Adhesive sheet for attaching transparent components

Abstract

The present invention addresses the problem of providing an adhesive sheet which is used for bonding glass plates to each other, and in which discoloration (color loss) can be prevented even when the adhesive sheet is left under high-temperature and high-humidity conditions for a long time. The present invention relates to an adhesive sheet for bonding transparent members, the adhesive sheet including an acrylic polymer and a colorant, wherein the adhesive sheet has an amount of change in total light transmittance of less than 2% when the adhesive sheet is sandwiched by two glass plates and stored for 500 hours in environments of 85 °C and a relative humidity of 85%.

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet for attaching to a transparent member. [Background technology]

[0002] Conventionally, input devices used in combination with display devices such as liquid crystal displays (LCDs) and display devices such as touch panels have been widely used. In the manufacture of these display devices and input devices, transparent pressure-sensitive adhesive sheets are used to bond optical components.

[0003] For example, Patent Document 1 discloses a double-sided pressure-sensitive adhesive sheet comprising a laminate including a flexible substrate layer, a first black layer, a second black layer, and a first pressure-sensitive adhesive layer, and a second pressure-sensitive adhesive layer. In such cases, the pressure-sensitive adhesive sheet used to attach the black layer may be required to have a design that does not impair the black appearance.

[0004] Meanwhile, as a means for imparting a black appearance to a pressure-sensitive adhesive sheet, a method of adding a pigment to the pressure-sensitive adhesive sheet is also known. For example, Patent Document 2 discloses a black foil-shaped pressure-sensitive adhesive containing an adhesive component, a black pigment, and a styrene-maleic acid resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-060435 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-32430 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, black adhesive sheets are known that are obtained by adding a black pigment to an adhesive layer. However, when such adhesive sheets are used to bond glass plates together and are left under high temperature and humidity conditions for a long period of time, the adhesive layer can fade (discolor), which has been a problem.

[0007] Therefore, in order to solve these problems of the conventional technology, the inventors have conducted research with the aim of providing an adhesive sheet that can be used to bond glass plates together and that can prevent fading (color loss) even when left under high temperature and high humidity conditions for a long period of time. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the inventors have found that by sandwiching an adhesive sheet for bonding transparent members, which contains an acrylic polymer and a colorant, between two glass plates and storing it in an environment of 85°C and 85% relative humidity for 500 hours, and keeping the change in total light transmittance to less than 2%, it is possible to prevent fading (discoloration) of the adhesive layer even when the adhesive sheet is used to bond glass plates and further stored under high temperature and high humidity conditions for a long period of time. Specifically, the present invention has the following configuration.

[0009] [1] A pressure-sensitive adhesive sheet for attaching transparent members, comprising an acrylic polymer and a colorant, An adhesive sheet for attaching transparent materials, which exhibits a change in total light transmittance of less than 2% when sandwiched between two glass plates and stored for 500 hours in an environment of 85°C and 85% relative humidity. [2] The pressure-sensitive adhesive sheet for attaching transparent members according to [1], wherein the colorant is a black metal oxide. [3] The pressure-sensitive adhesive sheet for attaching transparent members according to [1] or [2], which has a total light transmittance of 30% or more and less than 85%. [4] The pressure-sensitive adhesive sheet for attaching to a transparent member according to any one of [1] to [3], further comprising an acid scavenger. [5] The pressure-sensitive adhesive sheet for attaching transparent members according to [4], wherein the acid scavenger is a compound having at least one group selected from an oxazoline group and a carbodiimide group. [6] The pressure-sensitive adhesive sheet for applying to a transparent member according to any one of [1] to [5], wherein the colorant has an average primary particle size of 0.01 μm or more and less than 5 μm. [7] A laminate having a surface layer on one side of the pressure-sensitive adhesive sheet for applying to a transparent member according to any one of [1] to [6], and an indicator on the other side. [8] The laminate according to [7], wherein the surface layer is a glass layer or a resin layer. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an adhesive sheet that can be used to bond glass plates together and can prevent discoloration (color loss) even when left under high-temperature and high-humidity conditions for a long period of time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a cross section of a pressure-sensitive adhesive sheet having a release sheet. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the constituent elements may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] (adhesive sheet) The present invention relates to a pressure-sensitive adhesive sheet for applying to a transparent member, which comprises an acrylic polymer and a colorant. When the pressure-sensitive adhesive sheet for applying to a transparent member is sandwiched between two glass plates and stored for 500 hours in an environment of 85°C and 85% relative humidity, the change in total light transmittance is less than 2%. The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet used for applying to a transparent member, and the transparent member is preferably an optical member. That is, the pressure-sensitive adhesive sheet for applying to a transparent member of the present invention is preferably a pressure-sensitive adhesive sheet for applying to an optical member.

[0014] The adhesive sheet for bonding transparent members of the present invention (hereinafter also referred to as adhesive sheet) has the above-mentioned configuration, and therefore can prevent discoloration (color loss) of the adhesive sheet even when used to bond glass plates and then placed under high-temperature, high-humidity conditions for a long period of time. In an adhesive sheet in which discoloration (color loss) is suppressed in this way, coloring by a colorant or the like can be maintained for a long period of time. Therefore, the adhesive sheet for bonding transparent members of the present invention may be an adhesive sheet for use under high-temperature, high-humidity conditions, or may be an adhesive sheet for use under conditions of 85°C or higher and a relative humidity of 85% or higher.

[0015] Conventionally, when glass plates are laminated to both sides of a pressure-sensitive adhesive sheet containing a colorant and the resulting laminate is placed in a high-temperature, high-humidity environment for a long period of time, the pressure-sensitive adhesive sheet experiences discoloration. This phenomenon is particularly pronounced when a metal oxide is used as the colorant. Therefore, the present inventors decided to control the composition and manufacturing conditions of a pressure-sensitive adhesive sheet containing a colorant (metal oxide) to reduce the change in total light transmittance of the pressure-sensitive adhesive sheet to less than a predetermined value. As a result, the present invention has found that discoloration (discoloration) is suppressed even in pressure-sensitive adhesive sheets containing a colorant (metal oxide), and that the coloring due to the colorant (metal oxide) is maintained even in a high-temperature, high-humidity environment.

[0016] The present inventors have also discovered that when a pressure-sensitive adhesive sheet containing a colorant is placed under high-temperature, high-humidity conditions (e.g., 85°C or higher, relative humidity of 85% or higher) for a long period of time (e.g., 500 hours or more) and glass plates are laminated to both sides of the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet undergoes discoloration. The discoloration of the pressure-sensitive adhesive sheet of the present invention is not observed when the pressure-sensitive adhesive sheet containing a colorant is simply placed under high-temperature conditions of 85°C or higher, or when a resin film or the like is laminated to at least one side of the pressure-sensitive adhesive sheet even when the pressure-sensitive adhesive sheet is placed under specified conditions of relative humidity of 85% or higher for a long period of time (e.g., 500 hours or more). Thus, the present invention has discovered the phenomenon of discoloration of a pressure-sensitive adhesive sheet when the pressure-sensitive adhesive sheet is placed under high-temperature, high-humidity conditions (e.g., 85°C or higher, relative humidity of 85% or higher) for a long period of time (e.g., 500 hours or more) and glass plates are laminated to both sides of the pressure-sensitive adhesive sheet, and has further succeeded in suppressing this discoloration phenomenon.

[0017] In this specification, the change in total light transmittance of a pressure-sensitive adhesive sheet can be calculated by placing a pressure-sensitive adhesive sheet (laminate) with glass plates attached to both sides in an environment of 85°C and 85% relative humidity, and measuring the total light transmittance before and after 500 hours. The change in total light transmittance is a value calculated using the following formula. Change (%) = (85°C, 85% relative humidity treatment) rear Total light transmittance of laminate (treated at 85°C and 85% relative humidity) before (total light transmittance of laminate) The amount of change in total light transmittance is preferably less than 2%, more preferably 1.8% or less, even more preferably 1.5% or less, and particularly preferably 1.2% or less.

[0018] In this specification, the colorfastness of a pressure-sensitive adhesive sheet can be evaluated by measuring the change in L* value before and after 500 hours when a pressure-sensitive adhesive sheet (laminate) with glass plates attached to both sides is placed in an environment of 85°C and 85% relative humidity. The change in L* value is a value calculated using the following formula. Change = (processing rearL* value of the sample)-(processing before (L* value of sample) The change in the L* value is preferably less than 1.0, more preferably 0.9 or less, and even more preferably 0.8 or less.

[0019] Furthermore, in the present invention, when the pressure-sensitive adhesive sheet is attached to a display or the like displaying a black screen, the design of the display can be improved. Specifically, when the pressure-sensitive adhesive sheet of the present invention is attached to a display displaying a black screen, the degree of black color development of the display (desirability of the degree of black color development) can be increased, thereby improving the design of the display and display devices having the display. Furthermore, even in a display that is not displaying a black screen, the degree of black color development of the display is increased by attaching the pressure-sensitive adhesive sheet, thereby emphasizing the sense of unity with the surroundings and improving the design.

[0020] The total light transmittance of a pressure-sensitive adhesive sheet (laminate) having glass plates bonded to both sides thereof before treatment at 85°C and a relative humidity of 85% is preferably less than 85%, more preferably 80% or less, and even more preferably 75% or less. The total light transmittance of the laminate before treatment at 85°C and a relative humidity of 85% is preferably 30% or more. Furthermore, the total light transmittance of the pressure-sensitive adhesive sheet (laminate) having glass plates bonded to both sides thereof after being placed in an environment of 85°C and a relative humidity of 85% for 500 hours is preferably less than 85%, more preferably 80% or less, and even more preferably 75% or less. The total light transmittance of the laminate after treatment at 85°C and a relative humidity of 85% is preferably 40% or more. By setting the total light transmittance of the laminate within the above range, the degree of black color development in displays and the like can be more effectively improved. The total light transmittance of a pressure-sensitive adhesive sheet (laminate) with glass plates bonded to both sides is a value measured by the following method. First, the pressure-sensitive adhesive sheet (laminate) with glass plates bonded to both sides is treated in an autoclave at 40°C and 5 atmospheres for 30 minutes. Next, the total light transmittance of the laminate is measured in accordance with JIS K 7150. This measurement is performed three times, and the average value is used as the total light transmittance of the laminate. For example, an integrating sphere light transmittance measuring device (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.) can be used to measure the total light transmittance. Note that the total light transmittance of a pressure-sensitive adhesive sheet (laminate) with glass plates bonded to both sides is the same as that of a pressure-sensitive adhesive sheet, and therefore the total light transmittance of a pressure-sensitive adhesive sheet (laminate) with glass plates bonded to both sides is used as the total light transmittance of the pressure-sensitive adhesive sheet.

[0021] The haze of the pressure-sensitive adhesive sheet is not particularly limited to a lower limit, but is preferably, for example, 0.1% or more. Furthermore, the haze of the pressure-sensitive adhesive sheet is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, and particularly preferably 15% or less. By keeping the haze of the pressure-sensitive adhesive sheet within the above range, the degree of black color development in displays and the like can be more effectively improved.

[0022] In the pressure-sensitive adhesive sheet of this embodiment, the product of the total light transmittance and haze value of the pressure-sensitive adhesive sheet is preferably 300 or less, more preferably 250 or less, even more preferably 200 or less, and particularly preferably 170 or less. The lower limit of the product of the total light transmittance and haze value of the pressure-sensitive adhesive sheet is not particularly limited, but considering the haze and total light transmittance for optical applications, it is preferably 10 or more. In particular, the pressure-sensitive adhesive sheet preferably has a total light transmittance of 40% or more and a haze of 6% or less, and more preferably a total light transmittance of 90% or less and a haze of 0.1% or more. By setting the product of the total light transmittance and haze value within the above range and setting the total light transmittance and haze of the pressure-sensitive adhesive sheet within the specified range, the degree of black color development of a display or the like can be more effectively increased while also more effectively improving the visibility of the display or the like.

[0023] The thickness of the pressure-sensitive adhesive sheet is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 50 μm or more. The thickness of the pressure-sensitive adhesive sheet is preferably 5000 μm or less, more preferably 3000 μm or less, and even more preferably 1000 μm or less. By making the thickness of the pressure-sensitive adhesive sheet equal to or less than the upper limit, water vapor intrusion from the edges can be prevented, thereby increasing durability. On the other hand, by making the thickness of the pressure-sensitive adhesive sheet equal to or greater than the lower limit, the pressure-sensitive adhesive sheet can be easily handled.

[0024] The pressure-sensitive adhesive sheet of the present invention may be a single-layer pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may be a single-sided pressure-sensitive adhesive sheet having a substrate (preferably a transparent substrate) on one side, or a double-sided pressure-sensitive adhesive sheet. Examples of double-sided pressure-sensitive adhesive sheets include a single-layer pressure-sensitive adhesive sheet consisting of a pressure-sensitive adhesive layer, a multilayer pressure-sensitive adhesive sheet having a plurality of laminated pressure-sensitive adhesive layers, a multilayer pressure-sensitive adhesive sheet having another pressure-sensitive adhesive layer laminated between two pressure-sensitive adhesive layers, a multilayer pressure-sensitive adhesive sheet having a support laminated between two pressure-sensitive adhesive layers, and a multilayer pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer laminated on one side of a support and another pressure-sensitive adhesive layer laminated on the other side. When the double-sided pressure-sensitive adhesive sheet has a support, a transparent support is preferably used as the support. As with the transparent substrate, a general film used in the optical field can be used as the support. Such double-sided pressure-sensitive adhesive sheets have excellent transparency as a whole, and are therefore suitable for use in bonding transparent members together.

[0025] 1, the present invention may also relate to a pressure-sensitive adhesive sheet with a release sheet, which has release sheets 12a and 12b on both surfaces of a pressure-sensitive adhesive sheet 11. Examples of release sheets include a release laminate sheet having a release sheet substrate and a release agent layer provided on one surface of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate.

[0026] Paper or polymer film is used as the substrate for the release sheet in the release laminate sheet. For optical applications, polymer film is preferably used to prevent the inclusion of foreign matter. As the release agent constituting the release agent layer, for example, a general-purpose addition or condensation type silicone-based release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone-based release agent with high reactivity is preferably used. Specific examples of silicone-based release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone Co., Ltd., and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. In addition, silicone-based release agents containing SiO2 units and (CH3)3SiO 1 / 2 Unit or CH2=CH(CH3)SiO 1 / 2 It is preferable to contain a silicone resin, which is an organosilicon compound having a unit. Specific examples of silicone resins include BY24-843, SD-7292, and SHR-1404 manufactured by Dow Corning Toray Silicone Co., Ltd., and KS-3800 and X92-183 manufactured by Shin-Etsu Chemical Co., Ltd. Commercially available peelable laminate sheets may be used, such as a heavy-duty separator film manufactured by Teijin DuPont Films Co., Ltd., which is a release-treated polyethylene terephthalate film, and a light-duty separator film manufactured by Teijin DuPont Films Co., Ltd., which is a release-treated polyethylene terephthalate film.

[0027] When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, it is preferable to have a pair of release sheets with different release strengths. That is, to facilitate peeling, it is preferable that the release properties of one release sheet differ from those of the other release sheet. If the releasability from one side differs from that from the other, it becomes easy to peel off only the release sheet with the higher releasability first.

[0028] The gel fraction of the pressure-sensitive adhesive sheet of the present invention is preferably 30 to 100%, more preferably 40 to 100%, and even more preferably 50 to 100%.

[0029] (Adhesive composition) The pressure-sensitive adhesive sheet of the present invention contains an acrylic polymer and a colorant. The pressure-sensitive adhesive sheet of the present invention preferably further contains an acid scavenger.

[0030] (acrylic polymer) The acrylic polymer is not particularly limited as long as it contains an acrylic monomer unit, but preferably contains, for example, a non-crosslinkable (meth)acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group. In this specification and claims, the term "unit" refers to a repeating unit (monomer unit) that constitutes a polymer.

[0031] The non-crosslinkable (meth)acrylic acid ester unit (a1) is a repeating unit derived from a (meth)acrylic acid alkyl ester. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate. These may be used alone or in combination of two or more. Among the above (meth)acrylic acid alkyl esters, at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, n-dodecyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferred because it increases adhesion.

[0032] The acrylic monomer unit (a2) having a crosslinkable functional group is preferably at least one selected from the group consisting of a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, and a glycidyl group-containing monomer unit. That is, the acrylic polymer preferably has at least one crosslinkable functional group selected from the group consisting of a carboxy group, a hydroxy group, an amino group, an amide group, a glycidyl group, and an isocyanate group. Examples of the carboxyl group-containing monomer unit include acrylic acid and methacrylic acid. The hydroxy group-containing monomer unit is a repeating unit derived from a hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, (meth)acrylic acids [(mono-, di-, or poly)alkylene glycols] such as mono(diethylene glycol) (meth)acrylate, and (meth)acrylic acid lactones such as monocaprolactone (meth)acrylate. Examples of the amino group-containing monomer unit include repeating units derived from amino group-containing monomers such as (meth)acrylamide and allylamine. Examples of the glycidyl group-containing monomer unit include repeating units derived from glycidyl group-containing monomers such as glycidyl (meth)acrylate.

[0033] The content of the acrylic monomer unit (a2) having a crosslinkable functional group in the acrylic polymer is preferably 0.01 to 40 mass %, more preferably 0.5 to 35 mass %. By setting the content of the acrylic monomer unit (a2) having a crosslinkable functional group within the above range, it becomes easier to control the crosslinkability and adhesiveness of the acrylic polymer.

[0034] When the acrylic monomer unit (a2) having a crosslinkable functional group is a carboxyl group-containing monomer unit, the content of the carboxyl group-containing monomer unit in the acrylic polymer is preferably 0.1% by mass or less, more preferably 0.05% by mass or less. It is also preferable that the content of the carboxyl group-containing monomer unit in the acrylic polymer is 0% by mass. By adjusting the content of the carboxyl group-containing monomer unit within the above range, a so-called acid-free pressure-sensitive adhesive sheet can be obtained. This makes it possible to more effectively improve the colorfastness of the pressure-sensitive adhesive sheet.

[0035] The acrylic polymer may further contain units derived from an alkoxyalkyl group-containing (meth)acrylate. The alkoxyalkyl group-containing (meth)acrylate is an alkoxyalkyl (meth)acrylate. As the alkoxyalkyl (meth)acrylate, for example, an alkoxyalkyl (meth)acrylate in which the alkoxy group has 1 to 12 carbon atoms and the alkylene group bonded to the alkoxy group has 1 to 18 carbon atoms is preferred. The alkoxy group preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. Furthermore, the alkylene group bonded to the alkoxy group preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, even more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms.

[0036] Examples of such alkoxyalkyl (meth)acrylates include 2-methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxymethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate.

[0037] The acrylic polymer may further contain units derived from a nitrogen-containing monomer. The nitrogen-containing monomer is a monomer containing a nitrogen element in one molecule. Examples of nitrogen-containing monomers include dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylol acrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide, N-vinylcaprolactam, N-vinyl-2-pyrrolidone, dimethylaminoethyl (meth)acrylate, and N-vinylformamide. Among these, the nitrogen-containing monomer is preferably at least one selected from an acrylamide derivative, an amino group-containing monomer, and a nitrogen-containing heterocycle-containing monomer, and more preferably an acrylamide derivative. The acrylamide derivative is more preferably at least one selected from dimethylacrylamide, diethylacrylamide, and acryloylmorpholine, and particularly preferably dimethylacrylamide.

[0038] The acrylic polymer may contain other monomer units as needed. The other monomers may be any monomers copolymerizable with the above-mentioned acrylic monomers, such as (meth)acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylpyrrolidone, and vinylpyridine. The content of other monomer units in the acrylic polymer is preferably 20% by mass or less, and more preferably 15% by mass or less.

[0039] The acid value of the acrylic polymer is preferably 3 mgKOH / g or less, more preferably 1 mgKOH / g or less, and particularly preferably 0.5 mgKOH / g or less. The acid value of the acrylic polymer may be 0 mgKOH / g. By setting the acid value of the acrylic polymer within the above range, the colorfastness of the pressure-sensitive adhesive sheet of the present invention can be more effectively improved.

[0040] The acid value of acrylic polymers is measured in accordance with JIS K 0070 (1992). Specifically, approximately 2 g of sample is weighed out accurately into a 100 ml Erlenmeyer flask using a precision balance, and 10 ml of a 1:1 (by weight) ethanol / diethyl ether mixed solvent is added to dissolve the sample. One to three drops of phenolphthalein ethanol solution are then added to the container as an indicator, and the sample is thoroughly stirred until homogeneous. The solution is then titrated with 0.1 N potassium hydroxide-ethanol solution, and the neutralization endpoint is determined when the indicator remains pale red for 30 seconds. The acid value of the acrylic polymer is calculated from the results using the following formula (1): Acid value (mgKOH / g)=[B×f×5.611] / S (1) In the calculation formula (1), B is the amount (ml) of 0.1N potassium hydroxide-ethanol solution used, f is the factor of the 0.1N potassium hydroxide-ethanol solution, and S is the amount (g) of acrylic polymer collected.

[0041] The weight-average molecular weight of the acrylic polymer is preferably 100,000 to 2,000,000, and more preferably 200,000 to 1,500,000. The weight-average molecular weight of the acrylic polymer is the value before crosslinking with a crosslinking agent described below. The weight-average molecular weight is measured by size exclusion chromatography (SEC) and is a value calculated based on polystyrene. The acrylic polymer may be commercially available or may be synthesized by a known method.

[0042] (coloring agent) The pressure-sensitive adhesive sheet of the present invention contains a colorant. The colorant is preferably a black pigment, more preferably at least one selected from metal oxides and carbon black, even more preferably metal oxides, and particularly preferably black metal oxides. By using a black metal oxide as the colorant, the visibility of the pressure-sensitive adhesive sheet can be more effectively improved. Furthermore, by using a black metal oxide as the colorant, for example, when the adherend has a black frame, the sense of unity with the adherend tends to be enhanced. Note that the colorant may contain other colorants in addition to the metal oxide. Examples of other colorants include aniline black, activated carbon, carbon nanotubes, dyes, etc.

[0043] Examples of metal oxides include copper oxide, iron oxide, manganese dioxide, titanium oxide, zinc oxide, zirconium oxide, barium titanate, potassium titanate, iron titanate, copper-chromium oxide, copper-manganese oxide, copper-iron-manganese oxide, copper-chromium-manganese oxide, copper-iron-chromium oxide, titanium black, etc. Among these, the metal oxide is more preferably a black metal oxide in which the metal species is selected from titanium, copper, iron, and manganese, and even more preferably a black metal oxide in which the metal species is selected from copper, iron, and manganese.

[0044] The lower limit of the average primary particle size of the colorant is not particularly limited, but is preferably 0.01 μm or more. The average primary particle size of the metal oxide is preferably less than 5 μm, more preferably 1 μm or less, even more preferably less than 0.5 μm, and particularly preferably less than 0.1 μm. By setting the average primary particle size of the metal oxide within the above range, the visibility of the pressure-sensitive adhesive sheet can be more effectively improved.

[0045] The content of the colorant is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more, relative to 100 parts by mass of the acrylic polymer, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the acrylic polymer.

[0046] The colorant is preferably mixed with the acrylic polymer in a state where it is dispersed in a dispersing resin, such as a polyester resin, a urethane resin, an acrylic resin, or a polyether resin.

[0047] (acid scavenger) The pressure-sensitive adhesive sheet of the present invention preferably further contains an acid scavenger. In this specification, the term "acid scavenger" refers to a compound that forms a crosslinked structure with a carboxy group contained in the pressure-sensitive adhesive sheet. By incorporating an acid scavenger into the pressure-sensitive adhesive sheet, color fading of the resulting pressure-sensitive adhesive sheet can be more effectively suppressed. This allows the color of the pressure-sensitive adhesive sheet to be maintained even in a high-temperature, high-humidity environment.

[0048] Examples of the acid scavenger include compounds having an organic amino group, an oxazoline group, an epoxy group, a carbodiimide group, etc. Among these, the acid scavenger is preferably a compound having at least one selected from an oxazoline group and a carbodiimide group. By adding a compound having at least one selected from an oxazoline group and a carbodiimide group as the acid scavenger, discoloration of the pressure-sensitive adhesive sheet can be more effectively suppressed.

[0049] Examples of compounds having an oxazoline group include 4,5-dihydro-2-(isopropenyl)oxazole-styrene polymer, ethyl / acrylate-2-isopropenyl-4,5-dihydro-1,3-oxazole-methyl / methacrylate polymer, and butyl / acrylate-4,5-dihydro-2-isopropenyl)oxazole-divinylbenzene-styrene polymer. Examples of compounds having a carbodiimide group include bis(2,6-diisopropylphenyl)carbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1,3-diisopropylcarbodiimide, and bis(2,6-diisopropylphenyl)carbodiimide.

[0050] As the compound having an oxazoline group, commercially available products can be used. Examples of commercially available products include Epocross RPS-1005 (manufactured by Nippon Shokubai Co., Ltd.), Epocross K-2000 series (manufactured by Nippon Shokubai Co., Ltd.), Epocross WK series (manufactured by Nippon Shokubai Co., Ltd.), and 4,5-dihydro-β-methyl-2-oxazoleethanol (manufactured by Kawaguchi Chemical Industry Co., Ltd.). In addition, as the compound having a carbodiimide group, commercially available products can be used. Examples of commercially available products include the cyclic carbodiimide "Carbodista" (manufactured by Teijin Limited), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (manufactured by Kawaguchi Chemical Industry Co., Ltd., EDC), and Carbodilite V-03 (manufactured by Nisshinbo Chemical Inc.).

[0051] The content of the acid scavenger is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the acrylic polymer, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of the acrylic polymer.

[0052] (Crosslinking agent) The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet of the present invention may contain a crosslinking agent. The crosslinking agent can be appropriately selected taking into account its reactivity with the crosslinkable functional groups of the acrylic polymer. For example, the crosslinking agent can be selected from known crosslinking agents such as isocyanate compounds, aziridine compounds, epoxy compounds, metal chelate compounds, and butylated melamine compounds. While oxazoline compounds are exemplified as the acid scavenger mentioned above, oxazoline compounds may also be used as crosslinkers when the acrylic polymer has carboxy groups. However, if the acrylic polymer does not have carboxy groups, the oxazoline compound does not function as a crosslinker. In other words, if the acrylic polymer does not have carboxy groups, the oxazoline compound functions as an acid scavenger rather than a crosslinker. Similarly, carbodiimide compounds may also be used as crosslinkers when the acrylic polymer has carboxy groups, but if the acrylic polymer does not have carboxy groups, they do not function as crosslinkers. Therefore, the crosslinking agent must be selected taking into account its reactivity with the crosslinkable functional groups of the acrylic polymer.

[0053] As the crosslinking agent, an isocyanate compound is preferably used because it can easily crosslink the hydroxyl group-containing (meth)acrylate, and more preferably the crosslinking agent is a bifunctional or higher functional isocyanate compound.

[0054] Examples of isocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, etc. Examples of commercially available products include a tolylene diisocyanate compound (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) and a xylylene diisocyanate compound (manufactured by Mitsui Chemicals, Inc., Takenate D-110N). Examples of epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. Examples of commercially available products include 1,3-bis(N,N-diglycidylaminomethyl)benzene (Mitsubishi Gas Chemical Company, Inc., TETRAD-X) and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (Mitsubishi Gas Chemical Company, Inc., TETRAD-C).

[0055] The content of the crosslinking agent in the pressure-sensitive adhesive composition is appropriately selected depending on the desired adhesiveness, etc., but is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the acrylic polymer. By setting the content of the crosslinking agent within the above range, processability can be further improved. Note that the crosslinking agent may be used alone or in combination with two or more types, and when two or more types are used in combination, it is preferable that the total mass is within the above range.

[0056] (ultraviolet absorber) The pressure-sensitive adhesive sheet of the present invention may contain an ultraviolet absorber. The ultraviolet absorber can be selected from those having a maximum absorption wavelength in the ultraviolet region. In the present invention, an ultraviolet absorber having a maximum absorption wavelength of 350 nm or more may be used. Examples of ultraviolet absorbers having a maximum absorption wavelength of 350 nm or more include compounds represented by the following general formula (1) or (2).

[0057] [ka]

[0058] In the above equation, R 1 represents a hydrogen atom, a halogen atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group, or a cyano group; R 2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 3 represents an alkyl group structure.

[0059] [ka]

[0060] In the above equation, R 4 , R 5 and R 6 is a hydrogen atom, a hydroxyl group, an alkyl group, or a halogen atom, and R 4 , R 5 and R 6 The alkyl group structure is a concept that includes substituents mainly composed of alkyl groups, such as substituted or unsubstituted alkyl groups and substituted or unsubstituted alkoxy groups.

[0061] Among these, it is particularly preferable to use an ultraviolet absorber that has improved compatibility by introducing an alkyl group with a large molecular weight into the aromatic ring of the basic skeleton and that is liquid or oily at 23° C. Here, being liquid or oily at 23° C. means that the ultraviolet absorber alone has fluidity even without a diluting solvent.

[0062] Commercially available ultraviolet absorbers can be used, including, for example, a triazine-based ultraviolet absorber (Tinuvin 477) and benzotriazole-based ultraviolet absorbers (Tinuvin 109, Tinuvin 384-2, and Tinuvin PS) manufactured by BASF Japan Ltd.

[0063] The content of the ultraviolet absorber is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, relative to 100 parts by mass of the acrylic polymer. The content of the ultraviolet absorber in the present invention is preferably adjusted to an amount such that the ultraviolet transmittance at a wavelength of 380 nm is less than 10%. In other words, the ultraviolet transmittance at a wavelength of 380 nm of the pressure-sensitive adhesive sheet of the present invention is preferably less than 10%. The above ultraviolet absorbers may be used alone or in combination of two or more types, and when two or more types are used in combination, the total mass preferably falls within the above range.

[0064] (solvent) The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet of the present invention may contain a solvent. In this case, the solvent is used to improve the coatability of the pressure-sensitive adhesive composition. Examples of solvents include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; and polyols and derivatives thereof such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate.

[0065] The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 25 to 500 parts by mass, more preferably 30 to 400 parts by mass, per 100 parts by mass of the acrylic polymer. The content of the solvent is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the total mass of the pressure-sensitive adhesive composition. One solvent may be used alone, or two or more solvents may be used in combination. When two or more solvents are used in combination, the total mass preferably falls within the above range.

[0066] (Other ingredients) The PSA sheet may contain other components in addition to those described above, provided that the effects of the present invention are not impaired. Examples of other components include known PSA additives. For example, these components can be selected as needed from among plasticizers, antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, and light stabilizers such as hindered amine compounds. Examples of the plasticizer include vinyl carboxylate esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, and vinyl benzoate, and styrene. Examples of antioxidants include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, etc. These antioxidants may be used alone or in combination of two or more. As a metal corrosion inhibitor, benzoriazole resins can be mentioned as a preferred example because of their compatibility with the pressure-sensitive adhesive and their high effectiveness. Examples of tackifiers include rosin-based resins, terpene-based resins, terpene-phenol-based resins, coumarone-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, and petroleum resins. Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers).

[0067] (Method of manufacturing pressure-sensitive adhesive sheet) The method for producing a pressure-sensitive adhesive sheet of the present invention preferably includes a step of applying a pressure-sensitive adhesive composition onto a release sheet to form a coating film.

[0068] The PSA composition can be applied using a known coating device, such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, microgravure coater, rod blade coater, lip coater, die coater, or curtain coater.

[0069] The method for producing a pressure-sensitive adhesive sheet preferably includes a step of heating the coating film. In this case, a known heating device such as a heating furnace or an infrared lamp can be used to heat the coating film formed by coating the pressure-sensitive adhesive composition. After the application of the adhesive sheet and the solvent is removed, the adhesive sheet may be subjected to an aging treatment in which the adhesive sheet is left standing at a certain temperature for a certain period of time, for example, at 23°C for 7 days.

[0070] (Applications of adhesive sheets) The pressure-sensitive adhesive sheet of the present invention is used for bonding transparent members. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used for bonding optical members. Examples of optical members include components of optical products such as touch panels and image display devices, and shatterproof films bonded to the outermost cover lens. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used for bonding to touch panels. Examples of components of touch panels include ITO films in which an ITO film is provided on a transparent resin film, ITO glass in which an ITO film is provided on the surface of a glass plate, transparent conductive films in which a transparent resin film is coated with a conductive polymer, hard coat films, and fingerprint-resistant films. Examples of components of image display devices include antireflection films, alignment films, polarizing films, retardation films, and brightness-enhancing films used in liquid crystal display devices. Materials used for these components include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, cellulose acylate, etc., and the pressure-sensitive adhesive sheet of the present invention is particularly preferably used for bonding to glass.

[0071] The present invention may also relate to a laminate obtained by laminating the above-mentioned pressure-sensitive adhesive sheet and the above-mentioned transparent member. Manufacturing the laminate includes a step of laminating the pressure-sensitive adhesive sheet to the transparent member. In the laminating step, the pressure-sensitive adhesive sheet is preferably laminated to the transparent member using a hand roller or the like. Furthermore, to enhance the adhesion between the pressure-sensitive adhesive sheet and the transparent member, autoclave treatment may be performed under conditions of 20 to 100°C and 1 to 10 atmospheres, for example.

[0072] (Laminate) The present invention also relates to a laminate having a surface layer on one side of the above-mentioned pressure-sensitive adhesive sheet for bonding a transparent member and an indicator on the other side. That is, the laminate has the surface layer, the pressure-sensitive adhesive sheet for bonding a transparent member, and the indicator, in this order. In the laminate, other layers may be provided between the surface layer and the pressure-sensitive adhesive sheet for bonding a transparent member, or between the pressure-sensitive adhesive sheet for bonding a transparent member and the indicator. In one embodiment, the surface layer, the pressure-sensitive adhesive sheet for bonding a transparent member, and the indicator are directly laminated in this order, with no other layers provided between the respective components.

[0073] The surface layer is a layer provided on the outermost surface of the laminate, and for example, when the laminate is incorporated into a display etc., the surface layer is a layer provided on the outermost surface on the visible side. The surface layer may be a surface protective film or a decorative film.

[0074] The surface layer is preferably a glass layer or a resin layer. Examples of the glass layer include, but are not limited to, chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass. Examples of the resin layer include, but are not limited to, an acrylic plate or a polycarbonate plate made of polymethyl methacrylate. Of these, it is more preferable that the surface layer be a glass layer.

[0075] The surface layer may have a step on at least one surface. For example, the surface layer may have a frame-shaped step on the side where the pressure-sensitive adhesive sheet is attached. In this case, the thickness of the step may be 1 to 50 μm, 5 to 40 μm, or 10 to 30 μm. The thickness of the step is preferably 50% or less of the thickness of the pressure-sensitive adhesive sheet, more preferably 40% or less, and even more preferably 30% or less. By satisfying the above conditions for the step provided on the surface layer, it is possible to prevent lifting or the generation of bubbles at the step between the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive sheet and the surface layer, and the laminate can exhibit excellent design properties.

[0076] A functional layer such as a hard coat layer, an anti-reflection layer, or an anti-glare layer may be provided on one or both sides of the surface layer.

[0077] Examples of the display include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper. [Example]

[0078] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0079] <Synthesis of Acrylic Polymer A> Acrylic polymer A was prepared by solution polymerization in ethyl acetate. Butyl acrylate (BA) and 2-hydroxyethyl acrylate (2HEA) were mixed in a mass ratio of 70:30 in ethyl acetate, and AIBN (azobisisobutyronitrile) was dissolved in the solution as a radical polymerization initiator. The solution was heated to 60°C to allow random copolymerization, yielding acrylic polymer A. The solution viscosity of a 35% by mass solution of this acrylic polymer A at 23°C was 6,400 mPa·s. The acid value of acrylic polymer A was 0.2 mgKOH / g.

[0080] <Synthesis of Acrylic Polymer B> Butyl acrylate (BA), methyl acrylate (MA), lauryl acrylate (LA), and 2-hydroxyethyl acrylate (2HEA) were mixed in a mass ratio of 35:30:10:25 in ethyl acetate, and azobisisobutyronitrile (AIBN) was dissolved in the solution as a radical polymerization initiator. The solution was heated to 60°C to allow random copolymerization, yielding acrylic polymer B. The solution viscosity of a 45% by mass solution of this acrylic polymer B at 23°C was 5,600 mPa·s. The acid value of acrylic polymer B was 0.3 mgKOH / g.

[0081] Example 1 Acrylic polymer A, an ethyl acetate solution of a tolylene diisocyanate adduct of trimethylolpropane (Coronate L-55E, manufactured by Tosoh Corporation), a copper, iron, manganese oxide pigment (TM Black 3550, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), an acid scavenger (bis(2,6-diisopropylphenyl)carbodiimide), and ethyl acetate as a solvent were mixed to obtain a pressure-sensitive adhesive composition having a solids concentration of 30% by mass, containing 0.5 parts by mass of crosslinker, 0.03 parts by mass of metal oxide, and 5 parts by mass of acid scavenger relative to 100 parts by mass of acrylic polymer A.

[0082] The pressure-sensitive adhesive composition was coated onto a first release sheet (heavy separator film, Teijin DuPont Films Co., Ltd., release-treated polyethylene terephthalate film). Coating was performed using a doctor blade YD model, manufactured by Yoshimitsu Seiki Co., Ltd., so that the thickness after drying would be 250 μm. The composition was then dried in a hot air dryer at 100° C. for 3 minutes to remove the solvent, forming a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer. A second release sheet (lightweight separator film, manufactured by Teijin DuPont Films Co., Ltd.) having a release treatment that provides better releasability than the first release sheet was attached to one side of this adhesive sheet, thereby obtaining the adhesive sheet of Example 1, which is an adhesive sheet with a release sheet.

[0083] Example 2 Acrylic polymer B, an ethyl acetate solution of a xylylene diisocyanate compound (Mitsui Chemicals, Takenate D-110N), a copper, iron, manganese oxide pigment (Dainichiseika Color & Chemicals Mfg. Co., Ltd., TM Black 3550), an acid scavenger (bis(2,6-diisopropylphenyl)carbodiimide), and ethyl acetate as a solvent were mixed to obtain a pressure-sensitive adhesive composition containing 0.3 parts by mass of crosslinker, 0.03 parts by mass of metal oxide, and 5 parts by mass of acid scavenger, relative to 100 parts by mass of acrylic polymer B, with a solids concentration of 40% by mass. Using this pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1.

[0084] Example 3 An adhesive composition and an adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that the acid scavenger was changed to 5 parts by mass of oxazoline (manufactured by Nippon Shokubai Co., Ltd., Epocross RPS-1005), the metal oxide was changed to 0.15 parts by mass, and the thickness of the adhesive sheet was changed to 100 μm.

[0085] Example 4 An adhesive composition and an adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that the content of metal oxide was changed to 0.23 parts by mass relative to 100 parts by mass of acrylic polymer A and the thickness of the adhesive sheet was changed to 150 μm.

[0086] Example 5 An adhesive composition and an adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that the metal oxide was changed to 0.25 parts by mass of titanium oxide pigment (Mikoku Pigment Co., Ltd., MHI Black #PD-367M) and the thickness of the adhesive sheet was changed to 200 μm.

[0087] Example 6 The metal oxide was changed to a carbon black pigment (Multilac A 903 Black, manufactured by Toyocolor Co., Ltd.), and the amount of pigment was changed so that the content was 0.80 parts by mass. Furthermore, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 2, except that the thickness of the pressure-sensitive adhesive sheet was changed to 50 μm.

[0088] (Comparative Example 1) A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that no acid scavenger was added.

[0089] (Comparative Example 2) A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 2, except that no acid scavenger was added.

[0090] (Comparative Example 3) A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 3, except that no acid scavenger was added.

[0091] Comparative Example 4 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 4, except that no acid scavenger was added.

[0092] (Comparative Example 5) Furthermore, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Comparative Example 3, except that no metal oxide was added.

[0093] (Measurement and Evaluation) <Total light transmittance> The adhesive film was cut into a size of 50 mm in width and 50 mm in length. The lightly peeling separator, which is the second peeling sheet, was peeled off and laminated onto a slide glass (manufactured by Matsunami Glass Industries Co., Ltd., S9112) using a hand roller. Then, the first peeling sheet was peeled off, and the exposed adhesive surface was attached to another slide glass using a laminator. In this state, it was kept in an autoclave under the conditions of 40 °C and 5 atm for 30 minutes to adhere it to the glass plate. Regarding the obtained laminate, in accordance with JIS K 7150, the total light transmittance was measured using an integrating sphere type light transmittance measuring device (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-5000). This measurement was performed three times in the central region of the sample, and the average value was taken as the total light transmittance of the adhesive sheet.

[0094] <Change amount of total light transmittance> Samples prepared in the same manner as the measurement of <Total light transmittance> were placed in an environment of 85 °C and 85% relative humidity, and the total light transmittance after 500 hours was measured. Based on the total light transmittance of the sample before being placed in the environment of 85 °C and 85% relative humidity, the change amount was calculated using the following formula and evaluated according to the following evaluation criteria. Change amount (%) = (Total light transmittance of the sample after treatment rear )-(Total light transmittance of the sample before treatment before

[0095] <Color fastness> Regarding the samples prepared in the same manner as the measurement of <Total light transmittance>, in accordance with JIS Z8781-4, the L* value in the L*a*b* color space was measured using a color measuring device (manufactured by Suga Test Instruments Co., Ltd., Colour Cute i). This measurement was performed three times in the central region of the sample, and the average value was taken as the L* value of the adhesive sheet. <Change amount of L*> Samples prepared in the same manner as the measurement of <Total light transmittance> were placed in an environment of 85 °C and 85% relative humidity, and the L* value after 500 hours was measured. Based on the L* value of the sample before being placed in the environment of 85 °C and 85% relative humidity, the change amount was calculated using the following formula and evaluated according to the following evaluation criteria. Change amount = (L* value of the sample after treatment rear )-(L* value of the sample before treatment before ​(L* value of sample) A: The change in L* value is less than 1.0 and the total light transmittance after treatment is less than 85%. B: The change in L* value is 1.0 or more and less than 2.0, and the total light transmittance after treatment is less than 85% C: The change in total light transmittance is 2.0 or more, or the total light transmittance after treatment is 85% or more

[0096] <Design> A sample was prepared in the same manner as in the measurement of <total light transmittance>, and was placed on a liquid crystal display showing a black screen and visually evaluated. A: It looked darker than when there was nothing on it. B: No change

[0097] <Sense of unity> A UV-curable black ink was screen-printed onto the surface of a glass plate (120 mm long x 70 mm wide x 0.7 mm thick) in a frame shape (inner edge size: 90 mm long x 50 mm wide x 5 mm deep) so that the coating thickness was 5 μm, resulting in a printed stepped glass plate with a 5 μm step. Next, the first release sheet was peeled off from the adhesive sheet with release sheet cut to 90 mm length x 54 mm width, and the sheet was laminated to a PET film (Cosmoshine A4300#100, manufactured by Toyobo Co., Ltd.) using a hand roller to produce a laminated film. This laminated film was cut to 95 mm length x 55 mm width, the second release sheet was peeled off, and the exposed adhesive surface was laminated to a glass plate (surface layer) with a printed step. At this time, the adhesive sheet was laminated using a hand roller so that it covered the entire printed area on the frame. In this state, the sheet was kept in an autoclave at 40°C and 5 atmospheres for 30 minutes to ensure close contact. In this state, the sheet was placed on a liquid crystal display displaying a black screen with the glass surface facing up and the adhesive sheet surface facing down, and visual evaluation was performed. A: The black screen and the surrounding black print (frame-like black print) appear to be one. B: The boundary between the black screen and the surrounding black print (frame-like black print) is faintly visible C: The boundary between the black screen and the surrounding black print (frame-like black print) is clearly visible.

[0098] [Table 1]

[0099] The pressure-sensitive adhesive sheets obtained in the examples were excellent in colorfastness and designability.

[0100] <Preparation of laminate> Two polarizing plates with adhesive layers (Polatechno Corporation, SKN-18243T-HC) were bonded together via one of the adhesive layers so that the polarization axes were in a crossed Nicol state (polarization axes: ∠45°, ∠135°), producing a first laminate consisting of polarizing plate / adhesive layer / polarizing plate / adhesive layer / separator. Next, the separator of the first laminate was peeled off, and a first glass plate (120 mm long x 70 mm wide x 0.7 mm thick) was bonded to the exposed adhesive layer, producing a second laminate consisting of polarizing plate / adhesive layer / polarizing plate / adhesive layer / first glass plate. Note that because the two polarizing plates were arranged in a crossed Nicol state, they were in an extinction state. Next, the pressure-sensitive adhesive sheet obtained in the above-mentioned Example was cut to a length of 90 mm x width of 54 mm, the first release sheet was peeled off, and the sheet was attached to the polarizing plate side (surface polarizing plate side) of the second laminate using a hand roller to produce a third laminate (separator / pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) obtained in the Example / polarizing plate / pressure-sensitive adhesive layer / polarizing plate / pressure-sensitive adhesive layer / first glass plate). Next, the heavy release sheet was peeled off, and the exposed adhesive surface was attached to a glass plate (surface layer) having a printed step produced by the method described below. At this time, the adhesive sheet was attached using a hand roller so that the adhesive sheet covered the entire printed area on the frame. In this state, the sheet was held in an autoclave at 40°C and 5 atmospheres for 30 minutes to ensure close contact. In this way, a laminate (glass plate having a printed step / pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) obtained in the Example / polarizing plate / pressure-sensitive adhesive layer / polarizing plate / pressure-sensitive adhesive layer / first glass plate) having a surface layer, a pressure-sensitive adhesive sheet for attaching a transparent member, and a display body in this order was obtained. The glass plate (surface layer) with a printed step was obtained by screen printing ultraviolet-curable black ink onto the surface of a glass plate (120 mm long x 70 mm wide x 0.7 mm thick) in the shape of a frame (inner edge size: 90 mm long x 50 mm wide x 5 mm deep) so that the applied thickness was 5 μm, forming a step of 5 μm. The pressure-sensitive adhesive sheets obtained in the examples had excellent unity even when formed into the above-mentioned laminates. [Explanation of symbols]

[0101] 1 adhesive sheet with release sheet 11 Adhesive sheet 12a Peel-off sheet 12b Release sheet

Claims

1. A pressure-sensitive adhesive sheet for attaching a transparent member, comprising an acrylic polymer, a colorant, and an acid scavenger, the acid scavenger is a compound having at least one selected from an oxazoline group and a carbodiimide group, the content of carboxy group-containing monomer units in the acrylic polymer is 0.1% by mass or less, An adhesive sheet for attaching transparent members, wherein when the adhesive sheet for attaching transparent members is sandwiched between two glass plates and stored in an environment of 85°C and 85% relative humidity for 500 hours, the change in total light transmittance calculated by the following formula is less than 2%. Change (%)=(Total light transmittance of laminate after treatment at 85°C and 85% relative humidity)−(Total light transmittance of laminate before treatment at 85°C and 85% relative humidity)

2. 2. The pressure-sensitive adhesive sheet for attaching transparent members according to claim 1, wherein the colorant is a black metal oxide.

3. The pressure-sensitive adhesive sheet for attaching a transparent member according to claim 1 or 2, which has a total light transmittance of 30% or more and less than 85%.

4. The pressure-sensitive adhesive sheet for attaching a transparent member according to any one of claims 1 to 3, wherein the colorant has an average primary particle size of 0.01 µm or more and less than 5 µm.

5. A laminate having a surface layer on one side of the pressure-sensitive adhesive sheet for applying to a transparent member according to any one of claims 1 to 4, and an indicator on the other side.

6. The laminate according to claim 5 , wherein the surface layer is a glass layer or a resin layer.

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