CN121002139A

CN121002139A - Adhesive sheet and display body

Info

Publication number: CN121002139A
Application number: CN202480022086.XA
Authority: CN
Inventors: 山田将希; 小鲭翔; 高桥洋一; 仓田雄一
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2023-03-30
Filing date: 2024-02-22
Publication date: 2025-11-21
Also published as: TW202440838A; KR20250166907A; WO2024202755A1; JPWO2024202755A1

Abstract

The present invention provides an adhesive sheet 1 having an adhesive layer 11 for bonding two display constituent members to each other, wherein the adhesive constituting the adhesive layer 11 is an active energy ray-curable adhesive, and when the peak temperature of the loss tangent tan delta of the adhesive constituting the adhesive layer 11' after active energy ray curing is Tb (° C), and the peak temperature of the loss tangent tan delta of the adhesive constituting the adhesive layer 11' after active energy ray curing is Ta (° C) after 120 hours of irradiation of ultraviolet rays of illuminance 100mW/cm ² to the adhesive layer 11', the value obtained by subtracting Tb from Ta is greater than 3. The adhesive sheet 1 can suppress the occurrence of needle-like cracks and is excellent in weather resistance.

Description

Adhesive sheet and display

Technical Field

The present invention relates to an adhesive sheet for bonding two display constituent members to each other, and a display obtained by using an adhesive layer of the adhesive sheet.

Background

Various mobile electronic devices such as mobile phones, smart phones, and tablet terminals in recent years include a display (display) using a display module including a liquid crystal module, a Light Emitting Diode (LED) module, and an organic electroluminescence (organic EL) module.

In the display as described above, a protective panel is generally provided on the front surface side of the display body module. With the reduction in thickness and weight of electronic devices, the protective panel has been changed from a conventional glass plate to a plastic plate such as an acryl plate or a polycarbonate plate.

Here, a gap is provided between the protective panel and the display module so that the deformed protective panel does not strike the display module even when the protective panel is deformed by an external force.

However, if there is a void, i.e., an air layer, as described above, reflection loss of light due to 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 is large, and there is a problem that the image quality of the display is deteriorated.

Accordingly, it has been proposed to fill the gap between the protective panel and the display module with an adhesive layer, thereby improving the image quality of the display. For example, patent document 1 discloses an adhesive layer as an adhesive layer filling a gap between a protective panel and a display module, having a shear storage modulus (G') at 25 ℃ and 1Hz of 1.0×10 ⁵ Pa or less, and a gel fraction of 40% or more.

Prior art literature

Patent literature

Patent document 1 Japanese patent laid-open publication No. 2010-97070

Disclosure of Invention

First, the technical problem to be solved

Sometimes, when a display obtained using the adhesive layer as described above is irradiated with ultraviolet rays of high intensity for a long period of time, needle-like cracks may occur in the adhesive layer. In particular, such a problem is likely to occur when an accelerated weather resistance test is performed by irradiating high-intensity ultraviolet rays for a long period of time.

The present invention has been made in view of such circumstances, and an object thereof is to provide an adhesive sheet and a display that can suppress the occurrence of needle-like cracks and have excellent weather resistance.

(II) technical scheme

In order to achieve the above object, in a first aspect, the present invention provides an adhesive sheet having an adhesive layer for bonding two display constituent members to each other, wherein the adhesive constituting the adhesive layer is an active energy ray-curable adhesive, and when a peak temperature of a loss tangent tan δ of the adhesive constituting the adhesive layer after active energy ray curing is set to Tb (° C), and a peak temperature of the loss tangent tan δ of the adhesive constituting the adhesive layer after active energy ray curing after irradiation of ultraviolet rays of an illuminance of 100mW/cm ² for 120 hours is set to Ta (° C), a value obtained by subtracting Tb from Ta is greater than 3 (invention 1).

In the adhesive layer of the adhesive sheet according to the invention (1), even when high-intensity ultraviolet rays are irradiated for a long period of time (for example, 20 hours, 40 hours, etc.), breakage of the crosslinking points, which are the starting points of the needle-like cracks, can be suppressed, and good adhesion to the display constituent members can be exhibited. As a result, the adhesive sheet can suppress the occurrence of needle-like cracks, and is excellent in weather resistance.

In the above invention (invention 1), the adhesive constituting the adhesive layer preferably has a gel fraction of 20% or more and 85% or less (invention 2).

In the above inventions (inventions 1 and 2), the adhesive constituting the adhesive layer after the curing by the active energy rays preferably has a gel fraction of 30% to 95% (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that the adhesive layer after the active energy ray curing is irradiated with ultraviolet rays having an illuminance of 100mW/cm ² for 120 hours, and the gel fraction of the adhesive constituting the adhesive layer is 40% to 99% (invention 4).

In the above inventions (inventions 1 to 4), the average peak molecular weight of the sol component constituting the adhesive of the adhesive layer after the curing by the active energy rays is preferably 1 to 25 ten thousand (invention 5).

In the above inventions (inventions 1 to 5), the adhesive layer after curing with active energy rays is preferably irradiated with ultraviolet rays having an illuminance of 100mW/cm ² for 120 hours, and then the adhesive constituting the adhesive layer has an average peak molecular weight of 1 to 20 ten thousand inclusive (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that the adhesive constituting the adhesive layer after the curing by the active energy rays has a storage modulus G' at 23 ℃ of 0.01MPa to 2MPa (invention 7).

In the above inventions (inventions 1 to 7), it is preferable that the adhesive agent constituting the adhesive agent layer after irradiation of the ultraviolet light of 100mW/cm ² for 120 hours on the adhesive agent layer after curing with active energy rays has a storage modulus G' at 23 ℃ of 0.01MPa or more and 2MPa or less (invention 8).

In the above inventions (inventions 1 to 8), it is preferable that the adhesive constituting the adhesive layer after the curing by the active energy rays has a storage modulus G' at-15 ℃ of 0.01MPa to 100MPa (invention 9).

In the above inventions (inventions 1 to 9), it is preferable that the adhesive agent constituting the adhesive agent layer after the active energy ray curing is irradiated with ultraviolet rays having an illuminance of 100mW/cm ² for 120 hours has a storage modulus G' at-15 ℃ of 0.1MPa or more and 1000MPa or less (invention 10).

In the above inventions (inventions 1 to 10), it is preferable that the adhesive constituting the adhesive layer after the curing by the active energy rays has a storage modulus G' at 100 ℃ of 0.0001MPa to 1MPa (invention 11).

In the above inventions (inventions 1 to 11), it is preferable that the adhesive agent constituting the adhesive agent layer after irradiation of the ultraviolet light of 100mW/cm ² for 120 hours on the adhesive agent layer after curing with active energy rays has a storage modulus G' of 0.0001MPa or more and 1MPa or less at 100 ℃.

In the above inventions (inventions 1 to 12), the adhesive is preferably an acrylic adhesive (invention 13).

In the above inventions (inventions 1 to 13), the pressure-sensitive adhesive sheet preferably includes 2 release sheets, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the 2 release sheets (invention 14).

In a second aspect, the present invention provides a display including one display constituent member, another display constituent member, and an adhesive layer for bonding the one display constituent member and the other display constituent member to each other, wherein the adhesive layer is formed of an adhesive layer of the adhesive sheet (inventions 1 to 14) (invention 15).

In the invention (invention 15), the one display element constituent member and the other display element constituent member may be both hard plates (invention 16).

(III) beneficial effects

The adhesive sheet and the display of the present invention can suppress the occurrence of needle-like cracks and are excellent in weather resistance.

Drawings

Fig. 1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of a display body according to an embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention are described.

[ Adhesive sheet ]

The adhesive sheet of this embodiment has an adhesive layer for bonding two display element constituent members to each other. The specific structure of the adhesive sheet and the constituent members of the display body will be described in detail later.

The adhesive constituting the adhesive layer in the adhesive sheet of the present embodiment is an active energy ray-curable adhesive. In the adhesive sheet of the present embodiment, when the peak temperature of the loss tangent tan δ of the adhesive constituting the adhesive layer after the active energy ray curing is set to Tb (°c), and the peak temperature of the adhesive constituting the adhesive layer after the active energy ray curing after the irradiation (hereinafter, also sometimes referred to as "S-UV irradiation") of ultraviolet light of illuminance 100mW/cm ² for 120 hours is set to Ta (°c), it is preferable that the value obtained by subtracting Tb from Ta is greater than 3 (Ta-Tb > 3). The method for measuring the loss tangent tan δ is as shown in the test example described below.

Here, the term "adhesive layer after active energy ray curing" as used herein refers to an adhesive layer after the adhesive layer is completely cured by active energy ray irradiation. Specifically, the adhesive layer after the active energy ray curing is an adhesive layer having a gel fraction increase rate of 10% or less, particularly an adhesive layer having a gel fraction increase rate of 5% or less, when the adhesive layer is further irradiated with active energy rays at the same radiation amount (light amount) as in the active energy ray curing. In this specification, "relative humidity α%" may be referred to as "α% RH" (RH; relative humidity).

It is considered that when ultraviolet rays of high intensity are irradiated for a long time as described above, the crosslinked structure of the adhesive changes, and needle-shaped cracks are generated. In contrast, in the adhesive of the present application, by satisfying the above-described relational expression, the peak temperature of the loss tangent tan δ shifts to the high temperature side after S-UV irradiation, and the point at which the viscosity of the adhesive increases in viscoelasticity shifts from the low temperature side to the normal temperature side. As a result, even when high-intensity ultraviolet light is irradiated for a long period of time (for example, 20 hours, 40 hours, etc.), breakage of the cross-linking points, which are the starting points of the needle-like cracks, can be suppressed, and good adhesion to the display constituent member can be exhibited. As described above, the adhesive sheet according to the embodiment of the present application can suppress the occurrence of needle-shaped cracks and is excellent in weather resistance.

From the viewpoint of suppressing the occurrence of the needle-like cracks, ta-Tb has a value of more preferably 4 or more, more preferably 5 or more, particularly preferably 6, and further preferably 7, and among these, preferably 8 or more. On the other hand, the upper limit value of Ta to Tb is preferably 30 or less, more preferably 24 or less, particularly preferably 18 or less, further preferably 15 or less, and particularly preferably 12 or less, from the viewpoint of moderately shifting the point at which the viscosity of the adhesive agent increases in viscoelasticity to the normal temperature side.

The peak temperature Ta of the loss tangent tan δ of the adhesive after S-UV irradiation of the active energy ray-cured adhesive layer (hereinafter, sometimes simply referred to as "adhesive after S-UV irradiation") is preferably-30 ℃ to 30 ℃, more preferably-20 ℃ to 20 ℃, particularly preferably-10 ℃ to 10 ℃, further preferably-5 ℃ to 5 ℃, and among them, is preferably-4 ℃ to 2 ℃. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

The peak temperature Tb of the loss tangent tan delta of the adhesive after the active energy ray curing (before the S-UV irradiation) is preferably-30 to 30 ℃, more preferably-25 to 20 ℃, particularly preferably-20 to 10 ℃, further preferably-15 to 5 ℃, and particularly preferably-10 to 0 ℃. Thus, the value of Ta-Tb as described above easily falls within a preferable range, and furthermore, good adhesion after active energy ray curing is easily obtained.

The gel fraction of the adhesive constituting the adhesive layer in the adhesive sheet of the present embodiment is preferably 20 to 85%, more preferably 30 to 80%, particularly preferably 40 to 75%, further preferably 46 to 70%, and among these, 52 to 67%. Thus, when an adherend is attached, good adhesion is easily exhibited. The method for measuring the gel fraction in the present specification is as shown in the test examples described below.

The gel fraction of the adhesive constituting the adhesive layer after active energy ray curing in the adhesive sheet of the present embodiment is preferably 30 to 95%, more preferably 40 to 92%, particularly preferably 50 to 90%, further preferably 60 to 88%, and among these, 70 to 86%. This makes it easy to improve the adhesion after the display element constituent members are bonded.

The gel fraction of the adhesive after S-UV irradiation is preferably 40 to 99%, more preferably 55 to 98%, particularly preferably 70 to 97%, further preferably 78 to 96%, and particularly preferably 84 to 95%. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

The adhesive agent constituting the adhesive agent layer after the active energy ray curing in the adhesive sheet of the present embodiment preferably has an average peak molecular weight of 1 to 25 ten thousand, more preferably 3 to 20 ten thousand, particularly preferably 5 to 15 ten thousand, further preferably 6 to 10 ten thousand, and particularly preferably 6.2 to 7.5 ten thousand. This makes it easy to improve the adhesion after the display element constituent members are bonded. The average peak molecular weight of the sol component in the present specification is a value in terms of standard polystyrene measured by gel permeation chromatography (Gel Permeation Chromatography, GPC). Specific measurement methods are shown in test examples described below.

The average peak molecular weight of the sol component of the adhesive after S-UV irradiation is preferably 1 to 20 ten thousand, more preferably 3 to 16 ten thousand, particularly preferably 4 to 12 ten thousand, further preferably 5 to 8 ten thousand, and particularly preferably 5.5 to 7 ten thousand. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

The adhesive constituting the adhesive layer after active energy ray curing in the adhesive sheet of the present embodiment preferably has a storage modulus G' at 23 ℃ of 0.01 to 2mpa, preferably 0.04 to 1mpa, more preferably 0.08 to 0.8mpa, particularly preferably 0.12 to 0.6mpa, further preferably 0.15 to 0.5mpa, and among these, 0.18 to 0.4mpa is preferred. This makes it easy to improve the adhesion after the display element constituent members are bonded. The method for measuring the storage modulus G' in the present specification is as shown in the test examples described below.

The storage modulus G' of the adhesive after S-UV irradiation at 23 ℃ is preferably 0.01 to 2MPa, more preferably 0.05 to 1.5MPa, still more preferably 0.1 to 1MPa, particularly preferably 0.15 to 0.8MPa, and still more preferably 0.18 to 0.6MPa. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

The adhesive agent constituting the adhesive layer after active energy ray curing in the adhesive sheet of the present embodiment preferably has a storage modulus G' at-15 ℃ of 0.01 to 100mpa, preferably 0.1 to 80mpa, more preferably 1 to 60mpa, particularly preferably 1 to 40mpa, further preferably 5 to 30mpa, and among these, 10 to 30mpa is preferred. This makes it easy to improve the adhesion at low temperature after the display element constituent members are bonded.

The storage modulus G' of the adhesive after S-UV irradiation at-15 ℃ is preferably 0.1 to 1000MPa, more preferably 1 to 500MPa, still more preferably 5 to 200MPa, particularly preferably 10 to 100MPa, still more preferably 18 to 50MPa. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

The adhesive constituting the adhesive layer after active energy ray curing in the adhesive sheet of the present embodiment preferably has a storage elastic modulus G' at 100 ℃ of 0.0001 to 1mpa, preferably 0.001 to 0.7mpa, more preferably 0.005 to 0.4mpa, particularly preferably 0.01 to 0.2mpa, further preferably 0.02 to 0.1mpa, and particularly preferably 0.03 to 0.07mpa. This makes it easy to improve the adhesion at high temperature after the display element constituent members are bonded.

The storage modulus G' of the adhesive after S-UV irradiation at 100℃is preferably 0.0001 to 1MPa, more preferably 0.0005 to 0.7MPa, still more preferably 0.001 to 0.4MPa, particularly preferably 0.005 to 0.2MPa, further preferably 0.01 to 0.1MPa, and particularly preferably 0.02 to 0.09MPa. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

The adhesive force of the active energy ray-cured adhesive layer (before S-UV irradiation) in the adhesive sheet of the present embodiment to soda lime glass is preferably 1 to 100N/25mm, more preferably 5 to 75N/25mm, particularly preferably 10 to 50N/25mm, and further preferably 15 to 35N/25mm. This makes it easy to obtain excellent weather resistance and foaming resistance. The above-mentioned adhesive force basically means an adhesive force measured by a 180-degree stretch-stripping method according to JIS Z0237:2009, and a specific test method is shown in a test example described later.

The adhesive layer after curing with active energy rays (before S-UV irradiation) in the adhesive sheet of the present embodiment preferably has a total light transmittance of 80% or more, more preferably 90% or more, particularly preferably 95% or more, and further preferably 99% or more. This provides a very high transparency, and can be suitably used for optical applications (for display bodies). The upper limit of the total light transmittance is not particularly limited, and may be 100%, or may be a value slightly exceeding 100% in terms of measurement. The total light transmittance of the adhesive layer before curing by active energy rays and the adhesive layer after S-UV irradiation is also preferably in the same numerical range as that of the adhesive layer before S-UV irradiation. The total light transmittance in the present specification is a value measured in accordance with JIS K7361-1:1997, and a specific test method is shown in the test example described below.

The haze value of the adhesive layer (before S-UV irradiation) after active energy ray curing in the adhesive sheet of the present embodiment is preferably 2% or less, and particularly preferably 1% or less. This provides a very high transparency, and can be suitably used for optical applications (for display bodies). The lower limit of the haze value is not particularly limited and may be 0%. The haze value of the adhesive layer before curing by active energy rays and the haze value of the adhesive layer after S-UV irradiation are also preferably in the same numerical range as the haze value of the adhesive layer before S-UV irradiation. The haze value in the present specification is a value measured in accordance with JIS K7136:2000, and a specific test method is shown in the test example described below.

The chromaticity b (chromaticity b 1) of the adhesive layer after the active energy ray curing in the adhesive sheet of the present embodiment, which is defined by CIE1976l×a×b×color system, is preferably-20 to 20, more preferably-10 to 10, particularly preferably-5 to 5, further preferably-1 to 1, and among them, is preferably-0.5 to 0.5. Thus, the adhesive layer is made almost colorless and transparent, and is suitable for optical applications.

The chromaticity b (chromaticity b) of the adhesive layer after S-UV irradiation of the adhesive layer after active energy ray curing, which is defined by CIE1976l×a×b×color system, is preferably 20 to 20, more preferably-10 to 10, particularly preferably-6~6, further preferably-2 to 2, and among these, is preferably-1 to 1. Thus, the adhesive layer was less yellow even after S-UV irradiation, and it was said to be excellent in weather resistance from the viewpoint of chromaticity.

The absolute value of the ratio (b×2/b×1) of the chromaticity b×2 to the chromaticity b×1 is preferably 20 or less, more preferably 15 or less, particularly preferably 10 or less, further preferably 5 or less, and among these, 2 or less. Thus, the adhesive layer was less in yellowing amount even after S-UV irradiation, and it was said to be excellent in weather resistance from the viewpoint of chromaticity. The lower limit of the absolute value of the ratio (b×2/b×1) is not particularly limited, and is most preferably 1.

The adhesive constituting the adhesive layer in the present embodiment is an active energy ray-curable adhesive, and the type thereof may be any of an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, and the like. Further, the adhesive may be any of a latex type, a solvent type, or a solvent-free type, and may be any of a crosslinked type or a non-crosslinked type. Among them, an acrylic adhesive excellent in adhesive properties, optical properties and the like is preferable.

The adhesive constituting the adhesive layer in this embodiment preferably contains a (meth) acrylate polymer, and particularly preferably contains a crosslinked product of the (meth) acrylate polymer as an adhesive main agent. In addition, the adhesive constituting the adhesive layer in the present embodiment preferably contains an adhesive main agent and an active energy ray-curable component. That is, the adhesive constituting the adhesive layer in this embodiment preferably contains a crosslinked product of a (meth) acrylate polymer and an active energy ray-curable component. The crosslinked product of the (meth) acrylate polymer is preferably a crosslinked product of the (meth) acrylate polymer and a crosslinking agent.

Specifically, the adhesive constituting the adhesive layer in the present embodiment is preferably formed by crosslinking (preferably thermally crosslinking) an adhesive composition (hereinafter, sometimes referred to as "adhesive composition P") containing the (meth) acrylate polymer (a), the crosslinking agent (B) and the active energy ray-curable component (C). In the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. Other similar terms are also the same. In addition, the term "polymer" also includes the concept of "copolymer".

(1) Each component is composed of

(1-1) (Meth) acrylate Polymer (A)

The (meth) acrylate polymer (A) preferably contains structural units derived from alkyl (meth) acrylates. Thereby the processing time of the product is reduced, can exhibit good results good adhesion. The hard monomer described later is not included in the alkyl (meth) acrylate.

The alkyl (meth) acrylate is preferably one in which the alkyl group has 1 to 20 carbon atoms from the viewpoint of adhesion. Examples of the alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group include methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. These may be used alone or in combination of two or more. Among the above, from the viewpoint of further improving the adhesion, an alkyl (meth) acrylate having 1 to 14 carbon atoms as an alkyl group is preferable, an alkyl (meth) acrylate having 2 to 10 carbon atoms as an alkyl group is more preferable, and an alkyl (meth) acrylate having 3 to 8 carbon atoms as an alkyl group is particularly preferable. Specifically, methyl acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, or isooctyl (meth) acrylate is preferable, and n-butyl acrylate or 2-ethylhexyl acrylate is particularly preferable.

The (meth) acrylate polymer (a) preferably contains 99 mass% or less of a structural unit derived from an alkyl (meth) acrylate, more preferably 96 mass% or less of a structural unit derived from an alkyl (meth) acrylate, and particularly preferably 92 mass% or less of a structural unit derived from an alkyl (meth) acrylate, from the viewpoint of imparting tackiness. In addition, when an acid-free adhesive is used as the adhesive, it is preferable to contain 85 mass% or less of a structural unit derived from an alkyl (meth) acrylate, more preferably 80 mass% or less of a structural unit derived from an alkyl (meth) acrylate, particularly preferably 75 mass% or less of a structural unit derived from an alkyl (meth) acrylate, and still more preferably 70 mass% or less of a structural unit derived from an alkyl (meth) acrylate, because of compatibility with an adherend to be adhered. On the other hand, the lower limit value is preferably 40% by mass or more, more preferably 48% by mass or more, particularly preferably 54% by mass or more, and further preferably 60% by mass or more. In addition, when the obtained adhesive contains an acid component, the structural unit is preferably contained in an amount of 70 mass% or more, more preferably 75 mass% or more, particularly preferably 80 mass% or more, and further preferably 85 mass% or more, because of compatibility with the object to be adhered.

The (meth) acrylate polymer (a) preferably has structural units derived from a reactive functional group-containing monomer. Thus, the reactive functional group derived from the reactive group-containing monomer reacts with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), and an adhesive having a desired cohesive force is obtained.

The reactive group-containing monomer is preferably a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), or the like. Among them, a hydroxyl group-containing monomer or a carboxyl group-containing monomer excellent in reactivity with the crosslinking agent (B) is preferable.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is preferable from the viewpoints of reactivity with the crosslinking agent (B) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids (ethylene unsaturated carboxylic acid) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid or methacrylic acid is preferable, and acrylic acid is particularly preferable, from the viewpoints of reactivity with the crosslinking agent (B) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

The content of the structural unit derived from the reactive functional group-containing monomer in the (meth) acrylate polymer (a) is preferably 1 to 40 mass%, more preferably 3 to 32 mass%, particularly preferably 6 to 26 mass%, and further preferably 8 to 22 mass%, from the viewpoint of the cohesive force. Among them, when an acid free adhesive is preferably used as the adhesive to be obtained, the content is preferably 12 to 21% by mass, particularly preferably 16 to 20% by mass, or when an adhesive containing an acid component is preferably used, the content is preferably 9 to 14% by mass.

The (meth) acrylate polymer (a) preferably further contains a structural unit derived from a hard monomer having a glass transition temperature (Tg) of 70 ℃ or more as a homopolymer. In addition, the aforementioned reactive functional group-containing monomer is not included in the hard monomer. Thus, the cohesive force of the obtained adhesive can be improved, and excellent foaming resistance can be easily obtained. In particular, when the structural unit derived from a (meth) acrylate having 5 to 8 carbon atoms in the alkyl group is contained, the cohesive force tends to be reduced, and therefore, the structural unit derived from the hard monomer is preferably contained. The glass transition temperature (Tg) of the hard monomer as a homopolymer is preferably 75 to 200 ℃, particularly preferably 80 to 180 ℃, and further preferably 90 to 150 ℃.

Examples of the hard monomer include methyl methacrylate (Tg 105 ℃, isobornyl acrylate (Tg 94 ℃), isobornyl methacrylate (Tg 180 ℃), adamantyl acrylate (Tg 115 ℃) and adamantyl methacrylate (Tg 141 ℃), and two or more of them may be used singly or in combination.

Among the hard monomers, methyl methacrylate or isobornyl acrylate is more preferable from the viewpoint of preventing adverse effects on other characteristics such as adhesion and transparency and further exhibiting the performance of the hard monomer. In particular, methyl methacrylate is preferable from the viewpoint of weather resistance, and isobornyl acrylate which is a monomer having an alicyclic structure (alicyclic structure-containing monomer) in the molecule is particularly preferable from the viewpoint of adhesion.

When the (meth) acrylate polymer (a) contains a structural unit derived from the hard monomer, the content thereof is preferably 1 to 35% by mass, more preferably 4 to 28% by mass, particularly preferably 8 to 22% by mass, and even more preferably 12 to 17% by mass, from the viewpoint of easily exhibiting desired aggregation force and viscoelasticity, and foaming resistance.

The (meth) acrylate polymer (a) also preferably contains a structural unit derived from a monomer having a nitrogen atom in the molecule (a nitrogen atom-containing monomer). In the case of using an alicyclic structure-containing monomer, particularly isobornyl acrylate, as the hard monomer, it is preferable that the monomer contains a structural unit derived from a nitrogen atom-containing monomer. By the presence of the structural unit derived from the nitrogen atom-containing monomer, a predetermined polarity can be imparted to the adhesive, and the adhesive properties can be further improved.

The nitrogen atom-containing monomer is preferably a monomer having a nitrogen-containing heterocycle from the viewpoint of imparting moderate rigidity to the (meth) acrylate polymer (a). In addition, from the viewpoint of improving the degree of freedom of a portion derived from a nitrogen atom-containing monomer in the higher-order structure of the adhesive to be formed, it is preferable that the nitrogen atom-containing monomer not contain a reactive unsaturated double bond group other than one polymerizable group used for polymerization for forming the (meth) acrylate polymer (a).

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylaziridine, aziridinylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, and the like, and among these, N- (meth) acryloylmorpholine exhibiting more excellent adhesion is preferable, and N-acryloylmorpholine is particularly preferable. One kind of them may be used alone, or two or more kinds may be used in combination.

When the (meth) acrylate polymer (a) contains a structural unit derived from a nitrogen atom-containing monomer, the content thereof 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 viewpoint of easily exhibiting desired viscoelasticity and more excellent adhesion.

The (meth) acrylate polymer (a) may optionally contain structural units derived from other monomers. As the other monomer, a monomer containing no reactive functional group is preferable in order not to hinder the action of the reactive group-containing monomer. Examples of the other monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (a) may be polymerized in solution, polymerized without solvent, or emulsified. Among them, a solution polymer obtained by a solution polymerization method is preferable. Since it is a solution polymer, a polymer of high molecular weight is easily obtained, and the above-mentioned value of Ta-Tb easily falls within a preferable range.

The polymerization system of the (meth) acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 10 to 300. Mu.m, more preferably 20 to 200. Mu.m, particularly preferably 30 to 120. Mu.m, further preferably 40 to 80. Mu.m. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range. Further, the desired cohesive force and viscoelasticity can be easily exhibited, and the appropriate adhesiveness can be easily exhibited. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by gel permeation chromatography (Gel Permeation Chromatography, GPC).

In the adhesive composition P, the (meth) acrylate polymer (a) may be used alone or in combination of two or more.

The content of the (meth) acrylate polymer (a) in the adhesive composition P of the present embodiment is preferably 60 to 99.9 mass%, more preferably 70 to 99 mass%, particularly preferably 80 to 98 mass%, and further preferably 85 to 97 mass%. When an acid free adhesive is preferable as the obtained adhesive, the content is preferably 90 to 96 mass%, and when an adhesive containing an acid component is preferable, the content is preferably 86 to 91 mass%. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

(1-2) Crosslinking agent (B)

The crosslinking agent (B) can crosslink the (meth) acrylate polymer (a) by heating the adhesive composition P, and can favorably form a crosslinked structure of a three-dimensional network structure. Thus, an adhesive having a predetermined cohesive force and viscoelasticity can be obtained, and the above-mentioned value of Ta-Tb easily falls within a preferable range. Further, excellent foaming resistance is easily obtained.

The crosslinking agent (B) may be any crosslinking agent that reacts with a reactive group (hydroxyl group or carboxyl group) of the (meth) acrylate polymer (a), and examples thereof 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. When the (meth) acrylate polymer (a) contains a structural unit derived from a hydroxyl group-containing monomer, an isocyanate-based crosslinking agent having excellent reactivity with a hydroxyl group is preferably used as the crosslinking agent (B). When the (meth) acrylate polymer (a) contains a structural unit derived from a carboxyl group-containing monomer, an epoxy-based crosslinking agent having excellent reactivity with a carboxyl group is preferably used as the crosslinking agent (B). The crosslinking agent (B) may be used alone or in combination of two or more.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound 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 the like, and biuret (biuret) bodies, isocyanurate bodies, and adducts thereof as reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylol propane-modified aromatic polyisocyanate is preferable, and trimethylol propane-modified toluene diisocyanate or trimethylol propane-modified xylylene diisocyanate is particularly preferable.

Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N '-diglycidyl aminomethyl) cyclohexane, N' -tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidyl amine. Among them, 1, 3-bis (N, N '-diglycidyl aminomethyl) cyclohexane or N, N' -tetraglycidyl-m-xylylenediamine is preferable from the viewpoint of reactivity with carboxyl groups.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.001 to 10 parts by mass, more preferably 0.005 to 5 parts by mass, and particularly preferably 0.01 to 1 part by mass, per 100 parts by mass of the (meth) acrylate polymer (a). When an acid free adhesive is used as the adhesive to be obtained, the content is preferably 0.05 to 0.8 mass%, more preferably 0.1 to 0.6 mass%, and from the viewpoint of weather resistance, preferably 0.2 to 0.4 mass%. When the adhesive contains an acid component as the adhesive to be obtained, the content is preferably 0.015 to 0.5 mass%, more preferably 0.02 to 0.1 mass%. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

(1-3) Active energy ray-curable component (C)

The adhesive composition P contains the active energy ray-curable component (C), and the obtained adhesive becomes active energy ray-curable.

The active energy ray-curable component (C) is not particularly limited as long as it is a component that is cured by irradiation with active energy rays and can obtain the above physical properties, and may be any of a monomer, an oligomer, and a polymer, or may be a mixture thereof. Among them, a polyfunctional acrylate monomer that makes the value of Ta to Tb easily fall within a preferable range is preferable.

Examples of the polyfunctional acrylate monomers include difunctional acrylates such as 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol adipic acid di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, di (acryloyloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, ethoxylated bisphenol A diacrylate, 9-bis [4- (2-acryloyloxyethoxy) phenyl ] fluorene, trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, tri (acryloyloxyethyl) isocyanurate, epsilon-caprolactone-tri- (2- (meth) acryloyloxyethyl) isocyanurate, and tetra (meth) glycerol acrylate, tetrafunctional type such as pentaerythritol tetra (meth) acrylate, pentafunctional type such as propionic acid modified dipentaerythritol penta (meth) acrylate, hexafunctional type such as dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, and the like. Among the above, from the viewpoint of the foaming resistance of the obtained adhesive, a polyfunctional acrylate monomer containing an isocyanurate structure in the molecule such as di (acryloxyethyl) isocyanurate, tri (acryloxyethyl) isocyanurate, epsilon-caprolactone-modified tri- (2- (meth) acryloxyethyl) isocyanurate is preferable, a polyfunctional acrylate monomer containing an isocyanurate structure in the molecule with three or more functions is more preferable, and epsilon-caprolactone-modified tri- (2- (meth) acryloxyethyl) isocyanurate is particularly preferable. One kind of them may be used alone, or two or more kinds may be used in combination. In addition, from the viewpoint that the obtained adhesive can easily exhibit desired viscoelasticity, the multifunctional acrylate monomer preferably has a molecular weight of less than 20000, more preferably a molecular weight of less than 10000, and particularly preferably a molecular weight of less than 5000. In addition, from the viewpoint of compatibility with the (meth) acrylate polymer (a), the molecular weight is preferably less than 1000.

The content of the active energy ray-curable component (C) in the adhesive composition P is preferably 1 to 50 parts by mass, more preferably 2 to 40 parts by mass, particularly preferably 3 to 30 parts by mass, and further preferably 4 to 20 parts by mass, per 100 parts by mass of the (meth) acrylate polymer (a). When an acid free adhesive is used as the adhesive to be obtained, the content is preferably 4.5 to 10 parts by mass, more preferably 5 to 8 parts by mass. When the adhesive contains an acid component as the adhesive to be obtained, the content is preferably 5 to 16 parts by mass, more preferably 8 to 14 parts by mass. Thus, the above-mentioned value of Ta-Tb easily falls within a preferred range.

(1-4) Photopolymerization initiator (D)

When ultraviolet rays are used as active energy rays for curing the adhesive layer, the adhesive composition P preferably contains a photopolymerization initiator (D). This can efficiently cure the active energy ray-curable component (C), and can reduce the polymerization curing time and the irradiation amount of ultraviolet rays.

As the photopolymerization initiator (D), examples thereof include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2-dimethoxy-phenylacetophenone, 2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholino-propane-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, diphenyl ketone, p-phenyldiphenyl ketone, 4' -diethylaminodiphenyl ketone dichloro-diphenyl ketone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone ], 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -phenylphosphine oxide and the like may be used alone, two or more kinds may be used in combination.

Among the above, a photopolymerization initiator of a phosphine system such as 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide or bis (2, 4, 6-trimethylbenzoyl) -phenylphosphine oxide or a mixture of diphenyl ketone and 1-hydroxycyclohexyl phenyl ketone is particularly preferable from the viewpoint of suppressing the occurrence of needle-like cracks, and a mixture of 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide or diphenyl ketone and 1-hydroxycyclohexyl phenyl ketone is particularly preferable from the viewpoint of weather resistance and foaming resistance.

The content of the photopolymerization initiator (D) in the adhesive composition P is preferably 1 to 40 parts by mass, more preferably 3 to 30 parts by mass, particularly preferably 6 to 22 parts by mass, and further preferably 8 to 14 parts by mass, per 100 parts by mass of the active energy ray-curable component (C). Thus, the obtained adhesive easily satisfies the above physical properties.

(1-5) Silane coupling agent (E)

The adhesive composition P preferably further contains a silane coupling agent (E). Thus, when the adherend is a glass member, the adhesion between the obtained adhesive and the glass member is improved. In addition, even if the adherend is a plastic plate, the adhesion of the obtained adhesive to the plastic plate is improved. This makes it easy to satisfy the above physical properties and to obtain excellent foaming resistance in the adhesive.

The silane coupling agent (E) is preferably an organosilicon compound having at least 1 alkoxysilane group in the molecule, which has good compatibility with the (meth) acrylate polymer (a) and light transmittance.

Examples of the silane coupling agent (E) include silicon compounds having a polymerizable unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyl trimethoxysilane, 3-glycidoxypropyl methyldiethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane and the like, silicon compounds having an epoxy structure such as 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, 3-mercaptopropyl dimethoxymethylsilane and the like, silicon compounds having an alkyl group such as 3-aminopropyl trimethoxysilane, N- (2-aminoethyl) -3-aminopropyl methyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyl triethoxysilane, and condensates of at least one of them with silicon compounds having an alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane and the like. One kind of them may be used alone, or two or more kinds may be used in combination.

The content of the silane coupling agent (E) in the adhesive composition P is preferably 0.01 to 10 parts by mass, more preferably 0.04 to 5 parts by mass, particularly preferably 0.08 to 1 part by mass, further preferably 0.12 to 0.5 part by mass, based on 100 parts by mass of the (meth) acrylate polymer (a), and among these, 0.15 to 0.35 part by mass is preferable. This makes it possible to easily exhibit excellent adhesion, and also makes it possible to easily exhibit excellent weather resistance and bubbling resistance.

(1-6) Various additives

The adhesive composition P may contain various additives commonly used in acrylic adhesives, for example, light stabilizers, ultraviolet absorbers, oxygen absorbers, antioxidants, tackifiers, softeners, colorants, infrared absorbers, rust inhibitors, antistatic agents, fillers, refractive index regulators, and the like, as needed.

Examples of the light stabilizer include a hindered amine light stabilizer and a hindered phenol light stabilizer, and from the viewpoint of suppressing needle-like cracks, a hindered amine light stabilizer is preferable. As a light stabilizer for the hindered amine, for example, there may be mentioned tetrakis (1, 2, 6-pentamethyl-4-piperidinyl) -1,2,3, 4-butanetetracarboxylate tetra (2, 6-tetramethyl-4-piperidinyl) 1,2,3, 4-butanetetracarboxylate, bis (1, 2, 6-pentamethyl-4-piperidinyl) sebacate tetra (2, 6-tetramethyl-4-piperidinyl) 1,2,3, 4-butanetetracarboxylate bis (1, 2, 6-pentamethyl-4-piperidinyl) sebacate. Among them, bis (1-undecyloxy-2, 6-tetramethylpiperidin-4-yl) carbonate is preferable from the viewpoints of weather resistance and foaming resistance. One kind of them may be used alone, or two or more kinds may be used in combination.

The content of the light stabilizer in the adhesive composition P is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, particularly preferably 0.1 to 5 parts by mass, further preferably 0.2 to 2 parts by mass, based on 100 parts by mass of the (meth) acrylate polymer (a), and among these, 0.3 to 1 part by mass is preferable. This makes it easy to suppress needle-like cracks and also makes it excellent in foaming resistance.

(2) Preparation of adhesive composition

The adhesive composition P can be prepared by preparing the (meth) acrylate polymer (A) and mixing the resulting (meth) acrylate polymer (A), the crosslinking agent (B) and the active energy ray-curable component (C), and optionally adding the photopolymerization initiator (D), the silane coupling agent (E), the additive, and the like.

The (meth) acrylate polymer (a) can be prepared by polymerizing a mixture of monomers constituting the polymer by a usual radical polymerization method. The polymerization of the (meth) acrylate polymer (a) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. However, the present invention is not limited thereto, and the polymerization may be performed without a solvent.

As the polymerization solvent, for example, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like can be cited, and two or more kinds may be used in combination. Examples of the polymerization initiator include azo compounds, organic peroxides, and the like, and two or more kinds may be used in combination. In the polymerization step, a chain transfer agent such as 2-mercaptoethanol may be blended to adjust the weight average molecular weight of the obtained polymer.

After the (meth) acrylate polymer (a) is obtained, the crosslinking agent (B), the active energy ray-curable component (C), and if necessary, the photopolymerization initiator (D), the silane coupling agent (E), the additive, the diluting solvent, and the like are added to the solution of the (meth) acrylate polymer (a), and the mixture is thoroughly mixed, thereby obtaining the adhesive composition P (coating solution) diluted with the solvent. In the case where a solid substance is used as any of the above-mentioned components, or in the case where precipitation occurs when the solid substance is mixed with other components in an undiluted state, the components may be dissolved or diluted in a diluting solvent in advance and then mixed with the other components.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride 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, cellosolve solvents such as ethyl cellosolve, and the like.

The concentration and viscosity of the coating solution thus prepared are not particularly limited as long as they are within a range capable of coating, and may be appropriately selected according to the situation. For example, the adhesive composition P is diluted so that the concentration thereof is 10 to 60 mass%. In addition, the addition of a diluting solvent or the like is not a necessary condition when the coating solution is obtained, and if the adhesive composition P has a viscosity that enables coating, the diluting solvent may not be added. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent of the (meth) acrylate polymer (a) directly serves as a diluting solvent.

(3) Preparation of the adhesive

The adhesive composition P is applied to a desired object and then crosslinked, whereby an adhesive (adhesive layer) can be obtained.

Crosslinking of the adhesive composition P can be performed by heat treatment. The heat treatment may be performed simultaneously with the drying treatment after the application of the adhesive composition P. The heating temperature of the heating treatment is preferably 50 to 150 ℃, particularly preferably 70 to 120 ℃. The heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

After the heat treatment, a curing period of about 1 to 2 weeks may be provided at normal temperature (e.g., 23 ℃, 50% rh) as needed. If a high curing period is required, the adhesive is formed after the curing period has elapsed, and if a curing period is not required, the adhesive is formed after the heating treatment has ended.

The crosslinked product of the (meth) acrylate polymer (a) crosslinked by the crosslinking agent (B) is formed by the above-mentioned heat treatment (and curing).

(4) Thickness of adhesive layer

The thickness of the adhesive layer (value measured according to JIS K7130) of the present embodiment is preferably 1 to 1000. Mu.m, more preferably 10 to 800. Mu.m, particularly preferably 30 to 600. Mu.m, from the viewpoint of adhesion and foaming resistance, preferably 50 to 400. Mu.m, further preferably 80 to 300. Mu.m, and particularly preferably 120 to 260. Mu.m, from the viewpoint of weather resistance.

(5) Specific structure of adhesive sheet

A specific structure as an example of the adhesive sheet of the present embodiment is shown in fig. 1.

As shown in fig. 1, the adhesive sheet 1 of one embodiment is composed of two release sheets 12a, 12b, and an adhesive layer 11 sandwiched between the two release sheets 12a, 12b so as to be in contact with the release surfaces of the two release sheets 12a, 12b, respectively. In the present specification, the release surface of the release sheet means a surface having releasability in the release sheet, and includes any one of a surface subjected to release treatment and a surface exhibiting releasability even if the release treatment is not performed.

The adhesive layer 11 is an adhesive layer in the adhesive sheet of the above embodiment.

The release sheets 12a and 12B protect the adhesive layer 11 until the adhesive sheets 1A and 1B are used, and are released when the adhesive sheets (adhesive layers) are used. In the adhesive sheet 1 of the present embodiment, one or both of the release sheets 12a and 12b are not necessary.

Examples of the release sheets 12a and 12b include polyethylene films, polypropylene films, polybutylene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene- (meth) acrylic acid copolymer films, ethylene- (meth) acrylate polymer films, polystyrene films, polycarbonate films, polyimide films, and fluororesin films. In addition, their crosslinked films may also be used. In addition, a laminated film of these may be used. In addition, from the viewpoint of the objective of perpetual development (SDGs), as a material constituting the release sheet, a material having a high biomass content, a recyclable or reusable material, or a material that has been recycled or reused may be used.

The release surfaces (particularly, the surfaces in contact with the adhesive layer 11) of the release sheets 12a and 12b are preferably subjected to a release treatment. Examples of the stripping agent used in the stripping treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based stripping agents.

The thickness of the release sheets 12a, 12b is not particularly limited, and is usually about 20 to 150 μm.

From the viewpoint of operability, among the two release sheets 12a and 12b, one release sheet is preferably a heavy release type release sheet having a large release force, and the other release sheet is preferably a light release type release sheet having a small release force.

(6) Production of adhesive sheet

As one example of the production of the adhesive sheet 1, a coating liquid containing the adhesive composition P is applied to the release surface of one release sheet 12 (or 12 b), and the adhesive composition P is thermally crosslinked by heat treatment to form a coating layer, and then the release surface of the other release sheet 12b (or 12 a) is laminated on the coating layer. If the curing period is required, the adhesive layer 11 is formed on the coating layer after the curing period, and if the curing period is not required, the adhesive layer 11 is directly formed on the coating layer. The adhesive sheet 1 was obtained through the above steps. The conditions for the heat treatment and curing are as described above.

As a method of applying the coating liquid of the adhesive composition P, for example, a bar coating method, a doctor blade coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

[ Display body ]

The display according to one embodiment of the present invention includes one display constituent member, another display constituent member, and an adhesive layer for bonding the one display constituent member and the other display constituent member to each other. The adhesive layer is formed of the adhesive layer of the adhesive sheet of the above embodiment.

At least one of the one display element constituting member and the other display element constituting member may have a step on at least a surface of the one side bonded by the adhesive layer.

The one display element constituting member and the other display element constituting member may each be a hard plate. When two hard plates are bonded to each other, the hard plates are hard and not bent, and therefore, in a state where the adhesive layer is attached to one of the hard plates, the hard plates are pressed in the vertical direction, so that the hard plates and the adhesive layer are bonded to each other, and the two hard plates are bonded to each other.

A display according to an embodiment of the present invention is described with reference to the accompanying drawings.

As shown in fig. 2, the display 2 of the present embodiment includes a first display constituent member 21 (one display constituent member), a second display constituent member 22 (the other display constituent member), and a cured adhesive layer 11' interposed therebetween and bonding the first display constituent member 21 and the second display constituent member 22 to each other.

At least one of the first display element forming member 21 and the second display element forming member 22 may have a step on a surface of the side to which the adhesive layer 11' is bonded at least after curing. In the present embodiment as shown in fig. 2, the first display element-constituting member 21 has a step due to the printed layer 3 or the like on the surface on the adhesive layer 11' side after curing.

The adhesive layer 11' after curing in the display 2 is a layer in which the adhesive layer 11 of the adhesive sheet 1 is cured by irradiation with active energy rays.

Examples of the display body 2 include a Liquid Crystal (LCD) display, a Light Emitting Diode (LED) display, an organic electroluminescence (organic EL) display, and electronic paper, and may be a touch panel. In addition, LED displays include displays using Mini LEDs (Mini LEDs), micro LED (Micro LED), and the like.

The first display element constituting member 21 is preferably a protective panel formed of a laminate including a glass plate, a plastic plate, or the like, in addition to the glass plate, the plastic plate, or the like. In this case, the printed layer 3 is generally formed in a frame shape on the adhesive layer 11' side after curing of the first display element constituting member 21.

The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, and the like. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5mm, preferably 0.2 to 2mm.

The plastic plate is not particularly limited, and examples thereof include an acrylic plate and a polycarbonate plate. The thickness of the plastic plate is not particularly limited, but is usually 0.2 to 5mm, preferably 0.4 to 3mm.

Various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, antiglare layer, etc.) may be provided on one or both surfaces of the glass plate, plastic plate, etc., or an optical member may be laminated. In addition, the transparent conductive film and the metal layer may be patterned.

The second display constituent member 22 is preferably an optical member intended to be attached to the first display constituent member 21, a display module (for example, a Liquid Crystal (LCD) module, a Light Emitting Diode (LED) module, an organic electroluminescence (organic EL) module, or the like), an optical member that is a part of the display module, or a laminate including the display module.

Examples of the optical member include a scattering preventing film, a polarizing plate (polarizing film), a polarizing plate, a retardation plate (retardation film), a viewing angle compensating film, a brightness enhancing film, a contrast enhancing film, a liquid crystal polymer film, a diffusion film, a semi-transmissive reflective film, and a transparent conductive film. The transparent conductive film is preferably an ITO-PET film having a tin-doped indium oxide (ITO) layer formed on one surface of a polyethylene terephthalate film.

The material constituting the printing layer 3 is not particularly limited, and a conventional material for printing 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, particularly preferably 3 to 20 μm. By setting the thickness of the print layer 3 to the above range, the level difference following property due to the cured adhesive layer 11' can be effectively exhibited, and the target hiding property of the print layer 3 can be sufficiently ensured. The printed layer 3 is generally formed in a frame shape on the adhesive layer 11' side after curing of the display element component.

In order to manufacture the display 2, as an example, one of the release sheets 12a of the adhesive sheet 1 may be peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 may be bonded to the surface of the first display constituent member 21 on the side where the print layer 3 is present.

Then, the other release sheet 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 member constituting member 22, thereby obtaining a display. Further, as another example, the bonding order of the first display body constitution member 21 and the second display body constitution member 22 may be changed.

After the lamination of the first display element-constituting member 21 and the adhesive layer 11 and the second display element-constituting member 22, the adhesive layer 11 is cured to become a cured adhesive layer 11' by irradiation of the adhesive layer 11 with active energy rays through the first display element-constituting member 21 and/or the second display element-constituting member 22.

The active energy ray refers to electromagnetic waves or charged particle rays having energy quanta, and specifically includes ultraviolet rays, electron rays, and the like. Among active energy rays, ultraviolet rays which are easy to handle are particularly preferable.

The irradiation of ultraviolet rays may be performed using a high-pressure mercury lamp, an H lamp manufactured by Heraeus, a xenon lamp, or the like, and the irradiation amount of ultraviolet rays is preferably 50 to 1000mW/cm ² by an illuminometer. The light quantity is preferably 50 to 10000mJ/cm ², more preferably 80 to 5000mJ/cm ², and particularly preferably 300 to 2000mJ/cm ². On the other hand, the irradiation of the electron beam may be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 krad.

In the display 2, since the adhesive constituting the adhesive layer 11 'after curing has the physical properties described above, even when irradiated with high-intensity ultraviolet rays for a long period of time (for example, 20 hours, 40 hours, etc.), the occurrence of needle-like cracks in the adhesive layer 11' after curing can be suppressed, and the weather resistance is excellent.

The embodiments described above are described for easier understanding of the present invention, and are not intended to limit the present invention. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents falling within the technical scope of the present invention.

For example, either one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and desired optical members may be laminated instead of the release sheets 12a and/or 12b. Further, the first display body constitution member 21 may not have a step. In addition, not only the first display element forming member 21 but also the second display element forming member 22 may have a step on the side of the adhesive layer 11' after curing.

In the present specification, when "X to Y" (X, Y is an arbitrary number), the meaning of "X is equal to or greater than Y and equal to or less than Y" is defined, and the meaning of "preferably greater than X" or "preferably less than Y" is also included, unless otherwise specified. In addition, when "X or more" (wherein X is an arbitrary number) is described, unless otherwise specified, the meaning of "preferably greater than X" is included, and when "Y or less" (wherein Y is an arbitrary number) is described, the meaning of "preferably less than Y" is included, unless otherwise specified.

Examples

Hereinafter, the present invention will be described more specifically by way of examples, but the scope of the present invention is not limited by these examples.

Example 1

1. Preparation of (meth) acrylate polymers

The (meth) acrylate polymer (a) was prepared by copolymerizing 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 by a solution polymerization method. When the molecular weight of the (meth) acrylate polymer (a) is measured by a method described later, the weight average molecular weight (Mw) is 50 ten thousand.

2. Preparation of adhesive composition

100 Parts by mass (solid content equivalent, hereinafter also referred to as "100 parts by mass") of the (meth) acrylic Ester polymer (A) obtained in the above-mentioned step (1), 0.15 part by mass of the isocyanate-based crosslinking agent (B1; manufactured by Mitsui Chemicals, inc. under the product name "TAKENATE D-101E"), 0.27 part by mass of epsilon-caprolactone-modified tris- (2-acryloyloxyethyl) isocyanurate (SHIN-NAKAMURA CHEMICAL CO., manufactured by LTD. Under the product name "NK Ester A-9300-1 CL") as the active energy ray-curable component (C), and 0.9 part by mass of the 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide (D1) as the photopolymerization initiator were mixed, sufficiently stirred, and diluted with methyl ethyl ketone, thereby obtaining a coating solution of the adhesive composition.

Here, table 1 shows the respective components (solid content conversion values) of the adhesive composition when the (meth) acrylate polymer (a) is set to 100 parts by mass (solid content conversion values). Details of abbreviations and the like described in table 1 are as follows.

[ (Meth) acrylate Polymer (A) ]

2EHA 2-ethylhexyl acrylate

BA n-butyl acrylate

MMA methyl methacrylate

IBXA isobornyl acrylate

ACMO N-acryloylmorpholine

HEA 2-hydroxyethyl acrylate

AA acrylic acid

[ Cross-linking agent (B) ]

B1 isocyanate-based crosslinking agent (Mitsui Chemicals, inc. manufactured by Inc. Product name "TAKENATE D-101E")

B2:1, 3-bis (N, N' -diglycidyl aminomethyl) cyclohexane (epoxy-based crosslinking agent)

[ Photopolymerization initiator (D) ]

D1:2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide

D2 bis (2, 4, 6-trimethylbenzoyl) -phenylphosphine oxide

D3 mixture of diphenylketone and 1-hydroxycyclohexylphenyl ketone (mass ratio 50:50)

D4:1-hydroxycyclohexyl phenyl ketone

D5 mixture of 2-oxo-2-phenylacetic acid-2- (2-oxo-2-phenylacetyloxyethoxy) ethyl ester and 2-oxo-2-phenylacetic acid-2- (2-hydroxyethoxy) ethyl ester (manufactured by IGM RESINS Co., ltd., product name "OMNIRAD 754")

[ Light stabilizer ]

F1 tetrakis (1, 2, 6-pentamethyl-4-piperidinyl) -1,2,3, 4-butanetetracarboxylate

F2 bis (1-undecoxy-2, 6-tetramethylpiperidin-4-yl) carbonate

3. Production of adhesive sheet

The coating solution of the adhesive composition obtained in the step 2 was applied to the release treated surface of the heavy release type release sheet R1, which was subjected to release treatment with a silicone release agent, on one surface of polyethylene terephthalate by a coater. Then, heat treatment was performed at 90 ℃ for 1 minute to form a coating layer. Then, the coating layer on the release sheet R1 obtained above was bonded to the release sheet R2 having a light release type, which was obtained by subjecting one surface of the polyethylene terephthalate film to a release treatment with a silicone release agent, so that the release treated surface of the release sheet R2 was in contact with the coating layer, and cured under conditions of 23 ℃ and 50% rh for 7 days, to thereby produce an adhesive sheet having an adhesive layer with a thickness of 50 μm, that is, an adhesive sheet having a structure of release sheet R1/adhesive layer (thickness: 50 μm)/release sheet R2.

The thickness of the adhesive layer was measured by a constant pressure thickness measuring instrument (product name "PG-02", manufactured by Teclock Co., ltd.) according to JIS K7130. Further, regarding the peel force of the release sheets R1 and R2 in the obtained adhesive sheet, it was confirmed that the peel force of the release sheet R1 was larger than the peel force of the release sheet R2.

Examples 2 to 7 and comparative examples 1 to 3

An adhesive sheet was produced in the same manner as in example 1, except that the types and weight average molecular weights (Mw) of the monomers constituting the (meth) acrylate polymer (a), the types and amounts of the crosslinking agent (B), the amounts of the active energy ray-curable component (C), and the types and amounts of the photopolymerization initiator (D) were changed as shown in table 1. In example 3 and example 4, a light stabilizer (F1/F2) was further added in the amounts shown in table 1.

Here, the weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured using Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< Measurement conditions >

Measurement device manufactured by TOSOH CORPORATION, HLC-8320

GPC column (passing through the column in the following order) TOSOH CORPORATION

TSK gel super H-H

TSK gel super HM-H

TSK gel super H2000

Determination of solvent tetrahydrofuran

Measurement temperature of 40 DEG C

[ Test example 1] (determination of gel fraction)

The adhesive layers of the adhesive sheets produced in examples and comparative examples were laminated in layers to produce adhesive layers having a thickness of 250. Mu.m. The adhesive layer (thickness: 250 μm) was cut into a size of 70 mm. Times.150 mm, and the adhesive layer was wrapped in a polyester net (mesh size 200), and the mass thereof was measured by a precision balance, and the individual mass of the net was subtracted, whereby the individual mass of the adhesive was calculated. The mass at this time was set to M1.

Thereafter, the adhesive coated on the polyester net was immersed in ethyl acetate at room temperature (23 ℃) for 24 hours. Thereafter, the adhesive was removed, air-dried at 23 ℃ in 50% rh for 24 hours, and then placed in an 80 ℃ oven for drying for 12 hours. After drying, the mass was weighed with a precision balance, and the individual mass of the above-mentioned net was subtracted, thereby calculating the individual mass of the adhesive. The mass at this time was set to M2. Gel fraction (%; before UV) is represented by (M2/M1). Times.100. The results are shown in table 2.

The adhesive layers of the adhesive sheets produced in examples and comparative examples were laminated to each other to produce adhesive layers having a thickness of 250. Mu.m. The adhesive layer (thickness: 250 μm) was irradiated with active energy rays (ultraviolet rays; UV) to cure the adhesive layer. The gel fraction (%; after UV) of the adhesive agent layer after the active energy ray curing 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.

< Conditions for irradiation with active energy rays >

Using high-pressure mercury lamps

Illuminance of 200mW/cm ², light quantity of 1000mJ/cm ²

UV illuminance A light Meter was manufactured by EYE GRAPHICS company "UVPF-A1"

The adhesive layers of the adhesive sheets produced in examples and comparative examples were laminated to each other to produce adhesive layers having a thickness of 250. Mu.m. Two soda lime glass plates (NIPPON SHEET GLASS CO., LTD. Manufactured by 1.1mm thick by 70mm long by 150mm wide) were bonded using the adhesive layer (thickness: 250 μm), and a laminate (soda lime glass plate/adhesive layer (thickness: 250 μm)/soda lime glass plate) was manufactured. The laminate is irradiated with active energy rays (ultraviolet rays; UV) under the above active energy ray irradiation conditions, and the adhesive layer is cured. Next, the laminate having the adhesive layer cured by the active energy ray was irradiated with ultraviolet rays (S-UV irradiation) under the following conditions. Then, the adhesive layer was separated from the two soda lime glass plates in the laminate after S-UV irradiation. The gel fraction (%; after S-UV) of the adhesive of the separated adhesive layer was measured in the same manner as described above. The results are shown in table 2.

< Conditions for ultraviolet irradiation >

Device Eye Super UV Tester SUV-W151 (IWASAKI ELECTRIC CO., LTD. Manufacturing)

Ultraviolet lamp (ME 06-L31 WX/SUV) (IWASAKI ELECTRIC CO., LTD. Manufactured by Kogyo Co., ltd.)

Water-cooled cannula WJ50-SUV-4 (IWASAKI ELECTRIC CO., LTD. Manufacturing)

Illuminance of 100mW/cm ²

Irradiation time of 120 hours

Light quantity 43.2kJ/cm ²

Temperature of 63 DEG C

Humidity 70% RH

Temperature and humidity control, closed circulation mode

Test example 2 (measurement of average peak molecular weight of Sol component)

The adhesive layers of the adhesive sheets produced in examples and comparative examples were laminated in layers to produce adhesive layers having a thickness of 250. Mu.m. The adhesive layer was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured. The adhesive of the adhesive layer after the active energy ray curing was concentrated using an evaporator in ethyl acetate (after dipping and removal of the adhesive) obtained in the same manner as in test example 1, to thereby obtain a sol component. Then, the sol component was diluted with tetrahydrofuran to a 0.3 mass% solution, filtered through a 0.45 μm filter, and then the average peak molecular weight (Mp; before S-UV) of the sol component was measured by GPC measurement. The measurement conditions for GPC measurement are as described above. The results are shown in table 2.

The adhesive sheets produced in examples and comparative examples were used to produce a laminate similar to that of test example 1. The laminate was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured. Next, the laminate having the adhesive layer cured with active energy rays was irradiated with ultraviolet rays (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 in the laminate after S-UV irradiation. The adhesive of the separated adhesive layer was subjected to the same procedure as described above, and the average peak molecular weight (Mp; after S-UV) of the sol component was measured. The results are shown in Table 2.

Test example 3 (measurement of dynamic viscoelasticity)

The adhesive layers of the adhesive sheets produced in examples and comparative examples were laminated in layers to produce adhesive layers having a thickness of 250. Mu.m. The adhesive layer was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured. A cylinder (height: 0.25 mm) having a diameter of 8mm was punched out of the adhesive layer after the active energy ray curing, and was used as a sample.

For the above samples, dynamic viscoelasticity was measured by a torsional shear method using a viscoelasticity measuring device (product name "MCR302" manufactured by Anton Paar corporation) according to JIS K7244-1, and storage modulus G ' (-15) at-15 ℃ (MPa; before S-UV), storage modulus G ' (23) at 23 ℃ (MPa; before S-UV), and storage modulus G ' (100) at 100 ℃ (MPa; before S-UV) were derived. The peak temperature (°C) of the loss tangent tan. Delta. (S-UV front: tb) was also derived. The results are shown in table 2.

Measuring frequency 1Hz

The measurement temperature range is-20 ℃ to 140 ℃

The temperature rise rate is 4 ℃ per minute

The adhesive sheets produced in examples and comparative examples were used to produce a laminate similar to that of test example 1. The laminate was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1 to cure the adhesive layer. Next, the laminate having the adhesive layer cured with active energy rays was irradiated with ultraviolet rays (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 in the laminate after S-UV irradiation. The dynamic viscoelasticity was measured in the same manner as described above for the adhesive layer after separation, and the storage modulus G ' (-15) at-15 ℃ (MPa; after S-UV), the storage modulus G ' (23) at 23 ℃ (MPa; after S-UV), and the storage modulus G ' (100) at 100 ℃ (MPa; after S-UV) were derived. The peak temperature (°C) of the loss tangent tan. Delta. (S-UV, ta) was also derived. The results are shown in table 2.

Further, the value of Ta minus Tb (Ta-Tb) obtained as described above was calculated. The results are shown in table 2.

[ Test example 4] (measurement of adhesion)

The release sheet R2 was peeled off from the adhesive sheets produced in examples and comparative examples, and the exposed adhesive layer was bonded to an easy-to-adhere layer on one of the surfaces of a polyethylene terephthalate (PET) film (toyobaco., ltd. Manufactured under the product name "COSMOSHINE A4360", thickness: 100 μm) having easy-to-adhere layers on both surfaces, to obtain a laminate of release sheet R1/adhesive layer/PET film. The laminate was cut into a sheet having a width of 25mm and a length of 100mm, and used as a sample.

The release sheet R1 was peeled off from the above sample in an atmosphere of 23 ℃ and 50% rh, and the exposed adhesive layer was attached to soda lime glass (NIPPON SHEET GLASS co., ltd. Manufactured), and pressure was applied at 50 ℃ for 20 minutes at 0.5MPa in an autoclave manufactured by KURIHARA SEISAKUSHO co., ltd. Then, the adhesive layer was cured by irradiation with active energy rays (ultraviolet rays; UV) through the soda lime glass under the same active energy ray irradiation conditions as in test example 1.

Then, the resultant was left to stand at 23℃and 50% RH for 24 hours, and then the adhesion was measured using a tensile tester (ORIENTEC Co., ltd., product name "TENSILON") at a peeling speed of 300mm/min and a peeling angle of 180 ℃. The conditions not described herein were measured according to JIS Z0237:2009. The results are shown in table 2.

Test example 5 (measurement of total light transmittance)

The adhesive layers of the adhesive sheets produced in examples and comparative examples were laminated in layers to produce adhesive layers having a thickness of 250. Mu.m. Using the adhesive layer (thickness: 250 μm), a laminate was produced in the same manner as in test example 1. The adhesive layer was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured to obtain a measurement sample. After background measurement with soda lime glass, the total light transmittance (%; before S-UV) was measured for the above-mentioned measurement sample using a haze meter (Nippon Denshoku Industries Co., ltd., product name "NDH-5000") according to JIS K7361-1:1997. The results are shown in table 2. In addition, when the total light transmittance of the adhesive layer before active energy ray curing was measured, the same measurement result was also obtained.

[ Test example 6] (measurement of haze value)

A measurement sample was prepared in the same manner as in test example 5. For this measurement sample, after background measurement was performed with glass, a haze value (%; before S-UV) was measured using a haze meter (Nippon Denshoku Industries Co., ltd., product name "NDH-5000") according to JIS K7136:2000. The results are shown in table 2. In addition, when the haze value of the adhesive layer before active energy ray curing was measured, the same measurement result was also obtained.

Test example 7 (measurement of Laab)

Using the adhesive sheets produced in examples and comparative examples, the same laminate as in test example 1 was produced. The laminate was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured. For the adhesive layer after the irradiation with active energy rays, chromaticity b (chromaticity b 1) specified by CIE1976l×a×b×color system was measured using a photometric spectrocolorimeter (Nippon Denshoku Industries co., ltd., product name "SQ 2000"). The results are shown in table 2.

The adhesive sheets produced in examples and comparative examples were used to produce a laminate similar to that of test example 1. The laminate was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured. Next, the laminate having the adhesive layer cured with active energy rays was irradiated with ultraviolet rays (S-UV irradiation) under the same ultraviolet irradiation conditions as in test example 1. Then, chromaticity b (chromaticity b×2) was measured for the adhesive layer in the laminate after S-UV irradiation in the same manner as described above. The results are shown in table 2.

Further, the absolute value of the ratio (b×2/b×1) of the chromaticity b×2 to the chromaticity b×1 obtained in the above is calculated. The results are shown in Table 2.

Test example 8 (evaluation of weather resistance)

Using the adhesive sheets produced in examples and comparative examples, the same laminate as in test example 1 was produced. The laminate was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in test example 1, and the adhesive layer was cured. Next, the adhesive layer cured with active energy rays was irradiated with ultraviolet rays under the same ultraviolet irradiation conditions as in test example 1 except that the ultraviolet irradiation time was set to 20 hours (light amount: 7.2kJ/cm ²) and 40 hours (light amount: 14.4kJ/cm ²). The adhesive layer after that was visually confirmed, and weather resistance was evaluated based on the following criteria. The results are shown in table 2.

No needle-like cracks and no bubbles, floating and peeling were generated.

No needle-like cracks were generated, but some bubbles were generated.

Needle-shaped cracks were generated.

Test example 9 (evaluation of foaming resistance)

The release sheet R2 was peeled from the adhesive sheets produced in examples and comparative examples, and the exposed adhesive layer was attached to a PC board-side surface of a plastic sheet (MITSUBISHI GAS CHEMICAL compass y, inc. Manufactured by mitsubon. Sheet MR58U, thickness: 0.7 mm) laminated with polymethyl methacrylate on a Polycarbonate (PC) board. Then, the release sheet R1 was peeled from the adhesive layer to expose the adhesive layer, and a transparent conductive film (OIKE & co., ltd.) was laminated so that the ITO layer side of the laminate of the PET film and the ITO layer (ITO-PET film) was in contact with the adhesive layer. Thereafter, autoclave treatment was performed at 50℃under 0.5MPa for 20 minutes.

The adhesive layer of the obtained laminate was irradiated with active energy rays (ultraviolet rays; UV) through the transparent conductive film under the same conditions as in test example 1, and the adhesive layer was cured. Thereafter, the sample was left under normal pressure, 23℃and 50% RH for 24 hours.

The obtained sample was then stored under high temperature and high humidity conditions of 85 ℃ and 85% rh for 72 hours. Then, the state of the interface between the adhesive layer and the adherend (plastic plate) was visually confirmed, and the bubbling resistance was evaluated based on the following criteria. The results are shown in table 2.

No bubbles, floating, peeling, etc. were generated at all.

Air bubbles smaller than 1mm in diameter were produced, but no lifting/peeling was produced.

Bubble generation, floating, peeling, and the like are all made.

TABLE 1

TABLE 2

As can be seen from table 2, the adhesive sheet produced in examples was excellent in weather resistance while suppressing the occurrence of needle-like cracks even when irradiated with high-intensity ultraviolet rays for a long period of time (20 hours/40 hours).

Industrial applicability

The adhesive sheet of the present invention can be suitably used for bonding a display constituent member such as a protective panel to a desired display constituent member in the production of a display.

Description of the reference numerals

1 Adhesive sheet, 11 adhesive layer, 12a release sheet, 12b release sheet, 2 display, 11' cured adhesive layer, 21 first display constituent member, 22 first display constituent member, and 3 print layer.

Claims

1. An adhesive sheet having an adhesive layer for bonding two display body components together, characterized in that,

The adhesive constituting the adhesive layer is an adhesive that can be cured by active energy rays.

When the peak temperature of the loss tangent tanδ of the adhesive layer constituting the adhesive layer after curing by active energy rays is set as Tb (°C), and

When the adhesive layer cured by active energy rays is irradiated with ultraviolet light at an irradiance of 100 mW/ ^cm² for 120 hours, and the peak temperature of the loss tangent tanδ of the adhesive constituting the adhesive layer is set as Ta (°C),

The value obtained by subtracting Tb from Ta is greater than 3.

2. The adhesive sheet according to claim 1, wherein the gel fraction of the adhesive constituting the adhesive layer is 20% or more and 85% or less.

3. The adhesive sheet according to claim 1, characterized in that the gel fraction of the adhesive constituting the adhesive layer after curing by active energy rays is 30% or more and 95% or less.

4. The adhesive sheet according to claim 1, characterized in that, after the adhesive layer cured by active energy rays is irradiated with ultraviolet light at an irradiance of 100 mW/ ^cm² for 120 hours, the gel fraction of the adhesive constituting the adhesive layer is 40% or more and 99% or less.

5. The adhesive sheet according to claim 1, characterized in that the average peak molecular weight of the sol component of the adhesive constituting the adhesive layer after active energy ray curing is more than 10,000 and less than 250,000.

6. The adhesive sheet according to claim 1, characterized in that, after the adhesive layer cured by active energy rays is irradiated with ultraviolet light at an irradiance of 100 mW/ ^cm² for 120 hours, the average peak molecular weight of the sol component of the adhesive constituting the adhesive layer is more than 10,000 and less than 200,000.

7. The adhesive sheet according to claim 1, characterized in that the adhesive forming the adhesive layer after being cured by active energy rays has a storage modulus G’ of 0.01 MPa or more and 2 MPa or less at 23°C.

8. The adhesive sheet according to claim 1, characterized in that, after the adhesive layer cured by active energy rays is irradiated with ultraviolet light at an irradiance of 100 mW/ ^cm² for 120 hours, the storage modulus G' of the adhesive constituting the adhesive layer at 23°C is 0.01 MPa or more and 2 MPa or less.

9. The adhesive sheet according to claim 1, characterized in that the adhesive forming the adhesive layer after being cured by active energy rays has a storage modulus G’ of 0.01 MPa or more and 100 MPa or less at -15°C.

10. The adhesive sheet according to claim 1, characterized in that, after the adhesive layer cured by active energy rays is irradiated with ultraviolet light at an irradiance of 100 mW/ ^cm² for 120 hours, the storage modulus G' of the adhesive constituting the adhesive layer at -15°C is 0.1 MPa or more and 1000 MPa or less.

11. The adhesive sheet according to claim 1, wherein the adhesive forming the adhesive layer after being cured by active energy rays has a storage modulus G’ of 0.0001 MPa or more and 1 MPa or less at 100°C.

12. The adhesive sheet according to claim 1, characterized in that, after the adhesive layer cured by active energy rays is irradiated with ultraviolet light at an irradiance of 100 mW/ ^cm² for 120 hours, the storage modulus G' of the adhesive constituting the adhesive layer at 100°C is 0.0001 MPa or more and 1 MPa or less.

13. The adhesive sheet according to claim 1, wherein the adhesive is an acrylic adhesive.

14. The adhesive sheet according to claim 1, characterized in that,

The adhesive sheet has two release tabs.

The adhesive layer is held by the release tabs in such a way that it contacts the release surfaces of the two release tabs.

15. A display body comprising a display body constituent member, another display body constituent member, and an adhesive layer for bonding the one display body constituent member and the other display body constituent member together, characterized in that the adhesive layer is formed from the adhesive layer of the adhesive sheet according to any one of claims 1 to 14.

16. The display body according to claim 15, wherein both the one display body component and the other display body component are rigid plates.