JP7739948B2 - Active energy ray curable composition, cured product, and optical sheet - Google Patents

Description

The present invention relates to an active energy ray-curable composition, a cured product obtained by curing the composition, and an optical sheet made from the cured product.

Anti-reflection (LR) films used on the surfaces of flat panel displays (FPDs) such as liquid crystal displays (LCDs), organic light-emitting diode (OLED) displays, and plasma displays (PDPs) have a multilayer structure (substrate/high refractive index layer/low refractive index layer) in which two layers with a large difference in refractive index are formed on a film substrate. Each of these layers requires high scratch resistance (high hardness) to prevent scratches during the anti-reflection film manufacturing process, as well as high antistatic properties to prevent film contamination and blocking. Furthermore, because anti-reflection films are optical films, each layer also requires high transparency.

As a method for imparting the above-mentioned required properties, Patent Document 1 proposes the use of modified titanium oxide fine particles, in which a silane coupling agent has been reacted with the surface of titanium oxide, in combination with an antistatic agent.
Furthermore, an example has been disclosed in which a reaction product of colloidal silica and a silane coupling agent is used in combination with an antistatic agent (Patent Document 2).

Japanese Patent Application Laid-Open No. 2004-307579 JP 2013-144812 A

The curable compositions disclosed in the above documents do not contain phosphate esters, carboxylate esters, sulfate esters, or sulfonate esters.
On the other hand, particularly when zirconia is used as inorganic oxide particles, problems arise in compositions containing zirconia and an antistatic polymer, such as a decrease in the dispersibility of zirconia and gelation of the polymer, making it difficult for compositions using zirconia to satisfy the above-mentioned required properties.

The problem that the present invention aims to solve is to provide an active energy ray-curable composition capable of forming optical articles having a high refractive index, high hardness, antistatic properties, and transparency, a cured product obtained by curing the composition, and an optical sheet made from the cured product.

As a result of extensive research to solve the above-mentioned problems, the inventors of the present invention have found that by combining inorganic oxide particles such as zirconia and an antistatic polymer with a dispersant containing a compound such as a phosphate ester, it is possible to suppress a decrease in the dispersibility of the inorganic oxide particles and gelation of the polymer. They have also discovered that it is possible to achieve a high refractive index, high hardness, and antistatic properties without sacrificing transparency, and have thus completed the present invention.

That is, the present invention relates to the following inventions.
(1) An active energy ray-curable composition comprising a resin (A) having a polyalkylene glycol structure and a quaternary ammonium salt, inorganic oxide particles (B), a dispersant (C), and a hydrophilic solvent (D), wherein the dispersant (C) contains one or more of a phosphate ester, a carboxylate ester, a sulfate ester, and a sulfonate ester.
(2) The active energy ray-curable composition according to (1), wherein the inorganic oxide particles (B) are either or both of zirconium oxide particles and titanium oxide particles, and the inorganic oxide particles (B) are contained in an amount ranging from 10 to 70 mass% based on the total amount of solid components in the active energy ray-curable composition.
(3) The active energy ray-curable composition according to (1) or (2), wherein the dispersant (C) contains a phosphate ester, the mass ratio of the resin (A) to the dispersant (C) [(A)/(C)] is in the range of 1/5 to 5/1, and the mass ratio of the inorganic oxide particles (B) to the dispersant (C) [(B)/(C)] is in the range of 10/3 to 100/1.
(4) The active energy ray-curable composition according to any one of (1) to (3), wherein the hydrophilic solvent (D) contains at least one of methanol, ethanol, 1-propanol, 2-propanol, and 1-methoxy-2-propanol.
(5) The active energy ray-curable composition according to any one of (1) to (4), further comprising an active energy ray-curable compound (E), wherein the compound (E) is contained in an amount of 80 mass% or less based on the total amount of solid components in the active energy ray-curable composition.
(6) The active energy ray-curable composition according to (5), wherein the active energy ray-curable compound (E) contains at least a polyfunctional (meth)acrylate having three or more (meth)acryloyl groups.
(7) A cured product of the active energy ray-curable composition according to any one of (1) to (6) above, characterized in that the cured product has a refractive index of 1.55 or more.
(8) An optical sheet having a layer made of the cured product of (7) above.

By using a dispersant containing a phosphate ester or the like, the curable composition of the present invention can achieve suitable transparency while maintaining a high refractive index, high hardness, and antistatic properties. The cured product obtained by curing this composition has a high refractive index and hardness, as well as excellent antistatic properties and transparency, making it suitable for use in a variety of optical articles, such as prism sheets used in displays such as liquid crystal display devices, lenticular lens sheets used in stereoscopic photographs and projection screens, Fresnel lens sheets used in condenser lenses for overhead projectors, and diffraction gratings used in color filters, etc.

The active energy ray-curable composition of the present invention (hereinafter sometimes simply referred to as the "composition") contains a resin (A) having a polyalkylene glycol structure and a quaternary ammonium salt, inorganic oxide particles (B), a dispersant (C), and a hydrophilic solvent (D). It may also contain an active energy ray-curable compound (E), a photoinitiator (F), or other compounds. In the present invention, "(meth)acrylate" refers to either or both of acrylate and methacrylate, and "(meth)acryloyl group" refers to either or both of acryloyl group and methacryloyl group.

[Resin (A) Having a Polyalkylene Glycol Structure and a Quaternary Ammonium Salt]
The resin (A) having a polyalkylene glycol structure and a quaternary ammonium salt (hereinafter sometimes referred to as "component (A)") is a copolymer consisting of a polymerizable monomer (A-1) having a quaternary ammonium salt, a polymerizable monomer (A-2) having a polyalkylene glycol structure, and other optional components. The other optional components are not particularly limited, and may have any structure as long as they are polymerizable compounds copolymerizable with the polymerizable monomers (A-1) and (A-2). Alternatively, the other optional components may not be included as raw materials for component (A).

The polymerizable monomer (A-1) is a polymerizable monomer having a quaternary ammonium salt. Examples include compounds with a chloride counter anion, such as 2-[(meth)acryloyloxy]ethyltrimethylammonium chloride and 3-[(meth)acryloyloxy]propyltrimethylammonium chloride; compounds with a bromide counter anion, such as 2-[(meth)acryloyloxy]ethyltrimethylammonium bromide and 3-[(meth)acryloyloxy]propyltrimethylammonium bromide; and compounds with a non-halogen counter anion, such as 2-[(meth)acryloyloxy]ethyltrimethylammonium methylphenylsulfonate, 2-[(meth)acryloyloxy]ethyltrimethylammonium methylsulfonate, 3-[(meth)acryloyloxy]propyltrimethylammonium methylphenylsulfonate, 3-[(meth)acryloyloxy]propyltrimethylammonium methylsulfonate, 2-[(meth)acryloyloxy]ethyltrimethylammonium methylsulfate, and 3-[(meth)acryloyloxy]propyltrimethylammonium methylsulfate.

These polymerizable monomers (A-1) can be used alone or in combination of two or more.

Examples of the polymerizable monomer (A-2) include mono(meth)acrylates having a polyalkylene glycol structure, such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate, octoxypolyethylene glycol, octoxypolypropylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, stearoxypolyethylene glycol mono(meth)acrylate, phenoxypolyethylene glycol mono(meth)acrylate, phenoxypolyethylene glycol, phenoxypolypropylene glycol mono(meth)acrylate, nonylphenoxypolypropylene glycol mono(meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, and nonylphenoxypolypropylene glycol mono(meth)acrylate.

These polymerizable monomers (A-2) can be used alone or in combination of two or more.

Among the polymerizable monomers (A-2), mono(meth)acrylates having a polyethylene glycol structure or a polypropylene glycol structure are preferred, as they can further improve the antistatic properties of the cured coating film of the active energy ray-curable composition of the present invention, and among these, mono(meth)acrylates having a polyethylene glycol structure are more preferred.

The number-average molecular weight of the polyethylene glycol used as a raw material for the mono(meth)acrylate having a polyethylene glycol structure is preferably in the range of 200 to 8,000, more preferably 300 to 6,000, even more preferably 400 to 4,000, and particularly preferably 400 to 2,000, since this can further improve the antistatic properties of the cured coating film of the active energy ray-curable composition of the present invention.

The proportion of the polymerizable monomer (A-1) in the total amount of raw materials for component (A) is preferably in the range of 5 to 90% by mass, more preferably 20 to 80% by mass, and even more preferably 30 to 70% by mass, since this further improves the antistatic properties of the cured coating film of the active energy ray-curable composition of the present invention.

The proportion of the polymerizable monomer (A-2) in the total amount of raw materials for component (A) is preferably in the range of 1 to 90% by mass, more preferably in the range of 5 to 80% by mass, and even more preferably in the range of 10 to 50% by mass, since this can further improve the antistatic properties of the cured coating film of the active energy ray-curable composition of the present invention.

The weight-average molecular weight of component (A) is preferably in the range of 1,000 to 100,000, more preferably 2,000 to 50,000, and even more preferably 3,000 to 30,000, as this further improves the antistatic properties of the cured coating film of the active energy ray-curable composition of the present invention. Note that the weight-average molecular weight in the present invention is a value calculated in terms of polystyrene, measured by gel permeation chromatography (GPC).

The ratio of component (A) to the total amount of solid components in the composition of the present invention is preferably in the range of 0.1 to 50% by mass, more preferably in the range of 0.5 to 40% by mass, and even more preferably in the range of 1 to 30% by mass.

Component (A) can be used alone or in combination of two or more types.

[Inorganic oxide particles (B)]
The inorganic oxide particles (B) (hereinafter sometimes referred to as "component (B)") are particles of an inorganic compound such as a metal oxide. For example, zirconium oxide, titanium oxide, aluminum oxide, silicon oxide, antimony pentoxide, etc. are preferred, with oxides of Group 4 elements such as titanium oxide and zirconium oxide being more preferred, and zirconium oxide being most preferred.

Component (B) can be used alone or in combination of two or more types.

The refractive index of component (B) is preferably 1.54 or greater, more preferably 1.58 or greater, and most preferably 1.62 or greater.

The shape of the particles of component (B) is not particularly limited, but may be, for example, spherical, hollow, porous, rod-like, plate-like, fibrous, or amorphous, with spherical being preferred. The primary particle size is preferably 1 to 50 nm, with 1 to 30 nm being particularly preferred. The crystal structure is also not particularly limited, but a monoclinic system is preferred.

Inorganic oxide particles (B) have a higher refractive index than common organic materials, making them an effective means of increasing the refractive index of the cured product. However, it was necessary to consider the balance between the hardness, transparency, and antistatic properties of the cured product. Therefore, the inventors conducted various studies on the amount of component (B) used and discovered that 5 to 90% by mass, more preferably 8 to 80% by mass, and particularly preferably 10 to 70% by mass, based on the total amount of solid components in the composition of the present invention.

The range of 40 to 70 mass% is higher than the general blending amount of inorganic oxide particles, and is a range that could normally have a negative impact on the properties of the cured product of the composition. However, as described below, in this invention, the type and blending amount of dispersant contained in the composition was examined, and a composition was achieved in which the strength, transparency, and antistatic properties of the cured product are not likely to decrease, even when a large amount of component (B) is used to improve the refractive index.

[Dispersant (C)]
The dispersant (C) (hereinafter sometimes referred to as "component (C)") has an affinity with components (A) and (B) and thus serves to prevent aggregation of the inorganic oxide particles (B) in the composition. Specifically, it functions to affect the particle surface properties of the inorganic oxide particles (B), the interaction between particles of the inorganic oxide particles (B) component, and the interaction between the inorganic oxide particles (B) and materials other than component (B) in the composition of the present invention.

On the other hand, in compositions containing a resin (A) having a quaternary ammonium salt and inorganic oxide particles (B), the dispersibility of component (B) has decreased, and the resin (A) has gelled, making the composition difficult to cure and resulting in poor appearance such as reduced hardness or whitening of the cured product. Therefore, it has been difficult to manufacture optical sheets that take advantage of both the antistatic properties of resin (A) and the high refractive index of inorganic oxide particles (B).

The inventors therefore investigated various dispersants and discovered that the above problems do not occur when a mixture or compound containing at least one of carboxylic acid esters, sulfuric acid esters, sulfonic acid esters, or phosphate esters is used, and that an optical sheet with a high refractive index, high hardness, antistatic properties, and transparency can be achieved.

Specifically, they found that inorganic oxide particles (B) become more easily dispersed when anions such as phosphate groups contained in the ester bond with the inorganic oxide particles (B).

Component (C) preferably contains a carboxylic acid ester, a sulfonic acid ester, or a phosphate ester, and more preferably contains a phosphate ester.

The phosphate ester may be any of a phosphate monoester, a phosphate diester, and a phosphate triester, but a phosphate monoester is particularly preferred.

In particular, from the viewpoint of improving compatibility with polymerizable components other than component (C) in the composition, bleeding resistance, and hardness, it is more preferable that the phosphate ester have a (meth)acryloyl group in the molecule. For example, those represented by the following structural formula (1) are particularly preferred.

(In the formula, _R1 is a hydrogen atom or a methyl group, _R2 is an alkylene chain having 2 to 4 carbon atoms, x is an integer of 4 to 10, y is an integer of 1 or more, and n is an integer of 1 to 3.)

Hereinafter, dispersants containing phosphate esters will be referred to as phosphate ester-based dispersants.

Component (C) may also be a mixture containing at least one of a carboxylic acid ester, a sulfuric acid ester, a sulfonic acid ester, or a phosphate ester as an essential component, with various dispersants, including organosilicon compounds, blended in as optional components.

Specific examples of organosilicon compounds include hexamethyldisilazane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, and 3-methacryloxypropyltrimethoxysilane.

The amount of component (C) used is not particularly limited, but in the composition of the present invention, the mass ratio of the resin (A) to the dispersant (C) [(A)/(C)] is preferably in the range of 1/50 to 50/1, more preferably 1/20 to 20/1, and most preferably 1/5 to 5/1.

Furthermore, in the composition of the present invention, the mass ratio [(B)/(C)] of the inorganic particle dispersant (B) to the dispersant (C) is preferably in the range of 10/7 to 100/1, more preferably in the range of 10/5 to 100/1, and most preferably in the range of 10/3 to 100/1.

A dispersion with good stability can be obtained even when using a smaller amount of dispersant than is generally required.

[Hydrophilic Solvent (D)]
The hydrophilic solvent (D) (hereinafter sometimes referred to as "component (D)") is not particularly limited as long as it is an organic solvent that is highly miscible with water, and examples thereof include ether-based solvents, alcohol-based solvents, and nitrogen atom-containing solvents .
Specific examples of the solvent include ether solvents such as 1,2-dimethoxyethane, tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane; alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, t-butyl alcohol, ethylene glycol, propylene glycol, and 1-methoxy-2-propanol ; and solvents containing a nitrogen atom in the molecule such as acetonitrile, nitromethane, dimethylformamide, hexamethylphosphoric triamide, triethylamine, and pyridine.

Among the solvents exemplified as component (D), alcohol-based solvents such as ethanol, 1-propanol, 2-propanol, and 1-methoxy-2-propanol are preferred, with 1-propanol, 2-propanol, and 1-methoxy-2-propanol being more preferred, and 1-methoxy-2-propanol being most preferred.

Component (D) can be used alone or in combination of two or more types.

The inventors have discovered that the use of a hydrophilic solvent (D) can prevent a decrease in the dispersibility of the inorganic oxide particles (B) compared to when a non-hydrophilic solvent is used. Therefore, in the cured product of the composition of the present invention, the high refractive index component (B) is uniformly present, allowing the composition to exhibit a high refractive index.

[Active energy ray-curable compound (E)]
The composition of the present invention may contain, in addition to components (A) to (D), an active energy ray-curable compound (E) (hereinafter sometimes referred to as "component (E)"), provided that component (E) is a compound that does not fall under any of components (A), (C), and (D).

Component (E) is a polyfunctional (meth)acrylate. Examples include di(meth)acrylates of dihydric alcohols such as 1,4-butanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and tris(2-hydroxyethyl)isothiazolinone dimethacrylate. Di(meth)acrylate of socyanurate, di(meth)acrylate of diol obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol, di(meth)acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A, trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, tris(2-(meth)acryloyloxyethyl)isocyanurate, o-phenylphenoxyethyl (meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate Examples include dipentaerythritol acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

Furthermore, among the compounds of component (E) described above, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol tri(meth)acrylate are preferred because they improve the hardness of the cured coating film of the active energy ray-curable composition of the present invention. Of these, pentaerythritol tetra(meth)acrylate and pentaerythritol tri(meth)acrylate are more preferred, and pentaerythritol tetra(meth)acrylate is particularly preferred.

The active energy ray-curable composition of the present invention may also contain a urethane (meth)acrylate as component (E). The urethane (meth)acrylate is obtained by reacting a polyisocyanate with a (meth)acrylate having a hydroxyl group.

Examples of the polyisocyanate include aliphatic polyisocyanates and aromatic polyisocyanates, but aliphatic polyisocyanates are preferred because they can reduce discoloration of the cured coating film of the active energy ray-curable composition of the present invention.

The aliphatic polyisocyanate is a compound in which the moieties excluding the isocyanate groups are composed of aliphatic hydrocarbons. Specific examples of this aliphatic polyisocyanate include aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, and lysine triisocyanate; and alicyclic polyisocyanates such as norbornane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexylisocyanate), 1,3-bis(isocyanatomethyl)cyclohexane, 2-methyl-1,3-diisocyanatocyclohexane, and 2-methyl-1,5-diisocyanatocyclohexane. Trimers of the aliphatic polyisocyanates or alicyclic polyisocyanates can also be used as the aliphatic polyisocyanate. These aliphatic polyisocyanates can be used alone or in combination.

Examples of the (meth)acrylate having a hydroxyl group include 1,4-butanediol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and pentaerythritol tri(meth)acrylate, with pentaerythritol tri(meth)acrylate being particularly preferred.

The urethane (meth)acrylate may be obtained by addition reaction of one molecule of the polyisocyanate with multiple molecules of the (meth)acrylate having a hydroxyl group.

As the urethane (meth)acrylate synthesized from the above-mentioned compound, a compound having two or more polymerizable functional groups is preferred, a compound having three or more is more preferred, and a compound having four or more is even more preferred, as this improves the hardness of the cured coating film of the active energy ray-curable composition of the present invention.

These components (E) can be used alone or in combination of two or more.

From the viewpoint of improving the hardness and transparency of the cured coating film of the active energy ray-curable composition of the present invention, the amount of component (E) used is preferably 95% by mass or less, more preferably 85% by mass or less, and most preferably 80% by mass or less, based on the total amount of solid components in the composition.

[Photoinitiator (F)]
The active energy ray-curable composition of the present invention may contain a photoinitiator (F) (hereinafter, sometimes referred to as "component (F)"). Various initiators can be used, and preferred examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, thioxanthone and thioxanthone derivatives, 2,2'-dimethoxy-1,2-diphenylethan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one.

These (F) components can be used alone or in combination of two or more.

Of the compounds listed above, it is particularly preferable to use compounds that are highly soluble in water, i.e., highly hydrophilic, as component (F), such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one.

As described above, the composition of the present invention uses a hydrophilic resin having a polyalkylene glycol structure as component (A) and a hydrophilic solvent as component (D). Therefore, by using a highly hydrophilic compound as photoinitiator (F), compatibility with components (A) and (D) is improved, making it easier for component (A) to segregate on the coating film surface. Therefore, a cured product of a composition in which component (A), which acts as an antistatic agent, segregates on the surface, can exhibit excellent antistatic properties.

There are no particular restrictions on the amount of component (F) used, but because it is easier to achieve suitable curability, hardness, etc., it is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and particularly preferably 1 to 10 parts by mass, per 100 parts by mass of the active energy ray-curable compound (F) in the active energy ray-curable composition.

[Other ingredients]
The active energy ray-curable composition of the present invention does not inhibit the inclusion of other components other than components (A) to (F).

Typical examples of other components include solvents and fillers that do not fall under component (D).

Examples of solvents include ester solvents such as ethyl acetate, propyl acetate, and butyl acetate; and ketone solvents such as acetone, 2-butanone, methyl ethyl ketone, and methyl isobutyl ketone. These solvents can be used alone or in combination.

As a filler, for example, silica can be blended for the purpose of improving hard coat properties.
The silica is not limited, and known silica particles such as powdered silica and colloidal silica can be used. Examples of commercially available powdered silica particles include Aerosil 50 and 200 manufactured by Nippon Aerosil Co., Ltd., Sildex H31, H32, H51, H52, H121, and H122 manufactured by Asahi Glass Co., Ltd., E220A and E220 manufactured by Nippon Silica Industry Co., Ltd., SYLYSIA470 manufactured by Fuji Silysia Co., Ltd., and SG Flake manufactured by Nippon Sheet Glass Co., Ltd.
Furthermore, examples of commercially available colloidal silica include methanol silica sol, IPA-ST, MEK-ST, PGM-ST, NBA-ST, XBA-ST, DMAC-ST, ST-UP, ST-OUP, ST-20, ST-40, ST-C, ST-N, ST-O, ST-50, and ST-OL, all of which are manufactured by Nissan Chemical Industries, Ltd.

The silica may be reactive silica. Examples of the reactive silica include silica modified with a reactive compound. Examples of the reactive compound include a reactive silane coupling agent having a hydrophobic group, a compound having a (meth)acryloyl group, a compound having a maleimide group, and a compound having a glycidyl group.
Examples of commercially available powdered silica modified with a compound having a (meth)acryloyl group include Aerosil RM50 and R711 manufactured by Nippon Aerosil Co., Ltd., and examples of commercially available colloidal silica modified with a compound having a (meth)acryloyl group include MIBK-SD, MIBK-SD-L, MIBK-AC-2140Z, and MEK-AC-2140Z manufactured by Nissan Chemical Industries, Ltd. Other examples of reactive silica include silica modified with a glycidyl group such as 3-glycidoxypropyltrimethoxysilane, followed by an addition reaction with acrylic acid, and silica modified with a urethane reaction of 3-isocyanatepropyltriethoxysilane, a compound having a hydroxyl group, and a (meth)acryloyl group.

The shape of the silica fine particles is not particularly limited, and spherical, hollow, porous, rod-like, plate-like, fibrous, or irregularly shaped particles can be used. For example, commercially available hollow silica fine particles such as "Silinax (registered trademark)" manufactured by Nittetsu Mining Co., Ltd. can be used.
The primary particle size is preferably in the range of 5 to 200 nm. If the primary particle size is 5 nm or more, the inorganic fine particles are sufficiently dispersed in the composition, and if the primary particle size is 200 nm or less, the cured product can maintain sufficient strength.

The amount of silica blended is preferably 3 to 60% by mass based on 100% by mass of the composition.

[Cured product]
The active energy ray-curable composition of the present invention can be applied to a substrate or molded depending on the intended use, and then the solvent can be evaporated and the composition can be irradiated with active energy rays to form a cured product. Alternatively, the composition can be irradiated with active energy rays without using a substrate to form a cured product.

The substrate used to form the cured product can be a transparent substrate in the form of a film, sheet, or plate. The material of the substrate can be selected appropriately depending on the application, etc., and examples include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylic resins such as triacetyl cellulose, polycarbonate resin, methyl methacrylate copolymers, styrene resin, polysulfone resin, polyethersulfone resin, polycarbonate resin, vinyl chloride resin, polymethacrylimide resin, etc. Inorganic substrates such as glass substrates can also be used.

Examples of methods for applying the active energy ray-curable composition of the present invention to the substrate include die coating, microgravure coating, gravure coating, roll coating, comma coating, air knife coating, kiss coating, spray coating, dip coating, spinner coating, brush coating, solid coating using a silk screen, wire bar coating, and flow coating.

As described above, the active energy rays used to cure the active energy ray-curable composition of the present invention include ionizing radiation such as ultraviolet rays, electron beams, alpha rays, beta rays, and gamma rays. When ultraviolet rays are used as the active energy rays, examples of devices for irradiating the ultraviolet rays include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, electrodeless lamps (fusion lamps), chemical lamps, black light lamps, mercury-xenon lamps, short arc lamps, helium-cadmium lasers, argon lasers, sunlight, and LED lamps.

When a cured coating film of the active energy ray-curable composition of the present invention is formed on the substrate, the thickness of the cured coating film is preferably 20 nm or more, more preferably 35 nm or more, and even more preferably 50 nm or more, to ensure sufficient hardness of the cured coating film and to suppress curling of the film due to cure shrinkage of the coating film. However, the thickness can be changed appropriately depending on the application of the cured product, and is not particularly limited to this.

The cured product of the active energy ray-curable composition of the present invention preferably has a refractive index of 1.55 or higher, and more preferably 1.56 or higher. Because the cured product has a high refractive index and transparency, as well as suitable hardness, it can be suitably used in a variety of optical articles.

[Optical sheet]
The optical sheet of the present invention is an optical sheet having a layer made of a cured product of the above-mentioned active energy ray-curable composition. Examples of uses of the optical sheet include antireflection films used in flat panel displays (FPDs) such as liquid crystal displays (LCDs), organic electroluminescent displays (OLEDs), and plasma displays (PDPs). It is also envisioned that the optical sheet may be used as part of a polarizing plate used in cameras, sunglasses, aircraft and vehicle windows, etc. Other uses are not particularly limited as long as the purpose is surface protection or antireflection.

The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these examples as long as it does not depart from the gist of the invention. All parts and percentages in the examples are by weight unless otherwise specified.

(Production Example 1: Production of Resin (1) Having a Polyalkylene Glycol Structure and a Quaternary Ammonium Salt)
Nitrogen gas was introduced into a flask equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube, and the air in the flask was replaced with nitrogen gas. Thereafter, 55.0 parts by mass of 2-[(meth)acryloyloxy]ethyltrimethylammonium chloride, 20.0 parts by mass of cyclohexyl methacrylate, 25.0 parts by mass of methoxypolyethylene glycol methacrylate (NOF Corporation "Blemmer PME-1000"; number of repeating units n ≒ 23, molecular weight 1,000), and 300.0 parts by mass of methanol were added to the flask. Next, a solution obtained by dissolving 0.1 parts by mass of a polymerization initiator (azobisisobutyronitrile) in 3.0 parts by mass of methanol was added dropwise over 30 minutes, and the mixture was allowed to react at 65°C for 3 hours. The mixture was then diluted with methanol to obtain a 41% by mass solution of resin (1) having a polyalkylene glycol structure and a quaternary ammonium salt. The weight average molecular weight of the resulting resin (1) was 10,000.

(Production Example 2: Production of Resin (2) Having a Polyalkylene Glycol Structure and a Quaternary Ammonium Salt)
Nitrogen gas was introduced into a flask equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube, and the air in the flask was replaced with nitrogen gas. Thereafter, 58.0 parts by mass of 2-[(meth)acryloyloxy]ethyltrimethylammonium chloride, 20.0 parts by mass of cyclohexyl methacrylate, 22.0 parts by mass of methoxypolyethylene glycol methacrylate (NOF Corporation "Blemmer PME-1000"; number of repeating units n ≒ 23, molecular weight 1,000), and 300 parts by mass of methanol were added to the flask. Next, a solution obtained by dissolving 0.1 parts by mass of a polymerization initiator (azobisisobutyronitrile) in 3.0 parts by mass of methanol was added dropwise over 30 minutes, and the mixture was allowed to react at 65 ° C. for 3 hours. Methanol was then added to dilute the mixture, yielding a 41% by mass solution of resin (2) having a polyalkylene glycol structure and a quaternary ammonium salt. The weight average molecular weight of the resulting resin (2) was 15,000.

(Production Example 3: Production of Resin (3) Having a Quaternary Ammonium Salt)
Nitrogen gas was introduced into a flask equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube, and the air in the flask was replaced with nitrogen gas. Subsequently, 55.0 parts by mass of 2-[(meth)acryloyloxy]ethyltrimethylammonium chloride and 45.0 parts by mass of cyclohexyl methacrylate were added to the flask. Next, a solution prepared by dissolving 0.1 parts by mass of a polymerization initiator (azobisisobutyronitrile) in 3.0 parts by mass of methanol was added dropwise over 30 minutes, and the mixture was allowed to react at 65°C for 3 hours. Methanol was then added to dilute the mixture, yielding a 41% by mass solution of resin (3) containing a quaternary ammonium salt. The weight-average molecular weight of the resulting resin (3) was 10,000.

(Production Example 4: Production of Resin (4) Having a Quaternary Ammonium Salt)
Nitrogen gas was introduced into a flask equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube, and the air in the flask was replaced with nitrogen gas. Then, 35.0 parts by mass of 2-[(meth)acryloyloxy]ethyltrimethylammonium chloride, 65.0 parts by mass of butyl methacrylate, and 300 parts by mass of methanol were added to the flask. Next, a solution of 0.1 parts by mass of a polymerization initiator (azobisisobutyronitrile) dissolved in 3.0 parts by mass of methanol was added dropwise over 30 minutes, and the mixture was allowed to react at 65°C for 3 hours. Methanol was then added to dilute the mixture, yielding a 41% by mass solution of resin (4) containing a quaternary ammonium salt. The weight-average molecular weight of the resulting resin (4) was 10,000.

The weight-average molecular weights of the resins (1) to (4) obtained above were measured by gel permeation chromatography (GPC) under the following conditions:

Measurement equipment: High-speed GPC equipment ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mm I.D. x 30cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0 mL/min Injection volume: 100 μL (sample concentration 0.4% by mass in tetrahydrofuran solution)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

(Production Example 5: Preparation of Dispersion)
Zirconium oxide particle powder (Daiichi Kigenso Kagaku Kogyo Co., Ltd. "UEP-100", primary particle size: 11 nm) 166.4 parts by mass, 3-(meth)acryloyloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. "KBM-503") 16.6 parts by mass, phosphate ester dispersant (dispersant in which R ₁ in the structural formula (1) is a methyl group, R ₂ is an ethylene chain having 2 carbon atoms, x is 5, y is 2 (average value), and n is an integer of 1 to 3.) 25.0 parts by mass, methyl ethyl ketone 170.0 parts by mass were mixed and stirred for 30 minutes with a dispersion stirrer to perform coarse dispersion. Next, the resulting mixture was subjected to a dispersion treatment with a media-type wet disperser (Ashizawa Fine Tech Co., Ltd. "Star Mill LMZ-015") using zirconia beads having a particle size of 100 μm, with a residence time of 100 minutes, to obtain dispersion (1). The particle size of the sample in the middle of the process to which no dispersant was added was measured after adding a specified amount of dispersant and stirring.

(Examples 1 to 11, Comparative Examples 1 to 6)
Resin compositions were prepared by melt-mixing each compound and, if necessary, dispersion (1) to obtain the formulation shown in Table 1 below. The above-described evaluations were performed on the obtained resin compositions. The numerical values for the composition amounts in the table are in mass %. However, MeOH in the table refers to the amount contained as a solvent in the solutions of resins (1) to (4) prepared in Production Examples 1 to 4, and is not considered to be additionally added. Furthermore, the zirconia particles, dispersant, and MEK in Examples 1 to 11 and Comparative Examples 3 to 6 in the table are derived from dispersion (1) prepared in Production Example 5, and are not considered to be additionally added beyond the amounts contained in the dispersion.

Example 1
An active energy ray-curable composition (1) was obtained by uniformly mixing 26.8 parts by mass of the 41% by mass solution of resin (1) obtained in Production Example 1 (11.0 parts by mass as resin (1)), 72.7 parts by mass of the dispersion (1) obtained in Production Example 5 (containing 32.0 parts by mass of zirconia), 100.0 parts by mass of pentaerythritol tetraacrylate ("Aronix M450" manufactured by Toagosei Co., Ltd., containing less than 10% by mass of pentaerythritol triacrylate), 5.0 parts by mass of a photopolymerization initiator ("Irgacure 184" manufactured by BASF Japan Ltd.; 1-hydroxycyclohexyl phenyl ketone), and 419.4 parts by mass of propylene glycol monomethyl ether.

(Examples 2-11, Comparative Examples 1, 3 to 6)
As shown in Tables 1 and 2, the types and amounts of resins, compounds, and solvents were changed, and active energy ray-curable compounds (2) to (11), (R1), and (R3) to (R6) were obtained in the same manner as in Example 1. However, in Comparative Example 1, the dispersion (1) obtained in Production Example 5 was not added.

(Comparative Example 2)
An active energy ray-curable composition (R2) was obtained by uniformly mixing 26.8 parts by mass of the 41% by mass solution of resin (1) obtained in Production Example 1 (11.0 parts by mass as resin (1)), 32.0 g of zirconium oxide nanoparticle powder (product name: UEP-100, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., primary particle diameter 11 nm), 100.0 parts by mass of pentaerythritol tetraacrylate ("Aronix M450" manufactured by Toagosei Co., Ltd., containing less than 10% by mass of pentaerythritol triacrylate), 5.0 parts by mass of a photopolymerization initiator ("Irgacure 184" manufactured by BASF Japan Ltd.; 1-hydroxycyclohexyl phenyl ketone), and 428 parts by mass of propylene glycol monomethyl ether.

The following tests and evaluations were carried out using the active energy ray-curable compositions (1) to (11) and (R1) to (R6) obtained in Examples 1 to 11 and Comparative Examples 1 to 6 above.

[Preparation of evaluation samples]
The active energy ray-curable composition was applied to a 50 μm-thick PET film (trademark registered "Lumirror", manufactured by Toray Industries, Inc.) using a bar coater to give a film thickness of 2.5 μm, and after drying at 60°C for 1 minute, it was irradiated with an ultraviolet ray irradiation device (high-pressure mercury lamp, manufactured by iGraphics Co., Ltd.) in an air atmosphere at an irradiation light dose of 3 kJ/ ^m2 to obtain a polyester film having a cured coating film as an evaluation sample.

<Coating film appearance>
The state of the evaluation sample obtained above was visually observed.
The evaluation criteria are as follows:
◯: No whitening ×: No hardening due to gelation or particle sedimentation

<Haze (transparency)>
The haze value of the evaluation sample obtained above was measured using a haze meter ("NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS test method K7136:2000. A haze value of less than 1.0% was considered acceptable.

<Refractive index measurement>
The refractive index of the cured coating film of the evaluation sample obtained above was measured at a reference wavelength (589 nm) using a multi-wavelength Abbe refractometer (DR-M2) manufactured by ATAGO. The values in the table show the refractive index of the cured coating film. A value of 1.55 or higher is considered to be acceptable.

<Measurement of surface resistivity (evaluation of antistatic properties)>
The surface resistivity of the cured coating film of the evaluation sample obtained above was measured in accordance with JIS test method K6911-1995 using a high resistivity meter ("Hiresta-UPMCP-HT450" manufactured by Mitsubishi Chemical Analytech Co., Ltd.) at an applied voltage of 500 V for a measurement time of 10 seconds. A value of less than 5.0 × 10 ¹⁰ was considered to be acceptable.

<Pencil hardness>
The pencil hardness of the surface of the cured coating film of the evaluation sample obtained above was measured under a load of 750 g in accordance with JIS K5600-5-4 (1999). Five measurements were made for each hardness, and the hardness at which no scratches were observed four or more times was defined as the surface hardness of the laminated film. The pencil hardness was ranked in descending order of hardness as 2H, H, F, HB, and B, with H or higher being considered acceptable.

The abbreviations shown in Tables 1 to 3 represent the following compounds.
Dispersant: a mixture of 3-(meth)acryloyloxypropyltrimethoxysilane ("KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.) and a phosphate ester-based dispersant contained in dispersion (1) PGME: propylene glycol monomethyl ether (also known as 1-methoxy-2-propanol)
IPA: 2-propanol NPA: 1-propanol MEK: methyl ethyl ketone MeOH: methanol EtOAc: ethyl acetate PETTA: pentaerythritol tetraacrylate ("Aronix M450" manufactured by Toagosei Co., Ltd.)
UA: Urethane acrylate (Miramar PU610 manufactured by Bigen Specialty Chemical Co., Ltd., average functionality 6)
OPPEA: o-phenylphenoxyethyl (meth)acrylate ("Miramar M1142" manufactured by MIWON Co., Ltd.)
Photoinitiator: 1-hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by BASF Japan Ltd.)

It was confirmed that the cured product of the active energy ray-curable composition of the present invention has a high refractive index, high hardness, and antistatic properties without impairing transparency.
On the other hand, in Comparative Example 1, which did not contain inorganic oxide particles such as zirconia particles, the refractive index and hardness decreased. In Comparative Example 2, which did not contain a dispersant, gelation occurred, and in Comparative Examples 3 and 4, which used only a ketone-based solvent or an ester-based solvent, the inorganic oxide particles settled and did not harden. Therefore, no other measurements were performed in Comparative Examples 2 to 4. In Comparative Examples 5 and 6, when the resin containing a quaternary ammonium salt was replaced with a compound not containing a polyalkylene glycol structure, it was confirmed that transparency was significantly reduced. Furthermore, in Comparative Example 5, the surface resistance value exceeded the maximum measurable range, making measurement impossible.

Claims (6)

The composition contains a resin (A) having a polyalkylene glycol structure and a quaternary ammonium salt, inorganic oxide particles (B), a dispersant (C), and a hydrophilic solvent (D),
The dispersant (C) contains one or more of a phosphoric acid ester, a carboxylic acid ester, a sulfuric acid ester, and a sulfonic acid ester,
the hydrophilic solvent (D) contains at least one of 1-propanol, 2-propanol, and 1-methoxy-2-propanol;
Further containing an active energy ray-curable compound (E),
The active energy ray-curable compound (E) contains at least a polyfunctional (meth)acrylate having three or more (meth)acryloyl groups.
An active energy ray-curable composition. The inorganic oxide particles (B) are either or both of zirconium oxide particles and titanium oxide particles,
2. The active energy ray-curable composition according to claim 1, wherein the inorganic oxide particles (B) are contained in an amount of 10 to 70 mass % based on the total amount of solid components in the active energy ray-curable composition. The dispersant (C) contains a phosphate ester,
a mass ratio of the resin (A) to the dispersant (C) [(A)/(C)] is in the range of 1/5 to 5/1;
3. The active energy ray-curable composition according to claim 1, wherein a mass ratio of the inorganic oxide particles (B) to the dispersant (C) [(B)/(C)] is in the range of 10/3 to 100/1. The active energy ray-curable composition according to any one of claims 1 to 3 , wherein the active energy ray-curable compound (E) is contained in an amount of 80 mass% or less based on the total amount of solid components in the active energy ray-curable composition. A cured product of the active energy ray-curable composition according to any one of claims 1 to 4 , characterized in that the cured product has a refractive index of 1.55 or more. An optical sheet having a layer made of the cured product according to claim 5 .