WO2025254073A1 - Curable composition for forming overcoat layer - Google Patents

Abstract

[Problem] To provide a curable composition capable of forming an overcoat layer having improved impact resistance. [Solution] This curable composition for forming an overcoat layer comprises (a) a polyfunctional (meth)acrylate monomer, (b) organic hollow particles which each has a shell and a hollow part surrounded by the shell and which have an average particle diameter of 10-80 nm, and (c) a polymerization initiator. The organic hollow particles (b) are contained in an amount of 15-50 parts by mass per 100 parts by mass of the polyfunctional (meth)acrylate monomer (a), and the organic hollow particles (b) are particles of a poly((meth)acrylic acid ester).

Description

Curable composition for forming overcoat layer

The present invention relates to a curable composition useful as a material for forming an overcoat layer, and in particular to a curable composition capable of forming an overcoat layer that has excellent resistance to localized impact.

BACKGROUND ART Many electronic devices, such as smartphones, tablet devices, and other electronic and communication devices, office equipment, entertainment equipment, medical equipment, and lifestyle equipment, are equipped with display panels using liquid crystal display elements or organic EL display elements (liquid crystal displays (LCDs) and organic EL displays (OLEDs)).
These display panels are generally touch panel displays that have the ability to detect touch input from a stylus pen or a user's finger. Types that have a touch-recognition film (touch screen panel) attached to the surface of the panel, and in recent years, touch-integrated display panels have also been developed in which the touch electrodes necessary for touch recognition are incorporated inside the display panel when it is manufactured.

The surface of these touch panel displays is usually provided with a protective film (protective layer) called a hard coat layer to provide scratch resistance to prevent scratches on the display surface from fingernails and the like when the display is operated with fingers, anti-fouling properties to prevent fingerprints from adhering, and hardness to prevent deformation or breakage when a hard object comes into contact with the display surface.
For example, a polarizing plate protective film has been disclosed that has excellent pencil hardness and has a hard coat layer containing porous particles of an acrylic resin on at least one side of a film substrate for the purpose of preventing discoloration due to changes in temperature and humidity (Patent Document 1).
Furthermore, a substrate with a hard coating film, which is formed by blending hollow silicone-based microparticle aggregates with the aim of achieving high transparency and film strength, has been disclosed, and evaluation results of the pencil hardness and scratch resistance of the hard coating film have been disclosed (Patent Document 2).
Furthermore, in order to achieve a reduction in reflectance and a high total light transmittance, a hard-coated film (Patent Document 3) has been proposed, which has a hard-coating layer containing hollow silica fine particles or the like on at least one side of a polyester film, and a substrate with a hard-coating film containing hollow silica particles with internal cavities has been proposed as a hard-coating film having excellent adhesion to the substrate and scratch resistance (Patent Document 4).
Patent Document 5 discloses an antiglare hard-coated film that has a hard-coat layer containing organic fine particles that are not hollow particles on the surface of a transparent plastic film, and that controls the external haze value and 60° gloss value to desired values, has little variation in the external haze value depending on the film thickness, and is stable to produce and has excellent surface hardness (pencil hardness).

JP 2009-198811 A JP 2009-56673 A JP 2013-25116 A Patent No. 4540979 Patent No. 5259334

As described above, in the hard coat layer provided on the surface of a display, much research has been conducted on resistance to scratches and abrasions on the surface, such as pencil hardness and abrasion resistance.
However, it is difficult to say that sufficient consideration has been given to the resistance to localized impacts on the display surface, such as when a sharp object such as a stylus pen or ballpoint pen hits the display.

Color filters used in the above-mentioned liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays are provided with a transparent protective film (overcoat layer) for the purposes of improving durability against solvents, heat, etc., preventing impurities from passing through the color filter, and flattening the color filter.
The present inventors have conducted extensive research focusing on the resistance to local impacts on the LCD surface or OLED surface, and as a result have focused on imparting impact resistance not to a hard coat layer provided on the display surface, but to an internal layer constituting the display itself, such as an overcoat layer of a color filter.
The inventors have also found that by incorporating organic hollow particles into the overcoat layer, the impact resistance when a sharp object strikes the surface is improved, and have completed the present invention.

That is, the present invention provides, as a first aspect,
(a) a polyfunctional (meth)acrylate monomer,
A curable composition for forming an overcoat layer, comprising: (b) organic hollow particles having an average particle diameter of 10 nm to 80 nm, each having a shell and a hollow portion surrounded by the shell; and (c) a polymerization initiator,
The composition contains 15 to 50 parts by mass of the (b) organic hollow particles relative to 100 parts by mass of the (a) polyfunctional (meth)acrylate monomer,
the (b) organic hollow particles are poly(meth)acrylic acid ester particles;
The present invention relates to a curable composition for forming an overcoat layer.
As a second aspect, the present invention relates to the curable composition for forming an overcoat layer according to the first aspect, in which the (a) polyfunctional (meth)acrylate monomer includes a polyfunctional monomer having 3 to 6 (meth)acryloyl groups in one molecule.
As a third aspect, the present invention relates to the curable composition for forming an overcoat layer according to the first aspect or the second aspect, in which the (b) organic hollow particles are polymethyl methacrylate particles.
As a fourth aspect, the present invention relates to the curable composition for forming an overcoat layer according to the first aspect or the second aspect, further comprising (d) a surface modifier.
As a fifth aspect, the present invention relates to the curable composition for forming an overcoat layer according to the first aspect or the second aspect, further including (e) a solvent.
According to a sixth aspect, the present invention relates to the curable composition for forming an overcoat layer according to the first or second aspect, which does not contain inorganic particles and organic solid particles.
According to a seventh aspect, the present invention relates to a laminate including a film substrate and an overcoat layer on at least one surface of the film substrate, the overcoat layer being a cured product of the curable composition according to the first aspect or the second aspect.
An eighth aspect relates to a display device including the laminate according to the seventh aspect.

According to the present invention, it is possible to provide a curable composition for forming an overcoat layer, which can impart impact resistance to the overcoat layer.
Furthermore, according to the present invention, it is possible to provide a laminate having an overcoat layer obtained from the curable composition, a laminate having excellent impact resistance when a sharp object hits the surface, and a display device having the laminate.

<Curable composition for forming overcoat layer>
The curable composition for forming an overcoat layer of the present invention (hereinafter also simply referred to as the curable composition) specifically comprises:
(a) a polyfunctional (meth)acrylate monomer,
The present invention relates to a curable composition for forming an overcoat layer, which comprises (b) organic hollow particles having an average particle diameter of 10 nm to 80 nm and each having a shell and a hollow portion surrounded by the shell, and (c) a polymerization initiator, and the (b) organic hollow particles are poly(meth)acrylic acid ester particles in an amount of 15 parts by mass to 50 parts by mass per 100 parts by mass of the (a) polyfunctional (meth)acrylate monomer.
First, each of the above components (a) to (c) will be explained below.

[(a) Polyfunctional (meth)acrylate monomer]
In the curable composition of the present invention, examples of the (a) polyfunctional (meth)acrylate monomer include a monomer selected from the group consisting of polyfunctional (meth)acrylate compounds described below, a monomer selected from the group consisting of polyfunctional urethane (meth)acrylate compounds, oxyalkylene-modified products thereof (oxyalkylene-modified polyfunctional monomers), and a monomer selected from the group consisting of lactone-modified polyfunctional (meth)acrylate compounds.
The polyfunctional (meth)acrylate monomer (a) can be one selected from the group consisting of the various (meth)acrylate compounds described above, and can be used alone or in combination of two or more.
In the present invention, the term "(meth)acrylate compound" includes both acrylate compounds and methacrylate compounds, for example, "(meth)acrylic acid" includes acrylic acid and methacrylic acid. Furthermore, in the present invention, the term "(meth)acryloyl group" includes both acryloyl group and methacryloyl group.

In the present invention, preferred (a) polyfunctional (meth)acrylate monomers include polyfunctional monomers having at least two (meth)acryloyl groups per molecule, and more preferably polyfunctional monomers having at least three, for example, 3 to 6, (meth)acryloyl groups per molecule. Alternatively, (a) polyfunctional (meth)acrylate monomers include monomers selected from the group consisting of oxyalkylene-modified polyfunctional (meth)acrylate compounds having at least three (meth)acryloyl groups per molecule.

Among the (a) polyfunctional (meth)acrylate monomers, examples of the polyfunctional (meth)acrylate compounds (provided that they do not have a urethane bond) include trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, 1,3-propane Diol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, tricyclo[5.2.1.0 ^2,6 ] decanedimethanol di(meth)acrylate, dioxane glycol di(meth)acrylate, 2-hydroxy-1-acryloyloxy-3-methacryloyloxypropane, 2-hydroxy-1,3-di(meth)acryloyloxypropane, 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene, bis[4-(meth)acryloylthiophenyl]sulfide, bis[2-(meth)acryloylthioethyl]sulfide, 1,3-adamantanediol di(meth)acrylate, 1,3-adamantanedimethanol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate can be mentioned.
Among these, preferred polyfunctional (meth)acrylate compounds include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and mixtures of two or more thereof.

The polyfunctional urethane (meth)acrylate compound is a compound having a plurality of acryloyl groups or methacryloyl groups and one or more urethane bonds [—NHC(═O)O—] in one molecule, and may further have a urea bond [—NHC(═O)NH—].
Examples of the polyfunctional urethane (meth)acrylate compound include a compound obtained by reacting a polyfunctional isocyanate with a (meth)acrylate having a hydroxy group, and a compound obtained by reacting a polyfunctional isocyanate with a (meth)acrylate having a hydroxy group, and a polyol. However, the polyfunctional urethane (meth)acrylate compound that can be used in the present invention is not limited to these examples.

Examples of the polyfunctional isocyanate include tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate.
Examples of the (meth)acrylate having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and tripentaerythritol hepta(meth)acrylate.
Further examples of the polyol include diols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and dipropylene glycol; polyester polyols which are reaction products of these diols with aliphatic dicarboxylic acids or dicarboxylic anhydrides such as succinic acid, maleic acid, and adipic acid; polyether polyols; and polycarbonate diols.

In the oxyalkylene-modified product (oxyalkylene-modified polyfunctional monomer), examples of the oxyalkylene-modified include oxymethylene-modified, oxyethylene-modified, and oxypropylene-modified. Examples of the oxyalkylene-modified polyfunctional monomer include oxyalkylene-modified compounds of the polyfunctional (meth)acrylate compounds or polyfunctional urethane (meth)acrylate compounds. The oxyalkylene-modified polyfunctional monomers can also be used alone or in combination of two or more.
Examples of the oxyalkylene-modified polyfunctional (meth)acrylate compound include (meth)acrylate compounds of polyols modified with oxyalkylene. Examples of the polyols include glycerin, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, decaglycerin, polyglycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, and dipentaerythritol.

Furthermore, in the above-mentioned lactone-modified polyfunctional (meth)acrylate compound, ε-caprolactone can be used as the lactone used for lactone modification. Examples of the lactone-modified polyfunctional (meth)acrylate compound include ε-caprolactone-modified pentaerythritol tri(meth)acrylate, ε-caprolactone-modified pentaerythritol tetra(meth)acrylate, ε-caprolactone-modified dipentaerythritol penta(meth)acrylate, and ε-caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[(b) Organic hollow particles]
The component (b) is an organic hollow particle having a shell and a hollow portion surrounded by the shell, and an average particle size of 10 nm to 80 nm (hereinafter, also simply referred to as "organic hollow particle (b)").
In the curable composition of the present invention, the (b) organic hollow particles can impart impact resistance to the overcoat layer formed from the composition.

The (b) organic hollow particles have a shell (outer shell) made of an organic polymer layer. Compared with inorganic particles such as silica, the (b) organic hollow particles have a flexible shell and are expected to have better impact absorption.
In the organic hollow particles (b) of the present invention, poly(meth)acrylic ester particles containing poly(meth)acrylic ester as the polymer constituting the organic polymer layer can be used.
Examples of the poly(meth)acrylic acid ester include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate,
Examples include homopolymers of alkyl (meth)acrylates having 1 to 18 carbon atoms, such as cyclohexyl (meth)acrylate, mystyryl (meth)acrylate, cetyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate, and copolymers of two or more of these alkyl (meth)acrylates.

Furthermore, the organic polymer layer constituting the shell may contain a copolymer of the alkyl(meth)acrylate with an acrylic monomer such as (meth)acrylonitrile, (meth)acrylamide, (meth)acrylic acid, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, cumyl methacrylate, or dimethylaminomethyl (meth)acrylate; an aromatic vinyl monomer such as vinylpyridine, 2-acryloyloxyethyl phthalate, itaconic acid, fumaric acid, styrene, α-methylstyrene, p-methylstyrene, or p-chlorostyrene; a vinyl ester such as vinyl acetate or vinyl propionate; a halogen-containing monomer such as vinyl chloride or vinylidene chloride; or ethylene, propylene, or the like.
Furthermore, the organic polymer layer may be a homopolymer/copolymer of the alkyl(meth)acrylic acid ester crosslinked with a crosslinkable monomer, and examples of the crosslinkable monomer include di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, and ethylene oxide-modified trimethylolpropane tri(meth)acrylate. polyfunctional (meth)acrylic acid esters such as tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and further pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate; polyfunctional acrylamide derivatives such as N,N'-methylenebis(meth)acrylamide, N,N'-ethylenebis(meth)acrylamide; polyfunctional allyl derivatives such as butadiene, diallylamine, diallyl maleate, diallyl fumarate, diallyl succinate, tetraallyloxyethane, and triallyl isocyanurate; and aromatic allyl derivatives such as divinylbenzene, divinylnaphthalene, and diallyl phthalate.

Among these, polymethyl methacrylate particles can be preferably used as the (b) organic hollow particles. Hollow polymethyl methacrylate particles have the transparency and flexibility inherent to polymethyl methacrylate, and, combined with their hollowness, are suitable as particles with excellent impact resistance.
The polymethyl methacrylate particles (hollow particles) may be commercially available products, such as Techpolymer (registered trademark) NH, Techpolymer TP-NH, Techpolymer XX series (Sekisui Plastics Co., Ltd.).

The shape of the (b) organic hollow particles themselves can be, for example, bead-like and roughly spherical, and examples include roughly spherical particles or true spherical particles with an aspect ratio of 1.5 or less.

The average particle size of the (b) organic hollow particles used in the present invention is in the range of 10 nm to 80 nm, and for example, particles in the range of 30 nm to 80 nm can be used.
The average particle size (nm) used here refers to the average particle size measured by dynamic light scattering (DLS) (DLS average particle size: Z-average particle size). By setting the average particle size of the (b) organic hollow particles within the above range, a cured film having excellent impact resistance can be obtained.
The particle size distribution of the (b) organic hollow particles is not particularly limited, but they are preferably monodisperse fine particles with a uniform particle size.
The (b) organic hollow particles are preferably selected so that their average particle size, relative to the film thickness of a cured film obtained from the curable composition of the present invention described below, satisfies the range of (b) average particle size b/film thickness a = 0.01 to 1.0.

In the present invention, the (b) organic hollow particles are used in a proportion of 10 to 65 parts by mass, for example 15 to 50 parts by mass, and preferably 15 to 45 parts by mass, per 100 parts by mass of the aforementioned (a) polyfunctional (meth)acrylate monomer. If the content of the (b) organic hollow particles is too low, the impact resistance of the overcoat layer obtained from the curable composition may decrease. On the other hand, if the content of the (b) organic hollow particles is excessive, the surface flatness of the overcoat layer obtained from the curable composition may not be achieved.

Furthermore, the curable composition of the present invention may contain organic hollow particles other than the above-mentioned (b) organic hollow particles [poly(meth)acrylic acid ester hollow particles], for example, organic hollow particles whose shell (outer shell) organic polymer layer is made of polystyrene, polyimide, polyvinyl chloride, polyacetal, polyethylene terephthalate, etc., to the extent that the effects of the present invention are not impaired.

The curable composition of the present invention may contain inorganic particles (inorganic hollow particles, inorganic solid particles) and organic solid particles within a range that does not impair the effects of the present invention, but is preferably free of these inorganic particles and organic solid particles.
Even in an embodiment that does not contain these inorganic particles or organic solid particles, it is permissible to contain these particles at an impurity level.

[(c) Polymerization initiator]
The polymerization initiator (c) used in the curable composition of the present invention may be, for example, a polymerization initiator that generates radicals when exposed to active energy rays such as electron beams, ultraviolet rays, or X-rays, particularly ultraviolet rays.
Examples of the polymerization initiator (c) include benzoins, alkylphenones, thioxanthones, azos, azides, diazos, o-quinonediazides, acylphosphine oxides, oxime esters, organic peroxides, benzophenones, biscoumarins, bisimidazoles, titanocenes, thiols, halogenated hydrocarbons, trichloromethyltriazines, and onium salts such as iodonium salts and sulfonium salts. These may be used alone or in combination of two or more.
In the present invention, from the viewpoints of transparency, surface curability, and thin film curability, it is preferable to use alkylphenones as the polymerization initiator (c). By using alkylphenones, a cured film having improved impact resistance can be obtained.

Examples of the alkylphenones include α-hydroxyalkylphenones such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methylpropan-1-one, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one; α-aminoalkylphenones such as 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one; 2,2-dimethoxy-1,2-diphenylethan-1-one; and methyl phenylglyoxylate.

In the present invention, the (c) polymerization initiator is used in a proportion of 1 to 20 parts by mass, preferably 2 to 10 parts by mass, per 100 parts by mass of the (a) polyfunctional (meth)acrylate monomer.

[(d) Surface Modifier]
The curable composition of the present invention may contain (d) a surface modifier. As the (d) surface modifier used in the present invention, a fluorine-based surface modifier may be used.
A specific example of the fluorine-based surface modifier is a perfluoropolyether containing a poly(oxyperfluoroalkylene) group.

The number of carbon atoms in the alkylene group in the poly(oxyperfluoroalkylene) group is not particularly limited, but preferably is 1 to 4. That is, the poly(oxyperfluoroalkylene) group refers to a group having a structure in which divalent fluorocarbon groups having 1 to 4 carbon atoms and oxygen atoms are alternately linked, and the oxyperfluoroalkylene group refers to a group having a structure in which divalent fluorocarbon groups having 1 to 4 carbon atoms and oxygen atoms are linked. Specific examples include groups such as -[OCF ₂ ]- (oxyperfluoromethylene group), -[OCF ₂ CF ₂ ]- (oxyperfluoroethylene group), -[OCF ₂ CF ₂ CF ₂ ]- (oxyperfluoropropane-1,3-diyl group), and -[OCF ₂ C(CF ₃ )F]- (oxyperfluoropropane-1,2-diyl group).
The above oxyperfluoroalkylene groups may be used singly or in combination of two or more kinds, in which case the bonding of the multiple kinds of oxyperfluoroalkylene groups may be either block bonding or random bonding.

Among these, it is preferable to use a poly(oxyperfluoroalkylene) group having both --[OCF ₂ ]-- (oxyperfluoromethylene group) and --[OCF ₂ CF ₂ ]-- (oxyperfluoroethylene group) as repeating units.
Among these, the poly(oxyperfluoroalkylene) group is preferably a group containing repeating units -[OCF ₂ ]- and -[OCF ₂ CF ₂ ]- in a molar ratio of [repeating unit: -[OCF ₂ ]-]:[repeating unit: -[OCF ₂ CF ₂ ]-] = 2:1 to 1:2, and more preferably a group containing repeating units in a ratio of approximately 1: 1. The bonding of these repeating units may be either block bonding or random bonding.
The total number of repeating units of the oxyperfluoroalkylene group is preferably in the range of 5 to 30, and more preferably in the range of 7 to 21.
The weight average molecular weight (Mw) of the poly(oxyperfluoroalkylene) group measured by gel permeation chromatography in terms of polystyrene is 1,000 to 5,000, preferably 1,500 to 3,000.

In the present invention, as component (d), a perfluoropolyether containing a poly(oxyperfluoroalkylene) group, and having an active energy ray polymerizable group at the end of its molecular chain via a urethane bond (hereinafter also simply referred to as "perfluoropolyether having a polymerizable group at the end of its molecular chain") can be used.The end of the molecular chain of the perfluoropolyether may be either all ends or some ends of the molecular chain.When the molecular chain of the perfluoropolyether is linear, all ends and some ends of the molecular chain are both ends and one end of the linear molecular chain, respectively.
It should be noted that the perfluoropolyether having a polymerizable group at the end of the molecular chain excludes perfluoropolyethers having a poly(oxyalkylene) group between the poly(oxyperfluoroalkylene) group and the urethane bond.
Furthermore, the perfluoropolyether having a polymerizable group at the end of the molecular chain has excellent compatibility with component (a), thereby preventing the overcoat layer from becoming cloudy and enabling the formation of an overcoat layer that exhibits a transparent appearance.

Examples of the active energy ray-polymerizable group include a (meth)acryloyl group and a vinyl group.

The perfluoropolyether having a polymerizable group at the end of the molecular chain is not limited to those having one active energy ray-polymerizable group at the end of the molecular chain, but may have two or more active energy ray-polymerizable groups at the end of the molecular chain. For example, terminal structures containing active energy ray-polymerizable groups include structures of formulas [A1] to [A5] shown below, and structures in which the acryloyl group in these structures is replaced with a methacryloyl group.

 

An example of such perfluoropolyether having a polymerizable group at the end of the molecular chain is a compound represented by the following formula [2]:

(In formula [2], A represents one of the structures represented by formulas [A1] to [A5] and structures in which an acryloyl group in these structures is substituted with a methacryloyl group; PFPE represents the poly(oxyperfluoroalkylene) group (wherein the side directly bonded to ^L1 is the oxy terminal and the side bonded to the oxygen atom is the perfluoroalkylene terminal); ^L1 represents an alkylene group having 2 or 3 carbon atoms substituted with 1 to 3 fluorine atoms; each m represents an integer of 1 to 5; and ^L2 represents an (m+1)-valent residue obtained by removing OH from an (m+1)-valent alcohol.)

Examples of the alkylene group having 2 or 3 carbon atoms substituted with 1 to ₃ fluorine atoms include _-CH2CHF- , -CH2CF2-, _{-CHFCF2- , -CH2CH2CHF-} , _-CH2CH2CF2- , _{-CH2CHFCF2- and the like} , _{with -CH2CF2- being} preferred.

Examples of the partial structure (A-NHC(═O)O) _m L ² — in the compound represented by the above formula [2] include structures represented by the following formulas [B1] to [B12].


(In formulas [B1] to [B12], A represents one of the structures represented by formulas [A1] to [A5] and structures in which the acryloyl group in these structures is substituted with a methacryloyl group.)
Among the structures represented by the above formulas [B1] to [B12], formulas [B1] and [B2] correspond to the case where m = 1, formulas [B3] to [B6] correspond to the case where m = 2, formulas [B7] to [B9] correspond to the case where m = 3, and formulas [B10] to [B12] correspond to the case where m = 5.
Among these, the structure represented by formula [B3] is preferred, and the combination of formula [B3] and formula [A3] is particularly preferred.

Among the perfluoropolyethers having a polymerizable group at the end of the molecular chain, particularly preferred are compounds having a partial structure represented by the following formula [1]:
The partial structure represented by formula [1] corresponds to the portion obtained by removing A-NHC(═O) from the compound represented by formula [2].
In formula [1], n represents the total number of repeating units -[OCF ₂ CF ₂ ]- and the number of repeating units -[OCF ₂ ]-, and is preferably an integer in the range of 5 to 30, and more preferably an integer in the range of 7 to 21. The ratio of the number of repeating units -[OCF ₂ CF ₂ ]- to the number of repeating units -[OCF ₂ ]- is preferably in the range of 2:1 to 1:2, and more preferably in the range of approximately 1:1. The bonding of these repeating units may be either block bonding or random bonding.

In the present invention, when a perfluoropolyether having a polymerizable group at the end of the molecular chain is used, it can be used in a proportion of, for example, 0.05 parts by mass to 10 parts by mass, or 0.1 parts by mass to 5 parts by mass, relative to 100 parts by mass of the (a) polyfunctional (meth)acrylate monomer.
By using the perfluoropolyether having a polymerizable group at the end of the molecular chain in an amount of 10 parts by mass or less, it is possible to obtain an overcoat layer that is sufficiently compatible with (a) the polyfunctional (meth)acrylate monomer and that is less cloudy.

The perfluoropolyether having a polymerizable group at the end of the molecular chain is, for example, a perfluoropolyether represented by the following formula [3]:

(In formula [3], PFPE, L ¹ , L ² and m have the same meanings as in formula [2]), the hydroxy groups present at both ends of the compound represented by formula [3] are reacted with an isocyanate compound having a polymerizable group, that is, a compound in which an isocyanato group is bonded to a bond in the structure represented by formula [A1] to formula [A5] or in a structure in which the acryloyl group in these structures is substituted with a methacryloyl group (for example, 2-(meth)acryloyloxyethyl isocyanate, 1,1-bis((meth)acryloyloxymethyl)ethyl isocyanate, etc.), to form a urethane bond.

The poly(oxyperfluoroalkylene) group-containing perfluoropolyether, which is a specific example of the surface modifier (component (d)) of the curable composition of the present invention, may be a perfluoropolyether containing a poly(oxyperfluoroalkylene) group that has an active energy ray-polymerizable group at one end (one end) of its molecular chain via a urethane bond and a hydroxy group at the other end (the other end) of its molecular chain, or a perfluoropolyether containing a poly(oxyperfluoroalkylene) group as represented by the above formula [3] that has hydroxy groups at both ends of its molecular chain [a compound that does not have an active energy ray-polymerizable group]. An additional condition can be added that there must be no poly(oxyalkylene) group between the poly(oxyperfluoroalkylene) group and the urethane bond, and between the poly(oxyperfluoroalkylene) group and the hydroxy group.

(e) Solvent
The curable composition of the present invention may further contain (e) a solvent, that is, it can be used in the form of a varnish (film-forming material).
The solvent may be appropriately selected in consideration of its ability to dissolve and disperse the components (a) to (d) and, if desired, other additives described below, as well as workability during coating for forming a cured film (overcoat layer) described below, drying properties before and after curing, and the like.
For example, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, tetralin, etc.; aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, mineral spirits, cyclohexane, etc.; halides such as methyl chloride, methyl bromide, methyl iodide, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, o-dichlorobenzene, etc.; esters or ester ethers such as ethyl acetate, propyl acetate, butyl acetate, methoxybutyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate (PGMEA), etc.; diethyl ether, tetrahydrofuran (THF), 1,4-dioxane, methyl cellosolve, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether (PGMEA), etc. ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), di-n-butyl ketone, cyclopentanone, cyclohexanone; alcohols such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, isobutyl alcohol, tert-butyl alcohol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol; amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP); and sulfoxides such as dimethyl sulfoxide (DMSO), as well as mixtures of two or more of these solvents.

Furthermore, a solvent having a high boiling point can be used for the purpose of controlling the dispersibility of the (b) organic hollow particles during drying after coating.
Examples of such solvents include cyclohexyl acetate, propylene glycol diacetate, 1,3-butylene glycol diacetate, 1,4-butanediol diacetate, 1,6-hexanediol diacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxybutyl acetate, ethylene glycol, diethylene glycol, propylene glycol, 1,3-butylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, 3-methoxybutanol, dipropylene glycol dimethyl ether, and dipropylene glycol methyl-n-propyl ether.

The amount of (e) solvent used is not particularly limited, but is used at a concentration such that the solids concentration in the curable composition of the present invention is 1% to 70% by mass, preferably 5% to 50% by mass. Here, the solids concentration (also referred to as non-volatile content concentration) refers to the amount of solids (all components excluding the solvent component) relative to the total mass (total mass) of the components (a) to (d) (and, if desired, other additives) in the curable composition of the present invention.

[Other additives]
Furthermore, the curable composition of the present invention may contain, as needed, one or more of the additives that are generally added, such as a polymerization accelerator, a polymerization inhibitor, a photosensitizer, a leveling agent, a surfactant, an adhesion imparting agent, a plasticizer, an ultraviolet absorber, a light stabilizer, an antioxidant, a storage stabilizer, an antistatic agent, an inorganic filler, a pigment, and a dye, which may be blended alone or in combination, as long as the effects of the present invention are not impaired.

<Overcoat layer (cured film)>
The curable composition of the present invention can be applied (coated) onto a substrate to form a coating film, and the coating film can be cured by irradiating it with active energy rays such as ultraviolet rays to form an overcoat layer (cured film) on the substrate. That is, the overcoat layer in the laminate described below can be made of a cured product (cured film) of the curable composition of the present invention.
Examples of the substrate include various resins (polyesters such as polycarbonate, polymethacrylate, polystyrene, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN), polyurethane, thermoplastic polyurethane (TPU), polyolefin, polyamide, polyimide, epoxy resin, melamine resin, triacetyl cellulose (TAC), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene copolymer (AS), polyvinyl chloride (PVC), polypropylene (PP), norbornene resin, etc.), metal, wood, paper, glass, slate, etc. The shape of these substrates may be a plate, a film, or a three-dimensional molded product.
Furthermore, on the surface of the substrate, for example, a primer layer, an ultraviolet absorbing layer, an infrared absorbing layer, a near-infrared absorbing layer, an electromagnetic wave absorbing layer, a color correction layer, a refractive index adjusting layer, a weather-resistant layer, an antireflection layer, an antistatic layer, a discoloration preventing layer, a gas barrier layer, a water vapor barrier layer, a light scattering layer, an electrode layer, a color filter layer, or the like may be formed as a layer below the overcoat layer, and a plurality of layers below the overcoat layer may be laminated. The layer to be formed on the surface of the substrate is not particularly limited as long as it does not impair the effects of the present invention.

The method for applying the composition to the substrate can be selected appropriately from cast coating, spin coating, blade coating, dip coating, roll coating, spray coating, bar coating, die coating, inkjet printing, printing methods (relief printing, intaglio printing, lithographic printing, screen printing, etc.), etc., among which roll-to-roll methods can be used. Furthermore, from the viewpoint of thin-film application properties, relief printing, particularly gravure coating, can be used. It is preferable to filter the curable composition of the present invention before application using a filter with a pore size of approximately 0.2 μm, etc. If necessary, a solvent may be further added to the curable composition of the present invention when applying the composition. Examples of the solvent in this case include the various solvents listed above under [(e) Solvent].

After the curable composition of the present invention is applied to a substrate to form a coating film, the coating film is pre-dried as needed using a heating means such as a hot plate or an oven to remove the solvent (solvent removal step). The heating and drying conditions at this time are preferably, for example, 40°C to 120°C and about 30 seconds to 10 minutes.
After drying, the coating film is cured by irradiating it with active energy rays such as ultraviolet rays. Examples of active energy rays include ultraviolet rays, electron beams, and X-rays, with ultraviolet rays being particularly preferred. Examples of light sources that can be used for ultraviolet irradiation include sunlight, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, and UV-LEDs.
Thereafter, post-baking may be carried out, specifically by heating using a heating means such as a hot plate or an oven, to complete the polymerization.

The thickness of the cured film formed after drying and curing can typically be approximately 0.01 μm to 100 μm, or 0.01 μm to 50 μm, or 0.05 μm to 40 μm, or 0.1 μm to 35 μm, etc.

<Laminate>
The curable composition of the present invention can be used to produce a laminate having an overcoat layer on at least one surface (surface) of a film substrate. This laminate is also within the scope of the present invention. The laminate is intended for use in various display devices such as touch panels and liquid crystal displays.

The overcoat layer in the laminate of the present invention can be formed by a method including the steps of applying the curable composition of the present invention to a film substrate to form a coating film, removing the solvent by heating if necessary, and irradiating the coating film with active energy rays such as ultraviolet light to cure the coating film.

The film substrate can be a resin film from among the substrates listed above under Overcoat Layer (Cured Film). Examples include films made of polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyurethane, thermoplastic polyurethane (TPU), polycarbonate, polymethacrylate, polystyrene, polyolefin, polyamide, polyimide, triacetyl cellulose (TAC), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene copolymer (AS), polyvinyl chloride (PVC), and polypropylene (PP).

The film substrate may have, on its surface, for example, a primer layer, ultraviolet absorbing layer, infrared absorbing layer, near-infrared absorbing layer, electromagnetic wave absorbing layer, color correction layer, refractive index adjusting layer, weather-resistant layer, anti-reflection layer, anti-static layer, discoloration prevention layer, gas barrier layer, water vapor barrier layer, light scattering layer, electrode, color filter layer, etc., formed as an underlayer of the overcoat layer, or multiple underlayers of the overcoat layer may be laminated. There are no particular restrictions on the layers formed on the surface of the film substrate, as long as they do not impair the effects of the present invention.

Furthermore, the method of applying the curable composition of the present invention to the film substrate (coating film formation process) and the method of irradiating the coating film with active energy rays (curing process) can be the same as those listed above in <Overcoat layer (cured film)>. Furthermore, since the curable composition of the present invention contains a solvent (in the form of a varnish), a step of drying the coating film to remove the solvent can be included after the coating film formation process, if necessary. In this case, the method of drying the coating film (solvent removal process) listed above in <Overcoat layer (cured film)> can be used.

The thickness (film thickness) of the overcoat layer thus obtained can be set to be approximately 1 to 1000 times the average particle size of the (b) organic hollow particles. The thickness of the overcoat layer can be, for example, 0.01 μm to 100 μm, 0.01 μm to 50 μm, 0.05 μm to 40 μm, or 0.1 μm to 35 μm.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.
In the examples, the apparatus and conditions used for sample preparation and analysis of physical properties are as follows.

(1) Application by bar coater: TQC Sheen Automatic Film Applicator AB3125
Bar: A-Bar OSP-100 manufactured by OSG System Products Co., Ltd., maximum wet film thickness 100 μm (equivalent to wire bar #37)
Coating speed: 4 m/min (2) Oven equipment: Sanki Keiso Co., Ltd., two-layer clean oven (top and bottom type) PO-250-45-D
(3) UV curing device: CV-110QC-G manufactured by Heraeus Co., Ltd.
Lamp: Heraeus high-pressure mercury lamp H-bulb
(4) Gel Permeation Chromatography (GPC)
Apparatus: HLC-8420GPC manufactured by Tosoh Corporation
Column: TSKgel (registered trademark) G2000HXL, G3000HXL manufactured by Tosoh Corporation
Column temperature: 40°C
Eluent: tetrahydrofuran Detector: UV
(5) Laser microscope (pen drop test, dent depth measurement, crack confirmation)
Equipment: Keyence Corporation Digital Microscope VK-X250

The abbreviations have the following meanings:
Ac1: Polyfunctional acrylate [Aronix (registered trademark) M-933, manufactured by Toagosei Co., Ltd.]
PFPE1: A perfluoropolyether having the following structure, which has two hydroxy groups at each end of a molecular chain containing a poly(oxyperfluoroalkylene) group, without a poly(oxyalkylene) group interposed therebetween [Fomblin (registered trademark) T4 manufactured by Solvay Specialty Polymers, number average molecular weight of 2,200 calculated from the results of ¹⁹ F-NMR and ¹ H-NMR analysis]

(In the above formula, m is the number of repeating units -(CF ₂ CF ₂ O)-, and n is the number of repeating units -(CF ₂ O)-, satisfying 5≦(m+n)≦40, and m and n each independently represent an integer of 0 or greater, and when both repeating units are present, these repeating units are bonded in block bonds, random bonds, or block and random bonds.)
BEI: 1,1-bis(acryloyloxymethyl)ethyl isocyanate [Karenz (registered trademark) BEI, manufactured by Resonac Corporation]
DOTDD: dioctyltin dineodecanoate [Neostan (registered trademark) U-830, manufactured by Nitto Kasei Co., Ltd.]
O2959: 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methylpropan-1-one [Omnirad (registered trademark) 2959, manufactured by IGM Resins]
PGME: propylene glycol monomethyl ether, PGMEA: propylene glycol monomethyl ether acetate, HP1: organic hollow particle (polymethyl methacrylate hollow particle) dispersion [manufactured by Sekisui Plastics Co., Ltd., trade name Techpolymer (registered trademark) XX-6066Z, average particle diameter 65 nm, solid content concentration 10 mass %]
HP2: organic hollow particle (polymethyl methacrylate hollow particle) dispersion liquid [manufactured by Sekisui Plastics Co., Ltd., trade name Techpolymer (registered trademark) XX-7161Z, average particle diameter 80 nm, solid content concentration 10 mass%]
SP1: organic solid particles (polymethyl methacrylate solid particles) [manufactured by Sekisui Plastics Co., Ltd., trade name Techpolymer (registered trademark) SSX-103, average particle diameter 3 μm, used after being made into a dispersion with a solid content concentration of 40 mass%]

[Production Example 1] Production of perfluoropolyether (S1) having four acryloyl groups via urethane bonds at each end of a molecular chain containing a poly(oxyperfluoroalkylene) group. 1.19 g (0.5 mmol) of PFPE1, 0.52 g (2.2 mmol) of BEI, 0.017 g of DOTDD (0.01 times the total mass of PFPE1 and BEI), and 1.67 g of PGMEA were charged into a screw tube. This mixture was stirred at room temperature (approximately 23 ° C.) for 24 hours using a stirrer tip to obtain a 50 wt% PGMEA solution of the target compound S1. The weight average molecular weight (Mw) of the obtained S1 measured in polystyrene equivalent by GPC was 2,300, and the dispersity (Mw (weight average molecular weight) / Mn (number average molecular weight)) was 1.0.

[Examples 1 and 2, Comparative Examples 1 and 2]
The following components shown in Table 1 were mixed to prepare curable compositions having the solid content concentrations shown in Table 1. Here, the solid content refers to components other than the solvent (including the solvents shown in Table 1, the solvent of the surface modifier (solution), and the dispersion medium of each particle). In Table 1, [parts] represents [parts by mass] and [%] represents [% by mass].
Polyfunctional (meth)acrylate monomer: 100 parts by mass of a polyfunctional (meth)acrylate monomer shown in Table 1. Surface modifier: 0.8 parts by mass of a 50% by mass PGMEA solution of S1 (solid content: 0.4 parts by mass).
Particles: Particles (as solid content) shown in Table 1 in the amount shown in Table 1 Polymerization initiator: 5.0 parts by mass of O2959 Solvent: A solvent shown in Table 1 in an amount that results in a solid content concentration shown in Table 1

 

[Creation of cured film]
The curable compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were each applied to an A4-sized PET film with double-sided easy-adhesion treatment [Lumirror (registered trademark) U403, manufactured by Toray Industries, Inc., thickness 100 μm] using a bar coater to obtain a coating film. This coating film was dried in an oven at 65° C. for 3 minutes to remove the solvent.
The obtained film was exposed to UV light at an exposure dose of 700 mJ/ ^cm2 under a nitrogen atmosphere to produce a laminate having an overcoat layer (cured film) with a layer thickness (film thickness) of approximately 30 μm.
In the following description, the example numbers of the curable compositions will also be used as the example numbers of the overcoat layer and laminate, and the example numbers for evaluation in the drop impact test.

[Drop impact test (pen drop test)]
To evaluate the impact resistance of the overcoat layer, a pen drop test was carried out.
Each laminate was placed on a glass substrate with the overcoat layer facing up, and a pen with a thin, sharp tip (manufactured by DONG-A Co., Ltd., tip diameter: 0.3 mmφ, total length: 125 mm, weight: 10 g) was dropped from a height of 190 mm above the laminate (the distance from the laminate to the tip of the pen) so that the tip of the pen struck the overcoat layer perpendicularly.
Immediately after the test, the impact point was visually observed to check for dents or cracks, and the depth (maximum value) of the dent made on the surface of the overcoat layer by the impact was measured using a laser microscope. In this test, if the depth of the pen drop dent (dent) on the laminate having the overcoat layer is 50 μm or less, the overcoat layer can be evaluated as having high impact resistance.
The results obtained and the thickness of the overcoat layer are shown in Table 2.

 

As shown in Table 2, in Examples 1 and 2 in which organic hollow particles were blended, only shallow dents were observed after the pen drop test, and the dents (maximum depth) were also small. In addition, no cracks were observed around the dents.
On the other hand, in Comparative Example 1, which did not contain particles, not only dents but also cracks spreading from the dents were observed after the pen drop test. Furthermore, the dents in Comparative Example 1 were deeper than those in Examples 1 and 2, which resulted in a deterioration in impact resistance.
Furthermore, in Comparative Example 2, which contained organic solid particles, dents and cracks spreading from the dents were observed after the pen drop test. The dent depth was also larger than in Examples 1 and 2, confirming that the addition of organic solid particles was insufficient to improve impact resistance.

Claims (8)

(a) a polyfunctional (meth)acrylate monomer,
A curable composition for forming an overcoat layer, comprising: (b) organic hollow particles having an average particle diameter of 10 nm to 80 nm, each having a shell and a hollow portion surrounded by the shell; and (c) a polymerization initiator,
The composition contains 15 to 50 parts by mass of the (b) organic hollow particles relative to 100 parts by mass of the (a) polyfunctional (meth)acrylate monomer,
the (b) organic hollow particles are poly(meth)acrylic acid ester particles;
A curable composition for forming an overcoat layer. The curable composition for forming an overcoat layer according to claim 1, wherein the (a) polyfunctional (meth)acrylate monomer includes a polyfunctional monomer having 3 to 6 (meth)acryloyl groups per molecule. The curable composition for forming an overcoat layer according to claim 1 or claim 2, wherein the (b) organic hollow particles are polymethyl methacrylate particles. The curable composition for forming an overcoat layer according to claim 1 or claim 2, further comprising (d) a surface modifier. The curable composition for forming an overcoat layer according to claim 1 or claim 2, further comprising (e) a solvent. The curable composition for forming an overcoat layer according to claim 1 or claim 2, which does not contain inorganic particles or organic solid particles. A laminate comprising a film substrate and an overcoat layer on at least one surface of the film substrate, the overcoat layer being a cured product of the curable composition described in claim 1 or claim 2. A display device comprising the laminate according to claim 7.