Adhesive sheet, optical laminate and image display device

Abstract

To provide an adhesive sheet which can suppress changes in the dimensions of an optical film included in an optical laminate and is suitable for securing durability and transparency.SOLUTION: There is provided an adhesive sheet wherein when 10 evaluation areas of 1.5 μm square are arbitrarily set for a cross-sectional view of the adhesive sheet and an island-shaped area having a short diameter of 100 nm or more is defined as a first domain, the number of the evaluation areas in which the first domain is present is 5 or less and the adhesive sheet has a haze of 0.1% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet, an optical laminate, and an image display device. [Background technology]

[0002] In recent years, image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices), have rapidly become popular. These various image display devices typically have a laminated structure of an image-forming layer, such as a liquid crystal layer or an EL light-emitting layer, and an optical laminate including an optical film and an adhesive sheet. The adhesive sheet is mainly used to bond between films included in the optical laminate or to bond between the image-forming layer and the optical laminate. Examples of optical films include polarizing plates, retardation films, and polarizing plates with retardation films, which are formed by integrating a polarizing plate and a retardation film. Patent Documents 1 and 2 disclose examples of optical laminates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-031214 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-98665 Summary of the Invention [Problem to be solved by the invention]

[0004] Excessive changes in the dimensions of optical films due to temperature changes can cause light leakage and color unevenness in image display devices. Light leakage and color unevenness are particularly likely to occur in relatively large image display devices that use polarizing plates with retardation films. In addition, image display devices designed with narrow bezels (narrowed bezels) are becoming more common, making it increasingly important to suppress dimensional changes. One way to suppress dimensional changes is to increase the elastic modulus of the pressure-sensitive adhesive sheet included in the optical laminate. However, simply increasing the elastic modulus can reduce the durability of the pressure-sensitive adhesive sheet, making it unable to follow dimensional changes, and can also impair the transparency desired for an optical pressure-sensitive adhesive sheet.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive sheet that can suppress dimensional changes in an optical film contained in an optical laminate and is suitable for ensuring durability and transparency. [Means for solving the problem]

[0006] The present invention provides An adhesive sheet, Ten evaluation regions of 1.5 μm square are arbitrarily set on a cross-sectional image of the pressure-sensitive adhesive sheet, and when an island-like region having a short diameter of 100 nm or more is defined as a first domain, the number of evaluation regions in which the first domain exists is 5 or less, A haze of 0.1% or more Adhesive sheet, to provide.

[0007] In another aspect, the present invention provides a method for producing a composition comprising: An optical laminate comprising the pressure-sensitive adhesive sheet of the present invention and an optical film; to provide.

[0008] In another aspect, the present invention provides a method for producing a composition comprising: An image display device comprising the optical laminate of the present invention. to provide. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that can suppress dimensional changes in the optical film contained in the optical laminate and is suitable for ensuring durability and transparency. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of the pressure-sensitive adhesive sheet of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing an example of an optical laminate including the pressure-sensitive adhesive sheet of the present invention. [Figure 3] FIG. 3 is a cross-sectional view schematically showing an example of an optical laminate including the pressure-sensitive adhesive sheet of the present invention. [Figure 4] FIG. 4 is a cross-sectional view schematically showing an example of an optical laminate including the pressure-sensitive adhesive sheet of the present invention. [Figure 5] FIG. 5 is a cross-sectional view that schematically shows an example of an optical laminate that includes the pressure-sensitive adhesive sheet of the present invention. [Figure 6] FIG. 6 is a cross-sectional view that schematically shows an example of an image display device that includes the pressure-sensitive adhesive sheet of the present invention. [Figure 7A] FIG. 7A is a diagram showing a cross-sectional image of the pressure-sensitive adhesive sheet produced in Example 3, taken by a transmission electron microscope (TEM). [Figure 7B] FIG. 7B is a diagram showing a cross-sectional TEM image of the pressure-sensitive adhesive sheet produced in Example 8. [Figure 7C] FIG. 7C is a diagram showing a cross-sectional TEM image of the pressure-sensitive adhesive sheet produced in Example 9. [Figure 7D] FIG. 7D is a diagram showing a cross-sectional image of the pressure-sensitive adhesive sheet produced in Comparative Example 3, taken by TEM. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings, but is not limited to the following embodiments.

[0012] In this specification, "(meth)acrylic" means acrylic and methacrylic, and "(meth)acrylate" means acrylate and methacrylate.

[0013] [Adhesive sheet] An example of a pressure-sensitive adhesive sheet according to this embodiment is shown in Fig. 1. In the pressure-sensitive adhesive sheet 1 shown in Fig. 1, ten evaluation regions each measuring 1.5 µm square are arbitrarily set in a cross-sectional image of the pressure-sensitive adhesive sheet 1. When an island-like region having a minor axis of 100 nm or more is defined as a first domain, the number of evaluation regions containing first domains is five or less. The pressure-sensitive adhesive sheet 1 also has a haze of 0.1% or more.

[0014] One possible way to increase the elastic modulus of a pressure-sensitive adhesive sheet is to incorporate an additive into the pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive sheet. It is difficult for the additive to be completely compatible with the material contained in the pressure-sensitive adhesive composition, typically the polymer that serves as the main component, and the additive. Therefore, it is believed that incorporating an additive increases the haze of the pressure-sensitive adhesive sheet. According to the inventors' studies, it has been found that when domains of a certain size or larger are formed in a pressure-sensitive adhesive sheet with increased haze, the durability and transparency of the pressure-sensitive adhesive sheet tend to decrease. The formation of domains can cause whitening of the pressure-sensitive adhesive sheet due to light scattering and reflection at the domain interfaces, and can also cause the formation of voids and the like due to peeling at the domain interfaces when the pressure-sensitive adhesive sheet is deformed by an external force. Further studies have shown that the haze of a pressure-sensitive adhesive sheet with a haze of 0.1 % or more and with the domains in the above state, the pressure-sensitive adhesive sheet 1 can suppress dimensional changes in the optical film and is suitable for ensuring durability and transparency.

[0015] In this specification, the haze of the pressure-sensitive adhesive sheet 1 is the value when the sheet has a thickness of 75 μm, and can be measured in accordance with Japanese Industrial Standards (formerly Japanese Industrial Standards; JIS) K7136:1981.

[0016] The haze of the pressure-sensitive adhesive sheet 1 may be 0.2% or more. The upper limit of the haze is, for example, 1% or less, and may be 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, less than 0.5%, 0.45% or less, less than 0.43%, 0.4% or less, or even less than 0.37%.

[0017] In this specification, a domain refers to an island-like region of a sea-island structure that the pressure-sensitive adhesive sheet 1 may have. The domain may contain a substance derived from an additive. The minor axis of a domain can be determined as the length of the shortest imaginary line segment when a virtual line segment passing through the center of gravity of the domain and having the periphery of the domain at both ends is imagined on the cross-sectional image. It is preferable that the evaluation regions set in the cross-sectional image do not overlap with each other. The cross-sectional image can be obtained, for example, using a transmission electron microscope (TEM). The magnification of the obtained cross-sectional image is, for example, 10,000 to 30,000 times.

[0018] The number of evaluation regions in which the first domain exists may be four or less, three or less, two or less, one or less, or even zero.

[0019] For all first domains observed in the 10 evaluation regions set in the cross-sectional image of the pressure-sensitive adhesive sheet 1, the shortest distance between adjacent first domains may be 300 nm or more, 500 nm or more, or even 800 nm or more. A large shortest distance means a low density of the domains in the pressure-sensitive adhesive sheet 1. The distance between adjacent domains can be determined as the distance between their outer peripheries.

[0020] When an island-like region having a short axis of 50 nm or more and less than 100 nm is defined as a second domain, the number of evaluation regions having 10 or less second domains among the 10 evaluation regions set in the cross-sectional image of the pressure-sensitive adhesive sheet 1 may be 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or even 10. According to studies by the present inventors, the second domains can affect the durability and transparency of the pressure-sensitive adhesive sheet 1, although not as much as the first domains.

[0021] When an island-like region having a short diameter of 50 nm or more and less than 100 nm is defined as a second domain, for all second domains observed in the above-mentioned 10 evaluation regions set in the cross-sectional image of the adhesive sheet 1, the shortest distance between adjacent second domains may be 150 nm or more, 175 nm or more, or even 200 nm or more.

[0022] When an island-like region having a short diameter of 50 nm or more and less than 100 nm is defined as a second domain, the proportion (proportion by number) of second domains in which the shortest distance between adjacent second domains is 100 nm or more among all second domains observed in the above-mentioned 10 evaluation regions set in the cross-sectional image of the adhesive sheet 1 may be 50% or more, 60% or more, or even 70% or more.

[0023] The state of the domains in the pressure-sensitive adhesive sheet 1 can be evaluated, for example, by image analysis of a cross-sectional image. For image analysis, various software such as ImageJ can be used.

[0024] The state of the domains in the pressure-sensitive adhesive sheet 1 changes depending on the manufacturing conditions of the pressure-sensitive adhesive sheet 1 (including the heating conditions described below). The state of the domains also changes depending on the composition of the pressure-sensitive adhesive composition (I), p) It can vary based on the composition and properties (for example, glass transition temperature) of the acrylic polymer (A), the type and amount of the crosslinking agent (B), and the type and amount of additives.

[0025] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 1 to 200 μm, and may be 5 to 150 μm, 10 to 100 μm, 10 to 75 μm, 10 to 50 μm, 10 to 40 μm, 10 to 30 μm, or even 10 to 20 μm.

[0026] The storage modulus G' (25°C) of the pressure-sensitive adhesive sheet 1 is, for example, 0.15 MPa or more, and may be 0.16 MPa or more, 0.17 MPa or more, or even 0.18 MPa or more. The upper limit of the storage modulus G' (25°C) is, for example, 5 MPa or less, and may be 3.0 MPa or less, 2.5 MPa or less, 2.0 MPa or less, 1.5 MPa or less, 1.0 MPa or less, 0.8 MPa or less, 0.6 MPa or less, 0.5 MPa or less, or even less than 0.5 MPa. Pressure-sensitive adhesive sheets 1 having a storage modulus G' within the above range are particularly suitable for suppressing dimensional changes in optical films.

[0027] The storage modulus (25°C) of the pressure-sensitive adhesive sheet 1 can be evaluated by the following method. First, a measurement sample made of the material that constitutes the pressure-sensitive adhesive sheet 1 is prepared. The measurement sample is disc-shaped. The measurement sample has a bottom diameter of 8 mm and a thickness of 2 mm. The measurement sample may be obtained by punching out a disc from a laminate in which multiple pressure-sensitive adhesive sheets 1 are stacked. Next, dynamic viscoelasticity measurement is performed on the measurement sample. For example, an ARES-G2 manufactured by TA Instruments can be used for the dynamic viscoelasticity measurement. The storage modulus G' at 25°C of the pressure-sensitive adhesive sheet 1 can be determined from the results of the dynamic viscoelasticity measurement. The conditions for the dynamic viscoelasticity measurement are as follows: Measurement conditions Frequency: 1Hz Deformation mode: Torsion Measurement temperature: -70℃~150℃ Heating rate: 5°C / min

[0028] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 60% or more, and may be 65% or more, or even 70% or more. The upper limit of the gel fraction is, for example, 99% or less, 98% or less, or even 95% or less. Pressure-sensitive adhesive sheets 1 having a gel fraction within the above range are particularly suitable for suppressing dimensional changes in optical films.

[0029] The gel fraction of the pressure-sensitive adhesive sheet 1 can be evaluated by the following method. First, approximately 0.2 g is scraped off from the pressure-sensitive adhesive sheet 1 to obtain a small piece. Next, the obtained small piece is wrapped in a stretched porous polytetrafluoroethylene membrane (NTF1122 manufactured by Nitto Denko, average pore size 0.2 μm) and tied with kite string to obtain a test piece. Next, the weight A of the obtained test piece is measured. Weight A is the total weight of the pressure-sensitive adhesive sheet piece, the stretched porous membrane, and the kite string. The total weight B of the stretched porous membrane and kite string used is measured in advance. Next, the test piece is immersed in a 50 mL container filled with ethyl acetate and left to stand at 23°C for one week. After standing, the test piece is removed from the container and dried for two hours in a dryer set at 130°C, after which the weight C of the test piece is measured. The gel fraction of the pressure-sensitive adhesive sheet 1 is calculated from the measured weights A, B, and C using the formula: gel fraction (wt %)=(CB) / (AB)×100(%).

[0030] The pressure-sensitive adhesive sheet 1 may be formed from a pressure-sensitive adhesive composition (I) containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate-based crosslinking agent (B). However, the composition of the pressure-sensitive adhesive sheet 1 is not limited to the above example.

[0031] [Adhesive composition (I)] The pressure-sensitive adhesive composition (I) contains a (meth)acrylic polymer (A) and an isocyanate-based crosslinking agent (B). The (meth)acrylic polymer (A) is contained in the pressure-sensitive adhesive composition (I) as a main component. In other words, the pressure-sensitive adhesive composition (I) is an acrylic pressure-sensitive adhesive composition. The main component refers to the component with the largest content in the composition. The content of the main component is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 73% by weight or more, or even 75% by weight or more.

[0032] ((Meth)acrylic polymer (A)) The (meth)acrylic polymer (A) preferably has, as a main unit, a structural unit derived from a (meth)acrylic monomer (A1) having an alkyl group of 1 to 30 carbon atoms on the side chain. The alkyl group may be linear or branched. The (meth)acrylic polymer (A) may have one or more structural units derived from the (meth)acrylic monomer (A1). Examples of the (meth)acrylic monomer (A1) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, and isoheptyl (meth)acrylate. acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, and n-tetradecyl(meth)acrylate. In this specification, the term "main unit" refers to a unit that accounts for, for example, 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and even more preferably 80% by weight or more of all the structural units contained in the polymer.

[0033] The (meth)acrylic polymer (A) may have a structural unit derived from a (meth)acrylic monomer (A1) having a long-chain alkyl group on the side chain. An example of the monomer (A1) is n-dodecyl (meth)acrylate (lauryl (meth)acrylate). In this specification, the term "long-chain alkyl group" refers to an alkyl group having 6 to 30 carbon atoms.

[0034] The (meth)acrylic polymer (A) may have a structural unit derived from a (meth)acrylic monomer (A1) which, when made into a homopolymer, has a glass transition temperature (Tg) in the range of −70 to −20° C. An example of the monomer (A1) is n-butyl acrylate.

[0035] The (meth)acrylic polymer (A) may contain a structural unit other than the structural unit derived from the (meth)acrylic monomer (A1). The structural unit is derived from a monomer (A2) copolymerizable with the (meth)acrylic monomer (A1). The (meth)acrylic polymer (A) may contain one or more types of such structural units.

[0036] An example of the monomer (A2) is an aromatic ring-containing monomer. The aromatic ring-containing monomer may be an aromatic ring-containing (meth)acrylic monomer. Examples of the aromatic ring-containing monomer include phenyl(meth)acrylate, phenoxyethyl(meth)acrylate, benzyl(meth)acrylate, phenoxydiethylene glycol(meth)acrylate, ethylene oxide-modified nonylphenol(meth)acrylate, hydroxyethylated β-naphthol(meth)acrylate, and biphenyl(meth)acrylate. The content of the structural unit derived from the aromatic ring-containing monomer in the (meth)acrylic polymer (A) is, for example, 0 to 50% by weight, and may be 1 to 30% by weight, 5 to 25% by weight, 8 to 20% by weight, 10 to 18% by weight, 11 to 17% by weight, or even 12 to 16% by weight. The fact that the (meth)acrylic polymer (A) has a structural unit derived from an aromatic ring-containing monomer means that the (meth)acrylic polymer (A) and This can contribute to improving the compatibility with the crosslinking agent (B) and its self-polymer.

[0037] Another example of the monomer (A2) is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth)acrylic monomer. Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group can react with various crosslinking agents. From the viewpoint of increasing the uniformity of the crosslinked structure to be formed, the content of the structural unit derived from the hydroxyl group-containing monomer in the (meth)acrylic polymer (A) may be 1% by weight or less, 0.5% by weight or less, or even 0.1% by weight or less, or may even be 0% by weight (no such structural unit may be contained).

[0038] Monomer (A2) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Examples of the carboxyl group-containing monomer are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the amino group-containing monomer are N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of the amide group-containing monomer include acrylamide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam-based monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. The (meth)acrylic polymer (A) containing a structural unit derived from a carboxyl group-containing monomer, particularly acrylic acid, can enhance the self-polymerization of the isocyanate-based crosslinking agent (B), for example. Improved self-polymerization of the crosslinking agent (B) can contribute to suppressing peeling of the pressure-sensitive adhesive sheet, particularly in humid environments, and stabilizing the physical properties of the pressure-sensitive adhesive sheet in systems with a high content of the crosslinking agent (B).

[0039] Monomer (A2) may be a polyfunctional monomer. Examples of polyfunctional monomers include polyfunctional acrylates such as hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; and divinylbenzene. The polyfunctional acrylate is preferably 1,6-hexanediol diacrylate or dipentaerythritol hexa(meth)acrylate.

[0040] The total content of the structural units derived from the carboxyl group-containing monomer, the amino group-containing monomer, the amide group-containing monomer, and the polyfunctional monomer in the (meth)acrylic polymer (A) is It is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 8% by weight or less. When the (meth)acrylic polymer (A) has such structural units, the total content is, for example, 0.01% by weight or more, and may be 0.05% by weight or more. The (meth)acrylic polymer (A) does not need to contain structural units derived from polyfunctional monomers.

[0041] Examples of other monomers (A2) include (meth)acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate; epoxy group-containing monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; vinyl sulfonate; (meth)acrylic acid esters having an alicyclic hydrocarbon group, such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; vinyl esters, such as vinyl acetate and vinyl propionate; aromatic vinyl compounds, such as styrene and vinyl toluene; olefins or dienes, such as ethylene, propylene, butadiene, isoprene, and isobutylene; vinyl ethers, such as vinyl alkyl ether; and vinyl chloride.

[0042] The total content of the structural units derived from the other monomers (A2) in the (meth)acrylic polymer (A) is, for example, 30% by weight or less, may be 10% by weight or less, and is preferably 0% by weight (not including such structural units).

[0043] The (meth)acrylic polymer (A) can be formed by polymerizing one or more of the above-mentioned monomers by a known method. A monomer and a partial polymer of the monomer may also be polymerized. The polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy ray polymerization. Solution polymerization and active energy ray polymerization are preferred because they allow the formation of a pressure-sensitive adhesive sheet with excellent optical transparency. The polymerization is preferably carried out while avoiding contact between the monomer and / or the partial polymer and oxygen. For this purpose, for example, polymerization in an inert gas atmosphere such as nitrogen, or polymerization in a state where oxygen is blocked by a resin film or the like, can be employed. The (meth)acrylic polymer (A) formed may be in any form, such as a random copolymer, a block copolymer, or a graft copolymer.

[0044] The polymerization system for forming the (meth)acrylic polymer (A) may contain one or more polymerization initiators. The type of polymerization initiator can be selected depending on the polymerization reaction, and may be, for example, a thermal polymerization initiator or a photopolymerization initiator.

[0045] Examples of solvents used in solution polymerization include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. However, the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.

[0046] The polymerization initiator used in the solution polymerization is, for example, an azo-based polymerization initiator, a peroxide-based polymerization initiator, or a redox-based polymerization initiator. Examples of peroxide-based polymerization initiators include dibenzoyl peroxide and t-butyl permaleate. Among these, the azo-based polymerization initiator disclosed in JP-A-2002-69411 is preferred. Examples of the azo-based polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate) dimethyl, and 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the above examples. The azo-based polymerization initiator The amount of the polymerization initiator used is, for example, 0.05 to 0.5 parts by weight, and may be 0.1 to 0.3 parts by weight, relative to 100 parts by weight of the total amount of the monomers.

[0047] The active energy rays used in the active energy ray polymerization include, for example, ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams, as well as ultraviolet rays. The active energy ray is preferably ultraviolet rays. Polymerization by irradiation with ultraviolet rays is also called photopolymerization. The polymerization system for the active energy ray polymerization typically contains a photopolymerization initiator. The polymerization conditions for the active energy polymerization are not limited as long as a (meth)acrylic polymer (A) is formed.

[0048] Examples of the photopolymerization initiator include a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator, although the photopolymerization initiator is not limited to the above examples.

[0049] Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. An example of a photoactive oxime-based photopolymerization initiator is 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. An example of a benzoin-based photopolymerization initiator is benzoin. An example of a benzyl-based photopolymerization initiator is benzil. An example of a benzophenone-based photopolymerization initiator is benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, or α-hydroxycyclohexyl phenyl ketone. An example of a ketal-based photopolymerization initiator is benzil dimethyl ketal. An example of a thioxanthone-based photopolymerization initiator is thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, or dodecylthioxanthone.

[0050] The amount of the photopolymerization initiator used is, for example, 0.01 to 1 part by weight, and may be 0.05 to 0.5 parts by weight, relative to 100 parts by weight of the total amount of the monomers.

[0051] The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is, for example, 1,000,000 to 2,800,000, and from the viewpoint of the durability and heat resistance of the PSA sheet, may be 1,200,000 or more, or even 1,400,000 or more. The weight average molecular weight (Mw) of the polymer and oligomer in this specification is a value (polystyrene equivalent) based on measurement by GPC (gel permeation chromatography).

[0052] The content of the (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition (I) is, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, or even 80% by weight or more, in terms of solid content. The upper limit of the content is, for example, 99% by weight or less, 97% by weight or less, 95% by weight or less, 93% by weight or less, or even 90% by weight or less.

[0053] (Isocyanate-based crosslinking agent (B)) The isocyanate-based crosslinking agent (B) is a type of additive for the pressure-sensitive adhesive composition. The crosslinking agent (B) contains an isocyanate group as a crosslinking reactive group. The crosslinking agent (B) is typically a polyfunctional crosslinking agent having two or more crosslinking reactive groups per molecule. The crosslinking agent (B) may also be a trifunctional or higher crosslinking agent having three or more crosslinking reactive groups per molecule. The upper limit of the number of crosslinking reactive groups per molecule is, for example, five.

[0054] The isocyanate-based crosslinking agent (B) may be an aromatic isocyanate compound, an alicyclic isocyanate compound, or an aliphatic isocyanate compound.

[0055] Examples of aromatic isocyanate compounds that can be used in the crosslinking agent (B) include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0056] Examples of the alicyclic isocyanate compound that can be used in the crosslinking agent (B) include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0057] Examples of aliphatic isocyanate compounds that can be used in the crosslinking agent (B) are trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0058] The crosslinking agent (B) may be a derivative of the isocyanate compound. Examples of the derivative include multimers (dimers, trimers, pentamers, etc.), adducts obtained by addition to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, allophanate-modified products, isocyanurate-modified products, carbodiimide-modified products, and urethane prepolymers obtained by addition to polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0059] The crosslinking agent (B) is preferably an aromatic isocyanate compound or a derivative thereof, more preferably tolylene diisocyanate or a derivative thereof (i.e., a tolylene diisocyanate (TDI) crosslinking agent). TDI crosslinking agents have better reaction uniformity than xylylene diisocyanate or a derivative thereof (i.e., a xylylene diisocyanate (XDI) crosslinking agent). An example of a TDI crosslinking agent is an adduct of tolylene diisocyanate and a polyfunctional alcohol, and a more specific example is a trimethylolpropane / tolylene diisocyanate trimer adduct.

[0060] Commercially available products can be used as the crosslinking agent (B). Examples of commercially available products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, and Coronate HX (all manufactured by Tosoh Corporation; all trade names), as well as Takenate D-102, Takenate D-103, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500, and Takenate 600 (all manufactured by Mitsui Chemicals; all trade names). Examples of commercially available products include Coronate L, Takenate D-103, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500, and Takenate 600 (all manufactured by Mitsui Chemicals; all trade names). Takenate D-102 and Takenate D-103 (both of which are trimethylolpropane / tolylene diisocyanate trimer adducts) can be preferably used.

[0061] The amount of the crosslinking agent (B) in the pressure-sensitive adhesive composition (I) may be, for example, 1.5 parts by weight or more, 2 parts by weight or more, or even 2.5 parts by weight or more, relative to 100 parts by weight of the (meth)acrylic polymer (A). The upper limit of the amount may be, for example, 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 12 parts by weight or less, 10 parts by weight or less, 7 parts by weight or less, 5 parts by weight or less, or even 4 parts by weight or less.

[0062] The pressure-sensitive adhesive composition (I) may contain one or more crosslinking agents (B).

[0063] When the PSA sheet 1 is formed from a PSA composition containing a crosslinking agent (B), the first domain and / or the second domain may contain a polymer of the crosslinking agent (B). An example of the polymer is a self-polymer of the crosslinking agent (B).

[0064] Assuming a self-polymer (C) of the isocyanate-based crosslinking agent (B), the Hansen solubility parameter (HSP) distance Ra between the (meth)acrylic polymer (A) and the self-polymer (C) may be 15 or less. Heat generated during the formation of the pressure-sensitive adhesive sheet 1 can cause the isocyanate-based crosslinking agents (B) to react with each other, forming a self-polymer of the crosslinking agent (B). The formation of the self-polymer increases the cohesive strength of the pressure-sensitive adhesive sheet, thereby contributing to the formation of a pressure-sensitive adhesive sheet that can suppress dimensional changes in the optical film. However, if the compatibility between the (meth)acrylic polymer (A) and the self-polymer is low, it is thought that independent domains rich in the self-polymer are more likely to form within the pressure-sensitive adhesive sheet. According to the inventors' investigations, a distance Ra of 15 or less can contribute to the formation of the first domain and / or second domain in the above-described state.

[0065] The distance Ra may be 14.5 or less, 14 or less, 13.5 or less, 13 or less, 12.5 or less, or even 12 or less. The lower limit of the distance Ra is, for example, 6 or more.

[0066] The Hansen solubility parameter (HSP) is a solubility parameter introduced by Hildebrand, divided into three components: the dispersion term δD, the polarization term δP, and the hydrogen bonding term δH. δD represents the energy derived from the dispersion force between molecules. δP represents the energy derived from the polar force between molecules. δH represents the energy derived from the hydrogen bonding force between molecules. The units of each component are usually MPa. 1 / 2 The above three components give the Hansen equation A point (vector) in three-dimensional space known as the distance Ra is determined. The distance Ra is the distance between the point (D A , P A , H A ) and self-weight The point (D) corresponding to the union (C) C , P C , H C ) and is the distance between the A -δD B ) 2 +(δP A -δP B ) 2 +(δH A -δH B ) 2} 1 / 2 The details of the Hansen solubility parameters are disclosed in "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)". The δD, δP and δH of a polymer can be calculated using, for example, HSPiP (version Using known software such as 5), the solubility parameters can be calculated based on the structural units of the polymer and the content of those units in the polymer. More specifically, the δD, δP, and δH of each structural unit are calculated individually, and the weighted average values obtained by weighting the calculated δD, δP, and δH by the content of those units can be used as the δD, δP, and δH of the polymer. The calculations are performed at a temperature of 23°C. The calculated values of δD, δP, and δH may vary slightly depending on the software used. However, these differences are usually negligible when calculating Ra. The Hansen solubility parameter for crosslinking agents is calculated only for those that form self-polymers.

[0067] The self-polymer (C) assumed in the calculation of the distance Ra is an isocyanate-based crosslinking agent (B However, the self-polymer of the crosslinking agent (B) actually contained in the PSA sheet formed from the PSA composition (I) may contain structural units other than those derived from the crosslinking agent (B).

[0068] ((Meth)acrylic oligomer) The pressure-sensitive adhesive composition (I) may further contain a (meth)acrylic oligomer (D).

[0069] The (meth)acrylic oligomer (D) may have the same composition as the above-mentioned (meth)acrylic polymer (A) except for the weight-average molecular weight (Mw). The weight-average molecular weight (Mw) of the (meth)acrylic oligomer (D) may be, for example, 1,000 or more, 2,000 or more, 3,000 or more, or even 4,000 or more. The upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic oligomer may be, for example, 30,000 or less, 15,000 or less, 10,000 or less, or even 7,000 or less.

[0070] The (meth)acrylic oligomer (D) has, for example, one or more structural units derived from the following monomers: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, alkyl (meth)acrylates such as methyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols.

[0071] The (meth)acrylic oligomer (D) preferably has a structural unit derived from a (meth)acrylic monomer having a relatively bulky structure. In this case, the adhesiveness of the pressure-sensitive adhesive sheet can be further improved. Examples of such acrylic monomers include alkyl (meth)acrylates having an alkyl group with a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; and aromatic ring-containing (meth)acrylates, such as phenyl (meth)acrylate and benzyl (meth)acrylate. The monomer preferably has a cyclic structure, and more preferably has two or more cyclic structures. Furthermore, when ultraviolet irradiation is carried out during polymerization of the (meth)acrylic oligomer (D) and / or during formation of the pressure-sensitive adhesive sheet, it is preferable that the above-mentioned monomer does not have an unsaturated bond, since this makes it less likely that the progress of polymerization and / or formation will be inhibited. For example, an alkyl (meth)acrylate having an alkyl group with a branched structure, or an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

[0072] Specific examples of the (meth)acrylic oligomer (D) include a copolymer of butyl acrylate, methyl acrylate, and acrylic acid, a copolymer of cyclohexyl methacrylate and isobutyl methacrylate, a copolymer of cyclohexyl methacrylate and isobornyl methacrylate, a copolymer of cyclohexyl methacrylate and acryloylmorpholine, a copolymer of cyclohexyl methacrylate and diethylacrylamide, and a copolymer of 1-adamantyl acrylamide. copolymers of dicyclopentanyl methacrylate and isobornyl methacrylate; copolymers of dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, copolymers of methyl methacrylate and at least one selected from isobornyl acrylate and cyclopentanyl methacrylate; homopolymers of dicyclopentanyl acrylate; homopolymers of 1-adamantyl methacrylate; and homopolymers of 1-adamantyl acrylate.

[0073] For the polymerization of the (meth)acrylic oligomer (D), the above-mentioned polymerization method for the (meth)acrylic polymer (A) can be used.

[0074] When the pressure-sensitive adhesive composition (I) contains the (meth)acrylic oligomer (D), the blending amount thereof may be, for example, 70 parts by weight or less, 50 parts by weight or less, or even 40 parts by weight or less, per 100 parts by weight of the (meth)acrylic polymer (A). The lower limit of the blending amount may be, for example, 1 part by weight or more, 2 parts by weight or more, or even 3 parts by weight or more, per 100 parts by weight of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition (I) does not necessarily contain the (meth)acrylic oligomer (D).

[0075] (additives) The pressure-sensitive adhesive composition (I) may contain other additives. Examples of the additives include crosslinkers other than the isocyanate-based crosslinker (B), silane coupling agents, colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, rework improvers, softeners, antioxidants, antiaging agents, light stabilizers, UV absorbers, polymerization inhibitors, antistatic agents (such as alkali metal salts, ionic liquids, and ionic solids, which are ionic compounds), inorganic fillers, organic fillers, powders such as metal powders, particles, and foil-like materials. The additives include (meth)acrylic polymers (A). For example, it can be blended in an amount of 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 1 part by weight or less, per 100 parts by weight of the inorganic filler.

[0076] Examples of crosslinking agents other than the isocyanate-based crosslinking agent (B) include peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and polyfunctional metal chelates. When the pressure-sensitive adhesive composition (I) contains a crosslinking agent other than the isocyanate-based crosslinking agent (B), the total amount of the crosslinking agent is preferably 0.1 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, and 0.1 to 1 part by weight, in that order. The pressure-sensitive adhesive composition (I) may not contain a crosslinking agent other than the isocyanate-based crosslinking agent (B), such as an epoxy-based crosslinking agent.

[0077] Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0078] When the pressure-sensitive adhesive composition (I) contains a silane coupling agent, the blending amount thereof is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.2 parts by weight or less, 0.1 parts by weight or less, or even 0.05 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition (I) does not contain a silane coupling agent. It's okay.

[0079] The pressure-sensitive adhesive composition (I) may be, for example, an emulsion type, a solvent type (solution type), an active energy ray curable type (photocurable type), or a hot melt type (hot melt type). From the viewpoint of forming a pressure-sensitive adhesive sheet with superior durability, the pressure-sensitive adhesive composition (I) may be a solvent type. The solvent-type pressure-sensitive adhesive composition (I) may not contain a photocuring agent such as an ultraviolet curing agent.

[0080] The pressure-sensitive adhesive sheet 1 can be used, for example, for optical applications. The pressure-sensitive adhesive sheet 1 may be used in an optical laminate and / or an image display device. The pressure-sensitive adhesive sheet 1 is suitable for use in image displays in which suppression of dimensional changes in the optical film is particularly required, such as image displays with narrow frames or image displays with relatively large screen sizes. Use in these image displays, for example, suppresses peeling of the film included in the optical laminate.

[0081] [Manufacturing method of adhesive sheet] The adhesive sheet 1 can be formed, for example, by the manufacturing method of this embodiment described below, although the adhesive sheet 1 may also be formed by other manufacturing methods.

[0082] The manufacturing method of this embodiment includes heating a coating film of a pressure-sensitive adhesive composition (I) containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate-based crosslinking agent (B) to form a pressure-sensitive adhesive sheet 1 from the coating film. Hereinafter, the heating of the coating film is referred to as main heating (main heating). During this heating, thermal crosslinking and curing of the pressure-sensitive adhesive composition (I) contained in the coating film mainly proceeds.

[0083] The conditions for the main heating satisfy the following formula (1) or (2). Here, x and y are the heating temperature (°C) and time (seconds), respectively, for the main heating. Formula (2) means that if the heating temperature x exceeds 120°C, the heating time y should be limited to a predetermined time. The heating temperature x can be determined as the highest temperature to which the coating film is exposed, for example, as the set temperature of a heating device such as a heating oven used to heat the coating film (if the heating device has multiple zones with different set temperatures or if the set temperature changes over time, it can be determined as the highest set temperature to which the coating film is exposed in the heating device). The heating time y can be determined as the time the coating film is exposed to a temperature exceeding 120°C. When a heating device is used, the time y can be determined, for example, as the time the coating film is located in a space set at a temperature exceeding 120°C or the time the coating film passes through a zone set at a temperature exceeding 120°C. If there are multiple zones set at a temperature exceeding 120°C, the total time passing through those zones can be determined as time y. If the set temperature changes over time, the time during which the set temperature exceeds 120° C. can be calculated as time y. The same applies to the temperature p and time q of preheating, which will be described later. x≦120 (1) x>120 and y≦-2.17x+365.83 (2)

[0084] According to the inventors' investigations, the solubility of the isocyanate-based crosslinking agent (B) in a monomeric state deteriorates at high temperatures, and it tends to gradually aggregate within the coating film. Therefore, as the temperature x increases and the time y increases, the independent domains described above tend to be more easily formed in the PSA sheet, and the size and density of the domains formed tend to increase. On the other hand, when the temperature x drops below a certain level, the formation of oligomers such as dimers and trimers due to self-polymerization of the crosslinking agent (B) proceeds preferentially, suppressing aggregation. Main heating under conditions satisfying the above formula (1) or (2) is suitable for suppressing aggregation of the crosslinking agent (B).

[0085] The lower limit of the temperature x is, for example, 80°C or higher, and may be 85°C or higher, or even 90°C or higher. The upper limit of the temperature x is, for example, 165°C or lower, and may be 160°C or lower. The upper limit of the temperature x under the condition satisfying 1) may be 115° C. or less, 110° C. or less, 105° C. or less, 100° C. or less, 95° C. or less, or even 90° C. or less. The temperature x of the main heating may be kept constant throughout the main heating or may be changed during the main heating.

[0086] The lower limit of the time y is, for example, 10 seconds or more, and may be 20 seconds or more, 30 seconds or more, 35 seconds or more, 40 seconds or more, more than 40 seconds, 45 seconds or more, or even 50 seconds or more. The upper limit of the time y is, for example, 300 seconds or less, 180 seconds or less, or even less than 180 seconds. The upper limit of the time y under the condition satisfying formula (2) may be 100 seconds or less, 95 seconds or less, 90 seconds or less, 85 seconds or less, 80 seconds or less, 75 seconds or less, 70 seconds or less, 65 seconds or less, or even 60 seconds or less.

[0087] The conditions for this heating may satisfy the formula: y≦−2.17x+345.83 where x>120. In heating that satisfies the above formula, the time y is more limited than in heating that satisfies formula (2).

[0088] The conditions for the main heating may be such that x>120, y≦80, or even y≦60.

[0089] The conditions for this heating may be x≦120, y<180, or may be y≦160, y≦140, y≦120, y≦110, y≦100, y<100, y≦95, or even y≦90.

[0090] The manufacturing method of this embodiment may further include preheating the coating film of the pressure-sensitive adhesive composition (I) under heating conditions of a temperature p (°C) and a time q (seconds) before subjecting the coating film to main heating. The preheating temperature p is lower than the main heating temperature x. The preheating mainly involves drying the coating film, and in the case of a solvent-based pressure-sensitive adhesive composition (I), removing the solvent. The removal of the solvent can contribute to suppressing aggregation of the isocyanate-based crosslinking agent (B). Furthermore, preheating can contribute to promoting a reaction with a hydroxyl group-containing compound, typically water, to some extent to produce an oligomer of the crosslinking agent (B) while suppressing melting of the isocyanate-based crosslinking agent (B).

[0091] The main heating temperature x (°C) and the preheating temperature p (°C) may satisfy the formula: xp≦55. xp may be 50°C or less, 45°C or less, 40°C or less, 35°C or less, 30°C or less, less than 30°C, 25°C or less, 20°C or less, 15°C or less, or even 10°C or less. The lower limit of xp may be greater than 0°C, 5°C or more, or even 10°C or more. A small difference between temperature x and temperature p can contribute to suppressing shrinkage of the coated film caused by a sudden change in temperature.

[0092] The temperature p is, for example, 50°C or higher and lower than 80°C. The lower limit of the temperature p may be 55°C or higher, 60°C or higher, 65°C or higher, or even 70°C or higher. The upper limit of the temperature p may be 75°C or lower. The preheating temperature p may be maintained constant throughout the preheating or may be changed during the preheating.

[0093] The time q is, for example, 5 seconds or more, and may be 10 seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds or more, 30 seconds or more, 35 seconds or more, 40 seconds or more, or even 45 seconds or more. The upper limit of the time q is, for example, 180 seconds or less, and may be 120 seconds or less, 115 seconds or less, or even 110 seconds or less.

[0094] When the pressure-sensitive adhesive composition (I) is a solvent-based adhesive, the time q is set to a time when the solvent contained in the coating film is 30% or less, preferably 25% or less, more preferably 20% or less, of the content before preheating. The content may be set to the following amount.

[0095] The time q may be expressed as q / (q+y), which is the ratio of the preheating time to the total time of the preheating and main heating time, and may satisfy the relationship 0.2≦q / (q+y)≦0.6. The lower limit of q / (q+y) may be 0.25 or more, or even 0.3 or more. The upper limit of q / (q+y) may be 0.55 or less, 0.5 or less, 0.45 or less, or even 0.4 or less.

[0096] Preheating may be performed after a predetermined time r has elapsed since the formation of the coating film. Ensuring time r between the formation of the coating film and the start of preheating can contribute to efficient removal of the solvent contained in the coating film. Time r is, for example, 5 to 180 seconds, or may be 5 to 120 seconds or 10 to 60 seconds. During time r, the coating film is in an unheated atmosphere, for example, in an atmosphere of 20 to 30°C.

[0097] Preheating and main heating may be performed continuously. As a more specific example, one heating device may be divided into a preheating section and a main heating section, and the temperatures x and p of each section may be set independently, and the coating film may be continuously transported from the preheating section to the main heating section.

[0098] The coating film to be heated can be formed, for example, by applying the pressure-sensitive adhesive composition (I) or a mixture of the pressure-sensitive adhesive composition (I) and a solvent to a substrate film. The substrate film is typically a resin film or a metal film. The substrate film may be a film (release film) whose coating surface has been subjected to a release treatment. In one example of a release film, the coating surface has been subjected to a release treatment with a silicone compound. The substrate film may also be an optical film, in which case an optical laminate containing a pressure-sensitive adhesive sheet and an optical film can be formed.

[0099] The coating onto the substrate film can be carried out by a known method, such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, or extrusion coating using a die coater.

[0100] Compositions and mixtures that are applied to substrate films preferably have a viscosity that is suitable for handling and application.

[0101] [Optical laminate] An example of the optical laminate of this embodiment is shown in Fig. 2. The optical laminate 10A in Fig. 2 includes an adhesive sheet 1 and an optical film 2. The adhesive sheet 1 and the optical film 2 are laminated together. The optical laminate 10A can be used as an optical film with an adhesive sheet.

[0102] Examples of the optical film 2 include a polarizing plate, a retardation film, and a laminated film including a polarizing plate and / or a retardation film. However, the optical film 2 is not limited to the above examples. The optical film 2 may also include a glass film.

[0103] The polarizing plate includes a polarizer. A polarizer protective film may be bonded to at least one surface of the polarizer. Any pressure-sensitive adhesive or adhesive may be used to bond the polarizer and the polarizer protective film. An adhesive sheet 1 may be used for bonding. The polarizer is typically a polyvinyl alcohol (PVA) film in which iodine has been oriented by stretching, such as in-air stretching (dry stretching) or stretching in boric acid water.

[0104] The retardation film is a film having birefringence in the in-plane direction and / or the thickness direction. The retardation film is, for example, a stretched resin film, a film in which a liquid crystal material is oriented and fixed, or the like. It is a film.

[0105] The retardation film may be a λ / 4 plate, a λ / 2 plate, an anti-reflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of JP 2012-133303 A), a viewing angle compensation retardation film (see, for example, paragraphs 0225 and 0226 of JP 2012-133303 A), or an obliquely oriented viewing angle compensation retardation film (see, for example, paragraph 0227 of JP 2012-133303 A). The retardation film is not limited to the above examples, as long as it has birefringence in the in-plane direction and / or the thickness direction. The retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is single-layer or multi-layer, and the like are also not limited. Known films can be used as the retardation film.

[0106] The thickness of the optical film 2 is, for example, 1 to 200 μm. The thickness of the optical film 2, which is a polarizing plate, is, for example, 1 to 150 μm, and may be 100 μm or less, 75 μm or less, 50 μm or less, 20 μm or less, or even 15 μm or less. The lower limit of the thickness may be 10 μm or more, 20 μm or more, 50 μm or more, 75 μm or more, or even 100 μm or more.

[0107] The optical film 2 may be a single layer or a laminated film composed of two or more layers. When the optical film 2 is a laminated film, the pressure-sensitive adhesive sheet 1 may be used to bond the layers together.

[0108] Another example of the optical laminate of the present embodiment is shown in Fig. 3. The optical laminate 10B in Fig. 3 has a laminated structure in which a separator 3, a pressure-sensitive adhesive sheet 1, and an optical film 2 are laminated in this order. By peeling off the separator 3, the optical laminate 10B can be used as an optical film with a pressure-sensitive adhesive sheet.

[0109] The separator 3 is typically a resin film. Examples of resins that can be used to form the separator 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the separator 3 that comes into contact with the pressure-sensitive adhesive sheet 1 may be subjected to a release treatment. The release treatment may be, for example, a treatment using a silicone compound. However, the separator 3 is not limited to the above examples. The separator 3 is peeled off when the optical laminate 10B is used, for example, when it is attached to the image-forming layer.

[0110] Another example of the optical laminate of this embodiment is shown in Fig. 4. The optical laminate 10C in Fig. 4 has a laminated structure in which a separator 3, a pressure-sensitive adhesive sheet 1, a retardation film 2A, an interlayer pressure-sensitive adhesive 4, and a polarizing plate 2B are laminated in this order. After peeling off the separator 3, the optical laminate 10C can be used by being attached to, for example, an image-forming layer.

[0111] A known adhesive can be used for the interlayer adhesive 4. The adhesive sheet 1 may be used as the interlayer adhesive 4.

[0112] Another example of the optical laminate of this embodiment is shown in Fig. 5. The optical laminate 10D in Fig. 5 has a laminated structure in which a separator 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B, and a protective film 5 are laminated in this order. After peeling off the separator 3, the optical laminate 10D can be used by being attached to, for example, an image forming layer.

[0113] The protective film 5 has a function of protecting the optical film 2 (polarizing plate 2B) which is the outermost layer during distribution and storage of the optical laminate 10D and when the optical laminate 10D is incorporated into an image display device. Furthermore, the protective film 5 may function as a window to the external space when incorporated into an image display device. The protective film 5 is typically It is a resin film. The resin constituting the protective film 5 is, for example, polyester such as PET, polyolefin such as polyethylene and polypropylene, acrylic, cycloolefin, polyimide, or polyamide, with polyester being preferred. However, the protective film 5 is not limited to the above examples. The protective film 5 may be a glass film or a laminated film including a glass film. The protective film 5 may be subjected to surface treatment such as anti-glare, anti-reflection, or anti-static.

[0114] The protective film 5 may be bonded to the optical film 2 with any adhesive. Bonding with an adhesive sheet 1 is also possible.

[0115] The optical laminate may have any configuration as long as it includes a pressure-sensitive adhesive sheet formed by the above-described method for producing a pressure-sensitive adhesive sheet.

[0116] The optical laminate of this embodiment can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate, or as a sheet-shaped optical laminate.

[0117] The optical laminate of this embodiment is typically used in image display devices, such as liquid crystal displays, organic EL displays, and inorganic EL displays.

[0118] [Image display device] An example of an image display device of this embodiment is shown in Fig. 6. The image display device 11 in Fig. 6 has a laminated structure in which a substrate 7, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B, and a protective film 5 are laminated in this order. The image display device 11 has the optical laminates 10A, 10B, 10C, and 10D shown in Figs. 2 to 5 (excluding the separator 3). The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices.

[0119] The image display device 11 in Fig. 6 may be an organic EL display or a liquid crystal display. However, the image display device 11 is not limited to this example. The image display device 11 may also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 11 may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0120] The image display device may have any configuration as long as it includes a pressure-sensitive adhesive sheet formed by the above-described method for producing a pressure-sensitive adhesive sheet and / or an optical laminate formed by the above-described method for producing an optical laminate. [Example]

[0121] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0122] First, the evaluation methods for the (meth)acrylic polymers and pressure-sensitive adhesive sheets produced in the examples and comparative examples will be described.

[0123] [Weight average molecular weight (Mw)] The weight average molecular weight (Mw) of the (meth)acrylic polymer was evaluated by GPC under the following conditions. Analytical equipment: Waters, Acquity APC Column: Tosoh G7000HXL+GMHXL+GMHXL Column temperature: 40℃ Eluent: tetrahydrofuran (acid added) ·Flow rate: 0.8mL / min ·Injection volume: 100μL Detector: Differential refractometer (RI) Standard sample: Agilent, polystyrene (PS)

[0124] [Distance Ra] The distance Ra was calculated using the method described above. The software used was HSPiP (version 5 ) was used.

[0125] [Storage modulus G' (25℃)] The storage modulus G' (25°C) of the PSA sheet was evaluated using the method described above. However, the measurement sample was prepared by punching out a disc from a laminate obtained by stacking the manufactured PSA sheets. The dynamic viscoelasticity of the measurement sample was measured using an ARES-G2 manufactured by TA Instruments.

[0126] [Whitening] The degree of whitening of the pressure-sensitive adhesive sheet was evaluated as follows based on the haze measurement of the pressure-sensitive adhesive sheet. The smaller the haze, the smaller the degree of whitening. The haze of the pressure-sensitive adhesive sheet was measured in an atmosphere of 25°C using a haze meter HZ-V3 manufactured by Suga Test Instruments in accordance with JIS K7136:1981. The measurement was carried out on a slide glass S012140 (thickness 1.3 mm) manufactured by Matsunami Glass Industry Co., Ltd., with the pressure-sensitive adhesive sheet to be evaluated laminated in five layers (adhesive sheet thickness 15 μm) or three layers (adhesive sheet thickness 25 μm) (total thickness of 75 μm in both cases). For the pressure-sensitive adhesive sheet of Example 21, which had a thickness of 35 μm, the measured value V when two layers were laminated (total thickness 70 μm) was converted to a value equivalent to a total thickness of 75 μm using the formula: V × 75 / 70. A: Measured haze is less than 0.37% B: Measured haze is 0.37% or more and less than 0.43% C: Measured haze is 0.43% or more and less than 0.50% D: Measured haze is 0.50% or more

[0127] [Domain Status] The state of the domains of the pressure-sensitive adhesive sheet was evaluated by the above-mentioned evaluation method for a cross-sectional image of the pressure-sensitive adhesive sheet. The cross-sectional image was obtained using a TEM (HT7820, manufactured by Hitachi, Ltd.; acceleration voltage 100 kV) at a magnification of 20,000 times. The sample to be subjected to TEM was prepared by subjecting the pressure-sensitive adhesive sheet to evaluation to a heavy metal staining treatment using RuO4, then embedding the sheet in resin, and then subjecting it to an ultra-violet light. The specimen was prepared by cutting out a section approximately 100 nm thick using thin sectioning. Ten evaluation areas were set on the cross-sectional image so that they did not overlap with each other. The state was evaluated by image analysis of the cross-sectional image, and ImageJ was used for image analysis. The states of the evaluated domains, 1 to 5, and the evaluation criteria for each state are as follows:

[0128] (State 1: Number of evaluation areas where the first domain exists) A: Number of evaluation areas is 0 B: Number of evaluation areas: 1-2 C: Number of evaluation areas: 3-5 D: Number of evaluation areas is 6 or more

[0129] (State 2: For all first domains, the shortest distance between the first domains and the adjacent first domains ) A: The shortest distance is 300 nm or more D: The shortest distance is less than 300 nm

[0130] (State 3: For all second domains, the shortest distance between adjacent second domains) A: The shortest distance is 200 nm or more C: The shortest distance is 150 nm or more and less than 200 nm D: The shortest distance is less than 150 nm

[0131] (State 4: Number of evaluation areas with 10 or fewer second domains) A: Number of evaluation areas is 3 or more D: Number of evaluation areas: 1-2

[0132] (State 5: Percentage of all second domains in which the shortest distance between adjacent second domains is 100 nm or more) A: 50% or more D: Less than 50%

[0133] [Humidity durability] The humidity durability (corresponding to an accelerated durability test) of the pressure-sensitive adhesive sheet was evaluated using the following method. First, a circularly polarizing plate with a pressure-sensitive adhesive sheet was formed, with one exposed surface of each of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples. Next, the circularly polarizing plate was fixed to the surface of a glass plate (Corning Eagle XG) via the pressure-sensitive adhesive sheet. The circularly polarizing plate was fixed in an atmosphere of 23°C and 50% RH. Next, the plate was treated in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes, and then left to cool to 23°C to stabilize the bonding of the circularly polarizing plate to the glass plate. After that, the plate was left in a heated and humidified atmosphere at 60°C and 95% RH for 500 hours. After leaving the plate, the atmosphere was returned to 23°C and 50% RH, and the presence of peeling of the circularly polarizing plate from the glass plate and the formation of bubbles between the glass plate and the circularly polarizing plate were visually confirmed, and the humidity durability was evaluated as follows. A: No changes in appearance such as foaming or peeling are observed. B: A small amount of isolated peeling or bubbling was observed at the edge, but this was within the range that would not cause any problems in practical use. C: Slight continuous peeling or bubbling is observed at the edge, but is within a range that does not cause any practical problems. D: Significant peeling or bubbling is observed at the edge, and there is a problem in practical use.

[0134] The method for forming the circularly polarizing plate with the adhesive sheet used for evaluating the humidity durability is described below.

[0135] <Preparation of Polarizing Plate P1> (Fabrication of polarizer) A long polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000", thickness 30 μm) was uniaxially stretched in the longitudinal direction (total stretching ratio 5.9 times) using a roll stretching machine. At the same time, the resin film was subjected to the following treatments in order: swelling, dyeing, crosslinking, washing, and drying. A 12 μm-thick polarizer was produced. In the swelling treatment, the resin film was stretched 2.2 times while being treated with pure water at 20°C. In the dyeing treatment, the resin film was stretched 1.4 times while being treated with an aqueous solution at 30°C containing iodine and potassium iodide in a weight ratio of 1:7. The iodine concentration in the aqueous solution was adjusted so that the single transmittance of the produced polarizer would be 45.0%. A two-stage crosslinking treatment was used. In the first stage of the crosslinking treatment, the resin film was stretched 1.2 times while being treated with an aqueous solution at 40°C containing boric acid and potassium iodide. The content of boric acid in the aqueous solution used in the first cross-linking treatment was 5 The content of boric acid in the aqueous solution used in the second crosslinking treatment was 4.3 wt %, and the content of potassium iodide was 3.0 wt %. In the second crosslinking treatment, the resin film was stretched 1.6 times while being treated with a 65°C aqueous solution containing dissolved boric acid and potassium iodide. The content of boric acid in the aqueous solution used in the second crosslinking treatment was 4.3 wt %, and the content of potassium iodide was 5.0 wt %. In the washing treatment, an aqueous potassium iodide solution at 20°C was used. The content of potassium iodide in the aqueous solution used in the washing treatment was 2.6 wt %. The drying treatment was carried out at 70°C for 5 minutes.

[0136] (Preparation of polarizing plate P1) A triacetyl cellulose (TAC) film (Konica Minolta, product name "KC2UA", thickness 25 μm) was attached to each main surface of the prepared polarizer using a polyvinyl alcohol adhesive. However, the TAC film attached to one main surface had a hard coat (thickness 7 μm) formed on the main surface opposite the polarizer side. In this way, a polarizing plate P1 having a configuration of protective layer with hard coat / polarizer / protective layer (without hard coat) was obtained.

[0137] <Preparation of Retardation Film R1> (Preparation of First Retardation Film) 26.2 parts by weight of isosorbide (ISB), 100.5 parts by weight of 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF), 10.7 parts by weight of 1,4-cyclohexanedimethanol (1,4-CHDM), 105.1 parts by weight of diphenyl carbonate (DPC), and 0.591 parts by weight of cesium carbonate (0.2 wt % aqueous solution) as a catalyst were charged into a reaction vessel and dissolved under a nitrogen atmosphere (approximately 15 minutes). The heat transfer temperature in the reaction vessel was set to 150°C, and stirring was performed as necessary. Next, the pressure inside the reaction vessel was reduced to 13.3 kPa, and the heat transfer temperature was increased to 190°C over 1 hour. Phenol evolved as the heat transfer temperature increased was removed from the reaction vessel (the same applies below). Next, the temperature inside the reaction vessel was maintained at 190°C for 15 minutes, after which the pressure inside the reaction vessel was changed to 6.67 kPa and the heat transfer medium temperature was increased to 230°C over 15 minutes. When the stirring torque of the reactor's agitator increased, the heat transfer medium temperature was increased to 250°C over 8 minutes, and the pressure inside the reaction vessel was further reduced to 0.200 kPa or less. After reaching the predetermined stirring torque, the reaction was terminated, and the resulting reaction product was extruded into water and pelletized. In this way, a polycarbonate resin with a composition of BHEPF / ISB / 1,4-CHDM = 47.4 mol% / 37.1 mol% / 15.5 mol% was obtained. The glass transition temperature of the resulting polycarbonate resin was 136.6°C and the reduced viscosity was 0.395 dL / g.

[0138] The prepared polycarbonate resin pellets were vacuum-dried at 80°C for 5 hours, and then a long resin film with a thickness of 120 μm was obtained using a film-forming device equipped with a single-screw extruder (manufactured by Isuzu Chemical Engineering, screw diameter 25 mm, cylinder temperature setting 220°C), a T-die (width 200 mm, temperature setting 220°C), a chill roll (temperature setting 120-130°C), and a winder. Next, the obtained resin film was stretched in the width direction using a tenter stretching machine at a stretching temperature of 137-139°C and a stretch ratio of 2.5 times to obtain a first retardation film.

[0139] (Preparation of second retardation film) A liquid crystal coating solution was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer (weight average molecular weight 5000) represented by the following chemical formula (I) (wherein 65 and 35 represent the mol % of each structural unit), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name "Paliocolor LC242"), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, trade name "Irgacure 907") in 200 parts by weight of cyclopentanone. Next, the prepared liquid crystal coating solution was applied to the surface of a norbornene-based resin film (manufactured by Nippon Zeon, trade name "Zeonex"), which serves as a substrate film, using a bar coater, and then heated and dried at 80°C for 4 minutes to align the liquid crystal contained in the coating film. Next, the coating film was hardened by irradiation with ultraviolet light. A liquid crystal solidified layer (thickness: 0.58 μm) was formed on the substrate film as a second retardation film. The in-plane retardation Re of the liquid crystal solidified layer for light with a wavelength of 550 nm was 0 nm, and the retardation Rth in the thickness direction was -71 nm (nx=1.5326, ny=1.5326, nz=1.6550), and the refractive index characteristic of the liquid crystal solidified layer was nz>nx=ny.

[0140] [ka]

[0141] (Preparation of retardation film R1) One surface of the first retardation film prepared above was attached to the liquid crystal solidified layer of the second retardation film via an adhesive to prepare a retardation film R1.

[0142] <Preparation of a circularly polarizing plate with an adhesive sheet> (Preparation of interlayer adhesive) A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet, and condenser was charged with a monomer mixture containing 79.9 parts by weight of butyl acrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid, and 0.1 parts by weight of 4-hydroxybutyl acrylate. Next, 0.1 parts by weight of 2,2'-azoisobutyronitrile as a polymerization initiator was added to 100 parts by weight of the monomer mixture along with ethyl acetate. Nitrogen gas was introduced into the flask with gentle stirring to replace the atmosphere with nitrogen. The temperature in the flask was maintained at around 55°C, and the polymerization reaction was allowed to proceed for 7 hours. Ethyl acetate was then added to the resulting reaction solution to adjust the solids concentration to 30% by weight, yielding a (meth)acrylic polymer solution for use as an interlayer adhesive. The weight-average molecular weight of the resulting polymer was 2.2 million.

[0143] Next, 0.5 parts by weight of a trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Tosoh, trade name "Coronate L"), 0.1 parts by weight of benzoyl peroxide, a peroxide-based crosslinking agent, 0.2 parts by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403"), and 0.5 parts by weight of a polyether compound having a reactive silyl group (manufactured by Kaneka, Silyl SAT10) were mixed with the resulting (meth)acrylic polymer solution relative to 100 parts by weight of the solids content of the solution to obtain an adhesive composition PSA1 used as an interlayer adhesive for bonding the polarizing plate P1 and the retardation film R1.

[0144] (Preparation of polarizing plate with interlayer adhesive layer) The pressure-sensitive adhesive composition PSA1 prepared above was applied to the release surface of a 38 μm thick polyethylene terephthalate (PET) film (Mitsubishi Chemical Polyester Film, MRF38), a release film whose release surface was silicone-treated, so that the thickness of the layer after drying would be 12 μm, and the coating was dried at 155° C. for 1 minute to form an interlayer pressure-sensitive adhesive layer. Next, the formed interlayer pressure-sensitive adhesive layer was transferred to the protective layer (without hard coat) side of polarizing plate P1 to obtain a polarizing plate with an interlayer pressure-sensitive adhesive layer.

[0145] (Preparation of a circular polarizing plate with an adhesive sheet) Each adhesive sheet prepared in the Examples and Comparative Examples was transferred from the release film to the second retardation film side of the retardation film R1 (the norbornene-based resin film used as the substrate film when preparing the second retardation film was peeled off). Next, the polarizing plate with the interlayer adhesive layer prepared above was attached to the first retardation film side of the retardation film R1 via the interlayer adhesive layer to obtain a circular polarizing plate with an adhesive sheet. The retardation film R1 and the polarizing plate with the interlayer adhesive layer were attached so that the angle between the slow axis of the first retardation film and the absorption axis of the polarizer was 45 degrees counterclockwise when viewed from the side of the first retardation film.

[0146] [Condensation marks (exterior)] After this heating, the surfaces of the release film and the coating film (adhesive sheet) were visually inspected for traces of droplets, and the traces of condensation that may have occurred during the production of the adhesive sheet were evaluated as follows. A: No traces of droplets are visible. B: Slight traces of droplets are visible, but at a level that does not pose a problem in practical use. C: Droplet marks are visible, and there is a problem in practical use.

[0147] [Level of remains] The contents of residual monomer and residual solvent contained in the pressure-sensitive adhesive sheet formed on the release sheet were determined, and the level of residue was evaluated as follows (ppm is based on weight). A: The residual monomer content and the residual solvent content are both below the measurement limit. B: The total content of residual monomers and residual solvents is between the measurement limit and 50 ppm C: The total content of residual monomers and residual solvents is more than 50 ppm and 100 ppm or less D: The total content of residual monomers and residual solvents exceeds 100 ppm

[0148] (Method for measuring residual monomers) Approximately 0.1 g of adhesive sheet was placed in a screw tube, 5 mL of acetone was added, and the mixture was shaken overnight. The contents of the screw tube were then filtered through a membrane filter (average pore size 0.45 μm), and 1 μL of the resulting filtrate was injected into a gas chromatograph (GC) to determine the residual monomer content. The GC measurement conditions are as follows: GC equipment: Agilent Technologies, 6890N Column: Agilent Technologies, HP-1 (0.250 mmφ×30 m, df=1.0 μm) Column temperature: After holding at 40°C for 1 minute, the column was heated to 60°C (at a rate of 5°C / min), then heated to 140°C (at a rate of 10°C / min), and then heated to 300°C (at a rate of 20°C / min), and held at 300°C for 10 minutes. Column flow rate: 2 mL / min (He) Column pressure: constant flow mode (136 kPa) Inlet temperature: 200℃ Injection volume: 1μL Injection method: Split (10:1) Detector: Flame ionization detector (FID) Detector temperature: 250℃

[0149] (Method for measuring residual solvents) Approximately 0.02 g of adhesive sheet was collected and placed in a 20 mL headspace vial. The vial containing the adhesive sheet was then heated at 150°C for 30 minutes in a headspace sampler (HSS), and 1 mL of the gas phase in the heated vial was injected into a GC to determine the residual solvent content. The HSS conditions and GC measurement conditions are shown below. ·HSS conditions HSS device: Agilent Technologies, G1888 Heating temperature: 150℃ Cooking time: 30 minutes Pressurization time: 0.20 minutes Loop filling time: 0.20 min Loop equilibration time: 0.05 min Infusion time: 0.50 minutes Sample loop temperature: 160℃ Transfer line temperature: 200℃ GC measurement conditions (residual solvent) GC equipment: Agilent Technologies, 6890N Column: Agilent Technologies, HP-1 (0.250 mmφ×30 m, df=1.0 μm) Column temperature: held at 40°C for 3 minutes, then increased to 120°C (rate 10°C / min), then increased to 300°C (rate 20°C / min), and held at 300°C for 10 minutes. Column flow rate: 1 mL / min (He) Column pressure: constant flow mode (81 kPa) Inlet temperature: 250℃ Injection volume: 1mL Injection method: Split (20:1) Detector: FID Detector temperature: 250℃

[0150] [comprehensive evaluation] The durability and transparency of the pressure-sensitive adhesive sheets were comprehensively evaluated as follows. A: The humidity durability was rated A, and the whitening was rated A to C. B: Humidity durability is rated B, and whitening is rated A to C. C: Humidity durability is rated C, and whitening is rated A to C. D: At least one of the evaluations of humid durability and whitening was D.

[0151] Next, the method for producing each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples will be described.

[0152] The correspondence between the abbreviations or names shown in the following explanation and the compounds is as follows: BA: n-butyl acrylate BzA: benzyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate AIBN: 2,2'-azobisisobutyronitrile C / L: Trimethylolpropane / tolylene diisocyanate trimer adduct (isocyanate-based crosslinking agent; Tosoh, Coronate L) TetradC: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (multifunctional epoxy crosslinker; TetradC, manufactured by Mitsubishi Gas Chemical Company) KBM403: 3-glycidoxypropyltriethoxysilane (silane coupling agent; Shin-Etsu Chemical Co., Ltd., KBM403)

[0153] [Preparation of (meth)acrylic polymer (A)] (Synthesis Example 1) Into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 94.9 parts by weight of BA, 5.0 parts by weight of AA, and 0.1 parts by weight of HBA were charged. To 100 parts by weight of the mixture of methyl methyl acrylate and HBA, 0.1 parts by weight of AIBN was added as a polymerization initiator. Nitrogen gas was introduced into the flask while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was then maintained at around 55°C, and the polymerization reaction was allowed to proceed for 7 hours. Ethyl acetate was then added to the resulting reaction liquid to adjust the solids concentration to 12% by weight, yielding a solution of (meth)acrylic polymer (A-1). The weight-average molecular weight (Mw) of the (meth)acrylic polymer (A-1) was 2.2 million. Regarding the HSP, the δD, δP, and δH of the (meth)acrylic polymer (A-1) were 16.75 MPa, respectively. 1 / 2 , 3.49 MPa 1 / 2 and 5.38 MPa 1 / 2 It was.

[0154] (Synthesis Example 2) A solution of (meth)acrylic polymer (A-2) was obtained in the same manner as in Synthesis Example 1, except that the monomers used were changed to 79.9 parts by weight of BA, 15.0 parts by weight of BzA, 5.0 parts by weight of AA, and 0.1 parts by weight of HBA. The weight average molecular weight (Mw) of the (meth)acrylic polymer (A-2) was 2.2 million. Regarding HSP, δD, δP, and δH of the (meth)acrylic polymer (A-2) were 17.05 MPa, respectively. 1 / 2 , 3.49 MPa 1 / 2and 5.43 MPa 1 / 2 It was.

[0155] (Synthesis Example 3) A solution of (meth)acrylic polymer (A-3) was obtained in the same manner as in Synthesis Example 1, except that the monomers used were changed to 74.9 parts by weight of BA, 20.0 parts by weight of BzA, 5.0 parts by weight of AA, and 0.1 parts by weight of HBA. The weight average molecular weight (Mw) of the (meth)acrylic polymer (A-3) was 2.3 million. Regarding HSP, δD, δP, and δH of the (meth)acrylic polymer (A-3) were 17.15 MPa, respectively. 1 / 2 , 3.49 MPa 1 / 2 and 5.44 MPa 1 / 2 It was.

[0156] The types and amounts of the monomers and polymerization initiators used in Synthesis Examples 1 to 3, as well as the weight average molecular weights (Mw) and HSP distances Ra of the resulting polymers, are summarized in Table 1. The ΔD, ΔP, and ΔH of the self-polymerization of C / L were 20.50 MPa and 20.50 MPa, respectively. 1 / 2 , 12.40 MPa 1 / 2 and 9.60 MPa 1 / 2 It was.

[0157] [Table 1]

[0158] [Preparation of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Sheet] (Manufacturing Examples 1 to 8) As shown in the following Table 2, a crosslinking agent and the like were mixed with 100 parts by weight of the solid content of the (meth)acrylic polymer (A) to obtain a solvent-based pressure-sensitive adhesive composition. Note that Tetrad-C did not form a self-polymer.

[0159] [Table 2]

[0160] Next, the PSA composition prepared in each Production Example was applied to the release surface of a 38 μm thick PET film (Mitsubishi Chemical Polyester Film, MRF38), a release film whose release surface had been silicone-treated, to form a coating film. This was then left to stand in an environment at 23°C until preheating (leaving time r), after which the base film and coating film were transported while being subjected to successive preheating and main heating in an air-circulating constant-temperature oven, to form PSA sheets of the specified thickness for Examples 1 to 25 and Comparative Examples 1 to 5. The leaving time r and the conditions for preheating and main heating are shown in Table 3 below. The preheating and main heating temperatures are the set temperatures in the preheating section and main heating section of the oven, respectively. The preheating and main heating times are the times the base film and coating film pass through the preheating section and main heating section, respectively.

[0161] [Table 3]

[0162] The evaluation results of the produced pressure-sensitive adhesive sheets are shown in Table 4 below. TEM cross-sectional images of the pressure-sensitive adhesive sheets of Examples 3, 8, and 9 and Comparative Example 3 are shown in Figures 7A to 7D. Domain states 1 to 5 in Table 4 are as follows: State 1: Number of evaluation areas in which the first domain exists State 2: For all first domains, the shortest distance between the first domains and their adjacent first domains State 3: For all second domains, the shortest distance between them and their adjacent second domains State 4: Number of evaluation areas with 10 or fewer second domains State 5: Percentage of all second domains in which the shortest distance between adjacent second domains is 100 nm or more

[0163] [Table 4]

[0164] As shown in Table 4, the pressure-sensitive adhesive sheets of the Examples were more suitable for suppressing dimensional changes than the pressure-sensitive adhesive sheets of the Comparative Examples, and were also superior in transparency and durability. [Industrial Applicability]

[0165] The pressure-sensitive adhesive sheet of the present invention can be used, for example, as an optical pressure-sensitive adhesive sheet for use in an optical laminate and / or an image display device. [Explanation of symbols]

[0166] 1 adhesive sheet 2 Optical Film 10A, 10B, 10C, 10D Optical laminate 11 Image display devices

Claims

1. An adhesive sheet, Ten evaluation regions of 1.5 μm square are arbitrarily set on a cross-sectional image of the pressure-sensitive adhesive sheet, and when an island-like region having a short diameter of 100 nm or more is defined as a first domain, the number of evaluation regions in which the first domain exists is 5 or less, having a haze of 0.1% or more; Adhesive sheet.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the shortest distance between adjacent first domains is 300 nm or more for all first domains observed in the set evaluation area.

3. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein, when an island-like region having a short diameter of 50 nm or more and less than 100 nm is defined as a second domain, the number of evaluation regions in which the number of second domains is 10 or less is 3 or more in the set evaluation regions.

4. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein, when an island-like region having a minor axis of 50 nm or more and less than 100 nm is defined as a second domain, the shortest distance between adjacent second domains is 150 nm or more for all second domains observed in the set evaluation area.

5. 5. The pressure-sensitive adhesive sheet according to claim 1, wherein, when an island-like region having a minor axis of 50 nm or more and less than 100 nm is defined as a second domain, the proportion of second domains having a shortest distance between adjacent second domains of 100 nm or more among all second domains observed in the set evaluation area is 50% or more.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, having a storage modulus G' (25°C) of 0.15 MPa or more.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, which has a storage modulus G' (25°C) of less than 0.5 MPa.

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, which is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate-based crosslinking agent (B).

9. The pressure-sensitive adhesive sheet according to claim 8 , wherein the domains contain a polymer of the isocyanate-based crosslinking agent (B).

10. The pressure-sensitive adhesive sheet according to claim 8 or 9, wherein the amount of the isocyanate-based crosslinking agent (B) in the pressure-sensitive adhesive composition is 1.5 parts by weight or more per 100 parts by weight of the (meth)acrylic polymer (A).

11. The pressure-sensitive adhesive sheet according to any one of claims 8 to 10, wherein the isocyanate-based crosslinking agent (B) is a tolylene diisocyanate-based crosslinking agent.

12. The pressure-sensitive adhesive sheet according to any one of claims 8 to 11, wherein the (meth)acrylic polymer (A) contains a structural unit derived from an aromatic ring-containing monomer.

13. The pressure-sensitive adhesive sheet according to any one of claims 8 to 12, wherein the (meth)acrylic polymer (A) contains a structural unit derived from a hydroxyl group-containing monomer in a content of 1 wt% or less.

14. The pressure-sensitive adhesive sheet according to any one of claims 8 to 13, wherein the pressure-sensitive adhesive composition is a solvent-based composition.

15. An optical laminate comprising the pressure-sensitive adhesive sheet according to any one of claims 1 to 14 and an optical film.

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

Images