Pressure-sensitive adhesive sheet and optical laminate

Abstract

To provide: a pressure-sensitive adhesive sheet which is suitably used for producing an optical laminate having a polarizing plate whose discoloration is suppressed even when left standing in a high temperature environment; and the optical laminate containing an image display cell, the polarizing plate, and a front transparent plate, in which the polarizing plate is stuck to the front transparent plate via a pressure-sensitive adhesive layer and the front transparent plate has low water vapor permeability such as a glass plate.SOLUTION: An adhesive sheet has an adhesive layer consisting of an active energy ray-curable adhesive. Water vapor permeability of a cured adhesive layer which is formed by curing the adhesive layer with thickness of 200 μm by irradiation with an active energy ray measured in accordance with JIS Z0208 in a condition of 40°C, 90%RH is 160 g / (m2.24h.200 μm) or higher. An optical laminate uses the adhesive sheet.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet that is suitable for use in producing an optical laminate in which discoloration of a polarizing plate is suppressed even when placed in a high-temperature environment, and to an optical laminate. [Background technology]

[0002] Liquid crystal display devices and organic EL display devices are widely used as various optical laminates in personal computer monitors, televisions, mobile phones, car navigation devices, etc. In addition, image display panels are provided with a front transparent plate such as a glass plate on the viewing side of the image display panel for the purpose of preventing damage to the image display panel due to impact from the outer surface, etc.

[0003] One method for arranging a front transparent plate on an image display panel is to bond a polarizing plate, which is placed on the outermost surface of the image display panel, to the front transparent plate via an adhesive. In this configuration, the adhesive fills the gap between the image display panel and the front transparent member, reducing the refractive index difference at the interface and suppressing the deterioration of visibility due to reflection and scattering.

[0004] Incidentally, it is known that when an optical laminate in which an image display panel and a front transparent plate are bonded together using a pressure-sensitive adhesive is subjected to a long-term high-temperature durability test required for in-vehicle displays, etc., the transmittance of the polarizing plate constituting the image display panel at the central in-plane portion decreases. The decrease in transmittance of the polarizing plate is caused by polyenization of polyvinyl alcohol constituting the polarizer in a high-temperature environment, and the decrease in transmittance tends to be more pronounced as the panel size increases.

[0005] Therefore, several measures have been proposed to prevent the transmittance of the polarizer from decreasing. For example, Patent Document 1 describes a plastic film sheet with a water vapor permeability of 1 g / m 2 The document describes a method for manufacturing a display device in which a plastic film sheet is fixed to a support having a temperature of 1000 to 1500°C (1 / day) or less in a peelable manner, and the plastic film sheet is provided with the barrier properties required during the manufacturing process of the display device.

[0006] Patent Document 2 proposes an adhesive sheet to be used for bonding a polarizing plate to a transparent member arranged on the viewing side of an optical laminate, in which the base polymer of the adhesive composition constituting the adhesive sheet has a specific thickness, moisture permeability and moisture content and does not substantially contain organic acid monomer components as monomer units.

[0007] Patent Document 3 describes a reinforced polarizing optical film laminate used in an optical display panel attached to the body of a powered vehicle, which includes a polarizing film made of a polyvinyl alcohol-based resin, an optically transparent polarizing film protective film bonded to one or both sides of the polarizing film, either directly or via another optical film, and a transparent optical film having a predetermined strength laminated via an adhesive on the other side opposite to the one side of the polarizing film protective film bonded to one side of the polarizing film, and describes a method for reducing discoloration of the polarizing film by optimizing the iodine concentration and moisture content of the polarizing film. The techniques disclosed in these documents aim to suppress discoloration of the polarizing film by focusing on the iodine concentration and moisture content of the polarizing plate. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-280550 [Patent Document 2] Japanese Patent Application Publication No. 2017-075998 [Patent Document 3] Patent Publication No. 2021-073500 Summary of the Invention [Problem to be solved by the invention]

[0009] The present applicant has previously reported a display comprising one display component, another display component, and a cured adhesive layer that bonds the one display component and the other display component together, wherein at least one of the one display component and the other display component is made of a plastic plate, and the cured adhesive layer has a water vapor permeability of 100 g / (m 2 ·24h ·100μm) or more, 200g / (m 2 JP 2019-035061 A proposes a display body having an adhesive layer with a thickness of 100 μm or less (24h 100 μm).

[0010] The adhesive sheet used in the display described in this document has a relatively high water vapor permeability in the cured adhesive layer, which makes it difficult for moisture to condense in the cured adhesive layer.As a result, when the cured adhesive layer is placed in a high-temperature, high-humidity environment and then returned to room temperature and humidity, whitening of the cured adhesive layer is suppressed and the adhesive layer also has excellent blister resistance.

[0011] However, in the case of a display having a polarizing plate and one of the display component parts (front transparent plate) being a glass plate or the like that is difficult for water vapor to pass through, when this display is subjected to a high temperature environment, there is a problem that, although the problem of blister resistance is unlikely to occur, the problem of discoloration of the polarizing plate (polyenization) is likely to occur.

[0012] Therefore, an object of the present invention is to provide an optical laminate in which one gas shielding member and another gas shielding member are sandwiched via an adhesive layer, and one of the one gas shielding member and the other gas shielding member includes a polarizing plate, and an adhesive sheet that is suitably used for producing an optical laminate in which discoloration of the polarizing plate is suppressed even when placed in a high-temperature environment, and an optical laminate. [Means for solving the problem]

[0013] In order to solve the above problems, the present inventors have conducted extensive research into pressure-sensitive adhesive sheets to be used in optical laminates including an image display cell, a polarizing plate, and a front transparent plate, in which the polarizing plate is bonded to the front transparent plate via a pressure-sensitive adhesive layer. As a result, they have found that when a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive with a high water vapor permeability is used as the pressure-sensitive adhesive sheet to be used for bonding the polarizing plate to the front transparent plate, an optical laminate can be obtained in which discoloration of the polarizing plate is suppressed even when placed in a high-temperature environment, and have completed the present invention.

[0014] Thus, according to the present invention, there are provided optical laminates described in the following [1] to [6]. [1] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of an active energy ray-curable pressure-sensitive adhesive, wherein the pressure-sensitive adhesive layer having a thickness of 200 μm is cured by irradiation with active energy rays, and the cured pressure-sensitive adhesive layer has a water vapor permeability of 160 g / (m) measured in accordance with JIS Z0208 under conditions of 40°C and 90% RH. 2 24h 200μm or more). [2] The pressure-sensitive adhesive sheet according to [1], characterized in that the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer after curing is 20% or more and 95% or less. [3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer further contains a plasticizer.

[0015] [4] [1] or [2], wherein the adhesive constituting the adhesive layer is an acrylic adhesive. The adhesive sheet according to claim 1. [5] The pressure-sensitive adhesive sheet according to [1] or [2], which is sandwiched between one gas-shielding member and another gas-shielding member, and one of the one gas-shielding member and the other gas-shielding member is used in an optical laminate including a polarizing plate. [6] An optical laminate comprising one gas shielding member and another gas shielding member sandwiched via a pressure-sensitive adhesive layer, wherein either one of the one gas shielding member and the other gas shielding member includes a polarizing plate, The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive sheet according to [1] or [2], The one gas shielding member and the other gas shielding member have a water vapor permeability of 0.001 g / (m) as measured in accordance with JIS K7129 under conditions of 40°C and 90% RH. 2 24h) or less) of an optical laminate. [Effects of the Invention]

[0016] According to the present invention, there are provided an adhesive sheet and an optical laminate that are suitably used for producing an optical laminate that is sandwiched between one gas shielding member and another gas shielding member, one of the one gas shielding member and the other gas shielding member including a polarizing plate, and in which discoloration of the polarizing plate is suppressed even when placed in a high-temperature environment. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing the layer structure of an example of the optical laminate of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below, dividing it into 1) a pressure-sensitive adhesive sheet and 2) an optical laminate. 1) Adhesive sheet The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having at least a pressure-sensitive adhesive layer composed of an active energy ray-curable pressure-sensitive adhesive, wherein the pressure-sensitive adhesive layer having a thickness of 200 μm is cured by irradiation with active energy rays, and the cured pressure-sensitive adhesive layer is sandwiched between two Tetron meshes #380, and the water vapor permeability of the cured pressure-sensitive adhesive layer is measured in accordance with JIS Z0208 under conditions of 40°C and 90% RH and is 160 g / (m 2 ·24h·200μm or more).

[0019] (adhesive) The adhesive layer of the adhesive sheet of the present invention is made of an active energy ray-curable adhesive, and it is preferable to use one having the following physical properties. By using an adhesive having the physical properties shown below, an optical laminate can be obtained in which discoloration of the polarizing plate is suppressed when placed in a high-temperature environment, even if a front transparent plate with low water vapor permeability, such as a glass plate, is used.

[0020] (1) Water vapor permeability The pressure-sensitive adhesive used in the optical laminate of the present invention is a cured pressure-sensitive adhesive layer obtained by curing a 200 μm-thick pressure-sensitive adhesive layer formed on one side of a triacetyl cellulose film by irradiation with active energy rays, the cured pressure-sensitive adhesive layer having a water vapor permeability of 160 g / (m) as measured in accordance with JIS Z0208 under conditions of 40°C and 90% RH. 2 24h 200μm) or more, and in particular, 180g / (m 2 24h 200μm) or more, and more preferably 190g / (m 2 The upper limit of the water vapor permeability is not particularly limited, but is usually 2000 g / (m 2 ·24h·200μm) or less, and 1500g / (m 2 24h 200μm) or less, and particularly 1000g / (m 2 ·24h·200μm) or less, and more preferably 800g / (m 2 ·24h·200μm) or less is preferable.

[0021] The pressure-sensitive adhesive of the pressure-sensitive adhesive sheet of the present invention has a water vapor permeability within the above range, allowing the cured pressure-sensitive adhesive layer to exhibit excellent hydrophilicity. Here, at high temperatures, moisture is likely to be generated due to thermal degradation reactions of the resin. Furthermore, when the sheet is sandwiched between gas-shielding members that are impermeable to water vapor, the generated moisture is likely to remain, which, combined with high-temperature conditions, can easily cause discoloration of the polarizing plate (polyenization). As described above, the pressure-sensitive adhesive of the pressure-sensitive adhesive sheet of the present invention exhibits excellent hydrophilicity, thereby making it difficult for moisture to remain and facilitating its escape, thereby reducing the effects of moisture, which is one factor in polyenization. In other words, even when the optical laminate is placed under high-temperature conditions, the cured pressure-sensitive adhesive layer with excellent hydrophilicity suppresses the effects of moisture generated under such high-temperature conditions, which is thought to contribute to the suppression of polyenization. Therefore, condensation of the moisture in the cured pressure-sensitive adhesive layer is also unlikely to occur, and as a result, moisture in the polarizing plate adjacent to the pressure-sensitive adhesive layer is easily expelled from the system, thereby suppressing discoloration of the polarizing plate.

[0022] On the other hand, the water vapor permeability of the adhesive layer after curing is 2000 g / (m 2 If the permeability exceeds 200 μm (24 h x 24 h), if metal components such as electrodes are present on the adhesive layer side after curing, corrosion of the metal components may occur. The water vapor permeability test method is as shown in the test example described below.

[0023] (2) Gel fraction The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention before irradiation with active energy rays is preferably 10 to 80%, more preferably 20 to 75%, particularly preferably 30 to 70%, even more preferably 40 to 65%, and of these, preferably 41 to 60%. In the pressure-sensitive adhesive sheet of the present invention, the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer after curing is preferably 20% or more and 95% or less. This makes it easier to exert the desired cohesive strength, and therefore makes it easier to adjust physical properties such as adhesive strength and storage modulus to appropriate values. From this perspective, the gel fraction is preferably 25 to 88%, more preferably 30 to 82%, particularly preferably 35 to 76%, even more preferably 40 to 70%, and of these, 45 to 67% is preferred. The method for measuring the gel fraction of the pressure-sensitive adhesive layer before and after curing is as shown in the test examples described below.

[0024] (3) Total light transmittance In the pressure-sensitive adhesive sheet of the present invention, the total light transmittance of the pressure-sensitive adhesive layer is preferably 80% or more, more preferably 86% or more, particularly preferably 92% or more, even more preferably 98% or more, and even more preferably 99% or more. The upper limit of the total light transmittance is usually preferably 100% or less. This provides very high transparency and makes the sheet suitable for optical applications (displays). The total light transmittance of the pressure-sensitive adhesive layer is the same as that of the pressure-sensitive adhesive layer after curing by irradiation with active energy rays. The preferred range of the total light transmittance of the pressure-sensitive adhesive layer after curing is the same as that of the pressure-sensitive adhesive layer described above. The total light transmittance in this specification is a value measured in accordance with JIS K7361-1:1997.

[0025] (4) Haze value In the pressure-sensitive adhesive sheet of the present invention, the haze value of the pressure-sensitive adhesive layer is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, even more preferably 0.5% or less, and most preferably 0.2% or less. The lower limit of the haze value is usually preferably 0% or more. This provides very high transparency and makes the sheet suitable for optical applications (displays). The haze value of the pressure-sensitive adhesive layer is the same as that of the pressure-sensitive adhesive layer after curing by irradiation with active energy rays. The preferred range of the haze value of the pressure-sensitive adhesive layer after curing is the same as that of the pressure-sensitive adhesive layer described above. The haze value in this specification is a value measured in accordance with JIS K7136:2000.

[0026] (5) Storage modulus The storage modulus of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention at 23°C before irradiation with active energy rays is preferably 0.001 to 0.5 MPa, particularly preferably 0.005 to 0.3 MPa, further preferably 0.01 to 0.2 MPa, and of these, more preferably 0.03 to 0.1 MPa. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is cured by irradiation with active energy rays to form a cured pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer preferably has a storage modulus at 23°C of 0.01 to 0.5 MPa, more preferably 0.02 to 0.4 MPa, and even more preferably 0.03 to 0.3 MPa. The storage modulus at 23° C. of the pressure-sensitive adhesive layer before and after curing can be measured, for example, by the method described in the Examples. (6) Adhesive strength The adhesive strength of the adhesive layer of the pressure-sensitive adhesive sheet of the present invention to soda-lime glass before irradiation with active energy rays is preferably 1 to 100 N / 25 mm, more preferably 4 to 75 N / 25 mm, particularly preferably 8 to 50 N / 25 mm, and even more preferably 10 to 44 N / 25 mm. This allows the adhesive layer to exhibit sufficient adhesiveness to the adherend. Note that the adhesive strength basically refers to the adhesive strength measured by the 180-degree peel method in accordance with JIS Z0237:2009, and the specific test method is as shown in the test examples described below.

[0027] Furthermore, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is cured by irradiation with active energy rays to form a cured pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer to soda-lime glass is preferably 1 to 100 N / 25 mm, more preferably 4 to 75 N / 25 mm, particularly preferably 8 to 50 N / 25 mm, even more preferably 10 to 44 N / 25 mm, and even more preferably 12 to 38 N / 25 mm. This allows sufficient adhesion to the adherend. Note that the above-mentioned adhesive strength basically refers to the adhesive strength measured by the 180-degree peel method in accordance with JIS Z0237:2009, and the specific test method is as shown in the test examples described below.

[0028] Furthermore, when using the pressure-sensitive adhesive sheet, after bonding a polarizing plate and a front transparent plate using the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is irradiated with active energy rays through the front transparent plate. This cures the active energy ray-curable component (C), and the pressure-sensitive adhesive layer becomes a cured pressure-sensitive adhesive layer. This cured pressure-sensitive adhesive layer has an increased gel fraction and a high cohesive force due to curing, so the resulting laminate (display) has high durability and adhesion even under high temperature conditions, and the occurrence of bubbles, lifting, peeling, etc. between the laminate and the adherend is suppressed.

[0029] (7) Water absorption rate When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is cured by irradiation with active energy rays to form a cured pressure-sensitive adhesive layer, the water absorption rate of the pressure-sensitive adhesive layer is preferably 2% or less, more preferably 1.8% or less, and even more preferably 1.5% or less. The lower limit of the water absorption rate of the pressure-sensitive adhesive layer is 0% or more. The water absorption rate of the cured pressure-sensitive adhesive layer can be measured by the method described in the Examples.

[0030] 2. Adhesive composition The pressure-sensitive adhesive used in the optical laminate of the present invention is not particularly limited as long as it is composed of an active energy ray-curable pressure-sensitive adhesive and the water vapor permeability of the pressure-sensitive adhesive layer after curing, which is obtained by irradiating the pressure-sensitive adhesive layer with active energy rays, falls within the aforementioned ranges.

[0031] In particular, the pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive, and in particular, it preferably has a crosslinked structure composed of a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B) and also contains an active energy ray-curable component (C). Such a pressure-sensitive adhesive layer can be formed, for example, from a pressure-sensitive adhesive obtained by crosslinking (thermally crosslinking) a pressure-sensitive adhesive composition (hereinafter sometimes referred to as "pressure-sensitive adhesive composition P") containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), and an active energy ray-curable component (C). It is preferable that the pressure-sensitive adhesive composition P further contains a photopolymerization initiator (D) as desired. Furthermore, in this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" also includes the concept of "copolymer."

[0032] In addition, from the viewpoint of the SDGs, a material with a high biomass content, a material that can be recycled or reused, or a recycled or reused material may be used as the material constituting the pressure-sensitive adhesive used in the optical laminate of the present invention.

[0033] (2-1) (Meth)acrylic acid ester polymer (A) The (meth)acrylic acid ester polymer (A) is not particularly limited as long as the water vapor permeability of the resulting cured pressure-sensitive adhesive layer falls within the aforementioned range. In the present invention, the (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, a monomer having a reactive functional group in the molecule (reactive functional group-containing monomer). In particular, the (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, the reactive functional group-containing monomer in an amount of 1% by mass or more, more preferably 4% by mass or more, particularly preferably 7% by mass or more, and even more preferably 9% by mass or more. Furthermore, the (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, the reactive functional group-containing monomer in an amount of 60% by mass or less, more preferably 45% by mass or less, particularly preferably 30% by mass or less, and even more preferably 25% by mass or less. This makes it possible to ensure a sufficient content of monomers other than the reactive functional group-containing monomer, resulting in superior adhesiveness of the resulting pressure-sensitive adhesive.

[0034] When the (meth)acrylic acid ester polymer (A) contains the reactive functional group-containing monomer as a constituent monomer unit in the above amount, crosslinking (thermal crosslinking) the pressure-sensitive adhesive composition P results in a reaction between the reactive functional group derived from the reactive functional group-containing monomer in the (meth)acrylic acid ester polymer (A) and the reactive functional group of the crosslinking agent (B), forming a three-dimensional network structure as a crosslinked structure. This results in an increased cohesive strength of the resulting pressure-sensitive adhesive, resulting in excellent blister resistance and durability and adhesiveness under high-temperature conditions. Furthermore, the (meth)acrylic acid ester polymer (A) has a relatively high glass transition temperature (Tg). This results in an appropriate cohesive strength of the pressure-sensitive adhesive constituting the resulting cured pressure-sensitive adhesive layer, resulting in improved blister resistance and superior step-conforming ability under high-temperature and high-humidity conditions. Furthermore, when the reactive functional group is a hydrophilic group, the presence of the hydrophilic group in the above amount in the cured pressure-sensitive adhesive layer provides good compatibility with moisture, even when the cured pressure-sensitive adhesive layer is subjected to high-temperature conditions, allowing moisture to easily move through the cured pressure-sensitive adhesive layer. This is thought to make it easier for moisture to escape from the cured adhesive layer when the temperature and humidity are returned to normal after being placed in a high-temperature, high-humidity environment.As a result, moisture remaining in the polarizing plate adjacent to the adhesive layer also easily escapes through the adhesive layer, suppressing polyenization due to moisture.

[0035] The (meth)acrylic acid ester polymer (A) containing the reactive functional group-containing monomer as a constituent monomer unit in the above amount has good compatibility with the active energy ray-curable component (C), and as a result, the transparency of the resulting pressure-sensitive adhesive layer after curing is also improved.

[0036] Examples of reactive functional group-containing monomers include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), monomers having an amino group in the molecule (amino group-containing monomers), etc. From the viewpoint of easily satisfying the above-mentioned water vapor permeability, the reactive functional group-containing monomer is preferably a hydroxyl group-containing monomer or a carboxyl group-containing monomer, and particularly preferably a hydroxyl group-containing monomer.

[0037] 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 blister resistance, resistance to wet heat whitening, and further, conformability to unevenness and transparency under high-temperature and high-humidity conditions, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or 4-hydroxybutyl acrylate are particularly preferred. These may be used alone or in combination of two or more.

[0038] 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, or may have a cyclic structure.

[0039] From the viewpoint of adhesiveness, the (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 20 carbon atoms. Examples of the (meth)acrylic acid alkyl ester having an alkyl group with 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, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate. These may be used alone or in combination of two or more.

[0040] Of the above, preferred (meth)acrylic acid alkyl esters are those in which the alkyl group has 4 to 20 carbon atoms. Preferred (meth)acrylic acid alkyl esters in which the alkyl group has 4 to 20 carbon atoms include n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isobornyl (meth)acrylate, etc., and particularly preferred are n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isobornyl (meth)acrylate, which are capable of easily achieving the desired water vapor permeability, and among these, n-butyl (meth)acrylate and isobornyl (meth)acrylate are preferred.

[0041] The (meth)acrylic acid ester polymer (A) preferably contains 30 to 99 mass % of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer, more preferably 40 to 95 mass %, particularly preferably 50 to 90 mass %, and even more preferably 60 to 85 mass %. This allows the (meth)acrylic acid ester polymer (A) to exhibit suitable adhesive properties. Also, suitable amounts of other monomer components can be introduced into the (meth)acrylic acid ester polymer (A).

[0042] It is also preferable to use a combination of a (meth)acrylic acid alkyl ester monomer (hard monomer) having a glass transition temperature (Tg) of above 0°C as a homopolymer and a monomer (soft monomer) having a glass transition temperature (Tg) of 0°C or lower as a homopolymer. The soft monomer ensures adhesion and flexibility, while the hard monomer improves cohesion, resulting in improved blister resistance and conformability to uneven surfaces. In this case, the mass ratio of the hard monomer to the soft monomer is preferably 5:95 to 40:60, and particularly preferably 15:85 to 30:70.

[0043] The glass transition temperature (Tg) of the homopolymer of the hard monomer is preferably 40° C. or higher, particularly preferably 60° C. or higher, and more preferably 80° C. or higher. The glass transition temperature (Tg) is preferably 300° C. or lower, particularly preferably 200° C. or lower, and more preferably 130° C. or lower.

[0044] Examples of the hard monomer include methyl acrylate (Tg 10° C.), methyl methacrylate (Tg 105° C.), isobornyl acrylate (Tg 94° C.), isobornyl methacrylate (Tg 180° C.), adamantyl acrylate (Tg 115° C.), adamantyl methacrylate (Tg 141° C.), etc. These may be used alone or in combination of two or more.

[0045] Among the above hard monomers, from the viewpoint of further exerting the performance of the hard monomer while preventing adverse effects on other properties such as adhesion and transparency, methyl acrylate, methyl methacrylate, and isobornyl acrylate are preferred, and isobornyl acrylate is particularly preferred.

[0046] The glass transition temperature (Tg) of the homopolymer of the soft monomer is preferably from -100 to -20°C, particularly preferably from -90 to -30°C, and further preferably from -80 to -50°C.

[0047] Preferred examples of the soft monomer include alkyl acrylates having a linear or branched alkyl group having 2 to 12 carbon atoms. Examples include 2-ethylhexyl acrylate (Tg -70°C) and n-butyl acrylate (Tg -54°C), with 2-ethylhexyl acrylate (Tg -70°C) being particularly preferred from the viewpoint of adhesiveness, and n-butyl acrylate (Tg -54°C) being preferred from the viewpoint of obtaining a relatively hard adhesive. These may be used alone or in combination of two or more.

[0048] It is also preferable that at least a portion of the (meth)acrylic acid alkyl ester is a monomer having an alicyclic structure as the alkyl group (an alicyclic structure-containing monomer). Because the alicyclic structure-containing monomer is bulky, its presence in the polymer is presumed to increase the spacing between polymer molecules, thereby making the resulting pressure-sensitive adhesive excellent in flexibility. This results in the pressure-sensitive adhesive having excellent step-conforming properties.

[0049] The carbon ring of the alicyclic structure in the alicyclic structure-containing monomer may be a saturated structure or may partially contain an unsaturated bond. The alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic or tricyclic structure. From the viewpoint of optimizing the distance between the rings in the resulting (meth)acrylic acid ester polymer (A) and imparting high stress relaxation properties to the adhesive, the alicyclic structure is preferably a polycyclic alicyclic structure (a polycyclic structure). Furthermore, in consideration of the compatibility of the (meth)acrylic acid ester polymer (A) with other components, the polycyclic structure is particularly preferably a bicyclic to tetracyclic structure. Similarly, from the viewpoint of imparting stress relaxation properties, the number of carbon atoms in the alicyclic structure (meaning the total number of carbon atoms in the ring, or the total number of carbon atoms in the case of multiple independent rings) is preferably 5 or more, and particularly preferably 7 or more. On the other hand, there is no particular upper limit on the number of carbon atoms in the alicyclic structure, but from the viewpoint of compatibility as described above, it is preferably 15 or less, and particularly preferably 10 or less.

[0050] Specific examples of the alicyclic structure-containing monomer include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. Among these, dicyclopentanyl (meth)acrylate (alicyclic structure carbon number: 10), adamantyl (meth)acrylate (alicyclic structure carbon number: 10), or isobornyl (meth)acrylate (alicyclic structure carbon number: 7) are preferred, as they exhibit better blister resistance and better conformability to unevenness under high-temperature and high-humidity conditions, and isobornyl (meth)acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0051] When the (meth)acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a constituent monomer unit, the proportion of the alicyclic structure-containing monomer in the (meth)acrylic acid alkyl ester having an alkyl group of 1 to 20 carbon atoms is preferably 1 to 30 mass%, particularly preferably 4 to 24 mass%, and even more preferably 8 to 18 mass%, which provides the resulting pressure-sensitive adhesive with better step-conforming ability and sufficient excellent adhesive strength to transparent conductive films and plastics.

[0052] The (meth)acrylic acid ester polymer (A) may contain, as a monomer unit constituting the polymer, a reactive functional group-containing monomer other than the above-mentioned hydroxyl group-containing monomer.

[0053] Such reactive functional group-containing monomers include carboxyl group-containing monomers and amine group-containing monomers. Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, etc. These may be used alone or in combination of two or more.

[0054] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, monoethylaminopropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0055] On the other hand, it is also preferable that the (meth)acrylic acid ester polymer (A) does not contain a carboxy group-containing monomer as a monomer unit constituting the polymer. Since a carboxy group is an acid component, by not containing a carboxy group-containing monomer, even if the target to which the pressure-sensitive adhesive is applied contains a material that is susceptible to problems caused by acid, such as a transparent conductive film or a metal film such as tin-doped indium oxide (ITO), the problems caused by acid (corrosion, resistance change, etc.) can be suppressed.

[0056] Here, "free of carboxyl group-containing monomers" means that the carboxyl group-containing monomers are substantially not contained, and in addition to not containing any carboxyl group-containing monomers at all, the carboxyl group-containing monomers may be contained to an extent that the carboxyl groups do not cause corrosion of the transparent conductive film, metal wiring, etc. Specifically, the carboxyl group-containing monomers may be contained in the (meth)acrylic acid ester polymer (A) in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less, as monomer units.

[0057] Furthermore, the (meth)acrylic acid ester polymer (A) preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. The presence of the nitrogen atom-containing monomer as a constituent unit in the polymer imparts a predetermined polarity to the pressure-sensitive adhesive, making it possible to provide excellent affinity for adherends having a certain degree of polarity, such as glass. Examples of the nitrogen atom-containing monomer include the amino group-containing monomers described above as reactive functional group-containing monomers, as well as monomers having an amide group and monomers having a nitrogen-containing heterocycle. Among these, monomers having a nitrogen-containing heterocycle are preferred from the viewpoint of providing the (meth)acrylic acid ester polymer (A) with appropriate rigidity.

[0058] Examples of monomers having a nitrogen-containing heterocycle include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide. Among these, N-(meth)acryloylmorpholine, which exhibits superior adhesive strength, is preferred, and N-acryloylmorpholine is particularly preferred.

[0059] In addition, examples of nitrogen atom-containing monomers that can be used include N-vinylcarboxylic acid amide, (meth)acrylamide, N-methyl(meth)acrylamide, N-methylol(meth)acrylamide, N-tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-ethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-phenyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, and N-vinylcaprolactam. The above nitrogen atom-containing monomers may be used alone or in combination of two or more.

[0060] When the (meth)acrylic acid ester polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the nitrogen atom-containing monomer is preferably contained in an amount of 1 to 20 mass %, more preferably 4 to 16 mass %, and even more preferably 7 to 12 mass %, which allows the resulting pressure-sensitive adhesive to effectively exhibit excellent adhesiveness to adherends such as glass.

[0061] The (meth)acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired. Examples of other monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

[0062] The (meth)acrylic acid ester polymer (A) is preferably a linear polymer, which facilitates entanglement of molecular chains and is expected to improve cohesive strength, thereby providing a pressure-sensitive adhesive with superior desired adhesiveness.

[0063] The (meth)acrylic acid ester polymer (A) is preferably a solution polymer obtained by solution polymerization, which makes it easier to obtain a high molecular weight polymer and is expected to have improved cohesive strength, resulting in a pressure-sensitive adhesive with superior desired adhesiveness.

[0064] The polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

[0065] The lower limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 200,000 to 3,000,000, more preferably 300,000 to 2,200,000, particularly preferably 400,000 to 1,400,000, and even more preferably 450,000 to 800,000. This not only improves the adhesiveness of the resulting pressure-sensitive adhesive, but also makes it easier to satisfy the physical properties such as the water vapor transmission rate described above. Note that the weight average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0066] 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.

[0067] The content of the (meth)acrylic acid ester polymer (A) in the pressure-sensitive adhesive composition P is preferably 50 to 99.99 mass%, particularly preferably 60 to 99.9 mass%, and even more preferably 70 to 99 mass%. This ensures that the resulting pressure-sensitive adhesive effectively exhibits suitable adhesiveness and easily meets the water vapor permeability requirement. Furthermore, the contents of other components, such as the crosslinking agent (B) and the active energy ray-curable component (C), are ensured, and the resulting pressure-sensitive adhesive effectively exhibits suitable cohesive strength.

[0068] (2-2) Crosslinking agent (B) The crosslinking agent (B) plays a role in crosslinking the (meth)acrylic acid ester polymer (A) and forming a good three-dimensional network structure when the pressure-sensitive adhesive composition P is heated, thereby further improving the cohesive strength of the resulting pressure-sensitive adhesive and providing it with better blister resistance and step-conforming ability under high-temperature, high-humidity conditions.

[0069] The crosslinking agent (B) may be any agent that reacts with the reactive functional groups of the (meth)acrylic acid ester polymer (A), such as 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. As mentioned above, the (meth)acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer as a constituent monomer unit, and therefore, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with hydroxyl groups as the crosslinking agent (B). The crosslinking agent (B) may be used alone or in combination of two or more.

[0070] 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.

[0071] The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition P is preferably 0.01 to 10 parts by mass, more preferably 0.04 to 5 parts by mass, particularly preferably 0.08 to 1 part by mass, and even more preferably 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). This ensures an appropriate degree of crosslinking, making it easier for the resulting pressure-sensitive adhesive to satisfy the desired adhesive properties and physical properties such as the water vapor permeability described above.

[0072] (2-3) Active energy ray-curable component (C) The adhesive composition P preferably contains an active energy ray-curable component (C). This allows the adhesive obtained by crosslinking (thermal crosslinking) the adhesive composition P to become an active energy ray-curable adhesive. It is presumed that, upon curing by irradiation with active energy rays after application to an adherend, 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 high-order structure exhibits high cohesive strength and high film strength, resulting in excellent blister resistance and step conformability under high-temperature, high-humidity conditions.

[0073] 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, an oligomer, a polymer, or a mixture thereof. Among them, preferred is a polyfunctional acrylate monomer that has excellent compatibility with the (meth)acrylic acid ester polymer (A) and the like.

[0074] Examples of polyfunctional acrylate monomers include bifunctional monomers such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; trifunctional types such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional types such as propionic acid-modified dipentaerythritol tri(meth)acrylate; pentaerythritol tri(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate; and hexafunctional types such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. Among the above, from the viewpoint of the blister resistance and step-following ability of the resulting pressure-sensitive adhesive under high-temperature, high-humidity conditions, polyfunctional acrylate monomers containing an isocyanurate structure in the molecule, such as di(acryloxyethyl)isocyanurate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate, are preferred, polyfunctional acrylate monomers that are trifunctional or higher and contain an isocyanurate structure in the molecule are more preferred, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate is particularly preferred. These may be used alone or in combination of two or more. From the viewpoint of compatibility with the (meth)acrylic acid ester polymer (A), the polyfunctional acrylate monomer preferably has a molecular weight of less than 1,000.

[0075] The active energy ray-curable component (C) may also be an active energy ray-curable acrylate oligomer, such as a polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, or silicone acrylate.

[0076] The mass average molecular weight of the acrylate oligomer is preferably 50,000 or less, particularly preferably 1,000 to 50,000, and further preferably 3,000 to 40,000. These acrylate oligomers may be used alone or in combination of two or more.

[0077] The active energy ray-curable component (C) may also be an adduct acrylate polymer having a (meth)acryloyl group introduced into its side chain. Such an adduct acrylate polymer can be obtained by using a copolymer of a (meth)acrylic acid ester and a monomer having a crosslinkable functional group in the molecule, and reacting a compound having a group reactive with the (meth)acryloyl group and the crosslinkable functional group with a portion of the crosslinkable functional group of the copolymer.

[0078] The mass average molecular weight of the adduct acrylate polymer is preferably about 50,000 to 900,000, and particularly preferably about 100,000 to 500,000.

[0079] The active energy ray-curable component (C) can be one selected from the above-mentioned polyfunctional acrylate monomers, acrylate oligomers, and adduct acrylate polymers, or two or more selected from them can be used in combination, or can be used in combination with other active energy ray-curable components.

[0080] The content of the active energy ray-curable component (C) in the adhesive composition P is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, particularly preferably 4 to 30 parts by mass, even more preferably 5 to 20 parts by mass, and especially preferably 6 to 12 parts by mass, per 100 parts by mass of the (meth)acrylic acid ester polymer (A), from the viewpoints of improving the cohesive strength of the resulting adhesive and achieving excellent blister resistance and conformability to unevenness under high-temperature and high-humidity conditions.

[0081] (2-4) Photopolymerization initiator (D) When ultraviolet rays are used as the active energy rays to cure the active energy ray-curable pressure-sensitive adhesive, it is preferable that the pressure-sensitive adhesive composition P further contains a photopolymerization initiator (D), which allows the active energy ray-curable component (C) to be polymerized efficiently and reduces the polymerization and curing time and the exposure dose of the active energy rays.

[0082] Examples of such photopolymerization initiators (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzof Examples of suitable benzoxanthone include phenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, etc. These may be used alone or in combination of two or more.

[0083] The content of the photopolymerization initiator (D) in the pressure-sensitive adhesive composition P is preferably at least 0.1 parts by mass, particularly preferably at least 1 part by mass, relative to 100 parts by mass of the active energy ray-curable component (C), and is preferably at most 30 parts by mass, particularly preferably at most 15 parts by mass.

[0084] (2-5) Various additives If desired, various additives commonly used in acrylic pressure-sensitive adhesives, such as plasticizers, surfactants, silane coupling agents, ultraviolet absorbers, infrared absorbers, oxygen absorbers, rust inhibitors, colorants, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index adjusters, etc., can be added to the pressure-sensitive adhesive composition P. The polymerization solvents and dilution solvents described below are not included in the additives constituting the pressure-sensitive adhesive composition P.

[0085] The inclusion of a plasticizer in the pressure-sensitive adhesive layer is preferable because it can increase the water vapor permeability described above. This is presumably because the plasticizer penetrates into the three-dimensional network structure of the pressure-sensitive adhesive layer, providing an escape route for water vapor in the pressure-sensitive adhesive.

[0086] Examples of plasticizers in the pressure-sensitive adhesive sheet of the present invention include carboxylic acid ester-based plasticizers, phthalate ester-based plasticizers, phosphate ester-based plasticizers, adipate ester-based plasticizers, trimellitate ester-based plasticizers, polyester-based plasticizers, polyol-based plasticizers, epoxy-based plasticizers, carbonate-based plasticizers, etc. In this embodiment, the plasticizers can be used alone or in combination of two or more.

[0087] Examples of carboxylic acid ester-based plasticizers include aliphatic carboxylic acid esters and aromatic carboxylic acid esters. Examples of aliphatic carboxylic acid esters include methyl acetylricinoleate, di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate, adipic acid-propylene glycol polyester, and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. Examples of aromatic carboxylic acid esters include phthalate esters (also referred to as phthalate ester-based plasticizers) such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, di-2-ethylhexyl phthalate, dilauryl phthalate, distearyl phthalate, and diisononyl phthalate.

[0088] Examples of phosphate ester plasticizers include tricresyl phosphate, trioctyl phosphate, triphenyl phosphate, etc. Examples of adipate ester plasticizers include di-2-ethylhexyl adipate, diisononyl adipate, diisodecyl adipate, etc. Examples of trimellitate ester plasticizers include trioctyl trimellitate, triisononyl trimellitate, triisodecyl trimellitate, 2-ethylhexyl trimellitate, etc.

[0089] Examples of polyester plasticizers include adipic acid polyesters, phthalic acid polyesters, and sebacic acid polyesters, with adipic acid polyesters being preferred because they are more likely to meet the water vapor permeability requirement. The weight average molecular weight of polyester plasticizers, particularly adipic acid polyesters, is preferably 500 to 10,000, more preferably 800 to 7,000, particularly preferably 1,200 to 5,000, and even more preferably 2,000 to 4,000. The weight average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0090] Examples of polyol-based plasticizers include glycol-based plasticizers such as diethylene glycol dibenzoate, dipropylene glycol dibenzoate, triethylene glycol dibenzoate, triethylene glycol di-(2-ethylbutyrate), triethylene glycol di-(2-ethylhexoate), and dibutylmethylene bisthioglycolate; and glycerin-based plasticizers such as glycerol monoacetate, glycerol triacetate, and glycerol tributyrate.

[0091] Examples of epoxy plasticizers include epoxidized soybean oil, epoxidized linseed oil, epoxidized butyl stearate, diethylhexyl epoxyhexahydrophthalate, diisodecyl epoxyhexahydrophthalate, epoxy triglyceride, epoxidized octyl oleate, epoxidized decyl oleate, etc. Examples of carbonate plasticizers include propylene carbonate, ethylene carbonate, etc.

[0092] The content of the plasticizer in the pressure-sensitive adhesive layer is not particularly limited, but is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 40 parts by mass, particularly preferably 1 to 35 parts by mass, and even more preferably 5 to 32 parts by mass, relative to 100 parts by mass of the acrylic acid ester polymer (A), which makes it easier to satisfy the water vapor permeability requirement described above.

[0093] In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive preferably contains a surfactant (G). The surfactant (G) has a hydrophilic group and makes it easier to satisfy the above-mentioned physical properties such as water vapor permeability.

[0094] Examples of surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, nonionic surfactants and anionic surfactants are preferred, and from the viewpoint of adhesive strength of the pressure-sensitive adhesive layer, nonionic surfactants are more preferred.

[0095] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene styrenated phenyl ethers, polyoxyethylene polyoxypropylene glycols, and block copolymers of polyoxyethylene and polyoxypropylene.

[0096] Examples of anionic surfactants include polyoxyethylene alkyl ether sulfates and salts thereof, polyoxyethylene alkyl phenyl ether sulfates and salts thereof, polyoxyethylene alkyl ether phosphates and salts thereof, and polyoxyethylene alkyl phenyl ether phosphates and salts thereof.

[0097] The content of the surfactant is preferably 0.01 to 4 mass%, more preferably 0.1 to 3 mass%, particularly preferably 0.3 to 2 mass%, even more preferably 0.5 to 1.5 mass%, and especially preferably 0.7 to 1.1 mass%, relative to 100 mass% of the adhesive, which makes it easier to satisfy the above-mentioned physical properties such as water vapor permeability.

[0098] When the pressure-sensitive adhesive composition P contains a silane coupling agent, the resulting pressure-sensitive adhesive has improved adhesion to glass members and plastic plates, thereby providing the resulting pressure-sensitive adhesive with better blister resistance.

[0099] The silane coupling agent 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.

[0100] Examples of such silane coupling agents 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; and mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane. , 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and other amino group-containing silicon compounds, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used alone or in combination of two or more.

[0101] When the pressure-sensitive adhesive composition P contains a silane coupling agent, the content thereof 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 2 parts by mass or less, particularly preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less.

[0102] (1-6) Preparation of adhesive composition The adhesive composition P can be produced by producing a (meth)acrylic acid polymer (A), and mixing the resulting (meth)acrylic acid ester polymer (A) with, if desired, a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), and additives such as a plasticizer (E), a silane coupling agent (F), and a surfactant (G).

[0103] 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.

[0104] Examples of the polymerization initiator include azo compounds, organic peroxides, etc., and two or more of them may be used in combination. In the polymerization step, the weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

[0105] Once the (meth)acrylic acid ester polymer (A) is obtained, if desired, a crosslinking agent (B), an active energy ray-curable component (C), a photopolymerization initiator (D), 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 pressure-sensitive 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.

[0106] 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.

[0107] 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, when obtaining the coating solution, the addition of a dilution solvent or the like is not a necessary condition, and as long as the adhesive composition P has a viscosity that allows coating, the addition of a dilution solvent is not necessary. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) itself serves as the dilution solvent.

[0108] (3) Manufacturing of adhesive sheets One example of a method for producing a pressure-sensitive adhesive sheet is to apply a coating solution of a pressure-sensitive adhesive composition to the release surface of one release sheet, heat-treat the pressure-sensitive adhesive composition to thermally crosslink it, form a coating layer, and then overlay the release surface of the other release sheet on the coating layer. If a curing period is required, a curing period is allowed, but if no curing period is required, the coating layer becomes the pressure-sensitive adhesive layer as is. This results in a pressure-sensitive adhesive sheet having a layer structure of release layer / pressure-sensitive adhesive layer / release layer.

[0109] 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.

[0110] After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (e.g., 23°C, 50% RH). If this curing period is required, the pressure-sensitive adhesive layer is formed after the curing period has elapsed; if no curing period is required, the pressure-sensitive adhesive layer is formed after the heat treatment has been completed.

[0111] Another example of a pressure-sensitive adhesive sheet production method is as follows. Specifically, a coating solution of a pressure-sensitive adhesive composition is applied to the release surface of one release sheet, followed by a heat treatment to thermally crosslink the pressure-sensitive adhesive composition, thereby forming a coating layer, thereby obtaining a release sheet α with a coating layer. A coating solution of a pressure-sensitive adhesive composition is applied to the release surface of the other release sheet, followed by a heat treatment to thermally crosslink the pressure-sensitive adhesive composition, thereby forming a coating layer, thereby obtaining a release sheet β with a coating layer. The release sheet α with a coating layer and the release sheet β with a coating layer are then bonded together so that the two coating layers are in contact with each other. If a curing period is required, a curing period is allowed; if no curing period is required, the laminated coating layers are left as is, forming a pressure-sensitive adhesive layer. This results in a desired pressure-sensitive adhesive sheet. This production example allows stable production even when the pressure-sensitive adhesive layer is thick.

[0112] Examples of methods that can be used to apply the adhesive composition coating solution include bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, and curtain coating.

[0113] The release sheet used here protects the adhesive layer until the adhesive sheet is used, and is peeled off when the adhesive sheet is used. In the adhesive sheet used, one or both of the release sheets are not necessarily required.

[0114] Examples of materials that can be used as release sheets 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 may also be used. From the perspective of the SDGs, the material constituting the release sheet may be a highly biomass material, a recyclable or reusable material, or a recycled or reused material.

[0115] The release surface of the release sheet (particularly the surface in contact with the pressure-sensitive adhesive layer) is 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. It is preferable that one of the release sheets 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.

[0116] There are no particular restrictions on the thickness of the release sheet, but it is usually about 20 to 150 μm.

[0117] (4) Thickness of the adhesive layer The thickness of the pressure-sensitive adhesive layer of the optical laminate of the present invention (measured in accordance with JIS K7130) is preferably 1 to 200 μm, more preferably 5 to 120 μm, particularly preferably 10 to 100 μm, even more preferably 20 to 80 μm, and most preferably 30 to 60 μm. This makes it easier to exert the desired adhesive strength, to meet the above-mentioned water vapor permeability, and to provide a route for water to escape, which in turn makes it easier to prevent discoloration of the polarizing plate.

[0118] The pressure-sensitive adhesive sheet of the present invention is preferably sandwiched between one gas-shielding member and another gas-shielding member, and either one of the one gas-shielding member and the other gas-shielding member is preferably used in an optical laminate including a polarizing plate.

[0119] Here, one example of the gas shielding member is an image display cell, etc., and another example of the gas shielding member is a front transparent plate, etc. These members will be described in detail in the section on members of the optical laminate to be described later.

[0120] 2) Optical laminate The optical laminate of the present invention is an optical laminate in which one gas shielding member and another gas shielding member are sandwiched via a pressure-sensitive adhesive layer, and one of the one gas shielding member and the other gas shielding member includes a polarizing plate, and the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive sheet according to claim 1 or 2, and the one gas shielding member and the other gas shielding member have a water vapor permeability of 0.001 g / (m) or less, measured in accordance with JIS K7129 under conditions of 40°C and 90% RH. 2 -24h) or less.

[0121] An example of the optical laminate of the present invention is shown in Figure 1. In Figure 1, 1 represents one gas shielding member (image display cell), 2 represents a polarizing plate, 3a and 3b represent pressure-sensitive adhesive layers, 4 represents another gas shielding member (front transparent plate), and 10 represents the optical laminate.

[0122] The optical laminate (10) shown in FIG. 1 is formed by bonding one gas shielding member (1) and a polarizing plate (2), and the polarizing plate (2) and another gas shielding member (4) together via pressure-sensitive adhesive layers (3a) and (3b).

[0123] A typical example of one gas shielding member is an image display cell, and a typical example of the other gas shielding member is a glass plate. For example, the optical laminate (10) may be an optical laminate including an image display cell (1), a polarizing plate (2), and a front transparent plate (4), in which the polarizing plate (2) is bonded to the front transparent plate (4) via an adhesive layer (3b), and the front transparent plate (4) is made of a material with low water vapor permeability, such as a glass plate. The optical laminate (10) is inhibited from discoloring the polarizing plate even when left in a high-temperature environment for a long period of time, and is also excellent in resistance to moist heat whitening and blister resistance. In this specification, the term "high humidity environment" refers to a humid and hot environment of, for example, 85°C and 85% RH.

[0124] (Image display cell) The image display cell that is one gas shielding member may be, for example, an organic EL cell or a liquid crystal cell. As the organic EL cell, a light-emitting body (organic electroluminescence light-emitting body) is preferably formed by sequentially laminating a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate. The organic light-emitting layer is a laminate of various organic thin films, and various layer configurations can be adopted, such as a laminate of a hole-injection layer made of a triphenylamine derivative or the like and a light-emitting layer made of a fluorescent organic solid such as anthracene, a laminate of such a light-emitting layer and an electron-injection layer made of a perylene derivative or the like, or a laminate of a hole-injection layer, a light-emitting layer, and an electron-injection layer.

[0125] The liquid crystal cell may be a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, or a semi-transmissive semi-reflective liquid crystal cell that uses both external light and light from the light source. When the liquid crystal cell uses light from a light source, a polarizing film laminate is also arranged on the side opposite to the viewing side of the image display cell (liquid crystal cell), and a light source such as a backlight is also arranged. The polarizing film laminate on the light source side and the liquid crystal cell are bonded with an appropriate transparent adhesive layer. The liquid crystal cell may be driven in any type of mode, such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type).

[0126] The optical laminate (10) shown in Fig. 1 may include a polarizing plate (2) on the viewing side of an image display cell (1) such as an organic EL cell or a liquid crystal cell, and may further include a front transparent plate (4) on the viewing side. An optical film such as a polarizing plate or an optical element such as a backlight (not shown) may be provided on the opposite side of the image display cell (1). The image display cell (1) and the polarizing plate (2), and the polarizing plate (2) and the full-transparent plate (4) are bonded together via adhesive layers (3a, 3b). The water vapor permeability of the image display cell (1) measured in accordance with JIS K7129 under conditions of 40°C and 90% RH is usually 0.001 g / (m 2 24h or less.

[0127] (polarizing plate) The polarizing plate (2) includes a polarizer. The polarizer is a polyvinyl alcohol-based film (hereinafter, sometimes referred to as a "PVA film") containing iodine. The PVA film used in the polarizer is made of polyvinyl alcohol or a derivative thereof. Examples of polyvinyl alcohol derivatives include polyvinyl formal; polyvinyl acetal; and polyvinyl alcohol modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and their esters, acrylamide, etc. Polyvinyl alcohols with a degree of polymerization of about 1,000 to 10,000 and a degree of saponification of about 80 to 100 mol % are generally used.

[0128] A polarizer can be obtained by dyeing a PVA film with iodine and stretching it. The dyeing treatment is carried out, for example, by immersing the PVA film in an iodine solution. The temperature of the iodine solution is usually about 20 to 50°C, and the immersion time is usually about 10 to 300 seconds.

[0129] The PVA film may contain additives such as plasticizers. Examples of plasticizers include polyols and other condensates. Specific examples of plasticizers include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of plasticizer used is not particularly limited, but is usually 20% by mass or less in the PVA film.

[0130] The stretching treatment is a treatment in which the PVA film is stretched in at least one direction. Generally, the PVA film is stretched uniaxially in the machine direction. The stretching method can be either a wet stretching method or a dry stretching method. The PVA film that has been subjected to each of the above treatments is subjected to water washing treatment and drying treatment according to the information.

[0131] The polarizing plate (2) preferably has a transparent protective film on both sides of the polarizer. The polarizer and the transparent protective film can be attached to each other via an appropriate adhesive layer.

[0132] Examples of materials constituting the transparent protective film include thermoplastic resins that are excellent in transparency, mechanical strength, and thermal stability. Examples include cellulose-based resins such as triacetyl cellulose, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic resins, cyclic olefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof. Among these, cellulose-based resins such as triacetyl cellulose are preferred from the viewpoint of high moisture permeability and suppressing retention of moisture in the polarizer.

[0133] (Front transparent plate) The optical laminate (10) of the present invention has a water vapor permeability of 0.001 g / (m) measured in accordance with JIS K7129 under conditions of 40°C and 90% RH. 2 A front transparent plate (4) is used for 24 hours or less. The front transparent plate preferably has a total light transmittance of 80% or more, preferably 90% or more, and more preferably 95% or more. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance can be measured, for example, using a known total light transmittance measuring device.

[0134] A preferred example of such a front transparent plate is a glass plate. Examples of the glass plate 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. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 10 mm, and preferably 0.2 to 5 mm.

[0135] On one or both sides of the front transparent plate, various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare layer, etc.) may be provided, or optical members may be laminated. Furthermore, the transparent conductive film and metal layer may be patterned.

[0136] (optical laminate) Examples of the optical laminate include a liquid crystal (LCD) display, a light-emitting diode (LED) display, an organic electroluminescence (organic EL) display, and electronic paper, and may also be a touch panel. The display may also be a component constituting a part of any of these.

[0137] The optical laminate can be produced, for example, as follows. (Step 1) First, two adhesive sheets are prepared. The adhesive layers of the two adhesive sheets may have the same composition or different compositions. (Step 2) One release sheet of one of the adhesive sheets is peeled off, and the exposed adhesive layer of the adhesive sheet is attached to the surface of the image display cell (the surface on the printed layer side, if a printed layer is present). At this time, the adhesive layer has excellent initial step-conforming properties, so gaps and lifting near the steps caused by the printed layer are suppressed. (Step 3) Next, the other release sheet is peeled off from the adhesive layer of the adhesive sheet, and the exposed adhesive layer of the adhesive sheet is attached to a polarizing plate to obtain a laminate. (Step 4) Then, one release sheet of the other adhesive sheet is peeled off on the polarizing plate, and the exposed adhesive layer of the adhesive sheet is attached to the viewing side of the polarizing plate. (Step 5) Next, the other release sheet is peeled off from the adhesive layer of the adhesive sheet, and the exposed adhesive layer of the adhesive sheet is attached to the front transparent plate to obtain a laminate. (Step 6) Thereafter, the adhesive layer is irradiated with active energy rays to cure the adhesive, thereby converting the adhesive layer into a cured adhesive layer, thereby obtaining the desired optical laminate. The irradiation of active energy rays is usually carried out through a front transparent plate, from the viewpoint of high transparency and avoiding damage to the image display cell due to the irradiation of active energy rays.

[0138] 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.

[0139] The ultraviolet irradiation can be performed using a high-pressure mercury lamp, a Heraeus H lamp, a xenon lamp, or the like, and the amount of ultraviolet irradiation is set to an illuminance of 50 to 1000 mW / cm. 2 The light intensity is preferably about 50 to 10,000 mJ / cm. 2 is preferably 80 to 5000 mJ / cm 2 More preferably, it is 200 to 2000 mJ / cm 2 On the other hand, the electron beam irradiation can be carried out by an electron beam accelerator or the like, and the irradiation dose of the electron beam is preferably about 10 to 1000 krad.

[0140] In the optical laminate of the present invention, since the front transparent plate has a low water vapor permeability, In the display element according to this embodiment, the cured adhesive layer has excellent resistance to heat and humidity whitening, so that even if the display element is placed under high temperature conditions (e.g., 85°C, 85% RH, 120 hours) and then returned to room temperature and humidity, the cured adhesive layer is prevented from whitening.

[0141] Furthermore, since the gel fraction of the adhesive constituting the cured adhesive layer is within the above-mentioned range, the adhesive exhibits excellent cohesive strength, and the display body can exhibit excellent blister resistance.

[0142] 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.

[0143] For example, one of the two release sheets in the pressure-sensitive adhesive sheet may be omitted. The front transparent plate may have a step in the printed layer or a step other than the printed layer, or may have no step. Furthermore, not only the front transparent plate but also the image display cell may have a step on the pressure-sensitive adhesive layer side after curing. [Example]

[0144] 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.

[0145] Example 1 Step 1. Preparation of (meth)acrylic acid ester polymer (A) A (meth)acrylic acid ester polymer was prepared as the main component (A) by copolymerizing 70 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of N-acryloylmorpholine, 10 parts by mass of isobornyl acrylate, and 10 parts by mass of 2-hydroxyethyl acrylate by solution polymerization. The molecular weight of this (meth)acrylic acid ester polymer was measured by the method described below, and the mass average molecular weight (Mw) was 500,000.

[0146] Step 2. Preparation of adhesive composition 100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth)acrylic acid ester polymer as the main component (A) obtained in the above step 1, 0.2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E") as the crosslinking agent (B), and 6 parts by mass of ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "A-9300-1CL") as the active energy ray-curable component (C). 0.8 parts by mass of a mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator (D) mixed in a 1:1 mass ratio, 10 parts by mass of dibutoxyethoxyethyl adipate as a plasticizer (E), and 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent (F) were mixed, stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0147] Here, the formulations (solid content equivalent) of the pressure-sensitive adhesive compositions when the (meth)acrylic acid ester polymer as the main component (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)] 2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate MA: methyl acrylate ACMO: 4-acryloylmorpholine IBXA: Isobornyl acrylate HEA: 2-hydroxyethyl acrylate [Crosslinking agent (B)] B1: Isocyanate-based crosslinking agent (Mitsui Chemicals, product name "Takenate D-101E") B2: Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate HX") [Active energy ray-curable component (C)] C1: ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "A-9300-1CL") [Photopolymerization initiator (D)] D1: A mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone in a 1:1 mass ratio D2: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide D3: 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate (manufactured by San-Apro Co., Ltd., product name "CPI-100P", ionic photoacid generator) [Plasticizer (E)] E1: Dibutoxyethoxyethyl adipate E2: Tributyl acetyl citrate [Silane coupling agent (F)] F1: 3-glycidoxypropyltrimethoxysilane [Surfactant (G)] G1: Nonionic surfactant (manufactured by Daiichi Pharmaceutical Co., Ltd., product name "Noigen GIS-320") G2: Polyoxyethylene polyoxypropylene glycol (manufactured by Daiichi Pharmaceutical Co., Ltd., product name "Epane 720")

[0148] 3. Manufacturing of adhesive sheets The adhesive composition coating solution obtained in step 2 above was applied using a knife coater to the release-treated surface of a heavy-release release sheet R1 (thickness: 75 μm), one side of which had been treated with a silicone-based release agent for release of a polyethylene terephthalate film, and then heated at 90°C for 1 minute to form a coating layer (thickness: 50 μm). The coating layer side of the resulting release sheet R1 with coating layer was bonded to the release-treated surface of a light-release release sheet R2 (thickness: 38 μm), one side of which had been treated with a silicone-based release agent for release of a polyethylene terephthalate film, and the mixture was aged for 7 days under conditions of 23°C and 50% RH to produce an adhesive sheet consisting of release sheet R1 / adhesive layer (thickness: 50 μm) / release sheet R2.

[0149] The thickness of the adhesive layer was measured using a constant pressure thickness measuring device (manufactured by Teclock Corporation, product name "PG-02") in accordance with JIS K 7130. It was also confirmed that, in the resulting adhesive sheets, release sheet R1 had a greater peel strength from the adhesive than release sheet R2.

[0150] [Examples 2 to 10, Comparative Example 1] An adhesive sheet was produced in the same manner as in Example 1, except that the types and proportions of the monomers constituting the main agent (A), the mass average molecular weight (Mw) of the main agent (A), the type and amount of the crosslinking agent (B), the amount of the active energy ray-curable component (C), the type and amount of the photopolymerization initiator (D), the type and amount of the plasticizer (E), and the type of the surfactant (G) were changed as shown in Table 1.

[0151] Comparative Example 2 (Preparation of Adhesive Composition) 100 parts by mass of phenoxy resin (a reaction product of biphenyl-containing diol and bisphenol diglycidyl ether, glass transition temperature (Tg): 70°C, Mw: 55,000, hydroxyl equivalent = 270 g / eq, manufactured by Nippon Steel Chemical & Material Co., Ltd., product name "YP70") as the main component (A), and cyclic ether group-containing compound (a reaction product of butylene glycol and bisphenol A diglycidyl ether, properties at 23°C: liquid, epoxy equivalent: 440 g / eq, glass transition temperature (Tg) when homopolymerized: -69°C, viscosity (23°C): 200 mPa, manufactured by Mitsubishi Chemical Co., Ltd.) A coating solution of an adhesive composition was prepared by mixing 60 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mikal Corporation, product name "YX7400") as the crosslinking agent (B) (manufactured by Tosoh Corporation, product name "Coronate HX"), 0.8 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate HX") as the photopolymerization initiator (D) (4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, manufactured by San-Apro Co., Ltd., product name "CPI-100P"), and 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane as the silane coupling agent (F). The mixture was thoroughly stirred and diluted with methyl ethyl ketone.

[0152] An adhesive sheet was manufactured in the same manner as in Example 1, except that a coating solution of the adhesive composition was prepared as described above and the thickness of the adhesive layer of the adhesive sheet ("Thickness (μm)" in Table 1) was changed as shown in Table 1.

[0153] Here, the above-mentioned mass average molecular weight (Mw) is a polystyrene-equivalent mass 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℃

[0154] [Test Example 1] (Measurement of water vapor permeability) The adhesive layers of the adhesive sheets of the Examples and Comparative Examples were appropriately laminated to prepare an adhesive layer having a thickness of 200 μm. A triacetyl cellulose film (TAC, thickness: 80 μm, manufactured by Konica Minolta, Inc., product name "Konica Minolta TAC Film KC8UX2MW") was attached to the obtained adhesive layer. Next, ultraviolet light was irradiated under the following conditions to cure the adhesive layer to form a cured adhesive layer, and a laminate sample of the cured adhesive layer / TAC film was obtained. <Ultraviolet irradiation conditions> -High pressure mercury lamp used ·Illuminance 200mW / cm 2 ,Light intensity 1000mJ / cm 2 The UV illuminance and light intensity meter used is the "UVPF-A1" manufactured by Eye Graphics.

[0155] Next, the laminate sample was measured for water vapor permeability (g / (m)) in accordance with JIS Z0208 under conditions of 40°C and 90% RH. 2 The results are shown in Table 2.

[0156] [Test Example 2] (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.

[0157] 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 adhesive alone was calculated by subtracting the mass of the mesh alone. This mass was designated M2. The gel fraction (%) is expressed as (M2 / M1)×100. The gel fraction of the adhesive (before UV irradiation) was calculated from this data. The results are shown in Table 2.

[0158] The pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples were irradiated with ultraviolet (UV) rays through the release sheet R2 under the same UV irradiation conditions as in Test Example 1 to cure the pressure-sensitive adhesive layer, forming a cured pressure-sensitive adhesive layer. The gel fraction (after UV) of the pressure-sensitive adhesive in this cured pressure-sensitive adhesive layer was calculated in the same manner as above. The results are shown in Table 2.

[0159] [Test Example 3] (Measurement of adhesive strength) The release sheet R2 was peeled off from the adhesive sheets obtained in the Examples and Comparative Examples, and the exposed adhesive layer was attached to an adhesive layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360", thickness: 100 μm) having an adhesive layer to obtain a release sheet R1 / adhesive layer / PET film laminate. The resulting laminate was cut into a width of 25 mm and a length of 100 mm.

[0160] The release sheet R1 was peeled from the laminate at 23°C and 50% RH, and the exposed adhesive layer was attached to a soda-lime glass (Nippon Sheet Glass Co., Ltd.). The sample was then pressurized at 0.5 MPa and 50°C for 20 minutes in a Kurihara Manufacturing Co., Ltd. autoclave. This sample was used as a measurement sample (pre-UV). After leaving the sample at 23°C and 50% RH for 24 hours, the adhesive strength (N / 25 mm) of the measurement sample (pre-UV) was measured using a tensile tester (Orientec Co., Ltd., Tensilon) at a peel rate of 300 mm / min and a peel angle of 180°. Measurements were conducted under conditions other than those described here in accordance with JIS Z0237:2009. The results are shown in Table 2.

[0161] The pressure-sensitive adhesive layer of the measurement sample (before UV) prepared above was irradiated with ultraviolet (UV) light through the PET film under the same UV irradiation conditions as in Test Example 1, curing the pressure-sensitive adhesive layer to form a cured pressure-sensitive adhesive layer, which was used as the measurement sample (after UV). After leaving the sample for 24 hours at 23°C and 50% RH, the measurement sample (after UV) having the cured pressure-sensitive adhesive layer was measured for adhesive strength (N / 25 mm) using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.) at a peel speed of 300 mm / min and a peel angle of 180°. Measurements were conducted under conditions other than those described here in accordance with JIS Z 0237:2009. The results are shown in Table 2.

[0162] [Test Example 4] (Measurement of total light transmittance) For the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, background measurement was performed using a soda-lime glass plate, and then the total light transmittance (%) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7361-1:1997. The pressure-sensitive adhesive layers were then irradiated with ultraviolet (UV) rays under the same ultraviolet irradiation conditions as in Test Example 1 to cure the pressure-sensitive adhesive layers and obtain cured pressure-sensitive adhesive layers. The total light transmittance (%) of the cured pressure-sensitive adhesive layers was also measured in the same manner as above. The results are shown in Table 2.

[0163] [Test Example 5] (Haze Value Measurement) The haze value (%) of the adhesive layer of the adhesive sheet obtained in the Examples and Comparative Examples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-2000") in accordance with JIS K7136:2000. The adhesive layer was then irradiated with ultraviolet (UV) light under the same ultraviolet irradiation conditions as in Test Example 1 to cure the adhesive layer and obtain a cured adhesive layer. The haze value (%) of the cured adhesive layer was also measured in the same manner as above. The results are shown in Table 2.

[0164] [Test Example 6] (Measurement of water absorption rate) The release sheet R2 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 "Cosmoshine A4360", thickness: 100 μm) having an easy-adhesion layer, to obtain a laminate consisting of release sheet R1 / pressure-sensitive adhesive layer / PET film. The pressure-sensitive adhesive layer was irradiated with ultraviolet (UV) rays through the PET film under the same ultraviolet irradiation conditions as in Test Example 1, and the pressure-sensitive adhesive layer was cured to form a cured pressure-sensitive adhesive layer. The obtained laminate was cut into a width of 150 mm and a length of 150 mm to prepare a measurement sample. The release sheet R1 was peeled off from the measurement sample before testing, and the pre-test mass was measured.

[0165] The above measurement samples were placed in a humid and hot environment of 60°C and 90% RH for 24 hours. The post-test mass was measured within 10 minutes after removal. The water absorption rate (%) was calculated from the obtained measurements using the following formula (1). The results are shown in Table 2. Water absorption rate (%) = {(mass after test - mass before test) / mass before test} × 100 ... (1)

[0166] Test Example 7 (Measurement of storage modulus) The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples were laminated together to form a 3 mm thick laminate. A cylinder 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 the sample (before UV). The pressure-sensitive adhesive layer of the sample (before UV) was irradiated with ultraviolet (UV) rays under the same ultraviolet irradiation conditions as in Test Example 1 to cure the pressure-sensitive adhesive layer, which was used as the sample (after UV).

[0167] The storage modulus G' of the above sample (before UV irradiation) and sample (after UV irradiation) was measured under the following conditions by the torsional shear method using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR301") in accordance with JIS K7244-1, and the storage modulus (MPa) before and after UV irradiation at 23°C was obtained. The results are shown in Table 2. Measurement frequency: 1Hz Measurement temperature: 0℃~50℃

[0168] [Test Example 8] (Heat resistance evaluation) The release sheet R2 was peeled off from the pressure-sensitive adhesive sheet obtained in Comparative Example 1, and the exposed pressure-sensitive adhesive layer was attached to a polarizing plate made of soda-lime glass (thickness: 1.1 mm) on which a polarizing plate had been laminated.

[0169] The release sheet R2 was peeled off from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was then attached to soda-lime glass (thickness: 1.1 mm) by peeling off the release sheet R1, to produce a laminate of soda-lime glass / pressure-sensitive adhesive layer / polarizing plate / pressure-sensitive adhesive layer (Comparative Example 1) / soda-lime glass, which was used as the evaluation sample. The planar size of the laminate was 7 cm x 7 cm.

[0170] The evaluation sample was pressurized in a Kurihara Manufacturing Co., Ltd. autoclave at 0.5 MPa and 50°C for 20 minutes, then left to stand in a high-temperature environment at 105°C for 7 days, and then left to stand in an environment at room temperature and 50% RH for 24 hours. The color change of the evaluation sample before and after being placed in the high-temperature environment was visually confirmed, and heat resistance was evaluated according to the following evaluation criteria. The results are shown in Table 2. ○: No change in color was observed. △: The change in color was about 50% within the plane of the evaluation sample. ×: Discoloration was observed in more than half of the plane of the evaluation sample.

[0171] [Table 1]

[0172] [Table 2]

[0173] As can be seen from Table 2, the cured adhesive layer formed using the adhesive sheet obtained in the example was excellent at suppressing discoloration of the polarizing plate even when placed in a high-temperature environment. [Industrial Applicability]

[0174] The pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, for bonding to a display component having a desired high water vapor barrier property. [Explanation of symbols]

[0175] 1. One gas shielding member (image display cell) 2. Polarizing plate 3a, 3b...Adhesive sheet 4. Other gas shielding components (front transparent plate) 10. Image display device

Claims

1. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of an active energy ray-curable pressure-sensitive adhesive, The pressure-sensitive adhesive layer having a thickness of 200 μm is cured by irradiation with active energy rays, and the cured pressure-sensitive adhesive layer is measured at 40° C. and 90% RH in accordance with JIS Z0208 to have a water vapor permeability of 160 g / (m ２ 24h 200 μm or more).

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer after curing is 20% or more and 95% or less.

3. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer further contains a plasticizer. The pressure-sensitive adhesive sheet according to claim 1 or 2.

4. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive. The pressure-sensitive adhesive sheet according to claim 1 or 2.

5. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet is sandwiched between one gas-shielding member and another gas-shielding member, and either one of the gas-shielding member and the other gas-shielding member is used in an optical laminate including a polarizing plate.

6. An optical laminate comprising one gas shielding member and another gas shielding member sandwiched together via a pressure-sensitive adhesive layer, wherein one of the one gas shielding member and the other gas shielding member includes a polarizing plate, The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive sheet according to claim 1 or 2, The one gas shielding member and the other gas shielding member have a water vapor permeability of 0.001 g / (m) measured in accordance with JIS K7129 under conditions of 40°C and 90% RH. ２ An optical laminate characterized by having a shelf life of 24h or less.

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