal may be reversed), (3) a biaxially stretched film is manufactured, and a coating solution is applied off-line on one side or both sides of the film, followed by heat curing. There is a method of doing. Then, a hard coat layer is laminated on the easy-adhesion cured layer as described later.

The hard coat layer of the hard coat polyester film of the present invention can be coated with an aqueous coating solution, and the coating layer can be easily dried and heat-cured. Therefore, the in-line method (1) or (2) can be easily applied. It can be preferably adopted.

When melt-extruding the raw material resin for the base polyester film, the polyester raw material is preferably dried using a dryer such as a hopper dryer, a paddle dryer or the like, or a vacuum dryer. After the polyester raw material is dried in this way, it is melted at a temperature of 200 to 300° C. and extruded into a film using an extruder. For extrusion, any existing method such as a T-die method or a tubular method can be adopted.

Then, an unstretched film can be obtained by rapidly cooling the sheet-shaped molten resin after extrusion. As a method of rapidly cooling the molten resin, a method of obtaining a substantially unoriented resin sheet by casting the molten resin from a die onto a rotating drum and rapidly solidifying it can be suitably adopted.

The obtained unstretched film is preheated at 50 to 120° C., preferably 60 to 110° C., if necessary, then introduced into a roll-type longitudinal stretching machine, heated to 80 to 125° C., and then subjected to a difference in peripheral speed of the roll. The film is stretched in the machine direction about 2.5 to 5.0 times to obtain a uniaxially stretched film. After that, the coating liquid for forming the easy-adhesion cured layer is gravure coating method, kiss coating method, dipping method, spray coating method, curtain coating method, air knife coating method, blade coating method, reverse roll coating method, bar coating method, etc. Then, apply. The coating amount is preferably adjusted so that the cured easy-adhesion cured layer has a thickness of 1 μm or less. If the thickness exceeds 1 μm, the contribution of the increase in hardness of the hard coat layer becomes small, which is economically unfavorable, which is not preferable. In addition, the tack-free property after pre-drying is deteriorated, and problems such as transfer of the easy-adhesion layer to a metal roll occur in the process, which is not preferable. The lower limit of the thickness is preferably about 0.05 μm. If it is too thin, the adhesion to the substrate may be reduced, or the hardness of the hard coat applied to the upper layer may not be sufficiently expressed. A more preferable thickness range is 0.1 to 0.3 μm.

After coating, it is dried (pre-dried) at 80 to 120° C. for several tens of seconds, and laterally stretched 2.5 to 5.0 times with a tenter or the like. The stretching temperature is 80° C. or higher and 150° C. or lower. After transverse stretching, the film is heat-treated at 180° C. to 250° C. for about 0.3 to several seconds with the width of the film fixed, and then at 180° C. to 250° C. in the width direction of the film. It is preferable to perform a relaxation heat treatment of about 5%. The relaxation heat treatment is preferably 5 to 15 seconds. By the heat treatment after the transverse stretching, the acrylic polyol and the water-soluble amino resin react with each other, and an easily adhesive cured layer containing these reaction products is obtained. The easy-adhesion cured layer formed between the substrate and the hard coat layer in the hard coat polyester film of the present invention preferably has a Martens hardness of 280 to 600 N/mm ² . When the Martens hardness is 280 N/mm ² or more, the pencil hardness of the hard coat layer laminated on the easy-adhesion cured layer can be effectively 2H or more, which is preferable. The Martens hardness uses a diamond regular triangular pyramid indenter, an electronically controlled loading device, and a highly accurate displacement measuring device, so it is possible to control the depth in μm order and consider the influence of the base film. Without, the hardness of the hard coat layer itself can be evaluated. Further, in the case of pencil hardness evaluation, the tip shape of the pencil may change from time to time, but since the diamond regular triangular pyramid indenter is used in the Martens hardness evaluation, the tip shape hardly changes, and there is little variation in hardness evaluation. it can.

In the present invention, the hard coat layer is a polyester film having an easy-adhesion cured layer with an organic solvent, a coating solution containing an ionizing radiation-curable compound, and if necessary, a photopolymerization initiator, particles, and a surfactant. It is preferable to form the composition by coating and drying it and then curing it by irradiating it with ultraviolet rays or electron beams.

As a method for laminating the hard coat layer, a known method can be mentioned, and a method of coating and drying the coating solution on the substrate film and then curing the coating solution is preferable. As the coating method, known coating methods such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, a reverse roll coating method, a bar coating method and a lip coating method can be used. Can be mentioned. Among these, a gravure coating method, which can be applied by a roll-to-roll method and allows uniform application, and a reverse gravure method is particularly preferable.

As a method of dissolving or dispersing the ionizing radiation-curable compound, particles, photopolymerization initiator and the like contained in the coating liquid in an organic solvent, a method of stirring and dispersing them under heating is suitable. By heating the coating liquid, the solubility of the ionizing radiation-curable compound, particles and photopolymerization initiator can be improved. Therefore, the deterioration of the coating appearance due to undissolved substances and the like can be suppressed.

A known disperser can be used. Specific examples include ball mills, sand mills, attritors, roll mills, agitators, colloid mills, ultrasonic homogenizers, homomixers, pearl mills, wet jet mills, paint shakers, butterfly mixers, planetary mixers, and Henschel mixers.

The concentration of solid components such as the ionizing radiation-curable compound, particles and photopolymerization initiator contained in the coating liquid is preferably 5% by mass or more and 70% by mass or more. By adjusting the concentration of the solid content of the coating liquid to 5% by mass or more, it is possible to suppress the decrease in productivity due to the long drying time after coating. On the other hand, by adjusting the concentration of the solid content of the coating liquid to 70% by mass or less, it is possible to prevent the deterioration of the leveling property due to the increase of the viscosity of the coating liquid and the accompanying deterioration of the coating appearance. From the viewpoint of coating appearance, the solid content concentration of the coating liquid, the type of organic solvent, or the type of surfactant is adjusted so that the viscosity of the coating liquid is in the range of 0.5 cps to 300 cps. It is preferable.

The thickness of the hard coat layer after coating and curing is preferably 0.1 μm or more and 30 μm or less. Specifically, the lower limit of the thickness of the hard coat layer is preferably 0.5 μm or more, more preferably 1.0 μm or more. The upper limit of the thickness of the hard coat layer is more preferably 15 μm or less, further preferably 10 μm or less, and further preferably 3 μm or less. When the thickness of the hard coat layer is 0.1 μm or more, sufficient hardness is easily obtained, which is preferable. On the other hand, when the thickness of the hard coat layer is 30 μm or less, a good hard coat film can be obtained without causing a problem of curling due to poor curing of the hard coat layer or curing shrinkage, which is preferable.

When pre-drying is required, such as when the coating solution contains an organic solvent, the method of coating and drying on the substrate film includes known hot air drying, infrared heaters, etc. Drying is preferred.

The drying temperature after coating is preferably 40° C. or higher and 120° C. or lower, and particularly preferably the lower limit is 45° C. or higher and the upper limit is 80° C. or lower. When the temperature is 40° C. or higher, the organic solvent contained in the coating liquid can be sufficiently removed, and there is no risk of problems such as brushing. On the other hand, if the temperature is 120° C. or lower, it is possible to suppress minute coating defects such as bubbles, minute cissing, minute defects in the coating film such as cracks, and the like, and there is no fear that the appearance will deteriorate, which is preferable. Further, the film is not strongly contracted by heat, and there is no fear of deterioration of the flatness of the film due to heat wrinkles, which is preferable.

The tension of the film applied during drying is preferably 50 N/m or more and 300 N/m or less, and particularly preferably the lower limit is 100 N/m or more and the upper limit is 250 N/m or less. When the tension of the film is 50 N/m or more, the running film is not likely to meander, which is preferable. On the other hand, when it is 300 N/m or less, wrinkles do not occur in the film, flatness is maintained, and the appearance of the wound film is good, which is preferable.

In the present invention, a hard coat layer, an antistatic layer, an easily adhesive layer, a pressure-sensitive adhesive layer, an easily slipping layer, an electromagnetic wave absorbing layer, a dye or a pigment, etc. such as a hard coat layer, on the surface not provided with the hard coat layer, in a range that does not impair the effects of the present invention Other functions such as a resin layer containing a dye may be added.

In the present invention, the ionizing radiation-curable compound is cured by irradiation with ionizing radiation to form a hard coat layer. When irradiating with ultraviolet rays, an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, and a metal halide lamp are used, and an ultraviolet ray is irradiated with energy of 100 to 3000 mJ/cm ² in a wavelength region of 100 to 400 nm, preferably 200 to 400 nm. Irradiation is preferred. More preferably 50 mJ / cm ² or more 1000 mJ / cm ² or less, and more preferably the lower limit is 300 mJ / cm ² or more, the upper limit is 700 mJ / cm ² or less. It is desirable that the irradiation is performed in a nitrogen gas atmosphere because oxygen inhibition is reduced and scratch resistance is improved. When the integrated light amount is 50 mJ/cm ² or more, the polymerization reaction of the ionizing radiation-curable compound is promoted, and the surface hardness of the hard coat layer is increased, which is preferable. When the integrated light amount is 1000 mJ/cm ² or less, the base film is not likely to be deformed due to heat, which is preferable. The integrated light amount in the present invention can be measured by "UVR-T35" manufactured by Topcon.

When the coating liquid is cured with an electron beam, the irradiation dose is preferably 5 kGy or more and 100 kGy or less, and more preferably the upper limit is 30 kGy or more and the lower limit is 70 kGy or less. When it is 5 kGy or more, the polymerization reaction of the ionizing radiation-curable compound is promoted, and the surface hardness of the hard coat layer is improved, which is preferable. When it is 100 kGy or less, the life of the electron beam irradiation tube is extended, which is preferable in terms of production cost.

Thereby, the hard coat polyester film of the present invention is obtained. The thickness of the polyester film (excluding the coating film) is preferably 30 to 200 μm.

The hard coat layer in the present invention preferably has a pencil hardness of 2H or more. The curl height measured by the method described below is preferably less than 3 mm. Furthermore, it is preferable that the number of peeled squares in the cross-cut adhesion test measured by the method described below is 0.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the modes of these Examples, and may be appropriately performed without departing from the spirit of the present invention. It is possible to change. The evaluation method is shown below.

[NMR measurement]
The ratio of the copolymerization component introduced into the acrylic polyol is determined by nuclear magnetic resonance spectroscopy ( ¹ H-N
MR, ¹³ C-NMR: Varian Unity 400, manufactured by Agilent). The measurement was carried out by removing the solvent in the synthesized acrylic polyol with a vacuum dryer and then dissolving the dried product in heavy chloroform. From the obtained NMR spectrum, peaks of chemical shift δ (ppm) attributed to the methyl group site in methyl methacrylate, the hydroxy group site in hydroxyethyl acrylate, and the carboxy group site of methacrylic acid were identified. The integrated intensity of each obtained peak was determined, and the composition ratio (mol%) of the copolymerization component introduced into the acrylic polyol was confirmed from the number of hydrogens at each site and the integrated intensity.

[Confirmation of Tg]
The Tg of each acrylic polyol was determined from the composition ratio of the copolymerization component determined by the above NMR measurement and the Fox equation described above.

[Solubility]
The synthesized acrylic polyols (1) to (10) were put into a mixed solvent (25° C.) of 30% by mass of isopropanol and 70% by mass of water so that the solid content concentration was 12% by mass. Next, the stirring operation in the system was performed for 10 minutes, and the solubility of the acrylic polyol (1) to (10) was visually determined for the solubility of the acrylic polyol based on the following criteria. Table 1 shows the evaluation results.
◯: Colorless and transparent, no change was observed in the solution.
Δ: The solution is slightly turbid.
X: The solution is cloudy or gelling/precipitation of acrylic polyol is observed.
Further, the solubility of the coating liquid for the easy-adhesion cured layer (solid content concentration: 12% by mass) was judged based on the above criteria, and the evaluation results are shown in Tables 3 and 4.
◯: Colorless and transparent, no change was observed in the solution.
Δ: The solution is slightly turbid.
X: The solution is cloudy or gelling/precipitation of acrylic polyol is observed.

[Film forming property]
In order to evaluate the film-forming property of the acrylic polyol, the synthesized acrylic polyols (1) to (10) were mixed with 30% by mass of isopropanol and 70% by mass of water so that the solid concentration was 12% by mass. C.) to prepare a solution of the acrylic polyol alone, and then the solution was applied to the non-easy-adhesive surface of the polyester film (A4100, manufactured by Toyobo Co., Ltd.) with Mayer bar #5. Next, the film sample on which the coating layer (thickness 6.5 μm) was formed was allowed to stand in a hot air circulation oven set at a temperature of 60° C. for 30 seconds to perform pre-drying. Then, the film sample was taken out from the oven and pre-dried. The surface of the taken-out film was visually observed, and the acrylic polyol was evaluated for film-forming property by ranking according to the following criteria. The results are shown in Table 1.
◯: No whitening is observed in the coating film.
Δ: A slight whitening is observed in the coating film.
X: The coating film is entirely whitened.
[Tack-free property]
After preparing a coating liquid (solid content concentration: 12% by mass) for the easily adhesive cured layer, it is applied to the non-easy adhesive surface of a polyester film (A4100, manufactured by Toyobo Co., Ltd.) with a Mayer bar #5. Next, the film sample having the coating layer (thickness 6.5 μm) formed thereon was allowed to stand in a hot air circulation oven set at 60° C. for 30 seconds, the film sample was taken out of the oven, and the surface of the coating layer was palpated with a finger. .. The tackiness of the coating film obtained by touching with fingers was ranked according to the following criteria to evaluate tack-free property.
○: There is no sticky feeling.
Δ: Slightly sticky feeling (no coating film component adhered to fingertips when palpated).
Poor: Mostly sticky (a coating film component adheres to the fingertip during palpation).

[Pot life]
After preparing the coating liquid for the easy-adhesion cured layer (solid content concentration: 12% by mass), it was stored in a sample bottle capable of preventing solvent evaporation. Then, using a rheometer (MCR-302, manufactured by Anton Paar) and a cone plate (plate diameter: 50 mm, angle: 1°, manufactured by Anton Paar), the shear viscosity of the coating solution was measured under a shear rate of 1000 s ^-1. It was measured. The measurement was carried out at regular intervals from immediately after preparation to 48 hours later, and the rate of increase in shear viscosity was calculated based on the following formula. It should be noted that η _d is the shear viscosity over time, and η ₀ is the shear viscosity immediately after preparation of the solution. When the rate of increase in shear viscosity reached 20% or more, it was considered as the pot life of the coating solution, and if the rate of increase was less than 20% even after 48 hours from the preparation, the pot life was set to 48 hours.
Increase rate of shear viscosity (%)=100×η _d /η ₀
[Stretchability]
In order to evaluate the stretchability of the acrylic polyol itself, the synthesized acrylic polyols (1) to (10) were mixed with 30% by mass of isopropanol and 70% by mass of water so that the solid concentration was 12% by mass. (°C) to prepare a solution of the acrylic polyol alone, and then the solution was applied with a Meyer bar #5 to the surface of the polyester film which was only longitudinally stretched. Next, the film sample having the coating layer (thickness 6.5 μm) formed thereon was allowed to stand still in a hot air circulation oven set at a temperature of 60° C. for 30 seconds, and then the film sample was taken out from the oven and pre-dried. Then, the sample was manually rotated and set in a stretching device (manufactured by Toyobo Engineering Co., Ltd.), placed in a hot air circulation oven at 100° C., and slowly stretched. The stretching operation was performed until the length became 4 times the length before stretching, and the stretching device was taken out from the hot air circulation oven. Then, the coating film after stretching was observed with an optical microscope (magnification: 200 times), and the presence or absence of cracking due to stretching was determined according to the following criteria.
The coating liquid for easy-adhesion cured layer (solid content concentration: 12% by mass) was also evaluated by the same criteria, and the results are shown in Tables 3 and 4.
◯: No crack is seen at all.
Δ: Some cracks are seen (1 to 4).
X: Five or more cracks or cracks are observed on the entire surface.

[Martens hardness]
After cutting a film to be a sample into 10 mm×20 mm, a sample piece was pasted on a slide glass with an instant adhesive, and a surface of the sample piece was subjected to a dynamic ultra-fine hardness tester (DUH-211S, manufactured by Shimadzu Corporation). Was used to perform a push depth setting load-unloading test. From this measurement, the Martens hardness (HM ₁₁₅ ) was determined using the following formula (average value of n=3).
HM ₁₁₅ =1000×F/(26.43×h ² )
(F: load, h ² : push depth)
Measurement condition
(1) Indenter used: Diamond regular triangular pyramid indenter (ridge angle: 115°)
(2) Measurement mode: Push depth setting Load-Unload test
(3) Indentation depth: 0.05 μm
(4) Measurement atmosphere: 25±1℃, 65±5%RH
(5) Number of measurements n: 3

[Adhesion]
Using a cutter guide with a clearance of 2 mm, 100 square cuts penetrating the coating layer and reaching the base film are made on the surface of the coating film of the polyester film as a sample. Next, cellophane tape (registered trademark; manufactured by Nichiban Co., Ltd.; No. 405; width of 24 mm) was attached to the cut surface of the grid and rubbed with an eraser to completely adhere it. Then, the cellophane tape was vertically peeled off from the coating film layer, the number of squares of the coating film layer peeled off from the substrate film was visually counted, and the adhesion was determined from the following formula. In addition, partially peeled squares were counted as peeled squares and ranked according to the following criteria.
○: 0 peeled squares △: 1 to 5 peeled squares ×: 6 or more peeled squares

[Pencil hardness]
Based on JIS K 5600-5-4, the pencil hardness was measured using a pencil scratch tester. A pencil was scratched on the polyester film coating film as a sample by about 10 mm with a load of 750 gf being applied at an angle of 45°, and the condition of scratches was confirmed. The measurement was performed 5 times, and the hardness of the pencil when there was no scratch in all 5 times was defined as the pencil hardness.

[Flatness (curl height measurement)]
The hard-coated polyester film was cut into 10 cm squares, placed on a smooth surface, and the average height of the four corners of the curl was used as the curl height, and the rank was classified according to the following criteria.
◯: Curl average height of 4 corners is less than 3 mm Δ: Curl average height of 4 corners is 3 to 5 mm
×: Curl average height at four corners exceeds 5 mm

Synthesis example 1
[Synthesis of acrylic polyol (1)]
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube, 38 parts by mass of methyl methacrylate (MMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 11 parts by mass of methacrylic acid (MAA). Then, 349 parts by mass of isopropyl alcohol (IPA) were charged, and the temperature in the flask was raised to 80° C. while stirring. Stirring was performed for 3 hours while maintaining the inside of the flask at 80° C., and then 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. After nitrogen substitution was performed while heating the inside of the flask to 120°C, the mixture was stirred at 120°C for 2 hours.
Next, a pressure reduction operation of 1.5 kPa was carried out at 120° C. to remove unreacted raw materials and solvent to obtain an acrylic polyol. The inside of the flask was returned to atmospheric pressure and cooled to room temperature, and 598 parts by mass of an IPA aqueous solution (water content 50% by mass) was added and mixed. Then, using a dropping funnel while stirring, 0.5 M aqueous sodium hydroxide solution was added to neutralize the acrylic polyol until the pH of the solution was in the range of 5.5 to 7.5, and the solid content concentration was increased. To obtain 20% by mass of acrylic polyol (1). Table 1 also shows the composition ratio of the acrylic polyol (1) measured by NMR, solubility, film-forming property, tack-free property, and stretching suitability.

Synthesis examples 2-7
[Synthesis of acrylic polyols (2) to (7)]
As shown in Table 1, the acrylic polyol (2) having a solid content concentration of 20 mass% was prepared in the same manner as in Synthesis Example 1 except that the amounts of MMA, HEMA, MAA, IPA at the time of preparation, and IPA aqueous solution at the time of dilution were changed. ~ (7) was obtained. Table 1 also shows composition ratios, solubilities, film-forming properties, tack-free properties, and stretching suitability of acrylic polyols (2) to (7) measured by NMR. The composition ratio was represented by MMA as 1 (unit), HEMA as m (unit), and MAA as n (unit).

[Preparation of coating liquid for easy-adhesion cured layer]
The materials shown in Table 2 were added to an IPA aqueous solution (water content 70% by mass) so that the solid content concentration was 12% by mass, and the mixture was stirred to prepare coating liquids (1) to (23) for the easy-adhesion cured layer. ) Was prepared. In addition, "epochros" and "chemitite" are registered trademarks of Nippon Shokubai Co., Ltd., and "Barnock" is a registered trademark of DIC.

[Preparation of coating liquid for hard coat layer]
In a diluent (toluene: methyl ethyl ketone: butyl acetate = 10% by mass: 45% by mass: 45% by mass) composed of an organic solvent, urethane acrylate (BS-577, 100 parts by mass of Arakawa Chemical Co., Ltd. and 5 parts by mass of a photoinitiator (Irgacure 184, manufactured by BASF) were dissolved to prepare a coating solution (1) for the hard coat layer. Further, coating liquids (2) and (3) for the hard coat layer were prepared by using the same materials and the same number of parts by mass so that the solid content concentration was 10% by mass and 30% by mass.

Example 1
[Film formation and coating of coating liquid for easy-adhesion cured layer]
Polyethylene terephthalate (PET) resin pellets having an intrinsic viscosity of 0.62 dl/g and containing substantially no particles as a film raw material polymer were dried at 135° C. for 6 hours under a reduced pressure of 133 Pa. After that, it was supplied to an extruder, melt-extruded into a sheet at about 280°C, and rapidly cooled and adhered to solidify on a rotating cooling metal roll kept at a surface temperature of 20°C to obtain an unstretched PET sheet.
The unstretched PET sheet was heated to 100° C. with a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction with roll groups having different peripheral speeds to obtain a uniaxially stretched PET film.

Next, the coating liquid (1) for the easy-adhesion cured layer was applied to one side of the uniaxially stretched PET film by a metalling bar coating method so that the coating amount after drying was as shown in Table 3, and then 80°C. For 20 seconds (pre-drying). Subsequently, with a tenter, the film was stretched 4.0 times in the width direction at 120° C., and while the length in the width direction of the film was fixed, the film was heated at 230° C. for 0.5 seconds and further at 230° C. for 10 seconds 3 % Relaxation in the width direction to obtain a polyester film having an easily-adhesive cured layer having a thickness of 0.05 μm and a substrate film having a thickness of 50 μm. The physical properties of the obtained polyester film were good as shown in Table 3. The characteristics of the coating liquid for the easy-adhesion cured layer are also shown in Table 3.
[Coating of coating liquid for hard coat layer]
The coating liquid (1) for the hard coat layer was applied onto the easily adhesive hardened layer of the obtained polyester film with a Mayer bar #5. Next, the film sample on which the coating layer (thickness 6.5 μm) was formed was allowed to stand in a hot air circulation oven set at a temperature of 60° C. for 30 seconds, and then the film sample was taken out from the oven and dried.
Then, the polyester film coated with the hard coat layer is conveyed into a conveyor type ultraviolet irradiation device (CS30, manufactured by GS Yuasarai Tech), and ultraviolet irradiation of 400 mJ/cm ² is performed, and the thickness of the hard coat layer is 1 μm. Thus, a hard coat polyester film having a substrate film thickness of 50 μm was obtained. The physical properties of the obtained hard coat polyester film were good as shown in Table 3.

Examples 2 to 21
As shown in Table 3, a hard coat polyester film was obtained in the same manner as in Example 1 except that the coating film thickness of the easy-adhesion cured layer and the type of coating solution were changed. The characteristics of each coating solution and the characteristics of the film are shown in Table 3.

Comparative Examples 1-16
As shown in Table 4, a hard coat polyester film was obtained in the same manner as in Example 1 except that the coating film thickness of the easily adhesive hardened layer and the hard coat layer and the type of the coating liquid were changed. The characteristics of each coating solution and the characteristics of the film are shown in Table 4.

From Table 3, Examples 1 to 21 of the present invention all showed good coating film properties and coating liquid properties.

The hard coat polyester film of the present invention has a hard coat layer that can suppress the occurrence of curl even when the thickness of the base polyester film is small, has high surface hardness, and has good adhesion to the base film. .. Therefore, the hard coat polyester film of the present invention is mainly used for displays and the like, and is a base material for functional films such as antireflection film, antiglare film, light diffusion sheet, lens sheet, near infrared ray blocking film, and transparent conductive film. Is useful as

Claims (5)

A hard coat polyester film having a hard coat layer on at least one side, wherein an easy-adhesion cured layer containing a reaction product of a water-soluble acrylic polyol and a water-soluble amino resin between the polyester film as a base material and the hard coat layer. And the water-soluble acrylic polyol has 40 to 80 mol% of constituent units having a hydroxy group in 100 mol% of all constituent units, and the reaction product of the water-soluble acrylic polyol and the water-soluble amino resin is A hard coat polyester film, which is a reaction product of 100 parts by mass of a water-soluble acrylic polyol and 10 to 70 parts by mass of a water-soluble amino resin. The hard coat polyester film according to claim 1, wherein the water-soluble acrylic polyol has a carboxy group. The hard coat polyester film according to claim 1 or 2, wherein the water-soluble amino resin is an alkylated melamine resin. The hard coat polyester film according to claim 1, wherein the easy-adhesion cured layer has a Martens hardness of 280 to 600 N/mm ² . The hard coat polyester film according to claim 1, wherein the hard coat layer contains an ionizing radiation curable compound.