JP7500899B2 - Active energy ray curable composition - Google Patents

Description

The present invention relates to an active energy ray-curable composition.

In order to expand the viewing angle of a display screen, it is necessary to make the screen material have a high refractive index, which can be achieved by increasing the amount of high refractive index nanoparticles in the material. Coating agents composed of high refractive index nanoparticles and UV monomers are prone to cracking in applications that require high temperature and long-term heat resistance, such as in-vehicle equipment. In particular, increasing the amount of nanoparticles to increase the refractive index makes cracking more likely to occur.
Polysiloxane is a material that is considered suitable for applications that require heat resistance, but the production of polysiloxane by hydrolysis and dehydration condensation of alkoxysilane must be carried out in the presence of a solvent. If the solvent is then distilled off after the polysiloxane is produced, the polysiloxane will have a higher molecular weight and will harden.

JP 2009-263522 A International Publication No. 2018/43407

The problem to be solved by the present invention is to obtain an active energy ray-curable composition that forms a coating film with excellent heat resistance and a high refractive index.

As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by using a specific composition, and have thus completed the present invention.
1. An active energy ray-curable composition containing the following (A) and (B) and containing substantially no solvent:
(A) Zirconium oxide fine particles; (B) A polysiloxane obtained by acetal-protecting silanol groups of a hydrolysis condensation product of alkoxysilanes; 2. The active energy ray-curable composition according to 1, which contains (C) a photopolymerizable monomer.
3. The active energy ray-curable composition according to 1 or 2, which contains (D) a polyfunctional thiol compound.

The active energy ray-curable composition of the present invention can provide an active energy ray-curable composition that forms a coating film having excellent heat resistance and a high refractive index.
Furthermore, during curing, thiol-mediated bonds are formed, which reduces cure shrinkage, and as a result, the occurrence of cracks in the cured film can be further prevented even in high-temperature environments.

The active energy ray-curable composition of the present invention satisfies the above requirements A to F, and will be described below in order.
<A. Zirconium oxide fine particles>
In the present invention, the zirconium oxide fine particles that can be used as component A may or may not be surface-treated, and may or may not be spherical.
The average particle size of the zirconium oxide particles is preferably 1 to 50 nm.
The thickness is more preferably 3 nm or more, even more preferably 5 nm or more, and most preferably 8 nm or more. The thickness is more preferably 30 nm or less, even more preferably 20 nm or less, and most preferably 15 nm or less.
The smaller the average particle size, the more improved the transparency of the cured coating film.
When the average particle size of the zirconium oxide fine particles is 1 nm or more, the dispersibility is improved. When the average particle size of the zirconium oxide fine particles is 50 nm or less, light scattering is unlikely to occur in the obtained hard coat layer, and the transparency of the hard coat layer is high. The average particle size of the zirconium oxide fine particles is determined by measuring the primary particle size by a dynamic light scattering method.

The content of the zirconium oxide fine particles in the active energy ray-curable composition of the present invention is preferably 10.0 to 70.0% by mass in order to obtain excellent coating hardness and a high refractive index.
Among them, 20.0 mass% or more is more preferable, 30.0 mass% or more is even more preferable, and 50.0 mass% or more is most preferable. Also, 67.0 mass% or less is more preferable, and 65.0 mass% or less is even more preferable.
When the content is within this range, the cured coating film has sufficient hardness and it is easy to achieve an appropriate refractive index.

<B. Polysiloxane obtained by acetal-protecting silanol groups of hydrolysis condensation products of alkoxysilanes>
As the polysiloxane obtained by acetal-protecting the silanol groups of the hydrolysis condensation product of alkoxysilanes according to the present invention, for example, a compound synthesized by the following method can be used.
(Hydrolysis and condensation products of alkoxysilanes)
The hydrolysis condensate of alkoxysilanes is a compound represented by the following formula (1), and can be obtained by a known method from a silane compound having a hydrolyzable group such as an alkoxyl group.
Formula (1)
^R1aSi ( ^OR2 )b(OH)cO(4-a-b-c)/2 (1)
(In the formula, ^R1 is one or more groups selected from a hydrogen atom or an organic group having 1 to 18 carbon atoms, ^R2 is one or more groups selected from a linear or branched alkyl group having 1 to 6 carbon atoms, and a, b, and c can be arbitrarily determined.)
R ¹ in the compound of the above formula (1) is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, and examples thereof include a hydrogen atom; alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group; cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, and a norbornyl group; alkenyl groups such as a vinyl group and an allyl group; aryl groups such as a phenyl group and a naphthyl group; halogen-substituted hydrocarbon groups such as a chloromethyl group, a γ-chloropropyl group, and a 3,3,3-trifluoropropyl group; and (meth)acryloxy-, epoxy-, mercapto-, and amino-substituted hydrocarbon groups such as a γ-(meth)acryloxypropyl group, a γ-glycidoxypropyl group, a 3,4-epoxycyclohexylethyl group, a γ-mercaptopropyl group, and a γ-aminopropyl group. Of these, a methyl group, a propyl group, a cyclohexyl group, a norbornyl group, a phenyl group, and a 3,4-epoxycyclohexylethyl group are preferable.

When the content a of ^R1 is smaller than 0.3, the content of tetrafunctional siloxane units is increased, and the film may be easily cracked. On the other hand, when a is larger than 1.6, the content of bifunctional siloxane units is increased, and while flexibility is imparted to the film, the content of silanol groups essential for expressing adhesion to the substrate and alkali solubility may be reduced.

^R2 is a linear or branched alkyl group having 1 to 6 carbon atoms, and the ^OR2 group is a siloxane terminal group other than a silanol group (Si-OH), and is generated by introducing an alkoxy residue derived from alkoxysilanes before hydrolysis or an alcohol used as a reaction solvent during the synthesis of alkoxysilanes into a siloxane. Specific examples include methoxy groups, ethoxy groups, propoxy groups, and butoxy groups. Since inexpensive methoxysilane and ethoxysilane are suitable as raw materials for polyorganosiloxane, the ^OR2 group is often a methoxy group or an ethoxy group, but is not limited to these.

The introduction of acid labile groups into the polysiloxane of the hydrolysis condensation product of alkoxysilanes of the above formula (1) is achieved by the reaction of silanol groups with an acid labile group raw material. Since alkoxy residues are not involved, the content b may be 0. If b is greater than 0.3, the proportion of alkoxy residues in the terminal group increases, and the total amount of silanol groups decreases relatively, so the amount of acid labile groups introduced decreases, which is not preferable because sufficient resolution cannot be obtained.
The amount of these alkoxy residues can be quantified by an alcohol quantification method using infrared absorption spectroscopy or alkali cracking, etc. In fact, the method is applicable even to amounts below the measurement limit.

The silanol group content c can be determined by measuring the ²⁹ Si-NMR of the polysiloxane and calculating the average chemical structure of the siloxane. That is, for example, among the T units (R ¹ Si-O ₃ /2) synthesized from a trifunctional hydrolyzable silane, the four types of structural units (T0 to T3) shown in the following formula (2) are observed as signals at different chemical shifts in the ²⁹ Si-NMR spectrum. The area of this signal indicates the abundance ratio of this structure, so the molar amount % of the terminal group (OX) can be calculated from the abundance ratio of T0, T1, and T2. The molar amount of silanol groups contained in the polysiloxane can be calculated by subtracting the remaining amount of alkoxy groups separately determined by IR spectrum or the like from this molar amount.
(Equation 2)
(X = H or ^R2 , and ^R1 is as defined above.)

When the content c of silanol groups (Si-OH) exceeds 2, it corresponds to a case where the compound contains a large amount of tetrafunctional siloxane units (Q) or contains only trifunctional siloxane units (T) in a dimer structure in which all ends are silanol groups. Such polysiloxanes are not preferred because they are low molecular weight and have poor film-forming ability, and the cured film has poor crack resistance. When c is less than 0.001, the content of acid labile groups introduced by the substitution of the present invention may become extremely small.

The molecular weight of this polysiloxane can be measured by gel permeation chromatography (GPC). It is preferable that the weight average molecular weight obtained from a calibration curve made based on standard polystyrene is in the range of 300 to 200,000. If it is less than 300, the film-forming properties and crack resistance may be poor, and if it is more than 200,000, the solubility in the developer during development may be significantly reduced.

Polysiloxanes can be synthesized by a conventionally known method. Examples of hydrolyzable alkoxysilanes as raw materials and silane compounds that can be used in combination include the following: vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldichlorosilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, 5-hexenyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyldimethoxymethylsilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyldiethoxymethylsilane, 3-(4-vinylphenyl)propyltrimethoxysilane, 4-vinylphenylmethyltrimethoxysilane, 4-vinylphenyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyl In addition to so-called silane coupling agents such as mercaptopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane, there can be used tetrachlorosilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, methyltriisopropenoxysilane, ethyltrichlorosilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrichlorosilane, Examples of the silane include propyltrimethoxysilane, propyltriethoxysilane, butyltrichlorosilane, butyltrimethoxysilane, hexyltrichlorosilane, hexyltrimethoxysilane, decyltrichlorosilane, decyltrimethoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane, cyclohexyltrichlorosilane, cyclohexyltrimethoxysilane, propylmethyldichlorosilane, propylmethyldimethoxysilane, hexylmethyldichlorosilane, hexylmethyldimethoxysilane, cyclohexylmethyldichlorosilane, cyclohexylmethyldimethoxysilane, phenylmethyldichlorosilane, phenylmethyldimethoxysilane, etc. In addition, it is also possible to use the desired silicon compound by combining hydrogen silanes such as trichlorohydrogensilane, trimethoxyhydrogensilane, and triethoxyhydrogensilane with an organic group having an unsaturated bond by hydrosilylation reaction.
The hydrolyzable silicon compounds may be used alone or in combination of two or more.

The hydrolyzable groups contained in the alkoxysilanes are preferably methoxy and ethoxy groups, because the reaction is easy to control and the use of chlorosilanes is not preferred because residual halogen ions are unsuitable for the purposes of the present invention.
As for the organic group, as described above, methyl group, propyl group, cyclohexyl group, norbornyl group, phenyl group, and 3,4-epoxycyclohexylethyl group are preferred, and in particular, phenyl group and 3,4-epoxycyclohexylethyl group are most suitable. It is preferable to use a silane compound having these hydrolyzable groups and organic groups as a raw material.

Methods for obtaining hydrolyzed condensates that can be used in the present invention by hydrolyzing and condensing the above-mentioned hydrolyzable alkoxysilanes include known methods for hydrolyzing hydrolyzable silane compounds in water or in water and an organic solvent.
The amount of water used for hydrolysis is 1 mole or more, preferably 1.2 moles or more, per mole of hydrolyzable group. If the amount of water is less than 1 mole, the hydrolysis of the hydrolyzable group only proceeds partially, and a relatively large amount of the hydrolyzable group remains unreacted. If a large amount of unreacted hydrolyzable group remains, the amount of silanol group decreases accordingly, which is not suitable for the purpose of the present invention.

A wide variety of organic solvents can be used, whether water-soluble or water-insoluble, but polar solvents are preferred because of their high solubility in silanol-containing siloxanes. Specific examples include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, t-butanol, and diacetone alcohol, as well as ethylene glycol, monoethylene glycol monoether, propylene glycol, and propylene glycol monoether. In particular, low-boiling alcohols such as methanol and ethanol, which are easy to distill off, are preferred as polysiloxanes suitable for the present invention.

Conventionally known hydrolysis catalysts and condensation catalysts can be used during the hydrolysis and subsequent condensation reaction. Particularly preferred are acidic hydrogen halides, carboxylic acids, sulfonic acids, acidic or weakly acidic inorganic salts, solid acids such as ion exchange resins, etc. Examples of these include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, organic acids such as acetic acid, maleic acid, oxalic acid, and methanesulfonic acid, and cation exchange resins having sulfonic acid groups or carboxylic acid groups on the surface. The amount of the hydrolysis catalyst is preferably 0.001 to 10 mol% per mol of hydrolyzable groups. In the present invention, organic acids such as phosphoric acid, acetic acid, and oxalic acid that can be decomposed by heating are preferred.
Strictly speaking, hydrolysis and condensation reactions cannot be separated, and condensation is partially proceeding during hydrolysis. Therefore, the acid catalyst functions as a catalyst in both reactions, but if the degree of condensation is to be increased, a separate condensation catalyst may be added. Examples of these condensation catalysts include, in addition to the acid compounds listed above, basic compounds such as ammonia and amines, and metal compounds such as ammonium salts, titanium, zinc, zirconium, and tin.

Next, a method for substituting the silanol groups of this polysiloxane with acid labile groups will be described. The acetal-protected polysiloxane of the present invention is a polyorganosiloxane (polysiloxane) represented by the above formula (1) in which some of the hydrogen atoms of the hydroxyl groups directly bonded to silicon atoms are substituted with acid labile groups represented by the following formula (3) and/or crosslinked intramolecularly or intermolecularly with crosslinking groups having a C-O-C group represented by the following general formula (4).
Equation (3)
(In the formula, R ³ and R ⁴ are each independently a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms. R ⁵ is a linear, branched or cyclic alkyl group having 1 to 30 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. R ³ and R ⁴ , R ³ and R ⁵ , and R ⁴ and R ⁵ may be bonded to each other to form a ring together with the carbon atom or the carbon atom and oxygen atom to which they are bonded, and when a ring is formed, R ³ , R ⁴ , and R ⁵ participating in the formation of the ring are a linear or branched alkylene group having 1 to 18 carbon atoms.)

Equation (4)
(In the formula, R ⁶ , R ⁷ , R ⁹ and R ¹⁰ each independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms. R ⁶ and R ⁷ , and R ⁹ and R ¹⁰ may be bonded to each other to form a ring together with the carbon atom to which they are bonded, and when a ring is formed, R ⁶ , R ⁷ , R ⁹ and R ¹⁰ participating in the formation of the ring are linear or branched alkylene groups having 1 to 17 carbon atoms. R ⁸ represents a divalent hydrocarbon group having 1 to 6 carbon atoms which may contain an oxygen atom.)

As the acid labile group in the above formula (3), examples of the alkyl group having 1 to 6 carbon atoms for ^R3 and ^R4 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a hexyl group, a cyclopentyl group, and a cyclohexyl group.

Examples of the linear, branched or cyclic alkyl group having 1 to 30 carbon atoms for ^R5 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-decyl group, an n-dodecyl group, an n-hexyl group, a palmityl group, an n-stearyl group, a cyclopropyl group, a cholesteryl group, a tetrahydropyranyl group, and a tetrahydrofuranyl group. Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, a tolyl group, an ethylphenyl group, a propylphenyl group, a dimethylphenyl group, a methylethylphenyl group, a naphthyl group, a furyl group, and a biphenyl group. Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group, a methylbenzyl group, a propylbenzyl group, and a dimethylbenzyl group.

In formula (4), examples of the linear, branched or cyclic alkyl group having 1 to 6 carbon atoms for R ⁶ , R ⁷ , R ⁹ and R ¹⁰ include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a cyclohexyl group, a cyclopentyl group, etc. Furthermore, examples of the divalent hydrocarbon group having 1 to 6 carbon atoms which may contain an oxygen atom for R ⁸ include, in addition to an alkylene group, the following:
Equation (5)
In the above formulas (3) and (4), when R ³ , R ⁴ , and R ⁵ or R ⁶ , R ⁷ , R ⁹ , and R ¹⁰ form a ring, examples of the ring include a tetrahydropyranyl group and a tetrahydrofuranyl group.

In the present invention, the polysiloxane obtained by acetal-protecting the silanol groups of the hydrolysis condensate of alkoxysilanes can be obtained by addition reaction of the above polysiloxane in the presence of an acid catalyst with alkenyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, sec-butyl vinyl ether, ethyl-1-propenyl ether, cyclohexyl vinyl ether, methyl-1-propenyl ether, isopropenyl methyl ether, isopropenyl ethyl ether, dihydrofuran, and dihydropyran, or dialkenyl ether compounds such as ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,3-propanediol divinyl ether, 1,3-butanediol divinyl ether, 1,4-butanediol divinyl ether, neopentyl glycol divinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol divinyl ether, and ethylene glycol diethylene vinyl ether.

Furthermore, as reaction conditions for introducing an acid labile group, aprotic polar solvents such as dimethylformamide, dimethylacetamide, tetrahydrofuran, 1,4-dioxane, ethyl acetate, etc. can be used as the solvent, either alone or in combination of two or more kinds. As the acid catalyst, hydrochloric acid, sulfuric acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, pyridinium p-toluenesulfonate, etc. can be used.

<C. Photopolymerizable Monomer>
(Monofunctional Monomer)
Among the photopolymerizable monomers that may be contained in the active energy ray-curable composition of the present invention, examples of monofunctional monomers include the following.
Benzyl (meth)acrylate, butyl (meth)acrylate, ethyl carbitol (meth)acrylate, 2-methoxyethyl (meth)acrylate, isooctyl (meth)acrylate, tridecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, 2 Examples of monofunctional (meth)acrylates include ethylhexyl carbitol (meth)acrylate, isoamyl (meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate, isotetradecyl (meth)acrylate, isobornyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, caprolactone (meth)acrylate, methoxytripropylene glycol (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, and EO (ethylene oxide)-modified succinic acid (meth)acrylate.
Other examples include acryloylmorpholine, acrylonitrile, acrylamide, diethylacrylamide, styrene, and (meth)acrylic acid.

When such a monofunctional monomer is contained, the amount of the monomer in the active energy ray curable composition is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 15.0% by mass or more. The amount of the monomer in the active energy ray curable composition is preferably 40.0% by mass or less, more preferably 30.0% by mass or less, and even more preferably 28.0% by mass or less.

(Polyfunctional Monomer)
The polyfunctional monomer is a compound having a plurality of carbon-carbon unsaturated bonds in the molecule, and for example, the following compounds can be used.
(Poly)alkylene glycol di(meth)acrylates such as vinyloxyethoxyethyl (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and tripropylene glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol diacrylate, trimethylol Examples of the acrylates include dipentaerythritol penta(meth)acrylate and ethylene oxide modified products thereof, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and ethylene oxide modified products thereof, dipentaerythritol penta(meth)acrylate and ethylene oxide modified products thereof, dipentaerythritol hexa(meth)acrylate and ethylene oxide modified products thereof, urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, pentaerythritol ethoxy tetraacrylate, caprolactam modified dipentaerythritol hexaacrylate, ethoxylated bisphenol A diacrylate, and alkoxylated tetrahydrofurfuryl acrylate.
When such a polyfunctional monomer is contained, the content thereof in the active energy ray-curable composition is 1.0 to 10.0% by mass.

<D. Polyfunctional thiol compounds>
The polyfunctional thiol compound is preferably at least one selected from the group consisting of pentaerythritol tetrakis(3-mercaptobutyrate), trimethylolpropane tris(3-mercaptobutyrate), and 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinane-2,4,6-trione.
Among them, tetrafunctional or higher thiol compounds are preferable, and can further reduce the viscosity.
Further, it is preferable to use a secondary thiol having three or more functional groups or a secondary thiol having four or more functional groups.
When these polyfunctional thiol compounds are contained, the content is preferably 0.5 to 10.0% by mass based on the total amount of the photopolymerizable component and the polyfunctional thiol compound. The content is more preferably 5.0% by mass or less, even more preferably 2.5% by mass or less, and most preferably 1.8% by mass or less. The content of the polyfunctional thiol compound is preferably as small as possible within a range in which the effect of adding the polyfunctional thiol compound can be exhibited.
By including a polyfunctional thiol compound, the viscosity of the composition is reduced and the heat resistance of the coating film is improved.

<Physical properties of the active energy ray-curable composition of the present invention and the cured product thereof>
The active energy ray-curable composition of the present invention preferably has a viscosity of 60 mPa·s or less, more preferably 50 mPa·s or less, and even more preferably 44 mPa·s or less, without the addition of a solvent. Such a low viscosity allows smooth printing or application when the composition is made into an ink-jet ink composition, an ink composition, or used as a surface coating composition.
The viscosity is measured at 25° C. using an E-type viscometer (RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.).
The cured product of the active energy ray-curable composition of the present invention preferably has a refractive index of 1.60 or more, more preferably 1.64 or more, and even more preferably 1.68 or more. Such a high refractive index makes the formed cured coating appear more transparent and provides excellent cosmetic properties. Furthermore, by forming a cured coating on the display surface of a display device, the viewing angle can be expanded.

<Photopolymerization initiator>
The photopolymerization initiator that can be incorporated in the active energy ray-curable composition of the present invention is not particularly limited.
Examples of photopolymerization initiators that can be used include the following: However, it is preferable not to use photopolymerization initiators that cause coloring, such as yellowing, of the coating film over time.
Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819), ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, benzophenone, diethylthioxanthone, 2-methyl-1-(4-methylthio)phenyl-2-morpholinopropan-1-one, 4-benzoyl-4'-methyldiphenyl sulfide, 1-chloro-4-propoxythioxanthone, isopropylthioxanthone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydro Examples of such compounds include 2,4,6-dimethyl-2-hydroxyphenyl phosphine oxide, 2,6-dimethyl-2-hydroxyphenyl phosphine oxide, 2,6-dimethyl-2-hydroxyphenyl phosphine oxide, 2,6-dimethyl-2-hydroxyphenyl phosphine oxide, 2,6-dimethyl-2-hydroxyphenyl phosphine oxide, 2,6-dimethyl-2-hydroxyphenyl phosphine oxide, 2,6-dimethyl-2-hydroxyphenyl phosphine oxide, and 2,6-dimethyl-2-hydroxyphenyl phosphine oxide.
The content of the photopolymerization initiator in the active energy ray-curable composition of the present invention is not particularly limited, and is preferably 0.3 to 1.5 parts by mass, more preferably 0.4 parts by mass or more, and more preferably 0.8 parts by mass or less, relative to 100 parts by mass of the photopolymerizable component.

<Sensitizer>
The active energy ray curable composition of the present invention can use a sensitizer (compound) that has light absorption properties in the wavelength range of 400 nm or more, mainly ultraviolet light, and exhibits a sensitizing function for the curing reaction by light of a wavelength in that range. If the composition is sufficiently curable, it does not need to be used. Note that the above-mentioned "exhibits a sensitizing function by light of a wavelength of 400 nm or more" means that the composition has light absorption properties in the wavelength range of 400 nm or more. By using such a sensitizer, the active energy ray curable composition of the present invention can improve the LED curability.

The sensitizer is preferably an anthracene-based sensitizer, but two or more sensitizers may be used in combination. Specifically, the sensitizer is an anthracene-based sensitizer such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, or 9,10-bis(2-ethylhexyloxy)anthracene. Representative examples of commercially available anthracene-based sensitizers include DBA and DEA (manufactured by Kawasaki Chemical Industries, Ltd.).

When a sensitizer is included, it is preferably 0 to 8.0% by mass relative to the total mass of the photopolymerizable components. If the amount exceeds 8.0% by mass, no improvement in effect is observed, and it is undesirable as it will result in excessive addition. If the sensitizer content exceeds 8.0% by mass, the ink composition will not see an improvement in the effect of adding the sensitizer, and there is a tendency for excessive addition to occur.

In addition, since the active energy ray-curable composition is clear and susceptible to changes in color, it is preferable that the active energy ray-curable composition does not contain a photosensitizer that may cause discoloration, such as a thioxanthone-based sensitizer.

<Other ingredients>
The active energy ray curable composition may contain various additives as optional components to exhibit various functionalities as necessary. The optional components include, for example, a surface conditioner, a light stabilizer, a surface treatment agent, an antioxidant, an antiaging agent, a crosslinking accelerator, a polymerization inhibitor, a plasticizer, a preservative, a pH adjuster, an antifoaming agent, a moisturizing agent, etc. In addition, the active energy ray curable composition may or may not contain a hindered amine compound, and it is preferable that the active energy ray curable composition does not contain a thiol group-containing polysilsesquioxane, a polyurethane (meth)acrylate, or an acrylic polymer.

(Surface conditioner)
The active energy ray curable composition preferably contains a surface conditioner. The surface conditioner is not particularly limited. Examples of the surface conditioner include silicone-based surface conditioners, fluorine-based surface conditioners, and acetylene-based surface conditioners. Acetylene diol-based surface conditioners include Dynol 607, Dynol 609, EXP-4001, EXP-4300, and Olfin E1010 (manufactured by Nissin Chemical Industry Co., Ltd.). Silicone-based surfactants include BYK-307, 333, 347, 348, 349, 345, 378, and 3455 (manufactured by BYK-Chemie). Fluorine-based surfactants include F-410, 444, and 553 (manufactured by DIC Corporation), and FS-65, 34, 35, 31, and 30 (manufactured by DuPont).
When a surface conditioner is contained, the content of the surface conditioner is not particularly limited. For example, the content of the surface conditioner is preferably an amount that allows the surface tension of the ink composition to fall within a range suitable for forming a coating film, and is more preferably 0.1 to 1.5% by mass in the ink composition.

(Polymerization inhibitor)
The polymerization inhibitor is not particularly limited. For example, the polymerization inhibitor may be a hindered amine such as an N-CH3 type, an N-H type, or an N-OR type, a phenol type, an amine type, a sulfur type, or a phosphorus type.

(Antifoaming agent)
The antifoaming agent may be a silicone-based antifoaming agent, a Pluronic-based antifoaming agent, or the like.

(Production of active energy ray-curable composition)
Next, a method for producing the active energy ray-curable composition of the present invention using these materials will be described.
The active energy ray-curable composition of the present invention can be obtained by dispersing and mixing using a dispersing machine such as a wet circulation mill, a bead mill, a ball mill, a sand mill, an attritor, a roll mill, a DCP mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a high-pressure homogenizer (Microfluidizer, Nanomizer, Ultimizer, Genus PY, DeBEE2000, etc.), a pearl mill, etc., and adjusting the viscosity of the active energy ray-curable composition as necessary.

(Application)
The active energy ray-curable composition of the present invention is particularly suitable for use on glass or a surface layer of a substrate that is made of a transparent non-absorbing material and that requires high hardness and abrasion resistance. It is preferable to use the composition on a surface layer made of a resin substrate as a non-absorbing material, and further, it is preferable to use the composition on a surface layer made of a vinyl chloride polymer or an ethylene-vinyl acetate copolymer, a vinyl chloride resin, polyethylene terephthalate, polycarbonate, or the like as the resin, in terms of water resistance, etc. It is also preferable to use the composition on a surface layer made of a polyethylene terephthalate (PET), a vinyl chloride resin, polycarbonate, tarpaulin, an acrylic resin, or the like as the resin, in terms of adhesion, etc.
As a means for forming a coating of the active energy ray-curable composition of the present invention on the surface of these substrates, known coating means or printing means can be used.
The cured product of the active energy ray-curable composition of the present invention does not have adhesiveness or tackiness.

Specifically, a method for forming and curing a pattern using the active energy ray-curable composition of the present invention can involve forming a coating film or a pattern on any substrate using a known coating device such as a bar coater, and then curing the coating film or the pattern by irradiation with active energy rays.
Another method includes ejecting the active energy ray-curable composition of the present invention onto a substrate using an inkjet head, and then exposing the coating of the composition of the present invention that has landed on the substrate to light to cure it.
For example, ejection onto a substrate (printing of an image) can be carried out by supplying the active energy ray-curable composition of the present invention to a printer head for inkjet printing that is compatible with low viscosity inks, and ejecting the ink composition from the printer head so that the coating film on the substrate has a thickness of, for example, 1 to 60 μm. Furthermore, exposure to light and curing (curing of an image) can be carried out by irradiating light onto the coating film of the active energy ray-curable composition of the present invention that has been applied onto the substrate as an image.
As a device for printing the active energy ray-curable composition of the present invention, a conventionally used printer device for inkjet pattern formation can be used, etc. As a light source for curing the coating film, ultraviolet light (UV lamp), ultraviolet light (light-emitting diode (LED)), electron beam, visible light, etc. are exemplified, and from an environmental standpoint, a light-emitting diode (LED) that generates ultraviolet light with an emission peak wavelength in the range of 350 to 420 nm is preferable.
Ultraviolet light emitted from a light emitting diode (LED) as a light source is defined as "light emitted from a light emitting diode that generates ultraviolet light with an emission peak wavelength in the range of 350 to 420 nm."

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".
The materials used in the following Examples and Comparative Examples are as follows: In the tables, the units of values in the columns relating to pigment, dispersant, resin, solvent and total are "mass %".

(Film curability)
The curability of the coating film after UV irradiation was evaluated based on the presence or absence of tack on the coating film surface.
UV irradiation intensity: 180 mJ/ ^cm3
Coating thickness: 1-2 μm
○ (no tack)
× (with tack)

(Heat resistance of coating film)
A sample piece having a 30 μm thick UV-cured coating film formed by a spin coater was heated at 125° C. for 8 hours, and the presence or absence of cracks on the coating surface was then visually inspected.
UV irradiation intensity: 180 mJ/ ^cm3
○ (no cracks)
△ (slight cracks)
× (with cracks)

(Refractive Index)
The solution was applied to a glass substrate to a thickness of 1 μm using a spin coater and cured at a UV irradiation intensity of 180 mJ/cm ³ to prepare a coating film, which was measured using a reflection spectroscopic film thickness meter.

(Synthesis Example 1)
Phenyltrimethoxysilane 86.25g
Methacryloxypropyltrimethoxysilane 59.73g
21.95g water
Phosphoric acid 0.85g
The mixture was stirred under reflux for 35 minutes.
Then, 10.07 g of tetraethoxysilane
Dimethyldimethoxysilane 29.05g
The mixture was then refluxed and stirred for an additional 15 minutes, and the pressure was reduced with a diaphragm pump and the temperature was raised to 70°C.
Then, 105.39 g of ethyl vinyl ether
was added dropwise over 10 minutes, and the mixture was stirred at room temperature for 12 hours.
The mixture was then stirred at 80° C. for 20 minutes under reduced pressure to remove the solvent, yielding a solvent-free siloxane (where a=1.2 in formula (1)).

(Synthesis Example 2)
A solvent-free siloxane (wherein a = 1.25 in formula (1)) was obtained in the same manner as in Synthesis Example 1, except that 5.03 g of tetraethoxysilane and 31.95 g of dimethyldimethoxysilane were used.

(Synthesis Example 3)
A solvent-free siloxane (a=1.2 in formula (1)) was obtained in the same manner as in Synthesis Example 1, except that ethyl vinyl ether was not used and acetal protection was not performed.

(Synthesis Example 4)
A solvent-free siloxane (a=1.2 in formula (1)) was obtained in the same manner as in Synthesis Example 1, except that 77.56 g of methyltriethoxysilane was used instead of phenyltrimethoxysilane.

Example 1
0.175 g of the siloxane obtained in Synthesis Example 1,
Pentaerythritol tetrakis(3-mercaptobutyrate) 0.1g
Isobornyl acrylate 0.68g
Phenylphosphine oxide (Omnirad 819 (manufactured by IGM Resins B.V., photopolymerization initiator)) 0.059 g
2.86 g of a methyl ethyl ketone dispersion of zirconium oxide having an average particle size of 11 nm (zirconium oxide content: 70% by weight) (zirconia particles were blended so that the refractive index was 1.7) was mixed and stirred at 50° C. for 1 hour under reduced pressure conditions, and the methyl ethyl ketone of the dispersion was distilled off to obtain an active energy ray-curable composition.

Example 2
An active energy ray-curable composition was obtained in the same manner as in Example 1, except that the siloxane obtained in Synthesis Example 1 was replaced with the siloxane obtained in Synthesis Example 2.

Example 3
An active energy ray-curable composition was obtained in the same manner as in Example 1, except that pentaerythritol tetrakis(3-mercaptobutyrate) was not used.

(Comparative Example 1)
An active energy ray-curable composition was obtained in the same manner as in Example 1, except that the siloxane obtained in Synthesis Example 1 was replaced with the siloxane obtained in Synthesis Example 3. The siloxane used in this example was not acetal-protected.

(Comparative Example 2)
An active energy ray-curable composition was obtained in the same manner as in Example 1, except that the siloxane obtained in Synthesis Example 1 was replaced with the siloxane obtained in Synthesis Example 4.

According to the present invention, a coating film having a high refractive index and excellent heat resistance can be obtained by using a hydrolysis condensation product of acetal-protected alkoxysilanes.
In contrast, in Comparative Example 1, in which a hydrolysis condensate of alkoxysilanes not protected by acetal was used, the viscosity became too high, making it impossible to perform proper coating film evaluation, and cracks occurred.In Comparative Example 2, in which highly reactive methyltriethoxysilane was used, a coating film with poor coating film heat resistance was obtained, and cracks occurred.

Claims (3)

An active energy ray-curable composition comprising the following (A) and (B), and substantially free of a solvent:
(A) Zirconium oxide fine particles; (B) Polysiloxane obtained by protecting silanol groups of a hydrolysis condensation product of alkoxysilanes with acetal. The active energy ray-curable composition according to claim 1, which contains (C) a photopolymerizable monomer. The active energy ray-curable composition according to claim 1 or 2, which contains (D) a multifunctional thiol compound.