CN113993912A

CN113993912A - Photocurable composition, cured product thereof, sealing material, protective material, waterproof structure, and method for producing cured product

Info

Publication number: CN113993912A
Application number: CN202080044270.6A
Authority: CN
Inventors: 花仓优; 爱泽眸
Original assignee: Polymatech Japan Co Ltd
Current assignee: Sekisui Polymatech Co Ltd
Priority date: 2019-08-29
Filing date: 2020-08-05
Publication date: 2022-01-28
Also published as: WO2021039320A1; JPWO2021039320A1; KR20220055451A

Abstract

Provided is a photocurable composition which, after curing, gives a color change that can be recognized before curing. A photocurable composition comprising at least one acrylic compound selected from acrylic monomers, acrylic oligomers and acrylic polymers, a photoradical generator and a leuco dye, and having a color according to CIE1976 (L) of JIS Z8781-4^*，a^*，b^*) Uncured colour value (L) defined in colour space^* ₀，a^* ₀，b^* ₀) And color value (L) after curing^* ₁₀₀，a^* ₁₀₀，b^* ₁₀₀) The chromaticity difference Delta E of 10 or more, and the chromaticity variation parameter expressed by the following formula (1) is in the range of 0-2.0.

In the above formula (1), a^* ₀And b^* ₀Denotes L before curing^*a^*b^*Chromaticity of color space a^*Value and b^*Value of a^* ₅₀And b^* ₅₀L represents a case where the curing rate is 50%^*a^*b^*Chromaticity of color space a^*Value and b^*Value of a^* ₁₀₀And b^* ₁₀₀Denotes L after curing^*a^*b^*Chromaticity of color space a^*Value and b^*The value is obtained.

Description

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

Technical Field

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

Background

The photocurable composition can be used as a photocurable composition for a gasket or the like by using a cured product which is liquid before application and is photocurable after application, and can be sufficiently cured after application to a desired portion. However, for example, if the composition is not cured due to a process error or is not sufficiently cured due to deterioration of a UV lamp, the uncured photocurable composition may come into contact with a contact body to contaminate the contact body, or if the composition is less cured, the composition may be directly formed into a product and the compression set may be reduced, thereby causing product defects.

Such a problem is that the appearance of the photocurable composition changes little before and after curing, and it is difficult to see immediately whether or not the curing is completed, and therefore a technique for determining the presence or absence of curing by changing the color tone before and after curing has been developed, and is described in, for example, international publication No. 2016/129568 (patent document 1).

Documents of the prior art

Patent document

Patent document 1: international publication No. 2016/129568

Disclosure of Invention

Problems to be solved by the invention

However, the technique described in international publication No. 2016/129568 (patent document 1) is not: the cured state of the photocurable composition corresponded to a color change, which indicated the completion of curing. Further, when the dye concentration is high, it is difficult for light such as ultraviolet rays to reach the inside, and there is a possibility that curability is impaired.

The present invention has been made to solve the above problems. That is, the photocurable composition is provided, colored with a low concentration of leuco dye, and after curing is completed, gives a color change that can be recognized as the color before curing.

Means for solving the problems

The photocurable composition and the cured product thereof of the present invention which achieve the above object are as follows. That is, the photocurable composition of the present invention comprises at least one acrylic compound selected from acrylic monomers, acrylic oligomers and acrylic polymers, a photoradical generator and a leuco dye in accordance with CIE1976 (L) described in JIS Z8781-4^*，a^*，b^*) Uncured colour value (L) defined in colour space^* ₀，a^* ₀，b^* ₀) And color value (L) after curing^* ₁₀₀，a^* ₁₀₀，b^* ₁₀₀) The chromaticity difference Delta E of (2) is 10 or more, and the chromaticity variation parameter expressed by the following formula (1) is in the range of 0 to 2.0.

Mathematical formula 1

[ in the above formula (1), a^* ₀And b^* ₀Denotes L before curing^*a^*b^*Chromaticity of color space a^*Value and b^*Value of a^* ₅₀And b^* ₅₀L representing a curing Rate of 50%^*a^*b^*Color of color spaceDegree a^*Value and b^*Value of a^* ₁₀₀And b^* ₁₀₀Denotes L after curing^*a^*b^*Chromaticity of color space a^*Value and b^*The value is obtained.]

The present invention contains at least one acrylic compound selected from acrylic monomers, acrylic oligomers, and acrylic polymers, a photo radical generator, and a leuco dye, and therefore, at least one acrylic compound selected from acrylic monomers, acrylic oligomers, and acrylic polymers can be cured by light irradiation, and the color can be changed before and after curing. Further, CIE1976 (L) described in JISZ8781-4 was used^*，a^*，b^*) Uncured colour value (L) defined in colour space^* ₀，a^* ₀，b^* ₀) And color value (L) after curing^* ₁₀₀，a^* ₁₀₀，b^* ₁₀₀) Since the difference Δ E between the chromaticity before curing and the chromaticity after curing is 10 or more, the difference between the chromaticity before curing and the chromaticity after curing is large.

Mathematical formula 2

[ in the above formula (1), a^* ₀And b^* ₀Denotes L before curing^*a^*b^*Chromaticity of color space a^*Value and b^*Value of a^* ₅₀And b^* ₅₀L represents a case where the curing rate is 50%^*a^*b^*Chromaticity of color space a^*Value and b^*Value of a^* ₁₀₀And b^* ₁₀₀Denotes L after curing^*a^*b^*Chromaticity of color space a^*Value and b^*The value is obtained.]

Furthermore, since the chromaticity variation parameter expressed by the above formula (1) is in the range of 0 to 2.0, the distance (color variation) in the latter half of the reaction becomes larger by at least half of the distance in the former half of the reaction, and thus, it is possible to prevent a misreading of the cured state due to the color variation. In the present invention, the chromaticity difference and the chromaticity variation parameter are values measured and calculated by the methods described in the examples.

The present invention can provide a photocurable composition containing no acid generator. The photocurable composition containing no acid generator does not cause an early color change in the leuco dye, and easily allows the curing of the acrylic monomer, acrylic oligomer, and acrylic polymer to be compatible with the reaction of the leuco dye.

The present invention can provide a photocurable composition in which the acrylic compound is at least one of a monofunctional acrylic monomer, a difunctional or higher acrylic oligomer, and a difunctional or higher acrylic polymer. The photocurable composition in which the acrylic compound is at least one of a monofunctional acrylic monomer, a difunctional or higher acrylic oligomer, and a difunctional or higher acrylic polymer can be suitably used as a sealing material, a protective material, and the like because a cured product obtained by curing the photocurable composition exhibits water repellency when it is adhered to an electronic component or a substrate.

The present invention provides a photocurable composition containing the acrylic compound at least a monofunctional acrylic monomer and a styrene-based elastomer. The photocurable composition containing the acrylic compound and the styrene elastomer can reduce the transparency of a cured body, improve the mechanical strength of the cured body and provide rubber elasticity.

The present invention provides 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 20 ten thousand or more, an epoxy-modified styrene-based elastomer, and a styrene-based elastomer having an unsaturated bond in a soft segment. The 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 20 ten thousand or more, an epoxy-modified styrene-based elastomer, and a styrene-based elastomer having an unsaturated bond in a soft segment can be suitably used as a sealing material, a protective material, or the like, since the compression set in the cured product can be reduced.

The present invention can provide a photocurable composition in which the styrene-based elastomer is a styrene-isobutylene-styrene block polymer. The photocurable composition in which the styrene-based elastomer is a styrene-isobutylene-styrene block polymer can be suitably used as a protective material such as a sealant because it can reduce the transparency of a cured product, can improve the mechanical strength thereof, and can impart rubber elasticity thereto.

The present invention can provide a photocurable composition further containing an inorganic powder. Since the photocurable composition containing an inorganic powder imparts thixotropy to the photocurable composition and has shape stability after application, the photocurable composition can be suitably used as a protective material such as a sealing material and a sealing material, and a masking material.

The present invention can provide a cured product obtained by curing any of the above-mentioned photocurable compositions having a Δ E change of 20 or more when immersed in hydrochloric acid having a concentration of 1 normal at 70 ℃ for 120 hours. A cured product obtained by curing any of the above photocurable compositions having a change in Delta E of 20 or more when immersed in hydrochloric acid of 1N concentration at 70 ℃ for 120 hours does not contain an acid generator. Such a cured product is preferable because residual acid has little risk of causing corrosion of an adherend such as a substrate, wiring, an electronic component, or a case.

The invention can be made into the product with the March hardness of 0.005-50N/mm determined by a nano indentation test²The cured product of (1). The Martensitic hardness measured by a nano indentation test is 0.005-50N/mm²The cured product of (2) is excellent in the balance among flexibility, stretchability and compressibility, and can be suitably used as a protective material such as a sealing material and a sealing material, and a masking material.

The present invention can be made into a cured product of any of the above-mentioned photocurable compositions or a sealing material having a compression set of 50% or less. The cured product of any of the above photocurable compositions or the cured product thereof has a compression set of 50% or less, and therefore can be used as a sealing material such as a gasket having a preferable sealing property.

The present invention can be made into a cured product of any of the above-mentioned photocurable compositions or a protective material for covering an electronic component or wiring on a substrate. The cured product of any of the photocurable compositions or the cured product of any of the photocurable compositions is a protective material that covers an electronic component or wiring on a substrate, and therefore has excellent flexibility and flexibility.

The present invention can provide a waterproof structure including a case having an opening, a lid that closes the opening, and the sealing member provided in at least one of the case and the lid, and the sealing member is compressed and deformed by fitting the case and the lid to seal the opening in a liquid-tight state (liquid-tight state). The present invention is a waterproof structure including a case having an opening, a lid for closing the opening, and the sealing material provided on at least one of the case and the lid, the sealing material being compressively deformed by fitting the case and the lid to seal the opening in a liquid state, and therefore, the waterproof structure is excellent in sealing performance.

The present invention provides a method for producing a cured product, comprising at least a step of applying any one of the above-mentioned photocurable compositions and a step of irradiating with an active energy ray; the cured body is at least one cured body selected from a sealing material, a protective material, a masking material, an adhesive, and a vibration-proof material. The method for producing a cured product of the present invention comprises at least a step of applying any one of the photocurable compositions and a step of irradiating the photocurable composition with an active energy ray, and the cured product is at least one selected from a sealing material, a protective material, a masking material, an adhesive, and a vibration isolating material, and therefore, these cured products can be easily produced.

Effects of the invention

The photocurable composition of the present invention gives a color change after the completion of photocuring that is recognizable before curing. The cured product of the photocurable composition of the present invention can be used in various applications such as adhesives, masking materials, gaskets, sealing materials, and sealing materials.

Drawings

Fig. 1 is an explanatory view for explaining a measurement procedure of chromaticity.

Detailed Description

[ Photocurable composition ]

The present invention will be described in detail based on embodiments. The photocurable composition of the present invention comprises a component containing at least one acrylic compound selected from acrylic monomers, acrylic oligomers and acrylic polymers, a photoradical generator and a leuco dye, and is represented by CIE1976 (L) of JIS Z8781-4^*，a^*，b^*) Uncured colour value (L) defined in colour space^* ₀，a^* ₀，b^* ₀) And color value (L) after curing^* ₁₀₀，a^* ₁₀₀，b^* ₁₀₀) The chromaticity difference Delta E of (2) is 10 or more, and the chromaticity variation parameter expressed by the following formula (1) is in the range of 0 to 2.0.

Mathematical formula 3

The term "before curing" of the photocurable composition means a state before a photocuring reaction such as ultraviolet irradiation is performed in a state where components for forming a photocured body are mixed, and the term "after curing" means a state where the photocurable composition is cured under conditions that allow the photocuring reaction to be sufficiently completed. However, in the following examples, the term "cured" will be used in view of the fact that sufficient curing cannot be recognizedUsed after conversion in cumulative light quantity of 15000mJ/cm²The condition (2) is a state in which the cured article is cured by irradiation with light for curing and the change in the peak height is substantially saturated when the infrared absorption spectrum is measured by the FT-IR method described later.

The photocurable composition can be obtained by CIE1976 (L) described in JISZ8781-4^*，a^*，b^*) Uncured colour value (L) defined in colour space^* ₀，a^* ₀，b^* ₀) And color value (L) after curing^* ₁₀₀，a^* ₁₀₀，b^* ₁₀₀) Since the chromaticity difference Δ E of (a) is 10 or more, the color change between the uncured state and the cured state is significant, and the difference between them can be recognized. When Δ E is 20 or more, the color change is larger, and therefore Δ E is preferably 30 or more, and the color change in the latter half of the reaction becomes larger even when the chromaticity change parameter is large, and therefore it is particularly preferable. On the other hand, if Δ E is less than 10, the color change before and after curing is small, and it is difficult to determine whether or not curing is completed.

The molecule of formula (1) is represented by a^*，b^*Coordinate (a) of uncured chromaticity on a plane^* ₀，b^* ₀) Coordinate of chromaticity (a) of cured state to a curing ratio of 50%^* ₅₀，b^* ₅₀) And the denominator of the formula (1) represents the distance from a^*，b^*Chromaticity coordinate (a) of cured state at 50% cure rate on plane^* ₅₀，b^* ₅₀) Coordinate (a) of chromaticity in a cured state after curing (curing rate 100%) (a)^* ₁₀₀，b^* ₁₀₀) The distance of (c). Therefore, the formula (1) represents the ratio of the distance (color change) when the curing rate is from 50% to 100% (after the reaction) to the distance (color change) when the curing rate is from 0% to 50% (before the reaction) of the photocurable composition. And uses it as a chromaticity variation parameter. Since the chromaticity variation parameter, which is the value of the formula (1), is in the range of 0 to 2.0, when the value is 2.0, the color variation in the latter half of the reaction is the smallest, and the closer to 0, the later half of the reaction isThe larger the color change of (b) is (or the smaller the color change of the former half of the reaction is), the more the distance (color change) of the latter half of the reaction is at least half or more of that of the former half of the reaction. From the viewpoint of a large color change in the latter half of the reaction, the chroma change parameter is preferably 0 to 1.0, and particularly preferably 0 to 0.5.

It is known that chromaticity varies depending on the curing of an object, but the degree of curing and the degree of color change of a photocurable composition are not always the same, and in general, color change often occurs to a large extent already at the initial stage of curing. Therefore, even if the curing is not completely completed, a color change occurs, and thus the curing is mistakenly considered to be performed. However, in the present invention, by dividing the state of color change into two in the state where the curing rate of the photocurable composition reaches 50%, the magnitude of color change in the latter half of the reaction when the remaining 50% is cured can be regarded as important, and the value of formula (1) is set to be in the range of 0 to 2.0, so that the case where the color change is largely completed in the former half of the reaction can be eliminated. Thus, a photocurable composition capable of preventing a misreading of the cured state due to a color change was obtained. Next, the components constituting the photocurable composition will be described.

The photocurable composition of the present invention comprises a composition containing at least an acrylic compound, a photoradical generator and a leuco dye, wherein the acrylic compound is at least one of an acrylic monomer, an acrylic oligomer and an acrylic polymer, and the acrylic monomer, the acrylic oligomer and the acrylic polymer are used as the same meaning as that of the (meth) acrylic monomer in the present specification and claims, and the acrylic monomer is used as a (meth) acrylic monomer including not only an acrylate monomer but also a methacrylate monomer. Likewise, "acrylic oligomer" is synonymous with (meth) acrylic oligomer and includes methacrylate oligomers in addition to acrylate oligomers. "acrylic polymer" is synonymous with (meth) acrylic polymer and is used in the sense of including methacrylate polymers in addition to acrylate polymers. Any of the acrylic monomer, acrylic oligomer, and acrylic polymer is a compound having a radical polymerizable group, and is classified by expressing the compound after radical polymerization as a "cured product". The photocurable composition can be prepared 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 cured by a photo radical polymerization initiator, and is a liquid having a low viscosity before curing. When the photocurable composition contains a styrene-based thermoplastic elastomer, the monofunctional acrylic monomer dissolves the styrene-based thermoplastic elastomer. The cured body of the monofunctional acrylic monomer adheres to an electronic component or a substrate, and exhibits water repellency and the like.

The monofunctional acrylic monomer contains a monofunctional highly polar monomer such as a monofunctional (meth) acrylamide monomer in addition to a monofunctional (meth) acrylate monomer. More specifically, the acrylic resin composition contains an aliphatic (meth) acrylate monomer, an alicyclic (meth) acrylate monomer, an ether (meth) acrylate monomer, a cyclic ether (meth) acrylate acrylic monomer, an aromatic (meth) acrylate monomer, a heterocyclic (meth) acrylate monomer, and the like, and further contains a polar group-containing (meth) acrylate monomer such as a hydroxyl group-containing (meth) acrylate monomer, a carboxyl group-containing (meth) acrylate monomer, an acrylamide-based monomer, a tertiary amino group-containing (meth) acrylate monomer, an imide (meth) acrylate monomer, a glycidyl group-containing (meth) acrylate monomer, a phosphoric group-containing (meth) acrylate monomer, and the like.

Specific examples of the monofunctional aliphatic (meth) acrylate monomer include aliphatic hydrocarbon (meth) acrylate monomers such as butyl acrylate, lauryl acrylate, stearyl acrylate, isostearyl acrylate, decyl acrylate, isodecyl acrylate, isononyl acrylate, and n-octyl acrylate. Lauryl acrylate is preferably used in combination with a styrene-based elastomer because of its extremely excellent solubility and flexibility.

By blending the monofunctional aliphatic (meth) acrylate monomer, the styrene-based thermoplastic elastomer is dissolved when blending the styrene-based thermoplastic elastomer, and the flexibility of a cured product obtained after curing the photocurable composition can be improved, and the mahalanobis hardness and young's modulus can be reduced, and the elongation at the time of cutting can be greatly improved.

Specific examples of the monofunctional alicyclic (meth) acrylate monomer include isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, cyclohexyl 3, 3, 5-trimethacrylate, and cyclohexyl 4-t-butyl-acrylate.

By blending the monofunctional alicyclic (meth) acrylate monomer, the styrenic thermoplastic elastomer can be dissolved when it is contained. The monofunctional alicyclic (meth) acrylate monomer can improve the adhesion of a cured body (for example, a sealing material) obtained by curing the photocurable composition, and can reduce adhesive residue when the cured body is peeled off from an adherend. Further, the cured body is tough and has an effect of improving the Young's modulus. In addition, moisture resistance and transparency can be improved by increasing the proportion of the component.

For the monofunctional aliphatic (meth) acrylate monomer and the alicyclic (meth) acrylate monomer, it is preferable to use acrylate monomers, respectively. This is because an acrylate monomer is superior to a methacrylate monomer in photocurability in many cases, and can be cured at a relatively low cumulative light amount.

When a monofunctional aliphatic (meth) acrylate monomer and a monofunctional alicyclic (meth) acrylate monomer are used, these components have adhesive strength, and thus the adhesive can be used as an adhesive. Further, since the sealant is in close contact with an adherend and can prevent entry of foreign matter and moisture, the sealant is also preferable as a sealant.

In addition, it is preferable to use an alicyclic (meth) acrylate monomer and an aliphatic (meth) acrylate monomer in combination. The aliphatic (meth) acrylate monomer can improve the flexibility of the cured product and greatly improve the elongation at the time of cutting, while the alicyclic (meth) acrylate monomer has the effect of strengthening the cured product and improving the tensile strength. Therefore, both of them are used in combination, whereby appropriate flexibility and hardness can be achieved at the same time.

Examples of the ether (meth) acrylate monomer include 2-butoxyethyl acrylate, ethoxydiglycol acrylate, phenoxyethyl acrylate, phenoxydiglycol acrylate, and nonylphenol ethylene oxide-modified acrylate.

Examples of the cyclic ether acrylate monomer include tetrahydrofurfuryl acrylate, methyl (2-methyl-2-ethyl-1, 3-dioxolan-4-yl) acrylate, and methyl (3-ethyl-3-oxetanyl) acrylate.

Examples of the aromatic acrylate 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 acrylate monomer include 1, 4-cyclohexanedimethanol monoacrylate, 2-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxyethyl acrylate.

Examples of the carboxyl group-containing acrylate monomer include ω -carboxyl-polycaprolactone monoacrylate, monohydroxyethyl phthalate, 2-acryloyloxyethylsuccinic acid, 2-acryloyloxyethylhexahydrophthalic acid and the like.

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

Examples of the tertiary amino group-containing (meth) acrylate monomer include 2- (dimethylamino) ethyl methacrylate (DMAEMA).

Examples of the imide-based (meth) acrylate monomer include N-acryloyloxyethylhexahydrophthalimide and N-acryloyloxyethyltetrahydrophthalimide.

Examples of the glycidyl group-containing (meth) acrylate monomer include glycidyl acrylate, glycidyl methacrylate, and butyl 4-hydroxyacrylate glycidyl ether.

Examples of the phosphoric group-containing (meth) acrylate monomer include 2-methylchlorooxyethyl acid phosphate and the like.

Among them, aliphatic acrylate monomers, alicyclic acrylate monomers, aromatic acrylate monomers, and acrylamide monomers are preferable from the viewpoint of obtaining a photocurable composition which hardly exerts an adverse effect on color change and has excellent visibility of color change accompanying curing.

In addition, from the viewpoint of improving storage stability of the photocurable composition and adhesion to a resin, it is preferable to use a monofunctional highly polar monomer, and among the monofunctional highly polar monomers, nitrogen-containing monomers such as an acrylamide-based monomer, a tertiary amino group-containing (meth) acrylate monomer, and an imide-based (meth) acrylate monomer are preferable. Particularly, the imide-based (meth) acrylate monomer is preferable from the viewpoint of improving adhesion to the polyimide film. From the viewpoint of improving adhesion to metals, a phosphoric group-containing (meth) acrylate monomer, a hydroxyl group-containing acrylate monomer, and a carboxyl group-containing acrylate monomer are preferable.

In the case where both the alicyclic (meth) acrylate monomer and the aliphatic (meth) acrylate monomer are contained, the mass ratio of the alicyclic (meth) acrylate monomer to the aliphatic (meth) acrylate monomer is preferably 4: 1-1: 4. by using both an alicyclic (meth) acrylate monomer and an aliphatic (meth) acrylate monomer, adverse effects on the change in color tone of the composition can be reduced, and metal adhesion can be improved.

When the monofunctional aliphatic (meth) acrylate monomer is more than 4 times the mass of the alicyclic (meth) acrylate monomer, there is a possibility that adhesive residue may occur when a cured product of the photocurable composition is peeled off, and the adhesive strength and moisture resistance may be low. On the other hand, if the amount is less than 1 in 4, the cured product tends to be hard, and the adhesiveness increases more than necessary with time, which may make peeling difficult. Further, the amount of the alicyclic (meth) acrylate monomer and the aliphatic (meth) acrylate monomer is adjusted to 3: 2-1: 4, a cured product (e.g., a sealant) having appropriate adhesiveness, a high elongation at cutting, and easy peeling can be obtained.

Polyfunctional acrylic monomer:

the polyfunctional acrylic monomer is also a component that is cured by a photo radical polymerization initiator. When a cured product of the photocurable composition is used as a gasket, a sealing material, or the like, a small amount of the photocurable composition can be blended for the purpose of adjusting hardness, reducing surface tackiness, or the like, but it is difficult to add the photocurable composition as an essential component or an auxiliary component of a monofunctional acrylic monomer. Examples of such a polyfunctional acrylic monomer include a polyfunctional aliphatic (meth) acrylate monomer, a polyfunctional highly polar monomer, and a cyclopolymerizable (meth) acrylic monomer.

Examples of the polyfunctional aliphatic (meth) acrylate monomer include difunctional aliphatic (meth) acrylate monomers, and examples of the difunctional aliphatic (meth) acrylate monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, and glycerin di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methyl-1, 5-pentanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, and the like. When a styrenic thermoplastic elastomer is added, a difunctional aliphatic hydrocarbon di (meth) acrylate monomer having a reactive group at both ends is preferable because of its relatively high compatibility with the soft segment.

As the multifunctional highly polar monomer, a (meth) acrylate monomer having a polar group and bismaleimide are included. Specific examples of the polar group-containing (meth) acrylate monomer include ethoxylated diisocyanuric acid di/tri (meth) acrylate, epsilon-caprolactone-modified tris- (2-acryloyloxyethyl) isocyanurate, 2-methylchlorooxyethyl acid phosphate, 2-hydroxy-3-acryloyloxypropyl methacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, bisphenol A diglycidyl ether acrylate adduct, and the like. From the viewpoint of improving the adhesion, a tris (2-hydroxyethyl) isocyanurate-based (meth) acrylate monomer is preferable.

Specific examples of bismaleimides include 4, 4 '-diphenylmethane bismaleimide, 4-methyl-1, 3-phenylene bismaleimide, 2-bis [4- (4-maleimidophenoxy) phenyl ] propane, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, 1, 6-bis (maleimide) hexane, and 1, 6' -bismaleimide- (2, 2, 4-trimethyl) hexane. Among them, aliphatic bismaleimides such as 1, 6-bis (maleimide) hexane and 1, 6' -bismaleimide- (2, 2, 4-trimethyl) hexane are preferable from the viewpoint of difficulty in inhibiting the compatibility and photocurability of the photocurable composition.

The cyclopolymerizable (meth) acrylic monomer includes alpha-allyloxymethylacrylate (AOMA), alpha-hydroxymethylacrylate dimer (RHMA-D), and the like. They can be used for viscosity adjustment of photocurable compositions due to their low viscosity, and can improve hardness, heat resistance and toughness while maintaining appropriate flexibility because they do not excessively increase the three-dimensional crosslinking density by curing. Among the above, α -allyloxymethylacrylate is preferable from the viewpoint of improving coating properties, improving heat resistance, and improving adhesion to glass and the like.

When a cured product of the photocurable composition is used as a gasket, a sealing material, or the like, when a bifunctional or higher acrylic monomer is blended, the photocurable composition or the cured product thereof preferably contains 5% by mass or less, more preferably 1% by mass or less. This is because if a large amount of the compound is added, the hardness may increase and the adhesiveness to an adherend may decrease.

Acrylic acid oligomer:

the acrylic oligomer is mainly a compound having a (meth) acrylic group in a weight average molecular weight of 1000 to 5 ten thousand. 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 a terminal or a side chain of a main chain other than acrylic. Examples thereof include polybutadiene type acrylic oligomer, acrylamide type oligomer, polyisoprene type acrylic oligomer, polyurethane type acrylic oligomer, polyester type acrylic oligomer, polyether type acrylic oligomer, epoxy type acrylic oligomer, bisphenol type acrylic oligomer, and novolak type acrylic oligomer.

Acrylic acid polymer:

the acrylic polymer is a compound having a (meth) acrylic group with a weight average molecular weight of 5 to 500 ten thousand. The acrylic polymer includes a polymer obtained by polymerizing the acrylic monomer or acrylic oligomer to a predetermined molecular weight, and a polymer obtained by adding a (meth) acrylic group to a compound other than an acrylic compound. For example, the former is a homopolymer obtained by polymerizing butyl acrylate. The latter includes compounds obtained by adding a (meth) acrylic group to a compound having a polybutadiene, acrylamide, polyisoprene, polyurethane, polyester, polyether, epoxy skeleton or the like, and specific examples thereof include polybutadiene-based acrylic polymers, acrylamide-based acrylic polymers, polyisoprene-based acrylic polymers, polyurethane-based acrylic polymers, polyester-based acrylic polymers, polyether-based acrylic polymers, epoxy-based acrylic polymers, bisphenol-based acrylic polymers, and novolak-type acrylic polymers.

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

Styrenic thermoplastic elastomer:

styrenic thermoplastic elastomers (also referred to as styrenic elastomers) are not essential ingredients. However, the styrene-based elastomer is soluble in an acrylic monomer or an acrylic oligomer in the photocurable composition, and can reduce transparency by its hard segment. Therefore, the change in color can be more easily visually recognized than when the photocurable composition is transparent. In addition, the styrene-based elastomer can improve the mechanical strength of a cured product obtained by curing an acrylic monomer or an acrylic oligomer, and can impart rubber elasticity (flexibility). Further, the compression set can be reduced, and the moisture permeability can be reduced.

Specific examples of the styrene-based elastomer include modified styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-ethylene-butylene-styrene block copolymers (SEBS), styrene-ethylene-propylene-styrene block copolymers (SEPS), styrene-isobutylene-styrene block copolymers (SIBS), styrene-ethylene-propylene-styrene block copolymers (SEEPS), epoxy-modified styrene-based elastomers, and the like.

Among the above-mentioned styrene-based elastomers, styrene-based elastomers having an unsaturated bond in a soft segment, such as styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene/isoprene copolymer-styrene block copolymer, can have a smaller compression set of a cured product thereof than the case of using a styrene-based elastomer having no unsaturated bond in a soft segment. Therefore, when the cured product is used as a gasket, a sealing material, or the like, the sealing property can be maintained for a long period of time. In addition, the viscosity of 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.

In addition, in the case of using an epoxy-modified styrene-based elastomer or a styrene-based elastomer having an unsaturated bond in a soft segment among the above styrene-based elastomers, the compression set of a cured product obtained after curing can be reduced as compared with the case of using a styrene-based elastomer not containing an epoxy-modified styrene-based elastomer or having an unsaturated bond in a soft segment, and the sealing property can be improved over a long period of time. Further, by containing an epoxy-modified styrene-based elastomer or a styrene-based elastomer having an unsaturated bond in a soft segment, the tackiness of the surface of a cured product can be reduced, and the compression set can be made less likely to deteriorate even when an inorganic powder is added.

Further, the styrene-based elastomer preferably includes a high molecular weight styrene-based elastomer. Here, the high molecular weight styrene elastomer means an elastomer having a weight average molecular weight of 20 ten thousand or more. The weight average molecular weight of the high-molecular-weight styrene-based elastomer is preferably 25 ten thousand or more, and more preferably 40 ten thousand or more. The upper limit is not particularly limited, and may be, for example, 100 ten thousand or less. The weight average molecular weight is determined using a GPC method (Gel Permeation Chromatography), and can be determined based on a calibration curve (standard curve) determined using standard polystyrene.

By containing a high-molecular-weight styrene-based elastomer, the compression set can be reduced as compared with the case of using a low-molecular-weight styrene-based elastomer having a weight average molecular weight of less than 20 ten thousand, and the sealing properties can be maintained for a long period of time when the cured product is used as a gasket, a sealing material or a sealing material. Further, by containing a high molecular weight styrene elastomer, bleeding of the plasticizer can be suppressed, and a cured product having high flexibility can be obtained by adding a much larger amount of the plasticizer.

The amount of the styrene-based elastomer added when blended is preferably 1 to 60% by mass, more preferably 2 to 45% by mass, in the photocurable composition. When the blending amount 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 or the like. On the other hand, if the amount exceeds 60 mass%, the viscosity of the photocurable composition tends to be high. When the content is 35% by mass or less, the fluidity is suitable and the coating is easy.

The amount of the high molecular weight styrene elastomer added is preferably 1 to 7% by mass, more preferably 2 to 5% by mass, in the photocurable composition. When the blending amount of the high-molecular-weight styrene-based elastomer is less than 1% by mass, there is a possibility that the mechanical strength is lowered. On the other hand, if the amount exceeds 10 mass%, the viscosity of the photocurable composition tends to be high.

Among the high-molecular-weight styrene elastomers, a high-molecular-weight styrene elastomer having a predetermined branch chain (typically, a branch chain radially extending from a core), which is called a star polymer, is preferably used. The high molecular weight styrene elastomer having such a predetermined branch can suppress entanglement of the main chains as compared with a linear high molecular weight styrene elastomer, and can suppress an increase in viscosity of the photocurable composition even when formulated at a relatively high concentration. Specifically, the high molecular weight styrene-based elastomer can be blended in a photocurable composition at a concentration of about 5 to 20 mass%.

Photo-radical generator:

the photo-radical generator generates radicals, and the acrylic monomer, acrylic oligomer, and acrylic polymer are cured by photo-radical polymerization. The photo-radical generating agent contains a photo-radical polymerization initiator.

Examples of the photo-radical polymerization initiator include photopolymerization initiators such as benzophenones, thioxanthones, acetophenones, acylphosphines, oxime esters, alkylphenones, and intramolecular dehydrogenation type. Among these, an acetylene ketone initiator or an oxime ester initiator is preferably used, particularly from the viewpoint of easily increasing the color difference.

Examples of the alkylphenones include 2, 2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-methylpropanone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-methylpropanone, 2-hydroxy-1- (4- (4- (2-hydroxy-2-methylpropanoyl) benzyl) phenyl) -2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, 2-benzyl-2- (dimethylamino) -4' -morpholinobutylbenzone, and mixtures thereof, 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one and the like.

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

Examples of the intramolecular dehydrogenation include a mixture of methyl benzoylformate, oxyphenylacetic acid-2-2-oxo-2-phenylacetoxyethoxyethyl ester, and oxyphenylacetic acid-2-2-hydroxyethoxyethyl ester.

Examples of the oxime esters (oxyphenylacetates) include 1- [4- (phenylthio) phenyl ] octane-1, 2-dione ═ 2- (O-benzoyloxime) and 1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] ethanone-1- (O-acetyloxime).

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

Leuco dye:

the leuco dye is generally a compound that develops color when it comes into contact with an acid, and in the present invention, functions to develop color after curing of the photocurable composition and to confirm completion of curing of the photocurable composition. Specific examples of the leuco dye include phthalides, fluoranes, thiazines, quinolines, lactones, lactams, triphenylmethanes, and the like, and the phthalides include indolylphthalides, diphenylmethanebenzenephthalates, monovinyleneththalides, divinylbenzenephthalates, diphenylmethane azaphthalides, and phenylindoleazaphthalides.

Examples of the phthalides include 3, 3-bis [4- (dimethylamino) phenyl ] phthalide, 3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, and 3, 3-bis (1-butyl-2-methyl-1H-indol-3-yl) phthalide.

As the fluoranes, 2 '-methyl-6' - (N-p-tolyl-N-ethylamino) spiro [ isobenzofuran-1 (3H), 9 '- [9H ] xanthen-3-one, 1, 3-dimethyl-6-diethylaminofluoran, 2-chloro-3-methyl-6-dimethylaminofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-dimethylanilinofluoran, 2- (2-chloroanilino) -6-dibutylaminofluoran, 3, 6-dimethoxyfluoran, 2-dichlorofluoran, 9' -methyl-N-ethylamino-6-methylanilino, 2-chloro-6-dimethylaminofluoran, and the like are exemplified, 3, 6-di-N-butoxyfluoran, 1, 2-benzo-6-diethylaminofluoran, 1, 2-benzo-6-dibutylaminofluoran, 1, 2-benzo-6-ethylisopentylaminofluoran, 2-methyl-6- (N-p-tolyl-N-ethylamino) fluoran, 2- (N-phenyl-N-methylamino) -6- (N-p-tolyl-N-ethylamino) fluoran, 2- (3' -trifluoromethylanilino) -6-diethylaminofluoran, 3-chloro-6-cyclohexylaminofluoran, 2-methyl-6-cyclohexylaminofluoran, 3-di (N-butyl) amino-6-methoxy-7-anilinofluoran, 3, 6-bis (diphenylamino) fluorane, methyl-3 ', 6' -bisdiphenylamino fluorane, chloro-3 ', 6' -bisdiphenylamino fluorane and the like.

Examples of thiazines include benzoyl methylene blue.

The lactams include rhodamine-B-anilino lactam, rhodamine- (p-nitroanilino) lactam, rhodamine- (o-chloroanilino) lactam, rhodamine- (o-nitroanilino) lactam and the like.

Examples of triphenylmethanes include colorless crystal violet (LCV).

Further, as the lactones, Crystal Violet Lactone (CVL), a diazorhodamine lactone derivative, and the like are cited as lactone derivatives of crystal violet.

Among them, various lactones having a lactone ring structure, phthalates, and fluorans are preferable from the viewpoint that the color tone is not easily changed after curing and the visibility of the presence or absence of curing is excellent even after a predetermined period of time has elapsed.

The amount of the leuco dye added may be 0.001 to 2 parts by mass, preferably 0.005 to 1 part by mass, based on 100 parts by mass of the acrylic monomer, acrylic oligomer and acrylic polymer. When the amount is 0.001 to 0.1 part by mass, the visibility of the presence or absence of curing can be improved when the curing is carried out at a thickness of 0.5mm or more. In addition, when the amount is 0.1 to 2 parts by mass, the mechanical and physical properties of the cured product of the photocurable composition can be improved. The effect of improving the mechanical physical properties can be observed in a region where the amount of the leuco dye added is slightly high, because the leuco dye promotes the radical reaction.

Plasticizer:

the photocurable composition is preferably added with a plasticizer as needed. The addition of the plasticizer can impart high flexibility to the cured product, and is suitable for use as a gasket or a sealing material. When a styrene-based elastomer is added as a plasticizer, the plasticizer is preferably compatible with the soft segment. Specific examples of the plasticizer include paraffin oil, olefin oil, naphthene oil, and ester plasticizers, and specific examples of the ester plasticizer include phthalate, adipate, trimellitate, polyester, phosphate, citrate, epoxidized vegetable oil, sebacate, azelate, maleate, and benzoate. Further, when the styrene-based elastomer is added, paraffin-based oil is preferable among them, and when paraffin-based oil is used, the effect of improving the elongation by physical crosslinking of the hard segment of the styrene-based elastomer is small, and this contributes to improvement of flexibility and improvement of compression set of the cured body.

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 the amount exceeds 30 parts by mass, the plasticizer may bleed out from the cured product.

Thixotropy-imparting agent:

the thixotropy-imparting agent is preferably added to the photocurable composition. By improving the thixotropy, the shape retention of the applied photocurable composition is improved. This can suppress dripping of the liquid when the photocurable composition is applied, and can improve the shape retention of the applied photocurable composition. For example, when a photocurable composition is formed into a three-dimensional object using a Dispenser (Dispenser), the photocurable composition can be directly cured in a shape coated with the photocurable composition, and thus the cured object is suitably used as a gasket material or a sealing material.

Specific examples of the thixotropy imparting agent include: inorganic thixotropy imparting agents composed of inorganic powders such as silica, alumina and titanium oxide; organic thixotropy-imparting agents such as hydrogenated castor oil, amide wax and carboxymethyl cellulose, and inorganic powders are preferred, and among them, silica is preferred. The reason is that the hydrogen ion index (pH) of the photocurable composition can be easily controlled by performing a predetermined surface treatment on the inorganic powder, and a substance having such a surface treatment can be easily obtained from silica in the inorganic powder. The amount of silica added is preferably 2 to 10 parts by mass per 100 parts by mass of the acrylic monomer, acrylic oligomer, and acrylic polymer (including the plasticizer when the plasticizer is contained). When the amount is less than 2 parts by mass, the effect of addition is difficult to obtain, and when the amount exceeds 10 parts by mass, the viscosity of the photocurable composition may excessively increase or the hardness of the cured product may become excessively hard.

The inorganic powder subjected to the surface treatment is preferably one having a hydrogen ion index of 3.0 to 11.0. Within the above range, the leuco dye undergoes a predetermined color change upon curing, and thus the visibility of the presence or absence of curing is excellent. Further, the hydrogen ion index is more preferably 3.6 to 5.5. This is because the visibility of the presence or absence of curing is improved. The hydrogen ion index is a hydrogen ion index measured for a dispersion liquid of an inorganic powder having a dispersion concentration of 4 mass% in pure water.

Colorant:

in order to make the color change more noticeable, a white inorganic filler may be added to the photocurable composition. By using a white inorganic filler, a small color change can be made more noticeable, and visibility can be improved. In addition, when a coating object with low brightness is coated with the photocurable composition, the visibility of the presence or absence of curing is improved.

Specific examples of the colorant include inorganic compounds such as alumina, titanium oxide, magnesium oxide, calcium carbonate, talc, bentonite, and montmorillonite. Among these, alumina is particularly preferable because it not only improves visibility of the presence or absence of curing, but also has an effect of improving coatability by imparting appropriate thixotropy.

In addition, the hydrogen ion index of the colorant is preferably 3.0 to 11.0, more preferably 3.6 to 5.5. Within this range, the effect of imparting thixotropy is obtained in the same manner as when the thixotropy-imparting agent is added, and a synergistic effect of thixotropy-imparting can be expected.

Other components:

various additives can be appropriately blended in the photocurable composition within the range not exceeding the gist of the present invention. Examples of the plasticizer and the thixotropy imparting agent include silane coupling agents, polymerization inhibitors, defoaming agents, light stabilizers, antioxidants, antistatic agents, thermally conductive fillers, and other functional fillers.

The viscosity of the photocurable composition is preferably 10 to 1000 pas, more preferably 20 to 300 pas at 25 ℃. When the pressure is less than 10Pa · s, liquid dripping is likely to occur when the dispenser is used to apply an electronic component or the like. On the other hand, if it exceeds 1000 pas, it becomes difficult to apply the coating material by a dispenser. Further, by setting the thickness to 20Pa · s or more, the shape retention property during the period from the coating to the curing is high, and by setting the thickness to 200Pa · s or less, fine distribution can be performed using a thinner needle bar. The viscosity can be selected from a value measured at a rotation speed of 10rpm and a measurement temperature of 25 ℃ by using a B-type rotary viscometer.

The thixotropic ratio of the photocurable composition is preferably 2 or more, more preferably 4 or more at 25 ℃. When the thixotropic ratio is 2 or more, the photocurable composition can be prevented from spreading before curing when applied, and therefore, the photocurable composition is preferably used as a sealing material, a gasket, or the like in addition to a sealing material. Further, by setting the thixotropic ratio to 4 or more, the spread can be reduced even in a photocurable composition having a particularly low viscosity, and a fine shape using a finer needle bar can be formed. The thixotropic ratio is a value calculated as a ratio of viscosity (1 rpm)/viscosity (10rpm)) by measuring the viscosity at the rotation speed of 1rpm and the rotation speed of 10rpm at a measurement temperature of 25 ℃ using a B-type rotational viscometer. The upper limit of the thixotropic ratio is not limited, but is preferably substantially 20 or less.

Cured product of photocurable composition:

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

As the sealing material, JISK 6253-3: 2012, the hardness is preferably 60 degrees or less, more preferably 40 degrees or less, still more preferably 20 degrees or less, and still more preferably 5 degrees or less. If the angle is 5 degrees or less, the sealing material can be used as a sealing material requiring an extremely low load. Further, the compression set of the cured product is preferably 50% or less. This is because long-term sealability can be ensured.

In addition, the cured product of the photocurable composition of the present invention preferably has a Martin hardness of 0.005 to 30N/mm as measured by a nanoindentation test²Within the range of (1). By setting the mahalanobis hardness within this range, predetermined flexibility and flexibility are provided, and the rubber composition is suitable for use as a sealing material such as a gasket, a protective material such as a masking material or a sealing material, an adhesive, and a vibration-proof material. The method for measuring the mahalanobis hardness can be specifically the method described in the examples.

The sealing material preferably has flexibility applicable to the flexible substrate and strength having repairability removable after being used for sealing the electronic component. When such properties are considered as the storage modulus E', the storage modulus is preferably in the range of 0.4 to 4.1 MPa. When the storage modulus E 'is 0.4MPa or more, the cured product of the photocurable composition is not easily broken and is easily repaired, and when the storage modulus E' is 4.1MPa or less, the cured product is easily peeled off from the fitting to be sealed disposed on the flexible substrate. When the long-term adhesion and protective effect are preferred over the repairability as a sealing material, the storage 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 peel off from the adherend by increasing the toughness, and the wiring can be prevented from being broken by bending by providing appropriate rigidity.

Further, as an adhesive or a reinforcing member applied to a boundary portion between a rigid substrate and a flexible substrate, the cured product of the photocurable composition preferably has mechanical strength such as young's modulus and mahalanobis hardness, which is required as appropriate for the application.

The above embodiments are illustrative of the present invention, and modifications of the embodiments, additions and combinations of known techniques, and the like can be made without departing from the spirit of the present invention, and these techniques are also included in the scope of the present invention.

Examples

The present invention will be described in more detail based on examples (comparative examples). Photocurable compositions having the compositions shown in the following tables and cured products obtained by curing these photocurable compositions were prepared, and samples 1 to 29 were prepared. These samples were then subjected to various tests.

[ TABLE 1 ]

[ TABLE 2 ]

[ TABLE 3 ]

[ TABLE 4 ]

< preparation of sample >

Sample 1 to sample 29:

acrylic monomer, acrylic oligomer, acrylic polymer, leuco dye and the like according to the sampleThe photocurable compositions of samples 1 to 29 were prepared by mixing the required styrene elastomers, thoroughly mixing them, and then mixing the additives and the photo-radical polymerization initiator. The illumination intensity of these photocurable compositions was 250mW/cm²And an accumulated light amount of 15000mJ/cm²The cured products of samples 1 to 29 were obtained by irradiating ultraviolet rays (LED light source having a wavelength of 365 nm) under the conditions of (1).

In the tables, lauryl acrylate was used as the acrylic monomer, isobornyl acrylate was used as the aliphatic acrylate, phenoxyethyl acrylate was used as the aromatic acrylate, 2-hydroxyethyl acrylate was used as the hydroxyl group-containing acrylate, ω -carboxy-polycaprolactone monoacrylate was used as the carboxyl group-containing acrylate, 2-chlorooxyethyl acid phosphate was used as the phosphoric acid group-containing acrylate, acryloylmorpholine was used as the amide group-containing acrylate, 2- (dimethylamino) ethyl methacrylate was used as the amino group-containing acrylate, and 1, 9-nonanediol diacrylate was used as the difunctional aliphatic acrylate.

Further, as the acrylic polymer, an acrylic polymer of an acrylic skeleton ("RC 500(XX 067C)" (trade name), manufactured by Kaneka corporation) was used.

As a photo radical polymerization initiator, 2-hydroxy-2-methyl acetone was used as an alkyl benzophenone initiator, bis (2, 4, 6-trimethylbenzoyl) phenylphosphorous oxide was used as an acylphosphorous oxide, a mixture of oxyphenylacetic acid-2-2-oxo-2-phenylacetoxyethoxyethylethyl ester and oxyphenylacetic acid-2-2-hydroxyethoxyethyl ester was used as an intramolecular dehydrogenation type, and 1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] ethanone-1- (O-acetyloxime) was used as an oxyphenylacetic acid ester.

As the leuco dye, 2 ' -methyl-6 ' - (N-p-tolyl-N-ethylamino) spiro [ isobenzofuran-1 (3H), 9 ' - [9H ] xanthen ] -3-one ("RED 520" (trade name), manufactured by fujishan chemical industry co., ltd.), 3-bis (p-dimethylaminophenyl) -6-dimethylaminobenzophthalein ("Crystal Violet Lactone (CVL)", manufactured by fujishan chemical industry co., ltd.) and "leuco crystal violet" ((trade name), manufactured by tokyo chemical industry co., ltd.) were used for the fluorans, and as the triphenylmethane, respectively.

As the styrenic thermoplastic elastomer, a styrene-isobutylene-styrene triblock copolymer ("SIBSTAR 102T" (trade name), manufactured by Kaneka corporation) was used.

A photoacid generator ("CPI-210S" (trade name), available from San-Apro Co., Ltd.) was used as an additive, and silica ("AEROSIL 200" (trade name), available from Nippon AEROSIL Co., Ltd., specific surface area of about 200 m) was used as a viscosity modifier and a thixotropy-imparting agent²Hydrophilic fumed silica in terms of a/g), and alumina ("AluC" (trade name), produced by AEROSIL corporation of Japan, fumed alumina) was used as a colorant.

< various tests and evaluations >

The properties of the photocurable composition and the cured product thereof were evaluated by conducting various tests described below on the respective samples.

Calculation of cure rate when converted from photocurable composition to cured body:

when the photocurable composition is in an intermediate state from an uncured state, i.e., a state in which the cure rate is 0% to a completely cured state, i.e., a state in which the cure rate reaches 100%, the degree of curing, i.e., the cure rate, is several percent as measured by the FT-IR method. The FT-IR method records infrared absorption spectra with the longitudinal axis as absorbance for the uncured body and cured product, and reads from each spectrum a variable peak (from 820 cm) due to chemical bonds decreasing with the curing reaction^-1To 780cm^-1) And internal standard peak (1730 cm)^-1) The area of (2) is calculated from the values of the uncured body and the cured product, and the cure rate of the sample with an undetermined cure rate is determined.

More specifically, the area of the variable peak of the sample to be measured is denoted by a, the area of the internal standard peak is denoted by B, and the ratio R of the areas is obtained as a/B. Here, the R value of the uncured body was Ru, and the cured product (at the cumulative light amount of 15000 mJ/cm)²A cured product produced by irradiating ultraviolet rays under the conditions of (1) is set to the R valueRc, the reduction rate Dc (%) of the Rc value with respect to the Ru value, i.e., the reduction rate of the R value of the cured product, can be determined by the following formula (2).

Dc ═ 1-Rc/Ru). times.100. formula (2)

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

D ═ 1-R/Ru). times.100. formula (3)

The cure rate C (%) of the sample for which the cure rate was obtained can be obtained by comparing the D value of the sample with the Dc value. That is, it can be obtained from the following formula (4).

C ═ D/Dc × 100. formula (4)

Determination of the curing rate by the FT-IR is described in "measurement of curing rate of chemically reactive resin (UV curing, heat curing, and moisture curing) and its practice to practical application of adhesives, sealing materials, and paints (suzuo shou), information agency (ltd).

Measurement of color intensity:

the measurement of the chromaticity was performed as follows. First, as shown in FIG. 1A, 2 transparent glass plates 11 having a thickness of 1mm were prepared, and 0.1mm of peeled PET (HSPX) (not shown) was stuck to one surface of 1 of the transparent glass plates 11. A spacer ring (spacer) 12 having a thickness of 1mm and having a circular through hole 13 having a diameter of 10mm was disposed on the other glass plate 11 to which PET was not bonded, and the spacer ring was sandwiched between 2 glass plates by placing the other glass plate so that the spacer ring was opposed to PET.

Next, the chromaticity of the calibration white plate as a reference was measured. (measurement of blank, FIG. 1B). Next, the photocurable composition of each sample was applied to the inside of the through hole 13 of the spacer ring 12, and as shown in fig. 1C, the chromaticity of the photocurable composition before curing entering the through hole was measured. At this time, a correction white plate (not shown) is disposed below the lower glass plate 11. The photocurable composition was sealed in 2 glass plates to protect it from oxygen in the air. Then, as shown in FIG. 1D, a UV lamp (manufactured by Songhua corporation, "AicurUJ 30", wavelength 365nm,illuminance of 250mW/cm²) The photocurable composition 15 is irradiated with ultraviolet light for a predetermined time. Finally, as shown in FIG. 1E, the chromaticity of the cured product of the photocurable composition after curing was measured by a spectrophotometer (manufactured by Colour Techno System, Ltd. "convenient spectrophotometer JX 777") 14. In the actual measurement of the chromaticity, the ultraviolet irradiation time at which the curing rate became 50% was previously obtained for each sample, and the chromaticity was obtained for the sample irradiated with the ultraviolet light for that time. The values of the formula (1) as the chromaticity change parameters were calculated from the chromaticity of the uncured, cured rate of 50% and cured end (cured rate of 100%) of each sample, and the results are shown in the tables.

Measurement of color difference:

initially, the same sample as the sample used for the measurement of the chromaticity is prepared. Next, the samples were placed on a calibration white plate, and the hue of each sample was visually compared with the color of a color chart of a color sample "PANTONE uncoated chips" (manufactured by PANTONE corporation), and the closest color number was recorded. Next, the chromaticity of each color chart was measured by the spectrocolorimeter. The chromaticity difference Δ E was calculated from the chromaticities corresponding to the colors of the uncured and cured samples (curing ratio 100%) obtained in this way, and the results are shown in the tables.

In addition, the sample used for measuring the chromaticity is placed on a correction white plate, and a second chromaticity difference Δ E is obtained from the chromaticity obtained by measuring the chromaticity of each sample with a spectrocolorimeter₂。

In the present invention, the chromaticity difference Δ E is simply referred to as a "chromaticity difference Δ E", and the chromaticity difference Δ E is referred to as a "second chromaticity difference Δ E" in the case of the latter₂". The chromaticity difference Δ E is a value that faithfully reflects a visually recognized color change. Therefore, if the chromaticity difference Δ E is large and the chromaticity variation parameter is within a predetermined range, it means that it is easy to visually recognize before curing and after photocuring is completed.

On the other hand, for example, in the production process, a spectrocolorimeter or colorimetry is usedIn the special case of inspecting the state of curing, the second difference in color Δ E is preferably₂Is 10 or more, more preferably 20 or more. In this case, the chromaticity difference Δ E may be replaced with the second chromaticity difference Δ E₂Only the second chromaticity difference Δ E₂It is preferably 10 or more. Further, the chromaticity difference Δ E and the second chromaticity difference Δ E are preferable₂Both are 10 or more, more preferably 20 or more. In this case, it is possible to cope with both the inspection by the spectrocolorimeter and the visual inspection, and it is also possible to prevent inadvertent contact with the uncured photocurable composition, thereby improving the working safety of the worker. Further, the chromaticity difference Δ E of the color chart selected by visual observation and the chromaticity difference Δ E obtained by the spectrocolorimeter were used₂In most cases, the correlation is correlated, but the values deviate from the correlation in some samples. The reason for this is not clear, but it is considered that the chromaticity measured by spectrophotometry and the chromaticity visually perceived are different depending on the sample in which the reflected color and the transmitted color are in a complementary relationship, the degree of light diffusibility, and the like.

Calculation of Δ E/colorimetric Change parameter:

in each table, a value obtained by dividing the chromaticity difference Δ E by the chromaticity variation parameter is shown. The larger the chromaticity difference and the smaller the chromaticity variation parameter (i.e., the larger the chromaticity variation in the latter half of the reaction) the larger the value. Therefore, it is expected that this value correlates with the identifiability of the curing state.

Confirmation test of adequacy of curing judgment:

for each of the above samples, a test piece before curing (curing rate 0%), a curing rate 25%, a curing rate 50%, a curing rate 75%, and after curing (curing rate 100%) was prepared and used in the present test. After the test piece before curing and the test piece after curing were observed for 30 seconds, the test pieces were hidden, and the 5 test pieces with different curing states were observed randomly over 3 minutes, and it was answered whether the test piece was a test piece with a curing rate of 100% or a test piece other than the test piece. This test was performed for 5 persons for one sample (i.e., 5 test subjects), and the number of persons who responded incorrectly was measured. The results are shown in the tables.

Ma hardness (N/mm)²)：

A nanoindentation test of the cured body of each sample was performed using a nanoindenter (manufactured by ELIONIX, ENT-2100). The test piece used a cured product obtained by applying a photocurable composition to a glass plate having a thickness of 1mm so as to have a thickness of 200 μm and using an LED having a wavelength of 365nm at an illuminance of 250mW/cm²And an accumulated light amount of 15000mJ/cm²Under the conditions of (3) and (3) irradiating ultraviolet rays to cure the composition. Then, the mohs hardness of the cured product was measured using the indenter under conditions of a maximum indentation load of 0.1mN and an indentation speed of 0.01 mN/sec.

Immersion test with 1 normal hydrochloric acid:

the cumulative light quantity irradiated to each sample was 15000mJ/cm²The ultraviolet ray of (2) was used to obtain a cured product of each sample having a thickness of 1 mm. Then, 0.2g of a test piece was cut out of the cured product, immersed in 10g of 1N hydrochloric acid, and allowed to stand at 70 ℃ for 120 hours. Then, after 120 hours, the test piece was removed and the surface was lightly wiped to remove moisture. The test piece thus obtained was visually compared with a color chart of a color sample "PANTON European fashion chips" (manufactured by PANTONE Co., Ltd.), and the closest color number was recorded. Then, the chromaticity of each color chart was measured by the spectrocolorimeter, and the chromaticity difference was calculated from the chromaticity of the test piece after the test and the chromaticity of the test piece before the test of each sample, and the chromaticity difference Δ E after the immersion test of each table was calculated₃Column (c) shows the result.

< analysis of test results >

As a result of the test for confirming the adequacy of the curing judgment, the number of test subjects who erroneously answered at a curing rate of 100 or 75% or 100% is large for the sample 28 having Δ E less than 10. This is considered to be because the difference between the chromaticity at the curing rate of 100% and the chromaticity before curing is small. In addition, in the sample 29 having the chromaticity variation parameter exceeding 2.0, even if the curing rate is 25%, a tester which mistakenly considers the curing rate to be 100% appears, and there is a wrong answer. This is considered to be because a considerable change in chromaticity occurred in the first half of the reaction, and it was difficult to distinguish the case from the second half of the reaction and the case where the reaction was completed.

On the other hand, the test for confirming the adequacy of the curing judgment of the samples 9, 10 and 18 was 1 person. Although the value of the chromaticity variation parameter of sample 9 is smaller than 0.5, the chromaticity difference Δ E is smaller than 10 but smaller than 20, and it is considered that the difference in color is somewhat difficult to distinguish. The chromaticity difference Δ E of sample 10 was improved by more than 20 but less than 30 as compared with sample 9, and the chromaticity change parameter was also a slightly larger value of 2.0 or less but more than 1.0, and therefore, it was considered that the change in color in the latter half of the reaction was slightly indistinguishable. The chromaticity difference Δ E of sample 18 was a sufficiently large value exceeding 30, and the chromaticity change parameter was 2.0 or less but a large value exceeding 1.0, and therefore, it was considered that the change in color in the latter half of the reaction was slightly indistinguishable.

On the other hand, the number of wrong answers for samples 1 to 8, 11 to 17, and 19 to 27 other than sample 9, sample 10, sample 18, sample 28, and sample 29 was 0. For these samples, the Δ E of any sample was 30 or more, and the chromaticity variation parameter fell within the range of 0 to 1.0.

From these results, if the chromaticity difference Δ E is 10 or more and the chromaticity variation parameter is in the range of 0 to 2.0, the adequacy can be confirmed in most cases, although some errors may occur in the confirmation of adequacy of the curing judgment, and if the chromaticity difference Δ E is 30 or more and the chromaticity variation parameter is 1.0 or less, the adequacy of the curing judgment can be confirmed without errors and with reliability.

When the "Δ E/chromaticity variation parameter" is observed, the samples 9, 10 and 18 are within the range of 20 to 40. In addition, for the samples of the person who did not respond to the error, the value of "Δ E/chromaticity variation parameter" exceeded 40. From this, it is understood that the value of "Δ E/chromaticity variation parameter" is preferably 20 or more, and particularly preferably 40 or more.

Comparing samples 1 to 8 shows that the chromaticity change is particularly large because the chromaticity difference Δ E is 30 or more, except for sample 6. The initial colorimetric values of sample 6 were (31.9, 48.4), and it was found that the sample was red-colored. Since sample 6 is a phosphorus acid monomer, the reason for the initial change in chromaticity is considered to be that the photocurable composition is acidic. From this fact, it is found that an acrylic monomer having no acidic group is preferably used from the viewpoint that the initial color tone is colorless.

The second chromaticity differences of the samples 1 to 3 and 7 were all 20 or more. Therefore, it is found that not only visibility is improved but also visibility of a spectrocolorimeter is improved by using aliphatic, alicyclic, aromatic and acrylamide monomers.

In comparison with samples 1 to 6, sample 7 has a slightly higher martensitic hardness. It is presumed that the acrylamide-based monomer promotes the curing reaction. From this fact, it is found that when flexibility is sought, an acrylic monomer excluding an acrylamide monomer is used, and when rigidity is sought after by increasing hardness, it is preferable to add an acrylamide monomer.

When samples 2 and 9 to 11 are compared, the Δ E values of samples 9 and 10, which are acylphosphine-based initiators and intramolecular dehydrogenation-type initiators, are slightly smaller. This is believed to be because the initial chroma of these samples was slightly yellowish and somewhat close to the color after curing. From these results, it is found that the radical polymerization initiator is preferably an alkyl ketone initiator or an oxime ester initiator.

When the amounts of the leuco dyes added in the samples 13 to 15 were compared, the chromaticity difference tended to decrease as the amount of the leuco dye added was smaller. The reason why the chromaticity difference becomes small is considered to be that the concentration of the dye becomes low. However, in sample 12 in which the amount of the leuco dye added exceeds 1 part by mass, the chromaticity difference Δ E exceeds 30, but is not smaller than that in sample 15 in which the amount is 0.001 part by mass. The reason for this is considered to be that if the amount of the leuco dye added is more than a predetermined amount, the initial hue is slightly yellowish, and thus the hue approaches the color after curing. From this, it is found that the addition amount of the leuco dye is preferably in the range of 0.005 to 1 part by mass. Further, among them, the second chromaticity difference Δ E of the sample 12₂And max. Therefore, it is found that the amount of addition exceeding 1 part by mass is preferable in the case of determination of curing by a spectrocolorimeter.

When sample 2 and samples 19 to 23 are compared, the chromaticity change parameter of sample 2 exceeds 0.1 compared with sample 2 containing no colorant, and the chromaticity change parameter of samples 19 to 23 containing a colorant is 0.1 or less. From this, it is found that the visual recognizability of the color tone can be improved by containing the white powder of alumina as the colorant.

In particular, the second chromaticity differences Δ E of the samples 19, 20, 21, and 22₂It is known that the amount of the colorant added is preferably 0.1 to 1.5 parts by mass based on the total amount (100 parts by mass) of the resin components in order to improve the visibility of the spectrocolorimeter.

Further, samples 22 and 23 had an initial color tone of red. This is considered to be because the acidity of the photocurable composition increases when a large amount of silica and alumina are added to the composition, respectively, at a pH of 4.0 to 4.5 and a pH of 4.5 to 5.5, respectively. From this, it is found that the amount of such additives added 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 1 n hydrochloric acid, the chromaticity differences of the samples 28 and 29 were as small as less than 20, and the chromaticity differences of the samples 1 to 27 were all 20 or more. From this, it was found that the cured product was judged to be a cured product that could be recognized for a change in chromaticity by performing such an immersion test.

Description of the reference numerals

11 glass plate

12 gasket ring (gasket)

13 through hole

14-spectral colorimeter

15 Photocurable composition

16 UV lamp.

Claims

1. A photocurable composition comprising at least one acrylic compound selected from acrylic monomers, acrylic oligomers and acrylic polymers, a photoradical generator and a leuco dye,

using CIE1976 (L) described in JISZ8781-4^*，a^*，b^*) Uncured colour value (L) defined in colour space^* ₀，a^* ₀，b^* ₀) And color value (L) after curing^* ₁₀₀，a^* ₁₀₀，b^* ₁₀₀) The chromaticity difference Delta E of (A) is 10 or more,

the chromaticity variation parameter expressed by the following formula (1) is in the range of 0 to 2.0,

mathematical formula 1

2. The photocurable composition according to claim 1, wherein,

no 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 difunctional or higher acrylic oligomer, and a difunctional 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 a styrenic elastomer.

5. The photocurable composition according to claim 4, wherein,

the styrene elastomer is at least one of a high-molecular-weight styrene elastomer having a weight average molecular weight of 20 ten thousand or more, an epoxy-modified styrene elastomer, and a styrene elastomer having an unsaturated bond in a soft segment.

6. The photocurable composition according to claim 4, wherein,

the styrenic elastomer is a styrene-isobutylene-styrene block polymer.

7. The photocurable composition according to any one of claims 1 to 6, wherein,

also contains inorganic powder.

8. A cured product obtained by curing the photocurable composition according to any one of claims 1 to 7, which has a Δ E change of 20 or more when immersed in 1N hydrochloric acid at 70 ℃ for 120 hours.

9. The cured body according to claim 8,

the Martensitic hardness measured by a nano indentation test is 0.005-50N/mm²。

10. A sealing material which is a 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 and has a compression set of 50% or less.

11. A protective material which is a 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 and covers an electronic component or wiring on a substrate.

12. A waterproof structure is provided with:

a case having an opening;

a cover for blocking the opening; and

the sealing material according to claim 9, which is provided on at least one of the case and the lid,

the sealing material is compressed and deformed by fitting the case and the lid, and seals the opening in a liquid-tight state.

13. A method for producing a cured product, which is at least one cured product selected from a sealing material, a protective material, a masking material, an adhesive, and a vibration-proof material,

the method for producing the cured body at least comprises: a step of applying the photocurable composition according to any one of claims 1 to 7; and irradiating the substrate with an active energy ray.