JPH115952A - Optical adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive compsn. that exhibits only a small optical strain after cured, by incorporating at least one sulfur-contg. epoxy (meth) acrylate, a free-radical polymn. initiator, and at least one phenyl-group-contg. (meth)acrylate into the composition. SOLUTION: This compsn. contains at least one sulfur-contg. epoxy (meth) acrylate of the formula, a free-radical polymn. initiator. and 70 wt.% or lower at least one compd. selected from among phenyl (meth)acrylate, benzyl (meth) acrylate, phenoxyethyl (meth)acrylate, etc. A thermal polymn. initiator (e.g. azobisisobutyronitrile or benzoyl peroxide) or a photopolymn. initiator (e.g. an acylphosphine oxide or camphorquinone) is used as the free-radical polymn. initiator. In the formula, R is H or methyl ; Ph is phenyl ; and x is 0 or 1. A compd. of the formula, wherein R is methyl and x is 0, is bis(methacryloxy-2- hydroxypropylthiophenyl)sulfide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical adhesive composition used for bonding optical elements such as lenses, prisms, and optical waveguides, and more particularly, to a high refractive index and optical distortion after curing. The present invention relates to a small, high-performance optical adhesive composition.

[0002]

2. Description of the Related Art Conventionally, in assembling optical equipment such as a camera and a microscope, a transparent resin such as balsam or epoxy resin has been used as an adhesive for joining lenses and prisms. In recent years, with the development of the optoelectronics industry, applications for joining optical elements having advanced optical functions such as optical fibers and microlenses have been increasing, and bisphenol-A-epoxy (meth) acrylate and urethane have been used. Adhesives containing radically polymerizable monomers such as (meth) acrylates have also been widely used.

[0003] In particular, an optical device having a high degree of function, such as an optical modulator, an optical switch, or the like, which is formed by joining an optical waveguide element and a microlens or an optical fiber to form an optical circuit, has an adhesive having a folding ratio. Is needed. As such an adhesive, for example, JP-A-3-157471 discloses
Adhesives using N-vinylcarbazole are known.
Further, for example, Japanese Patent Application Laid-Open No. 2-113027 discloses a curable composition comprising 4,4′-dimercaptodiphenylsulfide dimethacrylate and polythiol,
It is said to be useful as an adhesive.

[0004]

However, N-vinylcarbazole, which is a main component of the high refractive index adhesive,
Although 4,4′-dimercaptodiphenyl sulfide dimethacrylate has a high refractive index, it cannot be used alone as an adhesive because it is a powdery or flake-like solid at room temperature.

[0005] For this reason, these compounds are used as an adhesive only after being mixed with other components which are liquid at normal temperature. However, the resin composition obtained in such a manner has a low mechanical property such as low temperature or vibration. When subjected to a shock or stored for a long period of time, the crystalline component tends to precipitate in the composition, and the refractive index fluctuates and coating cannot be performed.

An adhesive prepared using 4,4'-dimethicaptodiphenyl sulfide dimethacrylate has a large optical distortion after curing, especially when a photopolymerization initiator is added to rapidly cure the adhesive. Also increased.

[0007]

Technical Solution to Solve the Problems The present inventors have set forth: 1) an adhesive composition comprising at least one sulfur-containing epoxy (meth) acrylate represented by the following structural formula (1) and a radical polymerization initiator as components: By composing things,
Solved the above problem.

[0008]

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Here, R represents hydrogen or a methyl group, Ph represents a phenyl group, and the subscript x represents an integer of 0 or 1.

That is, an optical adhesive having a high refractive index after curing, excellent stability as a liquid adhesive, and small optical distortion after curing was obtained.

And 2) radical polymerization of at least one sulfur-containing epoxy (meth) acrylate represented by the following structural formula (1) and at least one phenyl group-containing (meth) acrylate selected from Group A below: It has been found that the above-mentioned problems can be solved also by constituting the adhesive composition using an initiator as a component.

[0012]

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Here, R represents hydrogen or a methyl group, Ph represents a phenyl group, and the subscript x represents an integer of 0 or 1.

Group A phenyl (meth) acrylate;
Benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate That is, the refractive index after curing is high, the stability as a liquid adhesive is excellent, and the optical distortion is high. An optical adhesive composition was obtained which has a small refractive index and can finely adjust the refractive index and viscosity according to the purpose.

3) The adhesive according to 1) or 2) above, wherein at least one photopolymerization initiator selected from acylphosphine oxide, diacylphosphine oxide and camphorquinone is used as a radical polymerization initiator. By constituting the composition, in addition to the features achieved in the above 1) and 2), a photocurable optical adhesive that has excellent photocurability, has no coloring, and is excellent in light resistance is also provided. I found what I could get.

The sulfur-containing (meth) acrylate represented by the following structural formula (1) used in the present invention is 1.63 after curing.
A compound having a high refractive index as described above, which is liquid at room temperature, has a high curing reactivity, and has a hydroxyl group in the molecule, so that it has good adhesiveness to optical glass and the like.

[0017]

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Here, R represents hydrogen or a methyl group, Ph represents a phenyl group, and the subscript x represents an integer of 0 or 1.

For this reason, by adding a radical polymerization initiator to the compound of the above formula (1), the compound can be used alone as an adhesive, and can be protected from various external changes such as temperature change and mechanical shock. However, the state is always stable, and the optical characteristics are also stable.

Although the reason is unclear, the compound of the above formula (1) has a feature that the optical distortion after curing is extremely small. Therefore, the compound which cures in a short time by using a photopolymerization initiator or the like is used. Even when used as a curable adhesive, it exhibits excellent optical characteristics without the problem of optical distortion.

Specific examples of the compound represented by the formula (1) of the present invention include, for example, bis (methacryloxy-2-hydroxypropyl-thiophenyl) wherein R in the formula (1) is a methyl group and the suffix X is 0. ) Sulfide, R in the formula (1)
Is a methyl group and the subscript X is 1, methacryloxy-2
-Hydroxypropyl-thiophenyl, 4-thiophenyl sulfide, (1) bis (acryloxy-2-hydroxypropyl-, wherein R is hydrogen and the subscript X is 0,
Thiophenyl) sulfide, and acryloxy-2-hydroxypropyl-thiophenyl, 4-thiophenyl sulfide wherein R in the formula (1) is hydrogen and the subscript X is 1 can be exemplified.

The compound of the formula (1) is prepared by, for example, reacting a known organic sulfur compound, 4,4'-thiobenzenethiol (trade name: MPS, manufactured by Sumitomo Seika Co., Ltd.) with glycidyl (meth) acrylate. Is obtained by

The following Group A compounds used in the present invention are as follows: Group A phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) Acrylates are all low-viscosity compounds containing a phenyl group in the molecule, can be mixed with the compound of the above formula (1) at an arbitrary ratio, and have the characteristic that optical distortion after curing is small. . For this reason, by using the compound of group A in combination with the compound of formula (1), the refractive index of the adhesive can be finely adjusted in a high refractive index region,
The viscosity of the adhesive can be adjusted in a wide range, and the application range of the adhesive of the present invention can be further expanded.

In the present invention, the phenyl group-containing (meth) acrylate of Group A is preferably used in a range of 70% by weight or less. This is because, when the amount of the compound of Group A exceeds 70% by weight, the refractive index of the adhesive decreases, and it becomes difficult to make use of the excellent high refractive index of the compound of the formula (1) of the present invention.

However, in order to utilize the good curing reactivity and low optical distortion of the compound of the formula (1) of the present invention, it is necessary to use the compound of Group A at 70% by weight or less. There is no.

Further, since the compounds of Group A are highly soluble, the polymerization initiator which is a crystalline solid can be rapidly mixed with the compound of the formula (1) at room temperature, and the addition of hydroxy methacrylate or a silane coupling agent can be carried out. It also has the advantage that known high-viscosity oligomers such as urethane acrylate and epoxy acrylate can be easily blended as desired.

Examples of the radical polymerization initiator used in the present invention include thermal polymerization initiators such as azobisisobutyronitrile, azobisdimethylvaleronitrile, benzoyl peroxide, cumene hydroperoxide, 1-hydroxy-cyclohexylphenyl ketone, Photopolymerization initiators such as acetophenone, benzophenone, benzoin ether, chlorothioxanthone, anthraquinone, acylphosphine oxide, diacylphosphine oxide and camphorquinone can be used.

When a thermal polymerization initiator is used as the radical polymerization initiator, the adhesive becomes a thermosetting type. As for the usage method, the optical parts coated with the adhesive are heated from 60 ° C to 150 ° C.
The adhesive is cured by heating in the temperature range of about 30 minutes to several hours.

When a photopolymerization initiator is added, a photocurable adhesive is obtained. As an application method, the optical component coated with the adhesive is irradiated with ultraviolet light or visible light having a short wavelength for several seconds to ten and several minutes to be cured. Light sources that can be used to cure the adhesive include ultraviolet light sources such as ultraviolet fluorescent lamps, high-pressure mercury lamps, and metal halide lamps, and wavelengths from 380 nm to 5 mm.
Visible light sources such as a visible light fluorescent lamp having an effective output in the visible light region with a short wavelength of 00 nm, a metal halide lamp for illumination, and a halogen lamp are exemplified.

Normally, when the adhesive is cured in a short time, the optical distortion of the cured adhesive tends to increase, and this tendency is particularly noticeable when the refractive index is high.

However, the adhesive of the present invention, despite having a high refractive index, has an excellent feature that, even when cured in a short time such as photopolymerization, the optical distortion is extremely small.

In the present invention, when a photopolymerization initiator is used as a radical polymerization initiator and used as a photopolymerization type adhesive, it is preferable to use acylphosphine oxide, diacylphosphine oxide, and camphorquinone. . When these photopolymerization initiators are used, excellent photocurability can be obtained, and an effect that the cured adhesive has no coloring and excellent light resistance can be obtained.

[0033] Since these photopolymerization initiators are colored yellow, the pale yellow or yellow color is also produced in the adhesive when it is mixed with the adhesive. Usually, when such a colored photopolymerization initiator is used, a brown or dark red color is generated after the curing of the adhesive, and the light resistance after the curing tends to be reduced and the color tends to be easily changed.

Surprisingly, however, when the photopolymerization initiator specified in the present invention is used for the adhesive of the present invention, the adhesive cured by irradiation with light becomes colorless and transparent, and furthermore, after the photocuring, the adhesive is cured for a long time. Irradiating with strong light over a wide range of colors, it exhibits extremely excellent performance in that discoloration and coloring hardly occur. It has also been found that the use of these photopolymerization initiators produces good results in that the adhesive properties of the adhesive of the present invention are also improved.

The acylphosphine oxide used in the present invention includes 2,4,6-trimethylbenzoyldiphenylphosphine oxide, benzoyldiphenylphosphine oxide, 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,4,6- Trimethylbenzoyl methoxy, phenylphosphine oxide and the like can be mentioned.

The diacylphosphine oxide used in the present invention includes bis (2,2) represented by the following structural formula (2).
6-dimethoxybenzoyl) -2,4,4 trimethylpentylphosphine oxide.

[0037]

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Further, in the present invention, optional components can be added as long as the features of the present invention are not impaired.

These optional components include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate,
Adhesive monomers such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, (meth) Alkyl (meth) acrylates such as tricyclo (5,2,1,0 ^2,6 ) decane acrylate, nonylphenoxyethyl (meth) acrylate, nonylphenol alkylene glycol (meth)
Monofunctional (meth) acrylates such as acrylates are exemplified.

As optional components, ethylene glycol di (meth) acrylate, triethylene di (meth) acrylate, polyethylene glycol di (meth) acrylate neopentyl di (meth), aliphatic urethane acrylate, aliphatic epoxy di (meth) acrylate, etc. Polyfunctional (meth) acrylates can also be used.

These optional components have a refractive index of 1.48 or more.
Since it is as low as about 1.55, there is a disadvantage that the refractive index of the adhesive is lowered, but since the optical distortion after curing is small, the adhesiveness of the adhesive of the present invention can be improved or the hardness can be adjusted. Use as necessary when adjusting chemical properties such as chemical resistance.

Further, the compound of the formula (1) of the present invention is liquid at normal temperature and has excellent compatibility with various compounds.
In relatively low-precision applications where the allowable range of optical distortion is wide, bisphenol-
Conventionally known compounds such as A-epoxydi (meth) acrylate and 4,4′-dimercaptodiphenylsulfide di (meth) acrylate can also be used in combination.

Also in this case, compared to the case where only a conventionally known compound is used, the stability of the liquid state of the adhesive is improved, the refractive index is increased, and the optical distortion after curing is reduced. The effect of the sulfur-containing di (meth) acrylate of the formula (1) of the present invention is imparted.

The adhesive of the present invention may contain a known silane coupling agent such as rimethoxyvinylsilane or γ- (meth) acryloxypropyltrimethoxysilane in order to increase the bonding strength or improve the bonding durability. It can also be added.

Next, the present invention will be described in more detail with reference to examples.

Example 1 As a compound represented by the formula (1) of the present invention, methacryloxy-2-hydroxypropyl-thiophenyl, in which R is a methyl group and X is 1, is a sulfur-containing monomethacrylate,
85 parts by weight of thiophenyl sulfide, R is a methyl group, X
A mixture of 15 parts by weight of bis (methacryloxy-2-hydroxypropyl-thiophenyl) sulfide, which is a sulfur-containing dimethacrylate having a molecular weight of 0, and 0.1 part by weight of azobisisobutyronitrile as a radical polymerization initiator, is a liquid adhesive at room temperature. The composition was prepared.

The adhesive composition was placed in a glass container, heated at 60 ° C. for 5 hours using a thermostat, and then cured by heating at 80 ° C. for 2 hours. A rectangular parallelepiped test piece having a width of 5 mm, a thickness of 5 mm, and a length of 10 mm was cut out from the cured product using a diamond cutter, and two orthogonal surfaces were polished to obtain a test piece for refractive index measurement.

When the refractive index of this test piece was measured using an Abbe refractometer, it had a high refractive index of 1.63.

Next, both ends were polished, and the diameter was 6 mm and the height was 10 mm.
A small amount of the adhesive of this example is applied to a cylindrical Pyrex glass test piece having a height of 25 mm and a diameter of 20 mm and a height of 25 mm, and then in the same manner as in the case of producing the above-described test piece for refractive index measurement. The test piece was adhered by heat treatment. When an adhesion test was performed on this adhesion test piece using a universal testing machine, the adhesion test piece had a compression-shear adhesive strength of 6.8 MPa (70 kgf / cm ² ).

Next, two 50 mm square low alkali glasses were opposed to each other with a 1 mm thick spacer interposed therebetween to form a glass cell.

The adhesive of this example was poured into the glass cell, and the adhesive was cured by heating under the same heating conditions as in the case of the refractive index measurement.

The test pieces thus obtained were placed between polarizing plates which were perpendicular to each other, and the test pieces were illuminated with a white fluorescent lamp from the back of one of the polarizing plates to observe the optical distortion of the test pieces.

The test piece made with the adhesive of this example was observed to be dark on the entire bonded surface, and it was confirmed that the optical distortion was extremely small.

The adhesive of this example was placed in a refrigerator at 4 ° C. for 1 hour.
After storage for months, no separation of liquid or precipitation of crystals occurred, and a stable liquid state was maintained.

Example 2 Methacryloxy-2 wherein R is a methyl group and X is 1 in the compound of formula (1) of the present invention.
Bis (methacryloxy-2), which is a sulfur-containing dimethacrylate in which 38 parts by weight of -hydroxypropyl-thiophenyl, 4-thiophenylsulfide, R is a methyl group, and X is 0
-Hydroxypropyl-thiophenyl) sulfide 12
By weight, 50 parts by weight of phenyl methacrylate and 0.5 part by weight of 1-hydroxycyclohexyl-phenyl ketone as a radical polymerization initiator were mixed to prepare a photopolymerizable adhesive of the present invention.

This adhesive was applied to Pyrex glass of the same size as that used in Example 1, and light was applied for 10 minutes using a 20 W ultraviolet fluorescent lamp (trade name: Chemical Lamp) manufactured by Toshiba Lighting & Technology Corporation. Irradiation was performed and light-cured.

The compressive shear adhesive strength of the thus obtained adhesive test piece was measured in the same manner as in Example 1, and the result was 5.7 MPa.
(58 kgf / cm ² ).

To determine the refractive index of the adhesive of this embodiment after curing, azobisisobutyronitrile, which is the thermal polymerization initiator used in Example 1, was added in an amount of 0.1% by weight.
The composition was heated and cured by the same method as described above to prepare a test piece for measuring the refractive index.

When the refractive index of this test piece was measured with an Abbe refractometer, it was 1.60.

Next, this adhesive was applied in the same manner as in Example 1 for 1 mm.
Was injected into a cell made of low alkali glass with a spacer interposed therebetween, and irradiated with light from a 20 W ultraviolet fluorescent lamp for 10 minutes to cure the adhesive.

The test piece was set between polarizing plates orthogonal to each other as in Example 1, and illuminated with a white fluorescent lamp.
It was found that the entire bonding surface was dark and the optical distortion was very small.

Further, this test piece was set in a spectrophotometer in which polarizing plates were arranged orthogonally on both sides of the sample chamber, and the light transmittance at a wavelength of 550 nm was measured.
A measurement result of 0.02% was obtained.

Next, the same measurement was carried out without setting the sample, and the light transmittance was 0.02% without change.

From the measurement results of the light transmittance, it was confirmed that the adhesive had very small optical distortion (birefringence) and hardly rotated the polarization axis of the measurement light as in the measurement in the empty state.

Comparative Example 1 In Example 2, the conventional (4) -dimercaptodiphenyl sulfide dimethacrylate was used instead of the sulfur-containing (meth) acrylate of the formula (1) of the present invention, and bisphenol- Two types of adhesive compositions using A-epoxy dimethacrylate were prepared.

This adhesive composition was photopolymerized in the same manner as in Example 2 to prepare a test piece for measuring optical strain, which was adhesively cured to a thickness of 1 mm between low alkali glasses.

When this test piece was sandwiched between orthogonal polarizing plates and illuminated with a white fluorescent lamp from the back of the polarizing plate, a large number of irregular light and dark patterns were observed on both test pieces.
Obviously, it was found that optical distortion occurred.

Subsequently, this test piece was set in a spectrophotometer provided with orthogonal polarizing plates as in Example 2, and the light transmittance at a wavelength of 550 nm was measured.

The light transmittance of the adhesive composition using 4,4'-bismercaptodiphenyl sulfide dimethacrylate is 0.76%, and that of the adhesive composition using bisphenol-A-epoxy dimethacrylate is 0.36%. Was the light transmittance.

From the results, it was quantitatively shown that the adhesive of Comparative Example 1 had optical distortion for rotating the polarization axis.

Next, 0.1% by weight of azobisisobutyronitrile was added to the adhesive composition prepared in Comparative Example 1, and the mixture was cured by heating in the same manner as in Examples 1 and 2 to measure the refractive index. Was prepared.

When the refractive index of this test piece was measured, it was 1.61 for the adhesive using 4,4′-dimercaptodiphenylsulfide dimethacrylate, and 1.61 for the adhesive using bisphenol-A-epoxydimethacrylate. A refractive index of 57 was shown.

From this fact, the refractive index of the adhesive of Comparative Example 1 is substantially the same as or lower than that of the adhesive of Example 1 or Example 2 according to the present invention, but the optical distortion is clearly inferior in performance. It has been found.

Example 3 In Example 2 of the present invention, 0.4 parts by weight of trimethylbenzoyldiphenylphosphine oxide and 0.05 parts by weight of camphorquinone were added in place of 1-cyclohexyl-phenylketone as a photopolymerization initiator. Thus, a high refractive index adhesive of the present invention was prepared.

This adhesive was applied to a test piece made of Pyrex glass in the same manner as in Example 2, and irradiated with light from a 20 W ultraviolet fluorescent lamp for 10 minutes.

When the adhesive strength of this test piece was measured,
7.7 MPa (79 kgf / cm ² ), and the adhesive strength was significantly increased by replacing the photopolymerization initiator with the type specified in the present invention.

Further, the adhesive prepared in Example 3 was applied to Pyrex glass and irradiated with light for 10 minutes using a 20 W visible light fluorescent lamp having a peak output at a wavelength of 420 nm instead of a 20 W ultraviolet fluorescent lamp. An adhesive test piece was prepared.

When the adhesion test of this test piece was carried out, a compressive shear adhesive strength of 9.6 MPa (98 kgf / cm 2) was obtained, which was about twice the result of Example 2 and was adhered using an ultraviolet fluorescent lamp. As a result, about 25% larger adhesive strength was obtained.

From the above, when the adhesive according to the present invention is used as a photopolymerizable adhesive, it is advantageous to use the photopolymerization initiator specified in the present invention, and the light source used for light irradiation is also short. It has been confirmed that even better adhesive properties can be obtained by using a long wavelength light source having an effective output up to the visible wavelength region.

Next, the adhesive of the present embodiment was injected into a cell made of low alkali glass according to the method of Embodiments 1 and 2, and irradiated with light for 10 minutes with the above-mentioned visible light fluorescent lamp to obtain an optical signal. Test pieces for strain measurement were prepared.

A test piece was set between orthogonal polarizing plates,
When illuminated with a white fluorescent lamp, it was confirmed that the adhesive surface was dark and the optical distortion of the adhesive was very small as in Examples 1 and 2, even when the adhesive was cured in a short time of 10 minutes.

Further, the present adhesive was injected between low alkali glass cells opposed to each other via a spacer having a thickness of 0.3 mm, and bonded by irradiating light with a 20 W visible light fluorescent lamp for 10 minutes. The test piece was colorless and transparent, and its light transmittance was measured by a spectrophotometer to find that the wavelength was 550 nm.
Was 91.4%.

Next, the sample was subjected to a light resistance test of continuously irradiating light with a metal halide lamp for illumination having an illuminance of 500,000 lux or more. After 500 hours, the sample was colorless and transparent, and the light transmittance at 550 nm was 90.
It was maintaining 7%.

From the results, it was confirmed that the adhesive according to the present invention had excellent light resistance.

Example 4 In the compound of the formula (1) of the present invention, 52 parts by weight of methacryloxy-2-hydroxypropyl-thiophenyl, 4-thiophenylsulfide wherein R is a methyl group and X is 1 is a sulfur-containing monomethacrylate; Is a methyl group and bis (methacryloxy-2-hydroxypropyl-thiophenyl) sulfide which is a sulfur-containing dimethacrylate wherein X is 0
10 parts by weight, 25 parts by weight of phenyl methacrylate as the Group A compound of the present invention, 0.5 parts by weight of trimethylbenzoyldiphenylphosphine oxide as a radical polymerization initiator of the present invention, 7 parts by weight of glycidyl methacrylate as an optional component, and hydroxyethyl An adhesive was prepared by blending 5 parts by weight of methacrylate and 1.5 parts by weight of triethoxyvinylsilane.

The Pyrex glasses were bonded to each other by irradiating them with a high pressure mercury lamp for 10 minutes using an adhesive, and the adhesive strength was measured. As a result, a compressive shear strength of 10.8 MPa (110 kgf / cm ² ) was obtained.

Next, the adhesive was poured into a cell made of low alkali glass in the same manner as in Example 1 and irradiated with light from a high-pressure mercury lamp for 10 minutes to prepare a test piece for measuring optical strain which was cured to a thickness of 1 mm. did.

When the test piece was set between orthogonal polarizing plates and illuminated with a white fluorescent lamp, no bright and dark stripes were observed on the adhesive surface, and it was confirmed that the optical distortion was very small.

In order to measure the refractive index of this adhesive,
Azobisisobutyronitrile was further added to the above composition at 0.1%.
After the addition by weight, polymerization was conducted by heating to prepare a test piece for measuring the refractive index. The measurement result of the refractive index by the Abbe refractometer was 1.60, indicating a high refractive index.

Example 5 In the compound of formula (1) of the present invention, 25 parts by weight of acryloxy-2-hydroxypropyl-thiophenyl, 4-thiophenylsulfide in which R is hydrogen and X is 1 is a sulfur-containing monoacrylate; Hydrogen, 5 parts by weight of bis (acryloxy-2-hydroxypropyl-thiophenyl) sulfide which is a sulfur-containing diacrylate in which X is 0, 50 parts by weight of phenyl methacrylate as a phenyl-containing (meth) acrylate represented by Group A of the present invention, 15 parts by weight of benzyl acrylate, bis (2,6-dimethoxybenzoyl) which is a diacylphosphine oxide represented by the following structural formula (2) as a radical polymerization initiator of the present invention
0.25 parts by weight of -2,4,4-drimethylpentylphosphine oxide, 2- (2) which is a conventionally known photopolymerization initiator
0.75 parts by weight of hydroxy-2-methyl-1-phenylpropan-1-one, 5 parts by weight of hydroxymethacrylate as an optional component, and 1.5 parts by weight of triethoxyvinylsilane were mixed to obtain an adhesive composition.

[0091]

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Using this adhesive, a 10-pressure mercury lamp was used.
For 2 minutes, and a Pyrex glass was adhered in the same manner as in Example 2, and the adhesive strength was measured.
A compression shear adhesive strength of (63 Kg / cm ² ) was obtained.

Next, the adhesive of this example was poured into a low-alkali glass cell via a 1 mm-thick spacer in the same manner as in Example 2, and the adhesive was cured by light irradiation with a high-pressure mercury lamp for 10 minutes. Was prepared. The obtained test piece was colorless and transparent.

When this test piece was set between polarizing plates orthogonal to each other and illuminated with a white fluorescent lamp, it was confirmed that the adhesion surface was dark and the optical distortion was small as in the other examples.

Further, in order to examine the refractive index of this adhesive,
A composition in which 0.1 parts by weight of azobishibutyronitrile was added to the adhesive was heated and polymerized, and machined to prepare a test piece.

The refractive index of this test piece was 1.58, indicating a high refractive index.

[0097]

As described above, the adhesive according to the present invention has high refractive index, excellent transparency, and extremely small optical distortion even when cured in a short time.

Since the compound of the formula (1) of the present invention is a liquid at room temperature, it does not crystallize due to disturbance such as a decrease in temperature or mechanical shock, and has a stable optical quality. It is also excellent in storage stability and workability of applying an adhesive.

The adhesive of the present invention can finely adjust the refractive index or change the viscosity within a high refractive index range by appropriately compounding the compound of Group A.

Further, when a specific photopolymerization initiator is used in the adhesive of the present invention, the photocuring characteristics of the adhesive are improved, and a better adhesive strength can be obtained.

Furthermore, despite the use of a photopolymerization initiator having light absorption in the long wavelength region of 380 nm or more, the adhesive after photocuring is colorless and transparent, and is exposed to strong light for 500 hours. It also has excellent light fastness, which hardly causes coloring or discoloration.

Such excellent performance is obtained by appropriately blending the compound of the formula (1) specified in the present invention, the compound of Group A and a specific photopolymerization initiator, and is unique to the present invention. The effect is.

Claims (4)

[Claims] An optical adhesive composition comprising at least one type of sulfur-containing epoxy (meth) acrylate represented by the following structural formula (1) and a radical polymerization initiator. Embedded image Here, R represents hydrogen or a methyl group, Ph represents a phenyl group, and the subscript x represents an integer of 0 or 1. 2. At least one sulfur-containing epoxy (meth) acrylate represented by the following structural formula (1), at least one phenyl group-containing (meth) acrylate selected from Group A below, and a radical polymerization initiator: An optical adhesive composition comprising: Embedded image Here, R represents hydrogen or a methyl group, Ph represents a phenyl group, and the subscript x represents an integer of 0 or 1. Group A Phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate 3. The method according to claim 1, wherein the radical polymerization initiator is at least one kind of photopolymerization initiator selected from acylphosphine oxide, bisacylphosphine oxide, and camphorquinone. An optical adhesive composition according to the above. 4. The method according to claim 2, wherein the radical polymerization initiator is at least one kind of photopolymerization initiator selected from acylphosphine oxide, bisacylphosphine oxide, and camphorquinone. An optical adhesive composition according to the above.