Adhesive, adhesive sheet, optical structure, and display body

Abstract

An adhesive according to the present invention contains an oxygen absorbent and is to be used for optical purposes. The adhesive is such that, when a laminate obtained by bonding two 7.0 cm squared soda-lime glass panels having a thickness of 1.1 mm by using a 250 μm-thick adhesive layer formed from the adhesive is placed in a 140°C atmosphere under persistent conditions for 100 hours of insertion, the absolute value of the ratio of b*2 to b*1 is 4.5 or less when b*1 is the chromaticity b*, as defined by the CIE 1976 L*a*b* color space, of the adhesive layer before the persistent conditions, and b*2 is the chromaticity b*, as defined by the CIE 1976 L*a*b* color space, of the adhesive layer at an end of the laminate after the persistent conditions. The adhesive enables suppression of yellowing at the ends of an optical member.

Description

Adhesive, adhesive sheet, optical structure and display

[0001] The present invention relates to an adhesive and an adhesive sheet, as well as an optical construction and a display obtained by using the same.

[0002] BACKGROUND ART In recent years, various mobile electronic devices such as mobile phones, smartphones, and tablet terminals are equipped with displays that use display modules having liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescence (organic EL) elements, etc.

[0003] In such displays, a protective panel is usually provided on the front side of the display module, and a gap is provided between the protective panel and the display module so that the deformed protective panel will not collide with the display module even if the protective panel is deformed by an external force.

[0004] However, when such a gap, i.e., an air layer, is present, there is a problem that the difference in refractive index between the protective panel and the air layer, and the difference in refractive index between the air layer and the display module, results in a large light reflection loss, which reduces the image quality of the display.

[0005] Therefore, it has been proposed to improve the image quality of a display by filling the gap between the protective panel and the display module with an adhesive layer (pressure-sensitive adhesive layer). For example, Patent Document 1 discloses a pressure-sensitive adhesive layer having a shear storage modulus (G') of 1.0 x 10 at 25°C and 1 Hz, which is used to fill the gap between the protective panel and the display module. ５ The document discloses a pressure-sensitive adhesive layer having a viscosity of 100 Pa or less and a gel fraction of 40% or more.

[0006] In recent years, high durability has been required, particularly in automotive applications. To meet this demand, for example, Patent Document 2 discloses an optical pressure-sensitive adhesive containing an acrylic copolymer (A) having a predetermined monomer composition and an isocyanate curing agent (B), in which the ratio G'2 / G'1 of the storage modulus G'1 at 175°C to the storage modulus G'2 at 225°C is specified.

[0007] JP 2010-97070 A JP 2023-102312 A

[0008] However, when a display obtained using the above adhesive layer is placed under high temperature for a long time, the adhesive layer may yellow at the edges of the display. The optical pressure-sensitive adhesive described in Patent Document 2 uses the degree of yellowing as a criterion for heat resistance, but the yellowing is not determined at the edges of the test piece.

[0009] The present invention has been made in consideration of these circumstances, and aims to provide an adhesive and adhesive sheet that can suppress yellowing at the ends of optical components, as well as an optical structure and display that can suppress yellowing of the adhesive layer at the ends.

[0010] In order to achieve the above-mentioned object, first, the present invention provides an adhesive for optical applications containing an oxygen absorber, characterized in that when a laminate formed by bonding two soda lime glass plates, each 1.1 mm thick and 7.0 cm square, with a 250 μm thick adhesive layer formed from the adhesive is placed under durability conditions in an atmosphere at 140°C for 100 hours, when the chromaticity b* defined by the CIE 1976 L*a*b* color system of the adhesive layer before the durability conditions is defined as b*1 and the chromaticity b* defined by the CIE 1976 L*a*b* color system of the adhesive layer at the end of the laminate after the durability conditions is defined as b*2, the absolute value of the ratio of b*2 to b*1 is 4.5 or less (Invention 1).

[0011] Secondly, the present invention provides an adhesive for optical applications containing an oxygen absorber, characterized in that when a laminate formed by bonding two 1.1 mm thick, 7.0 cm square soda lime glass plates together with a 250 μm thick adhesive layer formed from the adhesive is placed under durability conditions in an atmosphere at 140°C for 100 hours, when the chromaticity b* defined by the CIE 1976 L*a*b* color system of the adhesive layer at the end of the laminate after the durability conditions is b*2, the absolute value of b*2 is less than 2.0 (Invention 2).

[0012] Third, the present invention provides an adhesive for optical applications containing an oxygen absorber, characterized in that when a laminate formed by bonding two 1.1 mm thick, 7.0 cm square soda lime glass plates together with a 250 μm thick adhesive layer formed from the adhesive is placed under durability conditions in an atmosphere at 140°C for 100 hours, when the chromaticity b* defined by the CIE 1976 L*a*b* color system of the adhesive layer at the end of the laminate after the durability conditions is defined as b*2 and the chromaticity b* defined by the CIE 1976 L*a*b* color system of the adhesive layer at the center of the laminate after the durability conditions is defined as b*3, the absolute value of the ratio of b*2 to b*3 is 2.5 or less (Invention 3).

[0013] The adhesives according to the above inventions (Inventions 1 to 3) contain an oxygen absorber, which inactivates oxygen in the adhesive and suppresses thermal oxidative degradation of the adhesive. The edges of optical components are particularly susceptible to exposure to oxygen and thermal oxidative degradation. However, the action of the oxygen absorber effectively suppresses thermal oxidative degradation even at the edges of optical components. As a result, yellowing of the edges of optical components bonded via an adhesive layer using the adhesive can be suppressed. Specifically, when the above laminate is produced and subjected to the durability conditions described above, the yellowing of the edges after the durability conditions can be suppressed compared to the adhesive layer before the durability conditions (Invention 1), the degree of yellowing of the edges after the durability conditions can be reduced compared to the center (Invention 2), and the yellowing of the edges after the durability conditions can be suppressed compared to the center (Invention 3).

[0014] In the above inventions (Inventions 1 to 3), the oxygen absorber is preferably a compound represented by the following general formula (I) (Invention 4). (In general formula (I), X and Y each independently represent a chalcogen atom, and R １ , R ２ , R ７ , and R ８ each independently represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group; R ３ , R ４ , R ５ , and R６ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. J represents a linking group made of an aliphatic hydrocarbon having 3 to 15 carbon atoms, and any carbon atom in the linking group may be substituted with an oxygen atom, and the linking group may have at least one substituent selected from the group consisting of a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, and an alkenyloxy group having 2 to 5 carbon atoms. n is an integer from 1 to 5. However, Y, R ５ , R ６ , R ７ , and R ８ When there are a plurality of groups, they may be different atoms or groups.

[0015] In the above inventions (Inventions 1 to 4), the oxygen absorber is preferably a compound represented by the following general formula (II) (Invention 5). (In general formula (II), R ９ represents a hydrogen atom or a methyl group, R １０ represents a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, or an alkenyloxy group having 2 to 5 carbon atoms. １１ , R １２ , R １３ , and R １４ each independently represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group.

[0016] In the above inventions (Inventions 1 to 5), the oxygen absorber is preferably a compound represented by the following formula (III) (Invention 6).

[0017] The adhesive according to the above inventions (Inventions 1 to 6) is preferably an acrylic adhesive (Invention 7).

[0018] In the above inventions (Inventions 1 to 7), the main adhesive agent is preferably a (meth)acrylic acid ester polymer or a crosslinked product thereof (Invention 8).

[0019] The adhesive according to the above inventions (Inventions 1 to 8) is preferably an active energy ray-curable adhesive (Invention 9).

[0020] Fourth, the present invention provides an adhesive sheet having an adhesive layer for bonding two members together, wherein at least one of the members is an optical member, and the adhesive layer is made of any of the adhesives (Inventions 1 to 9) (Invention 10).

[0021] In the above invention (Invention 10), it is preferable that the adhesive sheet has two release sheets, and the adhesive layer is sandwiched between the release sheets so as to contact the release surfaces of the two release sheets (Invention 11).

[0022] Fifth, the present invention provides an optical construct comprising at least two members bonded together by an adhesive layer, wherein at least one of the members is an optical member, and the adhesive layer is formed from any of the adhesives (Inventions 1 to 9) (Invention 12).

[0023] Sixth, the present invention provides a display comprising one display component, another display component, and an adhesive layer for bonding the one display component and the other display component to each other, wherein the adhesive layer is formed from the adhesive layer of the adhesive sheet (Inventions 10 and 11) (Invention 13).

[0024] In the above invention (Invention 13), it is preferable that both the one display member and the other display member are hard plates (Invention 14).

[0025] The adhesive and adhesive sheet according to the present invention can suppress yellowing at the edges of an optical component, and the optical construction and display according to the present invention can suppress yellowing of the adhesive layer at the edges.

[0026] 1 is a cross-sectional view of an adhesive sheet according to one embodiment of the present invention;

[0027] Hereinafter, an embodiment of the present invention will be described. [Adhesive] The adhesive according to one embodiment of the present invention is used for optical applications and preferably contains an oxygen absorber. When a laminate formed by bonding two 1.1 mm thick, 7.0 cm square soda lime glass plates with a 250 μm thick adhesive layer formed from the adhesive according to this embodiment is placed under durability conditions in an atmosphere at 140° C. for 100 hours, the chromaticity b* of the adhesive layer before the durability conditions, as defined by the CIE 1976 L*a*b* color system, is defined as b*1, and the chromaticity b* of the adhesive layer at the edge of the laminate after the durability conditions is defined as b*2. When the chromaticity b* defined by the CIE 1976 L*a*b* color system is b*2 and the chromaticity b* defined by the CIE 1976 L*a*b* color system of the adhesive layer at the center of the laminate after the durability conditions is b*3, first, it is preferable that the absolute value of the ratio of b*2 to b*1 (b*2 / b*1) is 4.5 or less, second, it is preferable that the absolute value of b*2 is less than 2.0, and third, it is preferable that the absolute value of the ratio of b*2 to b*3 (b*2 / b*3) is 2.5 or less. The method for measuring chromaticity b* in this specification is as shown in the test examples described later.

[0028] Here, the "adhesive layer" in the "laminate formed by lamination with an adhesive layer" refers to an adhesive layer in the same state as the adhesive layer of the adhesive sheet if the adhesive is not active energy ray-curable, and refers to an adhesive layer cured by active energy ray irradiation after lamination if the adhesive layer is active energy ray-curable. The "adhesive layer after active energy ray curing" refers to an adhesive layer that has been completely cured by active energy ray irradiation. Specifically, this refers to an adhesive layer in which the rate of increase in gel fraction of the adhesive layer is 10% or less, and particularly refers to an adhesive layer in which the rate of increase is 5% or less, when the adhesive layer after active energy ray curing is further irradiated with active energy ray at the same dose (light amount) as when the active energy ray cured adhesive layer was cured with the active energy ray.

[0029] When the adhesive according to the present embodiment contains an oxygen absorber, the oxygen absorber inactivates oxygen in the adhesive, thereby suppressing thermal oxidative degradation of the adhesive. The edges of optical components are particularly susceptible to exposure to oxygen and thermal oxidative degradation. However, the action of the oxygen absorber effectively suppresses thermal oxidative degradation even at the edges of the optical components. As a result, yellowing of the edges of optical components bonded via an adhesive layer using the adhesive can be suppressed. Specifically, when the above-described laminate is produced and subjected to the durability conditions described above, it is possible to suppress yellowing of the edges after the durability conditions relative to the adhesive layer before the durability conditions, to reduce the degree of yellowing of the edges after the durability conditions, and to suppress yellowing of the edges relative to the center after the durability conditions.

[0030] Here, the term "edge of the laminate" in this specification refers to a circular area with a radius of 2 mm, with its center point located 3 mm inward from the center end face of any one side of the laminate in plan view. Also, the term "center of the laminate" in this specification refers to a 10 mm square area with the same center point as the center point of the laminate in plan view.

[0031] From the viewpoint of suppressing edge yellowing, the absolute value of b*2 / b*1 is preferably 4.5 or less, more preferably 3.0 or less, particularly preferably 2.5 or less, and even more preferably 2.0 or less, as described above. The lower limit of the absolute value of b*2 / b*1 is most preferably 1, but is also preferably 1.1 or more, particularly preferably 1.2 or more.

[0032] From the viewpoint of suppressing edge yellowing, the absolute value of b*2 is preferably less than 2.0, more preferably 1.6 or less, particularly preferably 1.2 or less, and even more preferably 1.0 or less, as described above. The lower limit of the absolute value of b*2 is also preferably 0 or more, more preferably 0.1 or more, particularly preferably 0.2 or more, and even more preferably 0.3 or more.

[0033] From the viewpoint of suppressing edge yellowing, the absolute value of b*2 / b*3 is preferably 2.5 or less, more preferably 2.2 or less, particularly preferably 2.0 or less, and even more preferably 1.8 or less, as described above. The lower limit of the absolute value of b*2 / b*1 is most preferably 1, but is also preferably 1.1 or more, particularly preferably 1.2 or more.

[0034] From the viewpoint of making the adhesive layer as colorless and transparent as possible, b*1 is preferably −10 to 10, more preferably −5 to 5, particularly preferably −1 to 1, and further preferably −0.5 to 0.5.

[0035] Furthermore, from the viewpoint of making the adhesive layer as colorless and transparent as possible and of making it easier to satisfy the above-mentioned physical properties, b*3 is preferably −10 to 10, more preferably −5 to 5, particularly preferably −1 to 1, and further preferably −0.5 to 0.5.

[0036] The oxygen absorber in this embodiment is preferably a compound represented by the following general formula (I) (hereinafter, sometimes referred to as "compound Q"), from the viewpoint of easily satisfying the above-mentioned physical properties. (In general formula (I), X and Y each independently represent a chalcogen atom, and R １ , R ２ , R ７ , and R ８ each independently represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group; R ３ , R ４ , R ５ , and R ６each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. J represents a linking group made of an aliphatic hydrocarbon having 3 to 15 carbon atoms, and any carbon atom in the linking group may be substituted with an oxygen atom, and the linking group may have at least one substituent selected from the group consisting of a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, and an alkenyloxy group having 2 to 5 carbon atoms. n is an integer from 1 to 5. However, Y, R ５ , R ６ , R ７ , and R ８ When there are a plurality of groups, they may be different atoms or groups.

[0037] In general formula (I), n is preferably 1 to 4, more preferably 1 or 2, from the viewpoint of easy availability of raw materials.

[0038] In general formula (I), X and Y are preferably an oxygen atom or a sulfur atom, more preferably an oxygen atom, from the viewpoint of ease of production of compound Q and of improving oxygen absorption performance.

[0039] R in general formula (I) １ , R ２ , R ７ , and R ８ Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0040] R in general formula (I) １ , R ２ , R ７ , and R ８ Examples of the alkenyl group having 2 to 6 carbon atoms include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a pentenyl group, a heptenyl group, a hexenyl group, an iso-3-hexenyl group, and a cyclohexenyl group.

[0041] R in general formula (I)１ , R ２ , R ７ , and R ８ Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0042] R in general formula (I) １ , R ２ , R ７ , and R ８ Examples of the aralkyl group include a benzyl group, a 2-phenylethyl group, a 2-naphthylethyl group, and a diphenylmethyl group.

[0043] Among the above, R １ , R ２ , R ７ , and R ８ are each independently preferably either an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group.

[0044] R in general formula (I) ３ , R ４ , R ５ , and R ６ The alkyl group having 1 to 6 carbon atoms, the alkenyl group having 2 to 6 carbon atoms, the aryl group, and the aralkyl group are the same as those in the above R １ , R ２ , R ７ , and R ８ Examples of the alkyl group include the alkyl group having 2 to 6 carbon atoms, the alkenyl group having 2 to 6 carbon atoms, the aryl group, and the aralkyl group.

[0045] Among the above, R ３ , R ４ , R ５ , and R ６ are each independently preferably any one of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, and an aryl group, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom. ３ and R ６ are preferably all hydrogen atoms, and R ４ and R５ are each preferably independently a hydrogen atom or a methyl group, and more preferably all are a hydrogen atom.

[0046] In general formula (I), the linking group of J is preferably an aliphatic hydrocarbon group having 3 to 10 carbon atoms, and more preferably an aliphatic hydrocarbon group having 3 to 5 carbon atoms, from the viewpoint of ease of handling of compound Q. Examples of styryloxy groups which are optional substituents on the linking group of J include 4-styryloxy groups. Furthermore, the alkenyloxy group having 2 to 5 carbon atoms which is optional substituent on the linking group of J may be a vinyloxy group having 2 to 5 carbon atoms. From the viewpoint of improving the oxygen absorption performance of compound Q, the optional substituent on the linking group of J is preferably a hydroxyl group or a (meth)acryloyloxy group.

[0047] As a specific example of the linking group of J, a linking group represented by the following general formula (J-1) is more preferred from the viewpoint of improving the oxygen absorption performance of compound Q. In addition, "*" in general formula (J-1) indicates the point of attachment to X or Y. In the above general formula (J-1), R ９ represents a hydrogen atom or a methyl group, and is preferably a hydrogen atom. １０ represents any one of a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, and an alkenyloxy group having 2 to 5 carbon atoms, and is preferably a hydroxyl group or a (meth)acryloyloxy group. The alkenyloxy group having 2 to 5 carbon atoms may be a vinyloxy group having 2 to 5 carbon atoms.

[0048] As a specific example of the compound Q, from the viewpoint of oxygen absorption performance and hence the viewpoint of easily satisfying the physical properties related to b*, a compound represented by the following general formula (II) is preferred. (In general formula (II), R ９ represents a hydrogen atom or a methyl group, R １０ represents a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, or an alkenyloxy group having 2 to 5 carbon atoms. １１ , R １２ , R １３ , and R １４each independently represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group.

[0049] R in general formula (II) １０ is preferably a hydroxyl group or a (meth)acryloyloxy group. １０ The alkenyloxy group having 2 to 5 carbon atoms may be a vinyloxy group having 2 to 5 carbon atoms.

[0050] R in general formula (II) １１ , R １２ , R １３ , and R １４ The preferred embodiments of the above are R １ , R ２ , R ７ , and R ８ is the same as

[0051] The oxygen absorber in this embodiment is particularly preferably a compound represented by the following formula (III) (hereinafter sometimes referred to as "compound S").

[0052] The method for producing compound Q is not particularly limited, and compound Q can be produced by using a known method or by combining and applying known methods. As an example, compound S can be produced by reacting 3-methyl-2-buten-1-ol with a compound capable of forming linking group J, such as epichlorohydrin, in the presence of an alkali such as potassium hydroxide. As reaction conditions, from the viewpoint of ensuring a sufficient reaction, it is preferable to stir the mixture at a temperature of about 25 to 70°C for about 2 to 10 hours.

[0053] The content of the oxygen absorber in the adhesive according to this embodiment is preferably 0.01 to 30% by mass, more preferably 0.05 to 25% by mass, particularly preferably 0.1 to 20% by mass, even more preferably 0.5 to 15% by mass, and of these, preferably 0.8 to 10% by mass. This allows edge yellowing to be effectively suppressed. From the viewpoint of more effectively suppressing edge yellowing, the lower limit of the oxygen absorber content is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more. On the other hand, from the viewpoint of blister resistance, the upper limit of the oxygen absorber content is preferably 8% by mass or less, more preferably 6% by mass or less, particularly preferably 4% by mass or less, and even more preferably 2% by mass or less.

[0054] The adhesive according to this embodiment is preferably a pressure-sensitive adhesive (adhesive), but is not limited to this. The type of adhesive according to this embodiment may be any of an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, etc. Furthermore, the adhesive may be any of an emulsion type, a solvent type, or a solventless type, and may be either a crosslinked type or a non-crosslinked type. Among these, an acrylic adhesive is preferred because of its excellent pressure-sensitive adhesive properties, optical properties, etc.

[0055] The acrylic adhesive may be an active energy ray-curable adhesive, an active energy ray-non-curable adhesive, a crosslinkable adhesive, a non-crosslinkable adhesive, or a combination thereof. Among these, an active energy ray-curable acrylic adhesive is preferred from the viewpoint of easily achieving excellent step conformability and blister resistance.

[0056] From the viewpoint of film-forming properties, the adhesive according to this embodiment preferably contains a (meth)acrylic acid ester polymer as the main adhesive agent, and particularly preferably contains a crosslinked (meth)acrylic acid ester polymer. The adhesive according to this embodiment also preferably contains the main adhesive agent and an active energy ray-curable component. The crosslinked (meth)acrylic acid ester polymer is preferably a crosslinked (meth)acrylic acid ester polymer and a crosslinking agent.

[0057] Specifically, the adhesive according to this embodiment is preferably obtained by crosslinking (preferably thermally crosslinking) an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), an oxygen absorber (C), and, if desired, an active energy ray-curable component (D). In this specification, (meth)acrylic acid refers to both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" also includes the concept of "copolymer."

[0058] (1) Components (1-1) (Meth)acrylic acid ester polymer (A) The (meth)acrylic acid ester polymer (A) preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester. This allows the polymer to exhibit good pressure-sensitive adhesive properties. Note that the (meth)acrylic acid alkyl ester does not include the hard monomers described below.

[0059] From the viewpoint of pressure-sensitive adhesiveness, the (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group containing 1 to 20 carbon atoms. Examples of (meth)acrylic acid alkyl esters having an alkyl group containing 1 to 20 carbon atoms include methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. These may be used alone or in combination of two or more. Among the above, from the viewpoint of further improving pressure-sensitive adhesiveness, (meth)acrylic acid esters in which the alkyl group has 1 to 14 carbon atoms are preferred, (meth)acrylic acid esters in which the alkyl group has 2 to 10 carbon atoms are more preferred, and (meth)acrylic acid esters in which the alkyl group has 3 to 8 carbon atoms are particularly preferred. Specifically, for example, methyl acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, or isooctyl (meth)acrylate are preferred, n-butyl acrylate or 2-ethylhexyl acrylate are particularly preferred, and 2-ethylhexyl acrylate is even more preferred.

[0060] From the viewpoint of imparting pressure-sensitive adhesiveness, the (meth)acrylic acid ester polymer (A) preferably contains 30 to 99 mass %, more preferably 40 to 92 mass %, particularly preferably 50 to 86 mass %, even more preferably 55 to 80 mass %, and of these, preferably 60 to 75 mass % of structural units derived from a (meth)acrylic acid alkyl ester. This makes it easier for the resulting adhesive to satisfy the physical properties described below and also results in excellent blister resistance and unevenness conformability.

[0061] The (meth)acrylic acid ester polymer (A) preferably contains a structural unit derived from a reactive functional group-containing monomer, whereby the reactive functional group derived from the reactive functional group-containing monomer reacts with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), thereby obtaining an adhesive having the desired cohesive strength.

[0062] Preferred examples of the reactive group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), etc. Among these, a hydroxyl group-containing monomer or a carboxyl group-containing monomer, which has excellent reactivity with the crosslinking agent (B), is preferred.

[0063] Examples of hydroxyl group-containing monomers include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate is preferred from the viewpoints of reactivity with the crosslinking agent (B) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

[0064] Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid or methacrylic acid is preferred, and acrylic acid is particularly preferred, from the viewpoint of reactivity with the crosslinking agent (B) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

[0065] From the viewpoint of cohesive strength, the content of the structural unit derived from the reactive functional group-containing monomer in the (meth)acrylic acid ester polymer (A) is preferably 1 to 40 mass%, more preferably 3 to 34 mass%, particularly preferably 6 to 28 mass%, even more preferably 9 to 24 mass%, and of these, preferably 12 to 20 mass%.

[0066] The (meth)acrylic acid ester polymer (A) also preferably contains a structural unit derived from a hard monomer having a glass transition temperature (Tg) of 70°C or higher as a homopolymer. The aforementioned reactive functional group-containing monomers are excluded from the hard monomer. By containing a structural unit derived from the hard monomer in the (meth)acrylic acid ester polymer (A), the resulting adhesive has improved cohesive strength, making it easier to achieve excellent step-following ability and blister resistance. In particular, when the (meth)acrylic acid ester polymer (A) contains a structural unit derived from a (meth)acrylic acid ester having an alkyl group with 5 to 8 carbon atoms, the cohesive strength tends to be low, so it is preferable to contain a structural unit derived from the hard monomer. The glass transition temperature (Tg) of the hard monomer as a homopolymer is preferably 75 to 200°C, particularly preferably 80 to 180°C, and even more preferably 90 to 150°C.

[0067] Examples of the hard monomer include methyl methacrylate (Tg 105° C.), isobornyl acrylate (Tg 94° C.), isobornyl methacrylate (Tg 180° C.), adamantyl acrylate (Tg 115° C.), adamantyl methacrylate (Tg 141° C.), etc. These may be used alone or in combination of two or more.

[0068] Among the above hard monomers, from the viewpoint of better exhibiting the performance of the hard monomer while preventing adverse effects on other properties such as pressure-sensitive adhesiveness and transparency, methyl methacrylate or isobornyl acrylate is more preferred, and isobornyl acrylate, which is a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer), is particularly preferred.

[0069] When the (meth)acrylic acid ester polymer (A) contains the structural unit derived from the hard monomer, the content thereof is preferably 1 to 30 mass%, more preferably 4 to 25 mass%, particularly preferably 8 to 20 mass%, and even more preferably 10 to 16 mass%, from the viewpoints of cohesive strength, step-following ability, and blister resistance.

[0070] The (meth)acrylic acid ester polymer (A) also preferably contains a structural unit derived from a monomer having a nitrogen atom in the molecule (nitrogen atom-containing monomer). In particular, when an alicyclic structure-containing monomer, particularly isobornyl acrylate, is used as the hard monomer, it is preferable to contain a structural unit derived from a nitrogen atom-containing monomer. The presence of a structural unit derived from a nitrogen atom-containing monomer can impart a predetermined polarity to the adhesive and improve adhesion.

[0071] As the nitrogen atom-containing monomer, a monomer having a nitrogen-containing heterocycle is preferred from the viewpoint of imparting appropriate rigidity to the (meth)acrylic acid ester polymer (A). Also, from the viewpoint of increasing the degree of freedom of the nitrogen atom-containing monomer-derived portion in the higher-order structure of the resulting adhesive, it is preferred that the nitrogen atom-containing monomer does not contain a reactive unsaturated double bond group other than one polymerizable group used in polymerization to form the (meth)acrylic acid ester polymer (A).

[0072] 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, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide. Among these, N-(meth)acryloylmorpholine, which exhibits superior adhesive strength, is preferred, and N-acryloylmorpholine is particularly preferred. These may be used alone or in combination of two or more.

[0073] When the (meth)acrylic acid ester polymer (A) contains a structural unit derived from a nitrogen atom-containing monomer, the content thereof is preferably 1 to 20 mass%, more preferably 2 to 16 mass%, particularly preferably 3 to 12 mass%, and even more preferably 4 to 8 mass%, from the viewpoint of better adhesiveness.

[0074] The (meth)acrylic acid ester polymer (A) may contain structural units derived from other monomers, if desired. The other monomers are preferably monomers that do not contain reactive functional groups, so as not to interfere with the action of the reactive group-containing monomer. Examples of such other monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

[0075] The (meth)acrylic acid ester polymer (A) may be a polymer obtained by solution polymerization, a polymer obtained without a solvent, or an emulsion polymerization. Among these, a solution polymer obtained by solution polymerization is preferred. By using a solution polymer, a high molecular weight polymer can be easily obtained, and the resulting adhesive can easily satisfy the physical properties described below, and can easily achieve better step conformability and blister resistance.

[0076] The polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

[0077] The weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 100,000 to 3,000,000, more preferably 200,000 to 2,400,000, particularly preferably 300,000 to 1,800,000, even more preferably 400,000 to 1,200,000, and most preferably 450,000 to 800,000. This makes it easier for the resulting adhesive to satisfy the physical properties described below and to achieve better step conformability and blister resistance. Note that the weight-average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0078] In the adhesive composition P, the (meth)acrylic acid ester polymer (A) may be used alone or in combination of two or more.

[0079] The content of the (meth)acrylic acid ester polymer (A) in the adhesive composition P according to this embodiment is preferably 70 to 99.9% by mass, more preferably 75 to 99% by mass, and particularly preferably 80 to 96% by mass, from the viewpoint of excellent film-forming properties and pressure-sensitive adhesiveness. From the viewpoint of excellent blister resistance and conformability to unevenness, it is even more preferably 82 to 94% by mass, and of these, 86 to 92% by mass is preferred.

[0080] (1-2) Crosslinking Agent (B) The crosslinking agent (B) crosslinks the (meth)acrylic acid ester polymer (A) by heating the adhesive composition P, thereby enabling the formation of a favorable crosslinked structure having a three-dimensional network structure, thereby obtaining an adhesive having a predetermined cohesive strength.

[0081] The crosslinking agent (B) may be any agent that reacts with the reactive functional group (hydroxyl group or carboxyl group) of the (meth)acrylic acid ester polymer (A), and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. When the (meth)acrylic acid ester polymer (A) contains a structural unit derived from a hydroxyl group-containing monomer, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with hydroxyl groups as the crosslinking agent (B). The crosslinking agent (B) may be used alone or in combination of two or more.

[0082] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate, and xylylene diisocyanate (XDI), aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret and isocyanurate forms thereof, as well as adducts thereof that are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate or trimethylolpropane-modified xylylene diisocyanate, are preferred from the viewpoint of reactivity with hydroxyl groups. From the viewpoint of seasoning, trimethylolpropane-modified tolylene diisocyanate is particularly preferred.

[0083] The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 10 parts by mass, more preferably 0.04 to 5 parts by mass, particularly preferably 0.08 to 1 part by mass, even more preferably 0.1 to 0.6 parts by mass, and of these, preferably 0.12 to 0.3 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). This makes the cohesive strength more suitable, making it easier for the resulting adhesive to satisfy the physical properties described below and to achieve excellent step-following ability and blister resistance.

[0084] (1-3) Oxygen Absorber (C) The oxygen absorber (C) used in the adhesive composition P is the oxygen absorber described above, and its specific components and content (mass%) in the adhesive are as described above. The amount of the oxygen absorber (C) in the adhesive composition P relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A) is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 25 parts by mass, particularly preferably 0.5 to 20 parts by mass, even more preferably 1 to 16 parts by mass, and especially preferably 2 to 12 parts by mass. This more effectively suppresses edge yellowing. On the other hand, from the viewpoint of blister resistance, the upper limit of the amount of the oxygen absorber (C) is preferably 9 parts by mass or less, more preferably 6 parts by mass or less, particularly preferably 4 parts by mass or less, and even more preferably 2 parts by mass or less.

[0085] (1-4) Active energy ray-curable component (D) When the adhesive composition P contains the active energy ray-curable component (D), the resulting adhesive is active energy ray-curable. The active energy ray-cured adhesive layer can easily achieve excellent step conformability and blister resistance by active energy ray curing after lamination.

[0086] The active energy ray-curable component (D) is not particularly limited as long as it is a component that can be cured by irradiation with active energy rays without impairing adhesiveness, and may be any of a monomer, an oligomer, or a polymer, or a mixture thereof. Among these, polyfunctional acrylate-based monomers are preferred, as they can easily achieve better step conformability and blister resistance.

[0087] Examples of polyfunctional acrylate monomers include bifunctional monomers such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; trifunctional types such as diglycerol tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional types such as propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate; tetrafunctional types such as diglycerol tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional types such as propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional types such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. Among the above, from the viewpoint of the step-following ability and blister resistance of the resulting adhesive, polyfunctional acrylate monomers containing an isocyanurate structure in the molecule, such as di(acryloxyethyl)isocyanurate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate, are preferred, polyfunctional acrylate monomers that are trifunctional or higher and contain an isocyanurate structure in the molecule are more preferred, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate is particularly preferred.These may be used alone or in combination of two or more. Furthermore, from the viewpoint of making the resulting adhesive more likely to exhibit the desired viscoelasticity, the polyfunctional acrylate monomer preferably has a molecular weight of less than 20,000, more preferably less than 10,000, and particularly preferably less than 5,000. Furthermore, from the viewpoint of compatibility with the (meth)acrylic acid ester polymer (A) and making the resulting adhesive more likely to satisfy the physical properties described below, a polyfunctional acrylate monomer preferably has a molecular weight of less than 1,000.

[0088] When the adhesive composition P contains an active energy ray-curable component (D), the content of the active energy ray-curable component (D) is preferably 0.1 to 40 parts by mass, more preferably 1 to 30 parts by mass, particularly preferably 2 to 20 parts by mass, even more preferably 3 to 15 parts by mass, and of these, preferably 4 to 10 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). This makes it easier for the resulting adhesive to satisfy the physical properties described below and to achieve better step-following ability and blister resistance.

[0089] (1-5) Photopolymerization initiator (E) When the adhesive composition P contains an active energy ray-curable component (D) and ultraviolet light is used as the active energy ray, the adhesive composition P preferably contains a photopolymerization initiator (E), which allows the active energy ray-curable component (D) to be cured efficiently and also reduces the polymerization / curing time and the ultraviolet light irradiation dose.

[0090] Examples of the photopolymerization initiator (E) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4 Examples of suitable benzoxanthraquinones include 2-methyl-2-hydroxybenzoyl-1-methyl-1-methyl-2-methyl-1 ...

[0091] Among the above, from the viewpoint of easily obtaining better conformability to unevenness and blister resistance, phosphine-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, or a mixture of 1-hydroxycyclohexyl phenyl ketone and benzophenone are preferred, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide is particularly preferred.

[0092] The content of the photopolymerization initiator (E) in the adhesive composition P is preferably 1 to 30 parts by mass, particularly preferably 5 to 22 parts by mass, and even more preferably 8 to 16 parts by mass, per 100 parts by mass of the active energy ray-curable component (D). This makes it easier for the resulting adhesive to satisfy the physical properties described below and to achieve better step-conforming ability and blister resistance.

[0093] (1-6) Silane Coupling Agent (F) The adhesive composition P preferably further contains a silane coupling agent (F). This improves the adhesion of the resulting adhesive to a glass member when the adherend is a glass member. Furthermore, even when the adherend is a plastic plate, the resulting adhesive improves the adhesion to the plastic plate. This makes it easier for the resulting adhesive to satisfy the physical properties described below, and also makes it easier to obtain better step conformability and blister resistance.

[0094] The silane coupling agent (F) is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the (meth)acrylic acid ester polymer (A) and has optical transparency.

[0095] Examples of such silane coupling agents (F) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; Examples of suitable silicon compounds include hydroxyl group-containing silicon compounds, amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane, as well as condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used alone or in combination of two or more.

[0096] The content of the silane coupling agent (F) in the adhesive composition P is preferably 0.01 to 10 parts by mass, more preferably 0.04 to 5 parts by mass, particularly preferably 0.08 to 1 part by mass, even more preferably 0.12 to 0.7 parts by mass, and especially preferably 0.15 to 0.4 parts by mass, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). This allows the resulting adhesive to exhibit excellent adhesion and to have even better step-following ability and blister resistance. Furthermore, the resulting adhesive is more likely to satisfy the physical properties described below.

[0097] (1-7) Various Additives The adhesive composition P may contain, if desired, various additives that are commonly used in acrylic adhesives, such as ultraviolet absorbers, light stabilizers, antistatic agents, tackifiers, colorants, infrared absorbers, rust inhibitors, antioxidants, light stabilizers, softeners, fillers, and refractive index adjusters.

[0098] (2) Production of Adhesive Composition The adhesive composition P can be produced by producing a (meth)acrylic acid ester polymer (A), mixing the obtained (meth)acrylic acid ester polymer (A) with a crosslinking agent (B) and an oxygen absorber (C), and, if desired, adding an active energy ray-curable component (D), a photopolymerization initiator (E), a silane coupling agent (F), an additive, etc.

[0099] The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a conventional radical polymerization method. The polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. However, the present invention is not limited thereto, and the polymerization may be carried out in the absence of a solvent.

[0100] Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of these may be used in combination. Examples of polymerization initiators include azo compounds and organic peroxides, and two or more of these may be used in combination. In the polymerization step, the weight-average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

[0101] Once the (meth)acrylic acid ester polymer (A) is obtained, the crosslinking agent (B), the oxygen absorber (C), and, if desired, the active energy ray-curable component (D), the photopolymerization initiator (E), the silane coupling agent (F), additives, the dilution solvent, etc. are added to the solution of the (meth)acrylic acid ester polymer (A), and the mixture is thoroughly mixed to obtain an adhesive composition P (coating solution) diluted with a solvent. Note that, when any of the above components is used in a solid state, or when precipitation occurs when mixed with other components in an undiluted state, that component may be dissolved or diluted alone in a dilution solvent before being mixed with other components.

[0102] Examples of the dilution solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.

[0103] The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are within a range that allows coating, and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted so that the concentration is 10 to 60 mass %. Note that the addition of a dilution solvent or the like is not a necessary condition for obtaining the coating solution, and as long as the adhesive composition P has a viscosity that allows coating, the addition of a dilution solvent is not necessary. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) is used as the dilution solvent.

[0104] (3) Production of Adhesive The adhesive composition P described above is applied to a desired object and then crosslinked to obtain an adhesive (adhesive layer).

[0105] The adhesive composition P can be crosslinked by a heat treatment. This heat treatment can also serve as a drying treatment after application of the adhesive composition P. The heating temperature for the heat treatment is preferably 50 to 150°C, and more preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.

[0106] After the heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (e.g., 23°C, 50% RH), if necessary. If this curing period is required, the adhesive is formed after the curing period has elapsed; if no curing period is required, the adhesive is formed after the heat treatment has been completed. In this specification, "relative humidity α%" may also be expressed as "α% RH" (RH; Relative humidity).

[0107] By the above heat treatment (and curing), a crosslinked product of the (meth)acrylic acid ester polymer (A) crosslinked by the crosslinking agent (B) is formed.

[0108] (4) Physical Properties (Gel Fraction) The gel fraction of the adhesive according to this embodiment is preferably 20 to 100%, more preferably 25 to 90%, particularly preferably 30 to 80%, even more preferably 35 to 80%, and most preferably 41 to 70%. This makes it easy to obtain good pressure-sensitive adhesion when applied to an adherend, as well as good blister resistance and step-conforming properties. The method for measuring the gel fraction in this specification is as shown in the test examples described below.

[0109] When the adhesive according to this embodiment is active energy ray-curable, the gel fraction of the adhesive after active energy ray curing is preferably 30 to 100%, more preferably 40 to 90%, particularly preferably 45 to 80%, even more preferably 50 to 70%, and of these, preferably 55 to 64%. This makes it easy to obtain good adhesive strength after attachment to an adherend, as well as good blister resistance and step-conforming ability.

[0110] Here, when the adhesive according to the present embodiment contains a crosslinking agent (B), it is preferable to provide a curing period, and the gel fraction (gel fraction G1) of the adhesive according to the present embodiment, 7 days after the formation of a coating layer, is preferably 20 to 100%, more preferably 25 to 90%, particularly preferably 30 to 80%, even more preferably 35 to 70%, and of these, preferably 41 to 60%.

[0111] Furthermore, the gel fraction (gel fraction G2) of the adhesive according to this embodiment, 14 days after the formation of a coating layer of the adhesive, is preferably 20 to 100%, more preferably 25 to 90%, particularly preferably 30 to 80%, even more preferably 35 to 70%, and of these, preferably 42 to 60%.

[0112] Furthermore, the difference (G2-G1; points) obtained by subtracting the gel fraction G1 (%) from the gel fraction G2 (%) is preferably 15 points or less, more preferably 10 points or less, even more preferably 7 points or less, particularly preferably 4 points or less, even more preferably 2 points or less, and most preferably 1 point or less. When the difference between the gel fraction G2 and the gel fraction G1 is small, it can be said that the seasoning is excellent.

[0113] When the adhesive according to the present embodiment is active energy ray-curable, the gel fraction (gel fraction G1c) of the adhesive cured with active energy rays 7 days after the formation of a coating layer of the adhesive is preferably 30 to 100%, more preferably 40 to 90%, particularly preferably 45 to 80%, even more preferably 50 to 70%, and of these, preferably 55 to 64%.

[0114] Furthermore, the gel fraction (gel fraction G2c) of the adhesive cured with active energy rays 14 days after the formation of the coating layer of the adhesive is preferably 30 to 100%, more preferably 40 to 90%, particularly preferably 45 to 80%, even more preferably 50 to 70%, and of these, preferably 55 to 64%.

[0115] [Adhesive Sheet] The adhesive sheet according to this embodiment has an adhesive layer for bonding two members together. At least one of the members is an optical member. The specific configuration of the adhesive sheet and the optical member will be described later.

[0116] The adhesive layer in the adhesive sheet according to this embodiment is made of the adhesive according to the embodiment described above.

[0117] The thickness of the adhesive layer of the adhesive sheet according to this embodiment (a value measured in accordance with JIS K7130) is preferably 1 to 1000 μm, more preferably 10 to 600 μm, and particularly preferably 20 to 300 μm, from the viewpoint of adhesive strength, conformability to unevenness, and blister resistance; and from the viewpoint of making edge yellowing less of a problem, it is preferably 30 to 150 μm, even more preferably 40 to 100 μm, and of these, 45 to 70 μm is preferred.

[0118] (1) Physical Properties (1-1) Storage Modulus G' The storage modulus G' at 23°C of the adhesive constituting the adhesive layer after lamination in this embodiment is preferably 0.001 to 10 MPa, more preferably 0.010 to 1 MPa, more preferably 0.020 to 0.500 MPa, particularly preferably 0.030 to 0.100 MPa, and even more preferably 0.035 to 0.060 MPa. This makes it easy to obtain good adhesive strength after lamination of the members, as well as good blister resistance and step conformability. The method for measuring the storage modulus G' in this specification is as shown in the test examples described below.

[0119] In this embodiment, the storage modulus G' at 80°C of the adhesive constituting the adhesive layer after lamination is preferably 0.001 to 2 MPa, more preferably 0.003 to 1 MPa, more preferably 0.006 to 0.100 MPa, particularly preferably 0.010 to 0.050 MPa, and even more preferably 0.015 to 0.023 MPa. This makes it easy to obtain good adhesive strength at high temperatures after lamination of the members, as well as good blister resistance and step conformability.

[0120] Here, in this specification, the term "adhesive layer after lamination" means, if the adhesive layer is not active energy ray-curable, an adhesive layer in the same state as the adhesive layer of the adhesive sheet; and, if the adhesive layer is active energy ray-curable, means an adhesive layer after lamination that has been cured by exposure to active energy rays.

[0121] (1-2) Adhesion Strength The adhesion strength of the adhesive layer of the adhesive sheet according to this embodiment to soda-lime glass after application is preferably 1 to 100 N / 25 mm, more preferably 6 to 70 N / 25 mm, particularly preferably 12 to 60 N / 25 mm, even more preferably 18 to 50 N / 25 mm, and most preferably 24 to 44 N / 25 mm. This tends to result in excellent conformability to unevenness and blister resistance. The above-mentioned adhesion strength is basically the adhesion strength measured using the 180-degree peel method in accordance with JIS Z0237:2009, and the specific test method is as shown in the test examples described below.

[0122] (1-3) Total Light Transmittance The total light transmittance of the adhesive layer after lamination in the adhesive sheet according to this embodiment is preferably 80% or more, more preferably 90% or more, particularly preferably 95% or more, and even more preferably 99% or more. This provides very high transparency and makes the sheet suitable for optical applications (displays). The upper limit of the total light transmittance is not particularly limited, and may be 100%, or may be a value slightly exceeding 100% due to measurement constraints. The total light transmittance in this specification is a value measured in accordance with JIS K7361-1:1997, and specific test methods are as shown in the test examples described below.

[0123] (1-4) Haze Value The haze value of the adhesive layer after lamination in the adhesive sheet according to this embodiment is preferably 2% or less, and particularly preferably 1% or less. This provides very high transparency and makes the adhesive sheet suitable for optical applications (displays). The lower limit of the haze value is not particularly limited, and may be 0%. The haze value in this specification is a value measured in accordance with JIS K7136:2000, and specific test methods are as shown in the test examples described below.

[0124] (1-5) Step-Conforming Ratio The step-conforming ratio (%) of the adhesive layer after lamination in the adhesive sheet according to this embodiment, as expressed by the following formula, is preferably 20% or more, particularly preferably 30% or more, and even more preferably 40% or more. This means that the step-conforming ability under high-temperature and high-humidity conditions is excellent, and in this case, the initial step-conforming ability (at the time of lamination) can also be said to be excellent. The upper limit of the step-conforming ratio is not particularly limited, but is usually preferably 80% or less, particularly preferably 70% or less. Step-conforming ratio (%) = {(Height of step (μm) that remains filled without bubbles, lifting, peeling, etc. after a predetermined durability test)) / (Thickness of adhesive layer)} × 100. The step-conforming ratio test method is as shown in the test examples described below.

[0125] (2) Specific Configuration of Adhesive Sheet A specific configuration of one example of the adhesive sheet according to this embodiment is shown in Figure 1. As shown in Figure 1, adhesive sheet 1 according to one embodiment is composed of two release sheets 12a, 12b and adhesive layer 11 sandwiched between these two release sheets 12a, 12b so as to contact the release surfaces of these two release sheets 12a, 12b. Note that in this specification, the release surface of a release sheet refers to the surface of the release sheet that has releasability, and includes both a surface that has been subjected to a release treatment and a surface that exhibits releasability even without being subjected to a release treatment.

[0126] The adhesive layer 11 is made of the adhesive according to the embodiment described above. The release sheets 12a and 12b protect the adhesive layer until the adhesive sheet is in use, and are peeled off when the adhesive sheet (adhesive layer) is to be used. In the adhesive sheet 1 according to this embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

[0127] Examples of materials that can be used as the release sheets 12a and 12b include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester polymer films, polystyrene films, polycarbonate films, polyimide films, and fluororesin films. Crosslinked films of these materials can also be used. Furthermore, laminated films of these materials may also be used. From the perspective of the SDGs, the material constituting the release sheets may be a material with a high biomass content, a recyclable or reusable material, or a recycled or reused material.

[0128] It is preferable that the release surfaces of the release sheets 12a and 12b (particularly the surfaces that come into contact with the adhesive layer 11) are subjected to a release treatment. Examples of release agents used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0129] There is no particular limitation on the thickness of the release sheets 12a and 12b, but it is usually about 20 to 150 μm.

[0130] From the viewpoint of ease of handling, it is preferable that one of the two release sheets 12a, 12b be a heavy release type release sheet with a large release force and the other be a light release type release sheet with a small release force.

[0131] (3) Manufacturing of Adhesive Sheet In one manufacturing example of adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), and a heat treatment is carried out to thermally crosslink the adhesive composition P to form a coating layer, after which the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer. If a curing period is required, a curing period is allowed, but if no curing period is required, the coating layer becomes adhesive layer 11 as is. Through the above steps, adhesive sheet 1 is obtained. The conditions for the heat treatment and curing are as described above.

[0132] The adhesive composition P can be applied by a coating solution such as bar coating, knife coating, roll coating, blade coating, die coating, or gravure coating.

[0133] (4) Use The adhesive sheet according to this embodiment is used to bond two members together, at least one of which is an optical member.

[0134] Examples of optical components include components constituting a display body (display body components) described below, as well as components constituting a solar cell, and components constituting a mobile body (car, ship, aircraft, etc.) or building (windows, exterior materials, interior materials, etc.), and are usually components made of a light-transmitting plastic plate, plastic film, glass plate, glass film, etc., or components containing any of these.

[0135] The other of the two members may be an optical member or a member made of an opaque or translucent material, such as metal, ceramics, colored plastic, colored glass, graphite, paper, wood, stone, mortar, plaster, or the like, or a member containing any of these.

[0136] [Optical Construction] An optical construction according to one embodiment of the present invention is formed by bonding at least two members together with an adhesive layer, at least one of which is an optical member. The adhesive layer is formed from the adhesive according to the above-described embodiment, or from the adhesive layer of the adhesive sheet according to the above-described embodiment.

[0137] The thickness of the adhesive layer in this embodiment is the same as that of the adhesive layer of the adhesive sheet according to the above-described embodiment, and the optical member is as described in the above-described embodiment.

[0138] To manufacture the optical construction according to this embodiment, for example, the adhesive coating liquid described above is applied to one component to form an adhesive layer, and then another component is bonded to the adhesive layer. As another example, the adhesive layer of the adhesive sheet described above is bonded to one component, and then another component is bonded to the adhesive layer.

[0139] Here, when the adhesive layer is active energy ray-curable, it is preferable to cure the adhesive layer by irradiating it with active energy rays through any member (member that transmits active energy rays) after the lamination.

[0140] The active energy ray refers to an electromagnetic wave or a charged particle beam that has an energy quantum, and specific examples thereof include ultraviolet rays, electron beams, etc. Among active energy rays, ultraviolet rays are particularly preferred because they are easy to handle.

[0141] The ultraviolet irradiation can be performed using a high-pressure mercury lamp, a Heraeus H lamp, a xenon lamp, or the like, and the amount of ultraviolet irradiation is set to an illuminance of 50 to 1000 mW / cm. ２ The light intensity is preferably about 50 to 10,000 mJ / cm. ２ is preferably 80 to 5000 mJ / cm ２ More preferably, it is 300 to 2000 mJ / cm ２ On the other hand, the electron beam irradiation can be carried out by an electron beam accelerator or the like, and the irradiation dose of the electron beam is preferably about 10 to 1000 krad.

[0142] [Display Body] A display body according to one embodiment of the present invention includes one display body component, another display body component, and an adhesive layer that bonds the one display body component and the other display body component to each other. The adhesive layer is formed from the adhesive layer of the adhesive sheet according to the embodiment described above.

[0143] At least one of the one display member constituting member and the other display member constituting member may have a step at least on the surface on the side to be bonded by the adhesive layer.

[0144] Both the first display member and the second display member may be hard plates. When two hard plates are bonded together, the hard plates are rigid and inflexible, so that the adhesive layer is attached to one of the hard plates and the two hard plates are pressed vertically to bring the hard plates into close contact with the adhesive layer, thereby bonding the two hard plates together.

[0145] A display according to one embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 2, the display 2 according to this embodiment is configured to include a first display component 21 (one display component), a second display component 22 (another display component), and an adhesive layer 11 located therebetween that bonds the first display component 21 and the second display component 22 to each other.

[0146] At least one of the first display body component 21 and the second display body component 22 may have a step on the surface that is bonded to the first display body component 21 by the adhesive layer 11. In the present embodiment shown in Fig. 2, the first display body component 21 has a step on the surface on the adhesive layer 11 side due to the printing layer 3 or the like.

[0147] The adhesive layer 11 in the display body 2 is either the adhesive layer 11 (non-curable by active energy rays) of the adhesive sheet 1 described above, or the adhesive layer 11 (curable by active energy rays) of the adhesive sheet 1 described above that has been cured by irradiation with active energy rays.

[0148] Examples of the display 2 include a liquid crystal (LCD) display, a light-emitting diode (LED) display, an organic electroluminescence (OLED) display, and electronic paper, and may also be a touch panel. Note that LED displays also include those using mini LEDs and micro LEDs.

[0149] The first display member 21 is preferably a protective panel made of a glass plate, a plastic plate, or a laminate containing these. In this case, the printing layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the first display member 21.

[0150] The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, etc. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5 mm, and preferably 0.2 to 2 mm.

[0151] The plastic plate is not particularly limited, and examples thereof include an acrylic plate, a polycarbonate plate, etc. The thickness of the plastic plate is not particularly limited, but is usually 0.2 to 5 mm, and preferably 0.4 to 3 mm.

[0152] On one or both sides of the glass plate or plastic plate, various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare layer, etc.) may be provided, or optical members may be laminated. Furthermore, the transparent conductive film and metal layer may be patterned.

[0153] The second display component 22 is preferably an optical element to be attached to the first display component 21, a display module (e.g., a liquid crystal (LCD) module, a light-emitting diode (LED) module, an organic electroluminescence (organic EL) module, etc.), an optical element as part of a display module, or a laminate including a display module.

[0154] Examples of the optical member include a shatterproof film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retardation film), a viewing angle compensation film, a brightness improvement film, a contrast improvement film, a liquid crystal polymer film, a diffusion film, a semi-transmitting reflective film, a transparent conductive film, etc. A preferred example of the transparent conductive film is an ITO-PET film in which a tin-doped indium oxide (ITO) layer is formed on one surface of a polyethylene terephthalate film.

[0155] The material constituting the printing layer 3 is not particularly limited, and known materials for printing can be used. The thickness of the printing 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. When the thickness of the printing layer 3 is within the above range, the step-following ability of the adhesive layer 11 is effectively exhibited, and the concealing property that is the purpose of the printing layer 3 can be sufficiently ensured. Note that the printing layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the display component.

[0156] To manufacture the display body 2, as an example, one of the release sheets 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is attached to the surface of the first display body component 21 on which the printing layer 3 is present.

[0157] Next, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display body component 22 to obtain the display body. As another example, the bonding order of the first display body component 21 and the second display body component 22 may be reversed.

[0158] Here, when the adhesive layer 11 is active energy ray curable (when it contains an active energy ray curable component (D)), after bonding the laminate of the first display body component 21 and the adhesive layer 11 to the second display body component 22, it is preferable to irradiate the adhesive layer 11 with active energy rays through the first display body component 21 and / or the second display body component 22 to cure the adhesive layer 11.

[0159] In the display body 2, the adhesive constituting the adhesive layer 11 contains the oxygen absorber described above, and therefore, even when exposed to high temperatures for a long period of time (for example, 100 hours in an atmosphere of 140°C), yellowing of the adhesive layer 11 at the edge of the display body 2 can be suppressed.

[0160] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0161] For example, one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, or a desired optical member may be laminated in place of the release sheets 12a and / or 12b. The first display body component 21 may not have a step. Furthermore, 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.

[0162] In this specification, when it is stated that "X to Y" (X and Y are any numbers), it means "X or more and Y or less" unless otherwise specified, and also means "preferably greater than X" or "preferably smaller than Y". Furthermore, when it is stated that "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when it is stated that "Y or less" (Y is any number), it also means "preferably smaller than Y" unless otherwise specified.

[0163] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0164] Example 1 1. Preparation of (meth)acrylic acid ester polymer 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 were copolymerized by solution polymerization to prepare a (meth)acrylic acid ester polymer (A). The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described below, and the weight average molecular weight (Mw) was found to be 500,000.

[0165] 2. Preparation of Adhesive Composition

[0073] 100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth)acrylic acid ester polymer (A) obtained in the above step 1, 0.15 parts by mass of an isocyanate-based crosslinking agent (B1; manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E", isocyanate type: TDI) as the crosslinking agent (B), and a compound represented by the following formula (III) as the oxygen absorber (C) were mixed. (manufactured by Kuraray Co., Ltd., product name "Diprenyl Glycerin Ether (DPNG)")), 6.9 parts by mass of ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-9300-1CL") as the active energy ray-curable component (D), 0.69 parts by mass of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide as the photopolymerization initiator (E), and 0.25 parts by mass of 3-glycidoxypropyltrimethoxysilane as the silane coupling agent (F) were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition.

[0166] Here, the formulations (solid content equivalent) of the adhesive compositions when the (meth)acrylic acid ester polymer (A) is taken as 100 parts by mass (solid content equivalent) are shown in Table 1. The details of the abbreviations and the like shown in Table 1 are as follows. [(Meth)acrylic acid ester polymer (A)] 2EHA: 2-ethylhexyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate [Crosslinking agent (B)] B1: isocyanate-based crosslinking agent, manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E", isocyanate type = TDI B2: isocyanate-based crosslinking agent, manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75", isocyanate type = XDI

[0167] 3. Manufacturing of Adhesive Sheet The coating solution of the adhesive composition obtained in step 2 above was applied with a coater to the release-treated surface of a heavy-release type release sheet R1, which had been prepared by treating one side of a polyethylene terephthalate film with a silicone-based release agent. This was then heated at 90°C for 1 minute to form a coating layer. The coating layer on the release sheet R1 obtained above was then bonded to a light-release type release sheet R2, which had been prepared by treating one side of a polyethylene terephthalate film with a silicone-based release agent, so that the release-treated surface of the release sheet R2 was in contact with the coating layer. This was then aged for 7 days under conditions of 23°C and 50% RH to produce an adhesive sheet having a 50 μm-thick adhesive layer, i.e., an adhesive sheet having a configuration of release sheet R1 / adhesive layer (thickness: 50 μm) / release sheet R2.

[0168] The thickness of the adhesive layer was measured using a constant pressure thickness measuring device (manufactured by Teclock Corporation, product name "PG-02") in accordance with JIS K 7130. Furthermore, it was confirmed that the release strength of release sheet R1 was greater than that of release sheet R2 in the obtained adhesive sheet.

[0169] Examples 2 to 4, Comparative Example 1 Adhesive sheets were produced in the same manner as in Example 1, except that the type of crosslinking agent (B) and the amount of oxygen absorber (C) added were changed as shown in Table 1.

[0170] The weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> Measurement device: HLC-8320, manufactured by Tosoh Corporation GPC columns (passed in the following order): TSK gel super H-H, TSK gel super HM-H, TSK gel super H2000, manufactured by Tosoh Corporation Measurement solvent: tetrahydrofuran Measurement temperature: 40°C

[0171] [Test Example 1] (Gel Fraction Measurement / Seasoning Evaluation) A 250 μm thick adhesive layer was prepared by laminating multiple adhesive layers from the adhesive sheets (7 days after the coating layer was formed) produced in the Examples and Comparative Examples. The adhesive layer (thickness: 250 μm) was cut into a size of 70 mm x 150 mm, and the adhesive layer was wrapped in a polyester mesh (mesh size 200). The mass was weighed using a precision balance, and the mass of the mesh alone was subtracted to calculate the mass of the adhesive alone. This mass was designated M1.

[0172] Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. The adhesive was then removed and air-dried for 24 hours in an environment at 23°C and 50% RH, and then dried in an oven at 80°C for 12 hours. After drying, the mass was weighed using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. This mass was designated M2. The gel fraction (%; G1) was expressed as (M2 / M1) x 100. The results are shown in Table 2.

[0173] In addition, an adhesive layer (thickness: 250 μm) prepared in the same manner as above was irradiated with active energy rays (ultraviolet rays; UV) to cure the adhesive layer. The gel fraction (%; G1c) of the adhesive in the adhesive layer after curing with active energy rays was measured in the same manner as above. The results are shown in Table 2. The irradiation conditions for active energy rays were as follows.

[0174] <Activated energy ray irradiation conditions> - High pressure mercury lamp used - Illuminance: 200 mW / cm ２ , Light amount: 1000mJ / cm２ ・UV illuminance and light intensity meter used is "UVPF-A1" manufactured by iGraphics

[0175] On the other hand, the adhesive sheets produced in the Examples and Comparative Examples were aged for an additional 7 days to obtain adhesive layers 14 days after the formation of the coating layer. The gel fraction (%; G2) of the adhesive layers was measured in the same manner as above. Furthermore, the adhesive layers 14 days after the formation of the coating layer were irradiated with active energy rays (ultraviolet rays; UV) in the same manner as above to cure the adhesive layers. The gel fraction (%; G2c) of the adhesive in the adhesive layers after curing with active energy rays was measured in the same manner as above. The respective results are shown in Table 2.

[0176] Furthermore, the difference (G2-G1; points) was calculated by subtracting the gel fraction G1 (%) from the gel fraction G2 (%), and the seasoning was evaluated based on the following criteria. The results are shown in Table 2. ◯: The difference between (G2-G1) is less than 5 points. ×: The difference between (G2-G1) is 5 points or more.

[0177] [Test Example 2] (Measurement of storage modulus G') A 250 μm thick adhesive layer was produced by laminating multiple adhesive layers of the adhesive sheets produced in the Examples and Comparative Examples. The adhesive layer (250 μm) was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in Test Example 1, and the adhesive layer was cured. A cylindrical body with a diameter of 8 mm (height 0.25 mm) was punched out from the adhesive layer (250 μm) after active energy ray curing, and this was used as a sample.

[0178] The dynamic viscoelasticity of the above sample was measured by a torsional shear method using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302") under the following conditions in accordance with JIS K7244-1, and the storage modulus G' (MPa) at 23°C and the storage modulus G' (MPa) at 80°C were observed. The results are shown in Table 2. Measurement frequency: 1 Hz Measurement temperature range: 0°C to 140°C Heating rate: 4°C / min

[0179] [Test Example 3] (Measurement of b* / Evaluation of Edge Yellowing) A 250 μm thick adhesive layer was produced by laminating multiple adhesive layers of the adhesive sheets produced in the Examples and Comparative Examples. Using this adhesive layer (thickness: 250 μm), two soda-lime glass plates (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 1.1 mm, length 7.0 mm × width 7.0 mm) were bonded to produce a laminate (soda-lime glass plate / adhesive layer (250 μm) / soda-lime glass plate). This bonding was performed in an autoclave manufactured by Kurihara Manufacturing Co., Ltd., at 0.5 MPa and 50 ° C. for 20 minutes.

[0180] Next, the laminate was irradiated with active energy rays (ultraviolet rays; UV) under the same active energy ray irradiation conditions as in Test Example 1 to cure the adhesive layer, and this was used as a measurement sample.

[0181] The obtained measurement sample was measured for chromaticity b* (chromaticity b*1) defined by the CIE 1976 L*a*b* color system using a simultaneous photometric spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SQ2000"). Note that since the soda-lime glass plate constituting the measurement sample is colorless and transparent, the chromaticity b* measured here is the chromaticity b* of the adhesive layer (adhesive layer after curing). The results are shown in Table 2.

[0182] Next, the measurement sample was subjected to durability conditions in an atmosphere at 140°C for 100 hours. The chromaticity b* of the end and center portions of the measurement sample after this durability condition (end portion: chromaticity b*2, center portion: chromaticity b*3) was measured in the same manner as described above. The results are shown in Table 2. Here, the end portion of the measurement sample refers to a circular area with a radius of 2 mm, with its center point located 3 mm inward from the center edge of any one side of the measurement sample in a planar view. Furthermore, the center portion of the measurement sample refers to a 10 mm square area with the same center point as the center point of the measurement sample in a planar view.

[0183] The absolute value of the ratio of the chromaticity b*2 to the chromaticity b*1 obtained above (b*2 / b*1), and the absolute value of the ratio of the chromaticity b*2 to the chromaticity b*3 (b*2 / b*3) were calculated. Based on the above measured and calculated values, edge yellowing was evaluated according to the following criteria. The results are shown in Table 2. <Criterion 1> ⊚...The absolute value of b*2 / b*1 was 2.5 or less. ◯...The absolute value of b*2 / b*1 was more than 2.5 and less than 4.5. ×...The absolute value of b*2 / b*1 was more than 4.5. <Criterion 2> ⊚...The absolute value of b*2 was less than 1.0. ◯...The absolute value of b*2 was 1.0 or more and less than 2.0. ×...The absolute value of b*2 was 2.0 or more. <Criterion 3> ⊚...The absolute value of b*2 / b*3 was 1.8 or less. ◯...The absolute value of b*2 / b*3 was more than 1.8 and less than 2.5. ×...The absolute value of b*2 / b*3 was more than 2.5.

[0184] Test Example 4 (Measurement of Total Light Transmittance) A measurement sample was prepared in the same manner as in Test Example 3. After background measurement of the measurement sample using a soda lime glass plate, the total light transmittance (%) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7361-1:1997. The results are shown in Table 2. The total light transmittance of the adhesive layer before curing with active energy rays was also measured, and the same measurement results were obtained.

[0185] Test Example 5 (Haze Value Measurement) A measurement sample was prepared in the same manner as in Test Example 3. After background measurement of the measurement sample using a soda lime glass plate, the haze value (%) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7136:2000. The results are shown in Table 2. The haze value of the adhesive layer before curing with active energy rays was also measured, and the same measurement result was obtained.

[0186] [Test Example 6] (Measurement of adhesive strength) The release sheet R2 was peeled off from the adhesive sheet produced in the Examples and Comparative Examples, and the exposed adhesive layer was attached to one of the easy-adhesion layers of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360", thickness: 100 μm) having easy-adhesion layers on both sides, to obtain a release sheet R1 / adhesive layer / PET film laminate. This laminate was cut into a 25 mm wide, 100 mm long piece, which was used as a sample.

[0187] The release sheet R1 was peeled off from the sample in an environment of 23°C and 50% RH, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and then pressurized for 20 minutes at 0.5 MPa and 50°C in an autoclave manufactured by Kurihara Manufacturing Co., Ltd. Then, active energy rays (ultraviolet rays; UV) were irradiated through the soda lime glass under the same active energy ray irradiation conditions as in Test Example 1, to cure the adhesive layer.

[0188] After that, the adhesive strength (N / 25 mm) was measured using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.) at a peel speed of 300 mm / min and a peel angle of 180 degrees. The measurement was conducted under conditions other than those described here in accordance with JIS Z0237:2009. The results are shown in Table 2.

[0189] Test Example 7 (Evaluation of Blister Resistance) The release sheet R2 was peeled off from the adhesive sheets produced in the Examples and Comparative Examples, and the exposed adhesive layer (50 μm thick) was bonded to the PC plate side of a plastic plate (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "Iupilon Sheet MR58U", thickness: 0.7 mm) consisting of a polycarbonate (PC) plate and a polymethyl methacrylate (PMMA) layer laminated thereon. The release sheet R1 was then peeled off from the adhesive layer to expose the adhesive layer, and a transparent conductive film (manufactured by Oike Kogyo Co., Ltd., laminate of a PET film and an ITO layer (ITO-PET film), total thickness 125 μm) was bonded to the adhesive layer so that the ITO layer side was in contact with the adhesive layer. The sheet was then autoclaved for 20 minutes at 50°C and 0.5 MPa.

[0190] The adhesive layer of the obtained laminate was cured by irradiating it with active energy rays (ultraviolet rays; UV) through the transparent conductive film under the same conditions as in Test Example 1. Thereafter, the laminate was left to stand at normal pressure, 23°C, and 50% RH for 24 hours, and this was used as a sample.

[0191] The obtained sample was stored for 72 hours under high temperature and high humidity conditions of 85°C and 85% RH. Thereafter, the condition at the interface between the adhesive layer and the adherend (plastic plate) was visually inspected, and blister resistance was evaluated according to the following criteria. The results are shown in Table 2. ⊚: No bubbles or lifting occurred. ◯: Bubbles or lifting with a diameter of 5 mm or less occurred, but were at a level that was practically acceptable. ×: Bubbles or lifting with a diameter of more than 5 mm occurred, and were at a level that was not practically acceptable.

[0192] Test Example 8 (Evaluation of Step-Conforming Ability) A UV-curable ink (manufactured by Teikoku Ink Co., Ltd., product name "POS-911 Black") was screen-printed to a predetermined thickness on the surface of a glass plate (manufactured by NSG Precision, product name "Corning Glass Eagle XG", length 90 mm x width 50 mm x thickness 0.5 mm) in the shape of a picture frame (outer dimensions: length 90 mm x width 5 mm, width 5 mm). Then, UV light (80 W / cm ２ The printed ultraviolet-curable ink was cured by a heating method using a heating element (two metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m / min) to prepare a stepped glass plate having printed steps (step height: one of 5 μm, 10 μm, 15 μm, 20 μm, and 25 μm).

[0193] The release sheet R2 was peeled off from the adhesive sheet produced in the Examples and Comparative Examples, and the exposed adhesive layer (50 μm thick) was attached to the adhesive layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360", thickness: 100 μm). Next, the release sheet R1 was peeled off to expose the adhesive layer, and using a laminator (manufactured by Fujipla Co., Ltd., product name "LPD3214"), the adhesive layer was laminated to each stepped glass plate so that it covered the entire frame-shaped print. Then, the sheet was autoclaved for 20 minutes under conditions of 50 ° C. and 0.5 MPa, and left for 24 hours at normal pressure, 23 ° C., and 50% RH.

[0194] Next, active energy rays were irradiated through the PET film under the same conditions as in Test Example 1 to cure the adhesive layer. Thereafter, the sample was stored for 120 hours under high-temperature, high-humidity conditions of 85°C and 85% RH (durability test), and the step-following ability was evaluated. Step-following ability was determined by whether the printed step was completely filled with the adhesive layer. If bubbles, lifting, peeling, or the like were observed at the interface between the printed step and the adhesive layer, it was determined that the printed step could not be followed. Here, step-following ability was evaluated using the step-following rate (%) shown by the following formula. The results are shown in Table 2. Step-following rate (%) = {(Height of the step that remained filled without bubbles, lifting, peeling, or the like after the durability test (μm)) / (Thickness of adhesive layer)} × 100. ◯: Step-following rate 40% or more. ×: Step-following rate less than 40%.

[0195]

[0196]

[0197] As can be seen from Table 2, the adhesive sheets produced in the examples were able to suppress yellowing of the adhesive layer at the edges of the laminate.

[0198] The adhesive and adhesive sheet according to the present invention can be suitably used, for example, in the production of a display, for bonding a display component such as a protective panel to a desired display component.

[0199] REFERENCE SIGNS LIST 1 adhesive sheet 11 adhesive layer 12a, 12b release sheets 2 display body 21 first display body constituent member 22 second display body constituent member 3 print layer

Claims

1. An adhesive containing an oxygen absorber, used for optical applications, It is an acrylic adhesive, When a laminate, formed by bonding two 1.1 mm thick, 7.0 cm square soda-lime glass plates with a 250 μm thick adhesive layer made from the aforementioned adhesive, is subjected to a durability condition of being immersed in a 140°C atmosphere for 100 hours, Let b*1 be the chromaticity b* of the adhesive layer before the aforementioned durability conditions, as defined by the CIE 1976 L*a*b* color system. When the chromaticity b* of the adhesive layer at the end of the laminate after the aforementioned durability conditions is defined by the CIE 1976 L*a*b* color system, and this is set to b*2, The absolute value of the ratio of b*2 to b*1 is 4.5 or less. An adhesive characterized by the following features.

2. An adhesive containing an oxygen absorber, used for optical applications, It is an acrylic adhesive, When a laminate, formed by bonding two 1.1 mm thick, 7.0 cm square soda-lime glass plates with a 250 μm thick adhesive layer made from the aforementioned adhesive, is subjected to a durability condition of being immersed in a 140°C atmosphere for 100 hours, When the chromaticity b* of the adhesive layer at the end of the laminate after the aforementioned durability conditions is defined by the CIE 1976 L*a*b* color system, and this is set to b*2, The absolute value of b*2 is less than 2.

0. An adhesive characterized by the following features.

3. An adhesive containing an oxygen absorber, used for optical applications, It is an acrylic adhesive, When a laminate, formed by bonding two 1.1 mm thick, 7.0 cm square soda-lime glass plates with a 250 μm thick adhesive layer made from the aforementioned adhesive, is subjected to a durability condition of being immersed in a 140°C atmosphere for 100 hours, Let b*2 be the chromaticity b* of the adhesive layer at the end of the laminate after the aforementioned durability conditions, as defined by the CIE 1976 L*a*b* color system. When the chromaticity b* of the adhesive layer in the central part of the laminate after the aforementioned durability conditions is defined as b*3 according to the CIE 1976 L*a*b* color system, The absolute value of the ratio of b*2 to b*3 is 2.5 or less. An adhesive characterized by the following features.

4. An adhesive containing an oxygen absorber, used for optical applications, It is an adhesive that can be cured by active energy rays, When a laminate, formed by bonding two 1.1 mm thick, 7.0 cm square soda-lime glass plates with a 250 μm thick adhesive layer made from the aforementioned adhesive, is subjected to a durability condition of being immersed in a 140°C atmosphere for 100 hours, Let b*1 be the chromaticity b* of the adhesive layer before the aforementioned durability conditions, as defined by the CIE 1976 L*a*b* color system. When the chromaticity b* of the adhesive layer at the end of the laminate after the aforementioned durability conditions is defined by the CIE 1976 L*a*b* color system, and this is set to b*2, The absolute value of the ratio of b*2 to b*1 is 4.5 or less. An adhesive characterized by the following features.

5. An adhesive containing an oxygen absorber, used for optical applications, It is an adhesive that can be cured by active energy rays, When a laminate, formed by bonding two 1.1 mm thick, 7.0 cm square soda-lime glass plates with a 250 μm thick adhesive layer made from the aforementioned adhesive, is subjected to a durability condition of being immersed in a 140°C atmosphere for 100 hours, When the chromaticity b* of the adhesive layer at the end of the laminate after the aforementioned durability conditions is defined by the CIE 1976 L*a*b* color system, and this is set to b*2, The absolute value of b*2 is less than 2.

0. An adhesive characterized by the following features.

6. An adhesive containing an oxygen absorber, used for optical applications, It is an adhesive that can be cured by active energy rays, When a laminate, formed by bonding two 1.1 mm thick, 7.0 cm square soda-lime glass plates with a 250 μm thick adhesive layer made from the aforementioned adhesive, is subjected to a durability condition of being immersed in a 140°C atmosphere for 100 hours, Let b*2 be the chromaticity b* of the adhesive layer at the end of the laminate after the aforementioned durability conditions, as defined by the CIE 1976 L*a*b* color system. When the chromaticity b* of the adhesive layer in the central part of the laminate after the aforementioned durability conditions is defined as b*3 according to the CIE 1976 L*a*b* color system, The absolute value of the ratio of b*2 to b*3 is 2.5 or less. An adhesive characterized by the following features.

7. The adhesive according to any one of claims 1 to 6, characterized in that the oxygen absorber is a compound represented by the following general formula (I). 【Chemistry 1】 (In general formula (I), X and Y each independently represent a chalcogen atom, and R １ , R ２ , R ７ , and R ８ each independently represent any one of an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, and an aralkyl group. R ３ , R ４ , R ５ , and R ６ each independently represent any one of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, and an aralkyl group. J represents a linking group composed of an aliphatic hydrocarbon having 3 to 15 carbon atoms, and any carbon atom of the linking group may be substituted with an oxygen atom, and may have at least one selected from the group consisting of a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, and an alkenyloxy group having 2 to 5 carbon atoms as a substituent. n is an arbitrary integer from 1 to 5. However, when there are a plurality of Y, R ５ , R ６ , R ７ , and R ８ , they may be different atoms or groups.)

8. The adhesive according to any one of claims 1 to 6, characterized in that the oxygen absorber is a compound represented by the following general formula (II). 【Chemistry 2】 (In general formula (II), R ９ R represents a hydrogen atom or a methyl group. １０ R represents one of the following: a hydroxyl group, a (meth)acryloyloxy group, a styryloxy group, or an alkenyloxy group having 2 to 5 carbon atoms. １１ , R １２ , R １３ , and R １４ Each of these independently represents one of the following: an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group.

9. The adhesive according to any one of claims 1 to 6, characterized in that the oxygen absorber is a compound represented by the following formula (III). 【Transformation 3】

10. The adhesive according to any one of claims 4 to 6, characterized in that it is an acrylic adhesive.

11. The adhesive according to any one of claims 1 to 6, characterized in that the main adhesive component is a (meth)acrylic acid ester polymer or a crosslinked product thereof.

12. The adhesive according to any one of claims 1 to 3, characterized in that it is an adhesive that can be cured by active energy rays.

13. The adhesive according to any one of claims 1 to 6, characterized in that it is a solvent-type adhesive.

14. An adhesive sheet having an adhesive layer for bonding two members together, At least one of the aforementioned members is an optical member, The adhesive layer comprises the adhesive described in any one of claims 1 to 6. An adhesive sheet characterized by the following features.

15. The adhesive sheet comprises two release sheets. The adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets. The adhesive sheet according to feature 14.

16. An optical structure comprising at least two members bonded together by an adhesive layer, At least one of the aforementioned members is an optical member, The adhesive layer is formed from the adhesive described in any one of claims 1 to 6. An optical structure characterized by the following features.

17. One display component, Other display component members, An adhesive layer that bonds the first display component and the other display component to each other. A display body equipped with, The adhesive layer is formed from the adhesive layer of the adhesive sheet described in claim 14. A display unit characterized by the following features.

18. The display body according to claim 17, characterized in that both the first display body component and the other display body component are made of a hard plate.

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