Adhesive, adhesive sheet, optical structure, and display

Abstract

The present invention provides an adhesive for optical use, the adhesive containing an oxygen absorbing agent. The adhesive can inhibit generation of needle-shaped cracks and has excellent weather resistance. The oxygen absorbent is preferably a compound represented by general formula (II). In general formula (II), R9 represents a hydrogen atom or a methyl group, and R10 represents any one of a hydroxyl group, a (meth) acryloyloxy group, a styryloxy group, and a C2-5 alkenyloxy group. And each of R11, R12, R13 and R14 independently represents any one of an alkyl group having 1-6 carbon atoms, an alkenyl group having 2-6 carbon atoms, an aryl group and an aralkyl group.

Description

Technical Field

[0001] The present invention relates to adhesives and adhesive sheets, and optical structures and displays obtained using the adhesives and adhesive sheets. Background Technology

[0002] In recent years, various mobile electronic devices such as mobile phones, smartphones, and tablets have incorporated display modules with liquid crystal elements, light-emitting diodes (LEDs), and organic electroluminescent (OLED) elements.

[0003] In the displays described above, a protective panel is typically provided on the surface side of the display module. As electronic devices become thinner and lighter, these protective panels have gradually changed from glass panels to plastic panels such as acrylic panels and polycarbonate panels.

[0004] Here, a gap is provided between the protective panel and the display module so that even if the protective panel is deformed by external force, the deformed protective panel will not collide with the display module.

[0005] However, if the gaps, i.e. air layers, as described above exist, there will be problems such as large light reflection loss and reduced image quality caused by the refractive index difference between the protective panel and the air layer, and the refractive index difference between the air layer and the display module.

[0006] Therefore, a solution has been proposed to fill the gap between the protective panel and the display module with an adhesive layer (adhesive layer), thereby improving the image quality of the display. For example, as an adhesive layer for filling the gap between the protective panel and the display module, Patent Document 1 discloses an adhesive layer with a shear storage modulus (G') of 1.0 × 10⁻⁶ at 25°C and 1 Hz. 5 Adhesive layers with a Pa value below 40% and a gel content of 40% or more.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2010-97070 Summary of the Invention

[0010] (a) Technical problems to be solved

[0011] However, if a display obtained using the adhesive layer described above is exposed to high-intensity ultraviolet light for an extended period, needle-like cracks may sometimes appear in the adhesive layer. In particular, this problem is more likely to occur when conducting weather resistance acceleration tests involving prolonged exposure to high-intensity ultraviolet light.

[0012] The present invention was made in view of such actual conditions, and its object is to provide adhesives, adhesive sheets, optical components and display bodies that can suppress the generation of needle cracks and have excellent weather resistance.

[0013] (II) Technical Solution

[0014] To achieve the above objectives, firstly, the present invention provides an adhesive for optical applications, which contains an oxygen absorber (Invention 1).

[0015] The oxygen absorber contained in the adhesive of the above-described invention (Invention 1) can capture oxygen from the adhesive, the adherend, and during bonding. Therefore, even under prolonged exposure to high-intensity ultraviolet light (e.g., 20 hours, 40 hours, 80 hours, etc.), the adhesive can suppress structural changes (e.g., destruction of cross-linking points) that could initiate needle-like cracks. As a result, the formation of needle-like cracks can be suppressed, and excellent weather resistance can be achieved.

[0016] In the above invention (Invention 1), the oxygen absorbent is preferably a compound represented by the following general formula (I) (Invention 2).

[0017] [Chemical Formula 1]

[0018]

[0019] In general formula (I), X and Y each independently represent chalcogen atoms, and R 1 R 2 R 7 and R 8 Each independently represents any one of alkyl, alkenyl, aryl, and aralkyl groups having 1 to 6 carbon atoms, R 3 R 4 R 5 and R 6 Each of the following independently represents any one of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, and an aralkyl group. J represents a linking group composed of an aliphatic hydrocarbon having 3 to 15 carbon atoms, wherein any carbon atom of the linking group may be optionally substituted with an oxygen atom, or the linking group may optionally have at least one substituent selected from the group consisting of a hydroxyl group, (meth)acryloyloxy group, styryloxy group, and an alkenyloxy group having 2 to 5 carbon atoms. n is any integer from 1 to 5. Wherein, when multiple Y and R are present... 5 R 6 R 7 and R 8 At that time, Y, R 5 R 6 R 7 and R8 These can be chosen from different atoms or groups.

[0020] In the above inventions (Inventions 1 and 2), the oxygen absorbent is preferably a compound represented by the following general formula (II) (Invention 3).

[0021] [Chemical Formula 2]

[0022]

[0023] In general formula (II), R 9 R represents a hydrogen atom or a methyl group. 10 R represents any one of hydroxyl, (meth)acryloyloxy, styryloxy, and olefinic groups having 2 to 5 carbon atoms. 11 R 12 R 13 and R 14 Each can independently represent any one of alkyl, alkenyl, aryl, and aralkyl groups having 1 to 6 carbon atoms.

[0024] In the above inventions (Inventions 1 to 3), the oxygen absorbent is preferably a compound represented by the following formula (III) (Invention 4).

[0025] [Chemical Formula 3]

[0026]

[0027] In the above inventions (Inventions 1 to 4), the adhesive is preferably an acrylic adhesive (Invention 5).

[0028] In the above inventions (Inventions 1-5), the adhesive is preferably a (meth)acrylate polymer or its crosslinked product (Invention 6).

[0029] In the above inventions (Inventions 1 to 6), the adhesive is preferably an adhesive that can be cured by active energy rays (Invention 7).

[0030] Second, the present invention provides an adhesive sheet having an adhesive layer for bonding two components together, characterized in that at least one of the components is an optical component, and the adhesive layer is composed of the adhesive (Invention 1-7) (Invention 8).

[0031] In the above invention (Invention 8), the chromaticity b* of the adhesive layer after bonding, as specified by the CIE1976 L*a*b* color system, is set to b*1, and the adhesive layer after bonding is irradiated for 120 hours at an illuminance of 100mW / cm². 2When the chromaticity b* of the adhesive layer after ultraviolet light exposure is set to b*2 according to the CIE1976L*a*b* color system, the absolute value of the ratio of b*2 to b*1 is preferably 10 or less (Invention 9).

[0032] In the above inventions (Inventions 8 and 9), it is preferable that the adhesive sheet has two release tabs, and the adhesive layer is held by the release tabs in such a way that it contacts the release surfaces of the two release tabs (Invention 10).

[0033] Third, the present invention provides an optical component, which is an optical component formed by bonding at least two components together using an adhesive layer, characterized in that at least one of the components is an optical component, and the adhesive layer is formed by the adhesive (Invention 1-7) (Invention 11).

[0034] Fourth, the present invention provides a display body comprising a display body component, another display body component, and an adhesive layer for bonding the one display body component and the other display body component together, characterized in that the adhesive layer is formed from the adhesive layer of the adhesive sheet (Invention 8-10) (Invention 12).

[0035] In the above invention (Invention 12), both the one display body component and the other display body component can be rigid plates (Invention 13).

[0036] (III) Beneficial Effects

[0037] The adhesive, adhesive sheet, optical component, and display body of the present invention can suppress the generation of needle-like cracks and have excellent weather resistance. Attached Figure Description

[0038] Figure 1 This is a cross-sectional view of an adhesive sheet according to one embodiment of the present invention.

[0039] Figure 2 This is a cross-sectional view of a display body according to one embodiment of the present invention. Detailed Implementation

[0040] The following describes the embodiments of the present invention.

[0041] [Adhesive]

[0042] One embodiment of the adhesive of the present invention is used for optical applications and preferably contains an oxygen absorber. It is generally believed that prolonged exposure to high illuminance (e.g., 100 mW / cm²) can reduce the effectiveness of such applications. 2Ultraviolet light can cause changes in the cross-linking structure of adhesives, resulting in needle-like cracks. In contrast, the adhesive of this embodiment contains an oxygen absorber. By capturing oxygen from the adhesive, the adherend, and during bonding, changes in the cross-linking structure of the adhesive can be suppressed even after prolonged exposure to high-intensity ultraviolet light (e.g., 20 hours, 40 hours, 80 hours, etc.). This suppresses changes in the structure that could become the initiation point of needle-like cracks (e.g., the destruction of cross-linking points). Thus, the adhesive of this embodiment can suppress the formation of needle-like cracks and exhibits excellent weather resistance.

[0043] The oxygen absorbent in this embodiment is preferably a compound represented by the following general formula (I) (hereinafter sometimes referred to as "compound Q").

[0044] [Chemical Formula 1]

[0045]

[0046] In general formula (I), X and Y each independently represent a chalcogenide atom, and R 1 R 2 R 7 and R 8 Each independently represents any one of alkyl, alkenyl, aryl, and aralkyl groups having 1 to 6 carbon atoms, R 3 R 4 R 5 and R 6 Each of the following independently represents any one of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, and an aralkyl group. J represents a linking group composed of an aliphatic hydrocarbon having 3 to 15 carbon atoms, wherein any carbon atom of the linking group may be optionally replaced by an oxygen atom, or the linking group may optionally have at least one substituent selected from the group consisting of a hydroxyl group, (meth)acryloyloxy group, styryloxy group, and an alkenyloxy group having 2 to 5 carbon atoms. n is any integer from 1 to 5. Wherein, when multiple Y and R are present... 5 R 6 R 7 and R 8 At that time, Y, R 5 R 6 R 7 and R 8 These can be chosen from different atoms or groups.

[0047] In general formula (I), from the perspective of the ease of obtaining raw materials, n is preferably 1 to 4, and more preferably 1 or 2.

[0048] In general formula (I), from the perspective of ease of manufacture of compound Q and improvement of oxygen absorption performance, X and Y are preferably oxygen atoms or sulfur atoms, and more preferably oxygen atoms.

[0049] R in general formula (I) 1 R 2 R 7 and R 8 Alkyl groups having 1 to 6 carbon atoms include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc.

[0050] R in general formula (I) 1 R 2 R 7 and R 8 Alkenes with 2 to 6 carbon atoms include, for example, vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, pentenyl, heptenyl, hexenyl, iso-3-hexenyl, cyclohexenyl, etc.

[0051] R in general formula (I) 1 R 2 R 7 and R 8 Aryl groups, for example, include phenyl, tolyl, xylyl, naphthyl, etc.

[0052] R in general formula (I) 1 R 2 R 7 and R 8 Aryl groups, for example, include benzyl, 2-phenylethyl, 2-naphthylethyl, diphenylmethyl, etc.

[0053] Of the above, R is preferred. 1 R 2 R 7 and R 8 Each is independently any one of an alkyl group having 1 to 6 carbon atoms and an alkenyl group having 2 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group.

[0054] R in general formula (I) 3 R 4 R 5 and R 6 Alkyl groups having 1 to 6 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, aryl groups, and aralkyl groups can be exemplified by the above-mentioned R. 1 R 2 R 7 and R 8Alkyl groups, alkenyl groups with 2 to 6 carbon atoms, aryl groups, and aralkyl groups are the same as those in the group.

[0055] Of the above, R is preferred. 3 R 4 R 5 and R 6 Each of the following is independently selected from hydrogen atom, alkyl group having 1 to 3 carbon atoms, alkenyl group having 2 or 3 carbon atoms, and aryl group, more preferably hydrogen atom or methyl group, and even more preferably hydrogen atom. From the perspective of improving the oxygen absorption performance of compound Q, R is preferred. 3 and R 6 All are hydrogen atoms, preferably R 4 and R 5 Each is independently a hydrogen atom or a methyl group, or more preferably, a hydrogen atom.

[0056] In general formula (I), from the perspective of ease of operation of compound Q, the linking group J is preferably an aliphatic hydrocarbon group with 3 to 10 carbon atoms, and more preferably an aliphatic hydrocarbon group with 3 to 5 carbon atoms. The linking group J may optionally contain a styreneoxy group as a substituent, such as 4-styreneoxy. Furthermore, the olefinoxy group with 2 to 5 carbon atoms that may optionally contain a substituent in the linking group J may be a vinyloxy group with 2 to 5 carbon atoms. From the perspective of improving the oxygen absorption performance of compound Q, the optional substituent in the linking group J is preferably a hydroxyl or (meth)acryloyloxy group.

[0057] As a specific example of the linking group J, from the perspective of improving the oxygen absorption performance of compound Q, the linking group represented by the following general formula (J-1) is more preferred. Furthermore, the "*" in general formula (J-1) indicates a bonding point with X or Y.

[0058] [Chemical Formula 2]

[0059]

[0060] In the above general formula (J-1), R 9 Represents a hydrogen atom or a methyl group, preferably a hydrogen atom. R 10 The term refers to any one of hydroxyl, (meth)acryloyloxy, styryloxy, and an olefinic group having 2 to 5 carbon atoms, preferably hydroxyl or (meth)acryloyloxy. Alternatively, the olefinic group having 2 to 5 carbon atoms may be an ethyleneoxy group having 2 to 5 carbon atoms.

[0061] From the perspective of oxygen absorption performance, as a specific example of compound Q, the compound represented by the following general formula (II) is preferred.

[0062] [Chemical Formula 3]

[0063]

[0064] In general formula (II), R 9 R represents a hydrogen atom or a methyl group. 10 R represents any one of hydroxyl, (meth)acryloyloxy, styryloxy, and olefinic groups having 2 to 5 carbon atoms. 11 R 12 R 13 and R 14 Each can independently represent any one of alkyl, alkenyl, aryl, and aralkyl groups having 1 to 6 carbon atoms.

[0065] R in general formula (II) 10 Preferably, it is hydroxyl or (meth)acryloyloxy. R 10 The olefinic group with 2 to 5 carbon atoms can be an ethyleneoxy group with 2 to 5 carbon atoms.

[0066] R in general formula (II) 11 R 12 R 13 and R 14 The preferred forms are respectively related to R in the above general formula (I). 1 R 2 R 7 and R 8 same.

[0067] The oxygen absorbent in this embodiment is particularly preferably a compound represented by the following formula (III) (hereinafter sometimes referred to as "compound S").

[0068] [Chemical Formula 3]

[0069]

[0070] There are no particular limitations on the preparation method of compound Q. Compound Q can be prepared by using known methods or a combination of known methods. As an example, compound S can be prepared by reacting a compound capable of forming a linking group J, such as epichlorohydrin, with 3-methyl-2-buten-1-ol in the presence of a base such as potassium hydroxide. As for the reaction conditions, from the perspective of ensuring a complete reaction, stirring at a temperature of about 25 to 70°C for about 2 to 10 hours is preferred.

[0071] The oxygen absorbent content in the adhesive of this embodiment is preferably 0.01 to 20% by mass, more preferably 0.05 to 12% by mass, particularly preferably 0.1 to 8% by mass, even more preferably 0.4 to 4% by mass, and most preferably 0.8 to 2% by mass. This allows for more effective suppression of needle-like crack formation and the attainment of superior weather resistance.

[0072] The adhesive used in this embodiment is preferably a pressure-sensitive adhesive, but it is not limited to this. The type of adhesive used in this embodiment can be any of the following: acrylic adhesive, polyester adhesive, polyurethane adhesive, rubber adhesive, silicone adhesive, etc. Furthermore, the adhesive can be any of the following: emulsion type, solvent type, or solvent-free type, and can be any of the following: crosslinked type or non-crosslinked type. Among these, acrylic adhesives with excellent pressure-sensitive adhesive properties and optical properties are preferred.

[0073] As an acrylic adhesive, it can be an adhesive that cures with active energy rays or an adhesive that cures without active energy rays; it can be a crosslinking adhesive or a non-crosslinking adhesive, or an adhesive that combines the above-mentioned adhesives. Among these, acrylic adhesives that cure with active energy rays are preferred from the perspective of easily obtaining excellent weather resistance.

[0074] From the perspective of film-forming properties, the adhesive of this embodiment preferably contains a (meth)acrylate polymer as the main adhesive agent, and particularly preferably contains a crosslinked product of a (meth)acrylate polymer. Furthermore, the adhesive of this embodiment also preferably contains the aforementioned main adhesive agent and an active energy radiation curable component. The crosslinked product of the (meth)acrylate polymer is preferably a crosslinked product of a (meth)acrylate polymer and a crosslinking agent.

[0075] Specifically, the adhesive of this embodiment is preferably formed by crosslinking (preferably thermal crosslinking) an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylate polymer (A), a crosslinking agent (B), an oxygen absorber (C), and an active energy radiation curable component (D) as needed. Furthermore, in this specification, (meth)acrylate refers to both acrylic acid and methacrylic acid. Other similar terms are also used. In addition, "polymer" also includes the concept of "copolymer".

[0076] (1) Each ingredient

[0077] (1-1) (Meth)acrylate polymer (A)

[0078] The (meth)acrylate polymer (A) preferably contains structural units derived from alkyl (meth)acrylates. This results in good pressure-sensitive adhesion. Furthermore, the alkyl (meth)acrylate does not contain the hard monomers described later.

[0079] From the perspective of pressure-sensitive adhesion, alkyl methacrylates with 1 to 20 carbon atoms in the alkyl group are preferred as (meth)acrylates. Examples of alkyl methacrylates with 1 to 20 carbon atoms in the alkyl group include methyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, myristyl methacrylate, palmitate methacrylate, and stearate methacrylate. The above-mentioned alkyl methacrylates can be used alone or in combination of two or more. Of the above, from the perspective of further improving pressure-sensitive adhesion, (meth)acrylates with alkyl groups having 1 to 14 carbon atoms are preferred, (meth)acrylates with alkyl groups having 2 to 10 carbon atoms are more preferred, and (meth)acrylates with alkyl groups having 3 to 8 carbon atoms are particularly preferred. Specifically, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate are preferred, n-butyl acrylate or 2-ethylhexyl acrylate are particularly preferred, and 2-ethylhexyl acrylate is even more preferred.

[0080] From the perspective of imparting pressure-sensitive adhesion, the (meth)acrylate polymer (A) preferably contains 30-99% by mass, more preferably 40-92% by mass, particularly preferably 50-86% by mass, and even more preferably 55-80% by mass of structural units derived from (meth)acrylate, wherein, preferably, it contains 60-75% by mass of structural units derived from (meth)acrylate.

[0081] The (meth)acrylate polymer (A) preferably has structural units derived from monomers containing reactive functional groups. Thus, the reactive functional groups from the monomers react with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), resulting in an adhesive with the desired cohesive strength.

[0082] As monomers containing reactive groups, preferred examples include monomers with intramolecular hydroxyl groups (hydroxyl-containing monomers), monomers with intramolecular carboxyl groups (carboxyl-containing monomers), and monomers with intramolecular amino groups (amino-containing monomers). Among these, monomers containing hydroxyl groups or carboxyl groups that exhibit excellent reactivity with the crosslinking agent (B) are preferred.

[0083] Examples of hydroxyl-containing monomers include hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate. Among these, 2-hydroxyethyl methacrylate or 4-hydroxybutyl methacrylate is preferred from the perspective of reactivity with the crosslinking agent (B) and copolymerization with other monomers. The aforementioned hydroxyl-containing monomers can be used alone or in combination of two or more.

[0084] Examples of carboxyl-containing monomers include olefinic unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid or methacrylic acid is preferred, and acrylic acid is particularly preferred, considering its reactivity with the crosslinking agent (B) and its copolymerization properties with other monomers. The aforementioned carboxyl-containing monomers can be used alone or in combination of two or more.

[0085] From the perspective of cohesion, the content of structural units from monomers containing reactive functional groups in the (meth)acrylate polymer (A) is preferably 1 to 40% by mass, more preferably 3 to 34% by mass, particularly preferably 6 to 28% by mass, further preferably 9 to 24% by mass, and preferably 12 to 20% by mass.

[0086] The (meth)acrylate polymer (A) preferably contains structural units derived from hard monomers with a glass transition temperature (Tg) of 70°C or higher as homopolymers. Furthermore, the aforementioned monomers containing reactive functional groups are not included in the hard monomers. By including structural units derived from the aforementioned hard monomers in the (meth)acrylate polymer (A), the cohesive strength of the resulting adhesive is improved, and excellent anti-foaming properties are readily obtained. In particular, when structural units of (meth)acrylates with 5 to 8 carbon atoms derived from alkyl groups are included, there is a tendency for a decrease in cohesive strength; therefore, it is preferable to include structural units derived from the aforementioned hard monomers. The glass transition temperature (Tg) of the aforementioned hard monomers as homopolymers is preferably 75 to 200°C, particularly preferably 80 to 180°C, and even more preferably 90 to 150°C.

[0087] Examples of the aforementioned hard monomers include methyl methacrylate (Tg 105℃), isobornyl acrylate (Tg 94℃), isobornyl methacrylate (Tg 180℃), adamantyl acrylate (Tg 115℃), and adamantyl methacrylate (Tg 141℃). These hard monomers can be used alone or in combination of two or more.

[0088] Among the aforementioned hard monomers, from the perspective of preventing adverse effects on pressure-sensitive adhesion, transparency, and other properties, while further enhancing the performance of the hard monomers, methyl methacrylate or isobornyl acrylate is preferred, and isobornyl acrylate, as a monomer with an intramolecular alicyclic structure (containing alicyclic monomers), is particularly preferred.

[0089] When the (meth)acrylate polymer (A) contains structural units from the above-mentioned hard monomers, from the perspective of cohesion and anti-foaming properties, its content is preferably 1 to 30% by mass, more preferably 4 to 25% by mass, particularly preferably 8 to 20% by mass, and even more preferably 10 to 16% by mass.

[0090] The (meth)acrylate polymer (A) preferably contains structural units derived from monomers having nitrogen atoms within the molecule (nitrogen-containing monomers). In particular, when using alicyclic monomers, especially isobornyl acrylate, as the aforementioned hard monomer, it is preferable to contain structural units derived from nitrogen-containing monomers. By including structural units from nitrogen-containing monomers, the adhesive can be given a specified polarity, resulting in superior adhesion.

[0091] From the perspective of giving the (meth)acrylate polymer (A) a suitable degree of rigidity, a monomer having a nitrogen-containing heterocycle is preferred as the aforementioned nitrogen-containing monomer. Furthermore, from the perspective of increasing the degree of freedom of the portion of the nitrogen-containing monomer in the higher-order structure of the formed adhesive, the nitrogen-containing monomer preferably does not contain reactive unsaturated double bond groups, except for the one polymerizable group used in the polymerization of the (meth)acrylate polymer (A).

[0092] Examples of monomers having nitrogen-containing heterocycles include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, ethyl aziridine(meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimazole, N-vinylcarbazole, and N-vinylphthalimide. Among these, N-(meth)acryloylmorpholine is preferred for its superior adhesive properties, and N-acryloylmorpholine is particularly preferred. One of the above-mentioned monomers having nitrogen-containing heterocycles may be used alone, or two or more may be used in combination.

[0093] When the (meth)acrylate polymer (A) contains structural units from nitrogen-containing monomers, its content is preferably 1 to 20% by mass, more preferably 2 to 16% by mass, particularly preferably 3 to 12% by mass, and even more preferably 4 to 8% by mass, from the perspective of better adhesion.

[0094] The (meth)acrylate polymer (A) may contain structural units from other monomers as needed. As other monomers, monomers that do not contain reactive functional groups are preferred so as not to interfere with the function of monomers containing reactive groups. Examples of such other monomers include methoxyethyl methacrylate, ethoxyethyl methacrylate, alkoxyalkyl methacrylates, vinyl acetate, styrene, etc. These other monomers may be used alone or in combination of two or more.

[0095] The (meth)acrylate polymer (A) can be obtained through solution polymerization, solvent-free polymerization, or emulsion polymerization. Solution polymers obtained via solution polymerization are preferred. By using solution polymers, high molecular weight polymers are readily obtained, leading to superior weather resistance.

[0096] The polymerization form of (meth)acrylate polymer (A) can be a random copolymer or a block copolymer.

[0097] The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 100,000 to 3,000,000, more preferably 200,000 to 2,400,000, particularly preferably 300,000 to 1,800,000, further preferably 400,000 to 1,200,000, and most preferably 450,000 to 800,000. This readily yields superior weather resistance. Furthermore, the weight-average molecular weight in this specification is a value converted from standard polystyrene determined by gel permeation chromatography (GPC).

[0098] In addition, in the adhesive composition P, the (meth)acrylate polymer (A) can be used alone or in combination of two or more.

[0099] The content of (meth)acrylate polymer (A) in the adhesive composition P of this embodiment is preferably 70-99.9% by mass, more preferably 80-99% by mass, particularly preferably 85-98% by mass, and even more preferably 90-97% by mass. As a result, the adhesive exhibits excellent film-forming properties and pressure-sensitive adhesion, and readily achieves superior weather resistance.

[0100] (1-2) Crosslinking agent (B)

[0101] Crosslinking agent (B) crosslinks (meth)acrylate polymer (A) by heating adhesive composition P, thereby enabling the formation of a well-defined three-dimensional network crosslinked structure. This results in an adhesive with specified cohesive strength, easily achieving superior weather resistance.

[0102] As the aforementioned crosslinking agent (B), any crosslinking agent that reacts with the reactive functional groups (hydroxyl or carboxyl groups) of the (meth)acrylate polymer (A) is acceptable. Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Here, when the (meth)acrylate polymer (A) contains structural units derived from hydroxyl-containing monomers, an isocyanate-based crosslinking agent with excellent reactivity with hydroxyl groups is preferably used as the crosslinking agent (B). Furthermore, one type of crosslinking agent (B) can be used alone, or two or more types can be used in combination.

[0103] The isocyanate-based crosslinking agent is an isocyanate-based crosslinking agent containing at least a polyisocyanate compound. Examples of polyisocyanate compounds include: aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret, isocyanurate, and adducts of the above substances as reactants with low-molecular-weight compounds containing active hydrogen, such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. From the perspective of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates are preferred, and trimethylolpropane-modified toluene diisocyanate or trimethylolpropane-modified xylylene diisocyanate are particularly preferred.

[0104] The content of crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 10 parts by weight relative to 100 parts by weight of (meth)acrylate polymer (A), more preferably 0.04 to 5 parts by weight, particularly preferably 0.08 to 1 part by weight, further preferably 0.12 to 0.6 parts by weight, and most preferably 0.15 to 0.3 parts by weight. This readily yields superior weather resistance.

[0105] (1-3) Oxygen absorbent (C)

[0106] The oxygen absorber (C) used in the adhesive composition P is the oxygen absorber described above, and its specific composition and content (mass %) in the adhesive are as described above. The amount of oxygen absorber (C) in the adhesive composition P relative to 100 parts by mass of the (meth)acrylate polymer (A) is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 15 parts by mass, particularly preferably 0.1 to 10 parts by mass, further preferably 0.4 to 5 parts by mass, and most preferably 0.8 to 2 parts by mass. This allows for more effective suppression of needle-like crack formation and the attainment of superior weather resistance.

[0107] (1-4) Active energy ray curing component (D)

[0108] By incorporating an active energy ray curable component (D) into the adhesive composition P, the resulting adhesive becomes an active energy ray curable adhesive. Based on the adhesive layer cured by active energy rays, superior weather resistance can be easily obtained through further active energy ray curing after bonding.

[0109] The active energy ray curable component (D) is not particularly limited as long as it does not hinder adhesion and is cured by irradiation with active energy rays. It can be any of monomers, oligomers, or polymers, or a mixture thereof. Among them, multifunctional acrylate monomers that are easy to obtain with superior weather resistance are preferred.

[0110] Examples of multifunctional acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, and hydroxypivalic acid neopentyl glycol di(meth)acrylate. di(meth)acrylate), dicyclopentyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified di(meth)acrylate phosphate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2-acryloxyethoxy)phenyl]fluorene, etc. (difunctional); trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, Trifunctional types include propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tri(acryloyloxyethyl)isocyanurate, and ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate; quadrufunctional types include diglycerol tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional types include propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional types include dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. Of the above, from the perspective of the weather resistance of the obtained adhesive, polyfunctional acrylate monomers containing an intramolecular isocyanurate structure, such as di(acryloyloxyethyl)isocyanurate, tri(acryloyloxyethyl)isocyanurate, and ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate, are preferred. Polyfunctional acrylate monomers with three or more functions and containing an intramolecular isocyanurate structure are more preferred, and ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate is particularly preferred. The above-mentioned polyfunctional acrylate monomers can be used alone or in combination of two or more. Furthermore, from the perspective of the obtained adhesive easily exhibiting the desired viscoelasticity, the polyfunctional acrylate monomers preferably have a molecular weight of less than 20,000, more preferably less than 10,000, and particularly preferably less than 5,000. Further, from the perspective of compatibility with (meth)acrylate polymer (A), a molecular weight of less than 1,000 is preferred.

[0111] When the adhesive composition P contains an active energy ray curable component (D), the content of the active energy ray curable component (D) relative to 100 parts by weight of the (meth)acrylate polymer (A) is preferably 0.1 to 40 parts by weight, more preferably 1 to 30 parts by weight, particularly preferably 2 to 20 parts by weight, further preferably 3 to 15 parts by weight, and most preferably 4 to 10 parts by weight. This readily yields superior weather resistance.

[0112] (1-5) Photopolymerization initiator (E)

[0113] When the adhesive composition P contains an active energy ray curable component (D) and uses ultraviolet light as the active energy ray, the adhesive composition P preferably contains a photopolymerization initiator (E). By containing a photopolymerization initiator (E), the active energy ray curable component (D) can be effectively cured, and the polymerization curing time and the amount of ultraviolet light irradiation can be reduced.

[0114] Examples of photopolymerization initiators (E) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone. -propan-1-one), 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)one, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzoindimethyl ketal (benzil) Dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligomeric [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc. These photopolymerization initiators can be used alone or in combination of two or more.

[0115] Among the above, from the perspective of suppressing the generation of needle-like cracks, phosphine-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, or mixtures of 1-hydroxycyclohexylphenyl ketone and benzophenone are preferred, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide is particularly preferred.

[0116] The content of photopolymerization initiator (E) in the adhesive composition P is preferably 1 to 30 parts by mass relative to 100 parts by mass of the active energy ray curable component (D), particularly preferably 5 to 25 parts by mass, and even more preferably 10 to 20 parts by mass. Therefore, the resulting adhesive readily meets the physical properties described later.

[0117] (1-6) Silane coupling agent (F)

[0118] The adhesive composition P preferably further contains a silane coupling agent (F). This improves the adhesion between the adhesive and a glass component if the adherend has a glass component. Furthermore, even if the adherend is a plastic sheet, the adhesion between the adhesive and the plastic sheet is improved. Consequently, superior weather resistance is easily obtained.

[0119] As a silane coupling agent (F), an organosilicon compound that is compatible with (meth)acrylate polymers (A), has light transmittance, and has at least one alkoxysilyl group in the molecule is preferred.

[0120] Examples of silane coupling agents (F) include: silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloyloxypropyltrimethoxysilane; silicon compounds with epoxy structures such as 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyltriethoxysilane. Thiol-containing silicon compounds such as methylpropyldimethoxymethylsilane; amino-containing silicides such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; condensates of 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one thereof with alkyl-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. The above silane coupling agents can be used alone or in combination of two or more.

[0121] The content of silane coupling agent (F) in the adhesive composition P is preferably 0.01 to 10 parts by weight relative to 100 parts by weight of (meth)acrylate polymer (A), more preferably 0.04 to 5 parts by weight, particularly preferably 0.08 to 1 part by weight, further preferably 0.12 to 0.7 parts by weight, and most preferably 0.15 to 0.4 parts by weight. As a result, the adhesive exhibits excellent adhesion, weather resistance, and anti-foaming properties.

[0122] (1-7) Ultraviolet absorber (G)

[0123] The adhesive composition P preferably further contains an ultraviolet absorber (G). As a result, the resulting adhesive can more effectively suppress the formation of needle-like cracks and exhibits superior weather resistance.

[0124] Examples of UV absorbers (G) include compounds based on benzophenone, benzotriazole, benzoate, benzoxazinone, triazine, phenyl salicylate, cyanoacrylate, and nickel complex salts. Among these, benzophenone-based or triazine-based compounds are preferred from the perspectives of suppressing needle-like cracks and compatibility with (meth)acrylate polymers (A). One of these UV absorbers can be used alone, or two or more can be used in combination.

[0125] Examples of compounds in the benzophenone family include 2,2-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid hydrate, and 2-hydroxy-4-n-octyloxybenzophenone.

[0126] Examples of the aforementioned triazine compounds include 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-octyloxyphenol, and 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol.

[0127] When the adhesive composition P contains a UV absorber (G), the content of the UV absorber (G) relative to 100 parts by weight of the (meth)acrylate polymer (A) is preferably 0.01 to 10 parts by weight, more preferably 0.04 to 5 parts by weight, particularly preferably 0.08 to 1 part by weight, further preferably 0.1 to 0.7 parts by weight, and most preferably 0.2 to 0.5 parts by weight. This readily satisfies the physical properties described later, resulting in superior weather resistance and anti-foaming properties.

[0128] (1-8) Light stabilizer (H)

[0129] The adhesive composition P preferably further contains a light stabilizer (H). As a result, the resulting adhesive can more effectively suppress the formation of needle-like cracks and exhibits superior weather resistance.

[0130] Examples of light stabilizers (H) include hindered amine and hindered phenolic light stabilizers, among which hindered amine light stabilizers (HALS) with superior performance are preferred. Examples of hindered amine light stabilizers include N-CH3 type HALS, NH type HALS, NO-alkyl type HALS, reactive HALS with (meth)acryloyl groups, and high molecular weight HALS. NO-alkyl type HALS with superior performance are preferred. Examples of NO-alkyl type HALS include bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate. One of the above light stabilizers can be used alone, or two or more can be used in combination.

[0131] When the adhesive composition P contains a light stabilizer (H), the content of the light stabilizer (H) relative to 100 parts by weight of the (meth)acrylate polymer (A) is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 7 parts by weight, particularly preferably 0.1 to 5 parts by weight, further preferably 0.4 to 3 parts by weight, and most preferably 0.8 to 2 parts by weight. This readily satisfies the physical properties described later, resulting in superior weather resistance.

[0132] (1-9) Antioxidants (I)

[0133] The adhesive composition P preferably further contains an antioxidant (I). As a result, the resulting adhesive can more effectively suppress the formation of needle-like cracks and exhibits superior weather resistance.

[0134] As antioxidants (I), examples include: triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythritol-tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butyl-4-hydroxyphenyl)propionate. Hindered phenolic compounds such as butylphenyl propionate and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; tris(2,4-di-t-butylphenyl) phosphite, 2,2-methylene bis(4,6-di-t-butylphenyl)octyl phosphite, and bis(2,6-di-t-butylphenyl)pentaerythritol diphosphite. Phosphite compounds such as diphosphite and tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylenediphosphonite; sulfur-based antioxidants such as 2-mercaptobenzimidazole, pentaerythritol tetrakis(3-lauryl thiopropionate), bis(dibutyldithiocarbamate)nickel(II), nickel diethyldithiocarbamate, and dilaurate 3,3'-thiodipropionate. Among these, hindered phenolic compounds that enhance the above effects are preferred, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is particularly preferred. The above antioxidants can be used alone or in combination of two or more.

[0135] When the adhesive composition P contains an antioxidant (I), the content of the antioxidant (I) relative to 100 parts by weight of the (meth)acrylate polymer (A) is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 7 parts by weight, particularly preferably 0.1 to 5 parts by weight, further preferably 0.4 to 3 parts by weight, and most preferably 0.8 to 2 parts by weight. This readily satisfies the physical properties described later, resulting in superior weather resistance.

[0136] (1-10) Various additives

[0137] Depending on the requirements, the adhesive composition P may also contain various additives commonly used in acrylic adhesives, such as antistatic agents, tackifiers, colorants, infrared absorbers, rust inhibitors, softeners, fillers, plasticizers, refractive index modifiers, etc.

[0138] (2) Preparation of adhesive composition

[0139] The adhesive composition P can be prepared by the following method: preparing a (meth)acrylate polymer (A), mixing the obtained (meth)acrylate polymer (A), crosslinking agent (B) and oxygen absorber (C), and adding, as needed, an active energy radiation curing component (D), a photopolymerization initiator (E), a silane coupling agent (F), an ultraviolet absorber (G), a light stabilizer (H), an antioxidant (I), additives, etc.

[0140] (Meth)acrylate polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer using conventional free radical polymerization. The polymerization of (meth)acrylate polymer (A) is preferably carried out by solution polymerization using a polymerization initiator, if necessary. However, the invention is not limited thereto, and polymerization can also be performed under solvent-free conditions.

[0141] Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone; two or more may be used simultaneously. Examples of polymerization initiators include azo compounds and organic peroxides; two or more may be used simultaneously. Furthermore, in the above polymerization process, the weight-average molecular weight of the obtained polymer can be adjusted by incorporating chain transfer agents such as 2-mercaptoethanol.

[0142] After obtaining (meth)acrylate polymer (A), a crosslinking agent (B), an oxygen absorber (C), and, as needed, active energy radiation curable components (D), photopolymerization initiators (E), silane coupling agents (F), ultraviolet absorbers (G), light stabilizers (H), antioxidants (I), additives, and diluents are added to the solution of (meth)acrylate polymer (A). The mixture is thoroughly mixed to obtain an adhesive composition P (coating solution) diluted with a solvent. Furthermore, if any of the above components precipitates when used in solid form or when mixed with other components in an undiluted state, that component can be pre-dissolved or diluted in a diluent before being mixed with other components.

[0143] As diluents for the above, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane can be used; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

[0144] The concentration and viscosity of the coating solution prepared in this way are not particularly limited as long as they are within a coatable range, and can be appropriately selected according to the situation. For example, the concentration of the adhesive composition P can be diluted to 10-60% by mass. Furthermore, the addition of a diluent is not necessary when obtaining the coating solution; as long as the adhesive composition P has a coatable viscosity, a diluent is not required. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent of (meth)acrylate polymer (A) is directly used as the diluent.

[0145] (3) Manufacturing of adhesives

[0146] After applying the above adhesive composition P to the desired object, crosslinking is performed to obtain an adhesive (adhesive layer).

[0147] Crosslinking of the adhesive composition P can be achieved by heat treatment. The drying process following coating of the adhesive composition P can also serve as the heat treatment. The heating temperature for the heat treatment is preferably 50–150°C, particularly preferably 70–120°C. Furthermore, the heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

[0148] After heat treatment, a curing period of approximately 1 to 2 weeks can be set at room temperature (e.g., 23°C, 50% RH) as needed. If this curing period is required, an adhesive will form after the curing period; if no curing period is required, the adhesive will form after the heat treatment is completed. Additionally, in this specification, "relative humidity α%" is sometimes expressed as "α% RH" (RH; Relative Humidity).

[0149] Through the above heat treatment (and curing), a cross-linked product of (meth)acrylate polymer (A) cross-linked by cross-linking agent (B) is formed.

[0150] (4) Physical properties (gel fraction)

[0151] The gel fraction of the adhesive in this embodiment is preferably 20-85%, more preferably 30-70%, particularly preferably 40-60%, further preferably 45-55%, and most preferably 47-50%. This allows for easy attainment of good pressure-sensitive adhesion when applying the adhesive to the substrate. Furthermore, the method for determining the gel fraction in this specification is shown in the test examples described later.

[0152] When the adhesive in this embodiment is an active energy ray curable adhesive, the gel fraction of the adhesive after active energy ray curing is preferably 30-99%, more preferably 40-90%, particularly preferably 45-80%, further preferably 50-74%, and most preferably 55-68%, and most preferably 60-63%. Therefore, the adhesion of the adhered objects is easily and well-maintained.

[0153] [Adhesive sheet]

[0154] The adhesive sheet of this embodiment has an adhesive layer for bonding two components together. At least one of the components is an optical component. The specific structure of the adhesive sheet and the optical component will be described later.

[0155] The adhesive layer in the adhesive sheet of this embodiment is composed of the adhesive of the above embodiment.

[0156] From the perspective of adhesion and weather resistance, the thickness of the adhesive layer of the adhesive sheet in this embodiment (the value measured based on JISK7130) is preferably 1 to 1000 μm, more preferably 10 to 800 μm, particularly preferably 30 to 600 μm, and from the perspective of weather resistance, preferably 50 to 400 μm, further preferably 80 to 300 μm, wherein preferably 120 to 260 μm.

[0157] (1)Physical properties

[0158] (1-1) Gel fraction / rate of change of gel fraction

[0159] The adhesive layer of the adhesive sheet in this embodiment, after bonding two components, is irradiated for 120 hours at an illuminance of 100 mW / cm². 2 After exposure to ultraviolet light (hereinafter sometimes referred to as "S-UV irradiation"), the gel content of the adhesive constituting the adhesive layer is preferably 40-99%, more preferably 50-95%, particularly preferably 55-90%, and even more preferably 60-85%, wherein 65-80% is preferred. Thus, the adhesive maintains its prescribed cohesive strength even after S-UV irradiation, easily achieving excellent weather resistance.

[0160] Here, when the adhesive layer is non-reactive energy ray curable, "adhesive layer after bonding" in this specification refers to an adhesive layer in the same state as the adhesive layer of the adhesive sheet. When the adhesive layer is reactive energy ray curable, "adhesive layer after bonding" in this specification refers to an adhesive layer cured by reactive energy ray irradiation after bonding. "Adhesive layer cured by reactive energy ray" means that the adhesive layer has been completely cured by reactive energy ray irradiation. Specifically, it means that when the reactive energy ray cured adhesive layer is further irradiated with reactive energy ray at the same dose (light intensity) as during reactive energy ray curing, the increase rate of the gel fraction of the adhesive layer is 10% or less, and particularly, the increase rate is 5% or less.

[0161] When the gel fraction of the adhesive in the bonded adhesive layer constituting the adhesive sheet of this embodiment is set as G1, and the gel fraction of the adhesive constituting the bonded adhesive layer after S-UV irradiation is set as G2, the gel fraction change rate ((G2 / G1)×100) (%), which is the ratio of G2 to G1, is preferably 120% or less, more preferably 117% or less, particularly preferably 115% or less, further preferably 112% or less, and most preferably 109% or less. This suppresses the destruction of crosslinking points that become the initiation point of needle-like cracks, resulting in good adhesion to the adhered objects. In other words, it more effectively suppresses the generation of needle-like cracks and provides superior weather resistance.

[0162] The lower limit of the above-mentioned gel fraction change rate is not particularly limited, but it is preferably 100% or more, particularly preferably 103% or more, and even more preferably 105% or more.

[0163] (1-2) Average peak molecular weight of sol components

[0164] The average peak molecular weight of the sol component of the adhesive constituting the bonded adhesive layer of this embodiment is preferably 10,000 to 250,000, more preferably 30,000 to 200,000, particularly preferably 40,000 to 150,000, further preferably 50,000 to 100,000, and most preferably 60,000 to 80,000. This ensures good adhesion after bonding the components. Furthermore, the average peak molecular weight of the sol component in this specification is a value converted from standard polystyrene determined by gel permeation chromatography (GPC). Specific determination methods are shown in the experimental examples described later.

[0165] The average peak molecular weight of the sol component of the adhesive after S-UV irradiation of the bonded adhesive layer (hereinafter referred to as "S-UV irradiated adhesive") is preferably 10,000 to 200,000, more preferably 20,000 to 150,000, particularly preferably 30,000 to 100,000, further preferably 40,000 to 70,000, and most preferably 50,000 to 58,000. This allows for more effective suppression of needle-like cracks and superior weather resistance.

[0166] (1-3) Energy storage modulus G'

[0167] The storage modulus G' of the adhesive layer constituting the bonded component in this embodiment at 23°C is preferably 0.001–2 MPa, more preferably 0.005–1 MPa, more preferably 0.01–0.5 MPa, particularly preferably 0.02–0.1 MPa, and even more preferably 0.03–0.07 MPa. This ensures good adhesion after bonding the components. Furthermore, the method for measuring the storage modulus G' in this specification is shown in the experimental examples described later.

[0168] The storage modulus G' of the adhesive after S-UV irradiation at 23°C is preferably 0.0001–2 MPa, more preferably 0.005–1 MPa, more preferably 0.01–0.5 MPa, particularly preferably 0.03–0.2 MPa, even more preferably 0.05–0.15 MPa, and most preferably 0.07–0.1 MPa. This allows for more effective suppression of needle-like crack formation and superior weather resistance.

[0169] The storage modulus G' of the adhesive forming the bonded adhesive layer at -15°C is preferably 0.01–100 MPa, more preferably 0.1–50 MPa, more preferably 1–25 MPa, particularly preferably 2–10 MPa, and even more preferably 3.0–5.0 MPa. Therefore, the bonding strength of the bonded components at low temperatures is readily good.

[0170] The storage modulus G' of the adhesive after S-UV irradiation at -15°C is preferably 0.01–100 MPa, more preferably 0.1–50 MPa, more preferably 1–25 MPa, particularly preferably 3–10.0 MPa, and even more preferably 6–9.5 MPa. This allows for more effective suppression of needle-like crack formation and superior weather resistance.

[0171] The storage modulus G' of the adhesive forming the bonded adhesive layer at 100°C is preferably 0.0001–2 MPa, more preferably 0.0005–1 MPa, more preferably 0.001–0.1 MPa, particularly preferably 0.003–0.05 MPa, even more preferably 0.005–0.02 MPa, and most preferably 0.007–0.012 MPa. Therefore, the bonding strength of the bonded components at high temperatures is readily achieved.

[0172] The storage modulus G' of the adhesive after S-UV irradiation at 100°C is preferably 0.0001–2 MPa, more preferably 0.0005–1 MPa, more preferably 0.001–0.1 MPa, particularly preferably 0.002–0.05 MPa, further preferably 0.003–0.02 MPa, and most preferably 0.004–0.01 MPa. This allows for more effective suppression of needle-like crack formation and superior weather resistance.

[0173] (1-4) Peak temperature of loss tangent tanδ

[0174] The peak temperature Tb of the loss tangent tanδ of the adhesive constituting the bonded adhesive layer is preferably -40 to 20°C, more preferably -30 to 10°C, particularly preferably -25 to 0°C, and even more preferably -20 to -5°C, with -15 to -10°C being the most desirable. This ensures good adhesion after the components are bonded. Furthermore, the method for measuring the loss tangent tanδ is shown in the experimental examples described later.

[0175] The peak temperature Ta of the loss tangent tanδ of the adhesive after S-UV irradiation is preferably -40 to 20°C, more preferably -30 to 10°C, particularly preferably -24 to 5°C, and even more preferably -18 to 0°C, wherein it is preferably -12 to -7°C. This allows for more effective suppression of needle-like crack formation and superior weather resistance.

[0176] The value of Ta minus Tb (Ta-Tb) is preferably 0 to 30, more preferably 0.1 to 20, particularly preferably 0.4 to 10, and even more preferably 0.8 to 5, with 1 to 2 being the most common. As a result, after S-UV irradiation, the peak temperature of the loss tangent tanδ shifts towards the higher temperature side. Therefore, the area of ​​increased viscosity in the adhesive tends to shift from the lower temperature side to the room temperature side. This suppresses the destruction of crosslinking points that could become the initiation point of needle-like cracks, resulting in good adhesion to the adhered material. In other words, it more effectively suppresses the formation of needle-like cracks and provides superior weather resistance.

[0177] (1-5) Adhesion

[0178] In this embodiment, the adhesion strength of the adhesive layer after bonding to soda-lime glass is preferably 1–100 N / 25 mm, more preferably 10–90 N / 25 mm, particularly preferably 20–80 N / 25 mm, further preferably 30–70 N / 25 mm, and most preferably 40–60 N / 25 mm. This results in excellent weather resistance and anti-blistering properties. The aforementioned adhesion strength is essentially the adhesion strength measured by the 180-degree peel test based on JIS Z0237:2009, and the specific test method is shown in the test examples described later.

[0179] (1-6) Total transmittance

[0180] In this embodiment, the total light transmittance of the adhesive layer after bonding is preferably 80% or more, more preferably 90% or more, particularly preferably 95% or more, and even more preferably 99% or more. This results in very high transparency, making it suitable for optical applications (display bodies). The upper limit of the above-mentioned total light transmittance is not particularly limited; it can be 100%, or a value slightly exceeding 100% due to measurement conditions. Furthermore, the total light transmittance of the adhesive layer after S-UV irradiation is also preferably within the same numerical range as described above. The total light transmittance in this specification is a value measured based on JIS K7361-1:1997, and the specific test method is shown in the test examples described later.

[0181] (1-7) Haze value

[0182] In this embodiment, the haze value of the adhesive layer after lamination is preferably 2% or less, and particularly preferably 1% or less. This results in very high transparency, suitable for optical applications (display bodies). There is no particular limitation on the lower limit of this haze value; it can be 0%. Furthermore, the haze value of the adhesive layer after S-UV irradiation is also preferably within the same range as described above. The haze values ​​in this specification are measured based on JIS K7136:2000, and the specific test methods are shown in the test examples described later.

[0183] (1-8) Chromaticity b*

[0184] In this embodiment, the chromaticity b* (chromaticity b*1) of the bonded adhesive layer, as specified by the CIE 1976 L*a*b* color system, is preferably -20 to 20, more preferably -10 to 10, particularly preferably -5 to 5, further preferably -2 to 2, and most preferably -1 to 1, and most preferably -0.5 to 0.5. Thus, the adhesive layer is nearly colorless and transparent, suitable for optical applications.

[0185] The chromaticity b* (chromaticity b*2) of the adhesive layer after S-UV irradiation, as specified by the CIE 1976 L*a*b* color system, is preferably -20 to 20, more preferably -10 to 10, particularly preferably -5 to 5, and even more preferably -3 to 3, wherein -1.2 to 1.2 is preferred. Therefore, even after S-UV irradiation, the yellowing degree of the adhesive layer is relatively low, demonstrating excellent weather resistance from a chromaticity perspective.

[0186] The absolute value of the ratio of chromaticity b*2 to chromaticity b*1 (b*2 / b*1) is preferably 10 or less, more preferably 6 or less, particularly preferably 3 or less, and even more preferably 2.5 or less. Therefore, even after S-UV irradiation, the degree of yellowing of the adhesive layer is relatively small, and from a chromaticity perspective, it exhibits excellent weather resistance. Furthermore, the lower limit of the absolute value of the ratio (b*2 / b*1) is not particularly limited, but is most preferably 1.

[0187] (2) Specific composition of adhesive sheet

[0188] The specific structure of the adhesive sheet, as an example of this embodiment, is shown below. Figure 1 .

[0189] like Figure 1 As shown, in one embodiment, the adhesive sheet 1 comprises two release sheets 12a and 12b and an adhesive layer 11, wherein the adhesive layer 11 is held by the two release sheets 12a and 12b in such a manner that it contacts the release surfaces of the two release sheets 12a and 12b. Furthermore, in this specification, the release surface of a release sheet refers to the surface of the release sheet that exhibits release properties, including both surfaces that have undergone release treatment and surfaces that exhibit release properties even without release treatment.

[0190] The adhesive layer 11 is composed of the adhesive of the above embodiment.

[0191] Release tabs 12a and 12b protect the adhesive layer before the adhesive sheet is used and are peeled off when the adhesive sheet (adhesive layer) is used. In the adhesive sheet 1 of this embodiment, one or both of the release tabs 12a and 12b are not necessarily required.

[0192] Examples of release sheets 12a and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate film, ionomer resin film, ethylene-(meth)acrylate copolymer film, ethylene-(meth)acrylate polymer film, polystyrene film, polycarbonate film, polyimide film, and fluoropolymer film. Furthermore, cross-linked films of the above-mentioned films can also be used. Further, laminated films of the above-mentioned films can also be used. Additionally, from the perspective of SDGs, materials constituting the release sheets can be materials with high biomass content, materials that can be recycled or reused, or materials that have already been recycled or reused.

[0193] It is preferable to perform a peeling treatment on the peeling surfaces (particularly the surfaces in contact with the adhesive layer 11) of the release sheets 12a and 12b. Examples of release agents used for the peeling treatment include alkyd-based, silicone-based, fluorinated, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0194] There are no particular restrictions on the thickness of the release strips 12a and 12b, which are usually around 20 to 150 μm.

[0195] From an operational point of view, it is preferable to set one of the two peeling plates 12a and 12b as a heavy-duty peeling plate with high peeling force and the other as a light-duty peeling plate with low peeling force.

[0196] (3) Manufacturing of adhesive sheets

[0197] As an example of manufacturing adhesive sheet 1, a coating liquid of the adhesive composition P is applied to the release surface of a release sheet 12a (or 12b), and then heat-treated to thermally crosslink the adhesive composition P to form a coating layer. Then, the release surface of another release sheet 12b (or 12a) is overlapped onto this coating layer. If a curing period is required, the coating layer becomes adhesive layer 11 after the curing period; if no curing period is required, the coating layer directly becomes adhesive layer 11. Through the above processes, adhesive sheet 1 is obtained. The heat treatment and curing conditions are as described above.

[0198] Methods for applying the coating liquid as a coating adhesive composition P include, for example, rod coating, blade coating, roller coating, squeegee coating, die coating, gravure coating, etc.

[0199] (4) Applications

[0200] The adhesive sheet in this embodiment is used to bond two components together, at least one of which is an optical component.

[0201] As optical components, in addition to the components constituting the display body (display body components) described later, other examples include components constituting solar cells, moving bodies (vehicles, ships, airplanes, etc.), and building components (windows, exterior materials, interior materials, etc.). These are usually components made of light-transmitting plastic sheets, plastic films, glass sheets, glass films, etc., or components containing the above-mentioned components.

[0202] The other of the two components can be an optical component, or a component made of an opaque or translucent material. For example, it can also be a component made of metal, ceramic, colored plastic, colored glass, graphite, paper, wood, stone, mortar, plaster, etc., or a component containing the above components.

[0203] [Optical Components]

[0204] An optical component according to one embodiment of the present invention is formed by bonding at least two components together using an adhesive layer, at least one of which is an optical component. The adhesive layer is formed from the adhesive of the above embodiment, or from the adhesive layer of the adhesive sheet of the above embodiment.

[0205] The thickness of the adhesive layer in this embodiment is the same as the thickness of the adhesive layer in the adhesive sheet of the above embodiment. Furthermore, the optical components are as described in the above embodiment.

[0206] To manufacture the optical component of this embodiment, as an example, the adhesive coating liquid described above is applied to a component to form an adhesive layer, and then other components are bonded to the adhesive layer. As another example, the adhesive layer of the adhesive sheet described above is applied to a component, and then other components are bonded to the adhesive layer.

[0207] Here, when the adhesive layer is curable by active energy rays, it is preferable to irradiate the adhesive layer with active energy rays through any component (the component through which the active energy rays pass) after the above-mentioned bonding to cure the adhesive layer.

[0208] Reactive energy rays refer to rays containing energy quanta within electromagnetic waves or charged particle beams; specifically, examples include ultraviolet light and electron beams. Among reactive energy rays, ultraviolet light, which is particularly easy to manipulate, is preferred.

[0209] Ultraviolet (UV) irradiation can be achieved using high-pressure mercury lamps, Heraeus H lamps, xenon lamps, etc., with an optimal UV irradiation intensity of 50–1000 mW / cm². 2 Approximately. Furthermore, the preferred light intensity is 50–10000 mJ / cm². 2 More preferably 80–5000 mJ / cm 2 The preferred value is 300–2000 mJ / cm³. 2On the other hand, electron beam irradiation can be performed using an electron beam accelerator or the like, and the preferred irradiation dose is around 10 to 1000 krad.

[0210] [Display Body]

[0211] One embodiment of the present invention provides a display body comprising a display body component, another display body component, and an adhesive layer for bonding the one display body component and the other display body component together. This adhesive layer is formed from the adhesive layer of the adhesive sheet described in the above embodiment.

[0212] At least one of the aforementioned display body component and the other display body component may have a step at least on the side of the surface adhered to by the aforementioned adhesive layer.

[0213] Both of the aforementioned display components can be rigid sheets. When the two rigid sheets are bonded together, since these rigid sheets are hard and will not bend, by pressing the two rigid sheets vertically while the adhesive layer is attached to one rigid sheet, each rigid sheet is sealed to the adhesive layer, thereby bonding the two rigid sheets together.

[0214] The display body of one embodiment of the present invention will be described with reference to the accompanying drawings.

[0215] like Figure 2 As shown, the display body 2 of this embodiment is constructed by having a first display body component 21 (one display body component), a second display body component 22 (another display body component), and an adhesive layer 11 located between them and bonding the first display body component 21 and the second display body component 22 together.

[0216] At least one of the first display body component 21 and the second display body component 22 may have a step at least on the side of the surface adhered to by the adhesive layer 11. Figure 2 In the embodiment shown, the surface of the first display body component 21 on the adhesive layer 11 side has a step caused by the printing layer 3, etc.

[0217] The adhesive layer 11 in the display body 2 is the adhesive layer 11 (non-active energy ray curable) of the adhesive sheet 1 itself, or is formed by curing the adhesive layer 11 (active energy ray curable) of the adhesive sheet 1 by irradiation with active energy rays.

[0218] Display devices 2 can include, for example, liquid crystal displays (LCDs), light-emitting diode (LED) displays, organic electroluminescent (OLED) displays, electronic paper, and touch panels. Furthermore, LED displays also include those using miniature LEDs, micro LEDs, and the like.

[0219] The first display component 21, in addition to glass plates, plastic plates, etc., is preferably a protective panel composed of a laminate containing them. In this case, the printed layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the first display component 21.

[0220] The glass plate mentioned above is not particularly limited, and examples include chemically tempered glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass. The thickness of the glass plate is not particularly limited, but is typically 0.1–5 mm, preferably 0.2–2 mm.

[0221] The plastic sheet used is not particularly limited; examples include acrylic sheets and polycarbonate sheets. The thickness of the plastic sheet is not particularly limited, but is typically 0.2–5 mm, preferably 0.4–3 mm.

[0222] In addition, various functional layers (transparent conductive film, metal layer, silicon dioxide layer, hard coating, anti-glare layer, etc.) can be applied to one or both sides of the aforementioned glass plate, plastic plate, etc., and optical components can also be stacked. Furthermore, the transparent conductive film and metal layer can also be patterned.

[0223] The second display component 22 is preferably an optical component, a display module (e.g., a liquid crystal (LCD) module, a light-emitting diode (LED) module, an organic electroluminescent (OLED) module, an optical component that is part of the display module, or a laminate containing the display module that should be attached to the first display component 21.

[0224] Examples of such optical components include anti-scattering films, polarizers (polarizing films), polarizers, retardation plates (retardation films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transparent reflective films, and transparent conductive films. As a transparent conductive film, an ITO-PET film with a tin-doped indium oxide (ITO) layer formed on one side of a polyethylene terephthalate (PET) film is preferably cited as an example.

[0225] The material constituting the printed layer 3 is not particularly limited, and known printing materials can be used. The thickness of the printed layer 3, i.e., the height of the step, is preferably 0.5 to 50 μm, more preferably 1 to 30 μm, and particularly preferably 3 to 20 μm. By keeping the thickness of the printed layer 3 within the above range, the step following ability provided by the adhesive layer 11 can be effectively utilized, and the concealment of the purpose of the printed layer 3 can be sufficiently ensured. In addition, the printed layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the display component.

[0226] In order to manufacture the display body 2, as an example, a peeling piece 12a of the adhesive sheet 1 is peeled off, and the adhesive layer 11 exposed by the adhesive sheet 1 is attached to the side of the first display body constituent member 21 where the printed layer 3 is present.

[0227] Next, another release tab 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display body component 22 to obtain the display body. In addition, as another example, the bonding order of the first display body component 21 and the second display body component 22 can be changed.

[0228] Here, when the adhesive layer 11 is curable by active energy rays (containing active energy ray curable component (D)), it is preferable that after the laminate of the first display body component 21 and the adhesive layer 11 is bonded to the second display body component 22, the adhesive layer 11 is irradiated with active energy rays through the first display body component 21 and / or the second display body component 22 to cure the adhesive layer 11.

[0229] In the display body 2, since the adhesive constituting the adhesive layer 11 contains the aforementioned oxygen absorber, even when exposed to high-intensity ultraviolet light for a long period of time (e.g., 20 hours, 40 hours, 80 hours, or 120 hours depending on the situation), the generation of needle-like cracks in the adhesive layer 11 is suppressed, resulting in excellent weather resistance.

[0230] The embodiments described above are provided for the purpose of understanding the present invention and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments also include all design changes, equivalents, etc., that fall within the technical scope of the present invention.

[0231] For example, one or both of the release tabs 12a and 12b of the adhesive sheet 1 can be omitted. Alternatively, desired optical components can be laminated instead of release tabs 12a and / or 12b. Furthermore, the first display body component 21 may not have a step. Moreover, not only the first display body component 21, but also the second display body component 22 may have a step on the adhesive layer 11 side.

[0232] Furthermore, in this specification, when referred to as "X to Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less," as well as "preferably greater than X" or "preferably less than Y." Additionally, when referred to as "X or more" (where X is any number), unless otherwise specified, it includes the meaning of "preferably greater than X," and when referred to as "Y or less" (where Y is any number), unless otherwise specified, it also includes the meaning of "preferably less than Y."

[0233] Example

[0234] The present invention will be further described in detail below through examples, etc., but the scope of the present invention is not limited to these examples, etc.

[0235] [Example 1]

[0236] 1. Preparation of (meth)acrylate polymers

[0237] (Meth)acrylate polymer (A) was prepared by solution polymerization of 65 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of isobornyl acrylate, 5 parts by mass of N-acryloylmorpholine, and 15 parts by mass of 2-hydroxyethyl acrylate. The molecular weight of (meth)acrylate polymer (A) was determined by the method described below, and the weight-average molecular weight (Mw) was 500,000.

[0238] 2. Preparation of adhesive compositions

[0239] Mix 100 parts by mass (solid component conversion value; the same below) of the (meth)acrylate polymer (A) obtained in step 1 above, 0.17 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "TAKENATE D-101E"), 1 part by mass of the compound represented by the following formula (III) as an oxygen absorber (C) (manufactured by KURARAY CO.,LTD., product name "Diprenyl Glycerin Ether (DPNG)"), and 5.2 parts by mass of ε-caprolactone-modified tri-(2-acryloyloxyethyl) isocyanurate (manufactured by SHIN-NAKAMURA CHEMICAL CO,LTD., product name "NK ESTER") as an active energy ray curing component (D). A-9300-1CL”), 0.92 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (E1) as a photopolymerization initiator (E), and 0.25 parts by weight of 3-glycidyl etheroxypropyltrimethoxysilane as a silane coupling agent (F) were stirred thoroughly and diluted with methyl ethyl ketone to obtain a coating liquid of adhesive composition.

[0240] [Chemical Formula 4]

[0241]

[0242] Table 1 shows the proportions (converted to solids) of the adhesive composition when (meth)acrylate polymer (A) is set at 100 parts by weight. Details of the abbreviations, etc., listed in Table 1 are as follows.

[0243] [(Meth)acrylate polymer (A)]

[0244] 2EHA: 2-Ethylhexyl acrylate

[0245] IBXA: Isoborneol Acrylate

[0246] ACMO: N-Acryloylmorpholine

[0247] HEA: 2-Hydroxyethyl acrylate

[0248] [Photopolymerization initiator (E)]

[0249] E1: 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide

[0250] E2: A mixture of 1-hydroxycyclohexylphenyl ketone and benzophenone (mass ratio 50:50)

[0251] [UV absorber (G)]

[0252] G1: 2,2-Dihydroxy-4-methoxybenzophenone

[0253] G2: 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol

[0254] 3. Manufacturing of adhesive sheets

[0255] Using a coater, the coating solution of the adhesive composition obtained in step 2 above is applied to the release-treated surface of a heavy-release release sheet R1, on which one side of a polyethylene terephthalate film has been peeled using a silicone-based release agent. Then, it is heated at 90°C for 1 minute to form a coating layer. Next, the coating layer on the release sheet R1 is bonded to a light-release release sheet R2, on which one side of a polyethylene terephthalate film has been peeled using a silicone-based release agent, with the release-treated surface of the release sheet R2 in contact with the coating layer. The bond is then cured at 23°C and 50% RH for 7 days to produce an adhesive sheet with an adhesive layer of 50 μm thickness, i.e., an adhesive sheet consisting of release sheet R1 / adhesive layer (thickness: 50 μm) / release sheet R2.

[0256] The thickness of the adhesive layer was measured according to JIS K7130 using a constant pressure thickness gauge (manufactured by TECLOCK, product name "PG-02"). Furthermore, regarding the peel force of the release liner R1 and release liner R2 in the obtained adhesive sheet, it was confirmed that the peel force of release liner R1 is greater than that of release liner R2.

[0257] [Examples 2-5, Comparative Examples 1-2]

[0258] Except for changing the amount of oxygen absorber (C) and the type of photopolymerization initiator (E) as shown in Table 1, the adhesive sheet was manufactured in the same manner as in Example 1. Furthermore, in Examples 2 and 3, ultraviolet absorber (G) (G1 / G2) was added in the amounts shown in Table 1. In Example 4, bis(1-undecoxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate as a light stabilizer (H) was added in the amounts shown in Table 1. In Example 5, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate as an antioxidant (I) was added in the amounts shown in Table 1.

[0259] Here, the weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight converted from polystyrene determined using gel permeation chromatography (GPC) under the following conditions (GPC determination).

[0260] <Measurement Conditions>

[0261] • Measuring apparatus: Manufactured by TOSOH CORPORATION, HLC-8320

[0262] • GPC column (passes through in the following order): Manufactured by TOSOH CORPORATION

[0263] TSK gel super HH

[0264] TSK gel super HM-H

[0265] TSK gel super H2000

[0266] • Determination solvent: tetrahydrofuran

[0267] • Measurement temperature: 40℃

[0268] [Experimental Example 1] (Determination of Gel Fraction)

[0269] By stacking the adhesive layers of the adhesive sheets manufactured in the multilayer embodiments and comparative examples, an adhesive layer with a thickness of 250 μm was prepared. This adhesive layer (thickness: 250 μm) was cut to a size of 70 mm × 150 mm, wrapped in a polyester mesh (mesh size 200), and its mass was measured using a precision balance. The mass of the mesh alone was then subtracted to calculate the mass of the adhesive. This mass is designated as M1.

[0270] Next, the adhesive wrapped with the above-mentioned polyester mesh was impregnated with ethyl acetate for 24 hours at room temperature (23°C). The adhesive was then removed and air-dried at 23°C and 50% RH for 24 hours, followed by drying in an oven at 80°C for 12 hours. After drying, its mass was weighed using a precision balance, and the mass of the mesh alone was subtracted to calculate the mass of the adhesive alone. This mass is designated as M2. The gel fraction (%) (G0) is expressed as (M2 / M1) × 100. The results are shown in Table 2.

[0271] Furthermore, an adhesive layer with a thickness of 250 μm was prepared by laminating the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples. This adhesive layer (thickness: 250 μm) was irradiated with active energy rays (ultraviolet; UV) to cure it. The gel fraction (%) (G1) of the adhesive layer cured by active energy rays was measured in the same manner as described above. The results are shown in Table 2. The irradiation conditions of the active energy rays are as follows.

[0272] <Conditions for Irradiation by Active Energy Rays>

[0273] • Use a high-pressure mercury lamp

[0274] Illuminance: 200mW / cm² 2 Light intensity: 1000 mJ / cm 2

[0275] • The UV illuminance meter used is the "UVPF-A1" manufactured by Eye Graphics.

[0276] Furthermore, an adhesive layer with a thickness of 250 μm was prepared by laminating the adhesive layer of the adhesive sheet manufactured in the multilayer embodiment and comparative example. Using this adhesive layer (thickness: 250 μm), two soda-lime glass plates (manufactured by Nippon SheetGlass Co., Ltd., thickness: 1.1 mm, length 70 mm × width 150 mm) were bonded together to prepare a laminate (soda-lime glass plate / adhesive layer (250 μm) / soda-lime glass plate). The laminate was irradiated with active energy rays (ultraviolet; UV) under the above-described active energy irradiation conditions to cure the adhesive layer. The resulting laminate was then irradiated with ultraviolet light (S-UV irradiation) under the following conditions. Then, for the laminate after S-UV irradiation, the adhesive layer was separated from the two soda-lime glass plates. The gel fraction (%) (G2) of the adhesive layer after separation was measured in the same manner as above. The results are shown in Table 2.

[0277] <Ultraviolet Irradiation Conditions>

[0278] • Equipment: EYE SUPER UV TESTER SUV-W151 (manufactured by IWASAKI ELECTRIC CO.,LTD.)

[0279] • UV lamp: ME06-L31WX / SUV (manufactured by IWASAKI ELECTRIC CO.,LTD.)

[0280] • Water cooling jacket: WJ50-SUV-4 (manufactured by IWASAKI ELECTRIC CO.,LTD.)

[0281] Illuminance: 100mW / cm² 2

[0282] • Irradiation time: 120 hours

[0283] • Light intensity: 43.2 kJ / cm² 2

[0284] Temperature: 63℃

[0285] Humidity: 70% RH

[0286] • Temperature and humidity control: Closed-loop system

[0287] Based on the G1 and G2 obtained above, the change rate of gel fraction ((G2 / G1)×100) (%), which is the ratio of G2 to G1, was calculated. The results are shown in Table 2.

[0288] [Experimental Example 2] (Determination of the average peak molecular weight of sol components)

[0289] By stacking the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples, an adhesive layer with a thickness of 250 μm was prepared. This adhesive layer (250 μm) was irradiated with active energy rays (ultraviolet; UV) under the same active energy irradiation conditions as in Test Example 1, causing the adhesive layer to cure. The ethyl acetate obtained in the same manner as in Test Example 1 (after adhesive impregnation and removal) was concentrated using an evaporator to obtain the sol component. Next, the sol component was diluted to a 0.3% by mass solution using tetrahydrofuran, filtered through a 0.45 μm filter, and the average peak molecular weight (Mp; before S-UV) of the sol component was determined by GPC measurement. The measurement conditions for the GPC measurement were as described above. The results are shown in Table 2.

[0290] Furthermore, an adhesive layer with a thickness of 250 μm was prepared by laminating the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples. Using this adhesive layer (thickness: 250 μm), a laminate was prepared in the same manner as in Test Example 1. The laminate was irradiated with active energy rays (ultraviolet; UV) under the same active energy irradiation conditions as in Test Example 1 to cure the adhesive layer. The resulting laminate was then irradiated with ultraviolet light (S-UV irradiation). Then, the adhesive layer was separated from the two soda-lime glass plates for the laminate after S-UV irradiation. For the adhesive of the separated adhesive layer, the average peak molecular weight (Mp; after S-UV) of the sol component was measured in the same manner as above. The results are shown in Table 2.

[0291] [Experimental Example 3] (Determination of Dynamic Viscoelasticity)

[0292] By stacking the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples, an adhesive layer with a thickness of 250 μm was prepared. The adhesive layer (250 μm) was irradiated with active energy rays (ultraviolet; UV) under the same active energy irradiation conditions as in Test Example 1, causing the adhesive layer to cure. A cylinder with a diameter of 8 mm (height of 0.25 mm) was punched from the active energy irradiated cured adhesive layer (250 μm) and used as a sample.

[0293] For the above samples, according to JIS K7244-1, using a viscoelasticity measuring apparatus (Anton Paar, product name "MCR302"), the dynamic viscoelasticity was measured under the following conditions by torsional shear method: storage modulus G'(-15) (MPa; before S-UV) at -15°C, storage modulus G'(23) (MPa; before S-UV) at 23°C, and storage modulus G'(100) (MPa; before S-UV) at 100°C. In addition, the peak temperature (°C) of the loss tangent tanδ (before S-UV: Tb) was also observed. The results are shown in Table 2.

[0294] Measurement frequency: 1Hz

[0295] Measurement temperature range: -20℃~140℃

[0296] Heating rate: 4℃ / minute

[0297] Furthermore, an adhesive layer with a thickness of 250 μm was prepared by laminating the adhesive layer of the adhesive sheet manufactured in the multilayer examples and comparative examples. Using this adhesive layer (thickness: 250 μm), a laminate was prepared in the same manner as in Test Example 1. The laminate was irradiated with active energy rays (ultraviolet; UV) under the same active energy irradiation conditions as in Test Example 1 to cure the adhesive layer. The resulting laminate was irradiated with ultraviolet light (S-UV irradiation) under the same ultraviolet irradiation conditions as in Test Example 1. Then, the adhesive layer was separated from the two soda-lime glass plates after S-UV irradiation. For the separated adhesive layer, the dynamic viscoelasticity was measured in the same manner as above, and the storage modulus G'(-15) at -15°C (MPa; after S-UV), the storage modulus G'(23) at 23°C (MPa; after S-UV), and the storage modulus G'(100) at 100°C (MPa; after S-UV) were observed. In addition, the peak temperature (°C) of the loss tangent tanδ (after S-UV: Ta) was also observed. The results are shown in Table 2.

[0298] Furthermore, the value of Ta minus Tb (Ta-Tb) obtained above is calculated. The results are shown in Table 2.

[0299] [Experimental Example 4] (Determination of Adhesion)

[0300] Release sheet R2 was peeled from the adhesive sheet manufactured in the examples and comparative examples. The exposed adhesive layer was then bonded to an easy-to-adhere layer of a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO.,LTD., product name "Cosmoshine A4360", thickness: 100 μm) with easy-to-adhere layers on both sides, resulting in a laminate of release sheet R1 / adhesive layer / PET film. This laminate was cut into pieces 25 mm wide and 100 mm long and used as a sample.

[0301] At 23°C and 50% RH, the release tab R1 was peeled off from the above sample, and the exposed adhesive layer was applied to soda-lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). The mixture was then pressurized for 20 minutes at 0.5 MPa and 50°C using an autoclave manufactured by Kurihara Seisakusho. Then, through the soda-lime glass, the adhesive layer was irradiated with active energy rays (ultraviolet; UV) under the same conditions as in Test Example 1 to cure the adhesive layer.

[0302] Then, after being placed at 23°C and 50% RH for 24 hours, the adhesion (N / 25mm) was measured using a tensile testing machine (manufactured by ORIENTEC, TENSILON) at a peel speed of 300 mm / min and a peel angle of 180 degrees. Conditions not described here were measured according to JIS Z0237:2009. The results are shown in Table 2.

[0303] [Experimental Example 5] (Determination of Total Transmittance)

[0304] By laminating the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples, an adhesive layer with a thickness of 250 μm was prepared. Using this adhesive layer (thickness: 250 μm), a laminate was prepared in the same manner as in Test Example 1. The laminate was irradiated with active energy rays (ultraviolet; UV) under the same active energy irradiation conditions as in Test Example 1 to cure the adhesive layer, and it was used as a sample for testing.

[0305] For the samples used in the above tests, based on background measurements using soda-lime glass, the total transmittance (%) was measured using a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd., product name "NDH-5000") according to JIS K7361-1:1997. The results are shown in Table 2. In addition, the total transmittance of the adhesive layer before curing with active energy rays was also measured, and the results were the same.

[0306] [Experimental Example 6] (Determination of Haze Value)

[0307] The test sample was prepared in the same manner as in Test Example 5. For this test sample, based on background measurements using glass, the haze value (%; before S-UV) was measured using a haze meter (manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd., product name "NDH-5000") according to JIS K7136:2000. The results are shown in Table 2. Additionally, the haze value of the adhesive layer before curing with active energy rays was also measured, and the results were the same.

[0308] [Experimental Example 7] (Determination of L*a*b*)

[0309] By laminating the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples, an adhesive layer with a thickness of 250 μm was prepared. Using this adhesive layer (thickness: 250 μm), a laminate was prepared in the same manner as in Test Example 1. The laminate was irradiated with active energy rays (ultraviolet; UV) under the same active energy irradiation conditions as in Test Example 1 to cure the adhesive layer. For the obtained laminate, the chromaticity b* (chromaticity b*1) specified by the CIE 1976 L*a*b* color system was measured using a simultaneous spectrophotometer (manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd., product name "SQ2000"). The results are shown in Table 2.

[0310] Furthermore, the resulting laminate was irradiated with ultraviolet light (S-UV irradiation) under the same conditions as in Test Example 1. The colorimetric b* (colorimetric b*2) of the adhesive layer after S-UV irradiation was measured in the same manner as described above. The results are shown in Table 2.

[0311] Furthermore, the absolute value of the ratio (b*2 / b*1) of the aforementioned chromaticity b*2 was calculated. In addition, based on this result, yellowing was evaluated according to the following criteria. The results are shown in Table 2.

[0312] ◎…The absolute value of b*2 / b*1 is less than 3.

[0313] ○… The absolute value of b*2 / b*1 is greater than 3 and less than 6.

[0314] The absolute value of △…b*2 / b*1 is greater than 6 and less than 10.

[0315] The absolute value of ×…b*2 / b*1 is greater than 10.

[0316] [Experimental Example 8] (Evaluation of Weather Resistance)

[0317] By laminating the adhesive layers of the adhesive sheets manufactured in the multilayer examples and comparative examples, an adhesive layer with a thickness of 250 μm was prepared. Using this adhesive layer (thickness: 250 μm), a laminate was prepared in the same manner as in Test Example 1. The laminate was irradiated with active energy rays (ultraviolet; UV) under the same conditions as in Test Example 1 to cure the adhesive layer. Then, except that the UV irradiation time was set to 20 hours (light intensity: 7.2 kJ / cm²), the adhesive layer was cured. 2 ), 40 hours (light intensity: 14.4 kJ / cm²) 2 ), 80 hours (light intensity: 28.8 kJ / cm²) 2 ) and 120 hours (light intensity: 43.2 kJ / cm²) 2Except for the conditions described in Test Example 1, the resulting laminate was irradiated with ultraviolet light under the same conditions. The adhesive layer was then visually inspected, and weather resistance was evaluated according to the following criteria. The results are shown in Table 2.

[0318] ◎…No needle-like cracks, bubbles, floating, or peeling were produced.

[0319] ○…No needle-like cracks were produced, but some bubbles were generated.

[0320] ×… produces needle-like cracks.

[0321] [Experimental Example 9] (Evaluation of Anti-foaming Properties)

[0322] Release sheet R2 was peeled off from the adhesive sheet manufactured in the examples and comparative examples, and the exposed adhesive layer was adhered to the PC board side of a plastic sheet (manufactured by MITSUBISHI GASCHEMICAL COMPANY, INC., product name "Iupilon Sheet MR58U", thickness: 0.7 mm) on which a polymethyl methacrylate (PMMA) layer was laminated on a polycarbonate (PC) board. Then, release sheet R1 was peeled off from the adhesive layer to expose the adhesive layer, and a transparent conductive film (manufactured by OIKE&Co., Ltd., a laminate of PET film and ITO layer (ITO-PET film, total thickness 125 μm) was adhered to the adhesive layer with its ITO layer side in contact with the adhesive layer. Next, an autoclave treatment was performed at 50°C and 0.5 MPa for 20 minutes.

[0323] Under the same conditions as in Example 1, the adhesive layer of the obtained laminate was irradiated with active energy rays (ultraviolet; UV) through the aforementioned transparent conductive film to cure the adhesive layer. Then, it was placed at normal pressure, 23°C, and 50% RH for 24 hours to obtain a sample.

[0324] The obtained samples were stored at 85°C and 85% RH for 72 hours. Then, the state of the interface between the adhesive layer and the substrate (plastic sheet) was visually confirmed, and the anti-foaming property was evaluated according to the following criteria. The results are shown in Table 2.

[0325] 〇…No bubbles, floating, or peeling were produced at all.

[0326] △… Bubbles with a diameter of less than 1 mm were generated, but no floating or peeling occurred.

[0327] ×... The whole thing produces bubbles or floats up or peels off.

[0328] [Table 1]

[0329]

[0330] [Table 2]

[0331]

[0332] As shown in Table 2, the adhesive sheets manufactured in the examples can suppress the formation of needle-like cracks even after prolonged exposure (20 hours / 40 hours / 80 hours) to high-intensity ultraviolet light, demonstrating excellent weather resistance. In particular, the adhesive sheets of Examples 2-5, which use ultraviolet absorbers, light stabilizers, or antioxidants, can suppress the formation of needle-like cracks even after further prolonged exposure (120 hours) to high-intensity ultraviolet light, exhibiting even better weather resistance.

[0333] Industrial applicability

[0334] The adhesive sheet of the present invention can be suitably used, for example, during the manufacture of a display body to protect the bonding of display body components such as panels to desired display body components.

[0335] Explanation of reference numerals in the attached figures

[0336] 1: Adhesive sheet; 11: Adhesive layer; 12a, 12b: Release sheet; 2: Display body; 21: First display body component; 22: Second display body component; 3: Printed layer.

Claims

1. An adhesive for optical applications, comprising an oxygen absorber.

2. The adhesive according to claim 1, characterized in that, The oxygen absorbent is a compound represented by the following general formula (I). [Chemical Formula 1] In general formula (I), X and Y each independently represent a chalcogenide atom, and R 1 R 2 R 7 and R 8 Each independently represents any one of alkyl, alkenyl, aryl, and aralkyl groups having 1 to 6 carbon atoms, R 3 R 4 R 5 and R 6 Each of the following independently represents any one of hydrogen atom, alkyl group having 1 to 6 carbon atoms, alkenyl group having 2 to 6 carbon atoms, aryl group, and aralkyl group; J represents a linking group composed of aliphatic hydrocarbons having 3 to 15 carbon atoms, wherein any carbon atom of the linking group may be optionally replaced by an oxygen atom, or the linking group may optionally have at least one of the following groups as a substituent: hydroxyl, (meth)acryloyloxy, styryloxy, and alkenyloxy having 2 to 5 carbon atoms; n is any integer from 1 to 5; wherein, when multiple Y and R are present... 5 R 6 R 7 and R 8 At that time, Y, R 5 R 6 R 7 and R 8 These can be chosen from different atoms or groups.

3. The adhesive according to claim 1, characterized in that, The oxygen absorbent is a compound represented by the following general formula (II). [Chemical Formula 2] In general formula (II), R 9 R represents a hydrogen atom or a methyl group. 10 It represents any one of hydroxyl, (meth)acryloyloxy, styryloxy, and alkenyloxy with 2 to 5 carbon atoms; R 11 R 12 R 13 and R 14 Each can independently represent any one of alkyl, alkenyl, aryl, and aralkyl groups having 1 to 6 carbon atoms.

4. The adhesive according to claim 1, characterized in that, The oxygen absorbent is a compound represented by the following formula (III). [Chemical Formula 3] 5. The adhesive according to claim 1, characterized in that, The adhesive is an acrylic adhesive.

6. The adhesive according to claim 1, characterized in that, The adhesive is a (meth)acrylate polymer or its crosslinked product.

7. The adhesive according to claim 1, characterized in that, The adhesive is an adhesive that can be cured by active energy rays.

8. An adhesive sheet having an adhesive layer for bonding two components together, characterized in that, At least one of the components is an optical component. The adhesive layer is composed of the adhesive according to any one of claims 1 to 7.

9. The adhesive sheet according to claim 8, characterized in that, The chromaticity b* of the bonded adhesive layer, as specified in the CIE 1976 L*a*b* color system, is set to b*1, and the bonded adhesive layer is irradiated for 120 hours at an illuminance of 100 mW / cm². 2 When the chromaticity b* of the adhesive layer after ultraviolet light exposure is set to b*2 according to the CIE 1976 L*a*b* color system,... The absolute value of the ratio of b*2 to b*1 is less than 10.

10. The adhesive sheet according to claim 8, characterized in that, The adhesive sheet has two release tabs, and the adhesive layer is held by the release tabs in such a way that it contacts the release surfaces of the two release tabs.

11. An optical component comprising at least two components bonded together using an adhesive layer, characterized in that, At least one of the components is an optical component. The adhesive layer is formed by the adhesive according to any one of claims 1 to 7.

12. A display body comprising a display body component, another display body component, and an adhesive layer for bonding the one display body component and the other display body component together, characterized in that, The adhesive layer is formed from the adhesive layer of the adhesive sheet as described in claim 8.

13. The display body according to claim 12, characterized in that, Both the one display component and the other display component are made of rigid board.

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