JPS6051770A - Optical adhesive - Google Patents

Abstract

PURPOSE:To provide an optical adhesive which has a low viscosity and can be quickly cured by irradiation with ultraviolet light, containing a bisphenol type epoxy compd. and/or a novolak type epoxy compd., a liquid alicyclic epoxy compd. and a photosensitive cationic polymn. catalyst as main components. CONSTITUTION:The titled optical adhesive contains a bisphenol type epoxy resin (e.g. bisphenol A diglycidyl ether) and/or a novolak type epoxy compd. (cresol novolak glycidyl ether) (A), a liquid alicyclic epoxy compd. (B) (e.g. 3,4-epoxy-6- methylcyclohexylmethyl) and a photosensitive cationic polymn. catalyst (C) (e.g. triphenylsulfonium hexafluorophosphate) as main components. Pref. the viscosity of component B is 500cP or below and that of the adhesive is 800cP or below.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical adhesive, particularly an optical adhesive having a low viscosity and a high refractive index.

BACKGROUND ART Conventionally, adhesives used for optical purposes such as lens assembling are generally desired to have good adhesion, ease of application, water resistance, heat resistance, weather resistance, and a high refractive index. to what is generally known.

Balsam (manufactured by Merck, etc.) is a thermosetting adhesive.

There are adhesives made of epoxy adhesives, polyester adhesives, polyvinyl acetate-allylsulfonamide, and formalin condensates. On the other hand, photo-curable adhesives include polyester-based adhesives (manufactured by Summers, USA (JV-69°71.74),
Thiol type (N0A-61, 63 manufactured by Norland, USA)
, 65, etc.), alkyl-based, epoxy-based, and acrylate-polythiol-based.

However, when using a thermosetting adhesive with a thickness of 10 μm or less, the curing progresses even during alignment (&U mounting, bonding) of lenses, etc., so alignment cannot be performed smoothly. On the other hand, if a resin is used that has a sufficiently long curing time compared to the alignment time, it will take a long time to harden after alignment is completed, which has the drawback of easily causing misalignment, and mass production effects cannot be expected. .

Thermosetting adhesives are widely used for bonding optical lenses, etc.1
Although it has strong adhesive strength, due to the above-mentioned disadvantages, it is unsuitable for fine or precise bonding, or bonding that requires mass production.

Therefore, in order to eliminate the above-mentioned disadvantages, it is desirable that, as a characteristic of the adhesive itself, curing does not proceed during alignment, and that it hardens as quickly as possible after alignment is completed.

An example of an adhesive having the above-mentioned characteristics is the ultraviolet curable adhesive described above.

However, to date, generally known UV-curable adhesives have low viscosity, high UV sensitivity, high transparency, and excellent weather resistance and solvent resistance.

Moreover, there was no adhesive with strong adhesive strength.

Liquid epoxy resins commonly used as adhesives have the following excellent properties. That is, it adheres well to materials with polar groups, such as glass, metals, ceramics, etc. In addition, the cohesive force of the adhesive itself is extremely high.
00% solid content, low shrinkage, high resistance to solvents and moisture, ability to be modified by blending with other resins, resistance over a wide temperature range, etc. It is.

In addition to these properties, epoxy resins are widely used as optical adhesives because of their high refractive index and high transparency. However, most of them are thermosetting adhesives and have various drawbacks in addition to being thermosetting adhesives. Amines, which are mainly used as hardening agents, have an odor and are irritating to the skin, and most of them are two-component adhesives, so they require thorough stirring during mixing.
There is a risk of making a mistake in the specified mixing ratio, and in addition, the pot life is short. There are other 1-liquid epoxy adhesives, but they have the disadvantage of short shelf life.

As mentioned above, even in the solid state, conventional mixtures of epoxy resin and curing agent react gradually at room temperature and do not have sufficient shelf life, and even when raised to high temperatures, the curing speed does not increase.
The essential drawback is that the cycle cannot be shortened.

The present invention solves the above-mentioned drawbacks by providing an adhesive that has a long shelf life, low viscosity, and cures and dries quickly under ultraviolet rays even though it is a liquid adhesive. Namely, the present invention uses a photosensitive cationic polymerization catalyst and a cationic photopolymerization initiator that decomposes with light and generates Lewis acid as a curing agent for an epoxy compound, thereby producing an optical adhesive that does not have the above-mentioned drawbacks. It is based on the fact that it can be obtained.

Furthermore, the low viscosity of the adhesive is important for various reasons such as making the adhesive layer thinner, preventing the inclusion of air bubbles, and improving workability. Alicyclic epoxy compounds generally have a low viscosity, are cured by ultraviolet irradiation in an extremely short period of time using a cationic photopolymerization initiator, and exhibit excellent weather resistance. On the other hand, bisphenol type or nobola 2 type epoxy compounds generally have high viscosity and high refractive index.

Therefore, in the present invention, an alicyclic epoxy compound (B) and a bisphenol type or novolac type epoxy compound (A) are used.
By mixing these and using a cationic photopolymerization initiator (C) as a curing agent, an adhesive with a low viscosity of 800 centivoise or less, excellent curing properties, and any refractive index up to a high refractive index can be obtained. agent can be made.

The photosensitive cationic polymerization catalyst (C) that can be used in the present invention, that is, the photopolymerization initiator, includes aromatic diazonium salts of Lewis acids such as boron trifluoride, aromatic iodonium salts of Lewis acids, phosphorus hexafluoride, etc. There are aromatic sulfonium salts of Lewis acids such as antimony hexafluoride. These photopolymerization initiators are cationic polymerization types, so unlike radical polymerization types such as UV curing of acrylates, they have the characteristic of curing and drying at high speed without being inhibited by oxygen in the air.

Among the above initiators, when the thickness of the adhesive layer exceeds 15 to 20μ, nitrogen gas bubbles are generated due to the decomposition of the diazonium salt, which remains in the adhesive layer. There are disadvantages and the disadvantage that the initiator turns yellow over time. On the other hand, aromatic sulfonium salts of Lewis acids do not have these drawbacks and are more excellent as optical adhesives.

Moreover, as an epoxy compound that can be used in the present invention, a bisphenol type epoxy compound (A) is used.

Bisphenol A diglycidyl ether, Bisphenol A diβ methylglycidyl ether, Bisphenol F
These include diglycidyl ether, tetrahydroxyphenylmethane tetraglycidyl ether, resorcinol diglycidyl ether, halogenated bisphenol A diglycidyl ether, and novolanc type epoxy compounds.
Examples of A) include phenol novolac glycidyl ether and cresol novolac glycidyl ether. As the alicyclic epoxy compound (B), compounds that are liquid at room temperature are used.9 For example, 3,4 epoxy-6 methylcyclohexylmethyl, 3,4 epoxy-6 methyl cyclohexane carboxylate, 3,4 epoxycyclohexyl methyl carboxylate. , bis(314-epoxy-6methylcyclohexylmethyl)adipate, vinylcyclohexene dieboxide, dicyclopentadiene oxide, bis(2,3-epoxycyclobentyl)
These include ether and limonene dioxide.

Among these epoxy compounds, bisphenol type and novolak type epoxy compounds have a high refractive index of 1.50 to 1°58, but they have high viscosity and are inferior in monoreactivity compared to alicyclic epoxy compounds. on the other hand.

The refractive index of the alicyclic epoxy compound is 1.47 to 1.50, which is somewhat low, but it has a low viscosity and high reactivity. Therefore, by mixing bisphenol-type or novolak-type epoxy compounds with alicyclic epoxy compounds, and if necessary, aliphatic epoxy resins, epoxidized dienes, carboxyl group-terminated epoxidized unsaturated fatty acid esters, etc. It is possible to obtain an adhesive that satisfies the qualities required for optical devices, such as viscosity, refractive index 5 reactivity, adhesive strength, and weather resistance.

The adhesive according to the present invention has a coating thickness ranging from several micrometers to several tens of micrometers, and has excellent adhesion to glass, metals, ceramics, and the like. Further, it is also possible to apply the coating using a conventional method such as a roll coater or a flow coater. Applications include glass and glass.

There are also adhesives between optically transparent materials such as glass and plastic, adhesives between optically transparent materials such as glass and metal or glass and ceramics, and other materials, and adhesion and fixing of electronic components. Specifically, bonding of camera lenses, bonding of cut glass, bonding of eyeglass lenses, manufacturing of glass for vanity tables, bonding of prisms, bonding of glass substrates and semiconductor parts, edge sealing of liquid crystal substrates, and connectors of optical fibers. This involves joining some parts.

Below, nine examples of the optical adhesive of the present invention will be described. In the examples, "parts" represent parts by weight.

Example 1 Preparation of UV-curable optical adhesive Bakelite ERL-4221 (3.4 epoxycyclohexyl methyl carboxylate manufactured by Union Carbide Japan) 57 parts Denacol EX-141 (phenyl glycidyl ether manufactured by Nagashio Sangyo +11) 15 parts Epicote 807 (Bisphenol F glycidyl ether manufactured by Yuka Shell Epoxy ■) 25 parts FC-508 (
1 rice! 3 parts (manufactured by 3M+1) of liphenylsulfonium hexafluorophosphate) The above composition was stirred and mixed with a mixer to obtain an optical adhesive. This adhesive was applied to a thickness of 10 μm on hard glass with a thickness of 1 mm, and then hard glass with the same thickness of 1 mm was placed on top of it, and ultraviolet rays were irradiated through the glass to harden it. Ultraviolet irradiation was performed using a high-pressure mercury lamp, ozone-free type 2KW (80W/cm) i-lamp,
It was cured by passing it once from the distance of the loan at an operating speed of 5 m/min. The viscosity of the adhesive is 200 centivoise (25°C), and the refractive index (50) is 1.518 before curing.
．． After curing, it was 1.544. Also, the light transmittance is 400
It was 99.2% at a film thickness of ~700 nm and 1100 cr.

Water resistance and weather resistance meet US military standards (MIL-A-3920).
0) were satisfied in all respects.

Example 2 Indirect Bakelite ERL-422157 part Denacol EX-14115 part DEN-431 (novolac glycidyl ether manufactured by Dow Chemical Japan 01) 25 parts 5P-55 (allyl diazonium trifluorocarbon manufactured by Asahi Denka Co., Ltd.) (rate) 3 parts The above composition was stirred and mixed with a mixer to obtain an optical adhesive.10 parts of this adhesive was placed on a 500 μm thick aluminum plate.
It was coated to a thickness of μm, a layer of 1 mm thick hard glass was placed on top of it, and ultraviolet rays were irradiated through the glass to cure it. Ultraviolet irradiation is performed using a high-pressure mercury lamp, ozone-free type 2KW (80W/am) i-light, and 5m/win from a distance of 10cm.
It was cured by one pass at an operating speed of . The viscosity of the adhesive is 270 centivoise (25°C) and the refractive index ('?'
L,) is 1.521 before curing. After curing, it was 1.546. Also, the light transmittance is 400-700nm, 100μm
The film thickness was 99.6%.

It satisfied all MIL-A-3920G requirements and had particularly excellent heat resistance.

Example 3 Preparation of UV-curable optical adhesive Bakelite ERL-422 150 parts Epikote 807 10 parts Denacol EX-14115 parts A-BPE-4 (2,2-bis(4-acryloyloxypolyethyleneoxyphenol manufactured by Nippon Kayaku ■) ))
20 parts Benzophenone 2 parts FC-5083 parts The above composition was stirred and mixed using a mixer to obtain an optical adhesive. This adhesive was applied to a thickness of 10 μm on a lead glass plate with a thickness of 511I11, a lead glass plate with the same thickness of 5IIlfl was placed on top of it, and ultraviolet rays were irradiated through the glass plate to cure it. High pressure mercury lamp ozone-less type 2KW (80
UV irradiation was performed using one W/c+n) lamp, and the film was cured by passing it once from a distance of 10 cm at an operating speed of 10+*/+nin. The curing speed is 2 times faster than the adhesives of Examples I and 2.
It was twice as fast and had excellent curing properties. Furthermore, the shrinkage rate is 2 to 3%, which is lower than that of general epoxy resins, which is 4 to 6%, and has excellent adhesive properties. The viscosity of the adhesive is 140 centivoise (25°C), the refractive index (pore p) is 1.511° before curing, and T1.537 after curing, and has characteristics that satisfy all MIL-A-3920C. Apuko.

Example 4 Preparation of UV-curable optical adhesive Bakelite ERL-422157 parts Denacol EX-14120 parts BP-4092 (brominated bisphenol A diglycidyl ether manufactured by Asahi Kakogyo 111) 20 parts 5P-5
53 parts The above composition was stirred and mixed using a mixer to obtain an optical adhesive. This adhesive was applied to a thickness of 10 μm on a stainless steel plate with a thickness of lllll11, then a soft glass plate with a thickness of 1 mm was layered on top of the adhesive, and ultraviolet rays were irradiated through the glass plate to harden the susceptor.

High pressure mercury lamp ozone-less type 2KW (80W/cm)
Ultraviolet irradiation was performed using a l lamp, and from a distance of 51
It was cured in one pass at an operating speed of 11/11 in. The refractive index ('rL;') is 1.507 before curing. 1.530 after curing, light transmittance is 400-700 r+m
.

It was 97.7% or more at a film thickness of 100 μm. MIL-
It satisfied the weather resistance test of A-3920C and had excellent heat resistance.

Example 5 Preparation of ultraviolet curable adhesive ERL-422156 part EX-141 14 parts DEN-43125 part BF-1000 (Nippon Petrochemical A1 epoxidized polybutadiene 5 parts FC-7508 3 parts The above composition was stirred with a mixer. An optical adhesive was obtained by mixing. A 10 μm layer of this adhesive was placed on a 1 mm thick nickel plate.
A thick layer of quartz glass was placed on top of the coating, and ultraviolet rays were irradiated through the glass to cure it. Ultraviolet irradiation was performed using one high-pressure mercury lamp, ozone-less type 2 KW (80W/cm), and the distance was 5 m from the distance of -Loan.
Cured by one pass at an operating speed of /min.

It satisfied all MIL-A-3920C requirements and had particularly excellent properties in terms of corrosion resistance and weather resistance.

Comparative Example I A polyester radical polymerization type adhesive (ultraviolet curable optical adhesive manufactured by Company A) was applied to a thickness of 10 μm on the same <1 mm thick hard glass plate as in Example 1, and a 1 mm thick
It was layered with thick hard glass and cured by irradiating ultraviolet light through the glass. When cured under the same ultraviolet irradiation conditions as in Example 1, it took 5 turns at an operating speed of 5 m/min, and the ultraviolet sensitivity of this adhesive was 11 times higher than that of the adhesive in Example 1.
It was 5. In addition, the cured sample was heated at 380°C.
When the adhesive layer was immersed in distilled water for 22 hours, the adhesive layer that was in direct contact with water turned white and the adhesive strength decreased. On the other hand, when the same sample was stored at -80℃ for 22 hours,
There was a crack of about 0.5 to 1 m. No changes occurred in the samples made with the adhesive of Example 1 in any of the tests.

Claims (1)

[Scope of Claims] 1. Optical use characterized by containing as main components a bisphenol type and/or novolac type epoxy compound (A), a liquid alicyclic epoxy compound (B), and a photosensitive cationic polymerization catalyst (C) glue. 2. The optical adhesive according to claim 1, wherein a liquid alicyclic epoxy compound (B) having a viscosity of 500 centivoise or less is used, and the viscosity of the adhesive is 800 centivoise or less. 3. The optical adhesive according to claim 1 or 2, wherein (C) is an aromatic sulfonium salt of a Lewis acid.