JP2006291148A - Urethane (meth)acrylate-based compound and active energy ray-curable resin composition using the same, and coating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a urethane (meth)acrylate-based compound which is useful to provide a coating layer with a high refractive index, and excellent adhesiveness to a base material and surface hardness: an active energy ray-curable resin composition using the same; and a coating agent containing the same. <P>SOLUTION: The urethane (meth)acrylate-based compound is represented by formula (1), wherein R<SB>1</SB>is hydrogen or methyl, a and b may be same or different and are an integer of 1-3, R<SB>2</SB>is a hydrocarbon group having a carbon number of 1-6, R<SB>3</SB>is a hydrocarbon group having a carbon number of 1-3, X is Cl, Br, or I, and c and d may be same or different and are 0 or an integer of 1-4. The active energy ray-curable resin composition uses the same. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a novel urethane (meth) acrylate compound, and more specifically, urethane (meth) useful for forming a coating layer having a high refractive index and excellent surface hardness and substrate adhesion. The present invention relates to an acrylate compound, an active energy ray-curable resin composition containing the same, and a coating agent comprising the active energy ray-curable resin composition.

With the progress of the optical industry such as displays and optical communications, there is a demand for transparent resins with excellent optical performance, and among them, the demand for coating materials is increasing.
In recent years, in the optical field, the demand for optical components with a low-reflection coating has increased, and examples include lenses used for display substrates, optical films, and glasses. In these optical components, it is important to improve the light transmittance. In particular, in display applications, it is important to reduce the reflectance even by 0.1% in order to improve luminance and reduce power consumption. .

As a technique for reducing the reflection, a technique is used in which a low refractive index layer is provided on the surface of the base material and the interface reflectance when light enters from the air layer is reduced. As a base material, a glass having a refractive index of about 1.50 is often used in the case of a display, and in the case of a spectacle lens, a plastic having a refractive index of about 1.75 has been adopted in recent years. As the low refractive index layer, a technique of providing a low refractive index coating layer on the surface of a base material using magnesium fluoride or fluororesin having a refractive index of about 1.40 is common.
For example, in the case of a spectacle lens, the refractive index of a plastic lens is improved to about 1.75, and when there is no low refractive index coating layer, the reflectance of the surface of the lens substrate is only one side according to Fresnel's law. There are 7%. In addition, the reflectance mentioned here is a reflectance when natural light is obtained perpendicularly to the coating layer from the air layer. When a low refractive index coating layer having a refractive index of 1.40 is provided on a substrate having a refractive index of 1.75, this reflectance is reduced to 4%.

Furthermore, as a technique for reducing the reflectance, a technique of providing a high refractive index coating layer between the base material and the low refractive index coating layer is effective, and the base material (refractive index 1.75) / high refractive index is effective. In the layer configuration of coating layer (refractive index 1.57) / low refractive index coating layer (refractive index 1.40), the reflectance can be reduced to 3%. In such a case, the problem is the adhesion between the substrate of the high refractive index coating layer and the low refractive index coating layer, and the high refractive index having adhesion to both the lens substrate and the low refractive index coating layer. A coating layer is required. The refractive index of the high refractive index coating layer is not necessarily high, and the optimum value is determined from the refractive index of the substrate and the refractive index of the low refractive index coating layer.

Taking an optical film for display as an example, a polyethylene terephthalate (PET) film having a refractive index of 1.65 is widely used as a base material, but when there is no low refractive index coating layer, Since the reflectance is as high as 6.0% on only one side, the surface of the PET film is often treated with an acrylic hard coat agent having a refractive index of about 1.50. 2%.
However, the reflectance is 4.1 by adopting a layer configuration of PET base material (refractive index 1.65) / high refractive index coating layer (refractive index 1.57) / hard coating layer (refractive index 1.50). % Can be reduced. Also in this case, the problem is the adhesion of the high refractive index coating layer, and in particular, a high refractive index coating layer having excellent adhesion to the PET film is required.

Furthermore, taking an electrode substrate used for a display such as a touch panel or a liquid crystal as an example, a transparent conductive film such as ITO (refractive index 2.0) is formed on the surface of a transparent substrate such as glass (refractive index 1.5). Although formed, the reflectance on the ITO surface side reaches 8.7%. In the case of such an electrode substrate, it is impossible to cover the transparent conductive film. Therefore, a method of inserting a high refractive index coating layer between glass and ITO is effective, but in this case, the problem is high. The high refractive index coating layer is required because of the adhesiveness of the refractive index coating layer, and in particular, the adhesiveness with glass.

As a resin composition for forming a coating layer having such a high refractive index, various materials that can be cured with an active energy ray such as ultraviolet rays have been studied. In particular, it can cope with diversification of optical functions and improvement of productivity. Therefore, a material having both a high refractive index and a fast curing property is desired. For example, a (meth) acrylate compound in which an aromatic ring or a sulfur atom is introduced into a molecular structure (see, for example, Patent Document 1). ) And urethane (meth) acrylates that have urethane bonds in the molecular structure and that contain specific structures, and specific monofunctional (meth) acrylates and photopolymerization A photocurable resin composition comprising an initiator (see, for example, Patent Document 2) has been proposed.
JP 61-072748 A JP 2002-105149 A

However, since the disclosed technology of Patent Document 1 does not have a unit for improving adhesion such as a urethane group or a carboxylic acid group in the molecular structure, it has poor adhesion to a substrate when used as a coating agent. It was. Moreover, since the refractive index is about 1.55 in the technique disclosed in Patent Document 2, it has not been able to answer the recent demand for higher refractive index. Furthermore, since the polyalkylene glycol chain is included in the molecular structure, this soft segment reduces the surface hardness.
In addition, the refractive index in this invention is a value measured at 23 degreeC using a NaD line | wire.

Therefore, in the present invention, under such a background, a urethane (meth) acrylate compound useful for forming a coating layer having a high refractive index and having excellent adhesion to the substrate and surface hardness, and An object of the present invention is to provide an active energy ray-curable composition using the same, and a coating agent comprising such an active energy ray-curable resin composition.

  However, as a result of intensive studies by the present inventors, it was found that the urethane (meth) acrylate compound (A) represented by the following general formula (1) meets the above purpose, and the present invention was completed.

（ここで、Ｒ₁は水素又はメチル基、aとｂは同じでも異なってもよい１〜３の整数、R₂は炭素数１〜６の炭化水素基、R₃は炭素数１〜３の炭化水素基、ＸはＣｌ、Ｂｒ、又はＩ、ｃとｄは同じでも異なってもよい０もしくは１〜４の整数である。）

(Where R ₁ is hydrogen or a methyl group, a and b may be the same or different integers 1 to 3, R ₂ is a hydrocarbon group having 1 to 6 carbon atoms, and R ₃ is a carbon group having 1 to ₃ carbon atoms. (Hydrocarbon group, X is Cl, Br, or I, c and d are the same or different and may be 0 or an integer of 1 to 4.)

  In the present invention, a urethane (meth) acrylate compound in which a and b in the above formula (1) are both 3 is more preferable from the viewpoint of fast curability.

Moreover, this invention relates also to the active energy ray hardening-type composition formed by containing said urethane (meth) acrylate type compound (A) and a photoinitiator (B).
In the present invention, the active energy ray-curable resin composition having a refractive index of a cured product of 1.56 to 1.60 and an Abbe number of 30 to 50 is preferable from the viewpoint of optical design. An active energy ray-curable composition containing a mercaptan compound (C) represented by the following general formula (2) is preferable from the viewpoint of increasing the refractive index, and further, an ethylenically unsaturated monomer (D). It is preferable from the viewpoint that the refractive index can be easily adjusted.

（ここで、Ｒ₄は炭素数１〜６のアルキル基、eは１〜４の整数である。）
また、本発明では、上記の活性エネルギー線硬化型組成物よりなるコーティング剤に関するものである。

(Here, R ₄ is an alkyl group having 1 to 6 carbon atoms, and e is an integer of 1 to 4.)
Moreover, in this invention, it is related with the coating agent which consists of said active energy ray hardening-type composition.

  Since the urethane (meth) acrylate compound (A) of the present invention has a structure represented by the general formula (1), the cured coating film obtained from the urethane (meth) acrylate compound has a high refractive index. And has excellent effects on adhesion to the substrate and surface hardness.

Hereinafter, the present invention will be described in detail.
The urethane (meth) acrylate compound (A) of the present invention has an aromatic ring, a sulfur atom, and, if necessary, a chlorine atom or a bromine atom in the molecular structure. The refractive index of the coating layer after polymerization is improved.

In the present invention, the refractive index of such a coating layer is important. In view of the recent demand for higher refractive index, the refractive index of the coating layer is preferably 1.56 or more, more preferably 1.56 to 1.60. If the refractive index is less than 1.56, the effect of reducing reflection is poor, which is not preferable.

When an active energy ray-curable resin composition obtained by using a urethane (meth) acrylate compound is used as an optical resin, it is important to pay attention to the Abbe number together with the refractive index. The Abbe number is a numerical value indicating the wavelength dependence of the refractive index, and the chromatic dispersion increases when the Abbe number is small. Normally, the refractive index and the Abbe number are contradictory, but a coating layer having a high refractive index and a high Abbe number is desired from the viewpoint of optical design. The Abbe number of the coating layer is preferably 30 or more, more preferably 30 to 50. An Abbe number of less than 30 is not preferable because of poor visibility.

Moreover, since the urethane (meth) acrylate compound (A) of the present invention has (meth) acryloyl groups at both ends of the molecular structure, it is rapidly cured by active energy rays such as ultraviolet rays and has a highly crosslinked structure. A coating layer is formed. This fast curability is important in coating applications and needs to be sufficiently cured with a small amount of light. Amount of light necessary for curing, for example, when performing curing by ultraviolet rays, preferably 2000 mJ / cm ² or less, 1000 mJ / cm ² or less being more preferred. In order to achieve the desired high refractive index and high surface hardness, it is necessary to improve the reaction rate of the (meth) acryloyl group, and the preferable range of the reaction rate is 60% or more, more preferably 70. % Or more, more preferably 80% or more. If the reaction rate is less than 60%, not only the refractive index will not be sufficiently high but also the surface hardness will be insufficient.

Furthermore, it is important that the urethane (meth) acrylate compound (A) of the present invention has a (meth) acryloyl group at both ends of the molecular structure, and has a (meth) acryloyl group in the side chain instead of the end. That is, when the number of side chain atomic groups that do not contribute to the structure between crosslinks increases, heat resistance and surface hardness decrease. The number of terminal (meth) acryloyl groups is not particularly limited, but is preferably 2 to 6, more preferably 4 to 6, still more preferably 6, particularly preferably 3 at one end of the molecular structure, and the other. There are three at the end of the total of six. An acryloyl group and a methacryloyl group may be mixed in one molecule.

Faster curability is achieved as the number of (meth) acryloyl groups at both ends increases, but the atomic group refractive index of the (meth) acryloyl group is about 1.5, and the (meth) acryloyl group has a molecular structure. Excessive introduction leads to a decrease in the refractive index of the coating layer, which is not preferable. Further, when the number of (meth) acryloyl groups increases excessively, curing shrinkage increases, and distortion is likely to occur in the coating layer.

Furthermore, since the urethane (meth) acrylate compound (A) of the present invention has a urethane bond in the molecular structure, the formed coating layer has high adhesion to substrates such as glass and plastic films. And having a high surface hardness due to hydrogen bonding. The two urethane bonds in the molecular structure must be introduced into the molecular chain via appropriate atomic groups. If the urethane bonds are excessively dense, the resulting polymer becomes brittle and the coating layer is prone to cracks. It is not preferable. The urethane bond is preferably introduced into the molecular chain via an asymmetric atomic group such as m-xylylene. For example, a symmetrical atomic group such as p-xylylene is not preferable because the urethane (meth) acrylate compound (A) is easily crystallized, and is inferior in solubility when used as a liquid coating agent.

In addition, it is necessary to introduce the aromatic ring into the molecular chain through an appropriate atomic group. When the aromatic ring is dense, the urethane (meth) acrylate compound (A) is easily crystallized and used as a liquid coating agent. This is not preferable because it is inferior in terms of solubility.
The urethane (meth) acrylate compound (A) of the present invention is molecularly designed based on the reasons described above.

Hereinafter, the production method of the urethane (meth) acrylate compound (A) of the present invention will be described. However, the present invention is not limited to these production methods, and the production method of the general formula (1) is not limited to these production methods. The thing of the structure shown should just be manufactured.
The urethane (meth) acrylate compound (A) of the present invention is produced by carrying out the following production steps [1] and [2] and, if necessary, the production step [3].

（ここで、R₃は炭素数１〜３の炭化水素基、ＸはＣｌ、Ｂｒ、又はＩ、ｃとｄは同じでも異なってもよい０もしくは１〜４の整数である。）
製造工程［２］：製造工程［１］で得られた両末端イソシアネート基含有化合物に水酸基含有（メタ）アクリレート系化合物を反応させる工程。
製造工程［３］：洗浄工程。 Production process [1]: A process in which a diol compound represented by the following general formula (3) is reacted with m-xylylene diisocyanate under specific conditions.

(Here, R ₃ is a hydrocarbon group having 1 to ₃ carbon atoms, X is Cl, Br, or I, and c and d are 0 or an integer of 1 to 4 which may be the same or different.)
Production step [2]: A step of reacting a hydroxyl group-containing (meth) acrylate compound with the both-end isocyanate group-containing compound obtained in the production step [1].
Manufacturing process [3]: Cleaning process.

First, the manufacturing process [1] will be described.
Examples of the compound represented by the above formula (3) include 4,4′-bis [β-hydroxyethylthio] diphenylsulfone, 4,4′-bis [β-hydroxypropylthio] diphenylsulfone, and 4,4 ′. -Bis [β-hydroxyethylthio] -3,3 ', 5,5'-tetrachlorodiphenylsulfone, 4,4'-bis [β-hydroxyethylthio] -3,3', 5,5'-tetra Examples include bromodiphenyl sulfone.
In the present invention, in order to produce the urethane (meth) acrylate-based compound (A) of the general formula (1), it is necessary to obtain a compound containing both terminal isocyanate groups of n = 1 in the following general formula (4) with high yield. There is.

When an oligomer having n of 2 or more is present, the purity of the urethane (meth) acrylate compound (A) represented by the general formula (1) obtained in the production steps [2] and [3] is lowered. The refractive index accuracy of the coating layer is poor. The content of the compound containing isocyanate groups at both ends with n = 1 is preferably 30% by weight or more, particularly 50% by weight or more, and more preferably 70% by weight or more with respect to the total reaction product. preferable.
In order to obtain an isocyanate group-containing compound with n = 1 at a high yield, it is preferable to carry out the production under the following reaction conditions.

As a reaction ratio of the diol compound represented by the above formula (3) and m-xylylene diisocyanate, m-xylylene diisocyanate is 2.0 to 2.1 mol with respect to 1.0 mol of the diol compound. preferable. If the amount is less than 2.0 mol, the hydroxyl-terminated compound remains in the reaction system after the reaction, and the desired urethane (meth) acrylate compound (A) cannot be obtained in good yield. On the other hand, when the amount exceeds 2.1 mol, a large amount of m-xylylene diisocyanate as a raw material remains in the reaction system after the reaction, so that the desired urethane (meth) acrylate compound (A) cannot be obtained in good yield. .

In the present invention, a reaction method in which the diol compound represented by the above formula (3) is dissolved in an organic solvent and this solution is dropped into m-xylylene diisocyanate is preferable. The organic solvent to be used is not particularly limited, but tetrahydrohyran (THF) is particularly preferable. The concentration of the diol compound in the solution is preferably 1 to 500 parts by weight / L, more preferably 10 to 300 parts by weight / L, still more preferably 100 to 200 parts by weight / L, and less than 1 part by weight / L. Productivity is inferior, and if it exceeds 500 parts by weight / L, it is not preferred because a compound containing both terminal isocyanate groups having n of 2 or more in general formula (4) tends to be produced.

Moreover, in order to obtain a compound having an isocyanate group containing both terminals with n = 1 efficiently, it is preferable to slow the dropping rate. The preferable range of the dropping rate is 1 to 200 mol / hour, more preferably 2 to 100 mol / hour, still more preferably 20 to 100 mol / hour, when the weight of all diol compounds is 100 mol. If it is less than / hour, the productivity is inferior, and if it exceeds 200 mol / hour, the number of oligomers increases, which is not preferable.

In the present invention, it is preferable to use a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo [5.4.0] undecene-7 for the purpose of promoting the reaction. The addition amount of the catalyst is not particularly limited, but is preferably 0.001 part by weight or more, more preferably 0.001 to 0.1 part by weight, particularly preferably 0.02 to 0 part per 100 parts by weight of the diol compound. .1 part by weight. Less than 0.001 part by weight is not preferable because the oligomer increases.
The reaction temperature is preferably 40 to 80 ° C., particularly preferably 50 to 70 ° C., more preferably 55 to 65 ° C. When the temperature is lower than 40 ° C., the productivity is inferior. It is not preferable because n-terminated two-terminal isocyanate group-containing compounds tend to be formed and m-xylylene diisocyanate tends to react with each other.
The reaction is preferably performed under an inert gas in order to improve the hue of the product.

Next, the manufacturing process [2] will be described.
The hydroxyl group-containing (meth) acrylate-based compound is reacted with the both-end isocyanate group-containing compound obtained in the production step [1].
The hydroxyl group-containing (meth) acrylate compound used in the present invention is not particularly limited as long as it is an acrylic acid partial ester of a polyhydric alcohol. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) ) Acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol di (meth) acrylate, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate, pentaerythritol tri ( And (meth) acrylate. Among these, pentaerythritol tri (meth) acrylate having 3 (meth) acryloyl groups is preferable in terms of fast curability.

About the usage-amount of a hydroxyl-containing (meth) acrylate type compound, the quantity of the isocyanate group in reaction system is measured by methods, such as titration, and a hydroxyl-containing (meta) is used so that it may become the quantity of a hydroxyl group equivalent to the quantity of this isocyanate group. ) Use acrylate compounds.
Examples of the titration method include a method in which di-n-butylamine is added to the reaction for reaction, and the remaining di-n-butylamine is back titrated with hydrochloric acid. The end point of the reaction can also be judged by confirming the amount of isocyanate groups in the reaction solution.
For the purpose of promoting the reaction, it is preferable to use a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo [5.4.0] undecene-7. The addition amount of the catalyst is preferably 0.001 to 0.1 parts by weight. The reaction temperature is preferably from 30 to 90 ° C, particularly preferably from 40 to 80 ° C.

Furthermore, the manufacturing process [3] will be described.
The obtained urethane (meth) acrylate compound (A) is preferably washed for purification. The purification referred to here is performed in order to remove a small amount of remaining monomers such as m-xylylene diisocyanate and by-product oligomers, and is a urethane (meth) acrylate compound represented by the general formula (1) ( The purpose is to improve the purity of A). The washing method is preferably carried out in two stages, a first stage (removal of residual monomers) and a second stage (removal of oligomers). The order of the first stage and the second stage can be switched.

In the first stage, the poor solvent of the urethane (meth) acrylate compound (A) represented by the general formula (1) is introduced into the reaction system, and the residual monomer transferred to the poor solvent layer is removed. As the poor solvent, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and a mixed solvent thereof are preferable.
In the second stage, a good solvent of the urethane (meth) acrylate compound (A) represented by the general formula (1) is introduced into the reaction system, and the target compound transferred to the good solvent layer is extracted. As the good solvent, toluene, xylene, and a mixed solvent thereof are preferable.
Thus, the urethane (meth) acrylate compound (A) represented by the general formula (1) of the present invention is obtained.

Next, the active energy ray-curable resin composition using the urethane (meth) acrylate compound (A) of the present invention will be described.
In the present invention, a coating layer having a high refractive index is formed by containing the urethane (meth) acrylate compound (A) represented by the general formula (1) and the photopolymerization initiator (B). The active energy ray-curable composition is suitable as a coating agent.

The photopolymerization initiator (B) is not particularly limited as long as it generates radicals by the action of light, and examples thereof include 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 2 -Hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylenephenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2- Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio ) Phenyl] -2-morpholinopropane-1, benzoin, benzoin methyl ether, benzene Inethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyldimethyl ketal, benzophenone, benzoylbenzoic acid, benzoylmethyl benzoate, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3 ' -Dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 4 ′, 4 ″ -diethylisophthalophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, α-acyloxime ester, acylphos Examples include fin oxide, methylphenylglyoxylate, benzyl, 9,10-phenanthrenequinone, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, among which benzyldimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one are preferred. Used for.

The content of the photopolymerization initiator (B) is preferably 0.1 to 10 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of the urethane (meth) acrylate compound (A). Particularly preferred is 2 to 5 parts by weight. If the blending amount is less than 0.1 parts by weight, the curing rate is slow, and if it exceeds 10 parts by weight, the hue of the coating layer is deteriorated.
Further, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethylamino as an auxiliary for the photopolymerization initiator Ethyl benzoate, ethyl 4-dimethylaminobenzoate (n-butoxy), isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthio It is also possible to use xanthone or the like together.

In the present invention, it is preferable to contain a mercaptan compound (C) as a chain transfer agent in addition to the photopolymerization initiator (B). In particular, as the mercaptan compound (C), a plurality of thiol groups are included in the molecular structure. It is preferable that it is a compound (C) which has. By using a compound having a plurality of thiol groups, it is possible to maintain a high refractive index, surface hardness, and heat resistance without reducing the crosslinking density of the resulting polymer.

Examples of mercaptan compounds (C) having a plurality of thiol groups include benzenedithiol, xylylenedithiol, hexanedithiol, tolylenetrithiol, pentaerythritol tetrakis (β-thiopropionate), pentaerythritol tetrakis (thioglycolate). ), Trimethylolpropane tris (β-thiopropionate), trimethylolpropane tris (thioglycolate), diethylene glycol bis (β-thiopropionate), diethylene glycol bis (thioglycolate), triethylene glycol bis (β -Thiopropionate), triethylene glycol bis (thioglycolate), dipentaerythritol hexakis (β-thiopropionate), dipentaerythritol hexakis (thioglyco) Rate), tris [2- (β-thiopropionyloxy) ethyl] triisocyanurate, tris (2-thioglyconyloxyethyl) triisocyanurate, tris [2- (β-thiopropionyloxyethoxy) ethyl] triisocyanate Nurate, tris (2-thioglyconyloxyethoxyethyl) triisocyanurate, tris [3- (β-thiopropionyloxy) propyl] triisocyanurate, tris (3-thioglyconyloxypropyl) triisocyanurate, and the like. It is done.

Moreover, it is more preferable that a mercaptan compound (C) contains an aromatic ring in molecular structure at the point of high refractive index. Furthermore, it is preferable that the thiol group and the aromatic ring are bonded via an alkylene spacer from the viewpoint of increasing the Abbe number (low color dispersion). When the thiol group and the aromatic ring are directly bonded, the Abbe number is significantly decreased, which is not preferable.
In the present invention, the mercaptan compound (C1) represented by the following general formula (2) is particularly preferable as the mercaptan compound (C).

（ここで、Ｒ₄は炭素数１〜６のアルキル基、eは１〜４の整数である。）

(Here, R ₄ is an alkyl group having 1 to 6 carbon atoms, and e is an integer of 1 to 4.)

In this invention, it is preferable that content of the said mercaptan compound (C) is 0.01-20 weight part with respect to 100 weight part of urethane (meth) acrylate type compounds (A), especially 0.1. It is preferably -15 parts by weight, more preferably 1-10 parts by weight. If the content is less than 0.01 parts by weight, the effect of increasing the refractive index is poor, and if it exceeds 20 parts by weight, the surface hardness is undesirably lowered.

In the present invention, in addition to the urethane (meth) acrylate compound (A), the photopolymerization initiator (B), and the mercaptan compound (C), it may further contain an ethylenically unsaturated monomer (D). Although it is preferable at the point which adjusts a refractive index easily, about this content, it is not specifically limited, 50 weight part or less with respect to 100 weight part of urethane (meth) acrylate type compounds (A), Especially 10-40 weight part, Furthermore, Is preferably 20 to 30 parts by weight. If the content exceeds 50 parts by weight, the refractive index tends to decrease or the adhesiveness tends to decrease, such being undesirable.
The ethylenically unsaturated monomer (D) may be any monomer having one or more ethylenically unsaturated groups in one molecule, and examples thereof include monofunctional monomers, bifunctional monomers, and trifunctional or more monomers.

Examples of the monofunctional monomer include styrene, vinyl toluene, chlorostyrene, α-methyl styrene, methyl (meth) acrylate, ethyl (meth) acrylate, acrylonitrile, vinyl acetate, 2-hydroxyethyl (meth) acrylate, and 2-hydroxy. Propyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-phenoxy-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3- Chloro-2-hydroxypropyl (meth) acrylate, glycerin mono (meth) acrylate, glycidyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isoborni (Meth) acrylate, tricyclodecanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, n-butyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl ( (Meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate, n-stearyl (meth) acrylate, phenyl methacrylate, benzyl (meth) acrylate, phenol ethylene oxide modified (n = 2) (meta ) Acrylate, nonylphenol propylene oxide modified (n = 2.5) (meth) acrylate, 2- (meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxy-2- Half (meth) acrylate, furfuryl (meth) acrylate, carbitol (meth) acrylate, benzyl (meth) acrylate, butoxyethyl (meth) acrylate, allyl (meth) acrylate, acryloylmorpholine of phthalic acid derivatives such as hydroxypropyl phthalate , 2-hydroxyethylacrylamide, N-methylol (meth) acrylamide, N-vinylpyrrolidone, 2-vinylpyridine, 2-acryloyloxyethyl acid phosphate monoester, and the like.

Examples of the bifunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and dipropylene. Glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide modified bisphenol A type di (meth) acrylate, propylene oxide modified bisphenol A type Di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythrito Rudi (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, diglycidyl phthalate di (meth) acrylate, hydroxypivalic acid modified neopentyl glycol di (meth) acrylate , Isocyanuric acid ethylene oxide modified diacrylate, 2-acryloyloxyethyl acid phosphate diester, p-bis [β- (meth) acryloyloxyethylthio] xylylene, 4,4′-bis [β- (meth) acryloyloxyethylthio ] Diphenyl sulfone etc. are mentioned.

Examples of the tri- or higher functional monomer include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth). ) Acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified triacrylate, ethylene oxide modified dipentaerythritol penta (meth) acrylate, ethylene oxide modified dipentaerythritol Hexa (meth) acrylate, ethylene oxide modified pentaerythritol tri (meth) acrylate, Chi alkylene oxide modified pentaerythritol tetra (meth) acrylate.

Other examples include a Michael adduct of acrylic acid or a 2-acryloyloxyethyl dicarboxylic acid monoester. Examples of the acrylic acid Michael adduct include acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, A methacrylic acid tetramer etc. are mentioned. The 2-acryloyloxyethyl dicarboxylic acid monoester is a carboxylic acid having a specific substituent, for example, 2-acryloyloxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxy Examples thereof include ethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxyethyl hexahydrophthalic acid monoester, 2-methacryloyloxyethyl hexahydrophthalic acid monoester, and the like. Furthermore, other oligoester acrylates can also be mentioned.
These ethylenically unsaturated monomers (D) may be used alone or in combination of two or more.

Thus, the active energy ray-curable type of the present invention comprising the urethane (meth) acrylate compound (A) and the photopolymerization initiator (B), preferably further containing a mercaptan compound (C) and an ethylenically unsaturated monomer (D). Resin composition can be obtained, but as required, silane coupling agent, antioxidant, polymerization inhibitor, yellowing inhibitor, ultraviolet absorber, filler, dye / pigment, oil, plasticizer, wax, dry Various additives such as additives, dispersants, wetting agents, emulsifiers, gelling agents, stabilizers, antifoaming agents, leveling agents, thixotropic agents, flame retardants, fillers, reinforcing agents, matting agents, and crosslinking agents. It can also be contained.

The active energy ray-curable composition of the present invention is preferably used as a coating agent for forming a coating layer having high refraction, high surface hardness, and high heat resistance. Although it does not specifically limit in coating on a base material, For example, well-known methods, such as a bar coat, a spin coat, a dip coat, and a gravure coat, are used.

When adjusting the coating agent for thin films, it is also preferable to dilute such an active energy ray-curable resin composition with a solvent, if necessary. Examples of such a solvent include known organic solvents such as ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, acetone, toluene, xylene, cyclohexanone, cellosolves, diacetone alcohol, propylene glycol monomethyl ether acetate and the like. The composition amount of the solvent is such that the composition concentration is 1 to 50% by weight, preferably 3 to 30% by weight or less, more preferably 4 to 20% by weight or less, and further preferably 5 to 15% by weight. If it exceeds 50% by weight, the coating property is inferior because of high viscosity, and if it is less than 1% by weight, the drying load increases, which is not preferable.

The coating agent comprising the active energy ray-curable resin composition of the present invention is cured by irradiating active energy rays after coating the substrate and drying the solvent as necessary.
Such a substrate is not particularly limited. For example, polyolefin resin such as polyethylene, polypropylene, polycyclopentadiene, polycarbonate, polyester, ABS resin, acrylic resin and the like (film, sheet, cup, etc.) ), Metal, glass and the like.

As such active energy rays, rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X rays and γ rays, electron beams, proton rays, neutron rays, etc. can be used. Curing by ultraviolet irradiation is advantageous from the viewpoint of easy availability and price. In addition, when performing electron beam irradiation, it can harden | cure even if it does not use a photoinitiator.
As a method of curing by ultraviolet irradiation, about 100 to 2000 mJ / cm ² using a high pressure mercury lamp, ultrahigh pressure mercury lamp, carbon arc lamp, metal halide lamp, xenon lamp, chemical lamp, etc. that emits light in the wavelength range of 150 to 450 nm. It is sufficient to irradiate the ultraviolet rays. After the ultraviolet irradiation, heating can be performed as necessary to complete the curing.

Thus, the active energy ray-curable resin composition using the urethane (meth) acrylate compound (A) and the urethane (meth) acrylate compound (A) of the present invention has a high refractive index and has a surface. A coating layer with excellent hardness, substrate adhesion, and light transmittance can be formed. Various coatings such as paints, adhesives, adhesives, inks, protective coating agents, anchor coating agents, and coating binders can be formed. Useful as a material. Among them, it is very useful as a coating agent for display optical films, lenses, memory disks and the like.

Hereinafter, the present invention will be described more specifically with reference to examples.
In the examples, “%” and “parts” are based on weight unless otherwise specified.

Example 1
[Synthesis of Urethane (meth) acrylate Compound (A-1)]
A four-necked flask equipped with a dropping funnel, thermometer, stirrer, water-cooled condenser and nitrogen gas blowing port was charged with 69.0 g (0.37 mol) of m-xylene diisocyanate and 0.02 g of dibutyltin dilaurate, while dropping. The funnel was charged with a uniform solution of 67.9 g (0.18 mol) of 4,4′-bis [β-hydroxyethylthio] diphenylsulfone and 700 g of tetrahydrofuran. After the temperature in the flask was raised to 60 ° C., the reaction was carried out by dropping the solution at 380 g / hour from the dropping funnel, and the reaction was terminated when the residual isocyanate group reached 1.8%. Subsequently, 163.2 g (0.37 mol) of pentaerythritol triacrylate (“Kyoeisha Chemical Industry Co., Ltd.“ Light acrylate PE-3A ”) and 0.4 g of hydroquinone methyl ether were added to the reaction system at 50 ° C., and then at 60 ° C. The reaction was terminated for 5 hours, and the reaction was terminated when the residual isocyanate group reached 0.1%. After the reaction liquid was concentrated, 500 g of methyl isobutyl ketone was added for washing, and the washing liquid was discarded. Subsequently, 500 g of toluene was added and stirred for 1 hour, followed by filtration using activated clay. Thereafter, the solvent was distilled off to obtain a urethane (meth) acrylate compound (A-1).

The chart of ¹³ C-NMR (reference substance: tetramethylsilane, solvent: CDCl ₃ ) of the obtained urethane (meth) acrylate compound (A-1) and its attribution are shown in FIG. 1, and ¹ H-NMR (reference substance) : Tetramethylsilane, solvent: CDCl ₃ ) and their attribution are shown in FIG. 2, and the infrared chart is shown in FIG.

The spectrum numbers on the ¹³ C-NMR chart correspond to the carbon numbers 1 to 22 described in the following structural formula, and the spectrum numbers on the ¹ H-NMR chart correspond to the numbers 1 to 22 described in the following structural formula. Corresponds to hydrogen bonded to carbon and hydrogen of urethane bond number 23. In the spectrum of the infrared chart, 1529 cm ⁻¹ and 1727 cm ⁻¹ are absorptions based on a urethane bond, and 809 cm ⁻¹ , 1409 cm ⁻¹ , 1617 cm ⁻¹ and 1634 cm ⁻¹ are absorptions based on an acryloyl group and 1158 cm. ^-1 and around 1300 cm ^-1 are absorptions based on sulfone groups.
NMR was measured using “UNITY 300” manufactured by VARIAN, and infrared was measured using “AVATAR 360” manufactured by NICOLET.

The structure of this urethane (meth) acrylate compound (A-1) is as follows.

[Preparation of active energy ray-curable resin composition]
To 100 parts of the urethane (meth) acrylate compound (A-1) obtained above, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (B-1) as a photopolymerization initiator (B) was added. ) (Ciba Specialty Chemicals, “Darocur 1173”) was added to obtain an active energy ray-curable resin composition.

[Formation of coating layer 1]
The active energy ray-curable resin composition was bar coated on a polyethylene terephthalate film having a thickness of 100 μm so as to have a film thickness of 10 μm (a part of the plate surface was masked with a tape for measuring the film thickness). ). After leveling for 10 minutes, using one high-pressure mercury lamp 80W, one lamp was irradiated with 1 pass of ultraviolet light (integrated irradiation amount 1000 mJ / cm ² ) at a conveyor speed of 1.6 m / min from a height of 13 cm, and cured. A coating layer was formed. The following evaluation was performed about the obtained coating layer. The evaluation results are shown in Table 2.

(Film thickness)
The masked tape was peeled off, and the film thickness (μm) of the step between the coated part and the non-coated part was measured using “Surfcom 1400D” manufactured by Keyence Corporation.
(Reaction rate)
The FT-IR of the coating layer was measured, and the reaction rate (%) was calculated from the peak area of 1635 cm ⁻¹ attributed to the double bond of the (meth) acryloyl group.
(Refractive index, Abbe number)
Using an “Abbe refractometer 1T” manufactured by Atago Co., Ltd., the value at 23 ° C. was measured with the NaD line.
(surface hardness)
The pencil hardness was measured according to JIS K 5600-5-4.
(Adhesion)
Perform a peel test according to JIS K 5600-5-6. The case where the coating layer was peeled off from the base material was indicated as x, and the case where the coating layer was not peeled off was indicated as ○.

[Formation of coating layer 2]
100 parts of the active energy ray-curable resin composition was dissolved in 900 parts of propylene glycol monomethyl ether acetate to prepare a coating agent having a composition concentration of 10% by weight. This coating agent was spin-coated on a glass plate having a thickness of 0.7 mm and a size of 100 × 100 mm so that the film thickness was 0.14 μm (a part of the plate surface was masked with a tape for measuring the film thickness). did). After drying at 100 ° C. for 10 minutes, using one high pressure mercury lamp 80W, one pass of UV irradiation (integrated irradiation amount 1000 mJ / cm ² ) at a conveyor speed of 1.6 m / min from a height of 13 cm. And a cured coating layer was formed. The following evaluation was performed about the obtained coating layer. The evaluation results are shown in Table 3.

(Film thickness)
The masked tape was peeled off, and the level difference between the coated part and the non-coated part was measured using “Surfcom 1400D” manufactured by Keyence Corporation.
(Adhesion)
In the visual inspection, the case where peeling was observed at the interface between the glass and the coating layer was rated as x, and the case where peeling was not observed was marked as ○.
(Total light transmittance)
On the obtained coating layer, 500 nm of ITO was formed by sputtering (220 ° C.). The total light transmittance of the obtained electrode substrate was measured according to JIS K 7105 using “SM Color Computer” manufactured by Suga Test Instruments Co., Ltd.

Example 2
[Synthesis of urethane (meth) acrylate compound (A-2)]
A four-necked flask equipped with a dropping funnel, thermometer, stirrer, water-cooled condenser, and nitrogen gas blowing port was charged with 115.3 g (0.61 mol) of m-xylene diisocyanate and 0.02 g of dibutyltin dilaurate, while dropping. A funnel was charged with a uniform solution of 113.5 g (0.31 mol) of 4,4′-bis [β-hydroxyethylthio] diphenylsulfone and 700 g of tetrahydrofuran. After raising the temperature in the flask to 60 ° C., the solution was dropped from the dropping funnel at a rate of 400 g / hour to carry out the reaction, and the reaction was terminated when the residual isocyanate group reached 2.8%. Subsequently, 71.2 g (0.61 mol) of 2-hydroxyethyl acrylate (“Kyoeisha Chemical Industry Co., Ltd.“ Light Ester HOA ”) and 0.4 g of hydroquinone methyl ether were added to the reaction system at 50 ° C., and 5 at 60 ° C. The reaction was terminated when the remaining isocyanate groups reached 0.1%. After the reaction solution was concentrated, 250 g of methyl isobutyl ketone was added for washing, and the washing solution was discarded. Subsequently, 250 g of toluene was added and stirred for 1 hour, followed by filtration using activated clay. Thereafter, the solvent was distilled off to obtain a urethane (meth) acrylate compound (A-2).

The chart of ¹³ C-NMR (reference substance: tetramethylsilane, solvent: CDCl ₃ ) of the obtained urethane (meth) acrylate compound (A-2) and its attribution are shown in FIG. 4, and ¹ H-NMR (reference substance) : Tetramethylsilane, solvent: CDCl ₃ ) and their attribution are shown in FIG. 5, and the infrared chart is shown in FIG.
The spectrum numbers on the ¹³ C-NMR chart correspond to the carbon numbers ¹ to 21 described in the following structural formula, and the spectrum numbers on the ¹ H-NMR chart correspond to the numbers 1 to 21 described in the following structural formula. Corresponds to hydrogen bonded to carbon and hydrogen of urethane bond number 22. In the infrared chart spectrum, 1529 cm ⁻¹ and 1721 cm ⁻¹ are absorptions based on urethane bonds, 810 cm ⁻¹ , 1409 cm ⁻¹ , 1610 cm ⁻¹ and 1637 cm ⁻¹ are absorptions based on acryloyl groups, and 1157 cm. ^-1 and around 1300 cm ^-1 are absorptions based on sulfone groups.
NMR was measured using “UNITY 300” manufactured by VARIAN, and infrared was measured using “AVATAR 360” manufactured by NICOLET.

The structure of this urethane (meth) acrylate compound (A-2) is as follows.

Using the obtained urethane (meth) acrylate compound (A-2), an active energy ray-curable resin composition was prepared in the same manner as in Example 1, and the coating layer was formed in the same manner as in Example 1. Formed. The evaluation results of the resulting coating layer are shown in Tables 2 and 3.

Example 3
In Example 1, the active energy ray-curable resin composition was obtained in the same manner as in Example 1 except that 10 parts of m-xylylenedithiol (C-1) was added as the mercaptan compound (C). Then, a coating layer was formed and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 2 and 3.

Example 4
70 parts of the urethane (meth) acrylate compound (A-1) obtained in Example 1, and 4,4′-bis [β-methacryloyloxyethylthio] diphenylsulfone (D-) as the ethylenically unsaturated monomer (D) 1) An active energy ray-curable resin composition was obtained in the same manner as in Example 1 except that 30 parts were used. Further, a coating layer was formed in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 2 and 3.

Example 5
70 parts of urethane (meth) acrylate compound (A-1) obtained in Example 1, 5 parts of m-xylylenedithiol (C-1) as mercaptan compound (C), and as ethylenically unsaturated monomer (D) An active energy ray-curable resin composition was obtained in the same manner as in Example 1 except that 20 parts of benzyl methacrylate (D-2) was used. Further, a coating layer was formed in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 2 and 3.

Example 6
In Example 1, an active energy ray-curable resin composition was obtained in the same manner as in Example 1 except that 2 parts of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., “KBM503”) was added. Then, a coating layer was formed and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 2 and 3.

Comparative Example 1
In Example 1, the same procedure was carried out except that the urethane (meth) acrylate compound (A-1) was changed to 4,4′-bis [β-methacryloyloxyethylthio] diphenylsulfone (D-1). An energy ray curable resin composition was obtained. Furthermore, tried to form a coating layer in the same manner as in Example 1, without curing the ultraviolet irradiation 1000 mJ / cm ^2, the surface was uncured at ultraviolet irradiation 2000 mJ / cm ^2.

Comparative Example 2
In Comparative Example 1, when ultraviolet irradiation was further repeated up to a light amount of 10 J, a coating layer was formed on the polyethylene terephthalate film. The evaluation results are shown in Table 2. However, the coating layer peeled off on the glass, and a test piece worthy of evaluation of light transmittance was not obtained.

Comparative Example 3
According to the description in Example 1 of Patent Document 2, a urethane (meth) acrylate-based composition is prepared. A reaction vessel equipped with a stirrer was charged with 29.6 g of 2,4-tolylene diisocyanate, 0.08 g of di-n-butyltin dilaurate and 0.02 g of 2,6-di-t-butyl-p-cresol, Cooled to 5-10 ° C. While stirring, 18.9 g of 2-hydroxy-3-phenyloxyprovir acrylate was added dropwise so that the temperature was maintained at 30 ° C. or lower. After completion of the dropwise addition, the mixture was reacted at 30 ° C. for 1 hour. Next, after 34.2 g of polytetramethylene glycol having a number average molecular weight of 402 was added and reacted at 50 ° C. for 1 hour, an ethylene oxide (m = n = 2.0) adduct of bisphenol A was subsequently added to 17. 2g was added and reaction was continued at 50-70 degreeC for 2 hours. The reaction was terminated when the residual isocyanate became 0.1% or less to obtain a urethane (meth) acrylate compound (A ′).
Using this urethane (meth) acrylate compound (A ′), an active energy ray-curable resin composition was prepared in the same manner as in Example 1, and a coating layer was formed in the same manner as in Example 1. The evaluation results of the obtained coating layer are shown in Tables 2 and 3.

REFERENCE EXAMPLE A 500 mm ITO film was formed on a glass plate having a thickness of 0.7 mm and a size of 100 × 100 mm by sputtering (220 ° C.). Table 3 shows the evaluation results of the obtained electrode substrate (electrode substrate having no high refractive index coating layer).

2 is a ¹³ C-NMR chart of a urethane (meth) acrylate compound (A-1) obtained in Example 1. FIG. 1 is a ¹ H-NMR chart of a urethane (meth) acrylate compound (A-1) obtained in Example 1. 2 is an infrared chart of the urethane (meth) acrylate compound (A-1) obtained in Example 1. FIG. 3 is a ¹³ C-NMR chart of a urethane (meth) acrylate compound (A-2) obtained in Example 2. FIG. 2 is a ¹ H-NMR chart of a urethane (meth) acrylate compound (A-2) obtained in Example 2. FIG. 2 is an infrared chart of the urethane (meth) acrylate compound (A-2) obtained in Example 2. FIG.

The active energy ray-curable resin composition comprising the urethane (meth) acrylate compound (A) and the urethane (meth) acrylate compound (A) according to the present invention has a high refractive index and surface hardness. Can form coating layers with excellent adhesion to substrates and light transmittance, and various film forming materials such as paints, adhesives, adhesives, inks, protective coating agents, anchor coating agents, coating binders, etc. Useful as. Among them, it is very useful as a coating agent for display optical films, lenses, memory disks and the like.

Claims (8)

A urethane (meth) acrylate compound represented by the following general formula (1).

... (1)
(Where R ₁ is hydrogen or a methyl group, a and b may be the same or different integers 1 to 3, R ₂ is a hydrocarbon group having 1 to 6 carbon atoms, and R ₃ is a carbon group having 1 to ₃ carbon atoms. (Hydrocarbon group, X is Cl, Br, or I, c and d are the same or different and may be 0 or an integer of 1 to 4.) The urethane (meth) acrylate compound according to claim 1, wherein a and b in the general formula (1) are both 3. An active energy ray-curable resin composition comprising the urethane (meth) acrylate compound (A) according to claim 1 or 2 and a photopolymerization initiator (B). The active energy ray-curable resin composition according to claim 3, wherein the cured product has a refractive index of 1.56 to 1.60 and an Abbe number of 30 to 50. The active energy ray-curable resin composition according to claim 3 or 4, further comprising a mercaptan compound (C). 6. The active energy ray-curable resin composition according to claim 5, wherein the mercaptan compound (C) is a mercaptan compound (C1) represented by the following general formula (2).

... (2)
(Here, R ₄ is an alkyl group having 1 to 6 carbon atoms, and e is an integer of 1 to 4.)   The active energy ray-curable resin composition according to claim 3, further comprising an ethylenically unsaturated monomer (D). A coating agent comprising the active energy ray-curable resin composition according to claim 3.

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