KR20240011749A - Adhesive sheets, optical laminates and image display devices - Google Patents

Abstract

In the provided adhesive sheet, when 10 square evaluation areas with a side of 1.5 μm are arbitrarily set on the cross-section of the adhesive sheet, and an island-like region with a short diameter of 100 nm or more is defined as the first domain, the first domain is The number of evaluation regions present is 5 or less, and the haze is 0.1% or more. This adhesive sheet can suppress dimensional changes in the optical film included in the optical laminate and is suitable for ensuring durability and transparency.

Description

Adhesive sheets, optical laminates and image display devices

The present invention relates to adhesive sheets, optical laminates, and image display devices.

In recent years, image display devices typified by liquid crystal displays and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have become rapidly popular. These various image display devices usually have a laminated structure of an image forming layer, such as a liquid crystal layer or an EL emitting layer, and an optical laminated body including an optical film and an adhesive sheet. The adhesive sheet is mainly used for bonding between films included in an optical laminate or for bonding an image forming layer to an optical laminate. Examples of optical films include a polarizing plate, a retardation film, and a polarizing plate with a retardation film in which the polarizing plate and the retardation film are integrated. Patent Documents 1 and 2 disclose an example of an optical laminated body.

Japanese Patent Publication No. 2008-031214 Japanese Patent Publication No. 2009-98665

Excessive changes in the dimensions of the optical film due to temperature changes cause light leakage and color unevenness in the image display device. Light leakage and color unevenness are particularly likely to occur in an image display device that uses a polarizing plate with a retardation film and has a relatively large size. Additionally, image display devices with narrowly designed frames (bezels) are becoming widespread, and suppressing changes in dimensions has become increasingly important. In order to suppress dimensional changes, it is conceivable to increase the elastic modulus of the adhesive sheet included in the optical laminate. However, simply increasing the elastic modulus may reduce the durability of the adhesive sheet, making it unable to keep up with changes in dimensions, and may also result in loss of transparency desired as an optical adhesive sheet.

The purpose of the present invention is to provide an adhesive sheet that can suppress dimensional changes in the optical film included in an optical laminate and is suitable for ensuring durability and transparency.

The present invention,

It is an adhesive sheet,

When 10 square evaluation areas with a side of 1.5 μm are arbitrarily set on the cross-section of the adhesive sheet, and an island-like region with a short diameter of 100 nm or more is defined as the first domain, the evaluation area in which the first domain exists The number is 5 or less,

Having a haze of 0.1% or more,

An adhesive sheet is provided.

In another aspect, the present invention:

An optical laminate comprising the adhesive sheet of the present invention and an optical film

to provide.

In another aspect, the present invention:

An image display device provided with the optical laminate of the present invention

to provide.

According to the present invention, it is possible to provide an adhesive sheet suitable for ensuring durability and transparency while suppressing dimensional changes in the optical film included in the optical laminate.

1 is a cross-sectional view schematically showing an example of the adhesive sheet of the present invention.
Figure 2 is a cross-sectional view schematically showing an example of an optical laminated body including the adhesive sheet of the present invention.
Figure 3 is a cross-sectional view schematically showing an example of an optical laminate including the adhesive sheet of the present invention.
Fig. 4 is a cross-sectional view schematically showing an example of an optical laminate including the adhesive sheet of the present invention.
Fig. 5 is a cross-sectional view schematically showing an example of an optical laminate including the adhesive sheet of the present invention.
Fig. 6 is a cross-sectional view schematically showing an example of an image display device provided with the adhesive sheet of the present invention.
FIG. 7A is a diagram showing a cross-section of the adhesive sheet produced in Example 3 using a transmission electron microscope (TEM).
FIG. 7B is a diagram showing a cross-sectional image by TEM of the adhesive sheet produced in Example 8.
FIG. 7C is a diagram showing a cross-sectional image by TEM of the adhesive sheet produced in Example 9.
FIG. 7D is a diagram showing a cross-sectional image by TEM of the adhesive sheet produced in Comparative Example 3.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below.

In this specification, “(meth)acrylic” means acrylic and methacryl. In addition, “(meth)acrylate” means acrylate and methacrylate.

[Adhesive sheet]

An example of the adhesive sheet of this embodiment is shown in Fig. 1. In the adhesive sheet 1 of FIG. 1, 10 square evaluation areas with a side of 1.5 μm are arbitrarily set on the cross-section of the adhesive sheet 1, and an island-like region with a short diameter of 100 nm or more is defined as the first domain. In this case, the number of evaluation areas in which the first domain exists is 5 or less. Additionally, the adhesive sheet 1 has a haze of 0.1% or more.

In order to increase the elastic modulus of the adhesive sheet, it is conceivable to mix additives with the adhesive composition forming the adhesive sheet, for example. Since it is difficult for the additives to be completely compatible with the materials contained in the adhesive composition, typically the polymer that is the main component, it is believed that the haze of the adhesive sheet increases by mixing the additives. According to the present inventors' examination, it was found that in the adhesive sheet with increased haze, when domains having a size larger than a certain level are generated, the durability and transparency of the adhesive sheet tend to decrease. The creation of domains may cause whitening of the adhesive sheet due to scattering and reflection of light at the domain interface, and may also cause peeling at the domain interface when the adhesive sheet is deformed by an external force. It is thought that this may cause the generation of voids, etc. According to further examination, the adhesive sheet 1, which has a haze of 0.1% or more and is in the above state with respect to the domain, can suppress dimensional changes in the optical film and is suitable for ensuring durability and transparency. .

In this specification, the haze of the adhesive sheet 1 is a value when the thickness is 75 μm, and can be measured based on Japanese Industrial Standards (formerly Japanese Industrial Standards; JIS) K7136:1981.

The haze of the adhesive sheet 1 may be 0.2% or more. The upper limit of haze is, for example, 1% or less, 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, 0.43% or less, 0.4% or less, and further. It may be less than 0.37%.

In this specification, a domain means an island-like region of a sea-island structure that the adhesive sheet 1 may have. The domain may contain substances derived from additives. Additionally, the short diameter of the domain can be determined as the shortest virtual line segment length when a virtual line segment passing through the center of gravity of the domain and having the outer periphery of the domain at both ends is assumed on the cross section. It is desirable that the evaluation areas set on the cross section do not overlap each other. A cross-sectional image can be acquired, for example, by a transmission electron microscope (TEM). The magnification of the cross-section to be acquired is, for example, 10,000 to 30,000 times.

The number of evaluation areas in which the first domain exists may be 4 or less, 3 or less, 2 or less, 1 or less, or even 0.

For all first domains observed in the 10 evaluation areas set on the cross-section of the adhesive sheet 1, the shortest distance between adjacent first domains may be 300 nm or more, 500 nm or more, and even 800 nm or more. do. A large shortest distance means that the density of the domains in the adhesive sheet 1 is low. Additionally, the distance between adjacent domains can be determined as the distance between outer peripheries.

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 in the 10 evaluation regions set on the cross section of the 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, and may even be 10 or more. According to the present inventors' examination, the second domain may affect the durability and transparency of the adhesive sheet 1, although not to the extent of the first domain.

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 10 evaluation areas set on the cross section of the adhesive sheet 1, adjacent second domains The shortest distance between domains may be 150 nm or more, 175 nm or more, and further 200 nm or more.

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, an adjacent second domain among all second domains observed in the above-mentioned 10 evaluation areas set on the cross-section of the adhesive sheet 1 The ratio (number ratio) of the second domains with a shortest distance between them of 100 nm or more may be 50% or more, 60% or more, and even 70% or more.

The state of the domains in the adhesive sheet 1 can be evaluated, for example, by image analysis of the cross-section. For image analysis, various software such as Image J can be used.

The state of the domains in the adhesive sheet 1 changes based on the manufacturing conditions (including heating conditions described later) of the adhesive sheet 1. In addition, the state of the domain is determined by the composition of the adhesive composition (I), the composition and characteristics (e.g. glass transition temperature) of the (meth)acrylic polymer (A), the type and mixing amount of the crosslinking agent (B), and the type and amount of additives. It may change based on the mixing amount, etc.

The thickness of the 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, and further 10 to 20 μm.

The storage modulus (G') (25°C) of the adhesive sheet 1 is, for example, 0.15 MPa or more, and may be 0.16 MPa or more, 0.17 MPa or more, and further may be 0.18 MPa or more. The upper limit of the storage modulus (G') (25°C) is, for example, 5 MPa or less, 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. It may be MPa or less, and further may be less than 0.5 MPa. The pressure-sensitive adhesive sheet 1 having a storage modulus (G') in the above range is particularly suitable for suppressing dimensional changes in optical films.

The storage elastic modulus (25°C) of the adhesive sheet 1 can be evaluated by the following method. First, prepare a sample for measurement made of the material constituting the adhesive sheet 1. The shape of the sample for measurement is disk-shaped. The sample for measurement has a bottom diameter of 8 mm and a thickness of 2 mm. The sample for measurement may be a laminate in which a plurality of adhesive sheets 1 are laminated and punched out onto a disk. Next, dynamic viscoelasticity measurement is performed on the measurement sample. For dynamic viscoelasticity measurement, for example, ARES-G2 manufactured by TA Instruments can be used. From the results of the dynamic viscoelasticity measurement, the storage elastic modulus (G') of the adhesive sheet 1 at 25°C can be specified. In addition, the conditions for dynamic viscoelasticity measurement are as follows.

·Measuring conditions

Frequency: 1Hz

Deformation Mode: Torsion

Measurement temperature: -70℃ to 150℃

Temperature increase rate: 5℃/min

The gel fraction of the adhesive sheet 1 is, for example, 60% or more, and may be 65% or more, and may even be 70% or more. The upper limit of the gel fraction is, for example, 99% or less, and may be 98% or less, and further may be 95% or less. The pressure-sensitive adhesive sheet 1 with the gel fraction in the above range is particularly suitable for suppressing dimensional changes in the optical film.

The gel fraction of the adhesive sheet 1 can be evaluated by the following method. First, about 0.2 g is scraped off from the adhesive sheet 1 to obtain small pieces. Next, the obtained small piece is surrounded by a stretched porous polytetrafluoroethylene film (NTF1122 manufactured by Nitto Denko, average pore diameter 0.2 μm) and tied with a string to obtain a test piece. Next, the weight (A) of the obtained test piece is measured. Weight (A) is the sum of the weight of the small pieces of the adhesive sheet, the stretched porous membrane, and the lead string. The total weight (B) of the stretched porous membrane and yarn used is measured in advance. Next, the test piece is immersed in a container with an internal volume of 50 mL filled with ethyl acetate and left to stand at 23°C for one week. After standing, the test piece is removed from the container, dried in a dryer set at 130°C for 2 hours, and then the weight (C) of the test piece is measured. From the measured weight (A), weight (B) and weight (C), the gel fraction of the adhesive sheet 1 is obtained by the formula: gel fraction (% by weight) = (C-B)/(A-B) x 100 (%) Calculate .

The adhesive sheet 1 may be formed from an 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 adhesive sheet 1 is not limited to the above example.

[Adhesive composition (I)]

The 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 adhesive composition (I) as the main component. In other words, the adhesive composition (I) is an acrylic adhesive composition. The main component refers to the component with the highest content in the composition. The content rate 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, and further may be 75% by weight or more.

((meth)acrylic polymer (A))

The (meth)acrylic polymer (A) preferably has as its main unit a structural unit derived from a (meth)acrylic monomer (A1) having an alkyl group of 1 to 30 carbon atoms in the side chain. The alkyl group may be linear or may have branches. The (meth)acrylic polymer (A) may have one or two or more types of structural units derived from the (meth)acrylic monomer (A1). Examples of (meth)acrylic monomer (A1) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, and t-butyl (meth)acrylate. Acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth) Acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate and n-tetradecyl(meth)acrylate. It is acrylate. In this specification, the “main unit” refers to, 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 of all structural units of the polymer. It means a unit that occupies more than one.

The (meth)acrylic polymer (A) may have a structural unit derived from a (meth)acrylic monomer (A1) having a long-chain alkyl group in the side chain. An example of the monomer (A1) is n-dodecyl (meth)acrylate (lauryl (meth)acrylate). In this specification, “long-chain alkyl group” means an alkyl group having 6 to 30 carbon atoms.

The (meth)acrylic polymer (A) may have a structural unit derived from the (meth)acrylic monomer (A1) whose glass transition temperature (Tg) is in the range of -70 to -20°C when used as a homopolymer. An example of the monomer (A1) is n-butylacrylate.

The (meth)acrylic polymer (A) may have structural units other than those derived from the (meth)acrylic monomer (A1). The structural unit is derived from a monomer (A2) copolymerizable with a (meth)acrylic monomer (A1). The (meth)acrylic polymer (A) may have one type or two or more types of the structural unit.

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

Another example of monomer (A2) is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth)acrylic monomer. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. , hydroxyalkyl (meth)acrylates such as 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate, and (4-hydride) Roxymethylcyclohexyl)-methyl acrylate. Additionally, hydroxyl groups can react with various crosslinking agents. From the viewpoint of improving 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, and further 0.1% by weight. It may be % or less, and may be 0% by weight (not including the structural unit).

The monomer (A2) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Examples of carboxyl group-containing monomers are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of amino group-containing monomers are N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of amide group-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, and N-methyl(meth)acrylamide. Acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylol-N-propane (meth)acrylamide, aminomethyl (meth) Acrylamide-based monomers such as 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 monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. By having the (meth)acrylic polymer (A) having a structural unit derived from a carboxyl group-containing monomer, especially acrylic acid, for example, the self-polymerization of the isocyanate crosslinking agent (B) can be increased. The improvement in the self-polymerization of the crosslinking agent (B) can particularly contribute to suppressing peeling of the adhesive sheet in a humidified environment and stabilizing the physical properties of the adhesive sheet in systems containing a high content of the crosslinking agent (B).

The monomer (A2) may be a polyfunctional monomer. Examples of polyfunctional monomers include 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. multifunctional acrylates such as; And it is divinylbenzene. Multifunctional acrylates are preferably 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

The total content of structural units derived from carboxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, and polyfunctional monomers in the (meth)acrylic polymer (A) is preferably 20% by weight or less, and more preferably is 10% by weight or less, more preferably 8% by weight or less. When the (meth)acrylic polymer (A) has the structural unit, 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.

Examples of other monomers (A2) include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, (meth)acrylic acid alkoxyalkyl esters such as 3-ethoxypropyl (meth)acrylic acid, 4-methoxybutyl (meth)acrylic acid, and 4-ethoxybutyl (meth)acrylic acid; Epoxy group-containing monomers such as glycidyl (meth)acrylate and methyl glycidyl (meth)acrylate; monomers containing sulfonic acid groups such as sodium vinyl sulfonate; Monomer containing a phosphate group; (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 it is vinyl chloride.

The total content of 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, or is 0% by weight ( It is preferable that it does not contain the structural unit.

The (meth)acrylic polymer (A) can be formed by polymerizing one or two or more types of monomers described above by a known method. You may polymerize a monomer and a partially polymerized product of the monomer. Polymerization can be performed, 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 can form a pressure-sensitive adhesive sheet with excellent optical transparency. Polymerization is preferably carried out avoiding contact between the monomer and/or partial polymer and oxygen. For this reason, for example, polymerization is performed in an inert gas atmosphere such as nitrogen, or in a state where oxygen is blocked by a resin film, etc. Polymerization of can be employed. The formed (meth)acrylic polymer (A) may be any form such as a random copolymer, a block copolymer, or a graft copolymer.

The polymerization system that forms the (meth)acrylic polymer (A) may contain one type or two or more types of polymerization initiators. The type of polymerization initiator can be selected through polymerization reaction, and may be, for example, a thermal polymerization initiator or a photopolymerization initiator.

Solvents used in solution polymerization include, for example, 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; 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.

Polymerization initiators used in solution polymerization include, for example, azo-based polymerization initiators, peroxide-based polymerization initiators, and redox-based polymerization initiators. Peroxide-based polymerization initiators include, for example, dibenzoyl peroxide and t-butyl permaleate. Among them, the azo-based polymerization initiator disclosed in Japanese Patent Application Laid-Open No. 2002-69411 is preferable. The azo-based polymerization initiator is, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2- Methyl propionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the above examples. The amount of the azo 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, based on 100 parts by weight of the total amount of monomers.

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

Photopolymerization initiators include, for example, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, and benzyl-based photopolymerization initiators. , a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. However, the photopolymerization initiator is not limited to the above examples.

Benzoin ether-based photopolymerization initiators include, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-di. Phenylethan-1-one, anisole methyl ether. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, 4 -(t-Butyl)dichloroacetophenone. The α-ketol-based photopolymerization initiator is, for example, 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. The aromatic sulfonyl chloride-based photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. A photoactive oxime-based photopolymerization initiator is, for example, 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. The benzoin-based photopolymerization initiator is, for example, benzoin. The benzyl-based photopolymerization initiator is, for example, benzyl. Benzophenone-based photopolymerization initiators include, for example, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. The ketal-based photopolymerization initiator is, for example, benzyldimethyl ketal. Thioxanthone-based photopolymerization initiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, and 2,4-diiso Propylthioxanthone and dodecylthioxanthone.

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, based on 100 parts by weight of the total amount of monomers.

The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is, for example, 1 million to 2.8 million, and may be 1.2 million or more, and further 1.4 million or more, from the viewpoint of durability and heat resistance of the adhesive sheet. The weight average molecular weight (Mw) of polymers and oligomers in this specification is a value (polystyrene conversion) based on measurement by GPC (gel permeation chromatography).

The content of the (meth)acrylic polymer (A) in the adhesive composition (I) is, in terms of solids ratio, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, and further may be 80% by weight or more. The upper limit of the content rate is, for example, 99% by weight or less, and may be 97% by weight or less, 95% by weight or less, 93% by weight or less, and further 90% by weight or less.

(Isocyanate-based crosslinking agent (B))

The isocyanate-based crosslinking agent (B) is a type of additive for the 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 be a trifunctional or higher crosslinking agent having 3 or more crosslinking reactive groups per molecule. The upper limit of the number of crosslinking reactive groups per molecule is, for example, 5.

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

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. .

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

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

The crosslinking agent (B) may be a derivative of the above isocyanate compound. Examples of derivatives include multimers (dimers, trimers, pentamers, etc.), adducts (adducts) obtained by addition to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, and allophanate-modified products. It is a urethane prepolymer obtained by adding polyol, isocyanurate modified product, carbodiimide modified product, and polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

The crosslinking agent (B) is preferably an aromatic isocyanate compound and its derivatives, and more preferably tolylene diisocyanate and its derivatives (in other words, tolylene diisocyanate-based (TDI-based) crosslinking agent). The TDI-based crosslinking agent has superior reaction uniformity compared to xylylene diisocyanate and its derivatives (in other words, xylylene diisocyanate-based (XDI-based) crosslinking agent). An example of a TDI-based crosslinking agent is an adduct of tolylene diisocyanate and a polyfunctional alcohol, and a more specific example is a trimethylolpropane/tolylene diisocyanate trimer adduct.

A commercial product can be used as the crosslinking agent (B). Examples of commercial products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, and Coronate HX (above, coating agents: all brand names), And 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 These are Nate D-178N, Takenate 500, and Takenate 600 (above, manufactured by Mitsui Chemicals; all are brand names). As the crosslinking agent (B), Coronate L, Takenate D-102, and Takenate D-103 (all of which are trimethylolpropane/tolylene diisocyanate trimer adducts) can be preferably used.

The compounding amount of the crosslinking agent (B) in the adhesive composition (I) is, for example, 1.5 parts by weight or more, 2 parts by weight or more, and even 2.5 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A). do. The upper limit of the mixing amount is, for example, 25 parts by weight or less, even if it is 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, and even 4 parts by weight or less. do.

The adhesive composition (I) may contain one or two or more types of crosslinking agents (B).

When the pressure-sensitive adhesive sheet 1 is formed from a pressure-sensitive adhesive 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 a polymer is the self-polymer of crosslinking agent (B).

When assuming a self-polymer (C) of an isocyanate-based crosslinking agent (B), the distance (Ra) of the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) is 15 or less. do. The heat generated when forming the adhesive sheet 1 may cause the isocyanate-based crosslinking agents (B) to react with each other to form a self-polymer of the crosslinking agent (B). The formation of the self-polymer can contribute to the formation of an adhesive sheet that can suppress dimensional changes in the optical film by increasing the cohesion of the adhesive sheet. However, when the compatibility between the (meth)acrylic polymer (A) and the self-polymer is low, it is conceivable that independent domains rich in the self-polymer are likely to occur inside the adhesive sheet. According to the present inventors' examination, the distance Ra of 15 or less may contribute to the formation of the first domain and/or the second domain in the above state.

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

The Hansen Solubility Parameter (HSP) is a solubility parameter introduced by Hildebrand that is divided into three components: a dispersion term (δD), a polarization term (δP), and a 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 unit of each component is usually MPa ^1/2 . One point (vector) in a three-dimensional space known as Hansen's space is determined by the above three components. The distance (Ra) is the points (DA, P _{A ,} H _A ) corresponding to the (meth)acrylic polymer (A) and the points (D _C , P _C , It is the distance between H _C ), and can be calculated by the formula: {4×(δD _A -δD _B ) ² +(δP _A -δP _B ) ² +(δH _A -δH _B ) ² } ^1/2 . For details on Hansen solubility parameters, see “Hansen Solubility Parameters; It is disclosed in “A Users Handbook (CRC Press, 2007).” δD, δP and δH of the polymer can be determined by calculation, for example, using known software such as HSPiP (version 5), based on the structural units the polymer has and the content of the units in the polymer. . More specifically, 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 the unit are calculated as δD, δP, and δH of the polymer. can do. However, the calculation is performed with the temperature set to 23°C. Additionally, the calculated values of δD, δP, and δH may differ slightly depending on the software used. However, the difference is usually of a size that can be ignored in determining Ra. For crosslinking agents, Hansen solubility parameters are calculated only for those that form self-polymers.

The self-polymer (C) assumed in calculating the distance (Ra) is a homopolymer containing structural units derived from an isocyanate-based crosslinking agent (B). However, the self-polymer of the crosslinking agent (B) actually contained in the adhesive sheet formed from the adhesive composition (I) may contain structural units other than those derived from the crosslinking agent (B).

((meth)acrylic oligomer)

The adhesive composition (I) may further contain a (meth)acrylic oligomer (D).

The (meth)acrylic oligomer (D) may have the same composition as the (meth)acrylic polymer (A) described above except that the weight average molecular weight (Mw) is different. The weight average molecular weight (Mw) of the (meth)acrylic oligomer (D) is, for example, 1000 or more, and may be 2000 or more, 3000 or more, and further may be 4000 or more. The upper limit of the weight average molecular weight (Mw) of the (meth)acrylic oligomer is, for example, 30,000 or less, and may be 15,000 or less, 10,000 or less, and further may be 7,000 or less.

The (meth)acrylic oligomer (D) has, for example, one or two or more types of structural units derived from the following monomers: methyl (meth)acrylate, ethyl (meth)acrylate, and 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, nonyl ( Alkyl (meth)acrylates such as meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate. rate; Esters of (meth)acrylic acid and alicyclic alcohol, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclofentanyl (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.

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 adhesive sheet can be further improved. Examples of the acrylic monomer 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 alcohol, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclofentanyl (meth)acrylate; These are 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. In addition, when irradiating ultraviolet rays during polymerization of the (meth)acrylic oligomer (D) and/or during formation of the adhesive sheet, it is difficult to inhibit the progress of polymerization and/or formation, so the monomer has an unsaturated bond. It is preferable that it does not have, and for example, an alkyl (meth)acrylate having an alkyl group having a branched structure, or an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

Specific examples of the (meth)acrylic oligomer (D) include copolymers of butylacrylate, methyl acrylate, and acrylic acid, copolymers of cyclohexyl methacrylate and isobutyl methacrylate, and cyclohexyl methacrylate and isobutyl methacrylate. Copolymer with bornyl methacrylate, copolymer with cyclohexyl methacrylate and acryloylmorpholine, copolymer with cyclohexyl methacrylate and diethylacrylamide, 1-adamantyl acrylate and methyl Copolymer with methacrylate, copolymer with dicyclopentanyl methacrylate and isobornyl methacrylate, dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate A copolymer of at least one selected from cyclopentanyl methacrylate and methyl methacrylate, a homopolymer of dicyclopentanyl acrylate, a homopolymer of 1-adamantyl methacrylate, and 1-adamantyl acrylate. It is a homopolymer of latex.

To polymerize the (meth)acrylic oligomer (D), the method for polymerizing the (meth)acrylic polymer (A) described above can be adopted.

When the adhesive composition (I) contains a (meth)acrylic oligomer (D), the compounding amount is, for example, 70 parts by weight or less, and 50 parts by weight or less, with respect to 100 parts by weight of the (meth)acrylic polymer (A). , furthermore, it may be 40 parts by weight or less. The lower limit of the compounding amount is, for example, 1 part by weight or more, and may be 2 parts by weight or more, and further may be 3 parts by weight or more, with respect to 100 parts by weight of the (meth)acrylic polymer (A). The adhesive composition (I) does not need to contain the (meth)acrylic oligomer (D).

(additive)

The adhesive composition (I) may contain other additives. Examples of additives include crosslinking agents other than the isocyanate-based crosslinking agent (B), silane coupling agents, colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, rework improvers, softeners, antioxidants, These are powders, particles, and thin substances such as anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts of ionic compounds, ionic liquids, ionic solids, etc.), inorganic fillers, organic fillers, and metal powders. The additive can be blended in an amount of, for example, 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 1 part by weight or less, with respect to 100 parts by weight of the (meth)acrylic polymer (A).

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 multifunctional metal chelates. When the pressure-sensitive adhesive composition (I) contains a crosslinking agent other than the isocyanate-based crosslinking agent (B), the total amount blended is preferably 0.1 to 5 parts by weight, and 0.1 to 5 parts by weight, based on 100 parts by weight of the (meth)acrylic polymer (A). It is more preferable in the following order: 3 parts by weight, 0.1 to 2 parts by weight, and 0.1 to 1 part by weight. The adhesive composition (I) does not need to contain a crosslinking agent other than the isocyanate-based crosslinking agent (B), for example, an epoxy-based crosslinking agent.

Examples of silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl). ) Silane coupling agents containing epoxy groups such as ethyltrimethoxysilane; 3-Aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine and N -Amino group-containing silane coupling agents such as phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and silane coupling agents containing isocyanate groups such as 3-isocyanate propyltriethoxysilane.

When the adhesive composition (I) contains a silane coupling agent, the compounding amount is, for example, 5 parts by weight or less, 3 parts by weight or less, and 1 part by weight or less, with respect to 100 parts by weight of the (meth)acrylic polymer (A). , it may be 0.5 part by weight or less, 0.2 part by weight or less, 0.1 part by weight or less, and further 0.05 part by weight or less. The adhesive composition (I) does not need to contain a silane coupling agent.

Types of the adhesive composition (I) include, for example, emulsion type, solvent type (solution type), active energy ray curing type (photocuring type), and heat melt type (hot melt type). From the viewpoint of forming a more durable adhesive sheet, the adhesive composition (I) may be of a solvent type. The solvent-type adhesive composition (I) does not need to contain a photocuring agent such as an ultraviolet curing agent.

The adhesive sheet 1 can be used for optical purposes, for example. The adhesive sheet 1 may be used in an optical laminate and/or an image display device. The adhesive sheet 1 is suitable for use in image display devices that specifically require suppression of dimensional changes with respect to optical films, such as image display devices with narrow frames or image display devices with relatively large screen sizes. By using these image display devices, for example, peeling of the film included in the optical laminated body is suppressed.

[Method of manufacturing adhesive sheet]

The adhesive sheet 1 can be formed, for example, by the manufacturing method of this embodiment described below. However, the adhesive sheet 1 may be formed by another manufacturing method.

The manufacturing method of this embodiment is to heat a coating film of an adhesive composition (I) containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate-based crosslinking agent (B), and forming an adhesive sheet from the coating film. It includes forming (1). Hereinafter, the heating of the coating film is referred to as main heating. In this heating, crosslinking and curing of the adhesive composition (I) contained in the coating film mainly progresses by heat.

The conditions for this heating satisfy the following equation (1) or (2). However, x and y are the heating temperature (°C) and time (seconds) in the main heating, respectively. Equation (2) means that when the heating temperature (x) exceeds 120°C, the heating time (y) must be limited within a predetermined time. The heating temperature (x) can be set as the highest temperature at which the coating film is exposed, for example, the set temperature of a heating device such as a heating oven used to heat the coating film (a plurality of different sections of the set temperature are set to the heating device). When provided or when the set temperature changes over time, it can be set as the highest set temperature at which the coating film is exposed within the heating device. The heating time (y) can be determined as the time during which the coating film is exposed to a temperature exceeding 120°C. When using a heating device, for example, time (y) is determined as the time for the coating film to be placed in a space set to a temperature exceeding 120℃, or the time for the coating film to pass through a section set to a temperature exceeding 120℃. It's okay too. If there are multiple sections set to a temperature exceeding 120°C, the sum of the time passing through the sections can be determined as time (y). When the set temperature changes over time, the time while the set temperature exceeds 120°C can be calculated as time (y). The same applies to the temperature (p) and time (q) of preheating described later.

x≤120… (One)

x>120, also y≤-2.17x+365.83… (2)

According to the examination by the present inventors, the solubility of the isocyanate-based crosslinking agent (B) in the monomer state deteriorates under high temperatures, and it tends to gradually aggregate inside the coating film. For this reason, the higher the temperature (x) and the longer the time (y), the easier it is for the independent domains to be created in the adhesive sheet, and the size and density of the created domains tend to increase. On the other hand, when the temperature (x) is below a certain level, the formation of oligomers such as dimers and trimers by self-polymerization between the crosslinking agents (B) proceeds preferentially, and aggregation is suppressed. This heating under conditions satisfying the above formula (1) or (2) is suitable for suppressing aggregation of the crosslinking agent (B).

The lower limit of temperature (x) is, for example, 80°C or higher, and may be 85°C or higher, and may also be 90°C or higher. The upper limit of temperature (x) is, for example, 165°C or lower, and may be 160°C or lower. The upper limit of temperature (x) under conditions that satisfy equation (1) may be 115°C or lower, 110°C or lower, 105°C or lower, 100°C or lower, 95°C or lower, and further 90°C or lower. The temperature (x) of the main heating may be kept constant throughout the main heating or may be changed during main heating.

The lower limit of 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, and even 50 seconds or more. The upper limit of time y is, for example, 300 seconds or less, and may be 180 seconds or less, and may even be less than 180 seconds. The upper limit of time (y) under conditions that satisfy equation (2) is 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, and further. It can be less than 60 seconds.

The conditions for this heating may satisfy the formula: y≤-2.17x+345.83 when x>120. In heating that satisfies the above equation, time (y) is further limited compared to heating that satisfies equation (2).

The conditions for this heating may be that x>120 satisfies y≤80, and further may satisfy y≤60.

The conditions for this heating may be x ≤ 120, y < 180, y ≤ 160, y ≤ 140, y ≤ 120, y ≤ 110, y ≤ 100, y < 100, y ≤ 95, and further. y≤90 may be satisfied.

In the manufacturing method of the present embodiment, before performing the main heating on the coating film of the adhesive composition (I), the coating film is preheated ( It may further include preliminary heating. The temperature (p) of preheating is lower than the temperature (x) of main heating. In the preheating, drying of the coating film and, in the case of the solvent-type pressure-sensitive adhesive composition (I), removal of the solvent are mainly carried out. Removal of the solvent can contribute to suppressing aggregation of the isocyanate-based crosslinking agent (B). In addition, preheating can contribute to producing an oligomer of the crosslinking agent (B) by suppressing melting of the isocyanate-based crosslinking agent (B) and advancing the reaction with a compound having a hydroxy group, typically water, to some extent.

The temperature (x) (°C) of the main heating and the temperature (p) (°C) of the preheating may satisfy the formula: x-p≤55. x-p 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, and further 10°C or less. The lower limit of x-p is greater than 0°C, and may be 5°C or higher, and may also be 10°C or higher. The small difference between the temperature (x) and the temperature (p) can contribute to suppressing shrinkage of the coating film due to a sudden change in temperature.

The temperature (p) is, for example, 50°C or more and less than 80°C. The lower limit of the temperature (p) may be 55°C or higher, 60°C or higher, 65°C or higher, and further may be 70°C or higher. The upper limit of temperature (p) may be 75°C or lower. The temperature (p) of the preheating may be kept constant throughout the preheating or may be changed during preheating.

The time (q) is, for example, 5 seconds or longer, and may be 10 seconds or longer, 15 seconds or longer, 20 seconds or longer, 25 seconds or longer, 30 seconds or longer, 35 seconds or longer, 40 seconds or longer, and further 45 seconds or longer. The upper limit of time q is, for example, 180 seconds or less, and may be 120 seconds or less, 115 seconds or less, and further 110 seconds or less.

When the adhesive composition (I) is a solvent type, the time (q) is such that the solvent contained in the coating film is 30% or less, preferably 25% or less, more preferably 20% or less relative to the content before preheating. You can set it like this.

Time (q) is expressed by q/(q+y), which is the time ratio of preheating to the total time of preheating and main heating, and may satisfy 0.2≤q/(q+y)≤0.6. . The lower limit of q/(q+y) may be 0.25 or more, and may even be 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, and further 0.4 or less.

Preheating may be performed after a predetermined time (r) has elapsed from the formation of the coating film. Securing the 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. The time r is, for example, 5 to 180 seconds, and may be 5 to 120 seconds or 10 to 60 seconds. During the time r, the coating film is in a non-heated atmosphere, for example, in an atmosphere of 20 to 30°C.

Preliminary heating and main heating may be performed continuously. As a more specific example, one heating device is divided into a preheating section and a main heating section, and the temperature (x, p) of each section is set independently, from the preheating section to the main heating section. The coating film may be conveyed continuously.

The coating film provided for the heating can be formed, for example, by applying the adhesive composition (I) or a mixture of the adhesive composition (I) and a solvent to a base film. The base film is typically a resin film or a metal film. The base film may be a film (release film) in which a peeling treatment has been performed on the applied surface. In one example of a release film, the application surface is peeled off using a silicone compound. Additionally, the base film may be an optical film, and in this case, an optical laminate containing the adhesive sheet and the optical film can be formed.

For application to the base film, a known method can be adopted. Application includes, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, extrusion by die coater, etc. It can be done by court.

The composition and mixture applied to the base film preferably have a viscosity suitable for handling and coating.

[Optical laminate]

An example of the optical laminated body 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 on each other. The optical laminate 10A can be used as an optical film with an adhesive sheet.

Examples of the optical film 2 are 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 example. The optical film 2 may contain a glass film.

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

A retardation film is a film that has birefringence in the in-plane direction and/or the thickness direction. The retardation film is, for example, a stretched resin film or a film obtained by aligning and fixing a liquid crystal material.

The retardation film includes a λ/4 plate, a λ/2 plate, an anti-reflection retardation film (e.g., see paragraphs 0221, 0222, and 0228 of Japanese Patent Application Laid-Open No. 2012-133303), and a retardation film for viewing angle compensation (e.g., Refer to paragraphs 0225 and 0226 of Japanese Patent Application Laid-Open No. 2012-133303), or an inclined orientation retardation film for viewing angle compensation (for example, see paragraph 0227 of Japanese Patent Application Laid-Open No. 2012-13303). 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. There are no limitations on the retardation value, arrangement angle, three-dimensional birefringence, and whether the retardation film is single-layered or multi-layered. As the retardation film, a known film can be used.

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, and further 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, and further 100 μm or more.

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 adhesive sheet 1 may be used to bond each layer.

Another example of the optical laminated body of this embodiment is shown in FIG. 3. The optical laminate 10B in FIG. 3 has a laminated structure in which the release liner 3, the adhesive sheet 1, and the optical film 2 are laminated in this order. The optical laminate 10B can be used as an optical film with an adhesive sheet by peeling off the release liner 3.

The release liner 3 is typically a resin film. Examples of the resin constituting the release liner 3 are polyester such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the release liner 3 that is in contact with the adhesive sheet 1 may be subjected to a release treatment. The peeling treatment is, for example, treatment with a silicone compound. However, the release liner 3 is not limited to the above examples. The release liner 3 is peeled off when the optical laminate 10B is used, for example, when attached to the image forming layer.

Another example of the optical laminated body of this embodiment is shown in FIG. 4. The optical laminate 10C in FIG. 4 has a laminated structure in which the release liner 3, the adhesive sheet 1, the retardation film 2A, the interlayer adhesive 4, and the polarizing plate 2B are laminated in this order. The optical laminate 10C can be used by peeling off the release liner 3 and then attaching it to an image forming layer, for example.

As the interlayer adhesive 4, a known adhesive can be used. The adhesive sheet (1) may be used for the interlayer adhesive (4).

Another example of the optical laminated body of this embodiment is shown in FIG. 5. The optical laminate 10D in FIG. 5 includes a release liner 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B, and a protective film 5 laminated in this order. It has a layered structure. The optical laminate 10D can be used by, for example, attaching it to an image forming layer after peeling off the release liner 3.

The protective film 5 covers 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 the image display device. ) has the function of protecting. Additionally, the protective film 5 may function as a window to external space when incorporated into the image display device. The protective film 5 is typically 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, and polyamide, with polyester being preferred. However, the protective film 5 is not limited to the above example. The protective film 5 may be a glass film or a laminated film containing a glass film. The protective film 5 may be subjected to surface treatment such as anti-glare, anti-reflection, anti-static, etc.

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

The optical laminate may have any configuration as long as it includes a pressure-sensitive adhesive sheet formed by the pressure-sensitive adhesive sheet manufacturing method.

The optical laminated body of this embodiment can be distributed and stored, for example, as a wound body obtained by winding a strip-shaped optical laminated body or as a sheet-shaped optical laminated body.

The optical laminated body of this embodiment is typically used in an image display device. Image display devices are, for example, EL displays such as liquid crystal displays, organic EL displays, and inorganic EL displays.

[Image display device]

An example of the image display device of this embodiment is shown in FIG. 6. The image display device 11 in FIG. 6 includes a substrate 7, an image forming layer (for example, an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, a retardation film 2A, and an interlayer adhesive 4. , it has a laminated structure in which the polarizing plate 2B and the protective film 5 are laminated in this order. The image display device 11 has the optical laminated bodies 10A, 10B, 10C, and 10D of FIGS. 2 to 5 (however, the release liner 3 is excluded). The substrate 7 and the image forming layer 6 may have the same configuration as the substrate and image forming layer provided in a known image display device.

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 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 appliance applications, vehicle-mounted applications, public information display (PID) applications, etc.

The image display device may have any configuration as long as it is provided with a pressure-sensitive adhesive sheet formed by the pressure-sensitive adhesive sheet manufacturing method and/or an optical laminated body formed by the optical laminated body manufacturing method.

Example

Hereinafter, the present invention will be explained in more detail through examples. The present invention is not limited to the examples shown below.

First, the evaluation method of the (meth)acrylic polymer and adhesive sheet produced in Examples and Comparative Examples is shown.

[Weight average molecular weight (Mw)]

The weight average molecular weight (Mw) of the (meth)acrylic polymer was evaluated by GPC under the following conditions.

·Analysis device: Waters, Acquity APC

Column: Dosoje, G7000HXL+GMHXL+GMHXL

·Column temperature: 40℃

Eluent: Tetrahydrofuran (acid added)

·Flow rate: 0.8mL/min

·Injection volume: 100μL

Detector: Differential refractometer (RI)

·Standard sample: made by Agilent, polystyrene (PS)

[Distance (Ra)]

The distance (Ra) was calculated by the method described above. As software, HSPiP (version 5) was used.

[Storage modulus (G') (25℃)]

The storage elastic modulus (G') (25°C) of the adhesive sheet was evaluated by the method described above. However, the sample for measurement was prepared by punching a laminate obtained by overlapping the produced adhesive sheets into a disk shape. ARES-G2 manufactured by TA Instruments was used to measure the dynamic viscoelasticity of the measurement sample.

[all sorts of flowers]

The degree of whitening of the adhesive sheet was evaluated as follows based on the measurement of haze for the adhesive sheet. It can be judged that the smaller the haze, the smaller the degree of whitening. The haze of the adhesive sheet was measured in an atmosphere of 25°C using a haze meter HZ-V3 manufactured by Suga Chemicals in accordance with JIS K7136:1981. Measurements were made when 5 layers (adhesive sheet thickness: 15 μm) or 3 layers (adhesive sheet thickness: 25 μm) were bonded onto slide glass S012140 (thickness: 1.3 mm) manufactured by Matsunami Glass Co., Ltd. (both It was carried out with a total thickness of 75 μm). For the adhesive sheet of Example 21 with a thickness of 35 μm, the measured value (V) in the two-layer bonded state (total thickness of 70 μm) is a value corresponding to a total thickness of 75 μm, according to the formula: V × 75/70 Converted.

A: Measured haze is less than 0.37%

B: Measured haze is 0.37% or more but less than 0.43%

C: Measured haze is 0.43% or more but less than 0.50%

D: Measured haze is 0.50% or more

[Domain status]

The state of the domain of the adhesive sheet was evaluated by the above evaluation method for the cross-sectional image of the adhesive sheet. The cross-sectional image was acquired by TEM (HT7820, manufactured by Hitachi Seisakusho; acceleration voltage 100 kV), and the magnification was set to 20,000 times. The sample to be used for TEM was prepared by subjecting the adhesive sheet to be evaluated to a heavy metal staining treatment with RuO ₄ , embedding it with a resin, and then cutting it to a thickness of about 100 nm using an ultra-thin sectioning method. Ten evaluation areas were set on the cross section so as not to overlap each other. The condition was evaluated by image analysis of the cross-section, and Image J was used for image analysis. States 1 to 5 of the evaluated domain and the evaluation criteria for each state are as follows.

(State 1: Number of evaluation areas in which the first domain exists)

A: Number of evaluation areas is 0

B: Number of evaluation areas is 1 to 2

C: Number of evaluation areas is 3 to 5

D: Number of evaluation areas is 6 or more

(State 2: For all first domains, shortest distance between adjacent first domains)

A: The shortest distance is more than 300nm

D: Shortest distance is less than 300nm

(State 3: For all second domains, shortest distance between adjacent second domains)

A: The shortest distance is more than 200nm

C: Shortest distance is more than 150nm and less than 200nm

D: Shortest distance is less than 150nm

(State 4: Number of evaluation areas where the number of second domains is 10 or less)

A: Number of evaluation areas is 3 or more

D: Number of evaluation areas is 1 to 2

(State 5: Among all second domains, ratio of domains whose shortest distance between adjacent second domains is 100 nm or more)

A: More than 50%

D: less than 50%

[Humidification Durability]

The humidification durability (corresponding to an accelerated durability test) of the adhesive sheet was evaluated by the following method. First, a circularly polarizing plate with an adhesive sheet was formed in which each adhesive sheet produced in Examples and Comparative Examples was provided on one exposed surface. Next, the circularly polarizing plate was fixed to the surface of a glass plate (Eagle XG, manufactured by Corning) through the adhesive sheet. Fixation of the circularly polarizing plate was performed in an atmosphere of 23°C and 50% RH. Next, after processing in an autoclave at 50°C and 5 atm (absolute pressure) for 15 minutes, leaving it until cooled to 23°C to stabilize the bonding of the circularly polarizing plate to the glass plate, It was left in a heated and humidified atmosphere for 500 hours. After leaving it in an atmosphere of 23°C and 50% RH, visually check whether the circularly polarizing plate peels off from the glass plate or foaming occurs between the glass plate and the circularly polarizing plate. Humidification durability is as follows. was evaluated.

A: No changes in appearance such as foaming or peeling are observed.

B: Although some individual peeling or foaming is seen at the end, it is within a range that is not problematic in practical terms.

C: At the end, some continuous peeling or foaming is observed, but it is within a range that is not problematic in practical terms.

D: Significant peeling or foaming is observed at the ends, which poses a problem in practical terms.

Hereinafter, a method of forming a circularly polarizing plate with an adhesive sheet used for evaluation of humidification durability is shown.

<Production of polarizer P1>

(Production of polarizer)

A long polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray, product name “PE3000”, thickness 30 μm) was stretched uniaxially in the longitudinal direction (total stretching ratio 5.9 times) using a roll stretching machine, and the resin Each treatment of swelling, dyeing, crosslinking, washing, and drying was sequentially performed on the film to produce a polarizer with a thickness of 12 μm. 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 polarizer to be produced was 45.0%. For the crosslinking treatment, a two-step process was adopted. In the first stage crosslinking treatment, the resin film was stretched 1.2 times while being treated with an aqueous solution of boric acid and potassium iodide at 40°C. The boric acid content in the aqueous solution used in the first step crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage crosslinking treatment, the resin film was stretched 1.6 times while being treated with an aqueous solution of boric acid and potassium iodide at 65°C. The boric acid content in the aqueous solution used in the second step crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. For the washing treatment, a 20°C aqueous potassium iodide solution was used. The content of potassium iodide in the aqueous solution used in the washing treatment was 2.6% by weight. The drying treatment was performed under drying conditions of 70°C and 5 minutes.

(Production of polarizer P1)

A triacetylcellulose (TAC) film (manufactured by Konica Minolta, product name "KC2UA", thickness 25 μm) was bonded to each main surface of the above-produced polarizer using a polyvinyl alcohol-based adhesive. However, in the TAC film bonded to one main surface, a hard coat (7 μm thick) was formed on the main surface opposite to the polarizer side. In this way, a polarizing plate (P1) having the structure of protective layer with hard coat/polarizer/protective layer (without hard coat) was obtained.

<Production of phase difference film (R1)>

(Production of the first retardation film)

26.2 parts by weight of isosorbide (ISB), 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF) 100.5 parts by weight, 1,4-cyclohexanedimethanol (1,4-CHDM) ) 10.7 parts by weight, 105.1 parts by weight of diphenyl carbonate (DPC), and 0.591 parts by weight of cesium carbonate (0.2% by weight aqueous solution) as a catalyst were added to a reaction vessel and dissolved in a nitrogen atmosphere (about 15 minutes). At this time, the temperature of the heating medium in the reaction vessel was set to 150°C, and stirring was performed as necessary. Next, the pressure in the reaction vessel was reduced to 13.3 kPa, and the heat medium temperature was raised to 190°C in 1 hour. Phenol generated as the temperature of the heating medium increased was discharged outside the reaction vessel (the same applies hereinafter). Next, the temperature in the reaction vessel was maintained at 190°C for 15 minutes, and then the pressure in the reaction vessel was changed to 6.67 kPa, and the heating medium temperature was raised to 230°C in 15 minutes. At the point when the stirring torque of the stirrer provided in the reaction vessel increased, the temperature of the heating medium was raised to 250°C in 8 minutes, and the pressure in the reaction vessel was set to 0.200 kPa or less. After reaching a predetermined stirring torque, the reaction was terminated, and the resulting reactant was extruded into water and pelletized. In this way, a polycarbonate resin having 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 obtained polycarbonate resin was 136.6°C, and the reduced viscosity was 0.395 dL/g.

The produced polycarbonate resin pellets were vacuum dried at 80°C for 5 hours, then extruded using a single-screw extruder (Isuzu Chemical Co., Ltd., screw diameter 25 mm, cylinder temperature set at 220°C), T-die (width 200 mm, set temperature 220°C), and cooled. An elongated resin film with a thickness of 120 μm was obtained using a film forming apparatus equipped with a roll (set temperature 120 to 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 stretching ratio of 2.5 times, to obtain a first retardation film.

(Production of the second retardation film)

20 parts by weight of a side-chain liquid crystal polymer (weight average molecular weight 5000) represented by the following formula (I) (where 65 and 35 are mole percent of each constituent unit), a polymerizable liquid crystal (BASF) exhibiting a nematic liquid crystal phase 80 parts by weight of the product, brand name "Paliocolor LC242") and 5 parts by weight of a photopolymerization initiator (manufactured by Chiba Specialty Chemicals, brand name "Irgacure 907") were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. Next, the prepared liquid crystal coating liquid was applied to the surface of the base film, a norbornene-based resin film (manufactured by Nippon Zeon, brand name “Zeonex”) using a bar coater, and then heated and dried at 80°C for 4 minutes. The liquid crystal contained in the coating film was oriented. Next, the coating film was cured by irradiation of ultraviolet rays, and a liquid crystal solidified layer (thickness 0.58 μm), which is a second retardation film, was formed on the base film. The in-plane retardation (Re) of the liquid crystal frozen layer for light with a wavelength of 550 nm is 0 nm, the phase difference (Rth) in the thickness direction is -71 nm (nx = 1.5326, ny = 1.5326, nz = 1.6550), and the liquid crystal fixed layer is nz. The refractive index characteristics of >nx=ny were shown.

(Production of retardation film (R1))

One side of the first retardation film produced above and the liquid crystal solidified layer of the second retardation film were bonded through an adhesive to produce a retardation film (R1).

<Production of circular polarizer with adhesive sheet>

(Production of interlayer adhesive)

A four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser contained 79.9 parts by weight of butylacrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid, and 0.1 part by weight of 4-hydroxybutylacrylate. The monomer mixture was added. Next, 0.1 part 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, and nitrogen gas was introduced while gently stirring to purge the flask with nitrogen. , the liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction proceeded for 7 hours. Next, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30% by weight, and a solution of a (meth)acrylic polymer to be used as an interlayer adhesive was obtained. The weight average molecular weight of the obtained polymer was 2.2 million.

Next, to the solution of the obtained (meth)acrylic polymer, 0.5 parts by weight of trimethylolpropane/tolylene diisocyanate trimer adduct (coating agent, brand name “Coronate L”) and peroxide per 100 parts by weight of solid content of the solution. 0.1 parts by weight of benzoyl peroxide as a cross-linking agent, 0.2 parts by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., brand name “KBM-403), and 0.5 parts by weight of a polyether compound having a reactive silyl group (Kanekase, Cyryl SAT10). Parts by weight were mixed to obtain an adhesive composition PSA1 to be used as an interlayer adhesive for bonding the polarizer (P1) and the retardation film (R1).

(Production of polarizer with interlayer adhesive layer)

The prepared adhesive composition PSA1 was applied to the peeled surface of a 38-μm-thick polyethylene terephthalate (PET) film (Mitsubishi Chemical Polyester Film, MRF38), which is a peeled film whose peeled surface was subjected to silicone treatment, as a layer after drying. It was applied to a thickness of 12 μm and dried at 155°C for 1 minute to form an interlayer adhesive layer. Next, the formed interlayer adhesive layer was transferred to the protective layer (without hard coat) side of the polarizing plate (P1), and a polarizing plate with an interlayer adhesive layer was obtained.

(Production of circular polarizer with adhesive sheet)

On the second retardation film side of the retardation film R1 (the norbornene-based resin film used as the base film when producing the second retardation film was peeled off), each adhesive sheet produced in the examples and comparative examples was separated from the release film. It was transferred and attached. Next, the above-produced polarizing plate with an interlayer adhesive layer was attached to the first retardation film side of the retardation film (R1) through an interlayer adhesive layer, thereby obtaining a circularly polarizing plate with an adhesive sheet. The attachment of the retardation film (R1) and the polarizing plate with an interlayer adhesive layer was carried out 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. .

[Condensation marks (exterior)]

It was visually confirmed whether there were traces of droplets on the surfaces of the peeling film and coating film (adhesive sheet) after main heating, and condensation traces that may occur during production of the adhesive sheet were evaluated as follows.

A: No traces of droplets are visible.

B: Some traces of droplets are visible, but in practical terms, they are at a level that is not problematic.

C: Traces of droplets are visible, which poses a problem in practical terms.

[Level of residue]

The contents of the residual monomer and residual solvent contained in the adhesive sheet formed on the release sheet were determined, and the degree of residual matter was evaluated as follows. Additionally, ppm is based on weight.

A: The remaining monomer content and residual solvent content are both below the measurement limit.

B: The total content of residual monomer and residual solvent is 50ppm or less above the measurement limit.

C: The total content of residual monomer and residual solvent is more than 50 ppm and less than 100 ppm.

D: The total content of residual monomer and residual solvent exceeds 100 ppm.

(Method for measuring residual monomer)

Approximately 0.1 g of the adhesive sheet was collected into a screw tube, 5 mL of acetone was added, and the mixture was shaken overnight. Afterwards, the contents of the screw tube were filtered through a membrane filter (average pore diameter 0.45 μm), and 1 μL of the obtained filtrate was injected into gas chromatography (GC) to determine the content of residual monomer. GC measurement conditions are shown below.

GC device: 6890N from Agilent Technologies

Column: HP-1 (0.250mmϕ×30m, df=1.0μm) manufactured by Agilent Technologies.

Column temperature: maintained at 40°C for 1 minute, then raised to 60°C (rate 5°C/min), then continued to rise to 140°C (rate 10°C/min), and further raised to 300°C (rate 20°C) /min), maintained at 300℃ for 10 minutes

Column flow rate: 2mL/min (He)

Column pressure: constant flow mode (136 kPa)

Inlet temperature: 200℃

Injection volume: 1μL

Injection method: Split (10:1)

Detector: Hydrogen salt ionization detector (FID)

Detector temperature: 250℃

(Method for measuring residual solvent)

Approximately 0.02 g of the adhesive sheet was collected and sealed in a headspace vial with a volume of 20 mL. Next, the vial encapsulated with the adhesive sheet was heated at 150°C for 30 minutes in a headspace sampler (HSS), and 1 mL of the gas phase in the vial after heating was injected into the GC to determine the content of the remaining solvent. The HSS conditions and GC measurement conditions are shown below.

·HSS conditions

HSS device: G1888 from Agilent Technologies

Heating temperature: 150℃

Heating time: 30 minutes

Pressurization time: 0.20 minutes

Loop charging time: 0.20 minutes

Loop equilibration time: 0.05 minutes

Injection time: 0.50 minutes

Sample loop temperature: 160℃

Transfer line temperature: 200℃

・GC measurement conditions (residual solvent)

GC device: 6890N from Agilent Technologies

Column: HP-1 (0.250mmϕ×30m, df=1.0μm) manufactured by Agilent Technologies.

Column temperature: maintained at 40°C for 3 minutes, then raised to 120°C (rate 10°C/min), then continued to rise to 300°C (rate 20°C/min), and held at 300°C for 10 minutes.

Column flow rate: 1mL/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℃

[Comprehensive evaluation]

A comprehensive evaluation of the durability and transparency of the adhesive sheet was conducted as follows.

A: The evaluation of humidification durability is A, and the evaluation of whitening is A to C.

B: The evaluation of humidification durability is B, and the evaluation of whitening is A to C.

C: The evaluation of humidification durability is C, and the evaluation of whitening is A to C.

D: At least one evaluation of humidification durability and whitening is D.

Next, the manufacturing method of each adhesive sheet of Examples and Comparative Examples will be described.

The correspondence between the abbreviated names or names shown in the following description and the compounds is as follows.

BA: n-butylacrylate

BzA: Benzyl acrylate

AA: Acrylic acid

HBA: 4-hydroxybutylacrylate

AIBN: 2,2'-azobisisobutyronitrile

C/L: Trimethylolpropane/tolylene diisocyanate trimer adduct (isocyanate-based crosslinking agent; dosing agent, Coronate L)

TetradC: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (multifunctional epoxy-based crosslinker; Mitsubishi Gas Chemical Co., Ltd., Tetrad C)

KBM403: 3-glycidoxypropyltriethoxysilane (silane coupling agent; manufactured by Shin-Etsu Chemical Co., Ltd., KBM403)

[Production of (meth)acrylic polymer (A)]

(Synthesis Example 1)

94.9 parts by weight of BA, 5.0 parts by weight of AA, and 0.1 part by weight of HBA were added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser. Next, 0.1 part by weight of AIBN was added as a polymerization initiator to 100 parts by weight of the mixture of BA, AA, and HBA, and nitrogen gas was introduced while gently stirring to purge the inside of the flask with nitrogen, and then the liquid temperature in the flask was adjusted to around 55°C. was maintained and the polymerization reaction proceeded for 7 hours. Next, ethyl acetate was added to the obtained reaction liquid to adjust the solid content concentration to 12% by weight, and a solution of (meth)acrylic polymer (A-1) was obtained. The weight average molecular weight (Mw) of the (meth)acrylic polymer (A-1) was 2.2 million. For HSP, δD, δP, and δH of (meth)acrylic polymer (A-1) were 16.75 MPa ^1/2 , 3.49 MPa ^1/2 , and 5.38 MPa ^1/2 , respectively.

(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, 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. For HSP, δD, δP, and δH of the (meth)acrylic polymer (A-2) were 17.05 MPa ^1/2 , 3.49 MPa ^1/2 , and 5.43 MPa ^1/2 , respectively.

(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, 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. For HSP, δD, δP, and δH of (meth)acrylic polymer (A-3) were 17.15 MPa ^1/2 , 3.49 MPa ^1/2 , and 5.44 MPa ^1/2 , respectively.

The types and input amounts of monomers and polymerization initiators used in Synthesis Examples 1 to 3, and the weight average molecular weight (Mw) and distance (Ra) of HSP for the obtained polymer are summarized in Table 1 below. Additionally, δD, δP, and δH of the C/L self-polymer were 20.50 MPa ^1/2 , 12.40 MPa ^1/2 , and 9.60 MPa ^1/2 , respectively.

[Production of adhesive composition and adhesive sheet]

(Production Examples 1 to 8)

As shown in Table 2 below, 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-type adhesive composition.

Next, the adhesive composition produced in each production example was applied to the peeling surface of a 38 μm thick PET film (Mitsubishi Chemical Polyester Film, MRF38), which is a peeling film whose peeling surface was subjected to silicone treatment, to form a coating film. After forming and leaving it to preheat in an environment of 23°C (leaving time (r)), preheating and main heating are continuously performed in an air circulation type constant temperature oven while transporting the base film and the coating film, and the preheating and main heating are carried out to a predetermined thickness. The adhesive sheets of Examples 1 to 25 and Comparative Examples 1 to 5 were formed. The standing time (r) and the conditions of preheating and main heating are shown in Table 3 below. In addition, the temperatures of the preheating and the main heating are the set temperatures of the preheating section and the main heating section in the oven, respectively. The time of preheating and main heating is the time for the base film and the coating film to pass through the preheating section and the main heating section, respectively.

The evaluation results of the produced adhesive sheet are shown in Table 4 below. Additionally, cross-sectional images by TEM of the adhesive sheets of Examples 3, 8, and 9 and Comparative Example 3 are shown in FIGS. 7A to 7D. In addition, the domain states 1 to 5 in Table 4 are respectively as follows.

State 1: Number of evaluation areas in which the first domain exists

State 2: For all first domains, the shortest distance between adjacent first domains

State 3: For every second domain, the shortest distance between adjacent second domains

State 4: Number of evaluation areas where the number of second domains is 10 or less.

State 5: Among all second domains, the ratio of domains whose shortest distance between adjacent second domains is 100 nm or more

As shown in Table 4, the adhesive sheets of the examples were suitable for suppressing dimensional changes and were excellent in transparency and durability compared to the adhesive sheets of the comparative examples.

The adhesive sheet of the present invention can be used, for example, as an optical adhesive sheet used in an optical laminated body and/or an image display device.

Claims (16)

It is an adhesive sheet,
When 10 square evaluation areas with a side of 1.5 μm are arbitrarily set on the cross-section of the adhesive sheet, and an island-like region with a short diameter of 100 nm or more is defined as the first domain, the evaluation area in which the first domain exists The number of is 5 or less,
Having a haze of 0.1% or more,
Adhesive sheet. According to paragraph 1,
An adhesive sheet, wherein for all the first domains observed in the set evaluation area, the shortest distance between the adjacent first domains is 300 nm or more. According to claim 1 or 2,
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, in the set evaluation region, the number of evaluation regions in which the number of the second domains is 10 or less is 3 or more. According to any one of claims 1 to 3,
When an island region having a short diameter of 50 nm or more and less than 100 nm is defined as a second domain, for all the second domains observed in the set evaluation region, the shortest distance between the adjacent second domains is Adhesive sheet, 150 nm or longer. According to any one of claims 1 to 4,
When an island region having a short diameter of 50 nm or more and less than 100 nm is defined as a second domain, among all the second domains observed in the set evaluation region, the shortest distance between the adjacent second domains is 100 nm. An adhesive sheet wherein the ratio of the second domains is 50% or more. According to any one of claims 1 to 5,
An adhesive sheet having a storage modulus (G') (25°C) of 0.15 MPa or more. According to any one of claims 1 to 6,
An adhesive sheet having a storage modulus (G') (25°C) of less than 0.5 MPa. According to any one of claims 1 to 7,
A pressure-sensitive adhesive sheet formed from an adhesive composition containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate-based crosslinking agent (B). According to clause 8,
An adhesive sheet wherein the first domain contains a polymer of the isocyanate-based crosslinking agent (B). According to clause 8 or 9,
A pressure-sensitive adhesive sheet, wherein the amount of the isocyanate-based crosslinking agent (B) in the pressure-sensitive adhesive composition is 1.5 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A). According to any one of claims 8 to 10,
An adhesive sheet in which the isocyanate-based crosslinking agent (B) is tolylene diisocyanate-based. According to any one of claims 8 to 11,
An adhesive sheet in which the (meth)acrylic polymer (A) contains a structural unit derived from an aromatic ring-containing monomer. According to any one of claims 8 to 12,
An adhesive sheet in which the (meth)acrylic polymer (A) contains a structural unit derived from a hydroxyl group-containing monomer at a content of 1% by weight or less. According to any one of claims 8 to 13,
An adhesive sheet wherein the adhesive composition is a solvent type. An optical laminate comprising the adhesive sheet of any one of claims 1 to 14 and an optical film. An image display device comprising the optical laminate of claim 15.