JP7725812B2 - Hard coat layer-forming composition and hard coat film - Google Patents

Description

The present invention relates to a composition for forming a hard coat layer and a hard coat film.

Polarizing plate protective films for LCD displays and protective films for circular polarizers used in organic EL displays, etc., are formed with resin layers to provide various functions. Examples of resin layers include an antistatic layer to provide antistatic properties, an antireflection layer to reduce reflection, and a hard coat layer to improve surface hardness. The provision of a hard coat layer is particularly essential for display applications, and hard coat layers are not only used as a single layer, but also play an important role as an underlying layer when an antireflection layer is laminated.

As the applications of these polarizing plates have expanded to include LCD TVs, laptops, and other devices, a variety of other properties are now required, including anti-reflective properties that reduce reflections from fluorescent lights, anti-static properties that make it difficult for dust to adhere, and anti-fouling properties that allow fingerprints and other contaminants to be wiped away. Laptops, in particular, are prone to becoming soiled by fingerprints, sebum, sweat, cosmetics, and other contaminants as a result of human use. Polarizing plates generally have a high surface energy, making them prone to adhesion of such contaminants. Furthermore, the surface of the anti-reflective film is microscopically uneven, making it difficult to remove the contaminants. Furthermore, there is the problem that only the areas where such contaminants have adhered become highly reflective, making the contaminants more noticeable.

To solve these problems, various technologies have been proposed to form an anti-fouling layer on the surface of optical components that makes it difficult for dirt to adhere and, if it does adhere, makes it easy to wipe off.

For example, Patent Document 1 proposes an anti-fouling, abrasion-resistant anti-reflective article in which an anti-reflection coating composed primarily of silicon dioxide is applied to the surface of a substrate, and the surface is further treated with a compound containing an organosilicon substituent. Patent Document 2 similarly proposes an anti-fouling, abrasion-resistant CRT filter in which the surface of a substrate is coated with a silanol-terminated organopolysiloxane. Furthermore, Patent Document 3 proposes an anti-fouling, low-reflection plastic having, on its surface, an anti-reflection coating containing mono- and disilane compounds containing polyfluoroalkyl groups and halogen, alkyl, or alkoxy silane compounds.

It is also common for hard coat layers to contain various additives to improve performance, such as hot water resistance, weather resistance, scratch resistance, and abrasion resistance, depending on the application. In particular, when used in touch panel applications, various environmental resistance properties, such as heat resistance and water absorption resistance, are required. For this reason, additives must also have sufficient heat resistance to withstand the processing and use temperatures of the hard coat layer-forming composition. Patent documents 4 to 6, for example, disclose techniques for increasing the molecular weight of additives to improve their heat resistance.

Japanese Patent Application Publication No. 1-086101 Japanese Patent Application Publication No. 4-338901 Japanese Patent Application Laid-Open No. 61-247743 Japanese Patent Application Publication No. 10-338777 Japanese Patent Application Laid-Open No. 2003-40937 WO 2008/062860

However, no conventional hard coat film combines high heat resistance with anti-fouling properties such as fingerprint wipeability. Furthermore, additives added to hard coats to impart functionality decompose to some extent at high temperatures, making it difficult for them to fully demonstrate their functionality. Furthermore, the thermal decomposition products of the additives often accelerate degradation of the hard coat. Given these circumstances, there is a need for the development of a composition for forming a hard coat layer that meets the high heat resistance requirements of recent years.

The present invention was made in light of these problems, and aims to provide a composition for forming a hard coat layer and a hard coat film that can impart heat resistance and anti-fouling properties to a hard coat layer without the need for an anti-fouling layer, and that can impart high adhesion to the substrate as well as excellent curl resistance, scratch resistance, and surface hardness, allow for easy removal of stains, and form a hard coat layer that consistently has high visibility without deteriorating its properties.

As a result of extensive research by the inventors, it was discovered that using specific monomers with excellent heat resistance and adjusting the blending ratio of additives to the composition within a specific range are important in solving the above-mentioned problems.

One aspect of the present invention for solving the above-mentioned problems is a composition containing a polyfunctional (meth)acrylic monomer (A) selected from dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer , a monomer (B), a photoradical polymerization initiator (C), a fluorine-containing compound (D) having a photoradical polymerizable group, and a non-polymerizable additive (E), wherein the polyfunctional (meth)acrylic monomer (A) is selected from dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer, a monomer (B), a photoradical polymerization initiator (C), a fluorine-containing compound (D) having a photoradical polymerizable group, and a non-polymerizable additive (E), The blending ratio of the acrylic monomer (A) is 1% by weight or more and 99% by weight or less based on the total weight of the polyfunctional (meth)acrylic monomer (A) and the monomer (B), the blending amount of the photoradical polymerization initiator (C) is 0.01% by weight or more and 10% by weight or less based on the total weight of the polyfunctional (meth)acrylic monomer (A) and the monomer (B), the blending ratio of the fluorine-containing compound (D) having a photoradical polymerizable group is 0.01% by weight or more and 10% by weight or less based on the total weight of the polyfunctional (meth)acrylic monomer (A) and the monomer (B), and the blending ratio of the non-polymerizable additive (E) in the composition is 5. 0% by mass or less, the monomer (B) is either 4-hydroxyphenyl methacrylate or N-(4-hydroxyphenyl) methacrylamide , and the non-polymerizable additive (E) in the composition is either a coatability improver, an antifoaming agent, a thickener, an antistatic agent, inorganic particles, organic particles, an organic lubricant, an organic polymer compound, an ultraviolet absorber, a light stabilizer, a dye, a pigment, or a stabilizer .

A composition for forming a hard coat layer, wherein the content of the monomer (B) in the composition for forming a hard coat layer is 2 mol % or more and 50 mol % or less based on the sum of the polyfunctional (meth)acrylic monomer (A) and the fluorine-containing compound (D) having a photoradical polymerizable group.

A composition for forming a hard coat layer, comprising the polyfunctional (meth)acrylic monomer (A) in a proportion of 50% by weight or more and 95% by weight or less based on the total weight of the polyfunctional (meth)acrylic monomer (A) and the monomer (B).

A hard coat film characterized by having a hard coat layer formed by curing a hard coat layer-forming composition on a transparent substrate, the surface free energy of the hard coat layer being 20 mN/m or less, and the film thickness of the hard coat layer being 5 to 25 μm.

The present invention provides a hard coat layer-forming composition and hard coat film that can impart heat resistance and anti-fouling properties to a hard coat layer without the need for an anti-fouling layer, and can impart high adhesion to the substrate as well as excellent curl resistance, scratch resistance, and surface hardness, allowing for easy removal of stains and forming a hard coat layer that consistently has high visibility without deteriorating its properties.

1 is a cross-sectional view of a hard coat film according to one embodiment of the present invention.

The present invention relates to a composition for forming a hard coat layer and a hard coat film used for the purpose of protecting the surface of displays such as cathode ray tube displays (CRTs), liquid crystal displays (LCDs), plasma display panels (PDPs), and field emission displays (FEDs). More specifically, the present invention relates to a composition for forming a hard coat layer and a hard coat film that have high adhesion to the substrate, excellent heat resistance and anti-fouling properties, and can also impart excellent curl resistance, scratch resistance, and surface hardness.

The present inventors have investigated ways to impart antifouling properties to a hard coat layer on a transparent substrate and have found that the above-mentioned conventional problems can be solved by a hard coat layer-forming composition comprising the polyfunctional (meth)acrylic monomer (A) of the present invention, a monomer (B) having a partial structure represented by the following general formula (I) or (II), a photoradical polymerization initiator (C), a fluorine-containing compound (D) having a polymerizable group, and a non-polymerizable additive (E).

The following describes in detail the mode for implementing the present invention (hereinafter referred to as the "present embodiment").

The polyfunctional (meth)acrylic monomer (A) constituting the hard coat layer-forming composition of the present invention is preferably a compound in which the hydroxyl groups of a polyhydric alcohol having two or more alcoholic hydroxyl groups per molecule are esterified with two or more (meth)acrylic acids. Other examples that can be used include those in which reactive acrylic groups are bonded to an acrylic resin skeleton, as well as polyester acrylate, urethane acrylate, epoxy acrylate, and polyether acrylate, and those in which acrylic groups are bonded to a rigid skeleton such as melamine or isocyanuric acid. However, the use of urethane (meth)acrylate monomers and/or oligomers in particular can significantly improve the hardness and flexibility of the hard coat layer.

In the present invention, the term "(meth)acrylic monomer" refers to both "acrylic monomer" and "methacrylic monomer." For example, "polyfunctional (meth)acrylic monomer" refers to both "polyfunctional acrylic monomer" and "polyfunctional methacrylic monomer." Furthermore, the polyfunctional (meth)acrylic monomer (A) of the present invention and the monomer (B) having a partial structure represented by general formula (I) or (II) may be an oligomer.

The urethane acrylate used as the preferred polyfunctional (meth)acrylic monomer (A) in the present invention is generally one that can be easily formed by reacting a polyester polyol with an isocyanate monomer or prepolymer, followed by reaction of the resulting product with an acrylate monomer having a hydroxyl group. Specific examples include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer. These monomers can be used alone or in combination. In the coating liquid, these monomers may be monomers or partially polymerized oligomers.

Commercially available polyfunctional acrylic monomers include products from Mitsubishi Rayon Co., Ltd. (trade name "Diabeam" series, etc.), Nagase ChemteX Corporation (trade name "Denacol" series, etc.), Shin-Nakamura Chemical Co., Ltd. (trade name "NK Ester" series, etc.), Dainippon Ink and Chemicals, Inc. (trade name "UNIDIC" series, etc.), Toagosei Co., Ltd. (trade name "Aronix" series, etc.), Nippon Oil & Fats Corporation (trade name "Blenmar" series, etc.), Nippon Kayaku Co., Ltd. (trade name "KAYARAD" series, etc.), Kyoeisha Chemical Co., Ltd. (trade name "Light Ester" series, "Light Acrylate" series, etc.), and others.

The hard coat layer-forming composition of the present invention contains a monomer (B) having a partial structure represented by general formula (I) or (II).

In formula (I), Q _A represents an ester bond shown in the formula, R _A represents a substituent, n1 represents an integer of 1 to 5, * represents a bonding site to the remainder of the monomer represented by formula (I), and ** represents a bonding site to the phenyl group in the formula.

Examples of the substituent represented by R _A include an alkyl group (e.g., an alkyl group having 1 to 5 carbon atoms), a cycloalkyl group (e.g., a cycloalkyl group having 3 to 6 carbon atoms), an alkoxy group (e.g., a methoxy group or an ethoxy group), a hydroxyl group, an acetyl group, a nitro group, a cyano group, a carboxyl group, an amino group, an ester group, and a halogen atom. As mentioned above, n1 represents an integer of 1 to 5, and may be an integer of 1 to 3. When n1 is an integer of 2 or greater, a plurality of R _As may be the same or different, or some of them may be the same.

In formula (II), _QB represents a linking group other than the ester bond represented by _QA in formula (I) or a single bond, R _B represents a substituent, n2 represents an integer of 1 to 5, and * represents a bonding site to the remainder of the monomer represented by formula (II), with the proviso that at least one R _B represents a hydroxyl group.

As described above, _QB represents a single bond or a linking group other than the ester bond represented by _QA . Examples of the linking group other than the ester bond represented by _QA include -CONR- (R represents a hydrogen atom or an alkyl group), an alkylene group (for example, an alkylene group having 1 to 4 carbon atoms), a urethane bond, an ether bond, and an ester bond represented by *-O-CO-** (** represents the bonding site with the phenyl group in formula (II)).

Examples of the substituent represented by R _B include an alkyl group (e.g., an alkyl group having 1 to 5 carbon atoms), a cycloalkyl group (e.g., a cycloalkyl group having 3 to 6 carbon atoms), an alkoxy group (e.g., a methoxy group, an ethoxy group), a hydroxyl group, an acetyl group, a nitro group, a cyano group, a carboxyl group, an amino group, an ester group, a halogen atom, etc. However, as described above, at least one R _B represents a hydroxyl group.

As described above, n2 represents an integer of 1 to 5, or may be an integer of 1 to 3. When n2 is an integer of 2 or greater, multiple R 1 _B may be the same, all different, or some of the same. When multiple R 1 _B are the same, all of the R 1 _B are hydroxyl groups.

The monomer having the partial structure represented by the above-mentioned general formula (I) or (II) may be, for example, a (meth)acrylate-based monomer, a (meth)acrylamide-based monomer, an N-substituted maleimide-based monomer, or a styrene-based monomer.

When the monomer having the partial structure represented by the above-mentioned general formula (I) or (II) is a (meth)acrylate-based monomer, examples include 4-methoxyphenyl (meth)acrylate, 4-hydroxyphenyl (meth)acrylate, 2,6-di-tert-butylphenyl (meth)acrylate, 2,6-di-tert-butyl-4-methoxyphenyl (meth)acrylate, 2-tert-butyl-4-hydroxyphenyl (meth)acrylate, 3-tert-butyl-4-hydroxyphenyl (meth)acrylate, 2,6-di-tert-butyl-4-methylphenyl (meth)acrylate, 2-hydroxy-4-tert-butylphenyl (meth)acrylate, and 2,4-di-methyl-6-tert-butylphenyl (meth)acrylate.

When the monomer having the partial structure represented by the above-mentioned general formula (I) or (II) is a (meth)acrylamide-based monomer, examples include N-(4-hydroxyphenyl)(meth)acrylamide.

When the monomer having the partial structure represented by the above-mentioned general formula (I) or (II) is an N-substituted maleimide monomer, examples include 4-hydroxyphenylmaleimide and 3-hydroxyphenylmaleimide.

When the monomer having the partial structure represented by the above-mentioned general formula (I) or (II) is a styrene-based monomer, examples include α-methyl-p-hydroxystyrene.

The proportion of polyfunctional (meth)acrylic monomer (A) used is preferably 1 to 99% by weight, more preferably 50 to 95% by weight, based on the total of polyfunctional (meth)acrylic monomer (A) and monomer (B) having a partial structure represented by general formula (I) or (II). If the proportion of polyfunctional (meth)acrylic monomer (A) used is less than 50% by weight, it may be insufficient to obtain a hard coat layer with sufficient hardness, resulting in problems such as reduced pencil hardness of the hard coat layer formed. Furthermore, if the proportion of polyfunctional (meth)acrylic monomer (A) used is more than 95% by weight, it may result in problems such as significant curling of the hard coat film toward the cured coating due to cure shrinkage of polyfunctional (meth)acrylic monomer (A). Furthermore, the low proportion of monomer (B) having a partial structure represented by general formula (I) or (II) used may result in insufficient compatibility with fluorine-containing compound (D) having a polymerizable group, resulting in cloudy coating liquids and the formation of precipitates, making it unsatisfactory in terms of obtaining a hard coat composition with good storage stability.

The photoradical polymerization initiator (C) constituting the hard coat layer-forming composition of the present invention is preferably a compound that generates radicals upon exposure to ionizing radiation and initiates the polymerization reaction of the acrylic monomer.

Specific examples of photoradical polymerization initiators (C) include carbonyl compounds such as acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, p-isopropyl-α-hydroxyisobutylphenone, α-hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone, and 1-hydroxycyclohexyl phenyl ketone, and sulfur compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone. These photopolymerization initiators may be used alone or in combination of two or more.

The amount of photoradical polymerization initiator (C) used is preferably 0.01% by weight or more and 10% by weight or less, based on the total amount of polyfunctional (meth)acrylic monomer (A) and monomer (B) having a partial structure represented by general formula (I) or (II) in the hard coat layer-forming composition. If it is less than 0.01% by weight, the curing reaction will not proceed sufficiently when irradiated with ionizing radiation, and if it exceeds 10% by weight, ionizing radiation will not reach the lower part of the hard coat layer sufficiently.

By adding a fluorine-based additive to the fluorine-containing compound (D) having a polymerizable group that constitutes the hard coat layer-forming composition of the present invention, it is possible to impart anti-fouling properties to the surface of the hard coat layer. However, if a fluorine-based additive is added to a fluorine compound that does not have a polymerizable group, the additive will float on the surface of the hard coat layer and will be removed from the hard coat surface when wiped with a cloth or the like. This has the disadvantage that the anti-fouling properties are lost once the surface is wiped with a cloth or the like. In the present invention, by providing a polymerizable group to a fluorine compound with anti-fouling properties, the fluorine-based additive will also polymerize during hard coat layer formation, which has the advantage of maintaining the anti-fouling properties even when the surface is wiped with a cloth or the like.

It is even more preferable that the polymerizable group of the fluorine-containing compound (D) having a polymerizable group is a compound having a (meth)acrylate group. This is because the fluorine-containing compound (D) having a polymerizable group can also be copolymerized with a polyfunctional (meth)acrylate compound, allowing for high hardness to be achieved by radical polymerization using ionizing radiation.

Examples of such fluorine-containing compounds (D) having a polymerizable group of the present invention include Optool DAC (manufactured by Daikin Industries, Ltd.), SUA1900L10, SUA1900L6 (manufactured by Shin-Nakamura Chemical Co., Ltd.), UT3971 (manufactured by Nippon Synthetic Co., Ltd.), Defensa TF3001, Defensa TF3000, Defensa TF3028 (manufactured by Dainippon Ink Co., Ltd.), Light Procoat AFC3000 (manufactured by Kyoeisha Chemical Co., Ltd.), KNS5300 (manufactured by Shin-Etsu Silicones Co., Ltd.), UVHC1105, UVHC8550 (manufactured by GE Toshiba Silicones Co., Ltd.), and the like.

The amount of fluorine-containing compound (D) having a polymerizable group used in the present invention is suitably 0.01 to 10% by weight based on the total amount of polyfunctional (meth)acrylic monomer (A) and monomer (B) having a partial structure represented by general formula (I) or (II) in the hard coat layer-forming composition. If the amount is less than 0.01% by weight, sufficient antifouling properties will not be exhibited, and the surface energy will be greater than 20 mN/m. If the amount exceeds 10% by weight, poor compatibility with the polymerizable monomer and solvent will occur, causing the coating liquid to become cloudy and precipitation to occur, which may lead to problems such as defects in the coating liquid and hard coat layer.

In this embodiment, the content of monomer (B) having a partial structure represented by general formula (I) or (II) is preferably in the range of 2 mol % or more and 50 mol % of the sum of (meth)acrylic monomer (A) and fluorine-containing compound (D) having a polymerizable group. When the content of monomer (B) having a partial structure represented by general formula (I) or (II) is 2 mol % or more, thermal decomposition of the hard coat film and additives used in combination can be more effectively suppressed.

Furthermore, when the content of monomer (B) having a partial structure represented by general formula (I) or (II) is 50 mol% or less, the effect of suppressing thermal decomposition of the resin and any additives used in combination can be maintained, while yellowing of the resin when heated and the resin becoming hard and brittle can be effectively suppressed. From a similar perspective, the content of monomer (B) having a partial structure represented by general formula (I) or (II) may be 2 mol% or more and 30 mol% or less, or 2 mol% or more and 20 mol% or less.

In addition, in the present invention, non-polymerizable additives (E) such as coatability improvers, antifoaming agents, thickeners, antistatic agents, inorganic particles, organic particles, organic lubricants, organic polymer compounds, UV absorbers, light stabilizers, dyes, pigments, or stabilizers can be further added as modifiers for the hard coat layer. These additives are used as composition components of the coating layer that constitutes the hard coat layer within a range that does not impair the reaction due to actinic rays, and can improve the properties of the hard coat layer depending on the application. The blending ratio of the non-polymerizable additive (E) is 50% by mass or less of the total mass of the components other than the solvent in the hard coat layer-forming composition. Specific examples of non-polymerizable additives (E) are shown in Table 1.

The hard coat layer-forming composition of the present invention is preferably cured by irradiating it with actinic radiation, particularly ultraviolet radiation. The hard coat layer-forming composition can be cured by adding a photoradical polymerization initiator to the composition and irradiating it with ultraviolet radiation. For ultraviolet radiation, any light having a wavelength of 400 nm or less can be used, and examples of such lamps include ultra-high pressure mercury lamps, high pressure mercury lamps, medium pressure mercury lamps, low pressure mercury lamps, xenon lamps, and halogen lamps. A heating step may also be added as needed.

To prevent thermal polymerization during production and dark reactions during storage, it is desirable to add a thermal polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, or 2,5-t-butylhydroquinone to the hard coat layer-forming composition of the present invention. The amount of thermal polymerization inhibitor added is preferably 0.005 to 0.05% by weight based on the solids content of the hard coat layer-forming composition.

Figure 1 is a cross-sectional view of a hard coat film according to one embodiment of the present invention. As shown in Figure 1, the hard coat film of this embodiment comprises a hard coat layer on a transparent substrate. The hard coat layer is formed by applying the hard coat layer-forming composition of the present invention onto the transparent substrate.

The hard coat layer-forming composition can be applied using known coating methods such as a bar coater, applicator, doctor blade, roll coater, die coater, or commer coater. At this time, a solvent can be added to the hard coat layer-forming composition as needed. Examples of solvents include methyl isobutyl ketone, cyclohexanone, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, cyclopentanone, methylcyclohexanone, ethylcyclohexanone, 2-butanone, ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, n-pentyl acetate, and γ-butyrolactone, isobutyl acetate, butyl acetate, toluene, xylene, 2-propanol, 1-butanol, cyclopentanol, diacetone alcohol, and ethylene glycol. Examples of solvents that can be used include glycol monomethyl ether, propylene glycol monomethyl ether, dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, dioxane, dioxolane, trioxane, tetrahydrofuran, anisole, phenetole, methyl cellosolve, cellosolve, butyl cellosolve, cellosolve acetate, dichloromethane, trichloromethane, trichloroethylene, ethylene chloride, trichloroethane, tetrachloroethane, N,N-dimethylformamide, and chloroform. The solvent is not limited to one type, and a mixture of multiple solvents may be used.

A transparent substrate is preferably a light-transmitting film, as long as it has adequate transparency and mechanical strength. For example, films such as polyethylene terephthalate (PET), cellulose triacetate (TAC), diacetyl cellulose, acetyl cellulose butyrate, polyethylene naphthalate (PEN), cycloolefin polymer, polyimide, polyethersulfone (PES), polymethyl methacrylate (PMMA), and polycarbonate (PC) can be used. Among these, when a hard coat film is to be provided on the front surface of an LCD display, cellulose triacetate (TAC) is preferably used because it has no optical anisotropy.

The hard-coated film of the present invention has a hard-coating layer as the outermost layer. In this case, it is preferable that the surface energy of the hard-coating layer surface of the hard-coating film of the present invention is 20 mN/m or less.

Surface free energy can be used as an index for evaluating the antifouling properties of the hard coat layer surface, and this surface free energy can be used to estimate the presence or absence, and the level, of antifouling properties of the hard coat surface. Surface free energy can be calculated from the contact angle on the hard coat layer surface using the extended Fowkes equation, and the smaller this value, the better the antifouling properties. The hard coat film of the present invention has a surface free energy of 20 mN/m or less, and therefore possesses high antifouling properties.

In addition, in the hard coat film of the present invention, the surface free energy of the hard coat layer surface is preferably 15 mN/m or more. The smaller the surface free energy value, the better the antifouling properties of the hard coat film. However, if the surface free energy of the hard coat layer surface is less than 15 mN/m, it will be necessary to add a considerable amount of fluorine-containing compound (D) having a polymerizable group, which will whiten the hard coat layer-forming composition and make the hard coat film that is formed whitish, making the resulting hard coat film unsuitable for application to the surface of a display.

The thickness of the applied hard coat layer is determined by the required hardness, but a preferred thickness is 3 to 30 μm, and more preferably 5 to 25 μm. A thickness of less than 3 μm will not provide sufficient hardness, while a thickness of more than 30 μm will cause the transparent substrate to curl significantly due to cure shrinkage of the hard coat layer, resulting in problems such as breakage in the next process.

The hard-coated film of the present invention may optionally be provided with a functional layer. The functional layer is provided between the transparent substrate and the hard-coat layer or on the surface of the transparent substrate on the side where the hard-coat layer is not provided. Examples of such functional layers include an anti-reflection layer, an anti-static layer, an anti-glare layer, an electromagnetic wave shielding layer, an infrared absorbing layer, an ultraviolet absorbing layer, and a color correction layer. These functional layers may be used as a single layer, or multiple layers with different functions may be used. Hard-coated films having a hard-coat layer formed on a transparent substrate, and hard-coated films further provided with such functional layers, can be attached to the surfaces of various displays, such as liquid crystal displays, plasma displays, and CRT displays, making it possible to provide displays with excellent scratch resistance and stain resistance.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples. The performance of the hard coat film was evaluated according to the following method.

Haze: Measurements were performed in accordance with JIS-K7105 using a Nippon Denshoku NDH-2000 to determine the haze (%) of the hard coat film.

Total light transmittance: Measurements were performed in accordance with JIS-K7105 using a Nippon Denshoku NDH-2000, and the transmittance (%) of the hard coat film was determined.

Pencil hardness: Evaluation was performed in accordance with JIS-K5400 to determine the hardness of the hard coat layer of the hard coat film.

Scratch resistance: The hard coat layer of the hard coat film was rubbed 10 times with #0000 steel wool while applying a load of 250 g/ ^cm2 , and the occurrence of scratches was confirmed. The evaluation criteria were as follows:
○: No scratches ×: Scratches

Antifouling properties: A fingerprint was left on the surface of the hard coat layer of the hard coat film, and the fingerprint was wiped off with a cellulose nonwoven fabric (Pencot M-3, manufactured by Asahi Kasei Corporation) while applying a load of 250 g/ ^cm2 , and the ease of removal was judged visually. The evaluation criteria were as follows:
○: Fingerprints can be completely wiped off △: Fingerprints remain after wiping ×: Fingerprints cannot be wiped off

Surface energy: Using a contact angle meter (CA-X model, manufactured by Kyowa Interface Science Co., Ltd.), a 1.8 mm diameter droplet was created on the tip of a needle in a dry state (20°C, 65% RH), and this was then brought into contact with the surface of the hard coat layer to create a droplet. The contact angle is the angle between the tangent to the liquid surface at the point where the solid and liquid come into contact and the solid surface, and is defined as the angle on the side containing the liquid. Distilled water and n-hexadecane were used as the liquids. The contact angles of these two types of solutions were used to calculate the surface energy using the extended Fowkes formula.

Heat resistance: After forming a coating film of the composition for forming a hard coat layer on a glass substrate, a sample of about several mg was cut out from the glass substrate and sealed in an aluminum pan, and the mass loss rate (%) under a nitrogen atmosphere was measured by the following method. A simultaneous thermogravimetric and differential scanning calorimeter (STA7000, manufactured by Hitachi High-Tech Science Corporation) was used to measure the mass loss rate (%). The sample was heated at 250°C for 20 minutes under a nitrogen atmosphere, and the mass loss amount (M = M ₀ - M _{1 ) obtained by subtracting the mass after heating (M 1 )} from the initial mass before heating (M ₀ ) was divided by the initial mass (M ₀ ) to calculate the mass loss rate ([M/M ₀ ] × 100) (%). The lower the mass loss rate, the better the heat resistance.

Thermal degradation of additives: 0.1 parts by mass of a hindered amine light stabilizer (trade name: Tinuvin (registered trademark) 123, manufactured by BASF Japan Ltd.) was added to the hard coat layer-forming composition as an additive, and a hard coat layer containing the light stabilizer was formed on a glass substrate. The glass substrate on which the coating film was formed was heated at 250°C for 10 minutes, and the residual rate of the additive in the coating film was measured using the following method. The glass substrate was cut into pieces measuring 1 ^cm2 , immersed in 1.5 mL of acetone, and extracted in an ultrasonic cleaner for 60 minutes. The additives in the glass substrate extract were quantified using ultra-high performance liquid chromatography/mass spectrometry (UHPLC/MS) (ultra-high performance liquid chromatograph/mass spectrometer (UHPLC/MS), Agilent 1260 LC System/6130B Single Quad MS System). The amount of additive remaining after heating (V ₁ ) was divided by the initial amount of additive before heating (V ₀ ) to calculate the additive remaining rate ([V ₁ /V ₀ ]×100) (%).

The above evaluations used the hard-coated films of Examples 1 to 4 and Comparative Examples 1 to 4. The method for producing these hard-coated films is described below.

Example 1
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
The following components were stirred and mixed: urethane acrylate: dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, UA-306H (Kyoeisha Chemical Co., Ltd.) 80 parts by weight; acrylic monomer: 4-hydroxyphenyl methacrylate (Showa Denko Co., Ltd.) 10 parts by weight; initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight; fluorine-based compound: Optool DAC (Daikin Industries, Ltd.) 0.5 parts by weight; additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight; solvent: ethyl acetate 100 parts by weight. The resulting coating solution was applied to a substrate by a bar coating method to a cured film thickness of 12 μm, dried, and irradiated with ultraviolet light from a metal halide lamp at 400 mJ/ ^cm² to form a hard coat layer, thereby producing the hard coat film of Example 1. The hard coat film was measured for total light transmittance, haze, scratch resistance, pencil hardness, antifouling properties, and heat resistance, and the results are shown in Table 2.

Example 2
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, UA-306I (Kyoeisha Chemical) 80 parts by weight Acrylic monomer: 4-hydroxyphenyl methacrylate (Showa Denko) 10 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Fluorine-based compound: Optool DAC (Daikin Industries) 0.5 parts by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: ethyl acetate 100 parts by weight The above components were stirred and mixed to form a coating solution, which was applied to a substrate by a bar coating method to a cured film thickness of 12 μm, dried, and irradiated with ultraviolet light at 400 mJ/ ^cm2 using a metal halide lamp to form a hard coat layer, producing a hard coat film of Example 2. The total light transmittance, haze, scratch resistance, pencil hardness, antifouling properties, and heat resistance of this hard coat film were measured and the results are summarized in Table 2.

Example 3
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: UA-306H (Kyoeisha Chemical) 80 parts by weight Acrylic monomer: 4-hydroxyphenyl methacrylate (Showa Denko) 10 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Fluorine-based compound: Defensa TF3001 (DIC) 1.0 parts by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: 100 parts by weight of ethyl acetate The coating solution was stirred and mixed onto a substrate using a bar coating method to a cured film thickness of 12 μm, dried, and irradiated with ultraviolet light at 400 mJ/ ^cm2 using a metal halide lamp to form a hard coat layer, producing the hard coat film of Example 3. The results of measuring the total light transmittance, haze, scratch resistance, pencil hardness, antifouling properties, and heat resistance of this hard coat film are summarized in Table 2.

Example 4
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: UA-306H (Kyoeisha Chemical) 80 parts by weight Acrylic monomer: N-(4-hydroxyphenyl)methacrylamide (Fujifilm Wako Pure Chemical Industries) 10 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Fluorine-based compound: Optool DAC (Daikin Industries) 0.5 parts by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: methyl isobutyl ketone 100 parts by weight The resulting coating solution was stirred and mixed onto a substrate using a bar coating method to a cured film thickness of 12 μm, dried, and irradiated with ultraviolet light at 400 mJ/cm ² using a metal halide lamp to form a hard coat layer, producing the hard coat film of Example 4. The total light transmittance, haze, scratch resistance, pencil hardness, antifouling properties, and heat resistance of this hard coat film were measured and the results are summarized in Table 2.

<Comparative Example 1>
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: UA-306H (Kyoeisha Chemical) 80 parts by weight Acrylic monomer: 4-hydroxyphenyl methacrylate (Showa Denko) 10 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Non-polymerizable fluorine-based compound: Megafac F470 (DIC) 1.0 parts by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: 100 parts by weight of ethyl acetate The above components were stirred and mixed to form a coating liquid, which was applied to a substrate by a bar coating method to a cured film thickness of 12 μm, dried, and irradiated with ultraviolet light at 400 mJ/cm2 using a metal halide lamp to form a hard coat layer, producing a hard coat film of Comparative Example 1. The results of measuring the total light transmittance, haze, scratch resistance, pencil hardness, and antifouling properties of this hard coat film are summarized in Table 2.

<Comparative Example 2>
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: UA-306H (Kyoeisha Chemical) 80 parts by weight Acrylic monomer: 4-hydroxyphenyl methacrylate (Showa Denko) 10 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Silicone additive: BYK-UV3500 (BYK-Chemie) 1.0 part by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: 100 parts by weight of ethyl acetate The coating solution was stirred and mixed onto the substrate using a bar coating method to a cured film thickness of 12 μm, dried, and irradiated with ultraviolet light at 400 mJ/ ^cm2 using a metal halide lamp to form a hard coat layer, producing a hard coat film of Comparative Example 2. The total light transmittance, haze, scratch resistance, pencil hardness, and antifouling properties of this hard coat film were measured and the results are summarized in Table 2.

<Comparative Example 3>
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: UA-306H (Kyoeisha Chemical Co., Ltd.) 80 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Fluorine-based compound: Optool DAC (Daikin Industries, Ltd.) 0.5 parts by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: 100 parts by weight of ethyl acetate The mixture was stirred, but the coating liquid became cloudy and could not be evaluated.

<Comparative Example 4>
A cellulose triacetate film substrate having a thickness of 80 μm was used as a transparent substrate.
Urethane acrylate: UA-306H (Kyoeisha Chemical) 90 parts by weight Acrylic monomer: Styrene (Tokyo Chemical Industry Co., Ltd.) 10 parts by weight Initiator: Irgacure 184 (Ciba Specialty Chemicals) 1.5 parts by weight Fluorine-based compound: Optool DAC (Daikin Industries) 0.5 parts by weight Additive: Tinuvin 123 (BASF Japan) 0.1 parts by weight Solvent: Ethyl acetate 100 parts by weight Although the mixture was stirred, the coating liquid became cloudy and could not be evaluated.

The evaluation results for Examples 1 to 4 and Comparative Examples 1 and 2 are summarized in Table 2.

In Examples 1 to 4 and Comparative Examples 1 and 2, urethane acrylate was used as the polyfunctional (meth)acrylic monomer (A), and therefore all hard coat films had a pencil hardness of 3H and good scratch resistance.

Comparing Examples 1-4 with Comparative Examples 1 and 2, the hard coat films of Examples 1-4, which used a fluorine-containing compound (D) having a polymerizable group, exhibited sufficient antifouling properties and a good surface energy of 20 mN/m or less. In contrast, Comparative Examples 1 and 2, which did not use a fluorine-containing compound having a polymerizable group, did not exhibit sufficient antifouling properties and had a surface energy exceeding 20 mN/m. Furthermore, the use of a monomer (B) having a partial structure represented by general formula (I) or (II) can suppress heat-induced mass loss and additive degradation. However, in Comparative Examples 1 and 2, the use of a non-polymerizable fluorine-based compound and a non-polymerizable silicone-based compound reduced the uniformity of the coating film after photocuring, resulting in areas that were susceptible to thermal degradation. This is thought to be the reason for the high mass loss rate and low retention rate. A mass loss rate of 3% or less was considered good, and a retention rate of 95% or more was considered good.

Comparing Examples 1 to 4 with Comparative Examples 3 and 4, it is clear that the use of monomer (B) having a partial structure represented by general formula (I) or (II) improves compatibility with fluorine-based additives.

Claims (4)

a polyfunctional (meth)acrylic monomer (A) selected from dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer ;
Monomer (B),
a photoradical polymerization initiator (C);
A composition comprising a fluorine-containing compound (D) having a photoradical polymerizable group and a non-polymerizable additive (E),
the blending ratio of the polyfunctional (meth)acrylic monomer (A) is 1% by weight or more and 99% by weight or less based on the total weight of the polyfunctional (meth)acrylic monomer (A) and the monomer (B);
the amount of the photoradical polymerization initiator (C) is 0.01% by weight or more and 10% by weight or less based on the total amount of the polyfunctional (meth)acrylic monomer (A) and the monomer (B);
the blending ratio of the fluorine-containing compound (D) having a photoradical polymerizable group is 0.01% by weight or more and 10% by weight or less based on the total weight of the polyfunctional (meth)acrylic monomer (A) and the monomer (B),
the blending ratio of the non-polymerizable additive (E) in the composition is 50 mass% or less,
the monomer (B) is either 4-hydroxyphenyl methacrylate or N-(4-hydroxyphenyl) methacrylamide ,
a coating agent, a defoaming agent, a thickener, an antistatic agent, an inorganic particle, an organic particle, an organic lubricant, an organic polymer compound, an ultraviolet absorber, a light stabilizer, a dye, a pigment, or a stabilizer ; 2. The composition for forming a hard coat layer according to claim 1, wherein a content of the monomer (B) in the composition for forming a hard coat layer is 2 mol % or more and 50 mol % or less based on a sum of the polyfunctional (meth)acrylic monomer (A) and the fluorine-containing compound (D) having a photoradical polymerizable group. 3. The composition for forming a hard coat layer according to claim 1, wherein the polyfunctional (meth)acrylic monomer (A) is contained in an amount of 50% by weight or more and 95% by weight or less with respect to the total of the polyfunctional (meth)acrylic monomer (A) and the monomer (B). A hard coat film comprising a transparent substrate and a hard coat layer formed by curing the hard coat layer-forming composition described in any one of claims 1 to 3, wherein the surface free energy of the hard coat layer surface is 20 mN/m or less, and the film thickness of the hard coat layer is 5 to 25 μm.