JP7400844B2 - Photocurable resin composition and cured product - Google Patents

Description

The present invention relates to a photocurable resin composition and a cured product thereof, and more particularly to a photocurable resin composition and a cured product thereof used for adhesion of a cover glass or an LCD (liquid crystal) module to a touch sensor.

In recent years, touch panels for smartphones, car navigation systems, tablet terminals, and the like have spread rapidly in the market. Current touch panels are composed of a touch sensor, an LCD (liquid crystal) module, a cover glass, etc., and by filling the air gap between the touch sensor and the module with an optically transparent adhesive, it improves visibility and absorbs shock. It is known to have excellent sex. Examples of such optically transparent adhesives include the adhesive composition described in Patent Document 1 below.

Japanese Patent Application Publication No. 2009-24098

However, the pressure-sensitive adhesive composition described in Patent Document 1 gradually becomes colored over time in a severe high-temperature environment. In contrast to conventional photocurable resin compositions used as optically transparent adhesives, we have developed a technology that maintains its tackiness and remains transparent without yellowing or other discoloration even when used for long periods of time in high-temperature environments. They are required to be able to sustain their sexuality.

An object of the present invention is to provide a photocurable resin composition that has sufficient adhesiveness and can maintain sufficient transparency in a high-temperature environment, and a cured product thereof.

As a result of studies by the present inventors, when a (meth)acrylic polymer obtained by polymerizing a (meth)acrylic monomer using a nitrile-based azo polymerization initiator is used as a constituent component of the resin composition. It was discovered that radicals and colored substances (ketene imine, etc.) generated from residual polymerization initiators contained in (meth)acrylic polymers promote resin deterioration. Based on these findings, the present inventors discovered the following photocurable resin composition and cured product thereof.

The photocurable resin composition according to the present invention contains a (meth)acrylic polymer, a monomer, a photopolymerization initiator, and an antioxidant, and the (meth)acrylic polymer contains a non-nitrile azoester polymerization initiator. This is a polymer obtained by polymerizing a (meth)acrylic monomer.

According to the photocurable resin composition according to the present invention, sufficient transparency can be maintained in a high temperature environment while maintaining adhesiveness. In particular, the photocurable resin composition of the present invention can maintain transparency and prevent yellowing even when used for a long time in a high-temperature environment. Such a photocurable resin composition has excellent adhesiveness, transparency, and weather resistance, and can be used as an optically transparent adhesive.

The photocurable resin composition according to the present invention has a content of the (meth)acrylic polymer based on 100 parts by mass of the total amount of the (meth)acrylic polymer, the crosslinking agent, the monomer, and the photoinitiator. is 30 to 65 parts by mass, the content of the crosslinking agent is 1.0 to 5.0 parts by mass, the content of the monomer is 30 to 58 parts by mass, and the content of the photoinitiator is The amount may be 0.005 to 5.0 parts by mass.

The cured product according to the present invention is a cured product of the photocurable resin composition according to the present invention.

According to the present invention, it is possible to provide a photocurable resin composition that has sufficient adhesiveness and can maintain sufficient transparency in a high-temperature environment, and a cured product thereof. In the present invention, when the resin composition is held at 95° C. for 1000 hours, the YI value (coloring index) can be maintained at, for example, 1.0 or less.

Embodiments of the present invention will be described in detail below. In this specification, "(meth)acrylic" means at least one of acrylic and methacrylic, "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid, and "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid. "Meth)acrylate" means at least one of acrylate and methacrylate. In addition, if there are multiple substances corresponding to each component in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. .

<Photocurable resin composition>
The photocurable resin composition (photocurable (meth)acrylic resin composition) according to the present embodiment includes (A) (meth)acrylic polymer (sometimes referred to as "component (A)"), (B) crosslinked agent (sometimes referred to as "component (B)"), (C) monomer (sometimes referred to as "component (C)"), (D) photoinitiator (photopolymerization initiator, sometimes referred to as "component (D)") )) and (E) an antioxidant (sometimes referred to as "component (E)"). Component (A) is a polymer obtained by polymerizing a (meth)acrylic monomer using a non-nitrile azoester polymerization initiator. The photocurable resin composition according to this embodiment can be used as an optically transparent adhesive.

[Component (A): (meth)acrylic polymer]
The photocurable resin composition according to this embodiment contains a (meth)acrylic polymer. Conventional photocurable resin compositions include rubber-based compositions and polyether-based compositions, but these have high elastic modulus and curing shrinkage, and may cause unevenness in liquid crystal display when applied to touch panels, etc. It has become a challenge. On the other hand, in this embodiment, by using a (meth)acrylic polymer that is flexible and has a low elastic modulus and curing shrinkage rate, it has sufficient adhesive strength and does not yellow even when used for a long time in a high temperature environment. It is possible to provide an optical pressure-sensitive adhesive and an optical pressure-sensitive adhesive cured product that can maintain transparency without causing coloration.

The (meth)acrylic polymer in this embodiment is a polymer obtained by polymerizing a (meth)acrylic monomer using a polymerization initiator, and has a structural unit derived from the (meth)acrylic monomer. Examples of (meth)acrylic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and octyl (meth)acrylate. (Meth)acrylic acid alkyl ester monomers such as acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate; (meth)acrylate, maleic acid, maleic anhydride, itaconic acid, fumaric acid, fumaric anhydride Carboxy group-containing monomers such as acids and their anhydrides; hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, polyethylene glycol (meth)acrylate, etc. Examples include monomers. These monomers may be used alone or in combination of two or more.

As the (meth)acrylic monomer, (meth)acrylic acid alkyl ester monomers (2-ethylhexyl acrylate, etc.) and hydroxy group-containing monomers (2-hydroxyethyl acrylate, etc.) are preferred. The ratio of the (meth)acrylic acid alkyl ester monomer is preferably 50 to 95% by mass, more preferably 55 to 90% by mass, and 60 to 95% by mass, more preferably 55 to 90% by mass, based on the total amount of the (meth)acrylic acid alkyl ester monomer and the hydroxy group-containing monomer. More preferably 90% by mass. When the ratio is 50% by mass or more, the cohesive force is excellent, and when the ratio is 95% by mass or less, the adhesive strength and weather resistance are further excellent.

As a polymerization initiator for obtaining a (meth)acrylic polymer, a non-nitrile azo ester polymerization initiator, which is a polymerization initiator having a non-nitrile structure (a polymerization initiator not containing a nitrile structure), is used. Examples of non-nitrile azo ester polymerization initiators include dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2' -azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(2,4,4-trimethylpentane), and the like. The amount of the polymerization initiator is preferably selected appropriately depending on the desired molecular weight and physical properties.

Among non-nitrile azo ester polymerization initiators, dimethyl 2,2'-azobis(2-methylpropionate), an azo polymerization initiator, has excellent polymerization activity and low hydrogen abstraction ability, so it has a stable molecular weight. It is particularly preferred because it can be polymerized and can easily maintain transparency even in a high-temperature environment for a long time.

When polymerizing the (meth)acrylic monomer, for example, a solution polymerization method can be applied. Examples of solvents used in this case include ethyl acetate, toluene, hexane, acetone, and methyl ethyl ketone. Moreover, as specific examples of methods other than solution polymerization, polymerization may be performed by bulk polymerization, suspension polymerization, emulsion polymerization, or the like.

The weight average molecular weight of component (A) is preferably 10,000 to 500,000 from the viewpoint of excellent viscosity after blending, workability, toughness and elastic modulus of the cured product. Weight average molecular weight can be measured by gel permeation chromatography (GPC).

The content of component (A) is preferably 30 to 65 parts by mass, and 35 to 60 parts by mass based on 100 parts by mass of the total amount of component (A), component (B), component (C), and component (D). parts, and even more preferably 40 to 55 parts by mass. When the content of component (A) is 30 parts by mass or more, curability becomes good, and when it is 65 parts by mass or less, curing shrinkage can be suppressed.

[Component (B): Crosslinking agent]
The photocurable resin composition according to this embodiment contains a crosslinking agent. The photocurable resin composition according to the present embodiment contains a (meth)acrylic polymer having a structural unit derived from a monomer having a hydroxy group in order to increase cohesive force and impart heat resistance, etc. , it is preferable to contain a crosslinking agent that reacts with hydroxyl groups.

Examples of the crosslinking agent include polyfunctional (meth)acrylate compounds, isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and melamine compounds. Among these crosslinking agents, polyfunctional (meth)acrylate compounds and isocyanate compounds are preferred because they can easily crosslink (meth)acrylic polymers.

Examples of polyfunctional (meth)acrylate compounds include trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexaacrylate. Examples include polyfunctional (meth)acrylates having three or more (meth)acryloyl groups in the molecule, such as (meth)acrylate.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like.

Epoxy compounds include N,N,N',N'-tetraglycidyl-m-xylene diamine (trade name TETRAD-X, manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 1,3-bis(N,N-diglycidylaminomethyl). ) Cyclohexane (trade name: TETRAD-C, manufactured by Mitsubishi Gas Chemical Co., Ltd.). Examples of the oxazoline compound include the trade name Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd.). Examples of the aziridine compound include trade names HDU, TAZM, and TAZO (all manufactured by Sogo Yakuko Co., Ltd.). Examples of metal chelate compounds include aluminum, iron, tin, titanium, nickel, etc. as metal components, and acetylene, methyl acetoacetate, ethyl lactate, etc. as chelate components. Examples of melamine compounds include hexamethylol melamine.

The content of component (B) is preferably selected appropriately depending on the desired adhesive properties. The content of component (B) is preferably 1.0 to 5.0 parts by mass based on 100 parts by mass of the total amount of components (A), (B), (C) and (D). When the content of component (B) is 1.0 parts by mass or more, a crosslinked structure is easily formed by the crosslinking agent, and the cohesive force of the adhesive composition can be improved; In some cases, appropriate fluidity can be maintained and coatability can be improved.

[(C) Component: Monomer]
The photocurable resin composition according to the present embodiment contains a monomer (excluding a compound corresponding to component (B) or component (D)). The photocurable resin composition according to the present embodiment has a high elastic modulus when only the (meth)acrylic polymer and the crosslinking agent are used, and from the viewpoint of suppressing a decrease in coatability, the photocurable resin composition uses a diluent monomer and has a low viscosity. It is preferable to Examples of diluent monomers include 2-ethylhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, acroylmorpholine, and the like. The type of monomer is preferably selected appropriately depending on desired adhesive properties such as compatibility with the (meth)acrylic polymer, glass transition temperature (Tg), and cohesiveness.

The content of component (C) is preferably selected appropriately depending on the desired adhesive properties. The content of component (C) is preferably 30 to 58 parts by mass, and preferably 35 to 55 parts by mass, based on 100 parts by mass of the total amount of component (A), component (B), component (C), and component (D). parts, more preferably 40 to 50 parts by mass. When the content of component (C) is 30 to 58 parts by mass, the modulus of elasticity is within a suitable range, and coating properties can be improved. The content of component (C) may be 40 to 58 parts by mass based on 100 parts by mass of the total amount of component (A), component (B), component (C), and component (D).

[Component (D): Photoinitiator]
As a photoinitiator, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 4-t-butyl-trichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one , 1-(4-isopropylphenyl-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxy Acetophenone-based photoinitiators such as ethoxy)-phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1, etc. benzoin photoinitiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal; benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, Benzophenone photoinitiators such as 4-benzoyl-4'-methyldiphenyl sulfide and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethyl Examples include thioxanthone-based photoinitiators such as thioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone.

The content of component (D) varies depending on the extinction coefficient, etc., but is from 0.005 to 100 parts by mass of the total amount of component (A), component (B), component (C), and component (D). It is preferably 5.0 parts by weight, more preferably 0.1 to 3.0 parts by weight, and even more preferably 0.1 to 0.5 parts by weight. When the content of component (D) is 0.005 parts by mass or more, the curing reaction of the photocurable resin composition can be sufficiently promoted, and a cured product can be efficiently formed. When the content of component (D) is 5.0 parts by mass or less, it is possible to suppress the reaction rate from decreasing in the thickness direction of the photocurable resin composition.

[Component (E): Antioxidant]
As a method of suppressing deterioration phenomena such as coloring, methods of adding various antioxidants to synthetic resins are known. The antioxidant used in this embodiment is not particularly limited, and conventionally known compounds can be appropriately employed. Examples include primary antioxidants such as hindered phenolic antioxidants and amine antioxidants, and secondary antioxidants such as phosphorus antioxidants, thiol antioxidants, and thioether antioxidants. .

The content of the antioxidant is preferably 0.05 to 2.0 parts by mass, and 0.05 to 2.0 parts by mass, based on 100 parts by mass of the total amount of components (A), (B), (C), and (D). 0.1 to 1.5 parts by weight is more preferable, and 0.2 to 1.0 parts by weight is even more preferable. When the antioxidant content is 0.05 parts by mass or more, yellowing of the resin composition can be easily suppressed, and when it is 2.0 parts by mass or less, deterioration in curability can be suppressed.

In the photocurable resin composition according to this embodiment, it is preferable to use a hindered phenol antioxidant, a thiol antioxidant, etc., and 4,6-bis(octylthiomethyl)-o-cresol (BASF It is more preferable to use 4,6-bis(octylthiomethyl)-o-cresol. preferable.

<Cured product>
The cured product according to the present embodiment is a cured product of the photocurable resin composition according to the present embodiment. It can be obtained by photocuring a photocurable resin composition by irradiating it with active energy rays such as rays and γ rays. The cured product of the photocurable resin composition is, for example, an optical adhesive cured product. The cured product according to this embodiment is, for example, in the form of a sheet.

The photocurable resin composition and its cured product according to this embodiment are extremely effective for adhesion to glass, polarizing plates, plastic films, composite sheets thereof, and the like.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. Note that "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

<Preparation of adhesive sheet>
(Example 1)
[Polymerization process of acrylic polymer for adhesive]
Methyl ethyl ketone (MEK) as a solvent was added to a pressurized stainless steel reactor equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube, and the mixture was stirred. Next, the temperature inside the system was raised to 82°C while blowing nitrogen into the charged solvent, and then 75 parts of 2-ethylhexyl acrylate (AOEC) and 25 parts of 2-hydroxyethyl acrylate (AHEC), which are acrylic monomers, were polymerized. A mixture of 0.15 parts of dimethyl 2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-601) as an initiator was uniformly mixed over 2 hours. It was added in a dropwise amount. After all the monomers were added dropwise and the mixture was kept warm for 1 hour, a mixture of 0.2 parts of polymerization initiator V-601 dissolved in MEK was added dropwise in an even amount over 30 minutes. Thereafter, the mixture was kept warm for about 1 hour, and then diluted with MEK. Next, as a step of deactivating the polymerization initiator, the temperature was raised to 128° C. under a pressure of 0.3 MPa, and the temperature was kept for 2.5 hours to obtain an acrylic polymerization intermediate with a solid content of 50%.

[Desolution process of acrylic polymer for adhesive]
The acrylic polymer of this example was obtained by replacing the solvent in the acrylic polymerization intermediate polymerized above with a monomer, so the following steps were performed.

In a separable flask equipped with a stirrer, a thermometer, an air blowing tube, and a vacuum pump, the deactivated acrylic polymerization intermediate (120 parts) and AOEC (35 parts) (solid content: AOEC = 65: 35) and 0.065 part of 3,5-di-tert-butyl-4-hydroxytoluene (BHT), and stirring and temperature raising were started while bubbling air. When the temperature was raised to 50° C., pressure reduction was started using a vacuum pump. The pressure inside the flask was reduced while paying attention to foaming, and the temperature was raised until the liquid temperature reached 90° C. while distilling off the solvent. The pressure was continued to be reduced while keeping the temperature at 90° C., and after 2 hours, it was confirmed by gas chromatography that the residual amount of solvent in the system was 0.02% or less, and an acrylic polymer was obtained.

[Preparation of adhesive]
With respect to 51 parts of the solid content of the acrylic polymer, (B) 2.8 parts of crosslinking agent (HGNR-003), (C) 29.8 parts of 2-ethylhexyl acrylate (AOEC), 4 -2.9 parts of hydroxybutyl acrylate (4-HBA) and 13.0 parts of acroylmorpholine (ACMO), and (D) 1-hydroxycyclohexyl phenyl ketone (Irgacure 184 (I-184)), which is a photopolymerization initiator. A pressure-sensitive adhesive containing 0.5 part of 4,6-bis(octylthiomethyl)-o-cresol (IRG Irganox-1520L), which is a hindered phenolic antioxidant (E) (Photocurable resin composition, adhesive main agent).

[Method for producing adhesive sheet]
The adhesive adjusted to a predetermined composition was sandwiched between two types of release separators: a heavy release separator: HTA-75 (film thickness: 75 μm) and a light release separator: BD-50 (film thickness: 50 μm), and a 300 μm spacer was used. An adhesive sheet was prepared by applying with a roller and curing with ultraviolet light. The conditions for ultraviolet curing are as follows.
Ultraviolet irradiation device: UV SYSTEM CS60 manufactured by GS YUASA LIGHTING Co., Ltd.
Ultraviolet lamp: Manufactured by GS YUASA LIGHTING Co., Ltd., metal halide lamp Exposure conditions: Illuminance 200 mW/cm ² , cumulative light amount 3000 mJ/cm ² (500 mJ cm ² × 4 times)

(Example 2)
An adhesive was obtained in the same manner as in Example 1, except that in [Polymerization step of acrylic polymer for adhesive], the acrylic monomers used were changed to 60 parts of AOEC and 40 parts of AHEC. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Example 3)
An adhesive was obtained in the same manner as in Example 1, except that in [Polymerization step of acrylic polymer for adhesive], the acrylic monomers used were changed to 90 parts of AOEC and 10 parts of AHEC. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Example 4)
[Preparation of adhesive] An adhesive was obtained in the same manner as in Example 1, except that the amount of antioxidant used was changed to 1.0 part of IRG1520L. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Example 5)
[Preparation of adhesive] An adhesive was prepared in the same manner as in Example 1, except that the antioxidant used was changed to 1.0 part of distearyl thiodipropionate (IRG PS800FD), which is a thiol-based antioxidant. I got it. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Example 6)
An adhesive was obtained in the same manner as in Example 3 except that the monomer used in [Preparation of adhesive] was changed to 45.7 parts of AOEC. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Comparative example 1)
Except for changing the polymerization initiator used in the [polymerization process of acrylic polymer for adhesives] to AIBN (2,2'-azobis(2-methylpropionitrile)) and eliminating the addition of an antioxidant. An adhesive was obtained in the same manner as in Example 1. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Comparative example 2)
An adhesive was obtained in the same manner as in Example 1 except that the polymerization initiator used in [Polymerization step of acrylic polymer for adhesive] was changed to AIBN. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Comparative example 3)
An adhesive was obtained in the same manner as in Example 2, except that the polymerization initiator used in [Polymerization step of acrylic polymer for adhesive] was changed to AIBN, and the addition of an antioxidant was omitted. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Comparative example 4)
An adhesive was obtained in the same manner as in Example 3, except that the polymerization initiator used in [Polymerization step of acrylic polymer for adhesive] was changed to AIBN, and the addition of an antioxidant was omitted. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Comparative example 5)
An adhesive was obtained in the same manner as in Example 5, except that the polymerization initiator used in [Polymerization step of acrylic polymer for adhesive] was changed to AIBN. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

(Comparative example 6)
A pressure-sensitive adhesive was obtained in the same manner as in Example 6, except that the polymerization initiator used in [Polymerization step of acrylic polymer for pressure-sensitive adhesive] was changed to AIBN, and the addition of an antioxidant was omitted. Then, using this adhesive, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

<Evaluation>
The colorability (yellowness) and adhesion to glass of the pressure-sensitive adhesive sheets of each Example and each Comparative Example were measured by the following methods. The results are shown in Tables 1 and 2.

[Evaluation method of colorability (yellowness, heat-resistant coloring)]
After cutting out the produced adhesive sheet into a size of 50 mm x 50 mm, the peel separator on one side was peeled off and bonded to glass to prepare a test piece. The peel separator of this test piece was peeled off and the initial YI value (initial sheet YI value) was measured using a color difference meter (Spectrophotometer SD6000 manufactured by Nippon Denshoku Industries Co., Ltd.). Thereafter, the sheet was placed in a dryer at 95° C. for 1000 hours, and then the YI value (sheet YI value after heat resistance test) was measured in the same manner. Then, the change in YI value at 95°C x 1000 hours ("95°C x 1000 hours YI value" - "Initial YI value") was determined from the initial YI value. Note that the higher the YI value, the stronger the yellowish tinge, and the larger the change, the more advanced the deterioration of the cured product.

[Method for measuring adhesion to glass (shear stress, shear adhesive strength)]
After cutting out the prepared adhesive sheet into a size of 20 mm x 20 mm, the release separators on both sides were peeled off, and the sheet was sandwiched between two pieces of glass to obtain a test piece. The test piece was attached to a tensile tester (Autograph AG-X/R, manufactured by Shimadzu Corporation), and measurements were taken at a peeling rate of 30 mm/min and a measurement temperature of 85°C, and the strength when the test piece broke was determined by shearing. Adhesive strength.

As is clear from Example 1 in Table 1, thermal coloring was suppressed by using the non-nitrile polymerization initiator V-601 and adding the hindered phenol antioxidant IRG1520L. Furthermore, from Examples 2 and 3, similar effects were confirmed when the copolymerization ratio of the acrylic polymer was set to AOEC:AHEC=60:40 to 90:10. It is assumed that by changing the copolymerization ratio, the larger the hydroxyl value, the stronger the interaction with glass, and the greater the adhesive force. In Example 4, in which the amount of the antioxidant IRG1520L was increased, coloring could be suppressed to the same degree as in Example 1, but the adhesive strength was slightly lowered. In Example 5, in which the thiol-based antioxidant IRG PS800FD was used as the antioxidant, thermal coloring was suppressed, although the effect was lower than that of IRG1520L in Example 1. In Example 6, in which only AOEC was used as the diluent monomer, thermal coloring was similarly suppressed.

On the other hand, in Comparative Example 1, which used AIBN having a nitrile structure as a polymerization initiator and did not contain an antioxidant, the coloring was large after 1000 hours at 95°C. In Comparative Examples 2 and 5 in which an antioxidant was added, thermal coloring was suppressed more than in Comparative Example 1, but thermal coloring was more suppressed than in cases where both a non-nitrile polymerization initiator and an antioxidant were formulated. It was big. Further, from Comparative Examples 3 and 4, even if the copolymerization ratio of the acrylic polymer was AOEC:AHEC=60:40 to 90:10, thermal coloring was large when AIBN was used and no antioxidant was used. Even in Comparative Example 6 where only AOEC was used as the diluent monomer, thermal coloring was large when AIBN was used and no antioxidant was used.

Based on these results, it is thought that when using a polymerization initiator with a nitrile structure, radicals and colored substances (ketene imine, etc.) generated from the remaining polymerization initiator promote the deterioration of the resin due to heat, causing coloration. Therefore, it is presumed that the coloring was suppressed by using a polymerization initiator that does not contain a nitrile structure and by scavenging radicals with an antioxidant.

Claims (1)

Contains (meth)acrylic polymer, monomer, photoinitiator and antioxidant,
The (meth)acrylic polymer is a polymer obtained by polymerizing a (meth)acrylic monomer using a non-nitrile azo ester polymerization initiator, and a structural unit derived from a (meth)acrylic acid alkyl ester monomer. , and has a structural unit derived from a hydroxy group-containing monomer,
A photocurable resin composition in which the ratio of the (meth)acrylic acid alkyl ester monomer is 50 to 95% by mass based on the total amount of the (meth)acrylic acid alkyl ester monomer and the hydroxy group-containing monomer (provided that , contains a vinyl monomer having a hydroxyl group in the range of 10 to 70% by mass of the total structural units, has a glass transition temperature (Tg) of 40 to 150°C, and has a number average molecular weight of 500 to 10,000. a tackifier comprising a vinyl polymer,
An optical resin composition comprising (A) an acrylic acid derivative, (B) an acrylic acid derivative polymer, and (C) a high molecular weight crosslinking agent, wherein the (A) acrylic acid derivative is an alkyl 2 or more selected from the group consisting of methacrylate, alkyl acrylate, methacrylic ester having a hydroxyl group, and acrylic ester having a hydroxyl group, and the (B) acrylic acid derivative polymer has an alkyl methacrylate, an alkyl acrylate, and a hydroxyl group. Two or more selected from the group consisting of a methacrylic ester having a hydroxyl group and an acrylic ester having a hydroxyl group are used as monomers, and the high molecular weight crosslinking agent (C) has a weight average molecular weight of 4,000 to 20, 000 polyurethane acrylate;
An adhesive composition comprising a monomer component containing a compound represented by any one of the following chemical formulas 1 to 3, or a polymer component having the monomer component as a polymerized unit, and a dye.
An adhesive composition comprising an acrylic polymer and a photoreactive monomer, wherein the acrylic polymer has a methyl methacrylate content of 3 to 30% based on the total amount (100% by weight) of monomer components constituting the acrylic polymer. An adhesive composition characterized in that it is an acrylic polymer composed of monomer components of % by weight,
Adhesive containing an acrylic resin (A), an ethylenically unsaturated compound (B) containing one ethylenically unsaturated group, and an ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups The agent composition [I] is an adhesive cured by active energy rays and/or heat, and the ethylenically unsaturated compound (B) containing one ethylenically unsaturated group is an aromatic ring-containing monomer ( B1) and a branched alkyl chain-containing (meth)acrylate monomer (B2) in which the alkyl group has 14 or more carbon atoms;
Contains an acrylic resin (A), an ethylenically unsaturated compound (B) containing one ethylenically unsaturated group, and an ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups, As the ethylenically unsaturated compound (B) containing one ethylenically unsaturated group, an aromatic ring-containing monomer (B1) and a branched alkyl chain-containing (meth)acrylate monomer (B2) in which the alkyl group has 14 or more carbon atoms are used. (excluding adhesive compositions for active energy rays and/or thermosetting optical members characterized by containing the following) .
In the chemical formulas 1 to 3, R is hydrogen or an alkyl group, A, B, T, U and W are each independently an alkylene group or an alkylidene group, and Q is an alkyl group or an aryl group. Yes, and n is a number from 0 to 5.