Photocurable composition

Abstract

To provide a new photocurable composition that achieves improved viscosity as compared to the current material composition and can also maintain the refractive index comparable to that of the current material composition.SOLUTION: A photocurable composition includes a bismethacrylate having an alicyclic skeleton of a predetermined structure, a monomethacrylate having an alicyclic skeleton of a predetermined structure, and an alicyclic skeleton acrylate polymer having an alicyclic skeleton of a predetermined structure with a molecular weight of 2000-20000.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photocurable composition suitable for optical sheets, optical plastic members, etc. In particular, the present invention relates to a photocurable composition containing an alicyclic skeleton bis(meth)acrylate. [Background technology]

[0002] Photocurable resins are resins that can be polymerized and hardened by light or electromagnetic waves of a specific wavelength. Compared to thermosetting resins, photocurable resins improve productivity by shortening the hardening time and shortening the production time, and they have functions that can only be achieved by photocurable resins, so they are used, for example, in optical sheets and optical plastic components.

[0003] Conventionally, as photocurable compositions suitable for optical sheets, optical plastic members, etc., for example, Patent Documents 1 and 2 disclose tricyclo[5.2.1.0 2,6 ]A photocurable composition comprising a bis(meth)acrylate compound substituted at the 3,8 (or 3,9 or 4,8) positions of a decane skeleton and a mercapto compound is disclosed.

[0004] Patent Document 3 discloses a photocurable composition that can give a cured product that can be easily released from a mold in a molding step, the photocurable composition containing 70 to 99 parts by mass of an alicyclic skeleton bis(meth)acrylate, 1 to 30 parts by mass of an alicyclic skeleton mono(meth)acrylate, 1 to 10 parts by mass of at least a bifunctional mercapto compound, and 0.1 to 5 parts by mass of a silicone oil.

[0005] Patent Document 4 describes, for example, bis(hydroxymethyl)tricyclo[5.2.1.0 2,6 ]decane=dimethacrylate and other alicyclic skeleton bis(meth)acrylates, such as bis(hydroxymethyl)tricyclo[5.2.1.0 2,6 ]decane=β-carboxylpropionate methacrylate or another alicyclic skeleton-containing mono(meth)acrylate having a carboxyl group is disclosed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-152510 [Patent Document 2] JP 2001-342222 A [Patent Document 3] JP 2002-121229 A [Patent Document 4] JP 2003-335823 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to use conventional photocurable resins for optical applications, it is necessary to adjust the optical properties and the physical properties of the photocurable resin to suit the production method, so it was a challenge to balance performance and productivity. In particular, when molding with a mold, in the process of filling the molding die with resin using a device that measures and fills the resin composition, problems have been pointed out such as the low viscosity of the resin causing leakage from the filling port, resulting in variations in the filling amount. When the viscosity of the resin is adjusted to solve this problem, the change in composition can result in a large change in the optical properties, particularly the refractive index, compared to the resin composition before the viscosity adjustment.

[0008] Therefore, an object of the present invention is to provide a new photocurable composition that can have a higher viscosity than current material compositions, while maintaining a refractive index equivalent to that of current material compositions. [Means for solving the problem]

[0009] The present invention proposes a photocurable composition containing an alicyclic skeleton bis(meth)acrylate represented by the following formula (1) (also referred to as "component A"), an alicyclic skeleton mono(meth)acrylate represented by the following formula (2) (also referred to as "component B"), and an alicyclic skeleton acrylate polymer represented by the following formula (3) which has an alicyclic structure and has a molecular weight of 2,000 to 20,000 (also referred to as "component C").

[0010] TIFF0007645082000001.tif94153

[0011] In formula (1), R1 and R2 each independently represent a hydrogen atom or a methyl group, m represents 1 or 2, n represents 0 or 1, and k and l each independently represent 0, 1, or 2.

[0012] TIFF0007645082000002.tif70153

[0013] In formula (2), R3 represents a hydrogen atom or a methyl group, R4 represents a divalent hydrocarbon residue, m represents 1 or 2, n represents 0 or 1, and r and s each independently represent 0, 1, or 2.

[0014] TIFF0007645082000003.tif94153 Effect of the Invention

[0015] According to the present invention, it is possible to increase the viscosity compared to the current material composition, i.e., a photocurable composition containing components A and B but not containing component C, while still maintaining the same refractive index as the current material composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] An embodiment of the present invention will be described in detail below, although the present invention is not limited to the following embodiment.

[0017] <This photocurable composition> A photocurable composition according to one embodiment of the present invention (hereinafter referred to as "the photocurable composition") contains the following Components A, B, and C.

[0018] (Component A) Component A is an alicyclic skeleton-containing bis(meth)acrylate (hereinafter sometimes abbreviated as "bis(meth)acrylate") represented by formula (1).

[0019] TIFF0007645082000004.tif94153

[0020] In formula (1), R1 and R2 each independently represent a hydrogen atom or a methyl group, m represents 1 or 2, n represents 0 or 1, and k and l each independently represent 0, 1, or 2.

[0021] Specific examples of bis(meth)acrylates include bis(hydroxy)tricyclo[5.2.1.0 2,6 ]Decane diacrylate, bis(hydroxy)tricyclo[5.2.1.0 2,6 ]Decane dimethacrylate, bis(hydroxy)tricyclo[5.2.1.0 2,6 ]decane=acrylate methacrylate and mixtures thereof, bis(hydroxy)pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]Pentadecane diacrylate, bis(hydroxy)pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]Pentadecane dimethacrylate, Bis(hydroxy)pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]pentadecane=acrylate methacrylate, and mixtures thereof.

[0022] Of these, bis(hydroxymethyl)tricyclo[5.2.1.0 2,6 ]Decane = diacrylate, bis(hydroxymethyl)tricyclo[5.2.1.02,6 ]Decane = dimethacrylate, bis(hydroxymethyl)tricyclo[5.2.1.0 2,6 ]decane=acrylate, methacrylate, and mixtures thereof are preferred. These bis(meth)acrylate compounds can be used alone or in combination of two or more kinds.

[0023] The content of the component A is preferably 10 to 90 parts by mass relative to 100 parts by mass of the total of the components A and B, and more preferably 20 parts by mass or more or 80 parts by mass or less, and even more preferably 30 parts by mass or more or 70 parts by mass or less.

[0024] (Component B) Component B is an alicyclic skeleton-containing mono(meth)acrylate (also referred to as "component B") represented by the following formula (2).

[0025] TIFF0007645082000005.tif70153

[0026] In formula (2), R3 represents a hydrogen atom or a methyl group, R4 represents a divalent hydrocarbon residue, m represents 1 or 2, n represents 0 or 1, and r and s each independently represent 0, 1, or 2.

[0027] Examples of the divalent hydrocarbon residue defined by R4 above include an ethylene group, a vinylene group, a trimethylene group, an o-phenylene group, and a 1,2-cyclohexylene group, and preferably have a carbon number of 8 or less. In addition, such a divalent hydrocarbon residue may have a substituent such as a carboxyl group, a hydroxyl group, or a sulfo group.

[0028] Specific examples of the alicyclic skeleton mono(meth)acrylate (hereinafter sometimes abbreviated as mono(meth)acrylate) represented by formula (2) constituting component B include bis(hydroxy)tricyclo[5.2.1.0 2,6 ]Decane=monoacrylate, bis(hydroxy)tricyclo[5.2.1.0 2,6]Decane=monomethacrylate, bis(hydroxy)tricyclo[5.2.1.0 2,6 ]decane=acrylate methacrylate and mixtures thereof, bis(hydroxy)pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]Pentadecane monoacrylate, bis(hydroxy)pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]Pentadecane monomethacrylate, bis(hydroxy)pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]pentadecane=acrylate methacrylate and mixtures thereof, and the like, are reaction products of hydroxyl group-containing mono(meth)acrylate compounds with intramolecular acid anhydrides of polycarboxylic acids, such as succinic anhydride, maleic anhydride, glutaric anhydride, 3-methylglutaric anhydride, phthalic anhydride, trimellitic anhydride, and the like.

[0029] Of these, bis(hydroxymethyl)tricyclo[5.2.1.0 2,6 ]Decane=monoacrylate, bis(hydroxymethyl)tricyclo[5.2.1.0 2,6 ]Decanol monomethacrylate and its mixtures with succinic anhydride and glutaric anhydride are preferred. These mono(meth)acrylates may be used alone or in combination.

[0030] In addition, when the alicyclic skeleton bis(meth)acrylate is produced, the alicyclic skeleton mono(meth)acrylate may be produced in some cases. In such a case, the mixture of Component A and Component B may be used as it is as a raw material for the photocurable composition.

[0031] The content of the component B is preferably 10 to 90 parts by mass, more preferably 20 parts by mass or more or 80 parts by mass or less, and even more preferably 30 parts by mass or more or 70 parts by mass or less, per 100 parts by mass of the total of the components A and B. If the proportion of the mono(meth)acrylate is too low, the effect of improving the adhesiveness cannot be obtained, and conversely, if it is too high, the heat resistance of the cured resin may decrease.

[0032] (Component C) Component C is an alicyclic skeleton-containing acrylate polymer (hereinafter sometimes abbreviated as "acrylate polymer") that has an alicyclic structure represented by the following formula (3) and has a molecular weight of 2,000 to 20,000.

[0033] TIFF0007645082000006.tif94153

[0034] The alicyclic structure represented by the above formula (3) has a large effect on the optical properties, particularly the refractive index, and if Component C has this alicyclic structure, when a photocurable composition is prepared by blending Component C with Component A and Component B, the refractive index can be maintained at the same level as that of a photocurable composition not blended with Component C. Furthermore, by adjusting the molecular weight and blending amount of Component C, the viscosity of the photocurable composition can be adjusted.

[0035] A specific preferred example of the acrylate polymer is an alicyclic skeleton-containing acrylate polymer represented by the following formula (4).

[0036] TIFF0007645082000007.tif94153

[0037] In formula (4), each R3 independently represents a hydrogen atom, a methyl group, or an aromatic ring. In this case, the aromatic ring may be a single ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a tetracene ring. Among these, a benzene ring and a naphthalene ring are preferred, and a benzene ring is more preferred. In formula (4), R4, R5, R7 and R8 each independently represent a hydrogen atom or a methyl group, and o, p, q and r each independently represent a value within the range of 0 to 40.

[0038] TIFF0007645082000008.tif94153

[0039] TIFF0007645082000009.tif94153

[0040] Specific examples of component C include an acrylate polymer represented by the following formula (5), an acrylate polymer represented by the following formula (6), or a mixture thereof.

[0041] TIFF0007645082000010.tif94153

[0042] TIFF0007645082000011.tif94153

[0043] In formula (5) and formula (6), o, p, q and r each independently represent The value is in the range of 0 to 40.

[0044] From the viewpoint of increasing viscosity, the molecular weight of the acrylate polymer is preferably 2000 or more, more preferably 3000 or more, more preferably 4000 or more, and even more preferably 5000 or more. On the other hand, from the viewpoint of solubility, the molecular weight is preferably 20000 or less, more preferably 15000 or less, more preferably 10000 or less, and even more preferably 7000 or less.

[0045] From the viewpoint of increasing viscosity, the content of component C, i.e., the acrylate polymer, is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, relative to 100 parts by mass of the total content of components A and B. On the other hand, from the viewpoint of solubility, the content is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less.

[0046] (Other Ingredients) The present photocurable composition may contain components other than Components A, B and C (also referred to as “other components”) as necessary. Examples of the other components include radically polymerizable monomers other than Components A, B, and C, photopolymerization initiators, chain transfer agents, release agents, antioxidants, UV absorbers, UV stabilizers, dyes and pigments, fillers, and silane coupling agents.

[0047] Examples of radically polymerizable monomers other than components A, B, and C include methacrylate compounds such as methyl methacrylate, 2-hydroxyethyl methacrylate, phenyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 2,2-bis[4-(β-methacryloyloxyethoxy)phenyl]propane, 2,2-bis[4-(β-methacryloyloxyethoxy)cyclohexyl]propane, 1,4-bis(methacryloyloxymethyl)cyclohexane, and trimethylolpropane trimethacrylate; styrene-based compounds such as styrene, chlorostyrene, divinylbenzene, and α-methylstyrene; and acrylic acid derivatives such as acrylamide, methacrylamide, acrylonitrile, and methacrylonitrile. Among these, 2,2-bis[4-(β-methacryloyloxyethoxy)phenyl]propane, 2,2-bis[4-(β-methacryloyloxyethoxy)cyclohexyl]propane, 1,4-bis(methacryloyloxymethyl)cyclohexane, trimethylolpropane trimethacrylate, and mixtures thereof are particularly preferred. The radically polymerizable monomer is preferably blended in an amount of 50 parts by mass or less per 100 parts by mass of the total of Components A, B and C.

[0048] Specific examples of the photopolymerization initiator include benzophenone, benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,6-dimethylbenzoyldiphenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. These polymerization initiators may be used alone or in combination of two or more kinds.

[0049] The photopolymerization initiator is preferably blended in a proportion of 0.01 to 10 parts by mass, more preferably 0.1 part by mass or more or 5 parts by mass or less, relative to 100 parts by mass of the total of Components A, B, and C.

[0050] As the chain transfer agent, for example, a polyfunctional mercaptan compound having two or more thiol groups in the molecule may be used. By using the polyfunctional mercaptan compound in combination, it is possible to impart appropriate toughness to the cured product. Examples of the mercaptan compound include divalent to hexavalent thioglycolic acid esters or thiopropionic acid esters such as pentaerythritol tetrakis(β-thiopropionate), pentaerythritol tetrakis(β-thioglycolate), trimethylolpropane tris(β-thiopropionate), trimethylolpropane tris(β-thioglycolate), diethylene glycol bis(β-thiopropionate), diethylene glycol bis(β-thioglycolate, dipentaerythritol hexakis(β-thiopropionate), dipentaerythritol hexakis(β-thioglycolate); tris[2-β-thiopropionyloxy] [2-(β-thioglyconyloxy)propyl]triisocyanurate, tris[2-(β-thioglyconyloxy)ethyl]triisocyanurate, tris[2-(β-thiopropionyloxyethoxy)ethyl]triisocyanurate, tris[2-(β-thioglyconyloxy)ethoxy)ethyl]triisocyanurate, tris[2-(β-thiopropionyloxy)propyl]triisocyanurate, tris[2-(β-thioglyconyloxy)propyl]triisocyanurate, and other ω-SH group-containing triisocyanurates; and α,ω-SH group-containing compounds such as benzene dimercaptan, xylylene dimercaptan, and 4,4'-dimercaptodiphenyl sulfide. Among these, pentaerythritol tetrakis(β-thiopropionate), trimethylolpropane tris(β-thiopropionate), tris[2-(β-thiopropionyloxyethoxy)ethyl]triisocyanurate, and mixtures thereof are particularly preferred. The mercaptan compound is usually blended in a proportion of 30 parts by mass or less per 100 parts by mass of the total of Components A, B and C.

[0051] Examples of silane coupling agents include vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-(methacryloxypropyl)trimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane. Among these, γ-(methacryloxypropyl)trimethoxysilane, γ-(methacryloxypropyl)methyldimethoxysilane, γ-(methacryloxypropyl)methyldiethoxysilane, γ-(methacryloxypropyl)triethoxysilane, γ-(acryloxypropyl)trimethoxysilane, etc. have methacryl or acrylic groups in the molecule and can be copolymerized with compositions A and B of the present invention, and are therefore preferably used. The mass ratio is preferably 0.1 to 50 parts by mass, and more preferably 1 part by mass or more or 20 parts by mass or less, relative to 100 parts by mass of the total of components A, B and C.

[0052] The photocurable composition can be polymerized and cured by a known method to form a cured product. For example, the photocurable composition can be polymerized by irradiating it with active energy rays such as ultraviolet rays to obtain a cured product.

[0053] In this case, the amount of active energy rays to be irradiated is arbitrary as long as the photopolymerization initiator generates radicals. If the amount is too small, polymerization is incomplete, and the heat resistance and mechanical properties of the cured product are not fully expressed, while if the amount is too excessive, degradation due to light, such as yellowing of the cured product, occurs. Therefore, ultraviolet rays of 200 to 400 nm are preferably irradiated at 0.1 to 200 J / cm according to the monomer composition and the type and amount of the photopolymerization initiator. 2It is preferable to irradiate in the range of The active energy rays may be irradiated in several separate times, i.e., about 1 / 20 to 1 / 3 of the total amount of irradiation is irradiated in the first time, and the remaining amount is irradiated in the second and subsequent times, thereby obtaining a cured product with smaller birefringence. Specific examples of lamps that can be used include metal halide lamps and high pressure mercury lamps. For the purpose of quickly completing the curing by polymerization, photopolymerization and thermal polymerization may be performed simultaneously. Specifically, the polymerizable composition and the entire mold may be heated in the range of 30 to 300° C. simultaneously with the irradiation of active energy rays to perform curing.

[0054] The present photocurable composition can be used as an adhesive, various coating agents, inks, paints, etc. In addition, a cured product obtained by polymerizing and curing the present photocurable composition with light can be used as a photocurable member suitable for an optical sheet, an optical plastic member, etc.

[0055] <Explanation of terms> In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably greater than X" or "preferably smaller than Y". In addition, when an expression is used such as "X or more" (X is any number) or "Y or less" (Y is any number), the expression also includes the intention that "greater than X is preferable" or "less than Y is preferable." EXAMPLES

[0056] The present invention is further illustrated by the following examples, which are not intended to limit the invention in any way.

[0057] <Method of measuring refractive index> The measurement environment was a temperature of 20±5°C and humidity of (65±20)%. A Shimadzu refractive index measuring instrument (KPR-2) was used, and the light source used for the measurement was the D line (5877 nm) of the sodium spectrum.

[0058] <Method of measuring viscosity> The measurement environment was a temperature of 20±5°C and humidity of (65±20)%. A viscosity measuring instrument (TV-25) manufactured by Toki Sangyo Co., Ltd. was used, and measurements were taken at a water temperature of 25°C using a chiller (E 100) manufactured by LAUDA.

[0059] <Method of measuring Abbe number> The measurement environment was a temperature of 20±5°C and humidity of (65±20)%. A Shimadzu refractive index measuring instrument (KPR-2) was used, and the light source used for the measurement was the D line (5877 nm) of the sodium spectrum.

[0060] <Drip experiment method> 3 g of the photocurable composition (sample) obtained in the Examples and Comparative Examples was placed in a dispenser ("PSY-50E" manufactured by Musashi Co., Ltd.) equipped with a nozzle (hole inner diameter 1 mm, hole length 25 mm), and the amount (mass) of liquid leaking out of the nozzle due to its own weight within 1 minute was measured.

[0061] <Evaluation> The evaluation was based on the following criteria. ◯ (good): The amount of dripping was less than that of Comparative Example 1. × (poor): The amount of dripping is not less than that in Comparative Example 1.

[0062] Example 1 Bis(hydroxymethyl)tricyclo[5.2.1.0] represented by the following formula (1) as component A 2,6 ]decane=dimethacrylate and bis(hydroxymethyl)tricyclo[5.2.1.0]decane dimethacrylate represented by the following formula (2) as component B 2,6 85 parts by mass of a mixture of decane and monomethacrylate were mixed with 15 parts by mass of an alicyclic skeleton acrylate polymer (mass average molecular weight 5400, solid content 6.0 mgKOH / g, referred to as "acrylic polymer"), which is a copolymer represented by the following formula (5) as component C, and an appropriate amount of THF was added as a solvent and stirred at room temperature until it became homogeneous. This is referred to as the "THF mixed solution".

[0063] TIFF0007645082000012.tif94153

[0064] In the formula (1), R1 represents a methyl group, R2 represents a methyl group, m represents 1, n represents 0, and k and l each independently represent 1.

[0065] TIFF0007645082000013.tif70153

[0066] In formula (2), R3 represents a methyl group, R4 represents a divalent hydrocarbon residue, m represents 1, n represents 0, and r and s each independently represent 1.

[0067] TIFF0007645082000014.tif94153

[0068] In the formula (5), the real values ​​of o, p, q, and r are unknown, but are each independently a value within the range of 0 to 40 based on the molecular weight.

[0069] Next, the THF mixture was heated at 60° C. while the solvent was removed using a rotary evaporator to obtain a mixture (referred to as a “photocurable composition (sample)”). The viscosity, refractive index, and Abbe number of the obtained photocurable composition (sample) were measured, and a dripping experiment was also carried out. The results are shown in Table 1.

[0070] Example 2 80 parts by mass of the mixture of components A and B and 20 parts by mass of an acrylic polymer as component C were mixed, and an appropriate amount of THF was added as a solvent and stirred at room temperature until it became homogeneous. This is referred to as the "THF mixed liquid." The THF mixture was heated at 60° C. while the solvent was removed using a rotary evaporator to obtain a mixture (referred to as a “photocurable composition (sample)”). The viscosity, refractive index, and Abbe number of the obtained photocurable composition (sample) were measured, and a dripping experiment was also carried out. The results are shown in Table 1.

[0071] Example 3 75 parts by mass of the mixture of components A and B and 25 parts by mass of an acrylic polymer as component C were mixed, and an appropriate amount of THF was added as a solvent, followed by stirring at room temperature until the mixture became homogeneous. This is referred to as the "THF mixed liquid." The THF mixture was heated at 60° C. while the solvent was removed using a rotary evaporator to obtain a mixture (referred to as a “photocurable composition (sample)”). The viscosity, refractive index, and Abbe number of the obtained photocurable composition (sample) were measured, and a dripping experiment was also carried out. The results are shown in Table 1.

[0072] Example 4 70 parts by mass of the mixture of components A and B and 30 parts by mass of an acrylic polymer as component C were mixed, and an appropriate amount of THF was added as a solvent, followed by stirring at room temperature until the mixture became homogeneous. This is referred to as the "THF mixed liquid." The THF mixture was heated at 60° C. while the solvent was removed using a rotary evaporator to obtain a mixture (referred to as a “photocurable composition (sample)”). The viscosity, refractive index, and Abbe number of the obtained photocurable composition (sample) were measured, and a dripping experiment was also carried out. The results are shown in Table 1.

[0073] Example 5 71.4 parts by mass of a mixture of components A and B, 25.6 parts by mass of acrylic polymer as component C, 3 parts by mass of pentaerythritol tetra(3-mercaptopropionate), 2 parts by mass of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator, and 0.5 parts by mass of octamethylcyclotetrasiloxane were mixed, and an appropriate amount of THF was added as a solvent and stirred at room temperature until it became uniform. This is called the "THF mixed liquid". The THF mixture was heated at 60° C. while the solvent was removed using a rotary evaporator to obtain a mixture (referred to as a “photocurable composition (sample)”). The viscosity, refractive index, and Abbe number of the obtained photocurable composition (sample) were measured, and a dripping experiment was also carried out. The results are shown in Table 1.

[0074] Comparative Example 1 95 parts by mass of a mixture of components A and B, 3 parts by mass of pentaerythritol tetra(3-mercaptopropionate), 1 part by mass of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator, and 1 part by mass of octamethylcyclotetrasiloxane were mixed and stirred at room temperature until homogenous, to obtain a mixed liquid (referred to as a "photocurable composition (sample)"). The viscosity, refractive index, and Abbe number of the obtained photocurable composition (sample) were measured, and a dripping experiment was also carried out. The results are shown in Table 1.

[0075] [Table 1]

[0076] As a result of various tests conducted by the present inventors up to now, namely, by adding various compounds to an alicyclic skeleton bis(meth)acrylate represented by the following formula (1) (component A) and an alicyclic skeleton mono(meth)acrylate represented by the following formula (2) (component B) to prepare photocurable compositions and measuring their viscosity and refractive index, it was found that the alicyclic structure represented by the following formula (3) has a significant effect on the optical properties, particularly the refractive index, and it was also found that the viscosity of the photocurable composition can be adjusted by adjusting the molecular weight of the compound having the alicyclic structure.

[0077] TIFF0007645082000016.tif94153

[0078] In formula (1), R1 and R2 each independently represent a hydrogen atom or a methyl group, m represents 1 or 2, n represents 0 or 1, and k and l each independently represent 0, 1, or 2.

[0079] TIFF0007645082000017.tif70153

[0080] In formula (2), R3 represents a hydrogen atom or a methyl group, R4 represents a divalent hydrocarbon residue, m represents 1 or 2, n represents 0 or 1, and r and s each independently represent 0, 1, or 2.

[0081] TIFF0007645082000018.tif94153

[0082] In addition, in Examples 1-5, the compound blended as component C was the compound represented by the following formula (5), but it is assumed that this may have been converted to the compound represented by the following formula (6) by reaction with acrylic acid. Even in this case, since the same effect as that of formula (5) can be obtained, it is assumed that the same effect can be obtained by blending the compound represented by the above formula (5), the compound represented by the above formula (6), or a mixture thereof as component C with components A and B.

[0083] Furthermore, from the results of various tests conducted by the present inventors, it has been confirmed that additives such as a photopolymerization initiator, a chain transfer agent, and a release agent have almost no effect on the refractive index, viscosity, and Abbe number of the photocurable composition.

Claims

1. A photocurable composition comprising an alicyclic skeleton bis(meth)acrylate represented by the following formula (1) (also referred to as "component A"), an alicyclic skeleton mono(meth)acrylate represented by the following formula (2) (also referred to as "component B"), and an alicyclic skeleton acrylate-based polymer represented by the following formula (3) having an alicyclic structure and a molecular weight of 2,000 to 20,000 (also referred to as "component C"), wherein the photocurable composition contains 10 to 90 parts by mass of component B and 10 to 90 parts by mass of component C relative to a total content of 100 parts by mass of components A and B: (In formula (1), R1 and R2 each independently represent a hydrogen atom or a methyl group, m represents 1 or 2, n represents 0 or 1, and k and l each independently represent 0, 1, or 2.) (In formula (2), R 3 represents a hydrogen atom or a methyl group, R 4 represents a divalent hydrocarbon residue, m represents 1 or 2, n represents 0 or 1, and r and s each independently represent 0, 1, or 2.

2. 2. The photocurable composition according to claim 1, wherein the alicyclic skeleton acrylate polymer having a molecular weight of 2,000 to 20,000 is an alicyclic skeleton acrylate polymer represented by the following formula (4): (In formula (4), R3 each independently represents a hydrogen atom, a methyl group, or an aromatic ring. R4, R5, R7, and R8 each independently represent a hydrogen atom or a methyl group. R6 represents the following formula (R6-1) or the following formula (R6-2). o, p, q, and r each independently represent a value within the range of 0 to 40.)

3. The photocurable composition according to claim 1 or 2, which contains a photopolymerization initiator.

4. The photocurable composition according to any one of claims 1 to 3, which contains a chain transfer agent.

5. 5. The photocurable composition according to claim 1, further comprising a release agent.

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