WO2021039320A1 - Photocurable composition, cured body thereof, sealing material, protective material, waterproof structure, and cured body production method - Google Patents

Abstract

Provided is a photocurable composition capable of changing colors after curing has finished, so as to be distinguishable from before the curing. The photocurable composition comprises a leuco dye, a photo-radical generation agent, and at least one acrylic compound selected from acrylic monomers, acrylic oligomers, and acrylic polymers. The color difference ΔE between the uncured color value (L^* ₀, a^* ₀, b^* ₀) and the post-curing color value (L^* ₁₀₀, a^* ₁₀₀, b^* ₁₀₀), as defined in the CIE 1976 (L^*, a^*, b^*) color space described in JIS Z8781-4, is 10 or greater. The color change parameter represented by formula (1) falls in the range of 0 to 2.0. [In formula (1), a^* ₀ and b^* ₀ respectively represent the color a^* value and b^* value in the pre-curing L^*a^*b^* color space, a^* ₅₀ and b^* ₅₀ respectively represent the color a^* value and b^* value in a 50% curing ratio L^*a^*b^* color space, and a^* ₁₀₀ and b^* ₁₀₀ respectively represent the color a^* value and b^* value in the post-curing L^*a^*b^* color space.]

Description

Photocurable composition and its cured product, sealing material, protective material, waterproof structure, and method for producing the cured product

The present invention relates to a photocurable composition, a cured product thereof, and the like, and a method for producing the same.

A photocurable composition that is liquid before application and can be used as a gasket or the like after being photocured after application is used after being sufficiently cured after being applied to a desired site. However, if, for example, it is uncured due to a process error or insufficiently cured due to deterioration of the UV lamp, the uncured photocurable composition may come into contact with the contact body and become contaminated. In addition, there is a risk that the product may be commercialized with insufficient curing, resulting in product defects due to a decrease in compression set.

Such a problem is that the change in appearance before and after curing of the photocurable composition is small and it is difficult to immediately notice whether or not the curing is completed. Therefore, a technique for distinguishing the presence or absence of curing by changing the color before and after curing. Has been developed and is described in, for example, International Publication No. 2016/129568 (Patent Document 1).

International Publication No. 2016/129568

However, in the technique described in International Publication No. 2016/129568 (Patent Document 1), the cured state of the photocurable composition does not necessarily correspond to the color change, and the color change indicates the end of curing. I couldn't say that. Further, if the dye concentration is high, it is difficult for light rays such as ultraviolet rays to reach the inside, and there is a concern that the curability is impaired.

The present invention has been made to solve such a problem. That is, there is provided a photocurable composition capable of obtaining a color change that can be distinguished from that before curing after completion of curing while coloring with a low concentration leuco dye.

The photocurable composition of the present invention and a cured product thereof that achieve the above object are as follows. That is, the present invention contains at least one acrylic compound selected from an acrylic monomer, an acrylic oligomer, and an acrylic polymer, a photoradical generator, and a leuco dye, and describes CIE1976 (L ^* , a ^{*) described in JISZ8781-4.} , B ^* ) Color between the uncured color value (L ^* ₀ , a ^* ₀ , b ^* ₀ ) defined in the color space and the color value after curing (L ^* ₁₀₀ , a ^* ₁₀₀ , b ^* ₁₀₀ ) Provided is a photocurable composition in which the degree difference ΔE is 10 or more and the chromaticity change parameter represented by the following formula (1) is in the range of 0 to 2.0.

[In the above formula (1), a ^* ₀ and b ^* ₀ indicate chromaticity a ^* value and b ^* value in the L ^* a ^* b ^* color space before curing, and a ^* ₅₀ and b ^* ₅₀ are. The chromaticity a ^* value and b ^{* value in the L *} a ^* b ^* color space at a curing rate of 50% are shown, and a ^* ₁₀₀ and b ^* ₁₀₀ are the chromaticity a in the L ^* a ^* b ^{* color space after curing. *} Value and b ^* value are shown. ]

Since the present invention contains at least one acrylic compound selected from an acrylic monomer, an acrylic oligomer, and an acrylic polymer, a photoradical generator, and a leuco dye, the acrylic monomer, acrylic oligomer, and acrylic can be irradiated with light. At least one acrylic compound selected from the polymers can be cured, and the chromaticity can be changed before and after curing. ^{Further, the uncured color values (L *} ₀ , a ^* ₀ , b ^* ₀ ) defined in the CIE1976 (L ^* , a ^* , b ^* ) color space described in JISZ8781-4 and the color values after curing (L * 0, a * 0, b * 0) Since ^{the chromaticity difference ΔE from L *} ₁₀₀ , a ^* ₁₀₀ , b ^* ₁₀₀ ) is 10 or more, the change in chromaticity before and after curing is large, and the difference is easy to understand.

[In the above formula (1), a ^* ₀ and b ^* ₀ indicate chromaticity a ^* value and b ^* value in the L ^* a ^* b ^* color space before curing, and a ^* ₅₀ and b ^* ₅₀ are. The chromaticity a ^* value and b ^{* value in the L *} a ^* b ^* color space at a curing rate of 50% are shown, and a ^* ₁₀₀ and b ^* ₁₀₀ are the chromaticity a in the L ^* a ^* b ^{* color space after curing. *} Value and b ^* value are shown. ]

Further, since the chromaticity change parameter represented by the above formula (1) is in the range of 0 to 2.0, the distance (color change) in the latter half of the reaction is at least half or more larger than that in the first half of the reaction, so that curing due to color change It is possible to prevent misunderstanding of the state. The chromaticity difference and the chromaticity change parameter in the present invention are values measured and calculated by the method described in Examples.

The present invention can be a photocurable composition that does not contain an acid generator. The photocurable composition containing no acid generator does not cause an early color change to the leuco dye, and it is easy to make the curing of the acrylic monomer, the acrylic oligomer, and the acrylic polymer correspond to the reaction by the leuco dye.

According to the present invention, the acrylic compound can be a photocurable composition in which the acrylic compound is at least one of a monofunctional acrylic monomer, a bifunctional or higher acrylic oligomer, and a bifunctional or higher acrylic polymer. A photocurable composition in which the acrylic compound is at least one of a monofunctional acrylic monomer, a bifunctional or higher acrylic oligomer, and a bifunctional or higher acrylic polymer, the cured product obtained by curing the photocurable composition is an electronic element. It can be used as a suitable sealing material, protective material, etc. because it adheres to the substrate and exhibits waterproofness and the like.

According to the present invention, the acrylic compound can be a photocurable composition containing at least a monofunctional acrylic monomer and further containing a styrene-based elastomer. A photocurable composition in which the acrylic compound contains at least a monofunctional acrylic monomer and further contains a styrene-based elastomer can reduce the transparency of the cured product and impart rubber elasticity while increasing its mechanical strength. it can.

In the present invention, the styrene-based elastomer is at least one of a high-molecular-weight styrene-based elastomer having a weight average molecular weight of 200,000 or more, an epoxy-modified styrene-based elastomer, and a styrene-based elastomer having an unsaturated bond in a soft segment. It can be a curable composition. A photocurable composition in which the styrene-based elastomer is at least one of a high-molecular-weight styrene-based elastomer having a weight average molecular weight of 200,000 or more, an epoxy-modified styrene-based elastomer, and a styrene-based elastomer having an unsaturated bond in a soft segment. Can reduce the compression set when it is made into a cured product, and can be suitably used as a sealing material, a protective material, and the like.

In the present invention, the styrene-based elastomer can be a photocurable composition which is a styrene-isobutylene-styrene block polymer. The photocurable composition in which the styrene-based elastomer is a styrene-isobutylene-styrene block polymer can reduce the transparency of the cured product and impart rubber elasticity while increasing its mechanical strength. , Can be suitably used as a protective material such as a sealing material.

The present invention can be a photocurable composition further containing an inorganic powder. A photocurable composition further containing an inorganic powder imparts thixotropy to the photocurable composition and has shape stability after coating, and thus serves as a protective material such as a sealing material and a sealing material, and a masking material. It can be preferably used.

The present invention can be a cured product of any of the above photocurable compositions in which ΔE changes by 20 or more when immersed in 1N hydrochloric acid at 70 ° C. for 120 hours. The cured product obtained by curing any of the above photocurable compositions in which ΔE changes by 20 or more when immersed in 1N hydrochloric acid at 70 ° C. for 120 hours does not contain an acid generator. Such a cured product is preferable because there is little concern that the residual acid will corrode the substrate, wiring, electronic elements, housing, and other adherends.

The present invention can be a cured product having a Martens hardness of 0.005 to 50 N / mm ^{2 as measured by a nanoindentation test.} A cured product having a Martens hardness of 0.005 to 50 N / mm ² measured in a nanoindentation test has an excellent balance of flexibility, extensibility, and compressibility, and protects sealing materials, encapsulants, etc. It can be suitably used as a material and a masking material.

The present invention can be a cured product of any of the above photocurable compositions or the cured product, and can be a sealing material having a compression set of 50% or less. Since the cured product of any of the above photocurable compositions or the cured product has a compression set of 50% or less, it can be used as a sealing material such as a gasket having excellent sealing properties.

The present invention can be a cured product of any of the above photocurable compositions or a cured product of any of the above, and can be used as a protective material for covering an electronic element or wiring on a substrate. The cured product of any of the photocurable compositions or the cured product of any of the above, and the protective material covering the electronic element or wiring on the substrate is excellent with predetermined flexibility and flexibility. It is a protective material.

The present invention includes a case having an opening, a lid that closes the opening, and the sealing material provided on at least one of the case or the lid, and by fitting the case and the lid. The sealing material can be compressed and deformed to form a waterproof structure that tightly seals the opening. The present invention includes a case having an opening, a lid that closes the opening, and the sealing material provided on at least one of the case or the lid, and by fitting the case and the lid. Since the sealing material is compressed and deformed to form a waterproof structure that tightly seals the opening, the waterproof structure has excellent sealing properties.

The present invention is selected from a sealing material, a protective material, a masking material, an adhesive, and a vibration-proof material, which comprises at least a step of applying any of the above-mentioned photocurable compositions and a step of irradiating with activation energy rays. It can be a method for producing at least one cured product. The present invention is selected from a sealing material, a protective material, a masking material, an adhesive, and an anti-vibration material, which comprises at least a step of applying any of the above photocurable compositions and a step of irradiating with activation energy rays. Since the method for producing at least one cured product is used, the production of these cured products is easy.

The photocurable composition of the present invention has a color change that can be distinguished from that before curing after the completion of photocuring. Further, the cured product of the photocurable composition of the present invention can be used for various purposes such as an adhesive, a masking material, a gasket, a sealing material, and a sealing material.

It is explanatory drawing explaining the chromaticity measurement procedure.

[Photocurable composition]
The present invention will be described in detail based on the embodiments. The photocurable composition of the present invention comprises at least one acrylic compound selected from an acrylic monomer, an acrylic oligomer, and an acrylic polymer, a photoradical generator, and a leuco dye, and comprises JISZ8781-4. The uncured color values (L ^* ₀ , a ^* ₀ , b ^* ₀ ) defined in the CIE1976 (L ^* , a ^* , b ^* ) color space described in 1 and the color values after curing (L ^* ₁₀₀ , a). ^{The chromaticity difference ΔE from *} ₁₀₀ , b ^* ₁₀₀ ) is 10 or more, and the chromaticity change parameter represented by the following equation (1) is in the range of 0 to 2.0.

[In the above formula (1), a ^* ₀ and b ^* ₀ indicate chromaticity a ^* value and b ^* value in the L ^* a ^* b ^* color space before curing, and a ^* ₅₀ and b ^* ₅₀ are. The chromaticity a ^* value and b ^{* value in the L *} a ^* b ^* color space at a curing rate of 50% are shown, and a ^* ₁₀₀ and b ^* ₁₀₀ are the chromaticity a in the L ^* a ^* b ^{* color space after curing. *} Value and b ^* value are shown. ]

The "before curing" of the photocurable composition means a state before the photocuring reaction such as irradiation with ultraviolet rays is performed in a state where the components forming the photocurable cured product are mixed, and the "after curing" means. A state in which the photocurable composition is cured under conditions that can sufficiently complete the photocuring reaction. However, in view of the fact that sufficient curing may not be observed, in the examples described later, "after curing" is defined as a state of being cured by irradiating light for curing under the condition of an ^{integrated light amount of 15,000 mJ / cm 2.} , The change in peak height when the infrared absorption spectrum is measured by the FT-IR method described later is shown in a substantially saturated state.

The photocurable composition is cured with an uncured color value (L ^* ₀ , a ^* ₀ , b ^* ₀ ) ^{defined in the CIE1976 (L *} , a ^* , b ^{*) color space described in JISZ8781-4.} Since the chromaticity difference ΔE from the later color values (L ^* ₁₀₀ , a ^* ₁₀₀ , b ^* ₁₀₀ ) is 10 or more, the color change between the uncured state and the cured state is clear, and the difference can be seen. Can be recognized. When ΔE is 20 or more, the color change is larger, and when ΔE is 30 or more, the color change in the latter half of the reaction is large even when the chromaticity change parameter is large, which is particularly preferable. On the other hand, if ΔE is less than 10, the color change before and after curing is small, and it may be difficult to determine whether or not curing is completed.

The molecules of the above formula (1) are based on the coordinates of the uncured chromaticity (a ^* ₀ , b ^* ₀ ^{) on the a *} , b ^* plane, and the coordinates of the chromaticity in the cured state with a curing rate of 50% (a ^*). _{The distance to 50} , b ^* ₅₀ ) is shown, and the denominator of equation (1) is the coordinates of the chromaticity of the cured state with a curing rate of 50% on the ^{a *} , b ^{* plane (a *} ₅₀ , b ^* ₅₀ ). It shows the distance from to ^{the coordinates (a *} ₁₀₀ , b ^* ₁₀₀ ) of the chromaticity in the cured state after curing (curing rate 100%). Therefore, the formula (1) is expressed when the curing rate of the photocurable composition is 50% to 100% with respect to the distance (color change) when the curing rate is 0% to 50% (first half of the reaction). The ratio of the distance (color change) of (the latter half of the reaction) is shown. This is used as a chromaticity change parameter. Since the value of this equation (1), that is, the chromaticity change parameter is in the range of 0 to 2.0, the color change in the latter half of the reaction is the smallest when the value is 2.0, and the closer to 0, the latter half of the reaction. The color change is large (or the color change in the first half of the reaction is small), and the distance (color change) in the latter half of the reaction is at least half or more larger than that in the first half of the reaction. From the viewpoint that the color change in the latter half of the reaction is large, the chromaticity change parameter is preferably 0 to 1.0, and particularly preferably 0 to 0.5.

It has long been known that the chromaticity differs depending on the curing of an object, but the degree of curing and the degree of color change of the photocurable composition do not always match, and generally the color changes in the initial stage of curing. Was almost always progressing. Therefore, even though the curing has not been completely completed, there are cases where the color change causes the product to be mistaken for the cured product. However, in the present invention, by dividing the state of color change into two in a state where the curing rate of the photocurable composition is 50%, it is possible to emphasize the magnitude of the color change at the time of curing the remaining 50% in the latter half of the reaction. In addition, since the case where the value of the formula (1) is in the range of 0 to 2.0 is set, it is possible to exclude the case where most of the color changes are completed in the first half of the reaction. As a result, a photocurable composition capable of preventing misunderstanding of the cured state due to color change can be obtained. Next, the components constituting the photocurable composition will be described.

The photocurable composition of the present invention comprises at least an acrylic compound of at least one of an acrylic monomer, an acrylic oligomer, and an acrylic polymer, a photoradical generator, and a leuco dye, but the acrylic monomer and acrylic. Regarding oligomers and acrylic polymers, as used herein and in the scope of claims, "acrylic monomer" is synonymous with (meth) acrylic monomer and is used to include not only acrylic acid ester monomer but also methacrylic acid ester monomer. Similarly, "acrylic oligomer" is synonymous with (meth) acrylic oligomer and includes methacrylic acid ester oligomer in addition to acrylic acid ester oligomer, and "acrylic polymer" is synonymous with (meth) acrylic polymer and is acrylic. It is used in the sense that it includes a methacrylate ester polymer in addition to the acid ester polymer. Further, all of the acrylic monomer, the acrylic oligomer, and the acrylic polymer are compounds having a radically polymerizable group, and those after the radical polymerization reaction are distinguished by notation as "cured product". This photocurable composition can be made into a cured product by photocuring an acrylic monomer, an acrylic oligomer and an acrylic polymer.

Monofunctional acrylic monomer:
The monofunctional acrylic monomer is a component that is cured by a photoradical polymerization initiator, and is a low-viscosity liquid before curing. If a styrene-based thermoplastic elastomer is included in the photocurable composition, the monofunctional acrylic monomer dissolves the styrene-based thermoplastic elastomer. The cured product of the monofunctional acrylic monomer adheres to an electronic element or a substrate and exhibits waterproofness and the like.

The monofunctional acrylic monomer contains a monofunctional high-polarity monomer such as a monofunctional (meth) acrylamide-based monomer in addition to the monofunctional (meth) acrylic acid ester monomer. More specifically, aliphatic (meth) acrylic acid ester monomer, alicyclic (meth) acrylic acid ester monomer, ether-based (meth) acrylic acid ester monomer, cyclic ether-based (meth) acrylic acid ester acrylic monomer, fragrance. Group (meth) acrylic acid ester monomer, heterocyclic (meth) acrylic acid ester monomer, etc., and further hydroxyl group-containing (meth) acrylic acid ester monomer, carboxyl group-containing (meth) acrylic acid ester monomer, acrylamide-based monomer, Polar groups such as tertiary amino group-containing (meth) acrylic acid ester monomer, imide-based (meth) acrylic acid ester monomer, glycidyl group-containing (meth) acrylic acid ester monomer, and phosphoric acid group-containing (meth) acrylic acid ester monomer. Contains (meth) acrylic acid ester monomers having.

Specific examples of the monofunctional aliphatic (meth) acrylic acid ester monomer include aliphatic carbides such as butyl acrylate, lauryl acrylate, stearyl acrylate, isostearyl acrylate, decyl acrylate, isodecyl acrylate, isononyl acrylate, and n-octyl acrylate. Examples thereof include hydrogen-based (meth) acrylic acid ester monomers. Lauryl acrylate is preferable when used in combination with a styrene-based elastomer because it is extremely excellent in solubility of the styrene-based elastomer and also excellent in flexibility.

By blending a monofunctional aliphatic (meth) acrylic acid ester monomer, the styrene-based thermoplastic elastomer is dissolved when blended, and the flexibility of the cured product obtained after curing of the photocurable composition is increased. It can be increased, the Martens hardness and Young's modulus can be lowered, and the elongation at the time of cutting can be greatly improved.

Specific examples of the monofunctional alicyclic (meth) acrylic acid ester monomer include isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4 -Tert-Butylcyclohexylacrylate and the like can be mentioned.

By blending a monofunctional alicyclic (meth) acrylic acid ester monomer, when a styrene-based thermoplastic elastomer is contained, it can be dissolved. The monofunctional alicyclic (meth) acrylic acid ester monomer enhances the adhesive strength of the cured product (for example, a sealing material) after curing of the photocurable composition, and when the cured product is peeled off from the adherend. It is possible to reduce the adhesive residue. It also has the effect of making the cured product tough and increasing Young's modulus. In addition, increasing the proportion of this component can enhance moisture resistance and transparency.

For the monofunctional aliphatic (meth) acrylic acid ester monomer and the alicyclic (meth) acrylic acid ester monomer, it is preferable to use the acrylic acid ester monomer, respectively. This is because many acrylic acid ester monomers are superior in photocurability as compared with methacrylic acid ester monomers, and in addition to being able to be cured with a relatively low integrated amount of light, the cured product tends to be flexible.

When a monofunctional aliphatic (meth) acrylic acid ester monomer and a monofunctional alicyclic (meth) acrylic acid ester monomer are used, they can be used as an adhesive because they have adhesive strength derived from these components. .. It is also preferable as a sealing material because it adheres to the adherend and can prevent foreign matter and moisture from entering.

Further, it is preferable to use the alicyclic (meth) acrylic acid ester monomer and the aliphatic (meth) acrylic acid ester monomer in combination. The aliphatic (meth) acrylic acid ester monomer can increase the flexibility of the cured product and greatly improve the elongation at the time of cutting, while the alicyclic (meth) acrylic acid ester monomer makes the cured product tough. It has the effect of increasing the tensile strength. Therefore, by using both of them in combination, it is possible to achieve both appropriate flexibility and hardness.

Examples of the ether-based (meth) acrylic acid ester monomer include 2-butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, and nonylphenolethylene oxide-modified acrylate.

Examples of the cyclic ether-based acrylic acid ester monomer include tetrahydrofurfuryl acrylate, (2-methyl-2-ethyl-1,3-dioxolane-4-yl) methyl acrylate, and (3-ethyl-3-oxetanyl) methyl acrylate. Can be mentioned.

Examples of the aromatic acrylic acid ester monomer include phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, nonylphenol ethylene oxide-modified acrylate, and benzyl acrylate.

Examples of the hydroxyl group-containing acrylic acid ester monomer include 1,4-cyclohexanedimethanol monoacrylate, 2-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxyethyl acrylate.

Examples of the carboxyl group-containing acrylic acid ester monomer include ω-carboxy-polycaprolactone monoacrylate, monohydroxyethyl phthalate acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid and the like. it can.

Examples of the acrylamide-based monomer include acrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, hydroxyethylacrylamide, acroylmorpholin and the like.

Examples of the tertiary amino group-containing (meth) acrylic acid ester monomer include 2- (dimethylamino) ethyl methacrylate (DMAEMA) and the like.

Examples of the imide-based (meth) acrylic acid ester monomer include N-acryloyloxyethyl hexahydrophthalimide and N-acryloyloxyethyl tetrahydrophthalimide.

Examples of the glycidyl group-containing (meth) acrylic acid ester monomer include glycidyl acrylate, glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether and the like.

Examples of the phosphoric acid group-containing (meth) acrylic acid ester monomer include 2-metacloyloxyethyl acid phosphate and the like.

Among these, an aliphatic acrylic acid ester monomer and an alicyclic acrylic acid ester can be obtained from the viewpoint that a photocurable composition having almost no adverse effect on color change and having excellent distinguishability of color change due to curing can be obtained. Monomers, aromatic acrylic acid ester monomers, and acrylamide-based monomers are preferable.

Further, from the viewpoint of storage stability of the photocurable composition and improvement of adhesion to the resin, it is preferable to use a monofunctional highly polar monomer, and among the monofunctional highly polar monomers, an acrylamide-based monomer and a tertiary amino group are contained. Nitrogen-containing monomers such as (meth) acrylic acid ester monomer and imide-based (meth) acrylic acid ester monomer are preferable. In particular, an imide-based (meth) acrylic acid ester monomer is preferable from the viewpoint of enhancing the adhesion to the polyimide film. Further, from the viewpoint of improving the adhesiveness to the metal, a phosphoric acid group-containing (meth) acrylic acid ester monomer, a hydroxyl group-containing acrylic acid ester monomer, and a carboxyl group-containing acrylic acid ester monomer are preferable.

When both an alicyclic (meth) acrylic acid ester monomer and an aliphatic (meth) acrylic acid ester monomer are contained, the alicyclic (meth) acrylic acid ester monomer and the aliphatic (meth) acrylic acid ester monomer The mass ratio is preferably 4: 1 to 1: 4. By using both the alicyclic (meth) acrylic acid ester monomer and the aliphatic (meth) acrylic acid ester monomer, the adverse effect on the color tone change of the composition can be reduced and the metal adhesiveness can be enhanced.

When the monofunctional aliphatic (meth) acrylic acid ester monomer exceeds 4 times by mass of the alicyclic (meth) acrylic acid ester monomer, adhesive residue is generated when the cured product of the photocurable composition is peeled off. There is a risk that the adhesive strength and moisture resistance will be insufficient. On the other hand, if it is less than one-fourth, the cured product tends to become hard, and the adhesiveness may increase more than necessary due to aging, making peeling difficult. Then, by setting the mass ratio of the alicyclic (meth) acrylic acid ester monomer to the aliphatic (meth) acrylic acid ester monomer in the range of 3: 2 to 1: 4, it has appropriate adhesion and can be cut. A cured product (for example, a sealing material) having a large time elongation and easy peeling can be obtained.

Polyfunctional acrylic monomer:
The polyfunctional acrylic monomer is also a component that is cured by the photoradical polymerization initiator. When the cured product of the photocurable composition is used as a gasket, a sealing material, a sealing material, etc., it can be blended in a small amount for the purpose of adjusting the hardness and reducing the surface tack, but only this is an essential component. It is difficult to do so, and it can be added as an auxiliary component of the monofunctional acrylic monomer. Examples of such a polyfunctional acrylic monomer include a polyfunctional aliphatic (meth) acrylic acid ester monomer, a polyfunctional highly polar monomer, and a cyclized polymerizable (meth) acrylic monomer.

Examples of the polyfunctional aliphatic (meth) acrylic acid ester monomer include a bifunctional aliphatic (meth) acrylic acid ester monomer, and specific examples of the bifunctional aliphatic (meth) acrylic acid ester monomer include ethylene glycol di. (Meta) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, glycerin di (meth) acrylate, tricyclodecanedimethanol di. (Meta) acrylate, neopentyl glycol di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di ( Examples thereof include meta) acrylate and 1,10-decanediol di (meth) acrylate. When a styrene-based thermoplastic elastomer is added, since the compatibility with the soft segment is relatively high, a bifunctional aliphatic hydrocarbon-based di (meth) acrylic acid ester monomer having reactive groups at both ends is used. It is preferable to use it.

The polyfunctional high-polarity monomer includes a (meth) acrylic acid ester monomer having a polar group and bismaleimide. Specific examples of the (meth) acrylic acid ester monomer having a polar group include di / tri (meth) acrylate ethoxylated isocyanurate, ε-caprolactone-modified tris- (2-acryloxyethyl) isocyanurate, and 2-methacryoxy. Examples thereof include ethyl acid phosphate, 2-hydroxy-3-acryloyloxypropyl methacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, and bisphenol A diglycidyl ether acrylic acid adduct. From the viewpoint of improving adhesion, a tris (2-hydroxyethyl) isocyanurate-based (meth) acrylic acid ester monomer is preferable.

Specific examples of bismaleimide include 4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 2,2-bis [4- (4-maleimide phenoxy) phenyl] propane, and bis. Examples thereof include (3-ethyl-5-methyl-4-maleimidephenyl) methane, 1,6-bis (maleimide) hexane, and 1,6'-bismaleimide- (2,2,4-trimethyl) hexane. Among these, 1,6-bis (maleimide) hexane and 1,6'-bismaleimide- (2,2,4-trimethyl) hexane are difficult to inhibit the compatibility and photocurability of the photocurable composition. Such as aliphatic bismaleimide is preferable.

Alternatively, examples of the cyclized polymerizable (meth) acrylic monomer include α-allyloxymethyl acrylate (AOMA) and α-hydroxymethyl acrylate dimer (RHMA-D). Since these have a low viscosity, they can be used for adjusting the viscosity of a photocurable composition, and since the three-dimensional crosslink density is not excessively increased by curing, they have hardness and heat resistance while maintaining appropriate flexibility. , Can increase toughness. Among the above, α-allyloxymethyl acrylate is preferable from the viewpoint of improving coatability, heat resistance, and adhesiveness of glass and the like.

When a cured product of a photocurable composition is used as a gasket, a sealing material, a sealing material, etc. and a bifunctional or higher acrylic monomer is blended, 5% by mass or less is contained in the photocurable composition or the cured product thereof. It is preferably contained so as to be, and more preferably 1% by mass or less. This is because if a large amount is added, there is a concern that the hardness will increase and the adhesiveness to the adherend will decrease.

Acrylic oligomer:
The acrylic oligomer is a compound having a (meth) acrylic group mainly having a weight average molecular weight in the range of 1,000 to 50,000. The acrylic oligomer includes an oligomer obtained by polymerizing the acrylic monomer to a predetermined molecular weight, and an oligomer having a (meth) acrylic group at the end or side chain of a main chain other than acrylic. For example, polybutadiene-based acrylic oligomer, acrylamide-based oligomer, polyisoprene-based acrylic oligomer, polyurethane-based acrylic oligomer, polyester-based acrylic oligomer, polyether-based acrylic oligomer, epoxy ester-based acrylic oligomer, bisphenol-based acrylic oligomer, novolak-type acrylic oligomer, etc. Can be mentioned.

Acrylic polymer:
Acrylic polymers are compounds having (meth) acrylic groups with a weight average molecular weight of 50,000 to 5 million. Acrylic polymers include polymers obtained by polymerizing the acrylic monomer or acrylic oligomer to a predetermined molecular weight, and polymers in which a (meth) acrylic group is added to a compound other than the acrylic compound. For example, the former includes a homopolymer obtained by polymerizing butyl acrylate. Examples of the latter include compounds having a (meth) acrylic group added to a compound having a polybutadiene, acrylamide, polyisoprene, polyurethane, polyester, polyether, epoxy skeleton and the like, and specifically, a polybutadiene-based acrylic polymer and an acrylamide-based acrylic. Examples thereof include polymers, polyisoprene-based acrylic polymers, polyurethane-based acrylic polymers, polyester-based acrylic polymers, polyether-based acrylic polymers, epoxy ester-based acrylic polymers, bisphenol-based acrylic polymers, and novolak-type acrylic polymers.

The total amount of the acrylic monomer, the acrylic oligomer, and the acrylic polymer is preferably 50% by mass to 99% by mass with respect to the mass of the photocurable composition. The blending amount of the monofunctional acrylic monomer is preferably 10% by mass to 94% by mass with respect to the total mass of the acrylic monomer, the acrylic oligomer, the acrylic polymer, and the thermoplastic elastomer described later.

Styrene-based thermoplastic elastomer:
Styrene-based thermoplastic elastomers (also referred to as styrene-based elastomers) are not essential components. However, the styrene-based elastomer can be dissolved in an acrylic monomer or an acrylic oligomer in the photocurable composition, and the transparency can be lowered due to the hard segment thereof. Therefore, the color change can be easily recognized as compared with the case where the photocurable composition is transparent. Further, the styrene-based elastomer can increase the mechanical strength of the cured product after the acrylic monomer or the acrylic oligomer is cured and can impart rubber elasticity (flexibility). Then, the compression set can be reduced, and in addition, the moisture permeability can be reduced.

Specific examples of the styrene-based elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and the like. Styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and epoxy-modified styrene-based Examples thereof include these modified products such as styrene.

Among the above styrene-based elastomers, soft products such as styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene / isoprene copolymer-styrene block copolymer. A styrene-based elastomer having an unsaturated bond in the segment can reduce the compressive permanent strain of the cured product as compared with the case where a styrene-based elastomer having no unsaturated bond in the soft segment is used. Therefore, when the cured product is used as a gasket, a sealing material, a sealing material, or the like, the sealing property can be maintained for a long period of time. In addition, the tack on the surface of the cured product can be reduced, and the compression set can be made less likely to deteriorate when the inorganic powder is added.

When a styrene-based elastomer having an unsaturated bond in the epoxy-modified styrene-based elastomer or the soft segment is used among the above-mentioned styrene-based elastomers, the styrene-based elastomer having an unsaturated bond in the epoxy-modified styrene-based elastomer or the soft segment is used. Compared with the case where it is not contained, the compression set of the cured product obtained after curing can be reduced, and the sealing property during long-term use is improved. Further, by including the epoxy-modified styrene-based elastomer or the styrene-based elastomer having an unsaturated bond in the soft segment, the tack on the surface of the cured product can be reduced, and the compression set deteriorates even if an inorganic powder is added. It can be difficult to do.

Further, the styrene-based elastomer preferably contains a high molecular weight styrene-based elastomer. Here, the high molecular weight styrene-based elastomer means an elastomer having a weight average molecular weight of 200,000 or more. The weight average molecular weight of this high molecular weight styrene elastomer is preferably 250,000 or more, and more preferably 400,000 or more. There is no particular upper limit, but it can be, for example, 1 million or less. The weight average molecular weight can be measured by using the GPC method (Gel Permeation Chromatography) and based on the calibration curve (calibration curve) measured by standard polystyrene.

By including the high molecular weight styrene elastomer, the compression set can be reduced as compared with the case of using the low molecular weight styrene elastomer having a weight average molecular weight of less than 200,000, and the cured product can be sealed with a gasket, a sealing material or a sealant. When used as a stopper, the sealing property can be maintained for a long period of time. Further, since the bleed-out of the plasticizer can be suppressed by containing the high molecular weight styrene-based elastomer, a cured product having high flexibility can be obtained by adding a large amount of the plasticizer.

When the styrene-based elastomer is blended, the amount added is preferably 1 to 60% by mass, more preferably 2 to 45% by mass in the photocurable composition. If the content of the styrene-based elastomer is less than 1% by mass, the mechanical strength may be lowered when the cured product is used as a gasket, a sealing material, a sealing material, or the like. On the other hand, if it exceeds 60% by mass, the viscosity of the photocurable composition tends to increase. If it is 35% by mass or less, the fluidity is suitable and it is easy to apply.

However, in the case of the high molecular weight styrene elastomer, the amount added is preferably 1 to 7% by mass, more preferably 2 to 5% by mass in the photocurable composition. If the content of the high molecular weight styrene elastomer is less than 1% by mass, the mechanical strength may be lowered. On the other hand, if it exceeds 10% by mass, the viscosity of the photocurable composition tends to increase.

Among the above high molecular weight styrene elastomers, it is preferable to use a high molecular weight styrene elastomer having a predetermined branched chain (typically a branched chain extending radially from the core) called a star polymer. The high molecular weight styrene elastomer having such a predetermined branched chain can suppress the entanglement of the main chains as compared with the linear high molecular weight styrene elastomer, and even if it is blended in a relatively high concentration. It is possible to suppress an increase in the viscosity of the photocurable composition. Specifically, this high molecular weight styrene-based elastomer can be blended in the photocurable composition at a concentration of about 5 to 20% by mass.

Photoradical generator:
The photoradical generator is one that generates radicals and cures an acrylic monomer, an acrylic oligomer, and an acrylic polymer by a photoradical polymerization reaction. The photoradical generator includes a photoradical polymerization initiator.

Examples of the photoradical polymerization initiator include benzophenone-based, thioxanthone-based, acetophenone-based, acylphosphine-based, oxime ester-based, alkylphenone-based, and intramolecular hydrogen abstraction-type photopolymerization initiators. Among these, it is preferable to use an alkiferone-based initiator or an oxime ester-based initiator from the viewpoint of easily increasing the chromaticity difference.

As the alkylphenone system, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenylketone, 2-hydroxy-2-methyl-methylpropanol, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-Hydroxy-methylpropanone, 2-hydroxy-1-(4- (4- (2-hydroxy-2-methylpropionyl) benzyl) phenyl) -2-methylpropan-1-one, 2-methyl- 1- [4- (Methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2- (dimethylamino) -4'-morpholinobutylphenone, 2-dimethylamino-2- (4-) Examples thereof include methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butane-1-one.

Examples of the acylphosphine type (acylphosphine oxide type) include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide and the like.

Examples of the intramolecular hydrogen abstraction type include a mixture of methyl benzoylate, oxyphenylacetic acid-2-oxo-2-phenylacetoxyethoxyethyl ester and oxyphenylacetic acid-2-hydroxyethoxyethyl ester.

Examples of the oxime ester type (oxyphenyl acetate type) include 1- [4- (phenylthio) phenyl] octane-1,2-dione = 2- (O-benzoyloxime) and 1- [9-ethyl-6- ( 2-Methylbenzoyl) -9H-carbazole-3-yl] Ethanone-1- (O-acetooxime) and the like can be mentioned.

The amount of the photoradical polymerization initiator added is preferably 0.1 to 10 parts by mass, preferably 1 to 8 parts by mass, based on 100 parts by mass of the total amount of all acrylic monomers and acrylic oligomers including monofunctional and bifunctional or higher. The part is more preferable. This is because if it is less than 0.1 part by mass, the polymerization may be insufficient and the curing may not be completed, and even if it is added in excess of 10 parts by mass, the effect of increasing the degree of polymerization does not increase so much.

Leuco dye:
The leuco dye is a compound that generally develops color upon contact with an acid, and in the present invention, it has a function of developing color after curing of the photocurable composition to confirm the completion of curing of the photocurable composition. Specific examples of leuco dyes include indrill phthalides, diphenylmethane phthalides, monovinyl phthalides, divinyl phthalides, diphenylmethane azaphthalides, phthalides including phenyl indolyl azaphthalides, fluorans, and the like. Types such as thiazines, stylinoquinolins, lactones, lactams, and triphenylmethanes can be mentioned.

Phthalides include 3,3 bis [4- (dimethylamino) phenyl] phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylaminophenyl) -3. -(1-Ethyl-2-methylindole-3-yl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,3-bis (1-butyl-2-methyl-1H-) Indole-3-yl) phthalide, etc. can be mentioned.

Fluolans include 2'-methyl-6'-(Np-tolyl-N ethylamino) spiro [isobenzofuran-1 (3H), 9'-[9H] xanthene] -3-one, 1,3. -Dimethyl-6-diethylaminofluorane, 2-chloro-3-methyl-6-dimethylaminofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- Anilinofluolane, 3-diethylamino-6-methyl-7-xylidinofluorane, 2- (2-chloroanilino) -6-dibutylaminofluorane, 3,6-dimethoxyfluorane, 3,6-di-n -Butoxyfluolane, 1,2-benz-6-diethylaminofluorane, 1,2-benz-6-dibutylaminofluorane, 1,2-benz-6-ethylisoamylaminofluorane, 2-methyl-6- (Np-trill-N-ethylamino) fluorane, 2- (N-phenyl-N-methylamino) -6- (Np-trill-N-ethylamino) fluorane, 2- (3'-tri Fluoromethylanilino) -6-diethylaminofluorane, 3-chloro-6-cyclohexylaminofluorane, 2-methyl-6-cyclohexylaminofluorane, 3-di (n-butyl) amino-6-methoxy-7- Examples thereof include anilinofluorane, 3,6-bis (diphenylamino) fluorane, methyl-3', 6'-bisdiphenylaminofluorane, chloro-3', 6'-bisdiphenylaminofluorane and the like.

Examples of thiazines include benzoyl leucomethylene blue.

Examples of lactams include rhodamine-B-anilinolactam, rhodamine- (p-nitroanilino) lactam, rhodamine- (o-chloroanilino) lactam, and rhodamine- (o-nitroanilino) lactam.

Examples of triphenylmethanes include leuco crystal violet (LCV).

Further, examples of the lactones include crystal violet lactone (CVL), which is a lactone derivative of crystal violet, and a diazarhodamine lactone derivative.

Among these, various lactones, phthalides, and fluorans having a lactone ring structure are preferable from the viewpoint that the color does not easily change after curing and the presence or absence of curing is excellent in distinguishability even after a lapse of a predetermined time.

The amount of the leuco dye added can be 0.001 to 2 parts by mass with respect to 100 parts by mass of the acrylic monomer, the acrylic oligomer, and the acrylic polymer, and is preferably 0.005 to 1 part by mass. If it is 0.001 to 0.1 parts by mass, it is possible to enhance the distinctiveness of the presence or absence of curing when curing with a thickness of 0.5 mm or more. Further, when the content is 0.1 to 2 parts by mass, the mechanical properties of the cured product of the photocurable composition can be enhanced. It is considered that the effect of enhancing the mechanical properties is observed in the region where the amount of the leuco dye added is slightly high, because the leuco dye promotes the radical reaction.

Plasticizer:
It is preferable to add a plasticizer to the photocurable composition if necessary. High flexibility can be imparted to the cured product by adding a plasticizer, which is suitable when used as a gasket or a sealing material. When a styrene-based elastomer is added, the plasticizer is preferably one that is compatible with the soft segment thereof. Specific examples of the plasticizer include paraffin-based oil, olefin-based oil, naphthen-based oil, and ester-based plasticizer, and specific examples of the ester-based plasticizer include phthalic acid ester, adipic acid ester, and trimellitic acid ester. , Polyester, phosphoric acid ester, citric acid ester, epoxidized vegetable oil, sebacic acid ester, azelacinic acid ester, maleic acid ester, benzoic acid ester and the like. Further, when the styrene-based elastomer is added, paraffin-based oil is preferable among these, and if paraffin-based oil is used, the effect of improving the extensibility by physical cross-linking of the hard segment of the styrene-based elastomer is small, and the cured product is cured. Contributes to the improvement of flexibility and compression set.

The amount of the plasticizer is preferably 30 parts by mass or less with respect to 100 parts by mass of the acrylic monomer and the acrylic oligomer. If it exceeds 30 parts by mass, the risk of the plasticizer bleeding out from the cured product increases.

Thixotropy-imparting agent:
It is preferable to add a thixotropic agent to the photocurable composition. By increasing the thixotropic property, the shape retention of the applied photocurable composition is improved. Therefore, it is possible to suppress dripping during application of the photocurable composition and improve the shape retention of the applied photocurable composition. For example, when the photocurable composition is formed into a three-dimensional object using a dispenser, it can be cured in the form in which the photocurable composition is applied, so that the cured product is used as a gasket material or a sealing material. Suitable for cases.

Specific examples of the thixotropy-imparting agent include an inorganic thixotropy-imparting agent consisting of inorganic powders such as silica, aluminum oxide, and titanium oxide; Agents and the like can be mentioned, but inorganic powder is preferable, and silica is preferable among them. The reason is that it is easy to control the hydrogen ion index (pH) of the photocurable composition by performing a predetermined surface treatment on the inorganic powder, and it is easy to obtain such a surface-treated silica among the inorganic powders. Because. When silica is used, the amount added is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the acrylic monomer, the acrylic oligomer, and the acrylic polymer (including the plasticizer when the plasticizer is contained). If it is less than 2 parts by mass, the effect of addition is difficult to obtain, and if it exceeds 10 parts by mass, the viscosity of the photocurable composition may increase too much, or the hardness of the cured product may become too hard.

As the surface-treated inorganic powder, it is preferable to use an inorganic powder having a hydrogen ion index of 3.0 to 11.0. Within the above range, the leuco dye undergoes a predetermined color change due to curing, so that it is excellent in distinguishability of the presence or absence of curing. Further, the hydrogen ion index is more preferably 3.6 to 5.5. This is because the distinguishability of the presence or absence of curing is enhanced. The hydrogen ion index is a hydrogen ion index measured for a dispersion liquid in which an inorganic powder having a concentration of 4% by mass is dispersed in pure water.

Colorant:
A white inorganic filler can also be added to the photocurable composition in order to make the color change clearer. By using a white inorganic filler, small color changes can be made clearer and visually distinguishable. Further, when the photocurable composition is applied to a coating target having a low lightness, the discriminability of the presence or absence of curing is enhanced.

Specific examples of the colorant include inorganic compounds such as aluminum oxide, titanium oxide, magnesium oxide, calcium carbonate, talc, bennite, and montmorolinite. Among these, aluminum oxide is particularly preferable because it not only enhances the distinctiveness of the presence or absence of curing, but also has the effect of enhancing the coatability by imparting appropriate thixotropy.
The hydrogen ion index of the colorant is preferably 3.0 to 11.0, and more preferably 3.6 to 5.5. This is because within this range, the effect of imparting thixotropy can be obtained in the same manner as when the thixotropic agent is added, and the synergistic effect of imparting thixotropy can be expected.

Other ingredients:
Various additives can be appropriately blended in the photocurable composition as long as the gist of the present invention is not deviated. In addition to the above plasticizers and thixophilicity-imparting agents, for example, silane coupling agents, polymerization inhibitors, defoamers, light stabilizers, antioxidants, antistatic agents, thermal conductive fillers, and other functional fillers. And so on.

The viscosity of the photocurable composition is preferably 10 to 1000 Pa · s at 25 ° C., more preferably 20 to 300 Pa · s. If it is less than 10 Pa · s, dripping is likely to occur when applying to an electronic element or the like with a dispenser. On the other hand, if it exceeds 1000 Pa · s, it becomes difficult to apply with a dispenser. Further, when it is set to 20 Pa · s or more, the shape retention from application to curing is enhanced, and when it is set to 200 Pa · s or less, fine dispensing using a finer needle becomes possible. The viscosity can be a value measured using a B-type rotational viscometer at a rotational speed of 10 rpm and a measurement temperature of 25 ° C.

Further, the thixotropy of the photocurable composition is preferably 2 or more at 25 ° C., and more preferably 4 or more. By setting the thixotropy to 2 or more, it is possible to prevent the photocurable composition from spreading before curing when the photocurable composition is applied. Therefore, in addition to the sealing material, a sealing material or a gasket It is preferable as an application such as. Further, by setting the thixotropy to 4 or more, the spread can be reduced even in a photocurable composition having a particularly low viscosity, and a fine shape can be formed by using a finer needle. The thixotropy is a value calculated as a ratio (viscosity (1 rpm) / viscosity (10 rpm)) obtained by measuring viscosity at rotational speeds of 1 rpm and 10 rpm at a measurement temperature of 25 ° C. using a B-type rotational viscometer. The upper limit of the thixotropy ratio is not limited, but is preferably about 20 or less.

Cured product of photocurable composition:
The photocurable composition can be cured by a photocuring reaction and used for various purposes such as an adhesive, a masking material, a gasket, a sealing material, and a sealing material. For example, if an electronic element provided on an electronic substrate or the like or a portion where metal is exposed is coated with a photocurable composition to cover an adherend, and then the photocurable composition is photocured by ultraviolet irradiation, the seal can be used. It can be used as a material. In addition to ultraviolet rays, as active energy rays, energy rays that activate (meth) acryloyl groups such as visible light or electron rays, and energy rays that generate radicals in a photoradical polymerization initiator can be used. Examples of the light source that irradiates ultraviolet rays include a high-pressure mercury lamp, a metal halide lamp, and an ultraviolet LED.

As the sealing material, the hardness thereof is preferably 60 degrees or less, more preferably 40 degrees or less, still more preferably 20 degrees or less in terms of A hardness according to JIS K6253-3: 2012 from the viewpoint of imparting rubber elasticity. It is even more preferable if the temperature is 5 degrees or less. If the temperature is 5 degrees or less, it can be used as a sealing material that requires an extremely low load. Further, the compression set of the cured product is preferably 50% or less. This is because the long-term sealing property can be guaranteed.

Further, in the cured product of the photocurable composition of the present invention, the maltens hardness measured in the nanoindentation test is preferably in the range ^{of 0.005 to 30 N / mm 2.} When the Martens hardness is in this range, it has predetermined flexibility and flexibility, and is suitable for applications such as sealing materials such as gaskets, masking materials, protective materials such as sealing materials, adhesives, and anti-vibration materials. It becomes. The method for measuring the Martens hardness can be specifically the method described in Examples.

The encapsulant preferably has flexibility that can be applied to a flexible substrate and strength that has repairability that can be removed after being used for encapsulating electronic components. Looking at these properties in terms of storage elastic modulus E', it is preferably in the range of 0.4 to 4.1 MPa. When the storage elastic modulus E'is 0.4 MPa or more, the cured product of the photocurable composition is hard to be torn and easily repaired, and when it is 4.1 MPa or less, the seal arranged on the flexible substrate is sealed. It becomes easy to peel off from the part to be stopped. Further, when long-term adhesiveness and protective effect are prioritized over repairability as a sealing material, the storage elastic modulus E'is preferably in the range of 4.1 to 250 MPa. Within this range, the cured product of the photocurable composition is less likely to be peeled off from the adherend due to the increased toughness, and the appropriate rigidity is provided to prevent the wiring from being broken due to bending. be able to.

Further, as an adhesive or a reinforcing member applied to the boundary portion between the rigid substrate and the flexible substrate, the mechanical strength such as Young's modulus and Martens hardness of the cured product of the photocurable composition is the strength appropriately required for the application. Is preferable.

The above-described embodiment is an example of the present invention, and the embodiments can be changed, known techniques can be added, combinations, and the like can be performed without departing from the spirit of the present invention, and these techniques are also within the scope of the present invention. It is included in.

Next, the present invention will be described in more detail based on Examples (Comparative Examples). A photocurable composition having the compositions shown in the following tables and a cured product obtained by curing the photocurable composition were prepared and used as Samples 1 to 29. Then, various tests were performed on these samples.

<Preparation of sample>

Sample 1 to Sample 29:
Acrylic monomer, acrylic oligomer, acrylic polymer, leuco dye, and styrene-based elastomer required depending on the sample are mixed, and after these are sufficiently mixed, an additive and a photoradical polymerization initiator are mixed to sample 1 to 1. A photocurable composition of Sample 29 was prepared. These photocurable compositions were irradiated with ultraviolet rays (LED light source having a wavelength of 365 nm) under the conditions of an illuminance of 250 mW / cm ² and an integrated light intensity of 15,000 mJ / cm ^{2 to obtain cured products of Samples 1 to 29.}

In each of the above tables, as the acrylic monomer, lauryl acrylate as the aliphatic acrylate, isobornyl acrylate as the alicyclic acrylate, phenoxyethyl acrylate as the aromatic acrylate, 2-hydroxyethyl acrylate as the hydroxyl group-containing acrylate, and carboxyl. Ω-carboxy-polycaprolactone monoacrylate as the group-containing acrylate, 2-methacryloxyethyl acid phosphate as the phosphate-containing acrylate, acroylmorpholine as the amide group-containing acrylate, and 2-methacrylate as the amino group-containing acrylate ( Dimethylamino) ethyl was used, and 1,9-nonanediol diacrylate was used as the bifunctional aliphatic acrylate.

Further, as the acrylic polymer, an acrylic polymer having an acrylic skeleton ("RC500 (XX067C)" (trade name), manufactured by Kaneka Corporation) was used.

As the photoradical polymerization initiator, 2-hydroxy-2-methyl-methylpropanol was used as an alkylphenone-based initiator, and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide was used as an acylphosphine oxide-based agent. A mixture of oxyphenylacetate-2-oxo-2-phenylacetoxyethoxyethyl ester and oxyphenylacetic acid-2-hydroxyethoxyethyl ester as the intramolecular hydrogen abstraction type, and 1- as the oxyphenylacetate ester system. [9-Ethyl-6- (2-methylbenzoyl) -9H-carbazole-3-yl] esterone-1- (O-acetooxym) was used, respectively.

Leuco dyes include 2'-methyl-6'-(N-p-tolyl-N ethylamino) spiro [isobenzofuran-1 (3H), 9'-[9H] xanthene] -3-one as fluorans. "RED520" (trade name), manufactured by Fukui Yamada Chemical Industry Co., Ltd., 3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide ("Crystal Violet lactone (CVL)", Fukui as phthalides Yamada Chemical Industry Co., Ltd.) and "Leuco Crystal Violet" ((trade name), manufactured by Tokyo Ohka Kogyo Co., Ltd.) were used as triphenylmethanes.

As the styrene-based thermoplastic elastomer, a styrene-isobutylene-styrene triblock copolymer (“SIBSTAR 102T” (trade name), manufactured by Kaneka Co., Ltd.) was used.

As an additive, a photoacid generator ("CPI-210S" (trade name), manufactured by San-Apro Co., Ltd.) is used, and silica ("Aerosil 200" (trade name), Nippon Aerosil Co., Ltd.) is used as a viscosity modifier and a nitrogen-imparting agent. Hydrophilic fumed silica with a specific surface area of about 200 m ² / g manufactured by the company) and aluminum oxide (“Alu C” (trade name), manufactured by Nippon Aerosil Co., Ltd., fumed aluminum oxide) were used as colorants. ..

<Various tests and evaluations>

Each of the above samples was subjected to various tests described below to evaluate the characteristics of the photocurable composition and its cured product.

Calculation of curing rate when transitioning from a photocurable composition to a cured product:
How much curing is achieved when the photocurable composition is in an intermediate state from an uncured state, that is, a state in which the curing rate is 0% to a completely cured state, that is, a state in which the curing rate is 100%. Whether it was progressing, that is, what percentage the curing rate was, was measured by the FT-IR method. FT-IR method, the vertical axis to record an infrared absorption spectrum is the absorbance for the cured finished product with uncured material, 780 cm ^-1 from fluctuations peak (820 cm ^-1 attributable to the chemical bonds decreases with the curing reaction ) And the area of the internal standard peak (1730 cm ^-1 ) are read from each spectrum, and the curing rate of the sample whose curing rate is undecided is calculated based on the values of the uncured body and the cured product.

More specifically, the area of the fluctuation peak of the measured sample is A, the area of the internal standard peak is B, and the area ratio R = A / B is obtained. Here, assuming that the R value of the uncured product is Ru and the R value of the cured product (cured product ^{produced by irradiating ultraviolet rays under the condition of an integrated light amount of 15,000 mJ / cm 2} ) is Rc, the Rc value is reduced with respect to the Ru value. The rate Dc (%), that is, the rate of decrease in the R value of the cured product can be calculated by the following formula (2).

Dc = (1-Rc / Ru) x 100 ... Equation (2)

Next, when the R value is obtained from the infrared absorption spectrum of the sample for which the curing rate is to be obtained, the reduction rate D (%) of this R value with respect to the Ru value can be obtained by the following equation (3).

D = (1-R / Ru) x 100 ... formula (3)

Then, the curing rate C (%) of the sample for which the curing rate is to be obtained can be obtained by comparing the D value of this sample with the Dc value. That is, it can be obtained by the following equation (4).

C = D / Dc x 100 ... Equation (4)

Regarding the determination of the curing rate by FT-IR, "Measurement of curing rate of chemically reactive resin (UV curing, thermosetting, moisture curing) and its practice-Actual application to adhesives, encapsulants, paints, etc. (Namiki) (By Yoichi) ”(Information Organization Co., Ltd.).

Saturation measurement:
The chromaticity was measured as follows. Explaining with reference to the schematic view shown in FIG. 1, first, as shown in FIG. 1A, two 1 mm-thick transparent glass plates 11 are prepared, and one side of the two transparent glass plates 11 is subjected to 0.1 mm peeling treatment (PET). HSPX) is pasted (not shown). A shim ring (spacer) 12 having a thickness of 1 mm and having a circular through hole 13 having a diameter of 10 mm is arranged on the glass plate 11 to which the PET is not attached, and the other glass plate is placed so that the PET faces the shim ring. The shim ring is sandwiched between two glass plates.

Next, the chromaticity of the reference white plate for calibration is measured. (Measurement of blank, FIG. 1B). Subsequently, the photocurable composition of each sample is applied to the through hole 13 of the shim ring 12, and the chromaticity of the photocurable composition before curing that has entered the through hole is measured as shown in FIG. 1C. .. At this time, a white calibration plate (not shown) is placed under the lower glass plate 11. The reason why the photocurable composition is sealed with two glass plates is to prevent the influence of oxygen in the air. Then, as shown in FIG. 1D, the photocurable composition 15 is irradiated with ultraviolet rays for a predetermined time with a UV lamp (“Aice UJ30” manufactured by Panasonic Corporation, wavelength 365 nm, illuminance 250 mW / cm ^{2) 16.} Finally, as shown in FIG. 1E, the chromaticity of the cured product of the photocurable photocurable composition is measured with a spectrophotometer (“Handy spectrophotometer JX777” manufactured by Color Techno System Co., Ltd.) 14. In the actual measurement of the chromaticity, the ultraviolet irradiation time at which the curing rate becomes 50% was determined in advance for each sample, and the chromaticity was determined for the sample after being irradiated with the ultraviolet rays for that time. The value of the formula (1), which is a chromaticity change parameter, was calculated from the chromaticity of each sample at uncured, cured rate of 50%, and cured (curing rate of 100%), and the results are shown in the above tables.

Measurement of chromaticity difference:
First, the same sample used in the chromaticity measurement is prepared. Subsequently, the sample is placed on a white plate for calibration, and the color of each sample is visually compared with the color of the color chip of the color sample "PANTONE uncoated chips" (manufactured by PANTONE). Recorded close color numbers. Subsequently, the chromaticity of each color chip is measured by the spectrophotometer. The chromaticity difference ΔE was calculated from the chromaticity corresponding to the uncured and cured (curing rate 100%) color of each sample thus obtained, and the results are shown in the above tables.

Separately, the sample used in the measurement of the chromaticity is placed on a white plate for calibration, and the chromaticity of each sample is measured by a spectrocolorimeter to obtain a second chromaticity difference ΔE. I asked for _2.
In the present invention, the term "chromaticity difference ΔE" indicates the chromaticity difference based on the color of the color chip, and the latter indicates the "second chromaticity difference ΔE ₂ ". To do. Here, the above-mentioned chromaticity difference ΔE is a value that faithfully reflects the color change visually observed. Therefore, if the chromaticity difference ΔE is large and the above-mentioned chromaticity change parameter is within a predetermined range, it means that it is easy to visually distinguish between before curing and after photocuring.

On the other hand, for example, in a special case where the state of curing is inspected using a spectrophotometer or a chromaticity meter in the production process, the second chromaticity difference ΔE ₂ is preferably 10 or more. , 20 or more is more preferable. In this case, replacing the chromaticity difference Delta] E in the second chromaticity difference Delta] E _2, only the second chromaticity difference Delta] E ₂ may be 10 or more. Further, both the chromaticity difference ΔE and the second chromaticity difference ΔE ₂ are preferably 10 or more, and more preferably 20 or more. In this case, in addition to being able to handle both spectrophotometric inspection and visual inspection, it is possible to prevent inadvertent contact with the uncured photocurable composition and improve the work safety of workers. Can be done. The chromaticity difference ΔE using the visually selected color chip and the chromaticity difference ΔE ₂ by the spectrophotometer correlate in many cases, but in some samples, the values deviate from the correlation. The reason is not clear, but there is a difference between the chromaticity measured by spectrophotometric measurement and the chromaticity visually perceived depending on the sample in which the reflected color and the transmitted color have a complementary color relationship and the degree of light diffusivity. It seems that it is occurring.

Calculation of ΔE / chromaticity change parameter:
In each table, the value obtained by dividing the chromaticity difference ΔE by the chromaticity change parameter is shown. This value becomes larger as the chromaticity difference is larger and the chromaticity change parameter is smaller (that is, the chromaticity change in the latter half of the reaction is larger). Therefore, it can be expected that this value correlates with the distinctiveness of the cured state.

Appropriateness confirmation test for curing judgment:
For each of the above samples, each specimen before curing (curing rate 0%), curing rate 25%, curing rate 50%, curing rate 75%, and after curing (curing rate 100%) was prepared for this test. First, the tester was shown the pre-cured test body and the post-cured test body for 30 seconds, then the test bodies were hidden, and after 3 minutes, the five test bodies having different cured states were randomly selected. They were shown one by one and asked if the test piece had a 100% cure rate or something else. This test was performed on one sample (that is, five test specimens) for five people, and the number of people who answered incorrectly was counted. The results are shown in the above tables.

Martens hardness (N / mm ² ):
A nanoindentation test of the cured product of each sample was carried out using a nanoindenter (manufactured by ELIONIX, ENT-2100). The test piece was prepared by applying a photocurable composition to a glass plate having a thickness of 1 mm so as to have a thickness of 200 μm, using an LED having a wavelength of 365 nm, under the conditions of ^{an illuminance of 250 mW / cm 2} and an integrated light amount of 15000 mJ / cm ^2. A cured product prepared by curing by irradiating with ultraviolet rays was used. Then, with the nano indenter, the Martens hardness of the cured product was measured under the conditions of a maximum pushing load of 0.1 mN and a pushing speed of 0.01 mN / sec.

Immersion test with 1 specified hydrochloric acid:
Each of the above samples was irradiated with ultraviolet rays having an integrated light intensity of 15,000 mJ / cm ² and cured to a thickness of 1 mm to obtain a cured product of each sample. Subsequently, 0.2 g of a test piece was cut out from this cured product, immersed in 10 g of 1N hydrochloric acid, and allowed to stand in an environment of 70 ° C. for 120 hours. Then, after 120 hours, the test piece was taken out and the water on the surface was lightly wiped off. The post-test test piece thus obtained was visually compared with the color chip of the color sample "PANTONE uncoated chips" (manufactured by PANTONE), and the closest color number was recorded. Subsequently, the chromaticity of each color chip is measured with the spectrocolorimeter, and the chromaticity difference is calculated from the chromaticity of the test piece after the test of each sample and the chromaticity of the test piece before the test. The results are shown in the item _{of chromaticity difference ΔE 3} after the immersion test in each table.

<Analysis of test results>

Looking at the results of the above-mentioned suitability confirmation test for curing judgment, it is erroneously answered that the curing rate of the sample 28 after curing (curing rate 100%) is other than 100 for the sample 28 whose ΔE is less than 10. There were some testers and some testers who mistakenly thought that the curing rate was 100% even if the curing rate was 75%, and many people gave incorrect answers. It is considered that this is because the chromaticity with a curing rate of 100% has little difference from the chromaticity before curing. In addition, in the sample 29 in which the chromaticity change parameter exceeds 2.0, some testers mistakenly think that the curing rate is 100% even if the curing rate is 25%. It was considered that this was because a considerable change in chromaticity occurred in the first half of the reaction and it was difficult to distinguish between the latter half of the reaction and the end of the reaction.

On the other hand, for samples 9, 10 and 18, there was one wrong answerer in the suitability confirmation test for curing judgment. In sample 9, although the value of the chromaticity change parameter was as small as 0.5 or less, the chromaticity difference ΔE exceeded 10 but was less than 20, so the color distinction was somewhat difficult to understand. Seem. In sample 10, the chromaticity difference ΔE was improved as compared with sample 9 and exceeded 20, but was less than 30, and the chromaticity change parameter was 2.0 or less but slightly larger than 1.0. Therefore, it seems that the color change in the latter half of the reaction was a little difficult to understand. In sample 18, the chromaticity difference ΔE is a sufficiently large value exceeding 30, but the chromaticity change parameter is 2.0 or less but a large value exceeding 1.0, so that the color change in the latter half of the reaction is a large value. It seems that it was a little difficult to understand.

On the other hand, for samples other than Sample 9, Sample 10, Sample 18, Sample 28 and Sample 29, that is, Samples 1 to 8, 11 to 17, 19 to 27, the number of incorrect answers was 0. For these samples, ΔE was 30 or more and the chromaticity change parameter was in the range of 0 to 1.0.

From these results, if the chromaticity difference ΔE is 10 or more and the chromaticity change parameter is in the range of 0 to 2.0, the suitability of the curing judgment may be slightly wrong, but the suitability is confirmed in many cases. It was found that if the chromaticity difference ΔE is 30 or more and the chromaticity change parameter is 1.0 or less, the suitability of the curing judgment can be confirmed without error.

Looking at the value of "ΔE / chromaticity change parameter", it was found that the above samples 9, 10 and 18 were in the range of 20 to 40. In addition, the value of "ΔE / chromaticity change parameter" was a value exceeding 40 in all the samples for which no one gave an incorrect answer. From this, it was found that the value of "ΔE / chromaticity change parameter" is preferably 20 or more, and particularly preferably 40 or more.

Comparing Samples 1 to 8, it can be seen that the change in chromaticity is particularly large because the chromaticity difference ΔE is 30 or more except for Sample 6. Further, since the initial chromaticity value of Sample 6 is (31.9, 48.4), it can be seen that the sample 6 is colored reddish. Since Sample 6 is a phosphoric acid-containing monomer, it is considered that the reason why the initial chromaticity was changed was that the photocurable composition became acidic. From this, it was found that it is preferable to use an acrylic monomer having no acidic group from the viewpoint that the initial color tone is colorless.

Samples 1 to 3 and 7 all had a second chromaticity difference of 20 or more. Therefore, it was found that the use of aliphatic, alicyclic, aromatic, and acrylamide-based monomers enhances not only visual discrimination but also spectrophotometric discrimination.

Sample 7 had a slightly higher maltens hardness than Samples 1 to 6. It is presumed that the acrylamide-based monomer promotes the curing reaction. From this, it was found that it is preferable to use an acrylic monomer excluding the acrylamide-based monomer when seeking flexibility, and to add an acrylamide-based monomer when increasing the hardness and seeking rigidity.

Comparing Samples 2 and 9 to 11, the value of ΔE was slightly smaller in the acylphosphine-based initiator and the intramolecular hydrogen abstraction type initiators Samples 9 and 10. It is considered that this is because these samples had a slightly yellowish initial chromaticity and were slightly close to the color after curing. From this, it was found that it is preferable to use an alkylphenone-based initiator or an oxime ester-based initiator as the radical polymerization initiator.

Comparing the magnitudes of the addition amounts of the leuco dyes in the samples 13 to 15, the chromaticity difference tended to become smaller as the addition amount of the leuco dyes decreased. The reason why the difference in chromaticity is small seems to be that the density of the dye is low. However, in the sample 12 in which the amount of the leuco dye added exceeds 1 part by mass, the chromaticity difference ΔE exceeds 30, but the value is smaller than that of the sample 15 which is 0.001 part by mass. The reason seems to be that when the amount of the leuco dye added is larger than the predetermined amount, the initial chromaticity becomes slightly yellowish, and the color approaches the color after curing. From this, it was found that the amount of the leuco dye added is preferably in the range of 0.005 to 1 part by mass. Of these, sample 12 has the largest _{second chromaticity difference ΔE 2.} Therefore, it was found that the addition amount exceeding 1 part by mass is preferable when the curing is judged by the spectrocolorimeter.

Comparing Sample 2 and Samples 19 to 23, the chromaticity change parameter of Sample 2 exceeded 0.1 in Samples 19 to 23 containing a colorant as compared with Sample 2 not containing a colorant. In each case, the chromaticity change parameter is 0.1 or less. From this, it was found that the visibility of the color was enhanced by including aluminum oxide, which is a white powder, as the colorant.

Further, since the value of the second chromaticity difference ΔE ₂ is particularly large in the samples 19, 20, 21 and 22, the amount of the colorant added is the total amount of the resin components in order to improve the distinctiveness by the spectrocolorimeter. It was found that 0.1 to 1.5 parts by mass is preferable with respect to (100 parts by mass).

Further, the initial color of Sample 22 and Sample 23 was reddish. This is because the pH of silica used in the present invention is 4.0 to 4.5 and the pH of aluminum oxide is 4.5 to 5.5. Therefore, a large amount is added to make the photocurable composition acidic. It seems that this is because the degree has increased. From this, it was found that the addition amount of such an additive is preferably about 5 parts by mass or less with respect to 100 parts by mass of the total amount of the resin components.

As a result of the immersion test with 1N hydrochloric acid, the chromaticity difference between Sample 28 and Sample 29 was as small as less than 20, but the chromaticity difference between Samples 1 to 27 was 20 or more. From this, it was found that by performing such a dipping test, it can be determined that the cured product can discriminate in chromaticity change.

11 Glass plate 12 Sim ring (spacer)
13 Through hole 14 Spectrophotometer 15 Photocurable composition 16 UV lamp

Claims (13)

1. Containing at least one acrylic compound selected from an acrylic monomer, an acrylic oligomer, and an acrylic polymer, a photoradical generator, and a leuco dye.
   The uncured color values (L ^* ₀ , a ^* ₀ , b ^* ₀ ) defined in the CIE1976 (L ^* , a ^* , b ^* ) color space described in JISZ8781-4 and the color values after curing (L ^*). _{The chromaticity difference ΔE from 100} , a ^* ₁₀₀ , b ^* ₁₀₀ ) is 10 or more.
   A photocurable composition in which the chromaticity change parameter represented by the following formula (1) is in the range of 0 to 2.0.
   

   

   [In the above formula (1), a ^* ₀ and b ^* ₀ indicate chromaticity a ^* value and b ^* value in the L ^* a ^* b ^* color space before curing, and a ^* ₅₀ and b ^* ₅₀ are. The chromaticity a ^* value and b ^{* value in the L *} a ^* b ^* color space at a curing rate of 50% are shown, and a ^* ₁₀₀ and b ^* ₁₀₀ are the chromaticity a in the L ^* a ^* b ^{* color space after curing. *} Value and b ^* value are shown. ]
2. The photocurable composition according to claim 1, which does not contain an acid generator.
3. The photocurable composition according to claim 1 or 2, wherein the acrylic compound is at least one of a monofunctional acrylic monomer, a bifunctional or higher acrylic oligomer, and a bifunctional or higher acrylic polymer.
4. The photocurable composition according to any one of claims 1 to 3, wherein the acrylic compound contains at least a monofunctional acrylic monomer and further contains a styrene-based elastomer.
5. The light according to claim 4, wherein the styrene-based elastomer is at least one of a high-molecular-weight styrene-based elastomer having a weight average molecular weight of 200,000 or more, an epoxy-modified styrene-based elastomer, and a styrene-based elastomer having an unsaturated bond in a soft segment. Curable composition.
6. The photocurable composition according to claim 4, wherein the styrene-based elastomer is a styrene-isobutylene-styrene block polymer.
7. The photocurable composition according to any one of claims 1 to 6, further comprising an inorganic powder.
8. A cured product obtained by curing the photocurable composition according to any one of claims 1 to 7, wherein ΔE changes by 20 or more when immersed in 1N hydrochloric acid at 70 ° C. for 120 hours.
9. The cured product according to claim 8, wherein the Martens hardness measured in the nanoindentation test is 0.005 to 50 N / mm ^2.
10. A sealing material which is a cured product of the photocurable composition according to any one of claims 1 to 7 or a cured product according to claim 8 or 9, wherein the compression set is 50% or less.
11. The cured product of the photocurable composition according to any one of claims 1 to 7, or the cured product according to claim 8 or 9, which is a protective material that covers an electronic element or wiring on a substrate.
12. A case having an opening, a lid that closes the opening,
    The sealing material according to claim 9, which is provided on at least one of the case and the lid body, is provided, and the sealing material is compressively deformed by fitting the case and the lid body to seal the opening liquid-tightly. Waterproof structure to stop.
13. A sealing material, a protective material, a masking material, an adhesive, and a step including at least a step of applying the photocurable composition according to any one of claims 1 to 7 and a step of irradiating the activation energy ray. A method for producing at least one cured product selected from anti-vibration materials.

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