Adhesive sheet and display body

Abstract

The present application provides an adhesive sheet 1 which is an adhesive sheet 1 having an adhesive layer 11 for adhering two display body constituting members to each other, wherein the adhesive constituting the adhesive layer 11 is an active energy ray-curable adhesive, when a peak temperature of a loss tangent tan δ of the adhesive constituting the adhesive layer 11' after curing by active energy rays is set as Tb (°C), and a peak temperature of a loss tangent tan δ of the adhesive constituting the adhesive layer 11' after irradiation of the adhesive layer 11' after curing by active energy rays with ultraviolet rays of an illuminance of 100 mW / cm 2 2 for 120 hours is set as Ta (°C), the value obtained by subtracting Tb from Ta is greater than 3. The adhesive sheet 1 can suppress the generation of needle-shaped cracks and has excellent weather resistance.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet for bonding two display components together, and a display obtained by using an adhesive layer of the adhesive sheet. Background Technology

[0002] In recent years, various mobile electronic devices such as mobile phones, smartphones, and tablets have adopted displays (monitors) with display modules such as liquid crystal components, light-emitting diodes (LED components), and organic electroluminescent (organic EL) components.

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

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

[0005] However, if the gaps, i.e. air layers, mentioned above exist, the light reflection loss caused by the difference in refractive index between the protective panel and the air layer, as well as the difference in refractive index between the air layer and the display module, will be significant, resulting in a deterioration in the display's image quality.

[0006] Therefore, a solution has been proposed to improve the image quality of the display by using an adhesive layer to fill the gap between the protective panel and the display module. For example, Patent Document 1 discloses an adhesive layer that, as an adhesive layer for filling the gap between the protective panel and the display module, has a shear storage modulus (G') of 1.0 × 10⁻⁶ at 25°C and 1 Hz. 5 The pH value is below 40% and the gel fraction is above 40%.

[0007] Existing technical documents

[0008] Patent documents

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

[0010] (a) Technical problems to be solved

[0011] Sometimes, when a display made using the adhesive layer described above is exposed to high-intensity ultraviolet light for an extended period, needle-like cracks may appear in the adhesive layer. This problem is particularly prone to occur during accelerated weathering tests involving prolonged exposure to high-intensity ultraviolet light.

[0012] The present invention was made in view of the following actual situation, and its object is to provide an adhesive sheet and display body that can suppress the generation of needle-like cracks and has excellent weather resistance.

[0013] (II) Technical Solution

[0014] To achieve the above objectives, firstly, the present invention provides an adhesive sheet having an adhesive layer for bonding two display components together. The adhesive layer is characterized in that the adhesive is an active energy radiation-curable adhesive. The peak temperature of the loss tangent tanδ of the adhesive layer after active energy radiation curing is set to Tb (°C), and the active energy radiation-cured adhesive layer is irradiated with an irradiation of 100 mW / cm². 2 When the peak temperature of the loss tangent tanδ of the adhesive that constitutes the adhesive layer after 120 hours of ultraviolet light exposure is set as Ta (°C), the value obtained by subtracting Tb from Ta is greater than 3 (Invention 1).

[0015] In the adhesive layer of the adhesive sheet of the above-mentioned invention (Invention 1), even after prolonged exposure to high-intensity ultraviolet light (e.g., 20 hours, 40 hours, etc.), damage to cross-linking points, such as the initiation point of needle-like cracks, can be suppressed, thus exhibiting good adhesion to the components constituting the display body. As a result, the adhesive sheet can suppress the generation of needle-like cracks and has excellent weather resistance.

[0016] In the above invention (Invention 1), it is preferable that the gel fraction of the adhesive constituting the adhesive layer is 20% or more and 85% or less (Invention 2).

[0017] In the above inventions (Inventions 1 and 2), it is preferable 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 (Invention 3).

[0018] In the above inventions (Inventions 1-3), it is preferable to irradiate the adhesive layer after it has been cured by active energy rays with an irradiation intensity of 100 mW / cm². 2 After 120 hours of exposure to ultraviolet light, the gel content of the adhesive constituting the adhesive layer is 40% or more and 99% or less (Invention 4).

[0019] In the above inventions (Inventions 1 to 4), it is preferable that the average peak molecular weight of the sol component of the adhesive constituting the adhesive layer after curing by active energy rays is 10,000 or more and 250,000 or less (Invention 5).

[0020] In the above inventions (Inventions 1-5), it is preferable to irradiate the adhesive layer after it has been cured by active energy rays with an irradiation intensity of 100 mW / cm². 2After 120 hours of exposure to ultraviolet light, the average peak molecular weight of the sol component of the adhesive that constitutes the adhesive layer is above 10,000 and below 200,000 (Invention 6).

[0021] In the above inventions (Inventions 1 to 6), it is preferable 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 (Invention 7).

[0022] In the above inventions (Inventions 1-7), it is preferable to irradiate the adhesive layer after it has been cured by active energy rays with an irradiation intensity of 100 mW / cm². 2 After 120 hours of exposure to ultraviolet light, 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 (Invention 8).

[0023] In the above inventions (Inventions 1 to 8), it is preferable that the adhesive constituting the adhesive layer after curing by active energy rays has a storage modulus G' of 0.01 MPa or more and 100 MPa or less at -15°C (Invention 9).

[0024] In the above inventions (Inventions 1-9), it is preferable to irradiate the adhesive layer after curing with active energy rays with an irradiation intensity of 100 mW / cm². 2 After 120 hours of exposure to ultraviolet light, 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 (Invention 10).

[0025] In the above inventions (Inventions 1 to 10), it is preferable that the adhesive forming the adhesive layer after active energy ray curing has a storage modulus G' of 0.0001 MPa or more and 1 MPa or less at 100°C (Invention 11).

[0026] In the above inventions (Inventions 1-11), it is preferable to irradiate the adhesive layer after it has been cured by active energy rays with an irradiation intensity of 100 mW / cm². 2 After 120 hours of exposure to ultraviolet light, the adhesive constituting the adhesive layer has a storage modulus G' of 0.0001 MPa or more and 1 MPa or less at 100°C (Invention 12).

[0027] In the above inventions (Inventions 1 to 12), the adhesive is preferably an acrylic adhesive (Invention 13).

[0028] In the above inventions (Inventions 1 to 13), it is preferable that the adhesive sheet has two release tabs, and the adhesive layer is held by the release tabs in such a way that it contacts the release surfaces of the two release tabs (Invention 14).

[0029] Second, the present invention provides a display body comprising a display body component, another display body component, and an adhesive layer for bonding the one display body component and the other display body component together, characterized in that the adhesive layer is formed from the adhesive layer of the adhesive sheet (Invention 1-14) (Invention 15).

[0030] In the invention (Invention 15), both the one display body component and the other display body component may be made of rigid plates (Invention 16).

[0031] (III) Beneficial Effects

[0032] The adhesive sheet and display body of the present invention can suppress the generation of needle-like cracks and have excellent weather resistance. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view of an adhesive sheet according to one embodiment of the present invention.

[0034] Figure 2 This is a cross-sectional view of a display body according to one embodiment of the present invention. Detailed Implementation

[0035] The embodiments of the present invention will be described below.

[0036] [Adhesive sheet]

[0037] The adhesive sheet of this embodiment has an adhesive layer that bonds the two display components together. The specific structure of the adhesive sheet and the components of the display will be described in detail later.

[0038] In this embodiment, the adhesive constituting the adhesive layer in the adhesive sheet is an adhesive that is cured by active energy radiation. In the adhesive sheet of this embodiment, when the peak temperature of the loss tangent tanδ of the adhesive constituting the adhesive layer after active energy radiation curing is set as Tb (°C), the adhesive layer after active energy radiation curing is irradiated (hereinafter sometimes referred to as "S-UV irradiation") with an irradiation of 100 mW / cm². 2 When the peak temperature of the loss tangent tanδ of the adhesive constituting the adhesive layer after 120 hours of ultraviolet light exposure is set as Ta (°C), it is preferable that the value obtained by subtracting Tb from Ta is greater than 3 (Ta-Tb>3). Furthermore, the method for measuring the loss tangent tanδ is shown in the experimental examples described later.

[0039] Here, the term "adhesive layer cured by active energy rays" in this specification refers to an adhesive layer that has been completely cured by irradiation with active energy rays. Specifically, it refers to an adhesive layer that, when further irradiated with active energy rays at the same intensity (light intensity) as during active energy ray curing, exhibits an increase in gel fraction of 10% or less, particularly an increase of 5% or less. Furthermore, in this specification, "relative humidity α%" is sometimes expressed as "α%RH" (RH; Relative humidity).

[0040] It is generally believed that when exposed to high-intensity ultraviolet light for a prolonged period of time, as described above, the cross-linking structure of the adhesive changes, resulting in needle-like cracks. In contrast, in the adhesive of this invention, by satisfying the above-described relationship, the peak temperature of the loss tangent tanδ after S-UV irradiation shifts towards a higher temperature, and the point at which the adhesive's viscoelasticity increases shifts from a lower temperature to a normal temperature. As a result, even with prolonged (e.g., 20 hours, 40 hours, etc.) irradiation with high-intensity ultraviolet light, damage to cross-linking points, such as the initiation point of needle-like cracks, can be suppressed, resulting in excellent adhesion to the components of the display body. Thus, the adhesive sheet of this embodiment can suppress the generation of needle-like cracks and exhibits excellent weather resistance.

[0041] From the perspective of suppressing the formation of the aforementioned needle-like cracks, the value of Ta-Tb is more preferably 4 or more, more preferably 5 or more, particularly preferably 6, further preferably 7, and preferably 8 or more. On the other hand, from the perspective of moderately shifting the point of increasing the viscosity of the adhesive's viscoelasticity towards the room temperature side, the upper limit value of Ta-Tb is preferably 30 or less, more preferably 24 or less, particularly preferably 18 or less, further preferably 15 or less, and preferably 12 or less.

[0042] The peak temperature Ta of the loss tangent tanδ of the adhesive layer cured by active energy rays and then subjected to S-UV irradiation (hereinafter sometimes simply referred to as "S-UV irradiated adhesive") is preferably -30℃ to 30℃, more preferably -20℃ to 20℃, particularly preferably -10℃ to 10℃, further preferably -5℃ to 5℃, and most preferably -4℃ to 2℃. Therefore, the above Ta-Tb values ​​readily fall within the preferred range.

[0043] The peak temperature Tb of the loss tangent tanδ of the adhesive after curing with active energy rays (before S-UV irradiation) is preferably -30℃ to 30℃, more preferably -25℃ to 20℃, particularly preferably -20℃ to 10℃, and even more preferably -15℃ to 5℃, wherein it is preferably -10℃ to 0℃. Therefore, the Ta-Tb value easily falls within the preferred range, and good adhesion is easily obtained after curing with active energy rays.

[0044] In this embodiment, the gel fraction of the adhesive constituting the adhesive layer in the adhesive sheet is preferably 20-85%, more preferably 30-80%, particularly preferably 40-75%, and even more preferably 46-70%, with a preferred value of 52-67%. This allows for good adhesion when attaching to the substrate. Furthermore, the method for determining the gel fraction in this specification is shown in the test examples described later.

[0045] In this embodiment, the gel fraction of the adhesive forming the adhesive layer after curing by active energy rays in the adhesive sheet is preferably 30-95%, more preferably 40-92%, particularly preferably 50-90%, and even more preferably 60-88%, wherein 70-86% is preferred. This facilitates good adhesion after the display components are bonded together.

[0046] The gel fraction of the adhesive after S-UV irradiation is preferably 40-99%, more preferably 55-98%, particularly preferably 70-97%, further preferably 78-96%, and most preferably 84-95%. Therefore, the Ta-Tb values ​​mentioned above easily fall within the preferred range.

[0047] In this embodiment, the average peak molecular weight of the sol component of the adhesive forming the adhesive layer after curing by active energy rays in the adhesive sheet is preferably 10,000 to 250,000, more preferably 30,000 to 200,000, particularly preferably 50,000 to 150,000, and even more preferably 60,000 to 100,000, with a preferred value of 62,000 to 75,000. This facilitates good adhesion of the display components after bonding. Furthermore, the average peak molecular weight of the sol component in this specification is a value converted from standard polystyrene, determined by gel permeation chromatography (GPC). The specific determination method is shown in the experimental examples described later.

[0048] The average peak molecular weight of the sol component of the adhesive after S-UV irradiation is preferably 10,000 to 200,000, more preferably 30,000 to 160,000, particularly preferably 40,000 to 120,000, and even more preferably 50,000 to 80,000, with a preferred value of 55,000 to 70,000. Therefore, the Ta-Tb values ​​mentioned above easily fall within the preferred range.

[0049] In this embodiment, the storage modulus G' of the adhesive layer constituting the adhesive sheet after curing by active energy rays is preferably 0.01–2 MPa, more preferably 0.04–1 MPa, more preferably 0.08–0.8 MPa, particularly preferably 0.12–0.6 MPa, and even more preferably 0.15–0.5 MPa, with a preferred value of 0.18–0.4 MPa. This facilitates good adhesion of the display components after bonding. Furthermore, the method for measuring the storage modulus G' in this specification is shown in the experimental examples described later.

[0050] The storage modulus G' of the adhesive after S-UV irradiation at 23°C is preferably 0.01–2 MPa, more preferably 0.05–1.5 MPa, more preferably 0.1–1 MPa, particularly preferably 0.15–0.8 MPa, and even more preferably 0.18–0.6 MPa. Therefore, the above-mentioned Ta-Tb values ​​readily fall within the preferred range.

[0051] In this embodiment, the storage modulus G' of the adhesive layer constituting the adhesive sheet after curing by active energy rays is preferably 0.01 to 100 MPa, more preferably 0.1 to 80 MPa, more preferably 1 to 60 MPa, particularly preferably 1 to 40 MPa, and even more preferably 5 to 30 MPa, wherein, most preferably 10 to 30 MPa. This facilitates good adhesion of the display components at low temperatures after bonding.

[0052] The storage modulus G' of the adhesive after S-UV irradiation at -15°C is preferably 0.1–1000 MPa, more preferably 1–500 MPa, more preferably 5–200 MPa, particularly preferably 10–100 MPa, and even more preferably 18–50 MPa. Therefore, the above-mentioned Ta-Tb values ​​easily fall within the preferred range.

[0053] In this embodiment, the storage elastic modulus G' of the adhesive layer constituting the adhesive sheet after curing by active energy rays is preferably 0.0001–1 MPa, more preferably 0.001–0.7 MPa, more preferably 0.005–0.4 MPa, particularly preferably 0.01–0.2 MPa, and even more preferably 0.02–0.1 MPa, wherein preferably 0.03–0.07 MPa. This facilitates good adhesion of the display components at high temperatures after bonding.

[0054] The storage modulus G' of the adhesive after S-UV irradiation at 100°C is preferably 0.0001–1 MPa, more preferably 0.0005–0.7 MPa, more preferably 0.001–0.4 MPa, particularly preferably 0.005–0.2 MPa, and even more preferably 0.01–0.1 MPa, wherein, most preferably 0.02–0.09 MPa. Therefore, the above Ta-Tb values ​​readily fall within the preferred range.

[0055] In this embodiment, the adhesion strength of the adhesive layer (before S-UV irradiation) cured by active energy rays to soda-lime glass is preferably 1–100 N / 25 mm, more preferably 5–75 N / 25 mm, particularly preferably 10–50 N / 25 mm, and even more preferably 15–35 N / 25 mm. This readily results in excellent weather resistance and blister resistance. The aforementioned adhesion strength basically refers to the adhesion strength measured by the 180-degree peel test according to JIS Z0237:2009. Specific test methods are shown in the test examples described later.

[0056] The total light transmittance of the adhesive layer (before S-UV irradiation) after curing with active energy rays in this embodiment is preferably 80% or more, more preferably 90% or more, particularly preferably 95%, and even more preferably 99% or more. This results in very high transparency, making it suitable for optical applications (display bodies). The upper limit of the above-mentioned total light transmittance is not particularly limited and can be 100%, as the measurement results may allow for values ​​slightly exceeding 100%. Furthermore, the total light transmittance of the adhesive layer before curing with active energy rays and the adhesive layer after S-UV irradiation is preferably within the same range as that of the adhesive layer before S-UV irradiation. The total light transmittance in this specification is a value measured according to JIS K7361-1:1997, and the specific test method is shown in the test examples described later.

[0057] The haze value of the adhesive layer (before S-UV irradiation) after curing with active energy rays in the adhesive sheet of this embodiment is preferably 2% or less, and particularly preferably 1% or less. This results in very high transparency, making it suitable for optical applications (for displays). There is no particular limitation on the lower limit of this haze value; it can be 0%. Furthermore, the haze values ​​of the adhesive layer before and after S-UV irradiation are preferably within the same range as the haze value of the adhesive layer before S-UV irradiation. The haze values ​​in this specification are measured according to JIS K7136:2000, and the specific test methods are shown in the test examples described later.

[0058] In this embodiment, the chromaticity b* (chromaticity b*1) of the adhesive layer cured by active energy rays in the adhesive sheet is preferably -20 to 20, more preferably -10 to 10, particularly preferably -5 to 5, and even more preferably -1 to 1, wherein -0.5 to 0.5 is preferred. This makes the adhesive layer almost colorless and transparent, suitable for optical applications.

[0059] The chromaticity b* (chromaticity b*2) of the adhesive layer cured by active energy rays and then irradiated with S-UV is preferably 20 to 20, more preferably -10 to 10, particularly preferably -6 to 6, and even more preferably -2 to 2, wherein -1 to 1 is preferred. Therefore, even after S-UV irradiation, the yellowing of the adhesive layer is minimal, and from a chromaticity perspective, it can be said to have excellent weather resistance.

[0060] The absolute value of the ratio of chromaticity b*2 to chromaticity b*1 (b*2 / b*1) is preferably 20 or less, more preferably 15 or less, particularly preferably 10 or less, even more preferably 5 or less, and most preferably 2 or less. Therefore, even after S-UV irradiation, the degree of yellowing of the adhesive layer is small, and from a chromaticity perspective, it can be said to have excellent weather resistance. Furthermore, the lower limit of the absolute value of the ratio (b*2 / b*1) is not particularly limited, but is most preferably 1.

[0061] In this embodiment, the adhesive constituting the adhesive layer is an active energy radiation-cured adhesive, which can be any of the following: acrylic adhesive, polyester adhesive, polyurethane adhesive, rubber adhesive, silicone adhesive, etc. Furthermore, the adhesive can be any of the following: latex-based, solvent-based, or solvent-free; and can be any of the following: cross-linked or non-cross-linked. Preferably, it is an acrylic adhesive with excellent adhesive properties and optical properties.

[0062] In this embodiment, the adhesive constituting the adhesive layer preferably contains a (meth)acrylate polymer, and more particularly preferably a crosslinked product containing a (meth)acrylate polymer as the main adhesive agent. Furthermore, in this embodiment, the adhesive constituting the adhesive layer preferably contains both the main adhesive agent and an active energy radiation curable component. That is, in this embodiment, the adhesive constituting the adhesive layer preferably contains both a crosslinked product of a (meth)acrylate polymer and an active energy radiation curable component. The crosslinked product of the (meth)acrylate polymer is preferably a crosslinked product of a (meth)acrylate polymer and a crosslinking agent.

[0063] Specifically, in this embodiment, the adhesive constituting the adhesive layer is preferably formed by crosslinking (preferably thermal crosslinking) an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylate polymer (A), a crosslinking agent (B), and an active energy radiation curable component (C). Furthermore, in this specification, the term (meth)acrylate refers to both acrylic acid and methacrylic acid. Other similar terms are also used. In addition, the term "polymer" also includes the concept of "copolymer."

[0064] (1) Each ingredient

[0065] (1-1) (Meth)acrylate polymer (A)

[0066] The (meth)acrylate polymer (A) preferably contains structural units derived from alkyl (meth)acrylates. This allows it to exhibit good adhesion. Furthermore, the hard monomers described later are not included in this alkyl (meth)acrylate.

[0067] From an adhesive perspective, alkyl methacrylates with 1 to 20 carbon atoms in the alkyl group are preferred as (meth)acrylates. Examples of alkyl methacrylates with 1 to 20 carbon atoms in the alkyl group include methyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, myristyl methacrylate, palmitate methacrylate, stearyl methacrylate, etc. These can be used alone or in combination of two or more. Among the above, from the perspective of further improving adhesiveness, alkyl methacrylates with 1 to 14 carbon atoms in the alkyl group are preferred, alkyl methacrylates with 2 to 10 carbon atoms in the alkyl group are more preferred, and alkyl methacrylates with 3 to 8 carbon atoms in the alkyl group are particularly preferred. Specifically, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate are preferred, with n-butyl acrylate or 2-ethylhexyl acrylate being particularly preferred.

[0068] For the (meth)acrylate polymer (A), from the perspective of imparting adhesiveness, as an upper limit, it is preferable to contain 99% by mass or less of structural units derived from (meth)acrylate alkyl esters, more preferably 96% by mass or less of structural units derived from (meth)acrylate alkyl esters, and particularly preferably 92% by mass or less of structural units derived from (meth)acrylate alkyl esters. Furthermore, considering compatibility with the adherend and the adherend itself, when using an acid-free adhesive as the obtained adhesive, it is preferable to contain 85% by mass or less of structural units derived from (meth)acrylate alkyl esters, more preferably 80% by mass or less of structural units derived from (meth)acrylate alkyl esters, particularly preferably 75% by mass or less of structural units derived from (meth)acrylate alkyl esters, and even more preferably 70% by mass or less of structural units derived from (meth)acrylate alkyl esters. On the other hand, as a lower limit, it is preferable to contain 40% by mass or more, more preferably 48% by mass or more, particularly preferably 54% by mass or more, and even more preferably 60% by mass or more. Furthermore, due to compatibility with the adherend, etc., when the obtained adhesive contains an acid component, it is preferable to contain 70% by mass or more of the above-mentioned structural units, more preferably 75% by mass or more of the above-mentioned structural units, particularly preferably 80% by mass or more of the above-mentioned structural units, and even more preferably 85% by mass or more of the above-mentioned structural units.

[0069] The (meth)acrylate polymer (A) preferably has structural units derived from monomers containing reactive functional groups. Thus, the reactive functional groups derived from the monomers containing reactive groups react with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), resulting in an adhesive with the desired cohesive force.

[0070] As monomers containing reactive groups, preferred examples include monomers having a hydroxyl group in the molecule (hydroxyl-containing monomers), monomers having a carboxyl group in the molecule (carboxyl-containing monomers), and monomers having an amino group in the molecule (amino-containing monomers). Among these, hydroxyl-containing monomers or carboxyl-containing monomers with excellent reactivity with the crosslinking agent (B) are preferred.

[0071] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and other hydroxyalkyl methacrylates. Among these, 2-hydroxyethyl methacrylate or 4-hydroxybutyl methacrylate is preferred from the perspective of reactivity with the crosslinking agent (B) and copolymerization with other monomers. They can be used alone or in combination of two or more.

[0072] Examples of carboxyl-containing monomers include ethylene unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid or methacrylic acid are preferred, with acrylic acid being particularly preferred, considering their reactivity with the crosslinking agent (B) and their copolymerization properties with other monomers. They can be used alone or in combination of two or more.

[0073] From the perspective of cohesive strength, the content of structural units derived from monomers containing reactive functional groups in the (meth)acrylate polymer (A) is preferably 1 to 40% by mass, more preferably 3 to 32% by mass, particularly preferably 6 to 26% by mass, and even more preferably 8 to 22% by mass. Wherein, when an acid-free adhesive is preferably used as the obtained adhesive, the above content is preferably 12 to 21% by mass, particularly preferably 16 to 20% by mass, or, when an adhesive containing an acid component is preferred, the above content is preferably 9 to 14% by mass.

[0074] The (meth)acrylate polymer (A) preferably contains structural units derived from hard monomers with a glass transition temperature (Tg) of 70°C or higher as homopolymers. Furthermore, the aforementioned monomers containing reactive functional groups are not included in the hard monomers. This improves the cohesive strength of the resulting adhesive and readily yields excellent foaming resistance. In particular, the presence of structural units derived from (meth)acrylates with 5 to 8 carbon atoms from alkyl groups tends to reduce cohesive strength; therefore, it is preferable to contain structural units derived from the aforementioned hard monomers. The glass transition temperature (Tg) of the aforementioned hard monomers as homopolymers is preferably 75 to 200°C, particularly preferably 80 to 180°C, and even more preferably 90 to 150°C.

[0075] Examples of the aforementioned hard monomers include methyl methacrylate (Tg 105℃), isobornyl acrylate (Tg 94℃), isobornyl methacrylate (Tg 180℃), adamantyl acrylate (Tg 115℃), and adamantyl methacrylate (Tg 141℃). They can be used alone or in combination of two or more.

[0076] Among the aforementioned hard monomers, methyl methacrylate or isobornyl acrylate is preferred from the perspective of preventing adverse effects on other properties such as adhesion and transparency, and further maximizing the performance of the hard monomers. In particular, methyl methacrylate is preferred from the perspective of weather resistance, and isobornyl acrylate, which has an intramolecular alicyclic structure (containing alicyclic monomers), is especially preferred from the perspective of adhesion.

[0077] When the (meth)acrylate polymer (A) contains structural units derived from the above-mentioned hard monomers, its content 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 perspective of easily exerting the desired cohesiveness and viscoelasticity as well as foam resistance.

[0078] The (meth)acrylate polymer (A) preferably contains structural units derived from monomers having nitrogen atoms within the molecule (nitrogen-containing monomers). When using alicyclic monomers, particularly isobornyl acrylate, as the aforementioned hard monomer, it is preferable to contain structural units derived from nitrogen-containing monomers. By including structural units derived from nitrogen-containing monomers, the adhesive can be imparted with a predetermined polarity, resulting in superior adhesion.

[0079] As the aforementioned nitrogen-containing monomer, from the perspective of imparting appropriate rigidity to the (meth)acrylate polymer (A), a monomer having a nitrogen-containing heterocycle is preferred. Furthermore, from the perspective of increasing the degree of freedom of the portion of the higher-order structure of the formed adhesive derived from the nitrogen-containing monomer, it is preferable that the nitrogen-containing monomer, apart from the polymerizable group used to form the (meth)acrylate polymer (A), does not contain reactive unsaturated double bond groups.

[0080] Examples of monomers 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, aziridineylethyl(meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazolium, N-vinylcarbazole, and N-vinylphthalimide. Among these, N-(meth)acryloylmorpholine, which exhibits superior adhesive properties, is preferred, and N-acryloylmorpholine is particularly preferred. They can be used alone or in combination of two or more.

[0081] When the (meth)acrylate polymer (A) contains structural units derived from nitrogen-containing monomers, its content is preferably 1 to 20% by mass, more preferably 2 to 16% by mass, particularly preferably 3 to 12% by mass, and even more preferably 4 to 8% by mass, from the perspective of easily achieving the desired viscoelasticity and superior adhesion.

[0082] The (meth)acrylate polymer (A) may, as needed, contain structural units derived from other monomers. As other monomers, monomers that do not contain reactive functional groups are preferred so as not to hinder the action of monomers containing reactive groups. Examples of such other monomers include methoxyethyl methacrylate, ethoxyethyl methacrylate, alkoxyalkyl methacrylates, vinyl acetate, styrene, etc. They can be used alone or in combination of two or more.

[0083] The (meth)acrylate polymer (A) can be obtained through solution polymerization, solvent-free polymerization, or emulsion polymerization. Preferably, it is a solution polymer obtained by solution polymerization. Because it is a solution polymer, it is easier to obtain a high molecular weight polymer, and the Ta-Tb values ​​tend to fall within the preferred range.

[0084] The polymerization of (meth)acrylate polymer (A) can be either random copolymer or block copolymer.

[0085] The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 100,000 to 3,000,000, more preferably 200,000 to 2,000,000, particularly preferably 300,000 to 1,200,000, and even more preferably 400,000 to 800,000. Therefore, the Ta-Tb values ​​mentioned above readily fall within the preferred range. Furthermore, the desired cohesive strength and viscoelasticity can be easily achieved, while appropriate adhesiveness can also be readily achieved. Additionally, the weight-average molecular weight in this specification is a value converted from standard polystyrene determined by gel permeation chromatography (GPC).

[0086] In addition, in the adhesive composition P, the (meth)acrylate polymer (A) can be used alone or in combination of two or more.

[0087] The content of (meth)acrylate polymer (A) in the adhesive composition P of this embodiment is preferably 60-99.9% by mass, more preferably 70-99% by mass, particularly preferably 80-98% by mass, and even more preferably 85-97% by mass. When an acid-free adhesive is preferred as the obtained adhesive, this content is preferably 90-96% by mass, and when an adhesive containing an acid component is preferred, this content is preferably 86-91% by mass. Thus, the above-mentioned Ta-Tb values ​​readily fall within the preferred range.

[0088] (1-2) Crosslinking agent (B)

[0089] Crosslinking agent (B) crosslinks (meth)acrylate polymer (A) by heating adhesive composition P, forming a well-formed three-dimensional network crosslinked structure. This yields an adhesive with predetermined cohesive strength and viscoelasticity, and the Ta-Tb values ​​readily fall within a preferred range. Furthermore, excellent foaming resistance is readily obtained.

[0090] As the aforementioned crosslinking agent (B), any crosslinking agent that reacts with the reactive groups (hydroxyl or carboxyl groups) present in the (meth)acrylate polymer (A) is acceptable. Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Here, when the (meth)acrylate polymer (A) contains structural units derived from hydroxyl-containing monomers, an isocyanate-based crosslinking agent with excellent reactivity with hydroxyl groups is preferably used as the crosslinking agent (B). Furthermore, when the (meth)acrylate polymer (A) contains structural units derived from carboxyl-containing monomers, an epoxy-based crosslinking agent with excellent reactivity with carboxyl groups is preferably used as the crosslinking agent (B). Additionally, the crosslinking agent (B) can be used alone or in combination of two or more.

[0091] Isocyanate-based crosslinking agents include at least polyisocyanate compounds. Examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and phthalimide diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; as well as their biuret forms, isocyanurate forms, and adducts as reaction products with low molecular weight compounds containing active hydrogen, such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. From the perspective of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates are preferred, and trimethylolpropane-modified toluene diisocyanate or trimethylolpropane-modified phthalimide diisocyanate are particularly preferred.

[0092] Examples of epoxy-based crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidylamine. From the perspective of reactivity with carboxyl groups, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane or N,N,N',N'-tetraglycidyl-m-xylenediamine are preferred.

[0093] Relative to 100 parts by weight of the (meth)acrylate polymer (A), the content of the crosslinking agent (B) in the adhesive composition P is preferably 0.001 to 10 parts by weight, more preferably 0.005 to 5 parts by weight, and particularly preferably 0.01 to 1 part by weight. When an acid-free adhesive is preferably used as the obtained adhesive, this content is preferably 0.05 to 0.8% by weight, more preferably 0.1 to 0.6% by weight, and from the perspective of weather resistance, preferably 0.2 to 0.4 parts by weight. Furthermore, when the adhesive preferably contains an acid component as the obtained adhesive, this content is preferably 0.015 to 0.5% by weight, more preferably 0.02 to 0.1 parts by weight. Thus, the above-mentioned Ta-Tb values ​​easily fall within the preferred range.

[0094] (1-3) Active energy ray curing component (C)

[0095] By including an adhesive composition P containing an active energy ray curable component (C), the resulting adhesive becomes an active energy ray curable adhesive.

[0096] The active energy ray curable component (C) is not particularly limited as long as it is cured by irradiation with active energy rays and can achieve the above-mentioned physical properties. It can be any one of monomers, oligomers, or polymers, or a mixture thereof. Among them, polyfunctional acrylate monomers that make it easy for the above-mentioned Ta-Tb values ​​to fall within the preferred range are preferably included.

[0097] Examples of multifunctional acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypentyl acid neopentyl glycol di(meth)acrylate, dicyclopentyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified di(meth)acrylate, di(acryloyloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, etc. Difunctional types; trifunctional types including 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, ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate, etc.; tetrafunctional types including diglycerol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, etc.; pentafunctional types including propionic acid-modified dipentaerythritol penta(meth)acrylate, etc.; hexafunctional types including dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc., etc. Of the above, from the perspective of the foaming resistance of the obtained adhesive, polyfunctional acrylate monomers containing an isocyanurate structure, such as di(acryloyloxyethyl)isocyanurate, tri(acryloyloxyethyl)isocyanurate, and ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate, are preferred. Polyfunctional acrylate monomers with trifunctionality or higher and containing an isocyanurate structure are more preferred, and ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate is particularly preferred. They can be used alone or in combination of two or more. Furthermore, from the perspective of the adhesive's ability to readily exhibit the desired viscoelasticity, the polyfunctional acrylate monomers preferably have a molecular weight of less than 20,000, more preferably less than 10,000, and particularly preferably less than 5,000. Furthermore, from the perspective of compatibility with the (meth)acrylate polymer (A), a molecular weight of less than 1,000 is preferred.

[0098] Relative to 100 parts by weight of the (meth)acrylate polymer (A), the content of the active energy radiation curable component (C) in the adhesive composition P is preferably 1 to 50 parts by weight, more preferably 2 to 40 parts by weight, particularly preferably 3 to 30 parts by weight, and even more preferably 4 to 20 parts by weight. When an acid-free adhesive is preferably used as the obtained adhesive, this content is preferably 4.5 to 10 parts by weight, and even more preferably 5 to 8 parts by weight. Furthermore, when an adhesive preferably contains an acid component as the obtained adhesive, this content is preferably 5 to 16 parts by weight, and even more preferably 8 to 14 parts by weight. Thus, the above-mentioned Ta-Tb values ​​readily fall within the preferred range.

[0099] (1-4) Photopolymerization initiator (D)

[0100] When ultraviolet light is used as the active energy ray for curing the adhesive layer, the adhesive composition P preferably contains a photopolymerization initiator (D). This allows for efficient curing of the active energy ray curable component (C) and reduces polymerization curing time and the amount of ultraviolet light irradiation.

[0101] Examples of photopolymerization initiators (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinyl-propane-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)one, diphenyl ketone, and p-phenyldiphenyl Ketones, 4,4'-diethylaminodiphenyl ketone, dichlorodiphenyl ketone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligomeric [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc. They can be used alone or in combination of two or more.

[0102] Of the above, from the perspective of suppressing the formation of needle-like cracks, phosphine-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, or mixtures of diphenyl ketone and 1-hydroxycyclohexylphenyl ketone, are particularly preferred; from the perspective of weather resistance and foaming resistance, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, or mixtures of diphenyl ketone and 1-hydroxycyclohexylphenyl ketone, are particularly preferred.

[0103] The content of photopolymerization initiator (D) in the adhesive composition P is preferably 1 to 40 parts by mass relative to 100 parts by mass of the active energy ray curing component (C), more preferably 3 to 30 parts by mass, particularly preferably 6 to 22 parts by mass, and even more preferably 8 to 14 parts by mass. Therefore, the resulting adhesive readily satisfies the aforementioned physical properties.

[0104] (1-5) Silane coupling agent (E)

[0105] The adhesive composition P preferably further contains a silane coupling agent (E). This improves the adhesion between the adhesive and the glass component when the adherend is a glass component. Furthermore, even when the adherend is a plastic sheet, the adhesion between the adhesive and the plastic sheet is improved. Thus, the aforementioned physical properties are easily satisfied, and excellent foaming resistance is readily obtained in the adhesive.

[0106] As a silane coupling agent (E), an organosilicon compound having at least one alkoxysilane alkyl group in the molecule is preferred, which has good compatibility with the (meth)acrylate polymer (A) and is transparent.

[0107] Examples of such silane coupling agents (E) include, for example, silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloyloxypropyltrimethoxysilane; silicon compounds with epoxy structures such as 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane. Silicates containing mercapto groups, such as methoxymethylsilane; amino compounds containing amino groups, such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; condensates of 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one thereof with alkyl compounds containing methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane, etc. These compounds can be used alone or in combination of two or more.

[0108] Relative to 100 parts by weight of the (meth)acrylate polymer (A), the content of the silane coupling agent (E) in the adhesive composition P is preferably 0.01 to 10 parts by weight, more preferably 0.04 to 5 parts by weight, particularly preferably 0.08 to 1 part by weight, further preferably 0.12 to 0.5 parts by weight, and most preferably 0.15 to 0.35 parts by weight. This readily results in excellent adhesion, and also readily exhibits excellent weather resistance and foaming resistance.

[0109] (1-6) Various additives

[0110] The adhesive composition P may contain, as needed, various additives commonly used in acrylic adhesives, such as light stabilizers, ultraviolet absorbers, oxygen absorbers, antioxidants, tackifiers, softeners, colorants, infrared absorbers, rust inhibitors, antistatic agents, fillers, refractive index modifiers, etc.

[0111] Examples of light stabilizers include hindered amine light stabilizers and hindered phenolic light stabilizers. From the perspective of suppressing needle-like cracks, hindered amine light stabilizers are preferred. Examples of hindered amine light stabilizers include tetrakis(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidinyl)1,2,3,4-butanetetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1-undecyloxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate, 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, and 2,2,6,6-tetramethyl-4-piperidinyl methacrylate. Among them, bis(1-undecyloxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonates are preferred from the perspective of weather resistance and foaming resistance. They can be used alone or in combination of two or more.

[0112] The content of light stabilizer in the adhesive composition P is preferably 0.01 to 20 parts by weight relative to 100 parts by weight of (meth)acrylate polymer (A), more preferably 0.05 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, further preferably 0.2 to 2 parts by weight, and most preferably 0.3 to 1 part by weight. This readily suppresses needle-like cracks and also provides excellent foaming resistance.

[0113] (2) Preparation of adhesive composition

[0114] The adhesive composition P can be prepared by preparing a (meth)acrylate polymer (A), and mixing the obtained (meth)acrylate polymer (A), crosslinking agent (B), and active energy ray curable component (C), while adding photopolymerization initiator (D), silane coupling agent (E), additives, etc. as needed.

[0115] (Meth)acrylate polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer using conventional free radical polymerization. The polymerization of (meth)acrylate polymer (A) is preferably carried out by solution polymerization, using a polymerization initiator as desired. However, the invention is not limited thereto, and polymerization can also be carried out without a solvent.

[0116] Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more can be used in combination. Examples of polymerization initiators include azo compounds and organic peroxides, and two or more can be used in combination. Furthermore, in the above polymerization process, the weight-average molecular weight of the obtained polymer can be adjusted by incorporating chain transfer agents such as 2-mercaptoethanol.

[0117] After obtaining (meth)acrylate polymer (A), a crosslinking agent (B), an active energy radiation curable component (C), and, as needed, a photopolymerization initiator (D), a silane coupling agent (E), additives, and a diluent are added to a solution of (meth)acrylate polymer (A), and thoroughly mixed to obtain an adhesive composition P (coating solution) diluted with a solvent. Furthermore, if any of the above components is used in solid form, or if precipitation occurs when mixed with other components in an undiluted state, that component can be dissolved or diluted separately in a diluent beforehand and then mixed with the other components.

[0118] As diluents for the above-mentioned purposes, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane can be used; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and solvents such as ethyl cellosolve.

[0119] The concentration and viscosity of the coating solution prepared in this way are not particularly limited as long as they are within the range suitable for coating, and can be appropriately selected according to the situation. For example, the adhesive composition P can be diluted to a concentration of 10 to 60% by mass. Furthermore, the addition of a diluent or the like is not necessary when obtaining the coating solution; if the adhesive composition P has a viscosity suitable for coating, a diluent 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) is directly used as the diluent.

[0120] (3) Preparation of adhesive

[0121] After applying the above adhesive composition P onto the desired object, it is crosslinked to obtain an adhesive (adhesive layer).

[0122] Crosslinking of the adhesive composition P can be achieved by heat treatment. This heat treatment can also be performed simultaneously with the drying process after coating of the adhesive composition P. The heating temperature for the heat treatment is preferably 50–150°C, particularly preferably 70–120°C. Furthermore, the heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

[0123] Following heat treatment, a curing period of approximately 1 to 2 weeks can be provided at room temperature (e.g., 23°C, 50% RH), if required. If a longer curing period is required, the adhesive forms after the curing period; if no curing period is required, the adhesive forms after the heat treatment is completed.

[0124] Through the above-described heat treatment (and aging), a cross-linked product of (meth)acrylate polymer (A) is formed by cross-linking agent (B).

[0125] (4) Thickness of adhesive layer

[0126] From the perspective of adhesion and foaming resistance, the thickness of the adhesive layer in this embodiment (the value measured according to JIS K7130) is preferably 1 to 1000 μm, more preferably 10 to 800 μm, particularly preferably 30 to 600 μm, and from the perspective of weather resistance, preferably 50 to 400 μm, further preferably 80 to 300 μm, wherein preferably 120 to 260 μm.

[0127] (5) Specific structure of the adhesive sheet

[0128] The specific structure of the adhesive sheet as an example of this implementation scheme is shown in Figure 1 .

[0129] like Figure 1As shown, in one embodiment, the adhesive sheet 1 is composed of two release sheets 12a and 12b, and an adhesive layer 11 sandwiched between the two release sheets 12a and 12b in a manner that contacts the release surfaces of the two release sheets 12a and 12b respectively. Furthermore, in this specification, the release surface of a release sheet refers to a surface in the release sheet that has peelability, including either a surface that has undergone a peeling treatment or a surface that exhibits peelability even without a peeling treatment.

[0130] Adhesive layer 11 is the adhesive layer in the adhesive sheet of the above-described embodiment.

[0131] The aforementioned release tabs 12a and 12b protect the adhesive layer 11 until adhesive sheets 1A and 1B are used, and are peeled off when the adhesive sheets (adhesive layer) are used. In the adhesive sheet 1 of this embodiment, one or both of the release tabs 12a and 12b are not necessary.

[0132] For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylate copolymer film, ethylene-(meth)acrylate polymer film, polystyrene film, polycarbonate film, polyimide film, fluoropolymer film, etc., can be used as release sheets 12a and 12b. Furthermore, cross-linked films of these materials can also be used. Additionally, laminated films of these materials can also be used. Moreover, from the perspective of the Sustainable Development Goals (SDGs), materials with high biomass content, recyclable or reusable materials, or materials that have already been recycled or reused can be used as materials constituting the release sheets.

[0133] Preferably, the peeling surfaces (especially the surfaces in contact with the adhesive layer 11) of the aforementioned release sheets 12a and 12b are subjected to a peeling treatment. Examples of release agents used in the peeling treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0134] There are no particular restrictions on the thickness of the release strips 12a and 12b, which are usually around 20 to 150 μm.

[0135] From an operational perspective, among the two peeling sheets 12a and 12b, it is preferable that one peeling sheet is a heavy-peeling type with greater peeling force, and the other peeling sheet is a light-peeling type with less peeling force.

[0136] (6) Manufacturing of adhesive sheets

[0137] As an example of manufacturing the adhesive sheet 1, a coating liquid containing the adhesive composition P is applied to the release surface of one release sheet 12 (or 12b), and then heat-treated to thermally crosslink the adhesive composition P to form a coating layer. Afterward, the release surface of another release sheet 12b (or 12a) is laminated onto this coating layer. If a curing period is required, the coating layer is allowed to form the adhesive layer 11 after a curing period; otherwise, the coating layer is directly formed into the adhesive layer 11. The adhesive sheet 1 is obtained through the above process. The conditions for heat treatment and curing are as described above.

[0138] Methods for applying the coating liquid to the adhesive composition P can include, for example, rod coating, doctor blade coating, roller coating, blade coating, die coating, gravure coating, etc.

[0139] [Display Body]

[0140] One embodiment of the present invention provides a display body comprising a display body component, another display body component, and an adhesive layer for bonding the one display body component and the other display body component together. This adhesive layer is formed from the adhesive layer of the adhesive sheet described in the above embodiment.

[0141] At least one of the aforementioned display body constituent components and the other display body constituent component may have a step on the surface of at least one side that is bonded by the aforementioned adhesive layer.

[0142] Both of the aforementioned display body components can be rigid sheets. When the two rigid sheets are bonded together, since the rigid sheets are hard and will not bend, the two rigid sheets are pressed in the vertical direction with the adhesive layer attached to one of the rigid sheets, thereby making each rigid sheet and the adhesive layer adhere tightly to each other and bonding the two rigid sheets together.

[0143] The following is a description of an embodiment of the present invention with reference to the accompanying drawings.

[0144] like Figure 2 As shown, the display body 2 of this embodiment includes a first display body component 21 (one display body component), a second display body component 22 (another display body component), and a cured adhesive layer 11' located between them and bonding the first display body component 21 and the second display body component 22 together.

[0145] At least one of the first display body component 21 and the second display body component 22 may have a step on the surface of at least one side that is bonded by the cured adhesive layer 11'. Figure 2In the embodiment shown, the first display body component 21 has a step difference on the surface of the adhesive layer 11' after curing, caused by the printing layer 3, etc.

[0146] The cured adhesive layer 11' in the above-mentioned display body 2 is a layer that is cured by irradiation of the adhesive layer 11 of the above-mentioned adhesive sheet 1 through active energy rays.

[0147] As a display device 2, examples include liquid crystal displays (LCDs), light-emitting diode (LED) displays, organic electroluminescent (OLED) displays, electronic paper, and touch panels. Additionally, LED displays include those using mini LEDs and micro LEDs.

[0148] In addition to glass plates, plastic plates, etc., the first display body component 21 is preferably a protective panel formed of a laminate containing glass plates, plastic plates, etc. In this case, the printed layer 3 is usually formed in a frame shape on the adhesive layer 11' side after the first display body component 21 has cured.

[0149] The glass plate mentioned above is not particularly limited, and examples include chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass. The thickness of the glass plate is not particularly limited, but is typically 0.1–5 mm, preferably 0.2–2 mm.

[0150] The plastic sheet used is not particularly limited; for example, acrylic sheets and polycarbonate sheets can be included. The thickness of the plastic sheet is not particularly limited, but is typically 0.2–5 mm, preferably 0.4–3 mm.

[0151] Furthermore, various functional layers (transparent conductive film, metal layer, silicon dioxide layer, hard coating, anti-glare layer, etc.) can be applied to one or both sides of the aforementioned glass plate, plastic plate, etc., and optical components can also be stacked. In addition, the transparent conductive film and metal layer can be patterned.

[0152] The second display component 22 is preferably an optical component, a display module (e.g., a liquid crystal (LCD) module, a light-emitting diode (LED) module, an organic electroluminescent (OLED) module, an optical component that is part of the display module, or a laminate containing the display module, which is intended to be attached to the first display component 21.

[0153] Examples of the aforementioned optical components include anti-scattering films, polarizers (polarizing films), polarizers, retardation plates (retardation films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transparent reflective films, and transparent conductive films. As a transparent conductive film, an ITO-PET film in which a tin-doped indium oxide (ITO) layer is formed on one side of a polyethylene terephthalate (PET) film is preferably an example.

[0154] The material constituting the printed layer 3 is not particularly limited, and conventional printing materials can be used. The thickness of the printed layer 3, i.e., the height of the step, is preferably 0.5 to 50 μm, more preferably 1 to 30 μm, and particularly preferably 3 to 20 μm. By making the thickness of the printed layer 3 within the above range, the step following caused by the cured adhesive layer 11' can be effectively utilized, and the target concealment of the printed layer 3 can be sufficiently ensured. In addition, the printed layer 3 is usually formed in a frame shape on the side of the cured adhesive layer 11' of the display body constituent components.

[0155] In order to manufacture the above-mentioned display body 2, as an example, one of the release tabs 12a of the adhesive sheet 1 can be peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 can be attached to the side of the first display body constituent member 21 where the printed layer 3 is located.

[0156] Next, another release tab 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display component constituent member 22 to obtain a display body. Furthermore, as another example, the bonding order of the first display component constituent member 21 and the second display component constituent member 22 can be changed.

[0157] After the laminate of the first display body component 21 and the adhesive layer 11 is bonded to the second display body component 22, the adhesive layer 11 is irradiated with active energy rays through the first display body component 21 and / or the second display body component 22, so that the adhesive layer 11 is cured into a cured adhesive layer 11'.

[0158] Reactive energy rays refer to electromagnetic waves or charged particle rays that possess energy quanta. Specifically, examples include ultraviolet rays and electron rays. Among reactive energy rays, ultraviolet rays, which are particularly easy to process, are preferred.

[0159] Ultraviolet (UV) irradiation can be performed using high-pressure mercury lamps, Heraeus H lamps, xenon lamps, etc. The UV irradiation dose, measured by a lux meter, is preferably 50–1000 mW / cm². 2 In addition, the preferred light intensity is 50–10000 mJ / cm². 2 More preferably 80–5000 mJ / cm 2The preferred value is 300–2000 mJ / cm³. 2 On the other hand, electron beam irradiation can be carried out by electron beam accelerators, etc., and the preferred irradiation dose is about 10 to 1000 krad.

[0160] In the above-mentioned display body 2, since the adhesive constituting the cured adhesive layer 11' has the above-mentioned physical properties, even when exposed to high-intensity ultraviolet light for a long time (e.g., 20 hours, 40 hours, etc.), the generation of needle-like cracks in the cured adhesive layer 11' can be suppressed, and the weather resistance is excellent.

[0161] The embodiments described above are provided for ease of understanding of the invention and are not intended to limit the invention. Therefore, the elements disclosed in the above embodiments are intended to include all design changes and equivalents that fall within the scope of the invention.

[0162] For example, one or both of the release tabs 12a and 12b in the adhesive sheet 1 can be omitted. Alternatively, the release tabs 12a and / or 12b can be replaced by laminating the desired optical components. Furthermore, the first display body component 21 may not have a step. In addition, not only the first display body component 21, but also the second display body component 22 may have a step on the adhesive layer 11' side after curing.

[0163] Furthermore, in this specification, when "X to Y" (where X and Y are arbitrary numbers) is used, unless otherwise stated, it means "X or more and Y or less," and also includes the meaning of "preferably larger than X" or "preferably smaller than Y." Additionally, when "X or more" (where X is any number) is used, unless otherwise stated, it includes the meaning of "preferably larger than X"; when "Y or less" (where Y is any number) is used, unless otherwise stated, it includes the meaning of "preferably smaller than Y."

[0164] Example

[0165] The invention will be described in more detail below by way of examples, but the scope of the invention is not limited to these examples.

[0166] [Example 1]

[0167] 1. Preparation of (meth)acrylate polymers

[0168] (Meth)acrylate polymer (A) was prepared by copolymerization of 65 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of isobornyl acrylate, 5 parts by mass of N-acryloylmorpholine, and 15 parts by mass of 2-hydroxyethyl acrylate using solution polymerization. The weight-average molecular weight (Mw) of this (meth)acrylate polymer (A) was determined to be 500,000 by the method described later.

[0169] 2. Preparation of adhesive compositions

[0170] 100 parts by weight of (meth)acrylate polymer (A) obtained in step (1) above (conversion value of solid content, the same applies below), 0.15 parts by weight of isocyanate crosslinking agent (B1; manufactured by Mitsui Chemicals, Inc., product name "TAKENATE D-101E"), 5.2 parts by weight of ε-caprolactone-modified tri-(2-acryloyloxyethyl)isocyanurate (manufactured by SHIN-NAKAMURA CHEMICAL CO.,LTD., product name "NKEster A-9300-1CL") as active energy ray curing component (C), 0.9 parts by weight of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (D1) as photopolymerization initiator, and 0.27 parts by weight of 3-glycidyl etheroxypropyltrimethoxysilane as silane coupling agent (E) are mixed, stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of adhesive composition.

[0171] Table 1 here shows the components (converted to solids) of the adhesive composition when (meth)acrylate polymer (A) is set at 100 parts by weight. Details of the abbreviations, etc., recorded in Table 1 are described below.

[0172] [(Meth)acrylate polymer (A)]

[0173] 2EHA: 2-Ethylhexyl acrylate

[0174] BA: n-Butyl acrylate

[0175] MMA: Methyl methacrylate

[0176] IBXA: Isoborneol Acrylate

[0177] ACMO: N-Acryloylmorpholine

[0178] HEA: 2-Hydroxyethyl acrylate

[0179] AA: Acrylic acid

[0180] [Crosslinking agent (B)]

[0181] B1: Isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "TAKENATE D-101E")

[0182] B2: 1,3-Bis(N,N'-Diglycidylaminomethyl)cyclohexane (epoxy crosslinking agent)

[0183] [Photopolymerization Initiator (D)]

[0184] D1: 2,4,6-Trimethylbenzoyl-diphenyl-phosphine oxide

[0185] D2: Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide

[0186] D3: A mixture of diphenyl ketone and 1-hydroxycyclohexylphenyl ketone (mass ratio 50:50)

[0187] D4: 1-Hydroxycyclohexylphenyl ketone

[0188] D5: A mixture of 2-oxy-2-phenylacetic acid-2-(2-oxo-2-phenylacetoxyethoxy)ethyl ester and 2-oxy-2-phenylacetic acid-2-(2-hydroxyethoxy)ethyl ester (manufactured by IGM Resins, product name "OMNIRAD754")

[0189] [Light stabilizer]

[0190] F1: Tetra(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylic acid ester

[0191] F2: Bis(1-undecyloxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate

[0192] 3. Manufacturing of adhesive sheets

[0193] The coating solution of the adhesive composition obtained in step 2 above is coated onto the release-treated surface of a heavy-release release sheet R1, one side of which has been treated with a silicone-based release agent, using a coating machine. Then, it is heat-treated at 90°C for 1 minute to form a coating layer. Next, the coating layer on the release sheet R1 is bonded to a light-release release sheet R2, one side of which has been treated with a silicone-based release agent, so that the release-treated surface of the release sheet R2 is in contact with the coating layer. The bond is then cured at 23°C and 50% RH for 7 days to produce an adhesive sheet with an adhesive layer of 50 μm thickness. In other words, an adhesive sheet is formed by the structure of release sheet R1 / adhesive layer (thickness: 50 μm) / release sheet R2.

[0194] Furthermore, the thickness of the adhesive layer was measured using a constant pressure thickness gauge (manufactured by Teclock, product name "PG-02") according to JIS K7130. Additionally, regarding the peel force of release tabs R1 and R2 in the obtained adhesive sheet, it was confirmed that the peel force of release tab R1 is greater than that of release tab R2.

[0195] [Examples 2-7, Comparative Examples 1-3]

[0196] The types and weight-average molecular weights (Mw) of the monomers constituting the (meth)acrylate polymer (A), the type and amount of crosslinking agent (B), the amount of active energy radiation curable component (C), and the type and amount of photopolymerization initiator (D) were changed according to Table 1. Otherwise, the adhesive sheet was manufactured in the same manner as in Example 1. Furthermore, in Examples 3 and 4, light stabilizers (F1 / F2) were further added according to the amounts shown in Table 1.

[0197] Here, the weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight converted from polystyrene determined by gel permeation chromatography (GPC) under the following conditions (GPC determination).

[0198] <Measurement Conditions>

[0199] • Measuring apparatus: Manufactured by TOSOH CORPORATION; HLC-8320

[0200] • GPC column (passes through in the following order): Manufactured by TOSOH CORPORATION

[0201] TSK gel super HH

[0202] TSK gel super HM-H

[0203] TSK gel super H2000

[0204] • Solvent for determination: Tetrahydrofuran

[0205] • Measurement temperature: 40℃

[0206] [Experimental Example 1] (Determination of Gel Fraction)

[0207] Multiple layers of adhesive were stacked on the adhesive sheets manufactured in the examples and comparative examples to create an adhesive layer with a thickness of 250 μm. The adhesive layer (thickness: 250 μm) was cut into 70 mm × 150 mm pieces, wrapped in a polyester mesh (mesh size 200), and its mass was weighed using a precision balance. The mass of the mesh was then subtracted to calculate the mass of the adhesive. This mass was designated as M1.

[0208] The adhesive wrapped around the aforementioned polyester mesh was then immersed in ethyl acetate at room temperature (23°C) for 24 hours. Afterward, the adhesive was removed and air-dried at 23°C and 50% RH for 24 hours, then placed in an oven at 80°C for 12 hours. After drying, its mass was measured using a precision balance, and the mass of the mesh was subtracted to calculate the mass of the adhesive. This mass was designated as M2. The gel fraction (%) before UV exposure was expressed as (M2 / M1) × 100. The results are shown in Table 2.

[0209] Furthermore, multiple layers of adhesive layers were stacked on the adhesive sheets manufactured in the Examples and Comparative Examples to form an adhesive layer with a thickness of 250 μm. This adhesive layer (thickness: 250 μm) was irradiated with active energy rays (ultraviolet; UV) to cure it. The gel fraction (%) of the adhesive layer cured by active energy rays was measured in the same manner as described above. The results are shown in Table 2. The irradiation conditions of the active energy rays are as follows.

[0210] <Conditions of Irradiation by Active Energy Rays>

[0211] • Use a high-pressure mercury lamp

[0212] Illuminance: 200mW / cm² 2 Light intensity: 1000 mJ / cm 2

[0213] • The UV illuminance photometer used is the "UVPF-A1" manufactured by EYE GRAPHICS.

[0214] Furthermore, multiple layers of adhesive layers from the adhesive sheets manufactured in the Examples and Comparative Examples were stacked to create an adhesive layer with a thickness of 250 μm. Using this adhesive layer (thickness: 250 μm), two soda-lime glass plates (manufactured by NIPPON SHEETGLASS CO.,LTD., thickness: 1.1 mm, length 70 mm × width 150 mm) were bonded together to create a laminate (soda-lime glass plate / adhesive layer (thickness: 250 μm) / soda-lime glass plate). This laminate was then irradiated with active energy rays (ultraviolet; UV) under the aforementioned active energy ray irradiation conditions to cure the adhesive layer. Next, the laminate containing the adhesive layer cured by active energy rays was irradiated with ultraviolet light (S-UV irradiation) under the following conditions. Then, the adhesive layer was separated from the two soda-lime glass plates in the S-UV irradiated laminate. The gel fraction (%) of the adhesive in the separated adhesive layer was measured in the same manner as described above. The results are shown in Table 2.

[0215] <Ultraviolet radiation conditions>

[0216] • Equipment: Eye Super UV Tester SUV-W151 (manufactured by IWASAKI ELECTRIC CO.,LTD.)

[0217] • UV lamp: ME06-L31WX / SUV (manufactured by IWASAKI ELECTRIC CO.,LTD.)

[0218] • Water cooling jacket: WJ50-SUV-4 (manufactured by IWASAKI ELECTRIC CO.,LTD.)

[0219] Illuminance: 100mW / cm² 2

[0220] • Irradiation time: 120 hours

[0221] • Light intensity: 43.2 kJ / cm² 2

[0222] Temperature: 63℃

[0223] Humidity: 70% RH

[0224] • Temperature and humidity control: Closed-loop system

[0225] [Experimental Example 2] (Determination of the average peak molecular weight of sol components)

[0226] Multiple layers of adhesive layers were stacked on the adhesive sheets manufactured in the Examples and Comparative Examples to form an adhesive layer with a thickness of 250 μm. Under the same active energy radiation irradiation conditions as in Test Example 1, the adhesive layer was irradiated with active energy radiation (ultraviolet; UV) to cure it. The adhesive of the cured adhesive layer was concentrated using an evaporator with ethyl acetate (adhesive impregnation, after removal), obtained in the same manner as in Test Example 1, to obtain a sol component. This sol component was then diluted with tetrahydrofuran to a 0.3% by mass solution, filtered through a 0.45 μm filter, and the average peak molecular weight (Mp; before S-UV) of the sol component was determined by GPC measurement. The GPC measurement conditions were as described above. The results are shown in Table 2.

[0227] Furthermore, using the adhesive sheets manufactured in the Examples and Comparative Examples, a laminate identical to that of Test Example 1 was prepared. Under the same active energy ray irradiation conditions as in Test Example 1, the laminate was irradiated with active energy rays (ultraviolet; UV) to cure the adhesive layer. Next, the laminate having the adhesive layer cured by active energy rays was irradiated with ultraviolet light (S-UV irradiation) under the same ultraviolet irradiation conditions as in Test Example 1. Then, the adhesive layer was separated from the two soda-lime glass plates in the S-UV irradiated laminate. For the adhesive of the separated adhesive layer, the average peak molecular weight (Mp; after S-UV) of the sol component was measured in the same manner as above. The results are shown in Table 2.

[0228] [Experimental Example 3] (Determination of Dynamic Viscoelasticity)

[0229] Multiple layers of adhesive were stacked on the adhesive sheets manufactured in the examples and comparative examples to form an adhesive layer with a thickness of 250 μm. Under the same active energy radiation irradiation conditions as in Test Example 1, the adhesive layer was irradiated with active energy radiation (ultraviolet; UV) to cure it. A cylinder with a diameter of 8 mm (height of 0.25 mm) was punched from the active energy radiation-cured adhesive layer and used as a sample.

[0230] For the above samples, according to JIS K7244-1, the dynamic viscoelasticity was measured using a viscoelasticity measuring apparatus (manufactured by Anton Paar, product name "MCR302") by torsional shear method under the following conditions, and the storage modulus G'(-15) at -15℃ (MPa; before S-UV), the storage modulus G'(23) at 23℃ (MPa; before S-UV), and the storage modulus G'(100) at 100℃ (MPa; before S-UV) were derived. Furthermore, the peak temperature (℃) of the loss tangent tanδ (before S-UV: Tb) was also derived. The results are shown in Table 2.

[0231] Measurement frequency: 1Hz

[0232] Measurement temperature range: -20℃~140℃

[0233] Heating rate: 4℃ / min

[0234] Furthermore, using the adhesive sheets manufactured in the Examples and Comparative Examples, a laminate identical to that of Test Example 1 was prepared. Under the same active energy ray irradiation conditions as in Test Example 1, the laminate was irradiated with active energy rays (ultraviolet; UV) to cure the adhesive layer. Next, the laminate containing the adhesive layer cured by the active energy rays was irradiated with ultraviolet light (S-UV irradiation) under the same ultraviolet irradiation conditions as in Test Example 1. Then, the adhesive layer was separated from the two soda-lime glass plates in the S-UV irradiated laminate. For the separated adhesive layer, the dynamic viscoelasticity was measured as described above, and the storage modulus G'(-15) at -15°C (MPa; after S-UV), the storage modulus G'(23) at 23°C (MPa; after S-UV), and the storage modulus G'(100) at 100°C (MPa; after S-UV) were derived. Furthermore, the peak temperature (°C) of the loss tangent tanδ (after S-UV: Ta) was also derived. The results are shown in Table 2.

[0235] In addition, calculate the value of Ta minus Tb (Ta-Tb) obtained above. The results are shown in Table 2.

[0236] [Experimental Example 4] (Determination of Adhesion)

[0237] Peel off the release sheet R2 from the adhesive sheet manufactured in the examples and comparative examples, and adhere the exposed adhesive layer to the easy-adhesive layer on one side of a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO., LTD., product name "COSMOSHINE A4360", thickness: 100 μm) having an easy-adhesive layer on both sides, to obtain a laminate of release sheet R1 / adhesive layer / PET film. Cut the above laminate into pieces 25 mm wide and 100 mm long, and use them as samples.

[0238] Under conditions of 23°C and 50% RH, the release strip R1 was peeled off from the above sample, and the exposed adhesive layer was attached to soda-lime glass (manufactured by NIPPON SHEET GLASS CO.,LTD.). The mixture was then subjected to a pressure of 0.5 MPa at 50°C for 20 minutes in an autoclave manufactured by KURIHARA SEISAKUSHO Co.,Ltd. Then, under the same active energy ray irradiation conditions as in Test Example 1, the adhesive layer was cured by irradiating the soda-lime glass with active energy rays (ultraviolet; UV).

[0239] Then, the mixture was placed at 23°C and 50% RH for 24 hours, after which the adhesion was measured using a tensile testing machine (manufactured by ORIENTEC Co., Ltd., product name "TENSILON") at a peel speed of 300 mm / min and a peel angle of 180°. Conditions not described here were measured according to JIS Z0237:2009. The results are shown in Table 2.

[0240] [Experimental Example 5] (Determination of Total Transmittance)

[0241] Multiple layers of adhesive layers were stacked on the adhesive sheets manufactured in the Examples and Comparative Examples to form an adhesive layer with a thickness of 250 μm. Using this adhesive layer (thickness: 250 μm), a laminate was fabricated in the same manner as in Test Example 1. Under the same active energy ray irradiation conditions as in Test Example 1, the adhesive layer was irradiated with active energy rays (ultraviolet; UV) to cure it, and this was used as the test sample. After background measurement with soda-lime glass, the total transmittance (%; before S-UV) of the above-mentioned test sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") according to JISK 7361-1:1997. The results are shown in Table 2. The same measurement results were also obtained when measuring the total transmittance of the adhesive layer before active energy ray curing.

[0242] [Experimental Example 6] (Determination of Haze Value)

[0243] The test sample was prepared in the same manner as in Test Example 5. For this test sample, after background measurement with glass, the haze value (%; before S-UV) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") according to JIS K7136:2000. The results are shown in Table 2. Similarly, the same measurement results were obtained when measuring the haze value of the adhesive layer before curing with active energy rays.

[0244] [Experimental Example 7] (Determination of L*a*b*)

[0245] Using the adhesive sheets manufactured in the Examples and Comparative Examples, a laminate identical to that of Test Example 1 was prepared. Under the same active energy ray irradiation conditions as in Test Example 1, the laminate was irradiated with active energy rays (ultraviolet; UV) to cure the adhesive layer. The chromaticity b* (chromaticity b*1) of the adhesive layer after irradiation was simultaneously measured using a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SQ2000") as specified by the CIE 1976 L*a*b* color system. The results are shown in Table 2.

[0246] Furthermore, using the adhesive sheets manufactured in the Examples and Comparative Examples, a laminate identical to that of Test Example 1 was prepared. Under the same active energy ray irradiation conditions as in Test Example 1, the laminate was irradiated with active energy rays (ultraviolet; UV) to cure the adhesive layer. Next, the laminate containing the adhesive layer cured by the active energy rays was irradiated with ultraviolet light (S-UV irradiation) under the same ultraviolet irradiation conditions as in Test Example 1. Then, the colorimetric b* (colorimetric b*2) of the adhesive layer in the S-UV irradiated laminate was measured in the same manner as described above. The results are shown in Table 2.

[0247] Furthermore, the absolute value of the ratio of chromaticity b*2 to chromaticity b*1 (b*2 / b*1) obtained above was calculated. The results are shown in Table 2.

[0248] [Experimental Example 8] (Evaluation of Weather Resistance)

[0249] Using the adhesive sheets manufactured in the Examples and Comparative Examples, a laminate identical to that of Test Example 1 was prepared. Under the same active energy ray irradiation conditions as in Test Example 1, the laminate was irradiated with active energy rays (ultraviolet; UV) to cure the adhesive layer. Next, the adhesive layer cured by active energy rays was irradiated with ultraviolet light for 20 hours (light intensity: 7.2 kJ / cm²). 2 ) and 40 hours (light intensity: 14.4 kJ / cm) 2 In addition, the adhesive layer was irradiated with ultraviolet light under the same conditions as in Test Example 1. The adhesive layer thereafter was visually confirmed, and weather resistance was evaluated based on the following criteria. The results are shown in Table 2.

[0250] ◎...No needle-like cracks, bubbles, lifting, or peeling were produced.

[0251] ○…No needle-like cracks were produced, but some bubbles were produced.

[0252] ×… produced needle-like cracks.

[0253] [Experimental Example 9] (Evaluation of foaming resistance)

[0254] Release tab R2 was peeled off from the adhesive sheet manufactured in the examples and comparative examples, and the exposed adhesive layer was attached to the PC sheet side of a plastic sheet (manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC., product name "Iupilon.Sheet MR58U", thickness: 0.7 mm) on which polymethyl methacrylate was laminated on a polycarbonate (PC) sheet. Then, release tab R1 was peeled off from the adhesive layer to expose it, and a transparent conductive film (manufactured by OIKE & Co., Ltd., a laminate of PET film and ITO layer (ITO-PET film), total thickness 125 μm) was attached with its ITO layer side in contact with the adhesive layer. Afterwards, the mixture was autoclaved at 50°C and 0.5 MPa for 20 minutes.

[0255] The adhesive layer of the obtained laminate was irradiated with active energy rays (ultraviolet; UV) through the aforementioned transparent conductive film under the same conditions as in Experimental Example 1 to cure the adhesive layer. Afterwards, it was placed at normal pressure, 23°C, and 50% RH for 24 hours and used as a sample.

[0256] The obtained samples were then stored at 85°C and 85% RH for 72 hours. The interface between the adhesive layer and the substrate (plastic sheet) was then visually inspected, and foaming resistance was evaluated based on the following criteria. The results are shown in Table 2.

[0257] ○...No bubbles, floating, peeling, etc. were generated at all.

[0258] △… produces bubbles with a diameter of less than 1 mm, but does not produce buoyancy or peeling.

[0259] ×... The whole body produces bubbles, floats, peels off, etc.

[0260] [Table 1]

[0261]

[0262] [Table 2]

[0263]

[0264] As can be seen from Table 2, the adhesive sheet manufactured in the examples can suppress the generation of needle-like cracks even when exposed to high-intensity ultraviolet light for a long time (20 hours / 40 hours), and has excellent weather resistance.

[0265] Industrial applicability

[0266] The adhesive sheet of the present invention can be used, for example, to attach display body components such as protective panels to desired display body components during the manufacturing of a display body.

[0267] Explanation of reference numerals in the attached figures

[0268] 1: Adhesive sheet; 11: Adhesive layer; 12a: Release sheet; 12b: Release sheet; 2: Display body; 11': Cured adhesive layer; 21: First display body component; 22: First display body component; 3: Printed 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 The adhesive layer, after being cured by active energy rays, was irradiated with an irradiation of 100 mW / cm². 2 When the peak temperature of the loss tangent tanδ of the adhesive layer, which constitutes the adhesive layer, is set as Ta (°C) after 120 hours of ultraviolet light exposure, The value obtained by subtracting Tb from Ta is greater than 3.

2. The adhesive sheet according to claim 1, characterized in that, The adhesive comprising the adhesive layer has a gel content of 20% or more and 85% or less.

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

4. The adhesive sheet according to claim 1, characterized in that, The adhesive layer cured by active energy rays was irradiated with an irradiation of 100 mW / cm. 2 After 120 hours of exposure to ultraviolet light, the gel content 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 that constitutes the adhesive layer after curing by active energy rays is above 10,000 and below 250,000.

6. The adhesive sheet according to claim 1, characterized in that, The adhesive layer cured by active energy rays was irradiated with an irradiation of 100 mW / cm. 2 After 120 hours of exposure to ultraviolet light, the average peak molecular weight of the sol component of the adhesive that constitutes the adhesive layer is above 10,000 and below 200,000.

7. The adhesive sheet according to claim 1, characterized in that, The adhesive that forms 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, The adhesive layer cured by active energy rays was irradiated with an irradiation of 100 mW / cm. 2 After 120 hours of exposure to ultraviolet light, the storage modulus G' of the adhesive constituting the adhesive layer at 23°C is greater than 0.01 MPa and less than 2 MPa.

9. The adhesive sheet according to claim 1, characterized in that, The adhesive that forms 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, The adhesive layer cured by active energy rays was irradiated with an irradiation of 100 mW / cm. 2 After 120 hours of exposure to ultraviolet light, the storage modulus G' of the adhesive constituting the adhesive layer at -15°C is greater than 0.1 MPa and less than 1000 MPa.

11. The adhesive sheet according to claim 1, characterized in that, The adhesive that forms 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, The adhesive layer cured by active energy rays was irradiated with an irradiation of 100 mW / cm. 2 After 120 hours of exposure to ultraviolet light, the storage modulus G' of the adhesive constituting the adhesive layer at 100°C is greater than or equal to 0.0001 MPa and less than or equal to 1 MPa.

13. The adhesive sheet according to claim 1, characterized in that, 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, characterized in that, Both the one display component and the other display component are made of rigid board.

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