Adhesive sheet, and release film-equipped adhesive sheet, laminate for image display device, image display device, and adhesive sheet for organic light-emitting diode display device all using said adhesive sheet

Abstract

Provided is an adhesive sheet that has sufficient impact resistance and transparency as well as excellent ultraviolet absorption in the vicinity of the visible light region (for example, a wavelength of 405 nm).　The adhesive sheet comprises a resin component (A) having a structural unit derived from a (meth)acrylate-based monomer and an ultraviolet absorber (B), and satisfies the following requirements [I] and [II]. [I] The ultraviolet absorber (B) includes an ultraviolet absorber (B-1) having an absorption maximum at a wavelength of 300-360 nm and an ultraviolet absorber (B-2), other than the (B-1), having an absorption maximum at a wavelength of 350-420 nm. [II] The content ratio by mass of the ultraviolet absorber (B-1) to the ultraviolet absorber (B-2) contained in the adhesive sheet is 30:70 to 70:30.

Description

Adhesive sheet, adhesive sheet with release film using the same, laminate for image display device, image display device, adhesive sheet for organic light-emitting diode display device

[0001] The present invention relates to an adhesive sheet, and an adhesive sheet with a release film, a laminate for an image display device, an image display device, and an adhesive sheet for an organic light-emitting diode display device, using the same; more specifically, the present invention relates to an adhesive sheet that has sufficient adhesiveness and impact resistance and is excellent in ultraviolet absorption up to the vicinity of the visible light region, and an adhesive sheet with a release film, a laminate for an image display device, an image display device, and an adhesive sheet for an organic light-emitting diode display device, using the same.

[0002] In recent years, in response to the need for power saving, weight reduction, and thinning of image display devices installed in mobile electronic devices, image display devices using organic light-emitting diodes (OLEDs) and quantum dots (QDs) have been developed and are becoming widely used. In order to improve the visibility of these image display devices, the gap between the image display panel and optical components such as a protective panel or touch panel member arranged on the front side (viewing side) of the image display panel is filled with a resin such as an adhesive sheet or adhesive to suppress reflection of incident light and outgoing light from the displayed image at the air layer interface.

[0003] In the image display device, components within the image display device may be deteriorated by incident ultraviolet light. In particular, organic light-emitting diodes (OLEDs) are susceptible to deterioration by ultraviolet light, so protection from ultraviolet light incident from outdoor sunlight, etc. is considered important. For this reason, a known solution is to incorporate an ultraviolet absorber into a transparent adhesive sheet. For example, Patent Document 1 and Patent Document 2 disclose adhesive sheets containing an ultraviolet absorber.

[0004] On the other hand, mobile electronic devices are often at risk of breakage due to impacts such as being dropped due to their usage patterns. Impact resistance is also required for the pressure-sensitive adhesive sheet itself, so that components are less likely to be damaged or peeled apart due to the impact of a drop. For example, Patent Document 3 discloses a pressure-sensitive adhesive sheet having a tan δ peak top between -20 and 0°C, with the tan δ peak top value being 0.8 or more.

[0005] JP 2022-148857 A JP 2021-185570 A JP 2023-8631 A

[0006] Recently, with the trend toward thinner mobile electronic devices, in addition to protection from ultraviolet rays incident from the outside, impact resistance of the adhesive sheet itself is required to protect components inside the image display device from impacts from the external environment. The technologies disclosed in Patent Documents 1 and 2 take into consideration ultraviolet absorption and durability of the adhesive sheet, but do not take into consideration the impact resistance of the adhesive. Furthermore, the technology disclosed in Patent Document 3 takes into consideration the impact resistance of the adhesive, but does not take into consideration protection from ultraviolet rays.

[0007] In view of this background, the present invention provides a pressure-sensitive adhesive sheet that has sufficient transparency and excellent ultraviolet absorption up to the vicinity of the visible light region (for example, a wavelength of 405 nm), and further has sufficient impact resistance.

[0008] However, in view of the above circumstances, the present inventors have conducted extensive research and found that the above-mentioned problems can be solved by using two types of ultraviolet absorbers having absorption maxima at specific wavelengths in combination and setting the content ratio thereof within a specific range.

[0009] That is, the present invention has the following aspects. [1] A pressure-sensitive adhesive sheet comprising a resin component (A) having a structural unit derived from a (meth)acrylate monomer and an ultraviolet absorber (B), and satisfying the following requirements [I] and [II]. [I] The ultraviolet absorber (B) comprises an ultraviolet absorber (B-1) having an absorption maximum in a wavelength range of 300 to 360 nm and an ultraviolet absorber (B-2) other than (B-1) having an absorption maximum in a wavelength range of 350 to 420 nm. [II] The content ratio of the ultraviolet absorbers (B-1) and (B-2) contained in the pressure-sensitive adhesive sheet is 30:70 to 70:30 by mass. [2] The pressure-sensitive adhesive sheet according to [1], further satisfying the following requirement [III]. [III] The pressure-sensitive adhesive sheet has a storage shear modulus at −20°C of 2.0 MPa or less and a glass transition temperature determined from the peak of the loss tangent (tan δ) of −20°C or less, as measured by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz. [3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the ultraviolet absorber (B-2) has a pyrimidine structure. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the content of the ultraviolet absorber (B) is 0.1 to 20 mass% relative to the pressure-sensitive adhesive sheet. [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the resin component (A) has a structural unit derived from a crosslinking agent (C). [6] The pressure-sensitive adhesive sheet according to [5], wherein the crosslinking agent (C) comprises an acrylic crosslinking agent having a glass transition temperature (Tg) calculated by the Fox equation of −20° C. or lower. [7] The pressure-sensitive adhesive sheet according to [5] or [6], wherein the crosslinking agent (C) comprises an acrylic crosslinking agent having 1 to 3 ethylenically unsaturated groups in the molecule. [8] The pressure-sensitive adhesive sheet according to any one of [5] to [7], wherein the crosslinking agent (C) comprises an acrylic crosslinking agent having an oxyalkylene structure. [9] The pressure-sensitive adhesive sheet according to any one of [5] to [8], wherein the crosslinking agent (C) comprises a polyfunctional (meth)acrylate oligomer having a weight-average molecular weight of 1000 or more.

[10] The pressure-sensitive adhesive sheet according to any one of [5] to [9], wherein the crosslinking agent (C) comprises a urethane (meth)acrylate.

[11] The pressure-sensitive adhesive sheet according to any one of [1] to

[10] , wherein the pressure-sensitive adhesive sheet comprises a photoinitiator (D).

[12] The pressure-sensitive adhesive sheet according to

[11] , wherein the photoinitiator (D) is a hydrogen abstraction photoinitiator.

[13] The pressure-sensitive adhesive sheet according to any one of [1] to

[12] , which has a gel fraction of 5 to 80%.

[14] A pressure-sensitive adhesive sheet with a release film, comprising the pressure-sensitive adhesive sheet according to any one of [1] to

[13] and a release film laminated together.

[15] A laminate for an image display device, comprising two optical members laminated together with the pressure-sensitive adhesive sheet according to any one of [1] to

[13] interposed between them.

[16] An image display device comprising the laminate for an image display device according to

[15] .

[17] A pressure-sensitive adhesive sheet for an organic light-emitting diode display device, comprising the pressure-sensitive adhesive sheet according to any one of [1] to

[13] .

[0010] The pressure-sensitive adhesive sheet of the present invention has sufficient transparency, excellent ultraviolet absorption properties up to the vicinity of the visible light region (e.g., wavelength 405 nm), and also excellent impact resistance, and therefore can be suitably used as a pressure-sensitive adhesive sheet for attaching optical components, particularly as a pressure-sensitive adhesive sheet for organic light-emitting diode (OLED) display devices.

[0011] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below. In the present invention, the term "film" conceptually includes a sheet, a film, and a tape. Furthermore, when the term "panel" is used, such as an image display panel or a protective panel, it includes a plate, a sheet, and a film.

[0012] 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 includes the meaning of "preferably greater than x" or "preferably smaller than y." Furthermore, when it is stated that "x or more" (x is any number), it also includes the meaning of "preferably greater than x" unless otherwise specified, and when it is stated that "y or less" (y is any number), it also includes the meaning of "preferably smaller than y" unless otherwise specified. Furthermore, in this specification, "x and / or y (x and y are any configurations)" means at least one of x and y, and can mean three possibilities: x only, y only, or x and y. Furthermore, in this specification, "(meth)acrylic" means a comprehensive definition of acrylic and methacrylic, "(meth)acrylate" means a comprehensive definition of acrylate and methacrylate, and "(meth)acryloyl" means a comprehensive definition of acryloyl and methacryloyl. In this specification, the term "(meth)acrylic polymer" refers to a resin obtained by polymerizing a polymerization component containing at least one (meth)acrylate monomer, and has structural units derived from the (meth)acrylate monomer.

[0013] <<Adhesive Sheet>> A pressure-sensitive adhesive sheet according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive sheet") contains a resin component (A) and an ultraviolet absorber (B) described below. The physical properties of the pressure-sensitive adhesive sheet will be described below.

[0014] <Physical properties of the present pressure-sensitive adhesive sheet> [Light transmittance] The light transmittance of the present pressure-sensitive adhesive sheet at a wavelength of 380 nm is usually less than 5%, preferably 3% or less, more preferably 2% or less, and particularly preferably 1% or less. By having such a light transmittance, it tends to be possible to protect components of an image display device from deterioration due to ultraviolet rays.

[0015] Furthermore, the light transmittance of the pressure-sensitive adhesive sheet at a wavelength of 405 nm is usually less than 10%, preferably 8% or less, more preferably 7% or less, and particularly preferably 5% or less. By having such a light transmittance, even image display device components that are prone to deterioration by light tend to be able to be reliably protected from incident light.

[0016] Furthermore, the light transmittance of the pressure-sensitive adhesive sheet at a wavelength of 430 nm is usually 70% or more, preferably 73% or more, and particularly preferably 75% or more. By having such a light transmittance, it tends to be usable in applications such as image display devices that require transparency.

[0017] The light transmittance at each wavelength can be obtained by measurement using a spectrophotometer.

[0018] [Storage Shear Modulus at -20°C (G'(-20°C))] The storage shear modulus at -20°C (G'(-20°C)), obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, of the present pressure-sensitive adhesive sheet is preferably 2.0 MPa or less, more preferably 1.8 MPa or less, even more preferably 1.5 MPa or less, and particularly preferably 1.25 MPa or less. The lower limit of the storage shear modulus (G'(-20°C)) of the present pressure-sensitive adhesive sheet is preferably 0.1 MPa from the viewpoint of maintaining its shape. When the storage shear modulus (G'(-20°C)) of the present pressure-sensitive adhesive sheet is within the above range, for example, when the present pressure-sensitive adhesive sheet is adhered to a component sheet to form a laminate sheet or an image display device component, the flexibility of the laminate sheet or image display device component can be increased, particularly at low temperatures, and cracking of the component sheet or image display device component due to impact tends to be suppressed. When the impact speed is high, such as when an image display device with this pressure-sensitive adhesive sheet attached is dropped or when an object is dropped onto an image display device, the viscoelastic properties of this pressure-sensitive adhesive sheet will exhibit properties in a lower temperature range based on the temperature-time conversion of a viscoelastic body. In other words, the elastic behavior becomes relatively stronger and the impact absorption performance decreases, so the viscoelastic behavior at low temperatures becomes important.

[0019] [Storage shear modulus at 23°C (G'(23°C))] Furthermore, the storage shear modulus at 23°C (G'(23°C)), obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, of the present pressure-sensitive adhesive sheet is preferably 0.25 MPa or less, more preferably 0.20 MPa or less, even more preferably 0.10 MPa or less, particularly preferably 0.09 MPa or less, most preferably 0.08 MPa or less, and especially preferably 0.07 MPa or less. From the viewpoint of shape maintenance, the lower limit of the storage shear modulus (G'(23°C)) of the present pressure-sensitive adhesive sheet is preferably 0.01 MPa. When the storage shear modulus (G'(23°C)) of the present pressure-sensitive adhesive sheet is within the above range, the pressure-sensitive adhesive sheet tends to have excellent adhesiveness and flexibility.

[0020] The storage shear modulus at -20°C (G'(-20°C)) and the storage shear modulus at 23°C (G'(23°C)) are measured, for example, as follows. The pressure-sensitive adhesive sheet is repeatedly laminated to adjust the thickness to 0.7 to 1.2 mm (for example, 0.8 mm), and then a circular sample with a diameter of 8 mm is punched out. The obtained sample is subjected to dynamic viscoelasticity measurement using a rheometer under the conditions of a measurement jig: 8 mm diameter parallel plates, a frequency: 1 Hz, a measurement temperature: -50 to 100°C, and a heating rate: 5°C / min, and the values ​​of the storage shear modulus (G') at -20°C and 23°C are read.

[0021] [Glass transition temperature (Tg)] The glass transition temperature (Tg) of the pressure-sensitive adhesive sheet, defined as the maximum point of the loss tangent (tan δ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, is preferably −20° C. or lower, more preferably −23° C. or lower, even more preferably −26° C. or lower, and particularly preferably −29° C. or lower. The lower limit is usually −70° C., preferably −60° C., and more preferably −50° C. When the glass transition temperature (Tg) of the pressure-sensitive adhesive sheet is within the above range, it becomes easier to adjust the storage shear modulus (G'(−20° C.)) of the pressure-sensitive adhesive sheet to 2.0 MPa or lower, thereby enabling improvement in impact resistance.

[0022] The loss tangent (tan δ) is expressed as loss modulus (G") / storage shear modulus (G'), and is an index of whether the PSA sheet is relatively viscous. Here, the larger the loss tangent (Tan δ) value of the PSA sheet, the more viscous it is, and the smaller the loss tangent (Tan δ) value, the less viscous it is, i.e., the more elastic it is. Furthermore, the storage modulus (G') is a parameter that represents the elastic term of the PSA sheet, which is a viscoelastic body, and represents its ability to store applied deformation energy, etc. as elastic energy. On the other hand, the loss modulus (G") is a parameter that represents the viscosity term of a viscoelastic body, and represents its ability to convert applied deformation energy, etc. into dissipated energy due to internal friction, etc. within the PSA sheet. Therefore, when the speed of impact is high, such as when an image display device to which the PSA sheet is attached is dropped, or when an object is dropped on an image display device, the viscoelastic properties of the PSA sheet will exhibit properties in a lower temperature range, based on the temperature-time conversion of a viscoelastic body. Therefore, by having the maximum point of the loss tangent (tan δ) on the low temperature side, excellent impact resistance can be obtained.

[0023] The glass transition temperature (Tg) can be obtained by reading the temperature at which the loss tangent (Tan δ) is maximized, i.e., the peak temperature, from dynamic viscoelasticity spectrum data in a shear mode obtained by the same method as in the measurement method for the storage shear modulus (G') described above.

[0024] [Maximum Value of Loss Tangent (tan δ)] The maximum value of the loss tangent (tan δ) of the present pressure-sensitive adhesive sheet is preferably 1.5 or more, more preferably 1.7 or more, and particularly preferably 1.9 or more. By making the maximum value of the loss tangent (tan δ) equal to or greater than the above-mentioned value, the energy dissipation property against an applied impact is high, and the impact resistance of the laminate sheet or image display device component tends to be improved. Furthermore, in combination with the flexibility effect due to the low storage shear modulus (G' (-20°C)), cracking of the component sheet or image display device component due to impact tends to be further suppressed. The maximum value of the loss tangent (tan δ) refers to the peak value in the tan δ curve, i.e., the point with the largest value among the inflection points where the curve changes from positive (+) to negative (-) when differentiated.

[0025] The maximum value of the loss tangent (tan δ) can be obtained by reading the peak value in the tan δ curve, i.e., the maximum value among the inflection points where the tan δ curve changes from positive (+) to negative (−) when differentiated, from the dynamic viscoelasticity spectrum data in the shear mode obtained by the same method as the above-mentioned method for measuring the storage shear modulus (G′).

[0026] The maximum values ​​of the storage shear modulus at −20° C. (G′(−20° C.)), the storage shear modulus at 23° C. (G′(23° C.)), the glass transition temperature (Tg), and the loss tangent (tan δ) can be adjusted to fall within the above ranges by adjusting the components constituting the pressure-sensitive adhesive sheet (for example, the monomer components and weight-average molecular weight constituting the resin component (A) described below, the type of crosslinking agent (C), etc.), or by adjusting the irradiation intensity and irradiation amount of active energy rays during production of the pressure-sensitive adhesive sheet described below. However, this method is not limited to this.

[0027] [Gel Fraction] The gel fraction of the present pressure-sensitive adhesive sheet is preferably 5 to 80%, more preferably 7 to 70%, even more preferably 9 to 65%, particularly preferably 10 to 60%, and most preferably 12 to 55%. When the gel fraction of the present pressure-sensitive adhesive sheet is equal to or greater than the lower limit, the sheet tends to be able to sufficiently maintain its shape. When the gel fraction is equal to or less than the upper limit, the sheet tends to have excellent flexibility. The gel fraction is an indicator of the degree of crosslinking (degree of cure) and can be measured under the measurement conditions described in the Examples below.

[0028] The gel fraction can be adjusted to fall within the above range by adjusting the components constituting the pressure-sensitive adhesive sheet (e.g., the monomer components and weight-average molecular weight constituting the resin component (A) described below, the type of crosslinking agent (C), etc.), or by adjusting the irradiation intensity and dose of active energy rays during production of the pressure-sensitive adhesive sheet described below, although this method is not limited to this.

[0029] [Adhesive Strength] The adhesive strength of the present pressure-sensitive adhesive sheet against soda-lime glass at a peel angle of 180° and a peel speed of 300 mm / min is preferably 3 N / cm or more, more preferably 4 N / cm or more, and even more preferably 5 N / cm or more. An adhesive strength of 3 N / cm or more ensures that a laminate for an image display device using the present pressure-sensitive adhesive sheet has excellent durability. The upper limit of the adhesive strength is usually 50 N / cm. The adhesive strength can be measured under the measurement conditions described in the Examples below.

[0030] [Thickness] The thickness of the present pressure-sensitive adhesive sheet is not particularly limited, and is usually 10 to 1000 μm, preferably 12 to 500 μm, more preferably 15 to 250 μm, even more preferably 20 to 100 μm, and particularly preferably 25 to 50 μm. If the lower limit of the thickness of the present pressure-sensitive adhesive sheet is equal to or greater than the above-mentioned numerical value, the handleability tends to be improved. Furthermore, if the upper limit of the thickness is equal to or less than the above-mentioned numerical value, this tends to contribute to making the present pressure-sensitive adhesive sheet thinner.

[0031] As described above, the present pressure-sensitive adhesive sheet contains a resin component (A) and an ultraviolet absorber (B). The resin component (A) has structural units derived from a (meth)acrylate monomer, such as a resin component (A1) containing a (meth)acrylic polymer (P1) having structural units derived from a (meth)acrylate monomer, or a resin component (A2) formed from a syrup composition containing a (meth)acrylate monomer. The present pressure-sensitive adhesive sheet can be obtained, for example, by a method (first method) in which a pressure-sensitive adhesive composition containing a resin component (A1) containing a (meth)acrylic polymer (P1) and an ultraviolet absorber (B) is formed into a sheet and cured by crosslinking, i.e., polymerization, to form a pressure-sensitive adhesive sheet; or a method (second method) in which a syrup composition is applied to the sheet and then irradiated with active energy rays or heated to cure the (meth)acrylate monomer contained in the syrup component, forming the resin component (A2) into a pressure-sensitive adhesive sheet. The first and second methods are described in detail below.

[0032] <First Method> In the first method, the present pressure-sensitive adhesive sheet is obtained from a pressure-sensitive adhesive composition containing a resin component (A1) and an ultraviolet absorber (B). The resin component (A1) contains a (meth)acrylic polymer (P1) having a structural unit derived from a (meth)acrylate monomer. Each component contained in the pressure-sensitive adhesive composition will be described below.

[0033] [(Meth)acrylic polymer (P1)] Examples of the (meth)acrylic polymer (P1) contained in the pressure-sensitive adhesive composition include a homopolymer of an alkyl(meth)acrylate and a copolymer obtained by polymerizing a monomer component copolymerizable therewith. Among these, the (meth)acrylic polymer (P1) is preferably a copolymer, and more preferably a copolymer containing, as a copolymerization component, an alkyl(meth)acrylate (a1) having an alkyl group with 4 to 30 carbon atoms.

[0034] A more specific example of the copolymer is a copolymer of a monomer component containing an alkyl(meth)acrylate (a1) having 4 to 30 carbon atoms in the alkyl group [hereinafter, may be simply referred to as "alkyl(meth)acrylate (a1)"] and one or more copolymerizable monomers copolymerizable therewith selected from a carboxyl group-containing monomer (a2), a hydroxyl group-containing monomer (a3), a nitrogen-containing monomer (a4), an epoxy group-containing monomer (a5), a vinyl monomer (a6), an alkyl(meth)acrylate monomer (a7) having 1 to 3 carbon atoms in the alkyl group, an alicyclic monomer (a8), and other copolymerizable monomers (a9).

[0035] Among the copolymerizable monomers (a2) to (a9), the carboxyl group-containing monomer (a2), the hydroxyl group-containing monomer (a3), and the nitrogen-containing monomer (a4) are particularly preferred. Furthermore, it is particularly preferred that the copolymer does not contain the carboxyl group-containing monomer (a2) but contains either the hydroxyl group-containing monomer (a3) ​​or the nitrogen-containing monomer (a4). By including either the hydroxyl group-containing monomer (a3) ​​or the nitrogen-containing monomer (a4), corrosion resistance, adhesiveness, and resistance to wet heat whitening can be achieved when the adherend contains a corrosive component such as a metal. Furthermore, it is particularly preferred that the copolymer contains both the hydroxyl group-containing monomer (a3) ​​and the nitrogen-containing monomer (a4) in order to enhance cohesion.

[0036] [Alkyl (meth)acrylate (a1)] The alkyl (meth)acrylate (a1) is usually represented by the following formula (1): CH2=CH(R1)-COO(R2) (1) (wherein R1 represents a hydrogen atom or a methyl group, and R2 represents a linear or branched alkyl group having 4 to 30 carbon atoms.)

[0037] Specific examples of the alkyl (meth)acrylate (a1) include linear alkyl (meth)acrylates such as n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, icosyl (meth)acrylate, heneicosyl (meth)acrylate, and behenyl (meth)acrylate; sec-butyl (meth)acrylate, isobutyl (meth)acrylate, and the like. ) acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, isoicosyl (meth)acrylate, butyloctyl (meth)acrylate, isomyristyl (meth)acrylate, isocetyl (meth)acrylate, hexyldecyl (meth)acrylate, isostearyl (meth)acrylate, octyldecyl (meth)acrylate, octyldodecyl (meth)acrylate, isobehenyl (meth)acrylate, and other branched alkyl (meth)acrylates. These may be used alone or in combination of two or more.

[0038] Among these, linear alkyl (meth)acrylates are preferred from the viewpoint of obtaining flexibility. Furthermore, from the viewpoint of balancing adhesiveness and flexibility, linear alkyl (meth)acrylates having an alkyl group with 4 to 20 carbon atoms, more preferably 5 to 18, particularly 6 to 16, and even more particularly 7 to 14 carbon atoms are preferred, and examples thereof include n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate.

[0039] Among these, from the viewpoint of efficient formation of a crosslinked structure upon light irradiation, it is preferable to use a branched alkyl (meth)acrylate, and among these, a branched alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms, more preferably 5 to 18, particularly 6 to 16, and especially 7 to 14 carbon atoms is preferred, and for example, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate are preferred.

[0040] The proportion of the structural units derived from the alkyl (meth)acrylate (a1) relative to 100% by mass of the structural units of the (meth)acrylic polymer (P1) is preferably 5 to 95% by mass, more preferably 10 to 90% by mass, even more preferably 15 to 85% by mass, and particularly preferably 20 to 80% by mass. When the proportion of the structural units derived from the alkyl (meth)acrylate (a1) is equal to or greater than the lower limit, the polymer tends to have excellent flexibility and excellent conformability to uneven surfaces when the adherend has unevenness. Furthermore, when the proportion of the structural units derived from the alkyl (meth)acrylate (a1) is equal to or less than the upper limit, the effects of the copolymerizable monomer described below are easily obtained, and the polymer tends to have excellent adhesive strength and cohesive strength.

[0041] [Carboxy Group-Containing Monomer (a2)] When the (meth)acrylic polymer (P1) has a structural unit derived from a carboxy group-containing monomer (a2), the structural unit serves as a reaction site with the crosslinking agent (C) described below, and the adhesive strength of the pressure-sensitive adhesive sheet tends to be improved.

[0042] Examples of the carboxy group-containing monomer (a2) include (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, etc. These may be used alone or in combination of two or more.

[0043] When the (meth)acrylic polymer (P1) has a structural unit derived from a carboxy group-containing monomer (a2), the content thereof is usually 0.1 to 15 mass%, preferably 0.3 to 13 mass%, more preferably 0.5 to 10 mass%, and particularly preferably 1 to 6 mass%, relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1).

[0044] [Hydroxyl Group-Containing Monomer (a3)] When the (meth)acrylic polymer (P1) has a structural unit derived from a hydroxyl group-containing monomer (a3), the structural unit serves as a reaction site with the crosslinking agent (C) described below, which tends to improve the adhesive strength of the pressure-sensitive adhesive sheet and also to suppress whitening under heat and humidity.

[0045] Examples of the hydroxyl group-containing monomer (a3) ​​include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified hydroxy (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; diethylene glycol (meth)acrylate; polyethylene glycol (meth)acrylate; polypropylene glycol (meth)acrylate; polytetramethylene glycol (meth)acrylate; and polyoxyethylene poly(meth)acrylate. Examples of such vinyl ethers include (meth)acrylates having an oxyalkylene structure such as propylene glycol (meth)acrylate, primary hydroxyl group-containing (meth)acrylates such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, secondary hydroxyl group-containing (meth)acrylates such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate, tertiary hydroxyl group-containing (meth)acrylates such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate, and vinyl ethers such as 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether. These may be used alone or in combination of two or more.

[0046] Among the hydroxyl group-containing monomers (a3), hydroxyl group-containing monomers having a hydroxyalkyl group having 1 to 10, more preferably 1 to 6, and even more preferably 2 to 4 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether, are preferred, and primary hydroxyl group-containing (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, are particularly preferred.

[0047] When the (meth)acrylic polymer (P1) has a structural unit derived from a hydroxyl group-containing monomer (a3), the content thereof is usually 3 to 30 mass%, preferably 5 to 25 mass%, and particularly preferably 7 to 20 mass%, relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1), from the viewpoint of imparting cohesive strength and resistance to wet heat whitening.

[0048] [Nitrogen-Containing Monomer (a4)] When the (meth)acrylic polymer (P1) contains a structural unit derived from the nitrogen-containing monomer (a4), the cohesive strength of the pressure-sensitive adhesive sheet tends to be improved and whitening under moist heat tends to be suppressed. Furthermore, the nitrogen-containing monomer (a4) serves as a reaction site with the crosslinking agent (C) described below, which tends to improve the adhesive strength of the pressure-sensitive adhesive sheet and suppress whitening under moist heat. Furthermore, the nitrogen-containing monomer (a4) has the effect of promoting the hydrogen abstraction reaction of the hydrogen abstraction photoinitiator described below.

[0049] Examples of the nitrogen-containing monomer (a4) include amino group-containing monomers, amide group-containing monomers, isocyanate group-containing monomers, (meth)acrylonitrile, etc. These may be used alone or in combination of two or more.

[0050] Examples of the amino group-containing monomer include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino group-containing (meth)acrylates such as t-butylaminoethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; tertiary amino group-containing (meth)acrylates such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide; N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylacetamides, and N-vinylcaprolactam.

[0051] Examples of the amide group-containing monomer include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-n-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethylacrylamide, and N,N-diallyl(meth)acrylamide; hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide; maleimide or a derivative thereof.

[0052] Examples of the isocyanate group-containing monomer include 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof, etc. The isocyanate group may be protected with a blocking agent such as methyl ethyl ketone oxime, 3,5-dimethylpyrazole, 1,2,4-triazole, or diethyl malonate.

[0053] Among these nitrogen-containing monomers (a4), those having a tertiary nitrogen atom are preferred from the viewpoint of efficient formation of a crosslinked structure, and for example, tertiary amino group-containing (meth)acrylate, N,N-dialkyl(meth)acrylamide, N-vinylpyrrolidone, acryloylmorpholine, etc. are particularly preferred.

[0054] When the (meth)acrylic polymer (P1) has a structural unit derived from a nitrogen-containing monomer (a4), the content thereof is usually 0.1 to 15% by mass, preferably 0.5 to 13% by mass, particularly preferably 1 to 10% by mass, and particularly preferably 2 to 7% by mass, relative to 100% by mass of the structural units of the (meth)acrylic polymer (P1), from the viewpoint of imparting cohesive strength and resistance to wet heat whitening.

[0055] [Epoxy Group-Containing Monomer (a5)] Examples of the epoxy group-containing monomer (a5) include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. These may be used alone or in combination of two or more.

[0056] When the (meth)acrylic polymer (P1) has a structural unit derived from an epoxy group-containing monomer (a5), the content thereof is usually 0.1 to 10 mass%, preferably 0.3 to 13 mass%, particularly preferably 0.5 to 10 mass%, and especially preferably 1 to 6 mass%, relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1).

[0057] [Vinyl Monomer (a6)] Examples of the vinyl monomer (a6) include compounds having a vinyl group in the molecule. Examples of such compounds include vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl laurate, and vinyl stearate, as well as aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. These may be used alone or in combination of two or more.

[0058] When the (meth)acrylic polymer (P1) has a structural unit derived from a vinyl monomer (a6), the content thereof is usually 1 to 40 mass%, preferably 5 to 35 mass%, more preferably 8 to 30 mass%, particularly preferably 10 to 25 mass%, and especially preferably 2 to 7 mass%, relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1).

[0059] [Alkyl(meth)acrylate Monomer (a7) in Which the Alkyl Group Has 1 to 3 Carbon Atoms] Examples of the alkyl(meth)acrylate monomer (a7) in Which the alkyl group has 1 to 3 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0060] When the (meth)acrylic polymer (P1) has a structural unit derived from an alkyl (meth)acrylate monomer (a7) in which the alkyl group has 1 to 3 carbon atoms, the content thereof is, from the viewpoint of imparting cohesive strength to the PSA sheet, usually 0.1 to 15 mass%, preferably 0.5 to 13 mass%, particularly preferably 1 to 10 mass%, and especially preferably 2 to 7 mass%, relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1).

[0061] [Alicyclic Monomer (a8)] Examples of the alicyclic monomer (a8) include cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, adamantyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0062] When the (meth)acrylic polymer (P1) has a structural unit derived from an alicyclic monomer (a8), the content thereof is, from the viewpoint of imparting cohesive strength to the PSA sheet, usually 0.1 to 15 mass%, preferably 0.5 to 13 mass%, particularly preferably 1 to 10 mass%, and especially preferably 2 to 7 mass%, relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1).

[0063] [Other Copolymerizable Monomers (a9)] Examples of the other copolymerizable monomers (a9) include (meth)acrylates having an alkoxyalkylene glycol skeleton, such as methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, butoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, butoxypolypropylene glycol (meth)acrylate, methoxypolytetramethylene glycol (meth)acrylate, butoxypolytetramethylene glycol (meth)acrylate, methoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate, and butoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, and phenoxypolyethylene glycol-polypropylene glycol-(meth)acrylate; aromatic (meth)acrylates such as acrylate and nonylphenol ethylene oxide adduct (meth)acrylate, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxybenzophenone, Examples include (meth)acrylates having a benzophenone structure such as thacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof; heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate; and macromonomers.

[0064] When the (meth)acrylic polymer (P1) has a structural unit derived from another copolymerizable monomer (a9), the content thereof is usually 1 to 30% by mass, preferably 3 to 20% by mass, and more preferably 5 to 15% by mass, relative to 100% by mass of the structural units of the (meth)acrylic polymer (P1).

[0065] The (meth)acrylic polymer (P1) can be obtained by homopolymerizing an alkyl (meth)acrylate monomer when the (meth)acrylic polymer (P1) is a homopolymer, or by polymerizing a copolymerization component containing a (meth)acrylate (a1) having an alkyl group having 3 to 20 carbon atoms and the copolymerizable monomers (a2) to (a9) copolymerizable therewith when the (meth)acrylic polymer (P1) is a copolymer.

[0066] Examples of the polymerization method include conventionally known methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization, and among these, solution polymerization is preferred in that it allows the acrylic polymer (P1) to be produced safely and stably with any monomer composition.

[0067] The (meth)acrylic polymer (P1) may have a photoactive moiety, such as a polymerizable carbon-carbon double bond group, introduced into its side chain, thereby increasing the crosslinking efficiency of the pressure-sensitive adhesive composition and enabling the pressure-sensitive adhesive composition to be crosslinked in a shorter time, thereby increasing productivity.

[0068] Examples of a method for introducing a polymerizable carbon-carbon double bond group into the side chain of the (meth)acrylic polymer (P1) include a method in which a copolymer containing the above-mentioned carboxy group-containing monomer (a2), hydroxy group-containing monomer (a3), and nitrogen-containing monomer (a4) is prepared, and then a compound having a polymerizable carbon-carbon double bond group and a functional group reactive with these functional groups is subjected to a condensation or addition reaction while maintaining the activity of the polymerizable carbon-carbon double bond group.

[0069] Examples of combinations of these functional groups include an epoxy group (glycidyl group) and a carboxy group, an amino group and a carboxy group, an amino group and an isocyanate group, an epoxy group (glycidyl group) and an amino group, a hydroxyl group and an epoxy group, a hydroxyl group and an isocyanate group, etc. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferred from the standpoint of ease of reaction control, and a combination in which the copolymer has a hydroxyl group and the compound has an isocyanate group is more preferred.

[0070] Examples of the isocyanate compound having a polymerizable carbon-carbon double bond group include the above-mentioned 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.

[0071] From the viewpoint of improving adhesiveness and stress relaxation properties, the content of the compound having a functional group reactive with the functional group and a polymerizable carbon-carbon double bond group is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 1 part by mass or less, and particularly preferably 0.1 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer. The lower limit is usually 0 part by mass.

[0072] The weight average molecular weight (Mw) of the (meth)acrylic polymer (P1) is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more, from the viewpoint of obtaining a pressure-sensitive adhesive composition with high cohesive strength. Furthermore, the upper limit of the weight average molecular weight (Mw) of the (meth)acrylic polymer (P1) is preferably 1.5 million or less, more preferably 1.2 million or less, even more preferably 1.1 million or less, and particularly preferably 1 million or less, from the viewpoint of ease of handling and uniform stirring. The weight average molecular weight of the (meth)acrylic polymer (P1) is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0073] The content of the (meth)acrylic polymer (P1) in the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) is usually 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0074] [Ultraviolet Absorber (B)] The pressure-sensitive adhesive composition contains an ultraviolet absorber (B), thereby preventing optical components susceptible to ultraviolet degradation from light-induced degradation. In this embodiment, the ultraviolet absorber (B) includes an ultraviolet absorber (B-1) having an absorption maximum in the wavelength range of 300 to 360 nm and an ultraviolet absorber (B-2) other than (B-1) having an absorption maximum in the wavelength range of 350 to 420 nm. It is particularly preferred that the ultraviolet absorber (B) consists solely of the ultraviolet absorber (B-1) and the ultraviolet absorber (B-2). By combining the ultraviolet absorber (B-1) and the ultraviolet absorber (B-2), the ultraviolet absorber (B-1) having an absorption maximum in the wavelength range of 300 to 360 nm sufficiently ensures the ultraviolet absorption function of the pressure-sensitive adhesive sheet, while the ultraviolet absorber (B-2) having an absorption maximum in the wavelength range of 350 to 420 nm can sufficiently absorb light in a range that does not affect the light emission of organic light-emitting diodes (OLEDs) (for example, a wavelength range of 430 nm or less). As a result, deterioration of the organic light emitting diode (OLED) due to ultraviolet rays can be suppressed.

[0075] [Ultraviolet Absorber (B-1)] Examples of the ultraviolet absorber (B-1) include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, etc. These ultraviolet absorbers (B-1) can be used alone or in combination of two or more.

[0076] Examples of the benzophenone-based ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxytrihydridolate benzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sodium sulfoxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2-hydroxy-4-n-dodecyloxybenzophenone, and 2-hydroxy-4-methoxy-2'-carboxybenzophenone.

[0077] Examples of the benzotriazole-based ultraviolet absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-3,5-dicumylphenyl)phenylbenzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert- butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-4-octoxyphenyl)benzotriazole, 2,2'-methylenebis(4-cumyl-6-benzotriazolephenyl), 2,2'-p-phenylenebis(1,3-benzoxazin-4-one, 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole, and the like.

[0078] Examples of the triazine-based ultraviolet absorber include 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-ethoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-propoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-butoxyphenyl)-4,6-diphenyl-1,3,5-triazine, and 2-(2-hydroxy-4-hexyloxyphenyl)-4,6-diphenyl-1,3,5-triazine. triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-benzyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1, 3,5-triazine, 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-tridecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[ (2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-octyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-nonyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-decyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2,4-bis[4-(2-ethylhexyloxy)-2-hydroxyphenyl]-6-(4-methoxyphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-acryloyloxyethoxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, etc.

[0079] Examples of the salicylic acid-based ultraviolet absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.

[0080] Examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate and ethyl-2-cyano-3,3'-diphenylacrylate.

[0081] Among these ultraviolet absorbers (B-1), from the viewpoint of effectively suppressing light from reaching components of the image display device, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and triazine-based ultraviolet absorbers are preferred. Furthermore, among these, from the viewpoint of excellent yellowing resistance, benzophenone-based ultraviolet absorbers and triazine-based ultraviolet absorbers are more preferred, and 2,4-bis[4-(2-ethylhexyloxy)-2-hydroxyphenyl]-6-(4-methoxyphenyl)-1,3,5-triazine is particularly preferred.

[0082] Commercially available ultraviolet absorbers (B-1) include, for example, "Tinosorb S" manufactured by BASF Japan Ltd. and "KEMISORB111" manufactured by Chemipro Kasei Co., Ltd.

[0083] [Ultraviolet Absorber (B-2)] The ultraviolet absorber (B-2) is not particularly limited as long as it is a compound having an absorption maximum at a wavelength of 350 to 420 nm, preferably at a wavelength of more than 360 nm and not more than 420 nm.

[0084] Examples of the ultraviolet absorber (B-2) include azomethine-based ultraviolet absorbers, indole-based ultraviolet absorbers, cinnamic acid-based ultraviolet absorbers, pyrimidine-based ultraviolet absorbers, porphyrin-based ultraviolet absorbers, etc. These ultraviolet absorbers (B-2) can be used alone or in combination of two or more.

[0085] Examples of the azomethine ultraviolet absorber include indoaniline, acetophenoneazomethine, pyrazoloazomethine, imidazoleazomethine, imidazoazomethine, and pyridoneazomethine.

[0086] Examples of the indole-based ultraviolet absorbers include 5-indolol, 4-aminoindole, and 4-methoxyindole.

[0087] Examples of the cinnamic acid-based ultraviolet absorbers include ethylhexyl methoxycinnamate, isopropyl methoxycinnamate, isoamyl methoxycinnamate, diisopropyl methylcinnamate, and glyceryl dimethoxycinnamate ethylhexanoate.

[0088] Examples of the pyrimidine-based ultraviolet absorbers include 2((2-(dibutylamino)-4-epoxy-6-methyl-5-pyrimidinyl)methylene)propanedinitrile.

[0089] Examples of the porphyrin-based ultraviolet absorber include magnesium meso-tetra(4-sulfonatophenyl)porphine tetrasodium salt, magnesium octaethylporphyrin, magnesium tetramesitylporphyrin, octaethylporphyrin, tetrakis(2,6-dichlorophenyl)porphyrin, tetrakis(o-aminophenyl)porphyrin, tetramesitylporphyrin, tetraphenylporphyrin, zinc octaethylporphyrin, zinc tetramesitylporphyrin, zinc tetraphenylporphyrin, and non-protonated tetraphenylporphyrin.

[0090] Among these ultraviolet absorbers (B-2), from the viewpoint of effectively suppressing light from reaching components of an image display device, those having a pyrimidine structure, i.e., pyrimidine-based ultraviolet absorbers, are preferred, and 2((2-(dibutylamino)-4-epoxy-6-methyl-5-pyrimidinyl)methylene)propanedinitrile is particularly preferred.

[0091] Examples of commercially available ultraviolet absorbers (B-2) include "FDB-009" manufactured by Yamada Chemical Industry Co., Ltd. and "BONASORB UA3912" manufactured by Orient Chemical Industry Co., Ltd.

[0092] The content of the ultraviolet absorber (B) is preferably 0.1 to 20 mass % relative to the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) from the viewpoint of ultraviolet absorption, more preferably 0.2 to 10 mass %, even more preferably 0.4 to 8 mass %, and particularly preferably 0.6 to 5 mass %.

[0093] The content ratio of the ultraviolet absorber (B-1) to the ultraviolet absorber (B-2) is, in terms of ultraviolet absorption, 30:70 to 70:30 by mass, preferably 40:60 to 60:40, and particularly preferably 45:55 to 55:45.

[0094] [Crosslinking Agent (C)] The pressure-sensitive adhesive composition preferably contains a crosslinking agent (C) in order to adjust the maximum values ​​of the storage shear modulus, glass transition temperature (Tg) and loss tangent (tan δ) at low temperatures.

[0095] Examples of the crosslinking agent (C) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, peroxide-based crosslinking agents, metal chelate-based crosslinking agents, metal alkoxide-based crosslinking agents, metal salt-based crosslinking agents, acrylic crosslinking agents, etc. These may be used alone or in combination of two or more.

[0096] When the crosslinking agent (C) is a thermal crosslinking agent that undergoes a reaction due to heat, the thermal crosslinking agent undergoes a crosslinking reaction with the (meth)acrylic polymer (P1) to form the resin component (A1). When the crosslinking agent (C) is a photocrosslinking agent that undergoes a reaction due to light, the photocrosslinking agent crosslinks with the (meth)acrylic polymer (P1) to form a polymer, and the resin component (A1) contains this polymer. Therefore, when the pressure-sensitive adhesive composition contains the crosslinking agent (C), the pressure-sensitive adhesive sheet formed from this pressure-sensitive adhesive composition contains a resin component (A) having structural units derived from the crosslinking agent (C).

[0097] As the crosslinking agent (C), it is preferable to use a crosslinking agent that has the property of being cured by irradiation with active energy rays, from the viewpoints of aging-lessness, ease of adjusting the degree of crosslinking, etc. Note that the term "crosslinking" includes not only the case where polymer chains are crosslinked via a chemical bond, but also the case where crosslinking agents are crosslinked via a chemical bond, and the case where (pseudo) crosslinking is performed by a non-covalent bond due to interactions such as hydrogen bonds, electrostatic interactions, and van der Waals forces within or between polymer chains.

[0098] The crosslinking agent (C) is preferably a compound having an ethylenically unsaturated group in the molecule, particularly preferably a (meth)acrylate, from the viewpoint of facilitating the formation of a crosslinked structure upon irradiation with active energy rays. That is, the crosslinking agent (C) is preferably an acrylic crosslinking agent.

[0099] [Acrylic Crosslinking Agent] The acrylic crosslinking agent preferably has a glass transition temperature calculated from the Fox equation of -20°C or lower, more preferably -30°C or lower, even more preferably -35°C or lower, and particularly preferably -40°C or lower. The lower limit of the glass transition temperature is usually -80°C. When the acrylic crosslinking agent has a glass transition temperature in this range, it tends to be easier to adjust the glass transition temperature of the pressure-sensitive adhesive sheet to -20°C or lower. Furthermore, the use of the acrylic crosslinking agent tends to lower the storage shear modulus at low temperatures (e.g., -20°C), making it easier to adjust the viscoelastic behavior to the desired level.

[0100] The number of ethylenically unsaturated groups contained in the molecule of the acrylic crosslinking agent is usually 1 to 20, preferably 1 to 10, more preferably 1 to 6, and particularly preferably 1 to 3, from the viewpoint of adhesive properties.

[0101] The acrylic crosslinking agent preferably has an oxyalkylene structure from the viewpoint of imparting excellent impact resistance.

[0102] Examples of the acrylic crosslinking agent include monofunctional (meth)acrylate monomers, polyfunctional (meth)acrylate monomers, and polyfunctional (meth)acrylate oligomers, etc. Among these, polyfunctional (meth)acrylate oligomers are preferred.

[0103] (Monofunctional (meth)acrylate Monomer) When the pressure-sensitive adhesive composition contains a monofunctional (meth)acrylate, the molecular weight between crosslinking points can be increased when the pressure-sensitive adhesive composition is cured, which increases the degree of freedom of movement of the molecular chain and tends to make it easier to obtain a pressure-sensitive adhesive sheet with excellent stress relaxation properties. Examples of the monofunctional (meth)acrylate monomer include ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, dextran, methyl methyl acrylate ... Cyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isododecyl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, chlorooctyl (meth)acrylate, cyclononyl (meth)acrylate, cyclodecyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecane dimethanol acrylate, ethoxylated o-phenylphenol acrylate, 2-hydroxy-o-phenylphenol propyl acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, 2-hydroxy-o-phenylphenol propyl acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl tetrahydrophthalate,2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxypropyl hydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, benzyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-naphthyl (meth)acrylate, 9-anthracenyl (meth)acrylate, 1-pyrenyl methyl acrylate, Cetyl (meth)acrylate, benzyl (meth)acrylate, tricyclodecane dimethanol monoacrylate monocarboxylic acid, dicyclopentanyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, glycerin mono(meth)acrylate, pentaerythritol Trimethylolpropane mono(meth)acrylate, diglycerin mono(meth)acrylate, ditrimethylolpropane mono(meth)acrylate, dipentaerythritol mono(meth)acrylate, ethoxylated trimethylolpropane mono(meth)acrylate, propoxylated trimethylolpropane mono(meth)acrylate, ethoxylated glycerin mono(meth)acrylate, propoxylated glycerin mono(meth)acrylate, ethoxylated pentaerythritol mono(meth)acrylate, propoxylated pentaerythritol Examples include erythritol mono(meth)acrylate, ethoxylated ditrimethylolpropane mono(meth)acrylate, propoxylated ditrimethylolpropane mono(meth)acrylate, alkylene oxide-modified diglycerin mono(meth)acrylate, and alkylene oxide-modified dipentaerythritol mono(meth)acrylate, as well as monofunctional oligomers such as monofunctional urethane (meth)acrylate, monofunctional epoxy (meth)acrylate, and monofunctional polyester (meth)acrylate. These may be used alone or in combination of two or more.

[0104] (Polyfunctional (meth)acrylate Monomer) Examples of the polyfunctional (meth)acrylate monomer include 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A Polypropoxy di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone-modified tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate Acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, (tris(acryloxyethyl)isocyanurate, dipentaerythritol hexa(meth)acrylate, dipenta Examples of the acrylate include erythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, di(meth)acrylate of an ε-caprolactone adduct of neopentyl glycol hydroxypivalate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate.Among these, from the viewpoint of imparting flexibility and appropriate toughness to the pressure-sensitive adhesive sheet and enhancing adhesiveness, polyfunctional (meth)acrylates having an alkylene glycol skeleton, such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate, are more preferred.

[0105] From the viewpoint of imparting appropriate flexibility to the pressure-sensitive adhesive sheet, the molecular weight of the polyfunctional (meth)acrylate monomer is preferably 200 or more, more preferably 300 or more, even more preferably 400 or more, and particularly preferably 500 or more. The upper limit of the molecular weight of the polyfunctional (meth)acrylate monomer is usually 3,000 or less, and preferably 2,000 or less.

[0106] (Polyfunctional (meth)acrylate oligomer) Examples of the polyfunctional (meth)acrylate oligomer include polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, polyether (meth)acrylate, etc. Among them, from the viewpoint of imparting excellent impact resistance, it is preferable that the oligomer has an oxyalkylene structure, and from the viewpoint of imparting excellent adhesiveness and impact resistance, it is preferable that the oligomer has urethane (meth)acrylate.

[0107] The urethane (meth)acrylate can be obtained by reacting a polyol, a polyisocyanate, and a hydroxyl group-containing (meth)acrylate.

[0108] The polyol may be any compound having two or more hydroxyl groups, and examples thereof include aliphatic polyols, alicyclic polyols, polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polybutadiene polyols, polyisoprene polyols, (meth)acrylic polyols, polysiloxane polyols, etc. The polyols may be used alone or in combination of two or more.

[0109] Examples of the aliphatic polyol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, dimethylolpropane, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-tetramethylenediol, 1,3-tetramethylenediol, 2-methyl-1,3-trimethylenediol, 1,5-pentamethylenediol, 1, Examples of the alcohol include aliphatic alcohols containing two hydroxyl groups such as 6-hexamethylenediol, 3-methyl-1,5-pentamethylenediol, 2,4-diethyl-1,5-pentamethylenediol, pentaerythritol diacrylate, 1,9-nonanediol, and 2-methyl-1,8-octanediol; sugar alcohols such as xylitol and sorbitol; and aliphatic alcohols containing three or more hydroxyl groups such as glycerin, trimethylolpropane, and trimethylolethane.

[0110] Examples of the alicyclic polyol include cyclohexanediols such as 1,4-cyclohexanediol and cyclohexyldimethanol, hydrogenated bisphenols such as hydrogenated bisphenol A, and tricyclodecane dimethanol.

[0111] Examples of the polyether polyol include alkylene structure-containing polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, polypentamethylene glycol, and polyhexamethylene glycol, and random or block copolymers of these polyalkylene glycols.

[0112] Examples of the polyester polyol include a condensation polymer of a polyhydric alcohol and a polycarboxylic acid, a ring-opening polymer of a cyclic ester (lactone), and a reaction product of three components: a polyhydric alcohol, a polycarboxylic acid, and a cyclic ester.

[0113] Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene diol, 1,3-tetramethylene diol, 2-methyl-1,3-trimethylene diol, 1,5-pentamethylene diol, neopentyl glycol, 1,6-hexamethylene diol, 3-methyl-1,5-pentamethylene diol, 2,4-diethyl-1,5-pentamethylene diol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediols (such as 1,4-cyclohexanediol), bisphenols (such as bisphenol A), and sugar alcohols (such as xylitol and sorbitol).

[0114] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, and trimellitic acid.

[0115] Examples of the cyclic ester include propiolactone, β-methyl-δ-valerolactone, and ε-caprolactone.

[0116] Examples of the polycarbonate polyol include a reaction product of a polyhydric alcohol with phosgene, and a ring-opening polymer of a cyclic carbonate (such as alkylene carbonate).

[0117] Examples of the polyhydric alcohol include the polyhydric alcohols exemplified in the description of the polyester polyol, and examples of the alkylene carbonate include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate.

[0118] The polycarbonate polyol may be any compound having a carbonate bond in the molecule and a hydroxyl group at the end, and may have an ester bond in addition to the carbonate bond.

[0119] Examples of the polyolefin polyol include those having a homopolymer or copolymer of ethylene, propylene, butene, or the like as a saturated hydrocarbon skeleton and having hydroxyl groups at the molecular terminals.

[0120] The polybutadiene polyol may be, for example, a polybutadiene polyol having a butadiene copolymer as a hydrocarbon skeleton and hydroxyl groups at its molecular terminals. The polybutadiene polyol may be a hydrogenated polybutadiene polyol in which all or part of the ethylenically unsaturated groups contained in the polybutadiene polyol structure have been hydrogenated.

[0121] The polyisoprene-based polyol may be, for example, a polyisoprene-based polyol having an isoprene copolymer as a hydrocarbon skeleton and hydroxyl groups at its molecular terminals. The polyisoprene-based polyol may be a hydrogenated polyisoprene polyol in which all or part of the ethylenically unsaturated groups contained in the polyisoprene-based polyol structure have been hydrogenated.

[0122] Examples of the (meth)acrylic polyol include those having at least two hydroxyl groups in the molecule of a polymer or copolymer of alkyl (meth)acrylate, and examples of such alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate.

[0123] Examples of the polysiloxane polyol include dimethylpolysiloxane polyol and methylphenylpolysiloxane polyol.

[0124] Among these polyols, polyether polyols are preferred from the viewpoint of obtaining excellent impact resistance, and polyethylene glycol, polypropylene glycol, and polytetramethylene glycol are particularly preferred.

[0125] The polyisocyanate may be any compound having two or more isocyanate groups, and examples thereof include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; pentamethylene diisocyanate, hexamethylene diisocyanate; and trimethylsilyl diisocyanate. Examples of the polyisocyanate include aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, and lysine triisocyanate, alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate, trimer compounds or polymer compounds of these polyisocyanates, allophanate polyisocyanates, biuret polyisocyanates, and water-dispersible polyisocyanates. The polyisocyanates can be used alone or in combination of two or more.

[0126] Among these, diisocyanates are preferred from the viewpoint of stability during the urethanization reaction, more preferably aliphatic diisocyanates such as pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, and alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, and even more preferably isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and norbornene diisocyanate from the viewpoint of small cure shrinkage, and particularly preferably hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate from the viewpoint of excellent reactivity and versatility.

[0127] The hydroxyl group-containing (meth)acrylate is a compound having a hydroxyl group and a (meth)acryloyl group, and the number of hydroxyl groups is preferably 1 to 5, and particularly preferably 1.

[0128] Examples of the hydroxyl group-containing (meth)acrylate include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethyl acryloyl phosphate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, dipropylene glycol mono(meth)acrylate, fatty acid-modified glycidyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, and dimethylolcyclohexyl (meth)acrylate. hydroxyl-containing (meth)acrylates containing one (meth)acryloyl group, such as hydroxycaprolactone (meth)acrylate; hydroxyl-containing (meth)acrylates containing two (meth)acryloyl groups, such as glycerin di(meth)acrylate and 2-hydroxy-3-acryloyl-oxypropyl methacrylate; and hydroxyl-containing (meth)acrylates containing three or more (meth)acryloyl groups, such as pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified dipentaerythritol penta(meth)acrylate. These may be used alone or in combination of two or more.

[0129] Among these, hydroxyl group-containing (meth)acrylates containing two or less (meth)acryloyl groups are preferred, more preferably compounds containing one (meth)acryloyl group such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, dimethylolcyclohexyl mono(meth)acrylate, and hydroxycaprolactone (meth)acrylate, and particularly preferably hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0130] Among the urethane (meth)acrylates obtained by reacting the polyol, polyisocyanate, and hydroxyl group-containing (meth)acrylate, from the viewpoints of achieving a low glass transition temperature, an increased loss tangent (Tan δ), and excellent impact resistance, polyfunctional urethane (meth)acrylates having an oxyalkylene structure are preferred, more preferred are polyfunctional urethane acrylates having a polypropylene glycol skeleton, and even more preferred are polyfunctional urethane (meth)acrylates obtained by reacting 2-hydroxyethyl acrylate, isophorone diisocyanate, and polypropylene glycol diacrylate.

[0131] The weight average molecular weight of the polyfunctional (meth)acrylate oligomer is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, particularly preferably 8,000 or more, and especially preferably 10,000 or more, since a pressure-sensitive adhesive sheet having appropriate flexibility can be obtained. The upper limit of the molecular weight is usually 100,000, and preferably 50,000.

[0132] The content of the crosslinking agent (C) is typically 1 to 50 parts by mass, preferably 2 to 40 parts by mass, more preferably 3 to 35 parts by mass, and particularly preferably 5 to 30 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (P1). By controlling the content of the crosslinking agent (C) within this range, it tends to be possible to reduce the storage shear modulus at low temperatures, increase the maximum value of the loss tangent (tan δ), and adjust the viscoelasticity to the desired level. Furthermore, the pressure-sensitive adhesive sheet preferably contains structural units derived from the crosslinking agent (C) in an amount of 1 to 50% by mass, more preferably 2 to 40% by mass, even more preferably 3 to 35% by mass, and particularly preferably 5 to 30% by mass, relative to the pressure-sensitive adhesive sheet. By controlling the content of the structural units derived from the crosslinking agent (C) within this range, it tends to be possible to reduce the storage shear modulus at low temperatures, increase the maximum value of the loss tangent (tan δ), and adjust the viscoelasticity to the desired level.

[0133] [Photoinitiator (D)] The pressure-sensitive adhesive composition preferably further contains a photoinitiator (D). The photoinitiator (D) is a compound that generates radicals when exposed to active energy rays, such as ultraviolet light or visible light, more specifically, compounds that generate active radical species when exposed to light with a wavelength of 200 to 780 nm. Among these, from the viewpoint of photoreactivity, photoinitiators that absorb at wavelengths of 405 nm or more are preferred, and photoinitiators that have a molar absorption coefficient at a wavelength of 405 nm of 30 (L / mol cm) or more are particularly preferred. The photoinitiators (D) can be used alone or in combination of two or more.

[0134] The photoinitiator (D) is broadly classified into two types based on the radical generation mechanism. More specifically, it is broadly classified into cleavage-type photoinitiators, which can generate radicals by cleaving and decomposing the single bond of the photoinitiator itself, and hydrogen-abstraction-type photoinitiators, which can generate radicals by an excited photoinitiator abstracting hydrogen from a hydrogen donor in the system. The photoinitiator (D) can be either a cleavage-type photoinitiator or a hydrogen-abstraction-type photoinitiator, but cleavage-type photoinitiators are preferred in terms of their particularly high photosensitivity. On the other hand, hydrogen-abstraction-type photoinitiators are preferred in that they do not generate photodecomposition products like cleavage-type photoinitiators. Furthermore, hydrogen-abstraction-type photoinitiators are also preferred in that they cause a hydrogen abstraction reaction from the (meth)acrylic polymer (P1), which incorporates the (meth)acrylic polymer (P1) into the crosslinked structure, making it easier to form a crosslinked structure with many crosslinking points.

[0135] The hydrogen abstraction photoinitiators are roughly classified into intermolecular hydrogen abstraction photoinitiators that abstract hydrogen from other molecules, and intramolecular hydrogen abstraction photoinitiators that also cause a hydrogen abstraction reaction within the same molecule.

[0136] Specific examples of the hydrogen abstraction type photoinitiator include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, methyl 2-benzoylbenzoate, 4-[(4-methylphenyl)thio]benzophenone, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, intermolecular hydrogen abstraction photoinitiators such as benzoylformate, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, and 4-methacryloyloxyethoxy-4'-bromobenzophenone; and intramolecular hydrogen abstraction photoinitiators such as methyl benzoylformate, oxyphenylacetic acid-2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl ester, oxyphenylacetic acid-2-(2-hydroxy-ethoxy)ethyl ester, and dimethyl 2,2'-(thiobis(4,1-phenylene))bis(2-octoacetate).

[0137] Among these, those having absorption at wavelengths of 405 nm or more, such as methyl benzoylformate, oxyphenylacetic acid 2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl ester, oxyphenylacetic acid 2-(2-hydroxy-ethoxy)ethyl ester, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, and dimethyl 2,2′-(thiobis(4,1-phenylene))bis(2-octoacetate) are preferred. Among these, intramolecular hydrogen abstraction photoinitiators such as methyl benzoylformate, oxyphenylacetic acid-2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl ester, oxyphenylacetic acid-2-(2-hydroxy-ethoxy)ethyl ester, and dimethyl 2,2′-(thiobis(4,1-phenylene))bis(2-octoacetate) are preferred because they not only act as hydrogen donors in the system but also themselves can serve as starting points for radical generation.

[0138] Examples of the cleavage-type photoinitiator include benzyl ketal-based photoinitiators such as 2,2-dimethoxy-1,2-diphenylethan-1-one, α-hydroxyacetophenone-based photoinitiators such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one, and oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), and 2-benzyl-2-dimethylamino-1-(4-morpho-2-methyl-propanone). Examples of the photoinitiator include α-aminoacetophenone-based photoinitiators such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone; phosphine oxide-based photoinitiators such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide; and derivatives thereof.

[0139] Among these, α-aminoacetophenone-based initiators such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, which have absorption at wavelengths of 405 nm or more, and phosphine oxide-based initiators such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide are preferred, and phosphine oxide-based photoinitiators are preferred from the viewpoint of decomposition and discoloration after photoreaction.

[0140] When the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) contains a photoinitiator (D), the content thereof is usually 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass, and particularly preferably 0.3 to 3 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (P1). When the content of the photoinitiator (D) is within this range, a good crosslinking reaction tends to proceed.

[0141] [Other Components] The pressure-sensitive adhesive composition may contain, as needed, various additives such as silane coupling agents, plasticizers, tackifying resins, antioxidants, light stabilizers, metal deactivators, anti-aging agents, moisture absorbents, rust inhibitors, and inorganic particles as "other components" as long as the effects of the present invention are not impaired. Furthermore, the pressure-sensitive adhesive composition may contain, as needed, reaction catalysts such as tertiary amine compounds, quaternary ammonium compounds, and tin laurate compounds. These may be used alone or in combination of two or more.

[0142] [Silane coupling agent] The silane coupling agent is an organosilicon compound that contains one or more reactive functional groups and one or more alkoxy groups bonded to silicon atoms in its structure.The reactive functional groups include, for example, epoxy group, (meth)acryloyl group, mercapto group, hydroxyl group, carboxy group, amino group, amide group, and isocyanate group.Among these, epoxy group and mercapto group are preferred from the viewpoint of balance of durability.

[0143] The alkoxy group bonded to the silicon atom preferably contains an alkoxy group having 1 to 8 carbon atoms from the viewpoint of durability and storage stability, and is particularly preferably a methoxy group or an ethoxy group. The silane coupling agent may also have an organic substituent other than the reactive functional group and the alkoxy group bonded to the silicon atom, such as an alkyl group or a phenyl group.

[0144] Specific examples of the silane coupling agent include monomeric epoxy group-containing silane coupling agents, which are silane compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and silane coupling agents in which a portion of the silane compound is hydrolyzed and condensed, or silane compounds in which the silane compound is polymerized with methyltriethoxysilane, ethyltriethoxysilane, or methyltriethoxysilane. oligomeric epoxy group-containing silane coupling agents which are silane compounds obtained by co-condensation of alkyl group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane, and monomeric mercapto group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, and mercapto groups which are silane compounds obtained by hydrolysis and condensation polymerization of a part of the silane compounds or by polymerization of the silane compounds with the mercapto groups. Oligomeric mercapto group-containing silane coupling agents which are silane compounds obtained by co-condensation of alkyl group-containing silane compounds such as ethyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane; (meth)acryloyl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; coupling agents: amino group-containing silane coupling agents such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane;Examples of suitable silane coupling agents include vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane. These may be used alone or in combination of two or more.

[0145] Among these, epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used because of their excellent durability, and among these, epoxy group-containing silane coupling agents are particularly preferred.

[0146] When the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) contains a silane coupling agent, the content thereof is usually 0.005 to 10 parts by mass, preferably 0.01 to 5 parts by mass, and particularly preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the (meth)acrylic polymer (P1). When the content of the silane coupling agent is equal to or greater than the lower limit, durability tends to be improved, whereas when the content is equal to or less than the upper limit, durability tends to be improved.

[0147] [Plasticizer] The pressure-sensitive adhesive composition may contain a plasticizer to impart flexibility to the pressure-sensitive adhesive sheet.

[0148] The plasticizer is not particularly limited, but may be selected from the group consisting of polyisobutylene, polyisoprene, polybutadiene, amorphous polyolefins and copolymers thereof, silicone, polyacrylate, oligomeric polyurethane, ethylene propylene copolymer, and any combination or mixture thereof. Among these, polyisobutylene is preferred as the plasticizer.

[0149] The polyisobutylene may be, for example, one selected from the OPPANOLB series, which is commercially available from BASF under the trade name OPPANOL.

[0150] From the viewpoint of environmental protection, the plasticizer preferably has a lower volatile organic compound (VOC) value, which is usually less than 1000 ppm, preferably less than 800 ppm, more preferably less than 600 ppm, and particularly preferably 400 ppm. The volatile organic compound (VOC) value can be measured by thermogravimetric analysis.

[0151] When the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) contains a plasticizer, the content thereof is not particularly limited, but is usually 0.1 to 20 parts by mass, and preferably 0.5 to 15 parts by mass, per 100 parts by mass of the (meth)acrylic polymer (P1).

[0152] [Tackifier] The pressure-sensitive adhesive composition may contain a tackifier in order to improve the adhesive strength of the pressure-sensitive adhesive sheet.

[0153] Examples of the tackifier include terpene resins such as polyterpenes (e.g., α-pinene resins, β-pinene resins, and limonene resins) and aromatic-modified polyterpene resins (e.g., phenol-modified polyterpene resins); petroleum-based resins such as coumaran-indene resins, C5 hydrocarbon resins, C9 hydrocarbon resins, C5 / C9 hydrocarbon resins, and dicyclopentadiene resins; and rosins such as modified rosin, hydrogenated rosin, polymerized rosin, and rosin esters.

[0154] When the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) contains a tackifier, the content thereof is not particularly limited and is usually 0.1 to 20 parts by mass, and preferably 0.5 to 15 parts by mass, per 100 parts by mass of the (meth)acrylic polymer (P1).

[0155] [Rust inhibitor] The pressure-sensitive adhesive composition may contain a rust inhibitor to prevent corrosion when the adherend contains a corrosive portion such as a metal wiring.

[0156] Examples of the rust inhibitor include triazoles and benzotriazoles.

[0157] When the pressure-sensitive adhesive composition (pressure-sensitive adhesive sheet) contains a rust inhibitor, the content thereof is usually 0.01 to 5 parts by mass, and preferably 0.1 to 3 parts by mass, per 100 parts by mass of the (meth)acrylic polymer (P1).

[0158] [Method for producing the present pressure-sensitive adhesive sheet by method 1] Next, a method for producing the present pressure-sensitive adhesive sheet by method 1 will be described. However, the following description is an example of a method for producing the present pressure-sensitive adhesive sheet, and the present pressure-sensitive adhesive sheet is not limited to sheets produced by this production method.

[0159] In producing the present pressure-sensitive adhesive sheet, the above-mentioned pressure-sensitive adhesive composition is prepared, the pressure-sensitive adhesive composition is formed into a sheet, cured by irradiation with active energy rays, and then processed appropriately as necessary to produce the present pressure-sensitive adhesive sheet.

[0160] In addition, in producing the present pressure-sensitive adhesive sheet, the present pressure-sensitive adhesive sheet may be formed by preparing a pressure-sensitive adhesive composition for forming the present pressure-sensitive adhesive sheet in the same manner as described above, coating this onto a component of an image display device, and curing the pressure-sensitive adhesive composition, although the method is not limited to this.

[0161] When preparing the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive sheet, the components may be mixed using a propeller stirrer or kneader (e.g., a single-screw extruder, a twin-screw extruder, a planetary mixer, a twin-screw mixer, a pressure kneader, etc.). When mixing the various components, various additives such as a silane coupling agent and an antioxidant may be blended together with the (meth)acrylic polymer (P1) in advance and then fed to the stirrer or kneader, or all materials may be melt-mixed in advance and then fed, or a masterbatch in which only the additives are concentrated in the (meth)acrylic polymer (P1) may be prepared and then fed.

[0162] The pressure-sensitive adhesive composition can be formed into a sheet by any known method, such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendaring, inflation, injection molding, and liquid injection curing. Among these, when producing a sheet, wet lamination, extrusion casting, and extrusion lamination are preferred.

[0163] The pressure-sensitive adhesive composition can be cured by irradiation with active energy rays, and the pressure-sensitive adhesive sheet can be produced by irradiating a molded product of the pressure-sensitive adhesive composition, for example, a sheet, with active energy rays. In addition to irradiation with active energy rays, further curing can be achieved by heating.

[0164] The irradiation energy, irradiation time, irradiation method, etc. of the active energy rays are not particularly limited as long as they can activate the photoinitiator (D) and polymerize the monomer components.

[0165] Examples of the active energy rays in the active energy ray irradiation include light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, and visible light rays, as well as ionizing radiation such as X-rays, α-rays, β-rays, γ-rays, electron beams, proton beams, and neutron beams. Among these, ultraviolet rays or visible light rays are preferred from the viewpoints of suppressing damage to components of the image display device and facilitating reaction control. Furthermore, curing by irradiation with ultraviolet rays or visible light rays is advantageous from the viewpoints of curing speed, ease of availability of irradiation equipment, cost, and the like. Among these, curing by visible light rays, for example, active energy rays of 405 nm, is preferred from the viewpoint of preventing curing inhibition by ultraviolet absorbers.

[0166] Examples of light sources for irradiating active energy rays include high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, and LEDs, all of which emit light in the wavelength range of 150 to 450 nm.

[0167] The amount of active energy ray irradiation (cumulative light amount) is 10 to 6000 mJ / cm from the viewpoint of curing. 2 is preferred, and 50 to 5500 mJ / cm 2 More preferably, 100 to 5000 mJ / cm 2 is more preferably 200 to 4000 mJ / cm 2 The following is particularly preferred: 300 to 3000 mJ / cm 2 When the pressure-sensitive adhesive sheet is irradiated with active energy rays from both sides, the amount of active energy ray irradiation is the sum of the integrated energy on one side and the integrated energy on the other side.

[0168] The present pressure-sensitive adhesive sheet may also be active energy ray-curable. "The pressure-sensitive adhesive sheet is active energy ray-curable" means that the pressure-sensitive adhesive sheet has the property of being curable by active energy rays, in other words, that the pressure-sensitive adhesive sheet has room to be cured by active energy rays.

[0169] That is, the present pressure-sensitive adhesive sheet may be one in which the pressure-sensitive adhesive composition has been cured to a state in which there is still room for the pressure-sensitive adhesive composition to be cured by active energy rays (hereinafter also referred to as "primary curing"), or one in which the pressure-sensitive adhesive composition has been crosslinked (primary curing) by a thermal crosslinking agent and can be cured by active energy rays.

[0170] When the pressure-sensitive adhesive sheet is primarily cured, it may be primarily cured by heat or by active energy rays, but from the viewpoint of making it easier to control the gel fraction within a predetermined range, it is preferable that the pressure-sensitive adhesive sheet is primarily cured by irradiation with active energy rays.

[0171] When the pressure-sensitive adhesive sheet has active energy ray curability, that is, when the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet that has room to be cured by active energy rays and the pressure-sensitive adhesive sheet is subjected to primary curing by active energy rays, the cumulative irradiation amount at a wavelength of, for example, 405 nm is usually 10 to 5000 mJ / cm 2 , preferably 50 to 4000 mJ / cm 2 , more preferably 100 to 3000 mJ / cm 2 , more preferably 200 to 2500 mJ / cm 2 , particularly preferably 300 to 2000 mJ / cm 2 If the amount of irradiation is within the above range, it tends to be possible to adjust the degree of cure while leaving room for further cure.

[0172] In another embodiment of the method for producing the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive composition can be dissolved in an appropriate solvent and then coated using various coating techniques.

[0173] For example, the pressure-sensitive adhesive composition can be dissolved in a solvent, coated on a release film, dried, and cured by active energy ray irradiation to form the pressure-sensitive adhesive sheet. Furthermore, a release film may be laminated, if necessary. In this case, the pressure-sensitive adhesive composition may be coated on a release film, dried, cured by active energy ray irradiation, and a release film may be laminated thereon. Alternatively, the pressure-sensitive adhesive sheet may be formed by coating on a release film, drying, laminating a release film, and then curing by active energy ray irradiation.

[0174] The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition, and examples thereof include ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, and ethyl acetoacetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic solvents such as toluene and xylene; and alcohol solvents such as methanol, ethanol, and propyl alcohol. These can be used alone or in combination of two or more. Among them, ethyl acetate, acetone, methyl ethyl ketone, and toluene are preferred in terms of solubility, drying properties, cost, and the like, and ethyl acetate is particularly preferred.

[0175] In view of drying properties, the content of the solvent is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 400 parts by mass or less, and particularly preferably 300 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymer (P1). On the other hand, it is preferably 1 part by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 150 parts by mass or more. Coating can be performed by a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, or bar coating.

[0176] Drying methods include, for example, drying with a dryer, drying with a heated roll, and drying by blowing hot air onto the film. Among these, using a dryer is preferred because it allows for uniform and easy drying. These methods can be used alone or in combination of two or more.

[0177] The drying temperature is usually 40 to 150° C., more preferably 45 to 140° C., even more preferably 50 to 130° C., and particularly preferably 55 to 120° C. When the temperature is within this range, the solvent can be removed efficiently and relatively safely while suppressing thermal deformation of the release film.

[0178] The drying time is usually 1 to 30 minutes, more preferably 3 to 25 minutes, and even more preferably 5 to 20 minutes. When the drying time is within this range, the solvent can be removed efficiently and sufficiently.

[0179] The solvent content in the pressure-sensitive adhesive composition after drying is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

[0180] Furthermore, the present pressure-sensitive adhesive sheet may be a single-layer sheet consisting of only an adhesive layer formed from the pressure-sensitive adhesive composition, or a multi-layer sheet in which multiple adhesive layers formed from the pressure-sensitive adhesive composition are laminated.

[0181] <Adhesive Sheet with Release Film> The present adhesive sheet can also be provided as an adhesive sheet with a release film (adhesive sheet laminate) by laminating a release film on one or both sides of the adhesive layer (the present adhesive sheet) made of the adhesive composition.

[0182] When release films are provided on both sides of the present pressure-sensitive adhesive sheet, it is preferable to use a laminate configuration in which a light-release film with a relatively low release strength and a heavy-release film with a relatively high release strength are laminated together. When using a pressure-sensitive adhesive sheet with release films provided on both sides, first, one release film (light-release film) is peeled off to expose one side of the pressure-sensitive adhesive sheet, and then a component of an image display device (referred to as the first component) is attached to the other side of the pressure-sensitive adhesive sheet exposed by peeling off the other release film (heavy-release film), and then a component of a flexible image display device (referred to as the second component) is attached to the other side of the pressure-sensitive adhesive sheet.

[0183] As such a release film, a known release film can be appropriately used. Examples of the material for the release film include films such as polyester films, polyolefin films, polycarbonate films, polystyrene films, acrylic films, triacetyl cellulose films, and fluororesin films that have been subjected to a release treatment by coating with a release agent such as silicone resin, and release paper, etc., and these can be appropriately selected and used. Among these, polyester films, and even more particularly polyethylene terephthalate (PET) films, particularly biaxially oriented PET films, are preferred because of their excellent transparency, mechanical strength, heat resistance, flexibility, etc. A release film can be used in which a release layer formed by curing a curable silicone-based release agent containing silicone resin as the main component is provided on the substrate.

[0184] The thickness of the release film is not particularly limited. In particular, from the viewpoint of processability and handling, the thickness is preferably 10 to 250 μm, more preferably 25 to 200 μm, and even more preferably 35 to 190 μm.

[0185] <Second Method> In the second method, the present PSA sheet is obtained from a syrup composition containing a syrup component and an ultraviolet absorber (B). Hereinafter, each component contained in the syrup composition will be described.

[0186] [Syrup Component] The syrup component preferably contains a monomer component containing an alkyl(meth)acrylate (a1) and one or more copolymerizable monomers copolymerizable therewith selected from the group consisting of a carboxyl group-containing monomer (a2), a hydroxyl group-containing monomer (a3), a nitrogen-containing monomer (a4), an epoxy group-containing monomer (a5), a vinyl monomer (a6), an alkyl(meth)acrylate monomer (a7) having an alkyl group of 1 to 3 carbon atoms, an alicyclic monomer (a8), and other copolymerizable monomers (a9).

[0187] Among the copolymerizable monomers (a2) to (a9), the carboxyl group-containing monomer (a2), the hydroxyl group-containing monomer (a3), and the nitrogen-containing monomer (a4) are particularly preferred. Furthermore, it is particularly preferred that the copolymer does not contain the carboxyl group-containing monomer (a2) but contains either the hydroxyl group-containing monomer (a3) ​​or the nitrogen-containing monomer (a4). By including either the hydroxyl group-containing monomer (a3) ​​or the nitrogen-containing monomer (a4), corrosion resistance, adhesiveness, and resistance to wet heat whitening can be achieved when the adherend contains a corrosive component such as a metal. Furthermore, it is particularly preferred that the copolymer contains both the hydroxyl group-containing monomer (a3) ​​and the nitrogen-containing monomer (a4) in order to enhance cohesion.

[0188] The syrup component may also be composed of the (meth)acrylic polymer (P1) described in the first method and a monomer component. In one example, such a syrup component may be formed by partial polymerization of the so-called monomer component, or may be prepared by adding the monomer component to a polymer in which the monomer components constituting the (meth)acrylic polymer (P1) are completely or partially polymerized. That is, when a predetermined polymerization component is partially polymerized, some of the monomers are polymerized to form a polymer, while some of the monomers remain, thereby forming the syrup component. In another example, the syrup component can also be obtained by adding the monomer component to a partially or completely polymerized polymer.

[0189] [Alkyl(meth)acrylate (a1)] Examples of the alkyl(meth)acrylate (a1) include the alkyl(meth)acrylate (a1) described in the first method, and the types of preferred monomers and the like are also the same as those of the alkyl(meth)acrylate (a1) described in the first method.

[0190] The content of the alkyl (meth)acrylate (a1) is preferably 5 to 95% by mass, more preferably 10 to 90% by mass, even more preferably 15 to 85% by mass, and particularly preferably 20 to 80% by mass, relative to the syrup composition (adhesive sheet) in terms of flexibility. When the content of the structural unit derived from the alkyl (meth)acrylate (a1) is equal to or greater than the lower limit, excellent resistance to foaming at the peripheral edge during lamination is achieved, and when it is equal to or less than the upper limit, adhesiveness and other physical properties can be achieved at the same time.

[0191] [Carboxy Group-Containing Monomer (a2)] Examples of the carboxy group-containing monomer (a2) include the carboxy group-containing monomer (a2) described in the first method, and the preferred types of monomers are also the same as those for the carboxy group-containing monomer (a2) described in the first method.

[0192] When the syrup composition contains the carboxy group-containing monomer (a2), the content thereof is usually 0.1 to 15 mass %, preferably 0.3 to 13 mass %, more preferably 0.5 to 10 mass %, and particularly preferably 1 to 6 mass %, based on the syrup composition.

[0193] [Hydroxyl Group-Containing Monomer (a3)] Examples of the hydroxyl group-containing monomer (a3) ​​include the hydroxyl group-containing monomer (a3) ​​described in the first method, and the preferred types of monomers are also the same as those for the hydroxyl group-containing monomer (a3) ​​described in the first method.

[0194] When the syrup composition contains the hydroxyl group-containing monomer (a3), the content thereof is usually 3 to 30 mass %, preferably 5 to 25 mass %, and particularly preferably 7 to 20 mass %, based on the syrup composition.

[0195] [Nitrogen-Containing Monomer (a4)] Examples of the nitrogen-containing monomer (a4) include the nitrogen-containing monomer (a4) described in the first method, and the types of preferred monomers are also the same as those of the nitrogen-containing monomer (a4) described in the first method.

[0196] When the syrup composition contains the nitrogen-containing monomer (a4), the content thereof is usually 0.1 to 15 mass %, preferably 0.5 to 13 mass %, particularly preferably 1 to 10 mass %, and especially preferably 2 to 7 mass %, based on the syrup composition.

[0197] The syrup composition may contain the copolymerizable monomers (a5) to (a9) described in the first method. The types of these preferred monomers are the same as those described in the first method. The content of these copolymerizable monomers (a5) to (a9), i.e., the mass ratio relative to the syrup composition, is the same as the mass ratio relative to 100 mass% of the structural units of the (meth)acrylic polymer (P1) described in the first method.

[0198] [Ultraviolet absorber (B)] The ultraviolet absorber (B) comprises an ultraviolet absorber (B-1) having an absorption maximum in the wavelength region of 300 to 360 nm, and an ultraviolet absorber (B-2) other than (B-1) having an absorption maximum in the wavelength region of 350 to 420 nm. It is particularly preferred that the ultraviolet absorber (B) consists solely of the ultraviolet absorber (B-1) and the ultraviolet absorber (B-2).

[0199] The preferred compounds and physical properties of the ultraviolet absorbers (B-1) and (B-2) are the same as those explained in the first method.

[0200] The content of the ultraviolet absorber (B) is preferably 0.1 to 20 mass % relative to the syrup composition (adhesive sheet) from the viewpoint of ultraviolet absorption, more preferably 0.2 to 10 mass %, even more preferably 0.4 to 8 mass %, and particularly preferably 0.6 to 5 mass %.

[0201] The content ratio of the ultraviolet absorber (B-1) to the ultraviolet absorber (B-2) is, in terms of ultraviolet absorption, 30:70 to 70:30 by mass, preferably 40:60 to 60:40, and particularly preferably 45:55 to 55:45.

[0202] Furthermore, the syrup composition preferably contains the crosslinking agent (C) and photoinitiator (D) described in the first method above, and may also contain other components such as a silane coupling agent, as described in the first method above.

[0203] [Crosslinking Agent (C)] When the syrup composition contains a crosslinking agent (C), the crosslinking agent (C) undergoes a crosslinking reaction with the syrup component to form a resin component (A2). That is, when the syrup component contains a crosslinking agent (C), the resulting resin component (A2) has structural units derived from the crosslinking agent (C). When the crosslinking agent (C) is used, the preferred compounds and physical properties are the same as those of the crosslinking agent (C) described in the first method.

[0204] The preferred content of the crosslinking agent (C) is typically 0.1 to 30% by mass, preferably 1 to 25% by mass, and particularly preferably 5 to 20% by mass, relative to the syrup composition (pressure-sensitive adhesive sheet). By setting the content of the crosslinking agent (C) within this range, it tends to be possible to reduce the storage shear modulus at low temperatures, increase the maximum value of the loss tangent (tan δ), and adjust the viscoelasticity to the desired level.

[0205] [Photoinitiator (D)] The photoinitiator is not particularly limited as long as it is a photoinitiator described in the first method above, but from the viewpoint of efficiently progressing the polymerization reaction, it is preferable to include a cleavage-type photoinitiator, and among the cleavage-type photoinitiators described above, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide are particularly preferred. Furthermore, from the viewpoint of efficiently forming a crosslinked structure, it is preferable to include a hydrogen abstraction-type photoinitiator, and benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, and 4-(meth)acryloyloxybenzophenone are particularly preferred. The photoinitiator may include two or more selected from the group consisting of cleavage-type photoinitiators and / or hydrogen abstraction-type photoinitiators.

[0206] When the photoinitiator (D) is used, its content is usually 0.1 to 10% by mass, preferably 0.5 to 6% by mass, and more preferably 1 to 4% by mass, based on the syrup composition (adhesive sheet). If the content of the photoinitiator (D) is within this range, a good crosslinking reaction tends to proceed.

[0207] [Other Components] The other components may be the same as those described in the first method. In particular, when a silane coupling agent is used, its content is usually 0.005 to 5% by mass, preferably 0.01 to 3% by mass, and more preferably 0.05 to 1% by mass, based on the syrup composition (adhesive sheet). When the content is within the above range, adhesive strength and durability tend to be improved.

[0208] [Method for producing the present pressure-sensitive adhesive sheet by the second method] Next, a method for producing the present pressure-sensitive adhesive sheet by the second method will be described. However, the following description is merely an example of a method for producing the present pressure-sensitive adhesive sheet, and the present pressure-sensitive adhesive sheet is not limited to sheets produced by this method.

[0209] In producing the present pressure-sensitive adhesive sheet, the aforementioned syrup composition is prepared and then irradiated with active energy rays to cause prepolymerization. Subsequently, the syrup composition, to which additional photoinitiator (D), crosslinking agent (C), and other components are added as needed, is coated onto a release film or the like using various coating methods, and then the syrup composition is irradiated with active energy rays or heated to cure the syrup component and crosslinking agent (C) into resin component (A2), thereby producing the present pressure-sensitive adhesive sheet. The crosslinking agent (C) and other components may be added to the syrup composition from the beginning, or may be added to the syrup composition after prepolymerization has been completed. Furthermore, in producing the present pressure-sensitive adhesive sheet, prepolymerization and curing may be performed in a single step.

[0210] In another embodiment of the method for producing the present adhesive sheet, the present adhesive sheet can be produced by dissolving the syrup composition in a solvent, coating it on a release film, drying it, and then prepolymerizing and curing it by irradiating it with active energy rays.

[0211] In the method for producing the pressure-sensitive adhesive sheet, the release film, active energy rays, solvent, etc., as well as the mixing method, coating method, drying conditions, etc. may be the same as those explained in the first method.

[0212] The present PSA sheet obtained by such a second method may be a single-layer sheet having only a PSA layer made of the syrup composition, or a multi-layer sheet having a PSA layer made of the syrup composition and / or a plurality of other PSA layers laminated together. The present PSA sheet may also be provided as a PSA sheet with a release film, which has a configuration in which a release film is laminated on one or both sides of the PSA layer made of the syrup composition.

[0213] [Preferred Uses of the Present Pressure-Sensitive Adhesive Sheet] The present pressure-sensitive adhesive sheet is preferably used for bonding optical components. Specifically, it is preferably used for bonding components constituting a display, particularly components used in producing a display, and is particularly preferably used as a pressure-sensitive adhesive sheet for an organic light-emitting diode (OLED) display device. Specifically, it is used as a pressure-sensitive adhesive sheet for bonding an image display panel and image display device components such as a protective panel or touch panel arranged on the front side (viewing side) of the image display panel, or components constituting the image display device components. Note that the same image display device components as those described below can be used.

[0214] <Laminate for image display device> A laminate for an image display device according to one example of an embodiment of the present invention (hereinafter, may be referred to as "the present laminate for image display device") is a laminate for an image display device having a configuration in which two optical members are laminated via the present pressure-sensitive adhesive sheet.

[0215] Of the components of the laminate for an image display device, the pressure-sensitive adhesive sheet has been described above, and the components other than the pressure-sensitive adhesive sheet will be described below.

[0216] <Optical Component> Examples of optical components constituting the present laminate for image display devices include components of flat panel image display devices and components of flexible image display devices. Examples of such image display device components include flexible displays such as liquid crystal displays and organic electroluminescence (EL) displays, cover lenses (cover films), polarizing plates, polarizers, retardation films, barrier films, viewing angle compensation films, brightness enhancement films, contrast enhancement films, diffusion films, semi-transmitting reflective films, electrode films, transparent conductive films, metal mesh films, and touch sensor films. Any one of these may be used alone or in combination. Examples include a combination of a flexible display and another optical component, or a combination of a cover lens and another optical component.

[0217] The flexible image display device component is a bendable component, and refers to a component used in an image display device having a curved surface or a component that can be repeatedly bent. In particular, it is preferable that the component be a component that can be fixed to a curved shape with a curvature radius of 25 mm or more, and particularly a component that can withstand bending action with a curvature radius of less than 25 mm, more preferably less than 3 mm.

[0218] In the above-described configuration, examples of materials constituting the optical member include resin sheets and glass. Examples of materials for such resin sheets include polyester resins, cycloolefin resins, triacetyl cellulose resins, polymethyl methacrylate resins, polyurethanes, epoxy resins, polyimide resins, and aramid resins. These may be one type of resin or two or more types of resins. Among these, a resin sheet containing at least one resin selected from the group consisting of polyester resins, cycloolefin resins, triacetyl cellulose resins, polymethyl methacrylate resins, epoxy resins, polyimide resins, aramid resins, and polyurethane resins as a primary component is preferred. Here, the term "primary component" refers to the component that accounts for the largest mass ratio among the components constituting the optical member. Specifically, the component accounts for 50% by mass or more of the resin composition (resin sheet) forming the optical member, preferably 55% by mass or more, and particularly preferably 60% by mass or more.

[0219] [Method for manufacturing the present laminate for an image display device] The method for manufacturing the present laminate for an image display device is not particularly limited, and as described above, for example, a pressure-sensitive adhesive sheet may be formed by applying the pressure-sensitive adhesive composition onto an optical member, or a pressure-sensitive adhesive sheet with a release film may be formed in advance and then laminated to the optical member.

[0220] <Image display device> An image display device according to an embodiment of the present invention (hereinafter, sometimes referred to as "the image display device") is an image display device incorporating a laminate for an image display device having a configuration in which two optical members are bonded together via the present pressure-sensitive adhesive sheet. For example, the image display device including the laminate can be formed by laminating the laminate for an image display device having a configuration in which two optical members are bonded together via the present pressure-sensitive adhesive sheet onto another optical member.

[0221] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0222] First, the components of the pressure-sensitive adhesive compositions prepared in the examples will be described in detail.

[0223] [(Meth)acrylic polymer (P1)] An acrylic copolymer (weight average molecular weight: approximately 460,000) obtained by random copolymerization of 64 parts of 2-ethylhexyl acrylate, 19 parts of methyl acrylate, and 17 parts of hydroxyethyl acrylate.

[0224] [Ultraviolet absorbers (B)] Ultraviolet absorber (B-1): 2,4-bis[4-(2-ethylhexyloxy)-2-hydroxyphenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (maximum absorption wavelength: 346 nm, "Tinosorb S" manufactured by BASF Japan Ltd.) Ultraviolet absorber (B-2): 2((2-(dibutylamino)-4-epoxy-6-methyl-5-pyrimidinyl)methylene)propanedinitrile (maximum absorption wavelength: 402 nm, half width: 43 nm, "FDB-009" manufactured by Yamada Chemical Co., Ltd.)

[0225] [Crosslinking agent (C)] Crosslinking agent (C-1): urethane acrylate composed of 2-hydroxyethyl acrylate, isophorone diisocyanate, and propylene glycol ("KRM9465" manufactured by Daicel Allnex Corporation, glass transition temperature (Tg): -45°C, number of ethylenically unsaturated groups: 2, weight average molecular weight: 10,000) Crosslinking agent (C-2): pentaerythritol tri(tetra)acrylate ("NK Ester ATMM3L" manufactured by Shin-Nakamura Chemical Co., Ltd., number of ethylenically unsaturated groups: 3 to 4, weight average molecular weight: 298 to 352) [Photoinitiator (D)] Photoinitiator (D-1): ethyl (2,4,6-trimethylbenzoyl)-phenylphosphinate (molar absorption coefficient at a wavelength of 405 nm: 81 L / mol cm, "Omnirad TPO-L" manufactured by IGM) Photoinitiator (D-2): dimethyl 2,2'-(thiobis(4,1-phenylene))bis(2-octoacetate) (molar absorption coefficient at a wavelength of 405 nm: 329 L / mol cm)

[0226] Example 1 A pressure-sensitive adhesive composition was prepared by uniformly mixing 100 parts of a (meth)acrylic polymer (P1), 0.4 parts of an ultraviolet absorber (B-1), 0.4 parts of an ultraviolet absorber (B-2), 20 parts of a crosslinking agent (C-1), and 2 parts of a photoinitiator (D-1). The pressure-sensitive adhesive composition was then molded into a sheet having a thickness of 100 μm onto a silicone release-treated release film having a thickness of 100 μm (a polyethylene terephthalate (PET) film manufactured by Mitsubishi Chemical Corporation).

[0227] Thereafter, a 75 μm-thick release film (a PET film manufactured by Mitsubishi Chemical Corporation) that had been subjected to a silicone release treatment was laminated on the sheet-like pressure-sensitive adhesive composition to form a laminate, thereby obtaining a pressure-sensitive adhesive composition sheet with a release film consisting of a release film / pressure-sensitive adhesive composition layer / release film. Next, a high-pressure mercury lamp was used to irradiate the pressure-sensitive adhesive composition from the surface of the release film-attached pressure-sensitive adhesive composition sheet through the release film, with an integrated light intensity of about 1500 mJ / cm at a wavelength of 365 nm. 2 (The measured value at 405 nm was 1.1 J / cm 2 ) and a pressure-sensitive adhesive sheet with release films laminated on both the front and back surfaces was obtained.

[0228] Examples 2 and 3, Comparative Examples 1 to 3 PSA sheets with release films of Examples 2 and 3 and Comparative Examples 1 to 3 were prepared in the same manner as in Example 1, except that the formulations were changed as shown in Table 1 below.

[0229] The resulting pressure-sensitive adhesive sheets with release films of the Examples and Comparative Examples were measured and evaluated as follows, and the results are shown in Table 1 below.

[0230] <Light Transmittance> One release film was peeled off from the pressure-sensitive adhesive sheets with release films prepared in the Examples and Comparative Examples, and the exposed adhesive surface was roll-pressed onto a soda-lime glass (82 mm x 53 mm x 0.5 mm thick). Next, the remaining release film was peeled off, and the sheet was roll-pressed onto a soda-lime glass (82 mm x 53 mm x 0.5 mm thick). The sheet was then autoclaved (60°C, 0.2 MPa gauge pressure, 20 minutes) for finish bonding to prepare a laminate for evaluation. The light transmittance (%) of the evaluation laminate at wavelengths of 250 to 800 nm was measured using a spectrophotometer (Hitachi High-Technologies Corporation, "U-4100") . Light transmittances at 380 nm, 405 nm, and 430 nm were read from the resulting spectrum.

[0231] <Storage Shear Modulus (G'), Loss Tangent (Tan δ), Glass Transition Temperature (Tg)> The release films were removed from each of the release film-attached pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples, and multiple layers of pressure-sensitive adhesive sheets were laminated to form a laminate with a thickness of approximately 0.8 mm. A cylindrical object with a diameter of 8 mm was punched out from the resulting pressure-sensitive adhesive sheet laminate, and this was used as a sample. The temperature dispersion of dynamic viscoelasticity of this sample was measured under the following measurement conditions using a viscoelasticity measuring device (DHR20, manufactured by T.A. Instruments). From the obtained temperature dispersion data of dynamic viscoelasticity, the maximum values ​​of the storage shear modulus (G') and loss tangent (Tan δ) at -20°C and 23°C, as well as the peak temperature of the loss tangent (tan δ) as the glass transition temperature (Tg), were read. (Measurement conditions) Measurement jig: Φ8 mm parallel plate Distortion: 0.1% Frequency: 1 Hz Measurement temperature: -50 to 100°C Heating rate: 5°C / min

[0232] <Gel Fraction> The release film was peeled off from each of the pressure-sensitive adhesive sheets with release film prepared in the Examples and Comparative Examples, and a pressure-sensitive adhesive sheet piece weighing approximately 0.1 g was collected from the pressure-sensitive adhesive sheet. The collected pressure-sensitive adhesive sheet piece was wrapped in a bag-shaped SUS mesh (#150) with a mass (X), and the bag was closed to prepare a sample, and the mass (Y) of the sample was measured. The sample was immersed in ethyl acetate and stored in a dark place at 23°C for 24 hours, and then the sample was removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate, and the mass (Z) of the dried sample was measured. The gel fraction (X0) before light irradiation was calculated from each measured mass using the following formula: Gel fraction (%) = [(Z-X) / (Y-X)] x 100

[0233] <Adhesive Strength> One release film was removed from each of the release film-attached pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples, and a polyethylene terephthalate film (Cosmoshine A4300 manufactured by Toyobo Co., Ltd.) was roll-laminated as a backing film to the adhesive surface of the resulting pressure-sensitive adhesive sheet using a hand roller. This was cut into 10 mm wide strips, and the remaining release film was peeled off, and the exposed adhesive surface was roll-laminated to a soda-lime glass plate using a hand roller to produce a laminate consisting of glass / pressure-sensitive adhesive sheet / backing film.

[0234] The laminate was subjected to autoclave treatment (60°C, gauge pressure 0.2 MPa, 20 minutes) for finish adhesion to prepare a sample for evaluating glass adhesion. The backing film was peeled off at an angle of 180° to the glass plate at a peeling rate of 300 mm / min, and the tensile strength was measured with a load cell to determine the 180° peel strength (N / cm) of the PSA sheet to the glass surface.

[0235]

[0236] The results in Table 1 show that the pressure-sensitive adhesive sheets of the Examples were excellent in transparency and UV absorption properties. Furthermore, because they also had excellent viscoelastic properties, image display devices equipped with these pressure-sensitive adhesive sheets could be made to have excellent impact resistance. On the other hand, the pressure-sensitive adhesive sheet of Comparative Example 1 did not contain UV absorber (B), and thus was unable to achieve the desired UV absorption properties. Furthermore, the pressure-sensitive adhesive sheet of Comparative Example 2 had a high light transmittance at a wavelength of 405 nm and low UV absorption properties because the content ratio of UV absorbers (B-1) and (B-2) was outside the desired range. Furthermore, the pressure-sensitive adhesive sheet of Comparative Example 3 contained only UV absorber (B-1), and therefore had high light transmittance at wavelengths of 380 nm and 405 nm, and low UV absorption properties.

[0237] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0238] This pressure-sensitive adhesive sheet has sufficient impact resistance and transparency, and also has excellent ultraviolet absorption properties up to the near visible light region, making it useful as a pressure-sensitive adhesive sheet for attaching optical components, particularly as a pressure-sensitive adhesive sheet for organic light-emitting diode (OLED) display devices.

Claims

1. An adhesive sheet comprising a resin component (A) having a structural unit derived from a (meth)acrylate monomer and an ultraviolet absorber (B), and satisfying the following requirements [I] and [II]. [I] The ultraviolet absorber (B) includes an ultraviolet absorber (B-1) having an absorption maximum at a wavelength of 300 to 360 nm and an ultraviolet absorber (B-2) other than the above (B-1) having an absorption maximum at a wavelength of 350 to 420 nm. [II] The content ratio of the ultraviolet absorber (B-1) to the ultraviolet absorber (B-2) contained in the adhesive sheet is 30:70 to 70:30 by mass ratio.

2. The adhesive sheet according to claim 1, further satisfying the following requirement [III]. [III] In the adhesive sheet, the storage shear modulus at -20°C obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is 2.0 MPa or less, and the glass transition temperature determined at the peak of the loss tangent (tan δ) is -20°C or less.

3. The adhesive sheet according to claim 1, wherein the ultraviolet absorber (B-2) has a pyrimidine structure.

4. The adhesive sheet according to claim 1, wherein the content of the ultraviolet absorber (B) is 0.1 to 20% by mass based on the adhesive sheet.

5. The adhesive sheet according to claim 1, wherein the resin component (A) has a structural unit derived from a crosslinking agent (C).

6. The adhesive sheet according to claim 5, wherein the crosslinking agent (C) includes an acrylic crosslinking agent having a glass transition temperature (Tg) of -20°C or less determined from the Fox equation.

7. The adhesive sheet according to claim 5, wherein the crosslinking agent (C) includes an acrylic crosslinking agent having 1 to 3 ethylenically unsaturated groups in the molecule.

8. The adhesive sheet according to claim 5, wherein the crosslinking agent (C) includes an acrylic crosslinking agent having an oxyalkylene structure.

9. The adhesive sheet according to claim 5, wherein the crosslinking agent (C) includes a polyfunctional (meth)acrylate oligomer having a weight average molecular weight of 1000 or more.

10. The adhesive sheet according to claim 5, wherein the crosslinking agent (C) includes urethane (meth)acrylate.

11. The adhesive sheet according to claim 1, wherein the adhesive sheet includes a photoinitiator (D).

12. The adhesive sheet according to claim 11, wherein the photoinitiator (D) is a hydrogen abstraction type photoinitiator.

13. The adhesive sheet according to claim 1, wherein the gel fraction is 5 to 80%.

14. A pressure-sensitive adhesive sheet with a release film, comprising a structure in which the pressure-sensitive adhesive sheet according to any one of claims 1 to 13 and a release film are laminated.

15. A laminate for an image display device, comprising a configuration in which two optical members are laminated via the pressure-sensitive adhesive sheet according to any one of claims 1 to 13.

16. An image display device comprising the laminate for an image display device according to claim 15.

17. A pressure-sensitive adhesive sheet for an organic light-emitting diode display device, comprising the pressure-sensitive adhesive sheet according to any one of claims 1 to 13.

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