Pressure-sensitive adhesive sheet, optical film with pressure-sensitive adhesive layer, and optical laminate

Abstract

To provide an adhesive sheet which has ultraviolet absorbability and has excellent durability even when an adhesive layer is formed into a thin film, and to provide an optical film with an adhesive layer and an optical laminate.SOLUTION: There is provided an adhesive sheet 1 having at least an adhesive layer 11 which is used for optical applications, wherein the light transmittance (%) at a wavelength of 350 nm of the adhesive layer 11 is 20% or less and when the light transmittance (%) at a wavelength of 400 nm of the adhesive layer 11 is defined as X and the light transmittance (%) at a wavelength of 430 nm of the adhesive layer 11 is defined as Y, the following expressions (I) and (II) are satisfied and the storage elastic modulus at 23°C of the adhesive layer 11 is 0.15 MPa or more and 2 MPa or less. Y-X≥60 (I) Y / X≥4 (II)SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a method for producing the same, an optical film with a pressure-sensitive adhesive layer, and an optical laminate, and in particular to a pressure-sensitive adhesive sheet that has ultraviolet absorption properties and is suitable for laminating a polarizing plate, a retardation film, etc., and a method for producing the same, an optical film with a pressure-sensitive adhesive layer, and an optical laminate. [Background technology]

[0002] BACKGROUND ART In recent years, image display devices such as liquid crystal displays have been widely used as displays for various electronic devices, but recently, organic electroluminescence (organic EL) displays have also been increasingly used.

[0003] The above-mentioned displays are manufactured by laminating various optical members, such as polarizing plates and retardation films, which are adhered and laminated using pressure-sensitive adhesives.

[0004] The pressure-sensitive adhesive may be used in the form of a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet. An example of a pressure-sensitive adhesive sheet used for laminating optical components is disclosed in Patent Document 1. The pressure-sensitive adhesive layer of this pressure-sensitive adhesive sheet is made of an ultraviolet-curable pressure-sensitive adhesive. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-002119 Summary of the Invention [Problem to be solved by the invention]

[0006] Recently, various optical components of displays are required to be protected from ultraviolet light. In particular, protection from ultraviolet light is considered important because the light-emitting elements (OLEDs) of organic electroluminescent displays are susceptible to degradation by ultraviolet light. One possible solution to this problem is to incorporate an ultraviolet absorber into the adhesive layer. However, if an ultraviolet absorber is incorporated into an ultraviolet-curable adhesive such as that disclosed in Patent Document 1, the ultraviolet-curable adhesive will not cure sufficiently, resulting in reduced durability. Furthermore, with the recent trend toward thinner mobile electronic devices, thinner adhesive layers are sometimes required. In this case, adhesive strength is likely to decrease, further posing a problem with the durability described above.

[0007] The present invention has been made in consideration of the above-described circumstances, and aims to provide an adhesive sheet that has ultraviolet absorption properties and excellent durability even when the adhesive layer is thinned, a method for manufacturing the same, an optical film with an adhesive layer, and an optical laminate. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, first, the present invention provides a pressure-sensitive adhesive sheet for optical applications, which has at least a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a light transmittance (%) of 20% or less at a wavelength of 350 nm, and the pressure-sensitive adhesive layer has a light transmittance (%) of 400 nm wavelength (X) and a light transmittance (%) of 430 nm wavelength (Y), satisfying the following formulas (I) and (II), and the pressure-sensitive adhesive layer has a storage modulus at 23°C of 0.15 MPa or more and 2 MPa or less (Invention 1). YX≧60 (I) Y / X≧4 (II)

[0009] The pressure-sensitive adhesive layer in the above invention (Invention 1) has a light transmittance (%) of 20% or less at 350 nm, thereby providing excellent UV absorption and preventing deterioration of a member to which the pressure-sensitive adhesive layer is attached due to UV rays passing through the pressure-sensitive adhesive layer. Furthermore, when the pressure-sensitive adhesive layer's light transmittance (%) at 400 nm is defined as X and its light transmittance (%) at 430 nm is defined as Y, satisfying the above formulas (I) and (II) provides excellent UV absorption and visible light transmittance, resulting in a display with excellent image visibility. In particular, the pressure-sensitive adhesive layer can exhibit excellent UV absorption for UV rays in the long wavelength region (near 400 nm) close to visible light. Furthermore, the pressure-sensitive adhesive layer's storage modulus at 23°C of 0.15 MPa or more provides excellent durability, even when used as a thin film or when used as an adherend to a polarizing plate, a retardation film, or the like.

[0010] In the above invention (Invention 1), the thickness of the pressure-sensitive adhesive layer is preferably 0.1 μm or more and 10 μm or less (Invention 2).

[0011] In the above inventions (Inventions 1 and 2), the adhesive strength to alkali-free glass is preferably 0.5 N / 25 mm or more (Invention 3).

[0012] In the above inventions (Inventions 1 to 3), the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably 40% or more and 100% or less (Invention 4).

[0013] In the above inventions (Inventions 1 to 4), the pressure-sensitive adhesive layer preferably has a light transmittance (%) of 20% or less at a wavelength of 400 nm (Invention 5).

[0014] In the above inventions (Inventions 1 to 5), the pressure-sensitive adhesive layer preferably has a light transmittance (%) of 80% or more at a wavelength of 430 nm (Invention 6).

[0015] In the above inventions (Inventions 1 to 6), the pressure-sensitive adhesive layer preferably comprises a pressure-sensitive adhesive containing at least a cured product of an active energy ray-curable component and an ultraviolet absorber (Invention 7).

[0016] In the above invention (Invention 7), the pressure-sensitive adhesive preferably contains a crosslinked product obtained by crosslinking a (meth)acrylic acid ester polymer (Invention 8).

[0017] In the above inventions (Inventions 7 and 8), it is preferable that the pressure-sensitive adhesive is obtained from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), and an ultraviolet absorber (E) (Invention 9).

[0018] In the above invention (Invention 9), it is preferable that the maximum absorption wavelength of the photopolymerization initiator (D) and the maximum absorption wavelength of the ultraviolet absorber (E) are different (Invention 10).

[0019] In the above inventions (Inventions 9 and 10), the pressure-sensitive adhesive composition preferably contains, as the ultraviolet absorber (E), two types of ultraviolet absorbers having different maximum absorption wavelengths (Invention 11).

[0020] In the above inventions (Inventions 9 to 11), it is preferable that the photopolymerization initiator (D) has a light absorption wavelength peak region of 400 nm or more (Invention 12).

[0021] In the above inventions (Inventions 1 to 12), it is preferable that two release sheets are provided, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to contact the release surfaces of the two release sheets (Invention 13).

[0022] Secondly, the present invention provides a method for producing the pressure-sensitive adhesive sheet (Invention 10), characterized in that the pressure-sensitive adhesive layer is formed by thermally crosslinking and active energy ray-curing an adhesive composition containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), and an ultraviolet absorber (E) (Invention 14).

[0023] Thirdly, the present invention provides an optical film with a pressure-sensitive adhesive layer (Invention 15), characterized by comprising an optical film and a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Inventions 1 to 13) laminated on at least one side of the optical film.

[0024] In the above invention (Invention 15), the optical film is preferably a polarizing plate or a retardation film (Invention 16).

[0025] Fourth, the present invention provides an optical laminate comprising a first optical film, a second optical film, and a pressure-sensitive adhesive layer that bonds the first optical film and the second optical film to each other, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Inventions 1 to 13) (Invention 17).

[0026] In the above invention (Invention 17), it is preferable that the first optical film is a polarizing plate or a retardation film, and the second optical film is a retardation film (Invention 18). [Effects of the Invention]

[0027] The pressure-sensitive adhesive sheet, pressure-sensitive adhesive layer-attached optical film, and optical laminate according to the present invention have ultraviolet absorption properties and are excellent in durability even when the pressure-sensitive adhesive layer is made thin. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2]1 is a cross-sectional view of a pressure-sensitive adhesive layer-attached optical film according to one embodiment of the present invention. [Figure 3] 1 is a cross-sectional view of an optical laminate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, an embodiment of the present invention will be described. [Adhesive sheet] A pressure-sensitive adhesive sheet according to one embodiment of the present invention has at least a pressure-sensitive adhesive layer and is used for optical applications. The pressure-sensitive adhesive layer preferably has a light transmittance (%) of 20% or less at a wavelength of 350 nm, and satisfies the following formulas (I) and (II) where X is the light transmittance (%) at a wavelength of 400 nm and Y is the light transmittance (%) at a wavelength of 430 nm. The pressure-sensitive adhesive layer preferably has a storage modulus at 23°C of 0.15 MPa or more and 2 MPa or less. The method for measuring light transmittance in this specification is as shown in the test examples described below. The storage modulus in this specification is a value measured by a torsional shear method at a measurement frequency of 1 Hz in accordance with JIS K7244-6. Specifically, the method is as shown in the test examples described below. YX≧60 (I) Y / X≧4 (II)

[0030] The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of this embodiment has a light transmittance (%) of 20% or less at a wavelength of 350 nm, thereby providing excellent UV absorption and preventing deterioration of a member to which the pressure-sensitive adhesive layer is attached due to UV rays passing through the pressure-sensitive adhesive layer. Furthermore, when the pressure-sensitive adhesive layer's light transmittance (%) at a wavelength of 400 nm is defined as X and the pressure-sensitive adhesive layer's light transmittance (%) at a wavelength of 430 nm is defined as Y, satisfying the above formulas (I) and (II) provides excellent UV absorption and visible light transmittance, resulting in a display with excellent image visibility. In particular, the pressure-sensitive adhesive layer can exhibit excellent UV absorption for UV rays in the long wavelength region (near 400 nm) close to visible light. Furthermore, the pressure-sensitive adhesive layer's storage modulus at 23°C of 0.15 MPa or more provides excellent durability, even when used as a thin film or when used as an adherend to a polarizing plate, a retardation film, or the like. Specifically, when a laminate obtained by laminating a polarizing plate having a saponified triacetyl cellulose protective film and an alkali-free glass plate via the thin adhesive layer of the adhesive sheet is subjected to durability conditions of 85°C, 85% RH, and 500 hours, the occurrence of lifting, peeling, bubbling, streaks, etc. is suppressed. Note that polarizing plates, retardation films, etc. are prone to shrinkage when subjected to the durability conditions described above, and the shrinkage stress generated at that time makes them prone to warping. It is presumed that this makes the laminate prone to lifting, peeling, bubbling, streaks, etc.; however, since the adhesive layer has the above-described storage modulus, it is easy to suppress the above-described warping even in a thin film, and as a result, it is thought that the occurrence of lifting, peeling, bubbling, streaks, etc. is suppressed.

[0031] From the viewpoint of improving ultraviolet absorption, the light transmittance (%) at a wavelength of 350 nm is preferably 20% or less, more preferably 10% or less, particularly preferably 5% or less, and even more preferably 3% or less. The lower limit of the light transmittance is usually 0% or more, preferably 0.1% or more, particularly preferably 0.5% or more, and even more preferably 0.8% or more.

[0032] From the viewpoint of improving ultraviolet absorption and visible light transmittance, the light transmittance difference YX (hereinafter sometimes simply referred to as "light transmittance difference") represented by the above formula (I) is preferably 60 points or more, more preferably 64 points or more, particularly preferably 68 points or more, and even more preferably 70 points or more. The upper limit of the light transmittance difference is not particularly limited, but is usually 100 points or less, and from the viewpoint of making it easier for the light transmittance at a wavelength of 400 nm and the light transmittance at a wavelength of 430 nm to reach the desired values, it is preferably 95 points or less, more preferably 90 points or less, particularly preferably 85 points or less, and even more preferably 80 points or less.

[0033] From the viewpoint of improving ultraviolet absorption and visible light transmittance, the light transmittance ratio Y / X (hereinafter sometimes simply referred to as "light transmittance ratio") represented by the above formula (II) is preferably 4 or more, more preferably 4.5 or more, particularly preferably 5 or more, and even more preferably 5.5 or more. The upper limit of the light transmittance ratio is not particularly limited, but is usually 50 or less, and from the viewpoint of making it easier for the light transmittance at a wavelength of 400 nm and the light transmittance at a wavelength of 430 nm to reach the desired values, it is preferably 40 or less, more preferably 20 or less, particularly preferably 10 or less, and even more preferably 7 or less.

[0034] From the viewpoint of improving durability, the storage modulus of the pressure-sensitive adhesive layer at 23°C is preferably 0.15 MPa or more, more preferably 0.18 MPa or more, particularly preferably 0.22 MPa or more, and even more preferably 0.25 MPa or more. The upper limit of the storage modulus is preferably 2 MPa or less, more preferably 1.2 MPa or less, particularly preferably 0.7 MPa or less, even more preferably 0.45 MPa or less, and most preferably 0.4 MPa or less. When the upper limit of the storage modulus is as described above, the pressure-sensitive adhesive is more likely to exhibit appropriate flexibility and has better conformability to adherends such as polarizing plates and retardation films. This makes it easier for the pressure-sensitive adhesive layer to exhibit excellent adhesive strength and adhesion, particularly when the pressure-sensitive adhesive layer is thin, and ultimately leads to better durability.

[0035] From the viewpoint of improving ultraviolet absorption, the light transmittance (%) at a wavelength of 380 nm is preferably 20% or less, more preferably 15% or less, particularly preferably 10% or less, and even more preferably 5% or less. The lower limit of the light transmittance is usually 0% or more, and from the viewpoint of the reactivity of the active energy ray-curable component (C) with the photopolymerization initiator (D), it is preferably 0.1% or more, particularly preferably 1% or more, and even more preferably 3% or more.

[0036] From the viewpoint of improving ultraviolet absorption, the light transmittance of the pressure-sensitive adhesive layer at a wavelength of 400 nm is preferably 20% or less, more preferably 18% or less, particularly preferably 17% or less, and even more preferably 16% or less. The lower limit of the light transmittance is not particularly limited, but is usually 0% or more. From the viewpoint of making it easier for the light transmittance difference and light transmittance ratio to fall within the above ranges, it is preferably 5% or more. From the viewpoint of improving the curability of the active energy ray-curable component (C) by the photopolymerization initiator (D), it is more preferably 10% or more, particularly preferably 12% or more, and even more preferably 12.5% ​​or more.

[0037] From the viewpoint of improving visible light transmittance, the light transmittance of the pressure-sensitive adhesive layer at a wavelength of 430 nm is preferably 80% or more, more preferably 81% or more, particularly preferably 82% or more, and even more preferably 83% or more. The lower limit of the light transmittance is not particularly limited and may be 100%, but from the viewpoint of making it easier for the light transmittance difference and light transmittance ratio to fall within the above ranges, it is preferably 95% or less, more preferably 90% or less, particularly preferably 88% or less, and even more preferably 86% or less.

[0038] From the viewpoint of improving visible light transmittance, the light transmittance (%) at a wavelength of 500 nm is preferably 80% or more, more preferably 84% or more, particularly preferably 88% or more, and even more preferably 90% or more. The lower limit of the light transmittance is not particularly limited, but is usually 100% or less, preferably 99% or less, particularly preferably 96% or less, and even more preferably 92% or less.

[0039] The gel fraction of the adhesive constituting the adhesive layer in the adhesive sheet of this embodiment is preferably 40% or more, more preferably 60% or more, particularly preferably 70% or more, and even more preferably 80% or more. Furthermore, the gel fraction is preferably 100% or less, more preferably 96% or less, particularly preferably 92% or less. From the viewpoint of improving the optical properties and adhesive strength described above, it is even more preferably 90% or less, and most preferably 88% or less. When the gel fraction of the adhesive is within the above range, the adhesive has a predetermined cohesive strength and is more likely to satisfy the storage modulus described above. The method for measuring the gel fraction in this specification is as shown in the test examples described below.

[0040] The thickness of the adhesive layer in the adhesive sheet of this embodiment is preferably 10 μm or less, more preferably 8 μm or less, particularly preferably 7 μm or less, even more preferably 6 μm or less, and most preferably 5 μm or less. This allows the adhesive layer to be made thinner, thereby making the resulting display thinner. Furthermore, in this embodiment, even if the adhesive layer is as thin as described above, the storage modulus is within the above range, resulting in excellent durability. Furthermore, the adhesive layer is more likely to achieve the desired light transmittance at a wavelength of 430 nm, thereby exhibiting excellent visible light transmittance, and the resulting display has excellent image visibility.

[0041] On the other hand, from the viewpoint of improving durability and adhesive strength, the thickness of the pressure-sensitive adhesive layer is preferably 0.1 μm or more, more preferably 1 μm or more, particularly preferably 2 μm or more, further preferably 3 μm or more, and most preferably 4 μm or more, which makes it easier for the pressure-sensitive adhesive layer to achieve a desired light transmittance at a wavelength of 400 nm, thereby exhibiting excellent ultraviolet absorption properties.

[0042] The adhesive strength of the pressure-sensitive adhesive sheet of this embodiment to alkali-free glass is preferably 0.5 N / 25 mm or more, more preferably 1 N / 25 mm or more, particularly preferably 1.1 N / 25 mm or more, and even more preferably 1.2 N / 25 mm or more, which makes it easier to exhibit higher durability when used as an adherend to a polarizing plate, a retardation film, or the like.

[0043] On the other hand, the upper limit of the adhesive strength is not particularly limited, but taking reworkability into consideration, it is preferably 20 N / 25 mm or less, more preferably 12 N / 25 mm or less, particularly preferably 8 N / 25 mm or less, even more preferably 4 N / 25 mm or less, and most preferably 3 N / 25 mm or less.

[0044] Here, the adhesive strength in this specification basically refers to the adhesive strength measured by the 180-degree peel method in accordance with JIS Z0237:2009, and the measurement sample is 25 mm wide and 100 mm long, and the measurement sample is attached to the adherend and pressurized at 0.5 MPa and 50°C for 20 minutes, and then left to stand for 24 hours under conditions of normal pressure, 23°C, and 50% RH, and then measured at a peel speed of 300 mm / min.

[0045] FIG. 1 shows a specific configuration of an example of the pressure-sensitive adhesive sheet according to this embodiment. 1, the adhesive sheet 1 is composed of two release sheets 12a and 12b and an adhesive layer 11 sandwiched between the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. In this specification, the release surface of a release sheet refers to the surface of the release sheet that has releasability, and includes both a surface that has been subjected to a release treatment and a surface that exhibits releasability even without being subjected to a release treatment.

[0046] 1. Each component 1-1. Adhesive layer The type of adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to this embodiment is not particularly limited, and may be, for example, an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, or the like. The adhesive may be an emulsion type, a solvent type, or a solventless type, and may be a crosslinked type or a non-crosslinked type. Among these, an acrylic adhesive is preferred because of its excellent adhesive properties, optical properties, and the like.

[0047] The adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to this embodiment preferably contains at least a cured product of an active energy ray-curable component and an ultraviolet absorber, and preferably further contains a crosslinked product obtained by crosslinking a (meth)acrylic acid ester polymer. Such an adhesive is likely to satisfy the above-mentioned physical properties and can obtain particularly high durability.

[0048] A pressure-sensitive adhesive containing a crosslinked product obtained by crosslinking a (meth)acrylic acid ester polymer, a cured product of an active energy ray-curable component, and an ultraviolet absorber can be obtained by thermally crosslinking and active energy ray-curing an adhesive composition containing a (meth)acrylic acid ester polymer, a crosslinking agent (thermal crosslinking agent), an active energy ray-curable component, a photopolymerization initiator, and an ultraviolet absorber, or by active energy ray-curing a composition containing constituent monomers of the (meth)acrylic acid ester polymer, the crosslinking agent, the active energy ray-curable component, the photopolymerization initiator, and an ultraviolet absorber.

[0049] The adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to this embodiment is preferably a pressure-sensitive adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), and an ultraviolet absorber (E) that is thermally crosslinked and active energy ray-cured. The (meth)acrylic acid ester polymer (A) is preferably non-active energy ray-curable, and the crosslinking agent (B) is preferably a thermal crosslinking agent. Furthermore, the adhesive composition P preferably contains two types of ultraviolet absorbers (E) that have different maximum absorption wavelengths. In this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" also includes the concept of "copolymer."

[0050] (1) Components of the adhesive composition (1-1) (Meth)acrylic acid ester polymer (A) The (meth)acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer constituting the polymer. By containing this reactive functional group-containing monomer, the reactive functional group derived from the reactive functional group-containing monomer reacts with the crosslinking agent (B) described below, thereby forming a crosslinked structure (three-dimensional network structure), and a pressure-sensitive adhesive having a predetermined cohesive strength is obtained.

[0051] Preferred examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and a monomer having an amino group in the molecule (amino group-containing monomer). These reactive functional group-containing monomers may be used alone or in combination of two or more. Among the reactive functional group-containing monomers, preferred are hydroxyl group-containing monomers or carboxyl group-containing monomers, which have excellent reactivity with the crosslinking agent (B).

[0052] Examples of hydroxyl group-containing monomers include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these, from the viewpoints of the reactivity of the hydroxyl groups in the resulting (meth)acrylic acid ester polymer (A) with the crosslinking agent (B) and copolymerizability with other monomers, preferred are (meth)acrylic acid hydroxyalkyl esters having a hydroxyalkyl group having 1 to 4 carbon atoms. Specific examples include 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, with 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate being particularly preferred. These may be used alone or in combination of two or more.

[0053] Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferred from the viewpoint of adhesive strength and reactivity with the crosslinking agent (B). These may be used alone or in combination of two or more.

[0054] The (meth)acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a monomer unit constituting the polymer in an amount of at least 1% by mass, more preferably at least 2% by mass. When the reactive group-containing monomer is a carboxyl group-containing monomer, the amount is preferably at least 3% by mass, and more preferably at least 4% by mass. Furthermore, the (meth)acrylic acid ester polymer (A) preferably contains a reactive group-containing monomer as a monomer unit constituting the polymer in an amount of at most 10% by mass, more preferably at most 8% by mass, and more preferably at most 6% by mass. When the reactive group-containing monomer is a hydroxyl group-containing monomer, the amount is preferably at most 4% by mass, and more preferably at most 3% by mass. When the (meth)acrylic acid ester polymer (A) contains the reactive group-containing monomer as a monomer unit in the above amount, a good crosslinked structure is formed in the resulting pressure-sensitive adhesive, making it easier to achieve the aforementioned gel fraction and storage modulus. Furthermore, compatibility with components such as the active energy ray-curable component (C) and the ultraviolet absorber (E) is likely to be good, and the resulting pressure-sensitive adhesive is likely to exhibit the optical properties described above.

[0055] The (meth)acrylic acid ester polymer (A) preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. This allows the polymer to exhibit good adhesiveness. The alkyl group may be linear or branched.

[0056] From the viewpoint of adhesiveness, the (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 20 carbon atoms. Examples of the (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0057] Among the above, from the viewpoint of efficiently imparting adhesive strength, (meth)acrylic acid alkyl esters having an alkyl group with 2 to 12 carbon atoms are more preferred, and acrylic acid alkyl esters having an alkyl group with 4 to 10 carbon atoms are particularly preferred. Specifically, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate are preferred, n-butyl (meth)acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate are more preferred, and of these, n-butyl acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0058] From the viewpoint of imparting adhesiveness, the (meth)acrylic acid ester polymer (A) preferably contains, as monomer units constituting the polymer, 70% by mass or more, particularly preferably 80% by mass or more, and even more preferably 85% by mass or more of (meth)acrylic acid alkyl esters having an alkyl group with a carbon number of 1 to 20. Furthermore, from the viewpoint of ensuring the content of other monomers, the (meth)acrylic acid alkyl esters having an alkyl group with a carbon number of 1 to 20 are preferably contained in 99% by mass or less, particularly preferably 98% by mass or less, and even more preferably 96% by mass or less.

[0059] Furthermore, the (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer). When the alicyclic structure-containing monomer is contained, the bulky functional group thereof increases the distance between the (meth)acrylic acid ester polymers (A), thereby increasing the flexibility of the resulting pressure-sensitive adhesive and further improving the adhesive strength to adherends such as polarizing plates and retardation films.

[0060] The carbon ring of the alicyclic structure may be a saturated structure or may have an unsaturated bond. The alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic or tricyclic structure. The number of carbon atoms in the alicyclic structure is preferably 5 to 20, more preferably 6 to 15, and even more preferably 7 to 12.

[0061] Preferred examples of the alicyclic structure include those containing a cyclohexyl skeleton, a dicyclopentadiene skeleton, an adamantane skeleton, an isobornyl skeleton, a cycloalkane skeleton (a cycloheptane skeleton, a cyclooctane skeleton, a cyclononane skeleton, a cyclodecane skeleton, a cycloundecane skeleton, a cyclododecane skeleton, etc.), a cycloalkene skeleton (a cycloheptene skeleton, a cyclooctene skeleton, etc.), a norbornene skeleton, a norbornadiene skeleton, a polycyclic skeleton (a cubane skeleton, a basketane skeleton, a hasan skeleton, etc.), a spiro skeleton, etc. Among these, those containing an adamantane skeleton or an isobornyl skeleton are preferred from the viewpoint of further improving adhesive strength to various adherends.

[0062] The alicyclic structure-containing monomer is preferably a (meth)acrylic acid ester monomer having the above skeleton, specifically, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc., among which adamantyl (meth)acrylate and isobornyl (meth)acrylate are preferred, and isobornyl acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0063] From the viewpoint of increasing the adhesive strength of the resulting pressure-sensitive adhesive to adherends such as polarizing plates and retardation films, the (meth)acrylic acid ester polymer (A) preferably contains 1% by mass or more, particularly preferably 4% by mass or more, and even more preferably 8% by mass or more, of an alicyclic structure-containing monomer as a monomer unit constituting the polymer. Furthermore, from the viewpoint of ensuring the content of other monomers, the content of the alicyclic structure-containing monomer is preferably 20% by mass or less, particularly preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0064] The (meth)acrylic acid ester polymer (A) may be a solution polymer obtained by solution polymerization or a solventless polymer obtained by irradiation with active energy rays, but is preferably a solution polymer, which makes it easier to form a thin pressure-sensitive adhesive layer.

[0065] The (meth)acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired. The other monomers are preferably monomers that do not contain reactive functional groups, so as not to inhibit the aforementioned action of the reactive functional group-containing monomer. Examples of such monomers include non-reactive nitrogen atom-containing monomers such as N-acryloylmorpholine and N-vinyl-2-pyrrolidone, (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

[0066] The polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

[0067] The weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 1,000,000 or more, more preferably 1,400,000 or more, and particularly preferably 1,700,000 or more, from the viewpoint of easily satisfying the storage modulus requirement described above. Furthermore, from the viewpoint of easily achieving good compatibility with components such as the active energy ray-curable component (C) and the ultraviolet absorber (E), and easily enabling the resulting pressure-sensitive adhesive to exhibit the optical properties described above, it is preferably 1,800,000 or more, and particularly preferably 1,900,000 or more. Furthermore, the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 3,000,000 or less, more preferably 2,600,000 or less, particularly preferably 2,400,000 or less, and even more preferably 2,200,000 or less. When the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is within the above range, the optical properties, storage modulus, and adhesive strength described above are easily satisfied. In particular, even when the pressure-sensitive adhesive layer is thin, it is likely to exhibit excellent adhesive strength and adhesion, and excellent conformability to adherends such as polarizing plates and retardation films. The weight average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) and converted into standard polystyrene.

[0068] The acid value of the (meth)acrylic acid ester polymer (A) is preferably 0.5 mgKOH / g or more, more preferably 5 mgKOH / g or more, particularly preferably 15 mgKOH / g or more, and even more preferably 30 mgKOH / g or more. The acid value of the (meth)acrylic acid ester polymer (A) is preferably 120 mgKOH / g or less, more preferably 80 mgKOH / g or less, particularly preferably 60 mgKOH / g or less, and even more preferably 40 mgKOH / g or less. When the acid value is within the above range, the resulting pressure-sensitive adhesive is likely to satisfy the storage modulus and gel fraction requirements described above. In particular, the resulting pressure-sensitive adhesive has an appropriate number of crosslinking points, which makes it easy to form a crosslinked structure that exhibits flexibility. Therefore, even when the pressure-sensitive adhesive layer is thin, it is likely to exhibit suitable adhesive strength and adhesion, and it exhibits excellent conformability to adherends such as polarizing plates and retardation films, thereby exhibiting excellent durability.

[0069] The hydroxyl value of the (meth)acrylic acid ester polymer (A) is preferably 5 mgKOH / g or more, particularly preferably 8 mgKOH / g or more, and even more preferably 9 mgKOH / g or more. The hydroxyl value of the (meth)acrylic acid ester polymer (A) is preferably 25 mgKOH / g or less, more preferably 20 mgKOH / g or less, particularly preferably 15 mgKOH / g or less, and even more preferably 12 mgKOH / g or less. When the hydroxyl value is within the above range, the resulting pressure-sensitive adhesive is likely to satisfy the storage modulus and gel fraction described above. In particular, the resulting pressure-sensitive adhesive has an appropriate number of crosslinking points, which makes it easy to form a crosslinked structure that is likely to exhibit flexibility. Therefore, even when the pressure-sensitive adhesive layer is thin, it is likely to exhibit suitable adhesive strength and adhesion, and it will have excellent conformability to adherends such as polarizing plates and retardation films, and will exhibit excellent durability.

[0070] Furthermore, when the hydroxyl value of the (meth)acrylic acid ester polymer (A) is within the above range, the acid value of the (meth)acrylic acid ester polymer (A) is preferably 5 mgKOH / g or less, more preferably 3 mgKOH / g or less, particularly preferably 1 mgKOH / g or less, and even more preferably 0.5 mgKOH / g or less. This makes it possible to suppress acid-related defects even when the object to which the pressure-sensitive adhesive is applied is an object that would be affected by acid, such as a transparent conductive film or metal film such as tin-doped indium oxide (ITO). Note that the lower limit of the acid value of the (meth)acrylic acid ester copolymer (A) is preferably as small as possible, and therefore 0 mgKOH / g is particularly preferred.

[0071] Here, the hydroxyl value and acid value in this specification are basically theoretical values ​​derived from the blending ratio of the (meth)acrylic acid ester polymer (A), and when the theoretical values ​​cannot be derived, values ​​measured in accordance with JIS K0070 are used.

[0072] In the pressure-sensitive adhesive composition P, the (meth)acrylic acid ester polymer (A) may be used singly or in combination of two or more kinds.

[0073] The content of the (meth)acrylic acid ester polymer (A) in the adhesive composition P according to this embodiment is preferably 60% by mass or more, particularly preferably 70% by mass or more, and even more preferably 75% by mass or more. The content of the (meth)acrylic acid ester polymer (A) is preferably 90% by mass or less, particularly preferably 85% by mass or less, and even more preferably 80% by mass or less. By ensuring that the content of the (meth)acrylic acid ester polymer (A) is within the above range, the optical properties, storage modulus, gel fraction, adhesive strength, and the like described above are likely to be satisfied.

[0074] (1-2) Crosslinking agent (B) The crosslinking agent (B) crosslinks the (meth)acrylic acid ester polymer (A) by heating the pressure-sensitive adhesive composition P, and can form a good three-dimensional network crosslinked structure, which makes it easier to satisfy the storage modulus, gel fraction, adhesive strength, etc.

[0075] The crosslinking agent (B) may be any agent that reacts with the reactive functional groups of the (meth)acrylic acid ester polymer (A). Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent that has excellent reactivity with hydroxyl groups and carboxyl groups, and isocyanate-based crosslinking agents are particularly preferred. The crosslinking agent (B) may be used alone or in combination of two or more.

[0076] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret and isocyanurate forms thereof, as well as adducts thereof that are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferred from the viewpoint of reactivity with hydroxyl groups and carboxyl groups.

[0077] The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition P is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). The content is also preferably 1.0 part by mass or less, particularly preferably 0.8 parts by mass or less, and even more preferably 0.5 parts by mass or less. When the content of the crosslinking agent (B) is within the above range, the resulting pressure-sensitive adhesive is more likely to satisfy the aforementioned storage modulus, gel fraction, adhesive strength, etc.

[0078] (1-3) Active energy ray-curable component (C) When the adhesive composition P according to the present embodiment contains an active energy ray-curable component (C), it is presumed that in the adhesive obtained by thermally crosslinking and active energy ray-curing the adhesive composition P, the active energy ray-curable components (C) polymerize with each other, and the polymerized active energy ray-curable components (C) become entangled in the crosslinked structure (three-dimensional network structure) of the (meth)acrylic acid ester polymer (A). An adhesive having such a higher-order structure easily satisfies the storage modulus described above and exhibits very excellent durability.

[0079] The active energy ray-curable component (C) is not particularly limited as long as it is a component that can be cured by irradiation with active energy rays and can provide the above-mentioned effects, and may be any of a monomer, oligomer, or polymer, or a mixture thereof. Among them, a polyfunctional acrylate-based monomer that can easily provide a pressure-sensitive adhesive that satisfies the above-mentioned storage modulus is preferably mentioned.

[0080] Examples of polyfunctional acrylate monomers include bifunctional monomers such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated isocyanuric acid di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; trimethylolpropane diacrylate; Examples of the acrylate include trifunctional acrylates such as propane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris-(2-(meth)acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate; tetrafunctional acrylates such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional acrylates such as propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional acrylates such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. These may be used alone or in combination of two or more. From the viewpoint of excellent compatibility with the (meth)acrylic acid ester polymer (A), the polyfunctional acrylate monomer preferably has a molecular weight of less than 1000. By using such a polyfunctional acrylate monomer with excellent compatibility, the resulting pressure-sensitive adhesive is more likely to satisfy the optical properties described above.

[0081] Among the above, from the viewpoint of making it easier for the storage modulus, gel fraction, and adhesive strength of the resulting pressure-sensitive adhesive to be satisfied, polyfunctional acrylate monomers containing an isocyanurate structure in the molecule and polyfunctional acrylate monomers containing a trimethylolpropane structure in the molecule are preferred, and among these, polyfunctional acrylate monomers containing an isocyanurate structure in the molecule are particularly preferred. As the polyfunctional acrylate monomer containing an isocyanurate structure in the molecule, tris-(2-(meth)acryloxyethyl)isocyanurate is preferred, and tris-(2-acryloxyethyl)isocyanurate is particularly preferred. As the polyfunctional acrylate monomer containing a trimethylolpropane structure in the molecule, trimethylolpropane tri(meth)acrylate is preferred, and trimethylolpropane triacrylate is particularly preferred.

[0082] The content of the active energy ray-curable component (C) in the pressure-sensitive adhesive composition P is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, particularly preferably 12 parts by mass or more, and even more preferably 15 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). Furthermore, the content is preferably 30 parts by mass or less, more preferably 26 parts by mass or less, particularly preferably 22 parts by mass or less, and even more preferably 18 parts by mass or less. By having the content of the active energy ray-curable component (C) within the above range, the storage modulus and gel fraction described above are more easily satisfied, and the resulting pressure-sensitive adhesive can be made to have better durability and excellent lamination properties.

[0083] (1-4) Photopolymerization initiator (D) The pressure-sensitive adhesive composition P preferably further contains a photopolymerization initiator (D). However, the maximum absorption wavelength of this photopolymerization initiator (D) is preferably different from the maximum absorption wavelength of the ultraviolet absorber (E) described below. This allows the photopolymerization initiator (D) to be cleaved without any problems when irradiated with active energy rays having a wavelength sufficient to cleave the photopolymerization initiator (D), without being inhibited by the ultraviolet absorber (E). As a result, the curing reaction of the active energy ray-curable component (C) proceeds smoothly, making it easier to satisfy the storage modulus requirement described above. In this specification, the "maximum absorption wavelength" refers to the maximum absorption wavelength of absorbance at a wavelength of 200 to 500 nm in a 0.1% by mass acetonitrile solution.

[0084] Here, the active energy rays in this embodiment preferably emit light with substantial intensity in a wavelength range exceeding 365 nm. The wavelength range is preferably 380 to 450 nm, and more preferably 390 to 430 nm. Furthermore, when the maximum emission intensity at 365 nm or less (which usually has a maximum peak intensity around 365 nm) is taken as 100%, the active energy rays preferably have an intensity of 20% or more in at least a part of the wavelength range.

[0085] The photopolymerization initiator (D) preferably has a light absorption wavelength peak region of 400 nm or more, more preferably 410 nm or more, and particularly preferably 420 nm or more. This allows the photopolymerization initiator (D) to cleave without any problems even when irradiated with the above-mentioned active energy rays. As a result, the curing reaction of the active energy ray-curable component (C) proceeds smoothly, making it easier to satisfy the above-mentioned storage modulus. In this specification, the "light absorption wavelength peak region" refers to a wavelength region having an absorbance of 20% or more of the maximum absorbance.

[0086] The photopolymerization initiator (D) preferably has a maximum absorption wavelength of 350 nm or longer, particularly 360 nm or longer, and even more preferably 370 nm or longer. When there are multiple maximum absorption wavelengths with absorbance in the 200-500 nm wavelength range, it is sufficient that at least one of the maximum absorption wavelengths is within the above range. This ensures that the photopolymerization initiator (D) is less susceptible to inhibition by the ultraviolet absorber (E) described below when irradiated with the active energy rays, and cleaves without any problems, further improving the curability of the active energy ray-curable component (C). The resulting pressure-sensitive adhesive has high cohesive strength, making it easier to satisfy the storage modulus and gel fraction requirements described above. While the upper limit of the maximum absorption wavelength is not particularly limited, from the viewpoint of preventing the progress of the curing reaction when the pressure-sensitive adhesive layer 11 is stored under ambient light such as fluorescent light, it is preferably 450 nm or shorter, more preferably 430 nm or shorter, even more preferably 410 nm or shorter, and even more preferably 400 nm or shorter.

[0087] From the viewpoints of being less susceptible to inhibition by the ultraviolet absorber (E) described below, of allowing the photopolymerization initiator (D) to cleave without problems, and of further improving the curability of the active energy ray-curable component (C), the absorbance at a wavelength of 380 nm of an acetonitrile solution (hereinafter sometimes referred to as a "photopolymerization initiator solution") having a concentration of 0.1 mass % of the photopolymerization initiator (D) is preferably 0.3 or more, more preferably 0.5 or more, and particularly preferably 1 or more. The absorbance at a wavelength of 400 nm of the above-mentioned photopolymerization initiator solution is preferably 0.3 or more, more preferably 0.5 or more, and particularly preferably 0.9 or more. The absorbance at a wavelength of 410 nm of the above-mentioned photopolymerization initiator solution is preferably 0.3 or more, more preferably 0.5 or more, and particularly preferably 0.9 or more. The absorbance at a wavelength of 420 nm of the above-mentioned photopolymerization initiator solution is preferably 0.3 or more, more preferably 0.5 or more. The absorbance at a wavelength of 430 nm of the photopolymerization initiator solution described above is preferably 0.1 or higher, more preferably 0.2 or higher. The upper limit of the absorbance at wavelengths of 380 nm, 400 nm, 410 nm, 420 nm, and 430 nm of the photopolymerization initiator solution described above is not particularly limited, but each is typically preferably 2.5 or lower, and particularly preferably 2.0 or lower. If the absorbance exceeds 2.5, the curing reaction of the active energy ray-curable component (C) caused by the photopolymerization initiator (D) may progress due to ambient light, such as fluorescent light, during the formation or storage of the pressure-sensitive adhesive sheet, resulting in reduced durability during subsequent use. The method for measuring the absorbance of the photopolymerization initiator (D) is as shown in the test examples described below.

[0088] Examples of such photopolymerization initiators (D) include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc. These may be used alone or in combination of two or more.

[0089] The content of the photopolymerization initiator (D) in the pressure-sensitive adhesive composition P is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the active energy ray-curable component (C). The content of the photopolymerization initiator (D) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less. When the content of the photopolymerization initiator (D) is within the above range, the photopolymerization initiator (D) is less likely to be inhibited by the ultraviolet absorber (E) described below, and the photopolymerization initiator (D) is cleaved without any problems, further improving the curability of the active energy ray-curable component (C). This increases the cohesive strength of the resulting pressure-sensitive adhesive, making it easier to satisfy the storage modulus and gel fraction requirements described above.

[0090] (1-5) Ultraviolet absorber (E) The ultraviolet absorber (E) used has a light transmittance difference YX and a light transmittance ratio Y / X that satisfy the following formulas (I) and (II): The maximum absorption wavelength of the ultraviolet absorber (E) is preferably different from the maximum absorption wavelength of the above-mentioned photopolymerization initiator (D). YX≧60 (I) Y / X≧4 (II)

[0091] The adhesive composition P preferably contains a first ultraviolet absorber (E1) and a second ultraviolet absorber (E2) as the ultraviolet absorber (E). The first ultraviolet absorber (E1) and the second ultraviolet absorber (E2) preferably have different maximum absorption wavelengths. This makes it easier for the light transmittance difference and light transmittance ratio to satisfy the above formulas (I) and (II), thereby exhibiting excellent ultraviolet absorption, especially for ultraviolet rays in the long wavelength region (near 400 nm) close to visible light, and also exhibiting excellent visible light transmittance, resulting in a display having excellent image visibility.

[0092] The first ultraviolet absorber (E1) preferably has a lower limit of the absorption maximum wavelength of 365 nm or more, more preferably 380 nm or more, particularly preferably 390 nm or more, and even more preferably greater than 400 nm. Meanwhile, the upper limit of the absorption maximum wavelength is preferably 420 nm or less, particularly preferably 410 nm or less, and even more preferably 405 nm or less. When there are multiple absorption maximums with absorbance in the 200 to 500 nm wavelength range, it is sufficient that at least one of the absorption maximum wavelengths is within the above range. By having a maximum absorption wavelength within the above range, the photopolymerization initiator (D) is less likely to be inhibited by the first ultraviolet absorber (E1) when irradiated with the active energy rays, which further improves the curability of the active energy ray-curable component (C). The resulting pressure-sensitive adhesive has high cohesive strength, making it easier to satisfy the storage modulus and gel fraction requirements described above. Furthermore, the light transmittance at a wavelength of 430 nm tends to reach a desired value, and the light transmittance difference and light transmittance ratio tend to satisfy the above formulas (I) and (II).

[0093] Examples of the first ultraviolet absorber (E1) include compounds such as benzophenones, benzotriazoles, benzoates, benzoxazinones, methines, triazines, phenyl salicylates, cyanoacrylates, and nickel complex salts, and these compounds may be used alone or in combination of two or more.Among the first ultraviolet absorbers (E1), it is preferable to use benzophenones, benzotriazoles, methines, and triazines. Specifically, as the first ultraviolet absorber (E1), "FDB-009" (maximum absorption wavelength: 402 nm) or "FDB-001" (maximum absorption wavelength: 420 nm) manufactured by Yamada Chemical Co., Ltd. can be used, and among them, "FDB-009" is preferably used.

[0094] The content of the first ultraviolet absorber (E1) in the pressure-sensitive adhesive composition P is preferably an amount that satisfies the following condition: That is, when the content of the first ultraviolet absorber (E1) in the pressure-sensitive adhesive layer 11 is α1 mass % and the thickness of the pressure-sensitive adhesive layer 11 is β μm, the amount is preferably an amount that satisfies the following formula (III): 0.1≦α1×β≦60 …(III) When the content of the first ultraviolet absorber (E1) is an amount that satisfies the above conditions, the light transmittance difference and light transmittance ratio of the pressure-sensitive adhesive layer 11 tend to satisfy the above formulas (I) and (II). Furthermore, in the resulting pressure-sensitive adhesive, precipitation of the first ultraviolet absorber (E1) can be suppressed even after durability conditions.

[0095] From the above viewpoints, the lower limit of α1×β in the above formula (III) is preferably 0.5 or more, more preferably 1 or more, particularly preferably 3 or more, and even more preferably 5 or more. The upper limit of α1×β in the above formula (III) is preferably 45 or less, more preferably 30 or less, particularly preferably 15 or less, and even more preferably 10 or less.

[0096] The upper limit of the absorption maximum wavelength of the second ultraviolet absorber (E2) is preferably 390 nm or less, more preferably 380 nm or less, more preferably 370 nm or less, particularly preferably 360 nm or less, and even more preferably less than 360 nm. Meanwhile, the lower limit of the absorption maximum wavelength is preferably 200 nm or more, particularly preferably 250 nm or more, and even more preferably 280 nm or more. When there are multiple absorption maximums with absorbance in the wavelength range of 200 to 500 nm, it is sufficient that at least one of the absorption maximum wavelengths is within the above range. By having the absorption maximum wavelength within the above range, the photopolymerization initiator (D) is less likely to be inhibited by the second ultraviolet absorber (E2) when irradiated with the active energy rays, which further improves the curability of the active energy ray-curable component (C). The resulting pressure-sensitive adhesive has high cohesive strength, making it easier to satisfy the storage modulus and gel fraction requirements described above. Furthermore, the light transmittance at a wavelength of 400 nm tends to reach a desired value, and the light transmittance difference and light transmittance ratio tend to satisfy the above formulas (I) and (II).

[0097] Examples of the second ultraviolet absorber (E2) include compounds such as benzophenones, benzotriazoles, benzoates, benzoxazinones, triazines, phenyl salicylates, cyanoacrylates, and nickel complex salts, and one type may be used alone or two or more types may be used in combination.

[0098] Among the second ultraviolet absorbers (E2), it is preferable to use benzophenone compounds or triazine compounds. These compounds tend to have excellent compatibility with the (meth)acrylic acid ester polymer (A) and the active energy ray-curable component (C), etc., and the resulting pressure-sensitive adhesive is likely to satisfy the optical properties described above.

[0099] Preferred examples of benzophenone compounds include 2,2-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid hydrate, and 2-hydroxy-4-n-octyloxybenzophenone. Preferred examples of triazine compounds include 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3-5-triazine and 2-[4,6-di(2,4-xylyl)-1,3,5-triazin-2-yl]-5-octyloxyphenol. These compounds may be used alone or in combination of two or more.

[0100] The content of the second ultraviolet absorber (E2) in the pressure-sensitive adhesive composition P is preferably an amount that satisfies the following condition: That is, when the content of the second ultraviolet absorber (E2) in the pressure-sensitive adhesive layer 11 is α2 mass % and the thickness of the pressure-sensitive adhesive layer 11 is β μm, the amount is preferably an amount that satisfies the following formula (IV): 10≦α2×β≦100 …(IV) When the content of the second ultraviolet absorber (E2) is an amount that satisfies the above conditions, the light transmittance difference and light transmittance ratio of the pressure-sensitive adhesive layer 11 tend to satisfy the above formulas (I) and (II). Furthermore, in the resulting pressure-sensitive adhesive, precipitation of the second ultraviolet absorber (E2) can be suppressed even after durability conditions.

[0101] From the above viewpoint, the lower limit of α2×β in the above formula (IV) is preferably at least 20, more preferably at least 25, particularly preferably at least 30, and even more preferably at least 35. The upper limit of α2×β in the above formula (IV) is preferably at most 80, more preferably at most 60, particularly preferably at most 50, and even more preferably at most 40.

[0102] The content of the ultraviolet absorber (E) in the pressure-sensitive adhesive composition P is preferably an amount that satisfies the following condition: That is, when the content of the ultraviolet absorber (E) in the pressure-sensitive adhesive layer 11 is α% by mass and the thickness of the pressure-sensitive adhesive layer 11 is β μm, the amount is preferably an amount that satisfies the following formula (V): When the ultraviolet absorber (E) contains a first ultraviolet absorber (E1) and a second ultraviolet absorber (E2), the content of the ultraviolet absorber (E) is the total amount of the content of the first ultraviolet absorber (E1) and the content of the second ultraviolet absorber (E2). 10≦α×β≦120 …(V) When the content of the ultraviolet absorber (E) is an amount that satisfies the above conditions, the light transmittance difference and light transmittance ratio of the pressure-sensitive adhesive layer 11 tend to satisfy the above formulas (I) and (II). Furthermore, in the resulting pressure-sensitive adhesive, precipitation of the ultraviolet absorber (E) can be suppressed even after durability conditions.

[0103] From the above viewpoints, the lower limit of α×β in the above formula (V) is preferably at least 20, more preferably at least 25, particularly preferably at least 35, and even more preferably at least 40. The upper limit of α×β in the above formula (V) is preferably at most 100, more preferably at most 80, particularly preferably at most 60, and even more preferably at most 50.

[0104] (1-6) Silane coupling agent (F) The pressure-sensitive adhesive composition P preferably further contains a silane coupling agent (F), which improves adhesion to the adherend and provides greater durability.

[0105] The silane coupling agent (F) is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the (meth)acrylic acid ester polymer (A) and has optical transparency.

[0106] Examples of such silane coupling agents (F) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; epoxy structure-containing silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; Examples of such silane compounds include amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane, as well as condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These compounds may be used alone or in combination of two or more.

[0107] The content of the silane coupling agent (F) in the pressure-sensitive adhesive composition P is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). The content is preferably 1 part by mass or less, particularly preferably 0.5 parts by mass or less, and even more preferably 0.3 parts by mass or less. By ensuring that the content of the silane coupling agent (F) is within the above range, adhesion to the adherend is improved, making it easier to achieve suitable adhesive strength.

[0108] (1-7) Various additives If desired, various additives commonly used in acrylic pressure-sensitive adhesives, such as antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index modifiers, and rust inhibitors, can be added to the pressure-sensitive adhesive composition P. Note that polymerization solvents and dilution solvents described below are not included in the additives constituting the pressure-sensitive adhesive composition P.

[0109] (2) Production of adhesive composition The adhesive composition P can be produced by producing a (meth)acrylic acid ester polymer (A), mixing the resulting (meth)acrylic acid ester polymer (A) with a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), and an ultraviolet absorber (E), and, if desired, adding a silane coupling agent (F) and additives.

[0110] The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a conventional radical polymerization method. The polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method, using a polymerization initiator as desired. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used in combination.

[0111] Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0112] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, and diacetyl peroxide.

[0113] In the polymerization step, the weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

[0114] Once the (meth)acrylic acid ester polymer (A) is obtained, a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), an ultraviolet absorber (E), and optionally a silane coupling agent (F), additives, and a dilution solvent are added to the solution of the (meth)acrylic acid ester polymer (A) and mixed thoroughly to obtain a solvent-diluted adhesive composition P (coating solution). Note that when any of the above components is used in a solid state or when precipitation occurs when mixed with other components in an undiluted state, that component may be dissolved or diluted alone in a dilution solvent before being mixed with other components.

[0115] Examples of the dilution solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.

[0116] The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are within a range that allows coating, and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted so that the concentration becomes 10 to 60 mass %. Note that the addition of a dilution solvent or the like is not a necessary condition for obtaining the coating solution, and as long as the adhesive composition P has a viscosity that allows coating, it is not necessary to add a dilution solvent. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) itself serves as the dilution solvent.

[0117] (3) Formation of adhesive layer The pressure-sensitive adhesive layer 11 is preferably composed of a pressure-sensitive adhesive obtained by thermally crosslinking and active energy ray curing the pressure-sensitive adhesive composition P. Such a pressure-sensitive adhesive layer 11 can be preferably formed by applying the pressure-sensitive adhesive composition P to a desired object, heat-treating it, and then curing the pressure-sensitive adhesive composition P by irradiating it with active energy rays.

[0118] The heating temperature in the heat treatment is preferably 50 to 150° C., particularly preferably 70 to 120° C. The heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

[0119] Here, the active energy ray refers to an electromagnetic wave or a charged particle beam that has an energy quantum, and specific examples thereof include ultraviolet rays, electron beams, etc. Among active energy rays, ultraviolet rays are particularly preferred because they are easy to handle.

[0120] The ultraviolet irradiation can be performed using a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, or the like, and the amount of ultraviolet irradiation is set to an illuminance of 50 to 1000 mW / cm. 2 The light intensity is preferably about 50 to 10,000 mJ / cm. 2 is preferably 100 to 5000 mJ / cm 2 More preferably, it is 300 to 2000 mJ / cm 2On the other hand, the electron beam irradiation can be carried out by an electron beam accelerator or the like, and the irradiation dose of the electron beam is preferably about 10 to 1000 krad.

[0121] The (meth)acrylic acid ester polymer (A) is crosslinked by the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure) by heat treatment of the adhesive composition P. It is also presumed that the irradiation of the adhesive composition P with active energy rays causes the multiple active energy ray-curable components (C) to polymerize with each other, and the polymerized active energy ray-curable components (C) become entangled in the crosslinked structure of the (meth)acrylic acid ester polymer (A).

[0122] 1-2.Release sheet Release sheets 12a and 12b protect adhesive layer 11 until adhesive sheet 1 is used, and are peeled off when adhesive sheet 1 (adhesive layer 11) is to be used. In adhesive sheet 1 according to this embodiment, one or both of release sheets 12a and 12b are not necessarily required.

[0123] Examples of materials that can be used as the release sheets 12a and 12b include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, and fluororesin films. Crosslinked films of these materials can also be used. Furthermore, laminated films of these materials can also be used.

[0124] The release surfaces of the release sheets 12a and 12b (particularly the surfaces in contact with the pressure-sensitive adhesive layer 11) are preferably subjected to a release treatment. Examples of release agents used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Preferably, one of the release sheets 12a and 12b is a heavy-release type release sheet with a high release strength, and the other is a light-release type release sheet with a low release strength.

[0125] There are no particular restrictions on the thickness of the release sheets 12a and 12b, but it is usually about 20 to 150 μm.

[0126] 2. Manufacturing of adhesive sheets In one example of manufacturing the pressure-sensitive adhesive sheet 1, a coating solution of the pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), and heat treatment is performed to thermally crosslink the pressure-sensitive adhesive composition P to form a coating layer. The release surface of the other release sheet 12b (or 12a) is then superimposed on the coating layer to form a laminate. The coating layer is then cured by irradiating it with active energy rays through the release sheet 12a (or 12b), forming the pressure-sensitive adhesive layer 11.

[0127] In another example of manufacturing the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one of the release sheets 12a (or 12b), a heat treatment is performed to thermally crosslink the adhesive composition P, and a coating layer is formed.After that, while the coating layer is left exposed, active energy rays are irradiated to harden the coating layer, forming the adhesive layer 11, and then the release sheet 12b (or 12a) is laminated on the adhesive layer 11.

[0128] The coating solution of the pressure-sensitive adhesive composition P can be applied by, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, or the like.

[0129] [Optical film with pressure-sensitive adhesive layer] An optical film with a pressure-sensitive adhesive layer according to one embodiment of the present invention comprises an optical film and a pressure-sensitive adhesive layer laminated on at least one side of the optical film. A specific configuration of an optical laminate according to this embodiment is shown in FIG. 2. As shown in FIG. 2, an optical film with a pressure-sensitive adhesive layer 2 according to this embodiment comprises an optical film 21, a pressure-sensitive adhesive layer 11 laminated on one side of the optical member 21, and a release sheet 11b laminated on the side of the pressure-sensitive adhesive layer 11 opposite the optical member 21. This pressure-sensitive adhesive layer 11 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above, and this release sheet 11b is the release sheet 11b of the pressure-sensitive adhesive sheet 1 described above.

[0130] Examples of the optical film 21 include a polarizing plate, a retardation film, a brightness improving film, a viewing angle compensation film, a contrast improving film, a liquid crystal polymer film, a diffusion film, a semi-transmissive reflective film, a transparent conductive film, and a shatterproof film. Among these, a polarizing plate and a retardation film are preferred from the viewpoint of durability.

[0131] Examples of polarizing plates include a polarizing plate in which triacetyl cellulose (TAC) films are bonded to both sides of a polyvinyl alcohol (PVA) polarizer as protective films, a polarizing plate in which one of the TAC films is replaced with a cycloolefin polymer film (COP polarizing plate), or a polarizing plate in which a TAC film is bonded to one side of a PVA polarizer as a protective film. The TAC film may or may not be saponified.

[0132] To manufacture the above-mentioned optical film 2 with a pressure-sensitive adhesive layer, as an example, one of the release sheets 12a of the above-mentioned pressure-sensitive adhesive sheet 1 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is bonded to one side of the optical member 21.

[0133] The pressure-sensitive adhesive layer-attached optical film 2 according to this embodiment can be used by peeling off the release sheet 12b and attaching the exposed pressure-sensitive adhesive layer 11 to a desired optical member.

[0134] [Optical laminate] A specific configuration of an optical laminate according to one embodiment of the present invention is shown in Fig. 3. As shown in Fig. 3, the optical laminate 3 according to this embodiment is configured to include a first optical member 21, a second optical member 31, and a pressure-sensitive adhesive layer 11 located therebetween that bonds the first optical member 21 and the second optical member 31 to each other. This pressure-sensitive adhesive layer 11 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive layer-attached optical film 2 described above (the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1), and the first optical member 21 is the optical member 21 of the pressure-sensitive adhesive layer-attached optical film 2 described above.

[0135] Examples of displays to which the optical laminate 3 can be applied include liquid crystal displays (LCDs), light-emitting diode (LED) displays, organic electroluminescence (organic EL) displays, electronic paper, etc. The display may be a touch panel.

[0136] Examples of the first optical member 21 include those described above, and similar examples of the second optical member 31 include those described above. However, when the first optical member 21 is a polarizing plate, the second optical member 31 is preferably a retardation film. Furthermore, when the first optical member 21 is a retardation film, the second optical member 31 is preferably a polarizing plate or a retardation film.

[0137] To produce the optical laminate 3, for example, the release sheet 12b of the pressure-sensitive adhesive layer-attached optical film 2 is peeled off, and the exposed pressure-sensitive adhesive layer 11 is attached to a second optical member 31. As another example, one release sheet 12a of the pressure-sensitive adhesive sheet 1 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is attached to one surface of a first optical member 21. Next, the other release sheet 12b is peeled off from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is attached to the second optical member 31 to obtain a laminate. As yet another example, the order of attaching the first optical member 21 and the second optical member 31 may be reversed.

[0138] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0139] For example, either one of the release sheets 12a and 12b may be omitted from the pressure-sensitive adhesive sheet 1. Furthermore, the release sheet 12b of the pressure-sensitive adhesive layer-attached optical film 2 may be omitted. [Example]

[0140] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0141] Example 1 1. Preparation of (meth)acrylic acid ester polymer A (meth)acrylic acid ester polymer (A) was prepared by copolymerizing 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid by solution polymerization. The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the following method, and the weight average molecular weight (Mw) was 2,000,000. The acid value of the (meth)acrylic acid ester polymer (A) was 38.9 mg KOH / g, and the hydroxyl value was 0 mg KOH / g.

[0142] 2. Preparation of adhesive composition 100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth)acrylic acid ester polymer (A) obtained in the above step 1, 0.3 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") as a crosslinking agent (B), 15 parts by mass of tris-(2-acryloxyethyl) isocyanurate (C1) as an active energy ray-curable component (C), 2.3 parts by mass of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (D1) as a photopolymerization initiator (D), and ultraviolet A coating solution of adhesive composition P was obtained by mixing 1.5 parts by mass of a long-wavelength UV absorber (manufactured by Yamada Chemical Co., Ltd., product name "FDB-009", maximum absorption wavelength 402 nm) (E1-1) as the first ultraviolet absorber (E1) in the ray absorber (E), 10 parts by mass of 2,2-dihydroxy-4-methoxybenzophenone (E2-1) as the second ultraviolet absorber (E2), and 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane as the silane coupling agent (F), stirring thoroughly, and diluting with methyl ethyl ketone.

[0143] Here, the formulations (solid content equivalent) of the pressure-sensitive adhesive compositions when the (meth)acrylic acid ester polymer (A) is taken as 100 parts by mass (solid content equivalent) are shown in Table 1. Details of the abbreviations and the like shown in Table 1 are as follows. [(Meth)acrylic acid ester polymer (A)] BA: n-butyl acrylate AA: acrylic acid IBXA: Isobornyl acrylate HEA: 2-hydroxyethyl acrylate [Active energy ray-curable component (C)] C1: Tris-(2-acryloxyethyl) isocyanurate C2: Trimethylolpropane triacrylate [Photopolymerization initiator (D)] D1: Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide D2: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide D3: 1-hydroxycyclohexyl phenyl ketone [Ultraviolet absorber (E)] First UV absorber (E1) E1-1: Long wavelength UV absorber (Yamada Chemical Co., Ltd., product name "FDB-009", maximum absorption wavelength 402 nm) Second UV absorber (E2) E2-1: 2,2-dihydroxy-4-methoxybenzophenone (maximum absorption wavelengths: 284 nm, 340 nm) E2-2: Triazine UV absorber (manufactured by BASF Japan, product name "Tinuvin 477", maximum absorption wavelength 356 nm)

[0144] 3. Formation of adhesive layer The coating solution of the pressure-sensitive adhesive composition P obtained in step 2 above was applied using a knife coater to the release-treated surface of a heavy-release release sheet (manufactured by Lintec Corporation, product name "SP-PET752150"), one side of which had been release-treated with a silicone-based release agent, and then the sheet was heated at 90°C for 1 minute to form a coating layer. The surface of the heavy-release release sheet with the coating layer obtained was bonded to the release-treated surface of a light-release release sheet (manufactured by Lintec Corporation, product name "SP-PET381130"), one side of which had been release-treated with a silicone-based release agent.

[0145] Next, the coating layer was irradiated with ultraviolet light through the light release release sheet under the following conditions to cure the coating layer and form a 5 μm thick adhesive layer, thereby producing an adhesive sheet having a configuration of heavy release release sheet / adhesive layer (thickness: 5 μm) / light release release sheet. <Ultraviolet irradiation conditions> -High pressure mercury lamp used ·Illuminance 200mW / cm 2 , light intensity 500mJ / cm 2 The UV illuminance and light intensity meter used is the "UVPF-A1" manufactured by Eye Graphics.

[0146] The thickness of the pressure-sensitive adhesive layer is a value measured in accordance with JIS K7130 using a constant pressure thickness measuring instrument (manufactured by Teclock Corporation, product name "PG-02").

[0147] [Examples 2 to 5, Comparative Examples 1 to 5] Pressure-sensitive adhesive sheets were produced in the same manner as in Example 1, except that the composition of the (meth)acrylic acid ester polymer (A), the type and amount of the active energy ray-curable component (C), the type and amount of the photopolymerization initiator (D), and the type and amount of the ultraviolet absorber (E) were changed as shown in Table 1. The (meth)acrylic acid ester polymer (A) in Example 5 had an acid value of 0 mgKOH / g and a hydroxyl value of 9.7 mgKOH / g.

[0148] Here, the weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> GPC measuring device: Tosoh HLC-8020 GPC columns (passed in the following order): Tosoh Corporation TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0149] [Test Example 1] (Measurement of gel fraction) The pressure-sensitive adhesive sheets obtained in the examples and comparative examples were cut to a size of 80 mm x 80 mm, the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was weighed on a precision balance. The mass of the mesh alone was subtracted to calculate the mass of the pressure-sensitive adhesive alone. This mass was designated M1.

[0150] Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. The adhesive was then removed and air-dried for 24 hours at 23°C and 50% relative humidity, and then dried in an oven at 80°C for 12 hours. After drying, the mass was measured using a precision balance, and the mass of the mesh alone was subtracted to calculate the mass of the adhesive alone. This mass was designated M2. The gel fraction (%) was expressed as (M2 / M1) x 100. The results are shown in Table 2.

[0151] [Test Example 2] (Measurement of storage modulus) The release sheets were peeled off from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and multiple pressure-sensitive adhesive layers were laminated to a thickness of 3 mm. A cylindrical object with a diameter of 8 mm (height of 3 mm) was punched out from the resulting pressure-sensitive adhesive layer laminate, and this was used as a sample.

[0152] The storage modulus (MPa) of the above samples was measured under the following conditions by a torsional shear method using a viscoelasticity measuring device (manufactured by Physica, product name "MCR301") in accordance with JIS K7244-6. The results are shown in Table 2. Measurement frequency: 1Hz Measurement temperature: 23℃

[0153] [Test Example 3] (Measurement of absorbance) A 0.1% by mass acetonitrile solution was prepared for each of the photopolymerization initiators D1 to D3 used in the Examples and Comparative Examples, and the absorbance of the solution in the wavelength range of 200 to 500 nm was measured using an ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometer (Shimadzu Corporation, product name "UV-3600", optical path length 10 mm). Based on the results, the absorbance at wavelengths of 380 nm, 400 nm, 410 nm, 420 nm, and 430 nm, as well as the maximum absorption wavelength (nm) in the absorbance range of 200 to 500 nm, were calculated. The results are as follows:

[0154] [D1 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide)] Absorbance at 380nm: 1.8, absorbance at 400nm: 1.5, absorbance at 410nm: 1, absorbance at 420nm: 0.6, absorbance at 430nm: 0.3 Maximum absorption wavelength: 295nm, 370nm [D2 (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide)] Absorbance at wavelength 380nm: 1.5, absorbance at wavelength 400nm: 0.9, absorbance at wavelength 410nm: 0.3, absorbance at wavelength 420nm: 0, absorbance at wavelength 430nm: 0 Maximum absorption wavelength: 295nm, 368nm, 380nm, 393nm [D3 (1-hydroxycyclohexyl phenyl ketone)] Absorbance at wavelength 380nm: 0, absorbance at wavelength 400nm: 0, absorbance at wavelength 410nm: 0, absorbance at wavelength 420nm: 0, absorbance at wavelength 430nm: 0 Maximum absorption wavelength: 246nm, 280nm, 333nm

[0155] [Test Example 4] (Measurement of light transmittance) The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in each of the Examples and Comparative Examples was attached to a soda-lime glass to prepare a measurement sample. After background measurement using the soda-lime glass, the transmittance of the measurement sample was measured in the range of 200 to 800 nm using an ultraviolet-visible-near-infrared spectrophotometer (Shimadzu Corporation, product name "UV-VIS-NIR SPECTROPHOTOMETER UV-3600"), and the light transmittance (%) at wavelengths of 350 nm, 380 nm, 400 nm, 430 nm, and 500 nm was extracted. The measurement was performed using the attached large sample chamber MPC-3100 without using the built-in integrating sphere. The ultraviolet absorbency was evaluated according to the following evaluation criteria. The results are shown in Table 2. Good: The light transmittance at wavelengths of 350 nm and 400 nm was both less than 20%. Δ1: The light transmittance at a wavelength of 350 nm was less than 20%, but the light transmittance at a wavelength of 400 nm was 20% or more. Δ2: The light transmittance at a wavelength of 400 nm was less than 20%, but the light transmittance at a wavelength of 350 nm was 20% or more. ×: The light transmittance at wavelengths of 400 nm and 350 nm was 20% or more.

[0156] [Test Example 5] (Measurement of adhesive strength) The light-release release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was attached to an easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "PET A4300", thickness: 100 μm) having an easy-adhesion layer, to obtain a heavy-release release sheet / pressure-sensitive adhesive layer / PET film laminate. The resulting laminate was cut into a 25 mm wide, 100 mm long sample.

[0157] The heavy-release release sheet was peeled from the sample at 23°C and 50% RH, and the exposed adhesive layer was attached to alkali-free glass (Corning Incorporated, product name "Eagle XG") and then pressurized in a Kurihara Manufacturing Co., Ltd. autoclave at 0.5 MPa and 50°C for 20 minutes. After leaving the sample at 23°C and 50% RH for 24 hours, the adhesive strength (N / 25 mm) was measured using a tensile tester (Orientec Co., Ltd., product name "Tensilon") at a peel rate of 300 mm / min and a peel angle of 180°. Measurements were conducted in accordance with JIS Z0237:2009 except for the conditions described above. The results are shown in Table 2.

[0158] [Test Example 6] (Durability Evaluation) The light-release release sheet was peeled off from the pressure-sensitive adhesive sheet obtained in each of the Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was attached to a saponified triacetyl cellulose (TAC) protective film of a polarizing plate (50 μm thick) having the TAC protective film, and then cut to a size of 23.5 cm × 30.5 cm.

[0159] Next, the heavy release release sheet was peeled off from the laminate, and the exposed adhesive layer was attached to alkali-free glass (manufactured by Corning Incorporated, product name "Eagle XG"), and then pressurized at 0.5 MPa and 50°C for 20 minutes in an autoclave manufactured by Kurihara Seisakusho, and this was used as an evaluation sample.

[0160] The above evaluation samples were subjected to durability conditions of 85°C, 85% RH, and 500 hours, after which the presence or absence of lifting, peeling, bubbling, and streaks was checked using a 10x magnifying glass. Durability was then evaluated according to the following evaluation criteria. The results are shown in Table 2. ◯: No lifting, peeling, bubbling or streaks were observed. △: No lifting / peeling other than at the edges, bubbles larger than 0.5 mm, or streaks were observed, but lifting / peeling at the edges, bubbles larger than 0.5 mm, and streaks were observed, and it was determined that there was a problem in practical use. ×: Lifting and peeling other than at the edges, bubbles of more than 0.5 mm and streaks were observed, and the product was judged to be unsuitable for practical use.

[0161] [Test Example 7] (Precipitation of UV absorber) Evaluation samples were prepared in the same manner as in Test Example 6 described above. The evaluation samples were left to stand for 12 hours under conditions of 23°C and 50% RH, and the presence or absence of precipitation of the UV absorber in the adhesive of the evaluation sample was visually confirmed. Those samples in which precipitation of the UV absorber was not confirmed were then subjected to durability conditions of 85°C, 85% RH, and 500 hours, after which the presence or absence of precipitation of the UV absorber in the adhesive of the evaluation sample was visually confirmed. Durability was then evaluated according to the following evaluation criteria. The results are shown in Table 2. ◯: No precipitation of the ultraviolet absorber was observed after the durability test. ×: No deposition of the ultraviolet absorber was observed before the durability test, but deposition of the ultraviolet absorber was observed after the durability test. XX: Precipitation of the ultraviolet absorber was confirmed before the test was put under durability conditions.

[0162] [Table 1]

[0163] [Table 2]

[0164] As can be seen from Table 2, the pressure-sensitive adhesive sheets produced in the examples had excellent ultraviolet absorption properties and visible light transmittance, and also had excellent durability even though the pressure-sensitive adhesive layer was a thin film. [Industrial Applicability]

[0165] The pressure-sensitive adhesive sheet according to the present invention is suitably used, for example, for bonding a polarizing plate and a retardation film, or two retardation films together, in a display that requires protection from ultraviolet rays. [Explanation of symbols]

[0166] 1...Adhesive sheet 11...Adhesive layer 12a, 12b...Release sheet 2...Optical film with adhesive layer 21...Optical film 3...Optical laminate 21...First optical film 31...Second optical film

Claims

1. A pressure-sensitive adhesive sheet for optical applications having at least a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive containing at least a cured product of an active energy ray-curable component (C) and an ultraviolet absorber (E), the pressure-sensitive adhesive is obtained from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), the active energy ray-curable component (C), a photopolymerization initiator (D), and the ultraviolet absorber (E), the ultraviolet absorber (E) contains a first ultraviolet absorber (E1) and a second ultraviolet absorber (E2), the first ultraviolet absorber (E1) has a maximum absorption wavelength of 380 nm or more and 420 nm or less; the second ultraviolet absorber (E2) has a maximum absorption wavelength of 200 nm or more and 370 nm or less; the pressure-sensitive adhesive layer has a light transmittance (%) of 20% or less at a wavelength of 350 nm; When the light transmittance (%) of the pressure-sensitive adhesive layer at a wavelength of 400 nm is defined as X and the light transmittance (%) of the pressure-sensitive adhesive layer at a wavelength of 430 nm is defined as Y, the following formulas (I) and (II) are satisfied: The pressure-sensitive adhesive layer has a storage modulus at 23°C of 0.15 MPa or more and 2 MPa or less. A pressure-sensitive adhesive sheet characterized by: Y-X≧60...(I) Y / X≧4...(II)

2. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 0.1 μm or more and 10 μm or less.

3. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the adhesive strength to non-alkali glass is 0.5 N / 25 mm or more.

4. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer has a gel fraction of 40% or more and 100% or less.

5. 5. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a light transmittance (%) of 20% or less at a wavelength of 400 nm.

6. 6. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a light transmittance (%) of 80% or more at a wavelength of 430 nm.

7. 7. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive contains a crosslinked product obtained by crosslinking a (meth)acrylic acid ester polymer.

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the maximum absorption wavelength of the photopolymerization initiator (D) and the maximum absorption wavelength of the ultraviolet absorber (E) are different.

9. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the photopolymerization initiator (D) has a light absorption wavelength peak region of 400 nm or more.

10. The content of the second ultraviolet absorber (E2) in the pressure-sensitive adhesive layer is α ２ The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the following formula (IV) is established when the thickness of the pressure-sensitive adhesive layer is β μm and the mass % is β μm. 10≦α ２ ×β≦80 …(IV)

11. It has two release sheets, The pressure-sensitive adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets. The pressure-sensitive adhesive sheet according to any one of claims 1 to 10.

12. A method for producing the pressure-sensitive adhesive sheet according to any one of claims 1 to 11, The pressure-sensitive adhesive layer is formed by thermally crosslinking and curing with active energy rays an adhesive composition containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), and an ultraviolet absorber (E). A method for producing a pressure-sensitive adhesive sheet, comprising:

13. An optical film; The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 11, laminated on at least one surface of the optical film; An optical film with a pressure-sensitive adhesive layer, comprising:

14. 14. The pressure-sensitive adhesive layer-attached optical film according to claim 13, wherein the optical film is a polarizing plate or a retardation film.

15. a first optical film; a second optical film; and a pressure-sensitive adhesive layer that bonds the first optical film and the second optical film to each other; An optical laminate comprising: The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 11. An optical laminate characterized by:

16. the first optical film is a polarizing plate or a retardation film, The second optical film is a retardation film. The optical laminate according to claim 15 .

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