JPH09111189A - Optical adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical adhesive composition having such a high refractive index as to be difficult to realize hitherto by blending a specified vinyl compound that contains sulfur atoms with a vinyl compound that does not contain a sulfur atom. SOLUTION: This composition consists of 100 pts.wt. of at least one sulfur- containing vinyl compound selected among vinyl sulfide compounds represented by formula I (wherein R<1> , R<2> , R<3> and R<4> are each H, a halogeno or a 1-6C alkyl; and (n) is 0 to 10), methacrylic acid derivatives represented by formula II (wherein R<5> , R<6> , R<7> and R<8> are each H, a halogeno or a 1-6C alkyl), and prepolymers obtained by the addition reaction of a methacrylic acid derivative of formula II to a thiol compound of formula III (wherein (m) is 1 to 4) and at most 500 pts.wt. vinyl compound that does not contain a sulfur atom. The prepolymer preferably comprises the one obtained by the addition reaction of the methacrylic acid derivative to the thiol compound at an equivalent ratio of the methacryloyl groups of the former to the functional mercapto groups of the latter of (0.05 to 1):1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for an optical adhesive used for laminating optical members made of glass, transparent plastic or the like. More specifically, the present invention relates to a composition for an optical adhesive that joins portions through which light passes, or couples optical paths such as optical fibers to each other or optical fibers and optical waveguides in an optimal optical coupling state.

[0002]

2. Description of the Related Art Assembling of optical components used in optical communication originally employed methods such as soldering and laser welding from the viewpoint of reliability. However, these methods are unsuitable for areas where light passes or where high temperatures are disliked, and because they have the drawbacks of requiring advanced technology, the use of adhesives has increased in recent years. There is. In particular, for optical adhesives used for bonding optical members such as lenses and prisms, or for light passage such as adhesive coupling between various optical fibers and optical waveguides, (1) optical members such as glass and fiber Various properties such as matching refractive index and matching refractive index (2) transparency are required. Conventionally, as such an adhesive, a cationic UV curable resin using an epoxy base resin or a radical UV curable resin using an acrylic base resin has been used. However, their refractive index (nD) is in the range 1.50 to 1.59. On the other hand, as a low refractive index adhesive having a refractive index of 1.50 or less, an epoxy adhesive containing fluorine is known, and it is commercially available as an optical adhesive having a good transparency capable of controlling the refractive index. As a high refractive index adhesive (1.59 or more),
Epoxy adhesives containing bromine are known, but their refractive index is limited to 1.61.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polymerizable composition used for obtaining an optical adhesive having a high refractive index, which has hitherto been difficult to realize.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a polymerizable composition comprising a vinyl compound containing a sulfur atom and a vinyl compound containing no sulfur atom is used. It was found that the above-mentioned optical adhesive having a high refractive index can be obtained, and the present invention has been completed. That is, the present invention

(A) General formula (I):

Embedded image

[In the formula, R ¹ , R ² , R ³ and R ^{4, which} may be the same or different, each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms. n is 0
Represents an integer of 10 to 10. ] A vinyl sulfide compound represented by the following: (B) General formula (II):

[0007]

Embedded image

[In the formula, R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms. ] And a methacrylic acid derivative represented by the above general formula (II) and a general formula (III):

[0009]

[Chemical 6]

[In the formula, m represents an integer of 1 to 4. ] 100 parts by weight of a vinyl compound containing at least one sulfur atom selected from the group consisting of prepolymers obtained by addition reaction with a thiol represented by the formula, and 500 parts by weight of a vinyl compound containing no sulfur atom The present invention provides a composition for an optical adhesive, which comprises:

The optical adhesive obtained from the polymerizable composition of the present invention comprises a sulfur atom-containing vinyl compound represented by the above general formula and a sulfur atom-free vinyl compound as the main base resin. Therefore, the refractive index can be precisely and arbitrarily controlled within the range of 1.55 to 1.74 by changing the mixing ratio.
As a result, the refractive index of the optical adhesive can be matched with the refractive index of various optical glasses and various transparent plastics. Therefore, the light reflection at those joints or joints can be reduced to a theoretical limit value, and those joints or joints have appropriate flexibility and can be used as an adhesive or a durable adhesive. It has excellent performance.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The halogen atom represented by R ¹ , R ² , R ³ and R ⁴ in the vinyl sulfide compound represented by the general formula (I) of the component (A) in the present invention is chlorine. , Bromine, iodine, etc., and have 1 to 1 carbon atoms.
Examples of the alkyl group of 6 include linear and branched alkyl groups such as methyl, ethyl, propyl, i-propyl, butyl, sec-butyl, t-butyl, pentyl and hexyl. Preferably, R ^{1 to} R ⁴ are all hydrogen atoms, n is 0 to 10, and more preferably 0.
˜2, especially 0. Examples of the vinyl sulfide compound include the following compounds.

Bis (4-vinylthiophenyl) sulfide, bis (3-methyl-4-vinylthiophenyl) sulfide, bis (3,5-dimethyl-4-vinylthiophenyl) sulfide, bis (2,3,5) , 6-Tetramethyl-4-vinylthiophenyl) sulfide, bis (3-
Hexyl-4-vinylthiophenyl) sulfide, bis (3,5-dihexyl-4-vinylthiophenyl) sulfide, bis (3-chloro-4-vinylthiophenyl)
Sulfide, bis (3,5-dichloro-4-vinylthiophenyl) sulfide, bis (2,3,5,6-tetrachloro-4-vinylthiophenyl) sulfide, bis (3-bromo-4-vinylthiophenyl) ) Sulfide,
Bis (3,5-dibromo-4-vinylthiophenyl) sulfide, bis (2,3,5,6-tetrabromo-4-)
Vinylthiophenyl) sulfide, preferably bis (4-vinylthiophenyl) sulfide, bis (2,2
3,5,6-Tetrachloro-4-vinylthiophenyl)
Sulfide, bis (2,3,5,6-tetrabromo-4
-Vinylthiophenyl) sulfide and the like.

The method for producing the vinyl sulfide compound is not particularly limited, but, for example, after reacting bis (4-mercaptophenyl) sulfide with dichloroethane in the presence of alkali, dehydrochlorination treatment with alkali is performed. And the like. In this case, compounds having different numbers of n in the above general formula (I) can be obtained by changing the reaction conditions such as the amount of dichloroethane used and the charging method.

As the halogen atom represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ and the alkyl group having 1 to 6 carbon atoms in the methacrylic acid derivative represented by the general formula (II) as the component (B). May be the same as R ^{1 to} R ^{4 in} the general formula (I). Preferably, R ^{5 to} R ⁸ are all hydrogen atoms. Examples of such methacrylic acid derivatives include the following compounds.

Bis (4-methacryloylthiophenyl)
Sulfide, bis (3-methyl-4-methacryloylthiophenyl) sulfide, bis (3,5-dimethyl-4)
-Methacryloylthiophenyl) sulfide, bis (2,3,5,6-tetramethyl-4-methacryloylthiophenyl) sulfide, bis (3-hexyl-4-)
Methacryloylthiophenyl) sulfide, bis (3,
5-dihexyl-4-methacryloylthiophenyl) sulfide, bis (3-chloro-4-methacryloylthiophenyl) sulfide, bis (3,5-dichloro-4-)
Methacryloylthiophenyl) sulfide, bis (2,
3,5,6-tetrachloro-4-methacryloylthiophenyl) sulfide, bis (3-bromo-4-methacryloylthiophenyl) sulfide, bis (3,5-dibromo-4-methacryloylthiophenyl) sulfide,
Bis (2,3,5,6-tetrabromo-4-methacryloylthiophenyl) sulfide, preferably bis (4
-Methacryloylthiophenyl) sulfide, bis (2,3,5,6-tetrachloro-4-methacryloylthiophenyl) sulfide, bis (2,3,5,6-tetrabromo-4-methacryloylthiophenyl) sulfide and the like. .

The method for producing the above-mentioned methacrylic acid derivative is not particularly limited, and, for example, bis (4
-Mercaptophenyl) sulfide and methacrylic acid chloride may be reacted.

M in the thiol represented by the above general formula (III) used for producing the prepolymer of the component (C)
1 to 4, especially 2 is preferable. The method for producing the prepolymer is not particularly limited, and for example, in the presence of a base catalyst,
Examples thereof include a method in which a methacrylic acid derivative represented by the general formula (II) and an thiol represented by the general formula (III) are subjected to an addition reaction. Here, the ratio of the mercapto group of the thiols to the methacryloyl group of the methacrylic acid derivative is preferably a functional group equivalent ratio in the range of 0.05 to 1.0, and particularly preferably 0.2 to 0.6. When the functional group equivalent ratio is greater than 1.0, unreacted mercapto groups remain in the obtained prepolymer and the stability of the prepolymer deteriorates. The reaction temperature is preferably 0 to 80 ° C, particularly preferably 20 to 60 ° C.

As the component (C), particularly bis (4-
Methacryloylthiophenyl) sulfide, bis (2,
When a prepolymer obtained from 3,5,6-tetrachloro-4-methacryloylthiophenyl) sulfide or bis (2,3,5,6-tetrabromo-4-methacryloylthiophenyl) sulfide and thiols is used , Get good results.

The sulfur atom-free vinyl compound in the present invention is not particularly limited, and examples thereof include (meth) acrylic acid derivatives, aromatic vinyl compounds, alicyclic vinyl compounds and vinyl ethers. Known compounds can be mentioned. These alone are 2
More than one species may be used in combination. Further, not only a monofunctional compound but also a polyfunctional compound can be selected according to the purpose of use. Examples of the vinyl compound containing no sulfur atom include the following compounds.
In the present specification, both acrylic acid and methacrylic acid are collectively represented by the term "(meth) acrylic acid", and similarly, the term "(meth) acrylate" represents both acrylate and methacrylate. I shall. Further, "EO" means ethylene oxide.

Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate,
Isobutyl (meth) acrylate, tridecyl (meth)
Acrylate, n-lauryl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate. , Adamantyl (meth) acrylate, glycidyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 1-naphthyl (meth) acrylate, chlorophenyl (meth) acrylate, bromophenyl (meth) acrylate, tribromophenyl ( (Meth) acrylate,
Methoxyphenyl (meth) acrylate, cyanophenyl (meth) acrylate, chloromethyl (meth) acrylate, bromoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid Monofunctional (meth) acrylates such as polyethylene glycol ester, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, (meth) acrylic acid.

Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) ) Acrylate, tripropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (or tetra) (meth) Acrylate, dibromoneopentyl glycol dimethacrylate, EO adduct of tetrabromobisphenol A di (meth) acrylate, EO
Unsaturated fatty acids and their derivatives such as polyol poly (meth) acrylate such as modified bisphenol A di (meth) acrylate and EO modified bisphenol F di (meth) acrylate.

Aromatic vinyl compounds such as styrene, α-methylstyrene, α-methylstyrene dimer, vinyltoluene, chlorostyrene, bromostyrene, chloromethylstyrene, methoxystyrene and divinylbenzene. Cyclohexene, 4-vinylcyclohexane, 1,
5-cyclooctadiene, 5-vinylcyclo [2,2,
1] Alicyclic vinyl compounds such as hept-2-ene.

Vinyl acetate, ethyl vinyl ether, n-
Propyl vinyl ether, isobutyl vinyl ether,
t-butyl vinyl ether, n-amyl vinyl ether, isoamyl vinyl ether, cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether, n-octadecyl vinyl ether, dodecyl vinyl ether,
Propenyl ether propylene carbonate, ethylene glycol monovinyl ether, ethylene glycol divinyl ether, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, butanediol monovinyl ether, butanediol divinyl ether, hexanediol monovinyl ether, Examples thereof include vinyl ether compounds such as hexanediol divinyl ether, cyclohexanedimethanol monovinyl ether, cyclohexanedimethanol divinyl ether, and phenyl vinyl ether, and preferably glycidyl (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, and tetrahydr. Furfuryl (meth) acrylate, EO-modified bisphenol A di (meth) acrylate, EO-modified bisphenol F di (meth) (meth) acrylic acid esters such as acrylates.

In the present invention, 500 parts by weight or less, preferably 300 parts by weight, of a vinyl compound containing no sulfur atom is added to 100 parts by weight of a vinyl compound containing a sulfur atom.
Even better results can be obtained by using less than 100 parts by weight, particularly preferably less than 100 parts by weight.

The optical adhesive composition of the present invention is usually used for adhering an optical member by polymerizing the composition by photopolymerization, thermal polymerization or the like using a radical polymerization initiator. When photopolymerizing, as the radical polymerization initiator,
For example, 2,2-diethoxyacetophenone, 2,2-
Diethoxy-2-phenylacetophenone, benzophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzoinethyl Carbonyl compounds such as ether, benzoin isobutyl ether, benzoin isopropyl ether, 1-hydroxycyclohexyl phenyl ketone, 4,4-bisdimethylaminobenzophenone, methylbenzoisoformate, benzyldimethylketal, benzoylbenzoic acid, 2-chlorothioxanthone, 2 ，
UV polymerization initiators such as thioxanthones such as 4-diethylthioxanthone and 2,4-dimethylthioxanthone are used.

In the case of thermal polymerization, examples of the radical polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobisisovaleronitrile, 2,
Azo compounds such as 2′-azobis (2,4-dimethylvaleronitrile), ketone peroxides such as methyl ethyl ketone peroxide and methyl isobutyl ketone peroxide, diacyl such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide. A thermal polymerization initiator such as peroxides is used. Thermal polymerization temperature is 10 to 20
The temperature is in the range of 0 ° C, preferably 30 to 100 ° C.

The amount of the radical polymerization initiator used cannot be unconditionally determined because it varies depending on the type of the radical polymerization initiator, the type of the charged vinyl compound and the composition ratio, but it is usually a vinyl compound containing a sulfur atom and a sulfur atom. It is in the range of 0.5 to 6% by weight, and preferably in the range of 1 to 3% by weight, based on the total amount of the composition for optical adhesives of the present invention, which comprises a vinyl compound containing no atom.

In the present invention, if necessary, additives such as a silane coupling agent, a titanium coupling agent, a flexibility-imparting agent, a curing accelerator and a characteristic modifier may be added. it can. The properties of the composition can be further modified by adding these additives individually or in combination to the adhesive composition of the present invention.

For example, as a silane coupling agent added to enhance the adhesiveness of the adhesive composition of the present invention,
γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -Β-
(Aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-
Methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, N-β- (N-
Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride, methyltrimethoxysilane,
Methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl (3- (trimethoxysilyl) propyl) ammonium Chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane,
Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltriethoxysilane, benzyltrimethylsilane, vinyltris (2-methoxyethoxy) silane, γ-methacryloxypropyltris (2-methoxyethoxy) silane, β- (3,4- Epoxycyclohexyl) ethyltrimethoxysilane, γ-
Examples thereof include ureidopropyltriethoxysilane, γ-isocyanurylpropyltriethoxysilane, and n-octyltriethoxysilane.

Thus, the composition for optical adhesives of the present invention can be prepared by mixing the desired components by a method known per se, and the composition before addition of the above-mentioned radical polymerization initiator and the composition after addition thereof can be used. Is also within the scope of the present invention.
In use, by polymerizing and curing the composition using the above radical polymerization initiator, for example, various optical glasses having a refractive index of 1.55 to 1.74 and various optical members such as transparent plastics can be prepared. Can be widely used for bonding.

[0032]

EXAMPLES The present invention is described in more detail below with reference to synthetic examples and examples, but the present invention is not limited thereto. Synthesis Example 1 Synthesis of Prepolymer In a 1-liter four-necked flask, bis (4-) in which R ⁵ , R ⁶ , R ⁷ and R ⁸ in the general formula (II) are hydrogen atoms.
Methacryloylthiophenyl) sulfide 500g
(1.29 mol), 220 g of dichloromethane and p-
Methoxyphenol (0.08 g) was added, and the mixture was stirred at 40 ° C. until it became transparent.
After adding 8 g, 60 g of bis (2-mercaptoethyl) sulfide in which n is 2 in the general formula (III)
(0.389 mol) was added dropwise, and the mixture was stirred at 40 ° C for 15 minutes. In this case, the functional group equivalent ratio is 0.324. Then, dichloromethane was distilled off under reduced pressure to obtain 560 g of a pale yellow liquid methacrylic acid prepolymer. The refractive index of this liquid was 1.660. The gel permeation chromatography analysis result of this liquid shows that the average molecular weight is 1.
000 prepolymer and bis (4-methacryloylthiophenyl) sulfide.

Examples 1 to 7 The ingredients shown in Table 1 were mixed and stirred to prepare a test optical adhesive composition. This composition was cured under the following conditions, and its refractive index, light transmittance, photocurability, adhesive strength, and water resistant adhesiveness were evaluated. Curing condition is 10mW / c
It was cured by photopolymerization for 5 minutes by ultraviolet irradiation of m ² and was further post-cured at 60 ° C. for 1 hour. (1) The refractive index was measured at 25 ° C. using an Abbe refractometer. (2) The light transmittance was measured at a wavelength of 1.3 μm using a 1 mm thick cured sheet in an automatic spectrophotometer. (3) The photocurability is as shown in FIG.
Evaluated by adhering aluminum square bar to Pyrex glass with a thickness of 1mm using drops and measuring its torsional shear strength [UV irradiation 2 minutes (Table 1 upper value) and 5 minutes later (Table 1 lower value)] did. (4) The adhesive strength was evaluated by the adhesive strength of Pyrex glass / Pyrex glass. As shown in FIG. 3, one drop of the test composition was used to prepare a Pyrex glass-bonded adhesive piece, and as shown in FIG. 4, the adhesive piece was put in a sample holder and a tensile tester was used at a speed of 5 mm / min. The pressure plate was compressed and the shear strength was measured. (5) As for the water-proof adhesive strength, the adhesive piece shown in FIG.
After pressure cooker treatment for 10 hours at 100 ° C and RH, the adhesive strength was measured in the same manner as (4).

Examples 8 and 9 Using the ingredients shown in Table 1, compositions for optical adhesives were prepared in the same manner as in Examples 1 to 7, and the refractive index, the light transmittance, the adhesive strength, and the water resistant adhesive strength were prepared. Was evaluated. The curing conditions are 100 ° C,
Heated for 2 hours. The measurement conditions are the same as in Examples 1 to 7, and the obtained results are shown in Table 1 together.

[0035]

[Table 1]

FIG. 1 is a graph plotting the refractive index and the sulfur atom content of the optical adhesives obtained from the compositions of the vinyl compound containing a sulfur atom and the vinyl compound containing no sulfur atom in Table 1. Show. From these results, the optical adhesive obtained from the composition for optical adhesives of the present invention is excellent in light transmittance and has a refractive index of 1.5.
It has been clarified that it can be arbitrarily controlled with an accuracy of 0.0005 in the range of 5 to 1.74.

[0037]

When the optical adhesive of the present invention is applied to the optical path coupling / bonding in an optical member, the decrease in the light transmittance at the bonding / bonding portion is extremely small, so that it can be matched with the refractive index of various optical members. Optimal optical coupling can be formed.
In addition, since it is also moderately flexible and has excellent practical performance such as adhesiveness and durable adhesiveness, it is possible to realize an adhesive joint having excellent practical performance.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the refractive index of an optical adhesive and the sulfur content.

FIG. 2 is a schematic front view of a torsion shear adhesive strength test piece for photocurability evaluation.

FIG. 3 is a schematic perspective view showing an adhesive piece for Pyrex glass / adhesive strength test of Pyrex glass.

FIG. 4 is a schematic cross-sectional view showing a method for measuring the adhesive strength of Pyrex glass / Pyrex glass.

[Explanation of symbols]

1: Pyrex glass, 2: Cured test composition (adhesive), 3: Aluminum square bar (5 mm square), 4: Test adhesive piece, 5: Pressure plate, 6: Test adhesive piece holder

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumasa Yamamoto 1 346 Miyanishi, Harima-cho, Kako-gun, Hyogo Prefecture 1st Research Center, Sumitomo Seika Co., Ltd. (72) Michio Suzuki Suzuki 346 Miyanishi, Harima-cho, Kako-gun, Hyogo Address 1 Sumitomo Seika Chemical Co., Ltd. 1st Laboratory

Claims (4)

[Claims] 1. (A) General formula (I): [In the formula, R ¹ , R ² , R ³ and R ^{4, which} may be the same or different, each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms. n represents an integer of 0 to 10. ] A vinyl sulfide compound represented by the following: (B) General formula (II): [In the formula, R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms. ] And a methacrylic acid derivative represented by the above general formula (II) and a general formula (III): [In formula, m represents the integer of 1-4. ] 100 parts by weight of a vinyl compound containing at least one sulfur atom selected from the group consisting of prepolymers obtained by addition reaction with a thiol represented by the formula, and 500 parts by weight of a vinyl compound containing no sulfur atom A composition for an optical adhesive, comprising: 2. The composition for an optical adhesive according to claim 1, wherein R ¹ , R ² , R ³ and R ⁴ of the vinyl sulfide compound represented by the general formula (I) are hydrogen atoms. 3. The composition for an optical adhesive according to claim 1, wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ of the methacrylic acid derivative represented by the general formula (II) are hydrogen atoms. 4. The prepolymer is based on the methacryloyl group of the methacrylic acid derivative represented by the general formula (II),
The composition for optical adhesives according to claim 1, which is obtained by addition reaction of a mercapto group of a thiol represented by the general formula (III) in a functional group equivalent ratio of 0.05 to 1.0. Stuff.