JP5697927B2 - Optical adhesive composition - Google Patents

Description

The present invention relates to an optical adhesive composition. More specifically, the present invention relates to an optical adhesive composition suitable for bonding optical members and parts in various optical devices and the like.

As an optical adhesive used for bonding optical components and members in optical equipment, etc., not only adhesive strength but also various performances required in optical applications such as durability and visible light transmission are required. ing. For example, adhesives used in display panels and backlight panels in display devices such as liquid crystal displays are not only light resistant and heat resistant, but also have high adhesive strength and adhesive layer (film) strength that do not peel off due to vibration or impact. Is required. In addition, when the adhesive itself is used as a light transmission medium that transmits light, it is necessary that the material is excellent in visible light transmission. The adhesive used as such a light transmission medium is also preferably a thin film from the viewpoint of suppressing light transmission loss. Even when it is a thin film, the adhesive can withstand vibrations and impacts, and is bonded by moisture or light. It is required to have durability that does not lower the force. In recent years, the demand for thinner and lighter optical members has increased, and as a component of display devices, the ratio of resin materials is increasing in place of conventional inorganic materials such as glass and metal. . For this reason, in consideration of the heat resistance of the member made of such a resin material, it can be cured by a curing method that does not require heating at a high temperature (for example, a photocuring method, a low temperature thermosetting method), and the above-mentioned There is an urgent need to develop an adhesive having excellent characteristics.

By the way, various epoxy resins can be used for sealing materials for optical elements such as LEDs (Light Emitting Diodes) to obtain cured products having excellent transparency, heat resistance, and strength. Compositions are being considered. For example, Patent Document 1 discloses an epoxy resin composition containing a specific alicyclic epoxy resin and an alicyclic epoxy resin obtained by nuclear hydrogenation of an aromatic epoxy resin. It is disclosed that acid anhydrides are mainly used as the curing agent.

JP 2008-101171 A

However, as described in Patent Document 1, in the curing method using an acid anhydride, a large amount of ester bonds are generated in the resin in the curing (polymerization) step, so that the resulting cured product has sufficient moisture resistance. There is a problem that it does not increase. As described above, the absence of a decrease in adhesive force due to moisture or the like is a very important performance required for optical adhesives, and the development of an adhesive capable of solving such problems is eagerly desired. Moreover, although the epoxy resin composition of patent document 1 aims at the solution of the subject of the prior art in uses, such as a sealing material of an optical element, it is suitable for a sealing material use in this way. Although an epoxy resin composition is known, an epoxy resin composition that can solve the problems peculiar to the optical adhesive application as described above is not known.
As described above, the prior art has room for improvement in order to obtain a resin composition that gives a cured product having various characteristics required for optical adhesive applications.

The present invention has been made in view of the above situation, and is an optical adhesive composition that can be cured under mild conditions and has excellent thin film formability and film thickness uniformity. -It aims at providing the adhesive composition for optics which can obtain the hardened | cured material (adhesion layer) which exhibits impact resistance and was excellent also in adhesive force, durability, and visible-light transmittance.

The present inventor has variously studied a resin composition (especially an epoxy resin composition) suitable for use in an optical adhesive, and the resin composition contains a component composed of an alicyclic epoxy compound having a specific structure. It can be cured under mild conditions (for example, photocuring method, low-temperature thermosetting method), and the resulting cured product (adhesive layer) is bonded to materials such as glass, polycarbonate, polyester, acrylic, and silicone used for optical members. I found out that it was excellent in power. Further, when the resin composition further contains a component composed of a specific polyfunctional hydrogenated epoxy compound and / or polyfunctional alicyclic epoxy compound, the cured product becomes moderately soft, and a thin film (for example, thick It has been found that even if it is used in the order of several μm to 30 μm, it has excellent vibration resistance and impact resistance. And by adjusting the blending ratio (mass ratio) of the above two components to a specific range, it was found that even if it was thinned, it was excellent in film thickness uniformity and could exhibit high thin film formability, durability, and adhesive layer strength. . Furthermore, the present inventor can adopt a cationic curing method as a curing method when the resin composition contains a cationic curing catalyst, and a large amount of ester in the curing step like the above-described curing method using an acid anhydride. Since it was possible to prevent the formation of bonds, it was found that the cured product has excellent moisture resistance. And the hardened | cured material obtained by the said resin composition also discovered that it was especially useful as a thin film adhesive used for the adhesion | attachment of the optical member in various optical apparatuses, such as a display apparatus, and can solve the said subject truly. The present invention has been reached.

（式中、Ｘ^１及びＸ^２は、同一若しくは異なって、置換基を有してもよいエポキシシクロヘキサン基を表す。Ｒ^１及びＲ^２は、同一若しくは異なって、炭素数１〜２０の２価の有機基を表す。ｍ及びｎは、同一若しくは異なって、０〜１０の整数を表す。）で表され、かつ、重量平均分子量が５００未満であり、上記成分（Ｂ）は、重量平均分子量が１０００以上であり、上記エポキシ化合物における成分（Ａ）と成分（Ｂ）との質量比は、６０／４０〜９５／５であることを特徴とする光学用接着剤組成物である。
本発明はまた、上記光学用接着剤組成物を硬化して得られる光学用接着層でもある。
以下に本発明を詳述する。 That is, the present invention is an optical adhesive composition comprising an epoxy compound and a cationic curing catalyst as essential components, the epoxy compound comprising a component (A) comprising an alicyclic epoxy compound and a polyfunctional hydrogenated epoxy compound. And / or the component (B) comprising a polyfunctional alicyclic epoxy compound, the component (A) is represented by the following general formula (1):

(In the formula, X ¹ and X ² are the same or different and represent an epoxycyclohexane group which may have a substituent. R ¹ and R ² are the same or different and are divalent having 1 to 20 carbon atoms. M and n are the same or different and each represents an integer of 0 to 10), and the weight average molecular weight is less than 500, and the component (B) has a weight average molecular weight. Is an optical adhesive composition characterized by having a mass ratio of component (A) to component (B) in the epoxy compound of 60/40 to 95/5.
The present invention is also an optical adhesive layer obtained by curing the above optical adhesive composition.
The present invention is described in detail below.

The optical adhesive composition of the present invention (hereinafter also simply referred to as an adhesive composition) contains component (A), component (B) and a cationic curing catalyst as essential components. As the component (A), the component (B) and the cationic curing catalyst, one type or two or more types can be used.

<Component (A)>
The optical adhesive composition of the present invention includes a component (A) composed of an alicyclic epoxy compound. And this component (A) is represented by the said General formula (1), and its weight average molecular weight is less than 500.
When the component (A) (alicyclic epoxy compound) is represented by the general formula (1), the cured product (adhesive layer) has excellent adhesive strength. This is presumed to be due to the presence of both an ether bond (for example, one derived from an epoxycyclohexane group) and an ester bond in the cured product, and the inclusion of a cyclohexane ring. Moreover, it can be made to contain more ether bonds compared with an ester bond in the principal chain skeleton of hardened | cured material, and durability, such as moisture resistance of a hardened | cured material, and light resistance, can be improved.
Moreover, when the weight average molecular weight of the said component (A) is less than 500, it can prevent that the viscosity of the said optical adhesive composition becomes high too much, and it becomes easy to form in a thin film form. The weight average molecular weight of the component (A) is preferably 50 or more and less than 450, more preferably 80 or more and less than 400.
The weight average molecular weight in the present specification can be measured by gel permeation chromatography (column: TSKgel SuperMultipore HZ-N 4.6 ^* 150, eluent: tetrahydrofuran, standard sample: TSK polystyrene standard).

In the general formula (1), X ¹ and X ² are the same or different and represent an epoxycyclohexane group which may have a substituent. The substituent is not particularly limited, but is preferably a hydrocarbon group. As the hydrocarbon group, an alkyl group, an aryl group, and an aralkyl group are preferable. The hydrocarbon group may be an unsubstituted group or a group in which one or more of the hydrogen atoms are substituted with another hydrocarbon group. Other hydrocarbon groups in this case include an alkyl group (when the hydrocarbon group is an alkyl group, the substituted hydrocarbon group as a whole corresponds to an unsubstituted alkyl group), an aryl group, Examples thereof include an aralkyl group and an alkenyl group.
The position of the epoxy group in the said epoxycyclohexane group is not limited, It can provide in arbitrary positions. Further, the position of the substituent in the form in which the epoxycyclohexane group has a substituent is not limited.

Also in the above general formula (1), ^{R 1} and ^{R 2} are the same or different, represent a divalent organic group having 1 to 20 carbon atoms. The organic group is not limited as long as it has 1 to 20 carbon atoms as a whole, and examples thereof include an aliphatic hydrocarbon group and an organic group containing an aliphatic hydrocarbon. Examples of the organic group containing an aliphatic hydrocarbon include a non-hydrocarbon moiety such as an ether bond (—O—) and an ester bond (—O—C (═O) —) in the structure, and an aliphatic hydrocarbon. An organic group having The aliphatic hydrocarbon includes both those having a chain structure and those having a cyclic structure.
The organic group is preferably an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and more preferably an aliphatic hydrocarbon group having 1 to 10 carbon atoms.

Moreover, in the said General formula (1), m and n are the same or different and represent the integer of 0-10. m and n are not particularly limited as long as they are within the above range, but when either one of m and n is 0, the other is preferably 1 or more. That is, it is preferable that m + n ≧ 1.

Specifically, as the component (A), for example, alicyclic epoxy compounds represented by the following general formulas (2-1) to (2-5) are preferable. A form in which the component (A) is at least one compound selected from the group consisting of these compounds is also a preferred form of the present invention.

上記一般式（２−４）において、ｐは１〜３の整数を表す。

In the general formula (2-4), p represents an integer of 1 to 3.

As the component (A), in particular, as in the general formulas (2-1) to (2-4), the form in which the ester group is directly bonded to the cyclohexane ring, that is, in the general formula (1), m = The form which is 0 is more preferable. With such a form, the resulting cured product is excellent in durability. Particularly preferred is a compound represented by formula (2-1).

<Component (B)>
The optical adhesive composition of the present invention also contains a component (B) comprising a polyfunctional hydrogenated epoxy compound and / or a polyfunctional alicyclic epoxy compound. The component (B) has a weight average molecular weight of 1000 or more. When the adhesive composition contains such a component, the obtained cured product (adhesive layer) becomes moderately soft, and even when the cured product is formed into a thin film,・ Excellent impact resistance. The weight average molecular weight of the component (B) is preferably 1500 or more and less than 8000, and more preferably 2000 or more and less than 6000.

The polyfunctional hydrogenated epoxy compound is a hydrogenated epoxy compound having an average of two or more epoxy groups in one molecule. Such a hydrogenated epoxy compound is preferably a polyfunctional glycidyl ether compound having an average of two or more glycidyl ether groups bonded directly or indirectly to a saturated aliphatic cyclic hydrocarbon skeleton. Such a hydrogenated epoxy compound is preferably a complete or partial hydrogenated product of an aromatic polyfunctional epoxy compound, and more preferably a hydrogenated product of an aromatic polyfunctional glycidyl ether compound. Specifically, a hydrogenated bisphenol A type epoxy compound represented by the following general formula (3-1) and a hydrogenated bisphenol F type epoxy compound represented by the following general formula (3-2) are preferable. When the component (B) is a hydrogenated bisphenol A type epoxy compound and / or a hydrogenated bisphenol F type epoxy compound, the cured product (adhesive layer) becomes more flexible, and even if it is a thin film, It will be more excellent in impact resistance.
In general formulas (3-1) and (3-2), some hydrogen atoms of hydrocarbons such as a cyclohexyl ring and a methylene chain may be substituted. As the substituent, a halogen atom such as fluorine, chlorine and bromine, a hydrocarbon group which may have a substituent, and the like are preferable. Among the hydrocarbon groups, an alkyl group is preferable, and a methyl group and an ethyl group are more preferable.

式中、ｑは１以上の整数を表す。

In the formula, q represents an integer of 1 or more.

In the case where the component (B) is a hydrogenated bisphenol A type epoxy compound and / or a hydrogenated bisphenol F type epoxy compound, the hydrogenation rate of the epoxy compound is preferably greater than 95%. When the hydrogenation rate is greater than 95%, the aromatic cyclic structure contained in the component (B) is sufficiently reduced, so that coloring (yellowing) due to heat and light of the obtained cured product can be sufficiently suppressed. . More preferably, the hydrogenation rate is greater than 98%, and still more preferably, the hydrogenation rate is 100%.

Specific examples of the hydrogenated bisphenol A type epoxy compound include those obtained by hydrogenating a bisphenol A type epoxy compound, such as YX-8040 (manufactured by Mitsubishi Chemical Corporation), ST-4000D. (Manufactured by Nippon Steel Chemical Co., Ltd.).
As the hydrogenated bisphenol F-type epoxy compound, specifically, those obtained by hydrogenating a bisphenol F-type epoxy compound can be used.
In addition, in this specification, the compound etc. in which the manufacture or sales company name was shown shall represent a brand name.

The polyfunctional alicyclic epoxy compound is a compound having an average of two or more alicyclic epoxy groups in one molecule. Examples of the alicyclic epoxy group include an epoxycyclohexane group (epoxycyclohexane skeleton), an epoxy group added to a cyclic aliphatic hydrocarbon directly or via a hydrocarbon, and the like. Among these, a compound having an epoxycyclohexane group is preferable. Specifically, as the polyfunctional alicyclic epoxy compound, for example, a compound represented by the following general formula (4-1), EHPE3150 (manufactured by Daicel Chemical Industries, Ltd.) and the like are preferable.

式中、ｒは６以上の整数を表す。

In the formula, r represents an integer of 6 or more.

In addition, since the alicyclic epoxy compound as said component (A) also has a some alicyclic epoxy group, it is "polyfunctional". However, in this invention, component (A) and component (B The component (A) is referred to as “alicyclic epoxy compound”, and the component (B) is referred to as “polyfunctional hydrogenated epoxy compound and / or polyfunctional alicyclic epoxy compound”. The names are distinguished from each other.

The component (B) also preferably has an epoxy equivalent of 500 or more. Thereby, the cured product (adhesive layer) becomes more excellent in softness, and even in the case of a thin film, it becomes more excellent in vibration resistance and impact resistance. More preferably, the epoxy equivalent is 800 or more. The epoxy equivalent is preferably 4000 or less. More preferably, it is 2000 or less.

The components (A) and (B) may contain an aromatic ring in the structure as long as they do not impair the light resistance and heat resistance of the cured product (adhesive layer). In that case, as content of an aromatic ring, when the total amount of said each component (A) and (B) is 100 mass%, the mass ratio of the aromatic ring contained in the said structure may be 20 mass% or less. preferable. More preferably, it is 10 mass% or less, More preferably, it is 5 mass%, Most preferably, it is 0 mass%, ie, it does not contain an aromatic ring.

<Combination ratio of component (A) and component (B)>
The compounding ratio of the said component (A) and a component (B) is 60 / 40-95 / 5 by mass ratio (component (A) / component (B)). By adjusting the compounding ratio in such a range, the cured product (adhesive layer) obtained has excellent film thickness uniformity even when it is thinned, and exhibits high thin film formability, durability, and adhesive layer strength. It will be a thing. The mass ratio is preferably 65/35 or more, and more preferably 71/29 or more. Thereby, hardened | cured material becomes a thing which was further excellent in heat-and-moisture resistance and film thickness uniformity. The mass ratio is preferably 90/10 or less, and more preferably 85/15 or less. Thereby, hardened | cured material becomes a thing further excellent in impact resistance.

<Cation curing catalyst>
The optical adhesive composition of the present invention also contains a cationic curing catalyst. The cationic curing catalyst is not particularly limited as long as it is a compound capable of generating a cationic species that initiates polymerization by photoexcitation or heat, but is preferably a photocation curing catalyst or a thermal cation curing catalyst. By using a photocationic curing catalyst, a compound containing a cationic species is excited by light, a photodecomposition reaction occurs, and photocuring proceeds. In addition, by using a thermal cation curing catalyst, a compound containing a cation species is excited by heating, a thermal decomposition reaction occurs, and thermal curing proceeds. Among these, it is more preferable to use a photocation curing catalyst for the following reasons. That is, in the thermosetting, in the cooling process after curing, stress is generated due to the difference in shrinkage due to the difference in thermal expansion coefficient between the adhesive layer (cured product) and the adherend, and the warpage of the adherend, Depending on the material, it may cause cracking. Such a problem becomes particularly prominent when the adhesive layer is relatively thick, or when the adherend is large or thin. Specifically, the above problem becomes particularly noticeable when a large-sized protective glass or thin-film glass for a display whose size is increased and a display portion is thin is an adherend. On the other hand, such a problem does not occur in photocuring that does not require heating and cooling. Also, in heat curing, compared to the coating film of the adhesive composition, there is a problem that the film area of the cured film is increased or the film thickness is reduced. Is suppressed. In particular, when the adherend is a large glass, the difference becomes significant.
Thus, the form in which the cation curing catalyst is a photocationic curing catalyst is one of the preferred forms of the present invention.

The photocationic curing catalyst is also called a photocationic polymerization initiator, and exhibits a substantial function as a curing agent when irradiated with light.
Examples of the photocation curing catalyst include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p- (phenylthio) phenyldiphenylsulfonium hexafluoroantimonate, p- (phenylthio) phenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluoroantimonate, bis [4- (diphenylsulfonio) phenyl] sulfide bishexafluorophosphate, bis [4- (diphenylsulfonio) phenyl Sulfide bishexafluoroantimonate, (2,4-cyclopentadien-1-yl) [(1 Methylethyl) benzene] -Fe- hexafluorophosphate, diaryliodonium hexafluoroantimonate and the like.

Specific examples of the above-mentioned photocationic curing catalyst include UVI-6950, UVI-6970, UVI-6974, UVI-6990 (manufactured by Union Carbide); Adekaoptomer SP-150, SP-151, SP- 170, SP-172 (manufactured by ADEKA); Irgacure 250 (manufactured by Ciba Japan); CI-2481, CI-2624, CI-2623, CI-2064 (manufactured by Nippon Soda); CD-1010, CD-1011, CD-1012 (manufactured by Sartomer); DTS-102, DTS-103, NAT-103, NDS-103, TPS-103, MDS-103, MPI-103, BBI-103 (manufactured by Midori Chemical); PCI-061T , PCI-062T, PCI-020T, PCI-022T (manufactured by Nippon Kayaku Co., Ltd.) CPI-100P, CPI-101A, CPI-200K (manufactured by Sun Apro); Sun-Aid SI-60L, Sun-Aid SI-80L, Sun-Aid SI-100L, Sun-Aid SI-110L, Sun-Aid SI-145, Sun-Aid SI-150, Sun-Aid SI- Diazonium salt type, iodonium salt type, and sulfonium salt type such as 160, Sun-Aid SI-180L (manufactured by Sanshin Chemical Industry Co., Ltd.); WPAG series (manufactured by Wako Pure Chemical Industries, Ltd.) are preferred.

The thermal cation curing catalyst is also called a thermal acid generator, a thermal curing agent, a thermal cation generator, or a cationic polymerization initiator, and exhibits a substantial function as a curing agent when the curing temperature is reached in the adhesive composition. Is.
Examples of the thermal cation curing catalyst include the following general formula (5):
_{^{(R 3 a R 4 b R}} 5 c R 6 d Z) + s (AXt) -s (5)
(Wherein, Z represents at least one element selected from the group consisting of S, Se, Te, P, As, Sb, Bi, O, N and halogen elements. R ³ , R ⁴ , R ⁵ and R ⁶ is the same or different and represents an organic group, a, b, c and d are 0 or a positive number, and the sum of a, b, c and d is equal to the valence of Z. Cation (R ³ _a R ⁴ _b R ⁵ _c R ⁶ _d Z) ^{+ s} represents an onium salt, A represents a metal element or a metalloid which is a central atom of a halide complex, B, P, As, Sb, And at least one selected from the group consisting of Al, Ca, In, Ti, Zn, Sc, V, Cr, Mn, and Co. X represents a halogen element, and s is a net charge of a halide complex ion. T is a halogen element in a halide complex ion The compound represented by this is preferred.

Specific examples of the anion (AXt) ^-s of the general formula (5) include tetrafluoroborate (BF ⁴⁻ ), hexafluorophosphate (PF ⁶⁻ ), hexafluoroantimonate (SbF ⁶⁻ ), hexafluoro arsenates ^{(AsF 6-),} hexachloroantimonate (SbCl ^6-), and the like.
Further formula AXt (OH) ^- anions may be used which is represented by. Other anions include perchlorate ion (ClO ₄ ⁻ ), trifluoromethyl sulfite ion (CF ₃ SO ₃ ⁻ ), fluorosulfonate ion (FSO ₃ ⁻ ), toluenesulfonate ion, and trinitrobenzenesulfone. An acid ion etc. are mentioned.

As the thermal cation curing catalyst, those capable of exhibiting a function as a curing agent at a relatively low temperature are suitable. Specifically, those that can be cured at 140 ° C. or lower are preferred. Thereby, while being able to suppress the curvature and the crack of a to-be-adhered body resulting from the difference in shrinkage | contraction rate of hardened | cured material and a to-be-adhered body, a to-be-adhered body has low heat resistance compared with inorganic materials, such as glass. Even if it consists of a resin material, the influence on the adherend due to heating in the thermosetting step can be reduced. More preferably, it functions as a curing agent at 120 ° C. or lower.

Specific examples of the thermal cation curing catalyst include diazonium salt types such as AMERICURE series (American Can), ULTRASET series (Adeka), and WPAG series (Wako Pure Chemical Industries); UVE Iodonium salt types such as series (manufactured by General Electric), FC series (manufactured by 3M), UV9310C (manufactured by GE Toshiba Silicone), Photoinitiator 2074 (manufactured by Rhone-Poulenc), WPI series (manufactured by Wako Pure Chemical Industries, Ltd.) CYRACURE series (manufactured by Union Carbide), UVI series (manufactured by General Electric), FC series (manufactured by 3M), CD series (manufactured by Sartomer), optomer SP series / optomer CP series (manufactured by Adeka) Aid SI series (Sanshin Chemical Industry Co., Ltd.), CI series (manufactured by Nippon Soda Co., Ltd.), WPAG series (manufactured by Wako Pure Chemical Industries, Ltd.), CPI series (manufactured by San-Apro Ltd.) sulfonium salt type or the like, and the like. Among these, a sulfonium salt type is preferable in that it can be cured at a relatively low temperature.

In the optical adhesive composition, the content of the cationic curing catalyst is 100% by mass of the total amount of the component (A) and the component (B) as a non-volatile equivalent amount as an effective component amount not including a solvent or the like. The content is preferably 0.01 to 10% by mass. By setting the content of the cationic curing catalyst in such a range, it is possible to sufficiently increase the curing rate and to more sufficiently suppress coloring of the cured product at the time of curing or in the use environment. The content of the cationic curing catalyst is more preferably 0.05 to 5% by mass. More preferably, it is 0.1-3 mass%.

<Other ingredients>
The optical adhesive composition of the present invention may contain other components as long as the component (A), the component (B), and the cationic curing catalyst are essential components. More than seeds can be used. Examples of other components include solvent components, other polymerization components (epoxy resins, oxetane resins, vinyl monomers, etc.), polymer components, various additives, and the like.

The solvent can be included as necessary for the purpose of adjusting the viscosity of the composition. The solvent is not particularly limited and can be used as long as it is a conventionally known organic solvent, but a solvent that dissolves the components (A) and (B) described above is preferable. For example, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; hydrocarbons such as toluene and xylene; alcohols such as butanol and 2-ethylhexyl alcohol; ethylene glycol, diethylene glycol, (di) ethylene glycol methyl ether, (di) Glycols such as ethylene glycol ethyl ether, (di) ethylene glycol acetate, (di) ethylene glycol diacetate, (di) ethylene glycol methyl ether acetate, propylene glycol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate And derivatives thereof (ether, ester); esters such as ethyl acetate and butyl acetate are preferred.
The solvent may cause bubbles in the adhesive layer when the adhesive composition is cured to form an adhesive layer, and may cause a decrease in adhesive force, a decrease in light transmission property, and a permeability. Moreover, if it is used in a large amount, the viscosity of the composition becomes too low, which causes a decrease in the film thickness and shape controllability of the molded body. Therefore, when using a solvent, 30 mass% or less is preferable with respect to 100 mass% of the total amount of the said adhesive composition, More preferably, it is 15 mass% or less, More preferably, it is 10 mass% or less, More preferably, it is 5 mass%. Hereinafter, it is more preferably 1% by mass or less. Especially preferably, it is 0.1 mass% or less, Most preferably, it is 0 mass%, ie, it is not using a solvent.
In particular, in the case of photocuring, it is preferable not to use a solvent or to use a trace amount even if it is used.

The adhesive composition of the present invention contains components (A) and (B) as essential components as polymerization components, but the adhesive layer obtained from the above composition has features such as adhesive strength and impact resistance. In order to make it excellent, the total content of the component (A) and the component (B) contained in the composition is 80% by mass or more with respect to 100% by mass of the total amount of the polymerization components. preferable. More preferably, it is 90 mass% or more, More preferably, it is 95 mass% or more, Most preferably, it is 99 mass% or more.

Additives include inorganic fine particles, reactive diluents, saturated compounds without unsaturated bonds, pigments, dyes, antioxidants, UV absorbers, light stabilizers, plasticizers, non-reactive compounds, chain transfer agents , Thermal polymerization initiator, anaerobic polymerization initiator, polymerization inhibitor, adhesion improver such as inorganic filler and organic filler, coupling agent, heat stabilizer, antibacterial / antifungal agent, flame retardant, matting agent, Antifoaming agent, leveling agent, wetting / dispersing agent, anti-settling agent, thickener / anti-sagging agent, anti-coloring agent, emulsifier, anti-slip / scratch agent, anti-skinning agent, desiccant, antifouling agent, electrification An inhibitor, a conductive agent (electrostatic aid) and the like may be contained.

<Physical properties of optical adhesive composition>
The optical adhesive composition of the present invention preferably has a viscosity at 25 ° C. of 100 to 100,000 mPa · s. When the viscosity is in such a range, the adhesive composition is easily applied in a thin film. More preferably, it is 500-50000 mPa * s.
The viscosity of the adhesive composition can be measured using an R / S rheometer (manufactured by Brookfield) under the condition of a temperature of 25 ° C.

<Adhesive layer (cured product)>
An adhesive layer (cured product) can be obtained by curing the optical adhesive composition of the present invention. As the curing method, as described above, it is preferable to employ photocuring or thermosetting. Among them, in terms of preventing warpage and cracking of the adherend due to the difference in shrinkage between the cured product and the adherend, and suppressing changes in the film area and film thickness before and after the curing reaction. It is more preferable to employ photocuring.

The adhesive layer is preferably formed in a thin film shape. Specifically, the thickness is preferably 1 to 80 μm. Accordingly, the adhesive layer can have a small light transmission loss, and can be suitably used as a light transmission medium (light transmission medium) that transmits light. A more preferred lower limit is 5 μm or more. The upper limit is more preferably 60 μm or less, and still more preferably 50 μm or less.

The adhesive layer preferably has a visible light transmittance of 80% or more. Specifically, the parallel line transmittance at 400 nm is preferably 80% or more. As a result, it is possible to achieve high light transparency and transparency that are required particularly in applications to optical transmission bodies. The parallel line transmittance at 400 nm is more preferably 85% or more, and still more preferably 90% or more.
The transmittance can be measured using a sample having a thickness of 500 μm with a UV-VIS spectrophotometer (Agilent 8453, manufactured by Agilent Technologies).

Since the adhesive layer has high visible light permeability, it can be suitably applied to optical applications. Thus, an optical adhesive layer obtained by curing the optical adhesive composition is also one aspect of the present invention and is suitably used as an optical bonding material. The adhesive layer is also excellent in adhesiveness and heat-and-moisture resistance, and exhibits excellent impact resistance even in the case of a thin film. Therefore, the adhesive layer is particularly used for bonding optical members in various optical devices such as display devices. It is extremely useful as a thin film adhesive or the like. Among these, it is more preferable to use the light transmission medium (light transmission medium) that directly transmits light. Thus, it is one of the preferred embodiments of the present invention that the optical adhesive layer is an optical transmission medium adhesive layer and an optical transmission medium bonding material. As described above, since the adhesive layer is excellent in visible light transmission and impact resistance, when used as an optical transmission medium, the bonding between the display panel and the protection panel in the display device, and the light source in the backlight. And can be suitably used for joining the light guide plate and the like. An optical transmission body (or optical transmission material) in which a transparent medium is bonded via the optical adhesive layer or bonding material is also one aspect of the present invention.
The bonding material means a material having at least one surface made of the adhesive layer of the present invention. For example, in the form (1) constituted only by the adhesive layer of the present invention, the adhesive layer is formed on both surfaces of the transparent substrate. A mode (2) in which at least one adhesive layer is formed of the adhesive layer of the present invention is exemplified. In the case of the form (2), a form in which both surfaces are composed of the adhesive layer of the present invention is preferable. As the transparent substrate, for example, resin sheets (including film, plate, tape, etc.) such as acrylic resin, polycarbonate resin, polyester resin, and polyolefin resin, and glass sheets are preferably used. As a transparent base material when used as a bonding material for an optical transmission medium, a resin sheet is preferable from the viewpoint of excellent vibration resistance and impact resistance.

Since the optical adhesive composition of the present invention has the above-described configuration, it can be cured under mild conditions and has excellent thin film formability and film thickness uniformity. The above adhesive composition exhibits excellent vibration resistance and impact resistance even in a thin film, and also has a cured product with excellent adhesive strength, durability (moisture resistance, light resistance, etc.) and visible light transmission ( It is possible to obtain an adhesive layer. Further, such a cured product (adhesive layer) is extremely useful as a thin film adhesive (optical adhesive layer) used for bonding optical members in various optical devices such as display devices.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “% by mass”.

<Preparation of adhesive composition>
Preparation Example 1
62 parts of Celoxide 2021P (manufactured by Daicel Chemical Industries) and 38 parts of YX-8040 (manufactured by Mitsubishi Chemical Corporation) were weighed into a separable flask equipped with a stirrer, heated to 140 ° C. in a nitrogen atmosphere, and mixed for 1 hour. After cooling to room temperature, 1 part of CPI-101A (manufactured by San Apro) was added and mixed for 1 hour in the dark to obtain an adhesive composition (1).

Preparation Examples 2-10, Comparative Preparation Examples 1-4
Adhesive composition (2), respectively, in the same manner as in Preparation Example 1, except that component (A), component (B), curing agent, and if necessary, a curing accelerator are mixed in the proportions shown in Table 1. To (10), adhesive compositions (Comparative 1) to (Comparative 4) were obtained.

<Creation and evaluation of adhesive layer>
Examples 3-8, Reference Examples 1, 2, 9, 10 and Comparative Examples 1-4
Sample preparation method shown below using adhesive compositions (1) to (10) and adhesive compositions (Comparative 1) to (Comparative 4) obtained in Preparation Examples 1 to 10 and Comparative Preparation Examples 1 to 4 Thus, samples (adhesive layer samples) each having an adhesive layer formed thereon were prepared. About the obtained adhesive layer sample, the adhesive layer film thickness, adhesiveness, moist heat resistance, impact resistance and film thickness uniformity were measured and evaluated by the methods described later. The results are shown in Table 1.

Sample preparation method 1
After apply | coating an adhesive composition to a glass plate (A), it pinched | interposed with the other glass plate (B), and it hardened | cured on the conditions shown below. In photocuring, UV was irradiated from the glass plate (B) side.
(Curing conditions)
Photocuring (Examples 3-7, Reference Examples 1 , 2 , 9, 10, Comparative Examples 1-3): UV irradiation (high pressure mercury lamp, manufactured by Ushio Inc., peak wavelength 365 nm, irradiation amount 500 mJ / cm ² ) And cured.
Thermosetting (Example 8, Comparative Example 4): In Example 8, curing was performed by heating at 120 ° C. for 15 minutes. In Comparative Example 4, it was cured by heating at 150 ° C. for 2 hours.

Sample preparation method 2
The adhesive composition was applied to the glass plate (A) using an applicator and cured under the above-described curing conditions.

<Adhesive layer thickness>
The adhesive layer sample prepared by the sample preparation method 1 was evaluated. The gap between the glass plate (A) and the glass plate (B) sandwiching the adhesive layer was defined as the film thickness. That is, the total thickness of the adhesive layer sample and the thickness of the glass plates (A) and (B) are measured, and the value obtained by subtracting the thickness of the glass plates (A) and (B) from the total thickness is the adhesive layer film. Thickness. The film thickness was measured with a micrometer (Digital Micrometer MDC-25MJ, manufactured by Mitutoyo Corporation).

<Adhesiveness>
The adhesive layer sample prepared by the sample preparation method 1 was evaluated. The state of the sample when the cutter blade was pushed in between the glass plates of the adhesive layer sample was evaluated according to the following criteria. Moreover, the case where the film thickness of the contact bonding layer in a contact bonding layer sample is 10 micrometers and 40 micrometers was evaluated.
A: The adhesive layer does not peel off until the glass breaks.
B: Although it does not peel off even if a blade is put at the end of the sample, it peels off before the glass breaks.
C: The adhesive layer is easily peeled off simply by inserting a blade at the end of the sample.

<Heat and heat resistance>
The adhesive layer sample prepared by the sample preparation method 2 was evaluated. The adhesive layer sample was subjected to a moisture and heat resistance test in which the sample was left in a constant temperature and humidity atmosphere at a temperature of 85 ° C. and a relative humidity of 85% for 1000 hours, and the presence or degree of coloring after the test was evaluated. Specifically, the transmittance change rate (ΔT) with respect to 400 nm light before and after the test was measured and evaluated according to the following criteria. The transmittance was measured with a UV-VIS spectrophotometer (Agilent 8453, manufactured by Agilent Technologies). The film thickness of the adhesive layer in the adhesive layer sample was 100 μm.
A: ΔT <5%
B: 5% ≦ ΔT <10%
C: ΔT ≧ 10%

<Resin strength>
The adhesive layer sample prepared by the sample preparation method 1 was evaluated. Bending strength was evaluated as a measure of the brittleness of the adhesive layer. Specifically, a resin plate of (thickness) 1 mm × (width) 5 mm × (length) 30 mm is prepared, and a dynamic viscoelasticity measuring device (RSA-III, manufactured by T.A. Instruments Inc.) is used. A bending test was performed. A sample was placed on a support jig with an interval of 25 mm, and the displacement until it was cracked by being displaced at a speed of 0.1 mm per second in a three-point bending mode was measured and evaluated according to the following criteria.
○: No cracking even when pressed and bent by 5 mm Δ: Cracked by 3 mm or more and less than 5 mm ×: Cracked by less than 3 mm

<Thickness uniformity>
For the adhesive layer sample prepared by Sample Preparation Method 2, the film thickness was measured at five points on the sample. Variation in the measured value of the film thickness (difference between the maximum value and the minimum value) was calculated and evaluated according to the following criteria. The film thickness of the adhesive layer in the adhesive layer sample was 100 μm. The film thickness was measured with a micrometer (Digimatic Micrometer MDC-25MJ, manufactured by Mitutoyo Corporation).
○: Variation is less than 10 μm (the adhesive layer surface is smooth and the film thickness is uniform)
X: Variation is 10 μm or more (thickness variation is recognized)

The adhesive layer sample (film thickness: 100 μm) prepared from the composition of each example by the sample preparation method 1 was measured for parallel line transmittance with respect to 400 nm light. As a result, in all examples, it was 85% or more. It was. The transmittance measurement was performed with the apparatus described above.

Each compound in Table 1 is as follows.
ST-4000D: manufactured by Nippon Steel Chemical Co., Ltd., solid hydrogenated bisphenol A type epoxy resin EHPE3150: manufactured by Daicel Chemical Industries, Ltd., solid polyfunctional alicyclic epoxy resin

From the results shown in Table 1, in the examples using the adhesive composition corresponding to the present invention (Examples 3 to 8, Reference Examples 1 , 2 , 9 , and 10 ), the adhesive layers obtained are all adhesive and resistant. It turns out that it is excellent in all of impact property, heat-and-moisture resistance, and film thickness uniformity. On the other hand, examples in which the blending ratio of component (A) and component (B) is outside the scope of the present invention (Comparative Examples 1 and 2) and examples in which component (A) is a monofunctional alicyclic epoxy compound ( In Comparative Example 3) and the example employing the curing method using an acid anhydride (Comparative Example 4), an adhesive layer excellent in all of the above-described properties has not been obtained.
In Example 8 adopting thermosetting, when cured under the same conditions as in the above film thickness uniformity test, the film area after curing becomes larger than when the adhesive composition is applied, It was confirmed that the phenomenon decreased.

Claims (5)

An optical adhesive composition comprising an epoxy compound and a cationic curing catalyst as essential components,
The epoxy compound includes a component (A) composed of an alicyclic epoxy compound, and a component (B) composed of a polyfunctional hydrogenated epoxy compound and / or a polyfunctional alicyclic epoxy compound,
The component (A) is represented by the following general formula (1):

(In the formula, X ¹ and X ² are the same or different and represent an epoxycyclohexane group which may have a substituent. R ¹ and R ² are the same or different and are divalent having 1 to 20 carbon atoms. M and n are the same or different and each represents an integer of 0 to 10), and the weight average molecular weight is less than 500;
The component (B) is a hydrogenated bisphenol A type epoxy compound and / or a hydrogenated bisphenol F type epoxy compound, the hydrogenation rate is greater than 95%, and the weight average molecular weight is 1000 or more.
The optical adhesive composition, wherein the mass ratio of the component (A) to the component (B) in the epoxy compound is 71/29 to 90/10 . The optical adhesive composition according to claim 1, wherein the component (B) further has an epoxy equivalent of 500 or more. The mass ratio of the aromatic ring contained in the said structure is 10 mass% or less, when the total amount of each of said component (A) and (B) is 100 mass%, It is characterized by the above-mentioned. Optical adhesive composition. The optical adhesive composition according to claim 1, wherein the cationic curing catalyst is a photocationic curing catalyst. The optical adhesive layer obtained by hardening | curing the optical adhesive composition in any one of Claims 1-4.