JP7369887B2 - Adhesive compositions, adhesive sheets, optical laminates, image display panels and image display devices - Google Patents

Description

The present invention relates to an adhesive composition, an adhesive sheet, an optical laminate, an image display panel, and an image display device.

In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) have rapidly become popular. These various image display devices have a laminated structure of an image display cell such as a liquid crystal cell or an EL light emitting element, and an optical laminate including an optical film such as a polarizing plate and an adhesive sheet. Adhesive sheets are mainly used for bonding between optical films included in an optical laminate and for bonding an image display cell and an optical laminate. Patent Document 1 describes a pressure-sensitive adhesive composition containing a (meth)acrylic polymer having a structural unit derived from a polar group-containing monomer such as 2-methoxyethyl acrylate, and a pressure-sensitive adhesive composition formed from the pressure-sensitive adhesive composition. An adhesive sheet is disclosed.

JP2013-32428A

In an image display device, static electricity is generated during manufacture, for example, when an optical laminate is bonded to an image display cell via an adhesive sheet, or during use, for example, when a user touches the image display device. When an image display device is charged with this static electricity, problems such as poor display may occur. When using an image display device in an environment where static electricity is particularly likely to occur, for example in an environment where other electronic devices are present such as inside a vehicle, adhesive It is possible to adjust the surface resistance value of the adhesive sheet to a low value by blending a conductive agent into the agent composition. However, if the blending amount of the conductive agent is excessively large, the optical properties may deteriorate due to the precipitation of the conductive agent and the durability of the adhesive sheet may decrease when the conductive agent is exposed to high-temperature environments such as inside a vehicle in the summer. etc. tend to occur.

The present invention provides a pressure-sensitive adhesive composition that achieves a low surface resistance value and is suitable for use in optical laminates in environments where high temperatures are considered, and a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition. purpose.

The present invention
Contains a polymer (A) having a polyether structure as a main component,
further comprising a conductive agent and a radical scavenger,
The present invention provides a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive sheet has a surface resistance value of 1×10 ¹⁰ Ω/□ or less when formed into a pressure-sensitive adhesive sheet.

From another aspect, the present invention includes:
A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition described above is provided.

From another aspect, the present invention includes:
The above adhesive sheet,
optical film,
An optical laminate comprising:

From another aspect, the present invention includes:
An image display panel including the above optical laminate is provided.

From another aspect, the present invention includes:
An image display device including the above image display panel is provided.

From another aspect, the present invention includes:
A pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a polymer (B),
The relative dielectric constant of the polymer (B) at a frequency of 100 kHz is 5.0 or more,
After heating the adhesive sheet at 105° C. for 120 hours, the adhesive sheet contains 1000 ppm or less of formic acid based on mass.

From another aspect, the present invention includes:
An optical laminate including an adhesive sheet and an optical film,
The optical film is a polarizing plate containing a polarizer,
After heating the optical laminate at 105° C. for 120 hours, the polarizing plate provides an optical laminate containing 70 ppm or less formic acid on a mass basis.

According to the present invention, there is provided a pressure-sensitive adhesive composition that achieves a low surface resistance value and is suitable for use in optical laminates in environments where high temperatures are considered, and a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition. Can be provided.

FIG. 1 is a cross-sectional view schematically showing an example of the adhesive sheet of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of the optical laminate of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of the optical laminate of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of the optical laminate of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of the optical laminate of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of the optical laminate of the present invention. FIG. 7 is a cross-sectional view schematically showing an example of the image display panel of the present invention. FIG. 8 is a cross-sectional view schematically showing an example of the image display panel of the present invention. FIG. 9 is a cross-sectional view schematically showing an example of the image display panel of the present invention.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be implemented with arbitrary modifications without departing from the gist of the present invention.

(Embodiment 1)
[Adhesive composition]
The adhesive composition (I) of this embodiment contains a polymer (A) having a polyether structure as a main component, and further contains a conductive agent. According to studies by the present inventors, the polyether structure in the polymer (A) can promote the ionization of the conductive agent contained in the adhesive composition (I), and the ionization of the conductive agent is This can contribute to lowering the surface resistance value of adhesive sheets formed from materials.

Furthermore, further studies have shown that (i) when a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a polymer (A) having a polyether structure as a main component is used in an optical laminate, unnecessary (ii) coloration is often seen when polarizing plates are included in optical laminates; and (iii) coloration is caused by high temperatures caused by polypropylene. It has been found that the mechanism is presumed to be that radicals generated due to the ether structure move to the optical film and act on the polymer contained in the optical film. As an example of the action of radicals on polymers, polyenization of polyvinyl alcohol (PVA), which is a typical polymer contained in polarizers, can be considered. Polyenization of PVA is a phenomenon in which multiple carbon-carbon unsaturated bonds are generated in the main chain of PVA and the conjugated structure is extended, and the extension of the conjugated structure causes absorption in the visible light range, resulting in coloration (typically is thought to exhibit a red color). Polyenization of PVA can be explained as a phenomenon in which the crosslinked structure with boric acid disappears due to heat-induced hydrolysis, exposing many terminal OH groups of PVA, and a dehydration condensation reaction between the exposed OH groups progresses. Moreover, this dehydration condensation reaction is presumed to be a radical reaction. In addition, it is considered that the progress of radical reactions in the optical film at high temperatures, not limited to PVA in the polarizer, can cause changes in the optical properties of the optical film, such as coloring. Note that radicals generated due to the polyether structure include radicals generated due to the involvement of other components (e.g., polymerization initiators, crosslinking agents, antioxidants, etc.) starting from the radicals generated from the polyether structure. may be included.

Adhesive composition (I) further contains a radical scavenger. The radical scavenger can limit the amount of radicals generated at high temperatures in the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (I). The pressure-sensitive adhesive composition (I), which has a limited amount of radical generation under high temperatures when formed into a pressure-sensitive adhesive sheet, is suitable for use in optical laminates in environments where high temperatures are a consideration.

When a pressure-sensitive adhesive sheet is formed from the pressure-sensitive adhesive composition (I), the formed pressure-sensitive adhesive sheet has a surface resistance value of 1×10 ¹⁰ Ω/□ or less. The surface resistance value is 5×10 ⁹ Ω/□ or less, 1×10 ⁹ Ω/□ or less, 8×10 8 Ω/□ or less, 6×10 ⁸ Ω/□ or less, 5× ^{10 8 Ω} /□ or less, It may be 4×10 ⁸ Ω/□ or less, 3×10 ⁸ Ω/□ or less, or even 2×10 ⁸ Ω/□ or less. The lower limit of the surface resistance value is, for example, 1×10 ⁶ Ω/□ or more, and may be 1×10 ⁷ Ω/□ or more. The pressure-sensitive adhesive composition (I) having a surface resistance value within the above range when formed into a pressure-sensitive adhesive sheet is suitable for use in an environment where static electricity is likely to occur, for example, inside a vehicle.

<Polymer (A)>
Examples of the polymer (A) are (meth)acrylic polymers, urethane polymers, silicone polymers, and rubber polymers. However, the polymer (A) is not limited to the above examples as long as it has a polyether structure. Polymer (A) is preferably a (meth)acrylic polymer. In other words, the adhesive composition (I) may contain a (meth)acrylic polymer as a main component. In other words, the adhesive composition (I) may be an acrylic adhesive composition. The main component means the component with the highest content in the composition. The content of the main component is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 75% by weight or more, or even 80% by weight or more. In this specification, the (meth)acrylic polymer refers to a polymer having a structural unit derived from a (meth)acrylic monomer such as (meth)acrylate. The content of structural units derived from (meth)acrylic monomers in the (meth)acrylic polymer is, for example, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more. % or more, 85 weight % or more, 90 weight % or more, or even 95 weight % or more. The (meth)acrylic polymer may consist only of structural units derived from (meth)acrylic monomers. (Meth)acrylic means acrylic and methacrylic. (Meth)acrylate means acrylate and methacrylate.

Polymer (A) has a polyether structure. A polyether structure is a structure containing at least two ether groups (-O-). The polyether structure may be linear or branched. An example of a polyether structure includes an alkyl group that may be linear or branched, and at least two ether groups. The polymer (A) may have a polyether structure in the main chain or in the side chain, and preferably has the polyether structure in the side chain. The polymer (A) may be a (meth)acrylic polymer having a polyether structure in its side chain.

The polymer (A) may have a structural unit having a polyether structure. In the structural unit, the polyether structure may be located in the main chain or in the side chain, and is preferably located in the side chain. The polymer (A) may have a structural unit derived from a (meth)acrylic monomer having a polyether structure in its side chain.

An example of the polymer (A) having a polyether structure in its side chain has a structural unit derived from a monomer shown in the following formula (1). R ¹ in formula (1) is a hydrogen atom or a methyl group. R ² in formula (1) is an alkyl group which may be linear or branched, and is preferably a linear alkyl group. Examples of R ² are methyl and ethyl groups. n is an integer of 1 to 15, preferably an integer of 1 to 10, more preferably an integer of 1 to 5. When n is 1, the monomer of formula (1) contains two ether groups, including the "-O-" of the COO group. The monomer of formula (1) is one type of (meth)acrylic monomer, and more specifically, one type of (meth)acrylate monomer. Focusing on the R ² O group at the end of the side chain, the monomer of formula (1) is also a type of alkoxy group-containing (meth)acrylate monomer. The structural unit derived from the monomer of formula (1) has a polyether structure in its side chain.

Examples of the monomer of formula (1) are 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, and methoxytriethylene glycol (meth)acrylate. ) acrylate and methoxypolyethylene glycol (meth)acrylate, preferably 2-methoxyethyl acrylate (MEA). The structural unit derived from the monomer of formula (1) can particularly contribute to lowering the surface resistance value in the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (I).

The content of structural units having a polyether structure (for example, structural units derived from the monomer of formula (1)) in the polymer (A) is, for example, 15% by weight or more, 20% by weight or more, 25% by weight 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight The content may be 80% by weight or more, 85% by weight or more, 90% by weight or more, or even 95% by weight or more. The upper limit of the content may be, for example, 100% by weight or less, 99.5% by weight or less, or even 99% by weight or less.

The polymer (A) may have one or more structural units derived from the following monomer (A2). In addition, the monomer (A2) shown below can be copolymerized with the monomer of formula (1).

An example of the monomer (A2) is a (meth)acrylic monomer having an alkyl group having 1 to 30 carbon atoms in its side chain. The alkyl group may be linear or branched. Examples of (meth)acrylic monomers having an alkyl group in the side chain are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. , s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate 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 Acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate , heptadecyl (meth)acrylate and octadecyl (meth)acrylate. The content of the structural unit derived from the (meth)acrylic monomer having an alkyl group in the side chain in the polymer (A) is, for example, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less. % or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, even 5% by weight or less, even 0% by weight (without having the constituent unit) (even if) good.

Another example of the monomer (A2) is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth)acrylic monomer. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl ( meth)acrylate, hydroxyalkyl (meth)acrylates such as 10-hydroxydecyl (meth)acrylate and 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. From the viewpoint of improving the durability of the adhesive sheet formed from the adhesive composition (I), 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 4-hydroxybutyl (meth)acrylate is preferred. Acrylates are more preferred. The content of the structural unit derived from the hydroxyl group-containing monomer in the polymer (A) is, for example, 1 to 5% by weight, and may be 3% by weight or less, or even 2% by weight or less. The polymer (A) does not need to have a structural unit derived from a hydroxyl group-containing monomer.

The monomer (A2) may be an aromatic ring-containing monomer, a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. The aromatic ring-containing monomer may be an aromatic ring-containing (meth)acrylic monomer. Examples of aromatic ring-containing monomers are phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, and hydroxyethylated β- They are naphthol (meth)acrylate and biphenyl (meth)acrylate. 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, N-methyl(meth)acrylamide, N- Butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylol-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide, aminoethyl (meth)acrylamide, mercaptomethyl Acrylamide monomers such as (meth)acrylamide and mercaptoethyl (meth)acrylamide; N-acryloyl heterocycles 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.

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

The total content of structural units derived from aromatic ring-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, and polyfunctional monomers in polymer (A) is , preferably 20% by weight or less, more preferably 10% by weight or less, still more preferably 8% by weight or less. When the polymer (A) has the structural unit, the total content is, for example, 0.01% by weight or more, and may be 1% by weight or more, 2% by weight or more, or even 3% by weight or more. Polymer (A) does not need to have these structural units. In particular, in the polymer (A), the content of the structural unit derived from the carboxyl group-containing monomer may be less than 0.1% by weight, and even if it is 0% by weight (without having the structural unit). Even if you don't have one)

Examples of other monomers (A2) include nitrile group-containing (meth)acrylates such as (meth)acrylonitrile; epoxy group-containing monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; vinyl Sulfonic acid group-containing monomers such as sodium sulfonate; phosphate group-containing monomers; alicyclic hydrocarbon groups such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylic acid esters; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyltoluene; olefins or dienes such as ethylene, propylene, butadiene, isoprene and isobutylene; Vinyl ethers such as alkyl ethers; and vinyl chloride.

The total content of structural units derived from the other monomers (A2) in the polymer (A) is, for example, 30% by weight or less, may be 10% by weight or less, and is 0% by weight ( Preferably, it does not have the structural unit.

Polymer (A) can be formed by polymerizing one or more of the above-mentioned monomers by a known method. A monomer and a partial polymer of the monomer may be polymerized. Polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy ray polymerization. From the viewpoint of being able to form a pressure-sensitive adhesive sheet with excellent optical transparency, solution polymerization and active energy ray polymerization are preferred. It is preferable to carry out the polymerization while avoiding contact between the monomer and/or the partially polymerized product and oxygen. For this purpose, for example, polymerization may be carried out in an atmosphere of an inert gas such as nitrogen, or oxygen may be removed using a resin film or the like. Polymerization in a blocked state can be employed. The polymer (A) to be formed may be a random copolymer, a block copolymer, a graft copolymer, or the like.

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

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; cyclohexane, Alicyclic hydrocarbons such as 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 kinds of solvents.

Examples of the polymerization initiator used in solution polymerization include an azo polymerization initiator, a peroxide polymerization initiator, and a redox polymerization initiator. Examples of the peroxide polymerization initiator include dibenzoyl peroxide and t-butyl permaleate. Among these, the azo polymerization initiator disclosed in JP-A No. 2002-69411 is preferred. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, and 2,2'-azobis(2-methylpropion). 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 for active energy ray polymerization include, for example, ionizing radiation such as α rays, β rays, γ rays, neutron beams, and electron beams, and ultraviolet rays. The active energy rays are preferably ultraviolet rays. Polymerization by irradiation with ultraviolet light is also called photopolymerization. The polymerization system for active energy ray polymerization typically contains a photopolymerization initiator. The polymerization conditions for active energy polymerization are not limited as long as the polymer (A) is formed.

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

Examples of benzoin ether photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and anisole methyl. It is ether. Examples of acetophenone photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloro. It is acetophenone. Examples of the α-ketol photopolymerization initiator are 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. The aromatic sulfonyl chloride photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. The photoactive oxime photopolymerization initiator is, for example, 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. The benzoin-based photopolymerization initiator is, for example, benzoin. The benzylic photopolymerization initiator is, for example, benzyl. Examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. The ketal photopolymerization initiator is, for example, benzyl dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, 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 part by weight, based on 100 parts by weight of the total amount of monomers.

The weight average molecular weight (Mw) of the polymer (A) is, for example, 1 million to 3 million, preferably 1.8 million to 3 million. When the weight average molecular weight of the polymer (A) is 1 million to 3 million, cracks in the pressure-sensitive adhesive sheet can be suppressed, and an increase in viscosity and occurrence of gelation tend to be suppressed. The weight average molecular weight (Mw) of the polymer in this specification is a value (in terms of polystyrene) based on measurement by GPC (gel permeation chromatography).

The glass transition temperature (Tg) of the polymer (A) is, for example, -50°C or lower, preferably -52°C or lower, and more preferably -55°C or lower. The lower limit of Tg of polymer (A) is, for example, -75°C. The Tg of the polymer (A) is the value obtained by determining the Tg of each monomer forming the constituent units of the polymer (A) when it is made into a homopolymer, and averaging these Tg by considering the content of the constituent units. It is.

The content of the polymer (A) in the adhesive composition (I) is, in terms of solid content, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, and even 80% by weight. It may be more than that. The upper limit of the content may be, for example, 99% by weight or less, 97% by weight or less, or even 95% by weight or less.

<Conductive agent>
The adhesive composition (I) further includes a conductive agent (antistatic agent). The adhesive composition (I) may contain one or more conductive agents. Examples of conductive agents are ionic compounds such as salts. The ionic compound may be an ionic liquid that is liquid at room temperature (25° C.).

Examples of ionic compounds are inorganic and organic cation salts. Examples of inorganic cation salts are inorganic cation-anion salts. Examples of cations included in inorganic cation salts are alkali metal ions. The alkali metal ion is, for example, a lithium ion, a sodium ion, or a potassium ion, and preferably a lithium ion. The inorganic cation salt may be a lithium salt.

Examples of anions included in the inorganic cation salt are Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ -, ClO ₄ ^{- ,} NO ₃ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ ^- , SbF ₆ -, NbF ₆ ^- , TaF ₆ ^{- ,} (CN) ₂ N ^{- ,} _{C4F9SO3- , C3F7COO- ,} ( _{CF3SO2 ) (CF3CO)N-, -O3S(CF2)3SO3- ,} ^{and the following} _{general formula} ⁽ _{a )} It is an anion represented by ~(d).
(a) (C _n F _2n+1 SO ₂ ) ₂ N ^- (n is an integer from 1 to 10)
(b) CF ₂ (C _m F _2m SO ₂ ) ₂ N ^- (m is an integer from 1 to 10)
(c) ^- O ₃ S (CF ₂ ) _l SO ₃ ^- (l is an integer from 1 to 10)
(d) (C _p F _2p+1 SO ₂ )N ^- (C _q F _2q+1 SO ₂ ) (p and q are integers from 1 to 10 independently)

The anion contained in the inorganic cation salt is preferably a fluorine-containing anion, more preferably a fluorine-containing imide anion. An example of a fluorine-containing imide anion is an imide anion having a perfluoroalkyl group. More specific examples of fluorine-containing imide anions are (CF ₃ SO ₂ ) (CF ₃ CO) N ^- and anions represented by the above general formula (a), (b) or (d), Preferred are (perfluoroalkylsulfonyl)imides represented by the general formula (a) such as (CF ₃ SO ₂ ) ₂ N ^- and (C ₂ F ₅ SO ₂ ) ₂ N ^- , and more preferred are (CF ₃ SO _{2 )} ) ₂ N ^- bis(trifluoromethanesulfonyl)imide. An example of a preferred inorganic cation salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

Examples of organic cation salts are organic cation-anion salts. An example of a cation included in an organic cation salt is an organic onium containing an organic group. Examples of onium included in organic onium include nitrogen-containing onium, sulfur-containing onium, and phosphorus-containing onium, and preferably nitrogen-containing onium and sulfur-containing onium. Examples of nitrogen-containing oniums include ammonium cations, piperidinium cations, pyrrolidinium cations, pyridinium cations, cations with a pyrroline skeleton, cations with a pyrrole skeleton, imidazolium cations, tetrahydropyrimidinium cations, and dihydropyrimidinium cations. , pyrazolium cation, and pyrazolinium cation. An example of a sulfur-containing onium is a sulfonium cation. An example of a phosphorus-containing onium is a phosphonium cation. Examples of organic groups included in organic onium are alkyl groups, alkoxyl groups, and alkenyl groups. Specific examples of preferred organic oniums are tetraalkylammonium cations (eg, tributylmethylammonium cations), alkylpiperidinium cations, and alkylpyrrolidinium cations.

Examples of anions contained in organic cation salts are the same as those contained in inorganic cation salts. Examples of preferred organic cation salts are 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, trimethylbutylammonium bis(trifluoromethanesulfonyl)imide.

The conductive agent may be a combination of an inorganic cation salt and an organic cation salt.

The amount of the conductive agent in the adhesive composition (I) is, for example, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more based on 100 parts by weight of the polymer (A). , and even 4 parts by weight or more. The upper limit of the blending amount is, for example, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, less than 10 parts by weight, 9 parts by weight or less, 8 parts by weight or less, based on 100 parts by weight of the polymer (A). It may be 7 parts by weight or less, or even 6 parts by weight or less.

<Radical scavenger>
Adhesive composition (I) further contains a radical scavenger. Examples of radical scavengers include various antioxidants such as hindered phenol, hindered amine, phosphite, phenol and thioether antioxidants, and blends of these systems.

Types of antioxidants include, for example, radical chain inhibitors and peroxide decomposers.

The antioxidant may be at least one selected from hindered phenol, hindered amine, and phosphite.

The hindered phenolic antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to a carbon atom on an aromatic ring to which an OH group of phenol is bonded. Examples of hindered phenolic antioxidants are dibutylated hydroxytoluene (BHT); anox1098, Irganox1135, Irganox1330, Irganox1726, Irganox1425WL, Irganox1520L, Irganox245, Irganox245FF, Irganox259 , Irganox3114, Irganox565, and Irganox295 (all are trade names and manufactured by BASF).

The hindered amine antioxidant may have at least one hindered piperidine group in one molecule. Examples of hindered amine antioxidants are Adekastab LA-63, Adekastab LA-63P, Adekastab LA-52, and Adekastab LA-57 (all trade names, manufactured by ADEKA).

Examples of phosphite-based antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, and phenyl diisodecyl phosphite; and ADEKA STAB 2112, ADEKA STAB 2112RG, ADEKA STAB 1178, and ADEKA STAB 3010 (all trade names, manufactured by ADEKA). It is.

Examples of phenolic antioxidants are monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of monophenolic antioxidants are 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin-β-(3 , 5-di-t-butyl-4-hydroxyphenyl) propionate. Examples of bisphenol antioxidants are 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'- Thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3 -t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of polymeric phenolic antioxidants include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6 -tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, Bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid] glycol ester, 1,3,5-tris(3',5'-di-t-butyl- 4'-hydroxybenzyl)-S-triazine-2,4,6-(1H, 3H, 5H)trione and tocophenol.

Examples of thioether antioxidants are ADEKA STAB AO-503 and ADEKA STAB AO-26 (both are trade names and manufactured by ADEKA).

The molecular weight of the radical scavenger (e.g. antioxidant) may be 1000 or less, 900 or less, 850 or less, 800 or less, 700 or less, 600 or less, 500 or less, 450 or less, or even 400 or less. good. The lower limit of the molecular weight is, for example, 100 or more. According to studies by the present inventors, a radical scavenger having a molecular weight within the above range is particularly suitable for suppressing the amount of radical generation in a pressure-sensitive adhesive sheet formed from pressure-sensitive adhesive composition (I).

The radical scavenger (eg, antioxidant) may be liquid at room temperature (25° C.).

The amount of the radical scavenger in the adhesive composition (I) is, for example, 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more based on 100 parts by weight of the polymer (A). , 0.4 parts by weight or more, and even 0.5 parts by weight or more. The upper limit of the blending amount is, for example, 15 parts by weight or less, 10 parts by weight or less, 7 parts by weight or less, 5 parts by weight or less, less than 5 parts by weight, 4 parts by weight or less, based on 100 parts by weight of the polymer (A). The amount may be 3 parts by weight or less, or even 2 parts by weight or less.

<Additives>
The adhesive composition (I) may further contain materials other than the polymer (A), the conductive agent, and the radical scavenger. Examples of such materials are additives. Examples of additives are crosslinking agents, silane coupling agents, colorants such as pigments and dyes, ultraviolet absorbers, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, rework improvers, and softeners. These include powders, particles, and foil-like materials such as agents, polymerization inhibitors, rust preventives, inorganic fillers, organic fillers, and metal powders. The additives can be blended in a total amount of, for example, 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 3 parts by weight or less, based on 100 parts by weight of the polymer (A).

Examples of crosslinking agents are organic crosslinking agents and polyfunctional metal chelates. Examples of organic crosslinking agents are isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents. The organic crosslinking agent and the polyfunctional metal chelate can be used for both solvent-type and active energy ray-curable pressure-sensitive adhesive compositions (I). When the adhesive composition (I) is a solvent type, the crosslinking agent is preferably a peroxide-based crosslinking agent or an isocyanate-based crosslinking agent. A peroxide-based crosslinking agent and an isocyanate-based crosslinking agent may be used together. The adhesive composition (I) may contain an isocyanate crosslinking agent, a peroxide crosslinking agent, or both an isocyanate crosslinking agent and a peroxide crosslinking agent. Good too.

Examples of isocyanate-based crosslinking agents include aromatic isocyanate compounds such as tolylene diisocyanate, chlorphenylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, and polymethylene polyphenylisocyanate; cyclopentylene diisocyanate, cyclohexylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and Alicyclic isocyanate compounds such as isophorone diisocyanate; aliphatic isocyanate compounds such as butylene diisocyanate, tetramethylene diisocyanate and hexamethylene diisocyanate. Isocyanate-based crosslinking agents are compounds obtained by adding the above-mentioned isocyanate compounds to polyhydric alcohol compounds such as trimethylolpropane (adducts); A compound subjected to an addition reaction with a polyol; a derivative of the above-mentioned isocyanate compound such as an isocyanurate compound may also be used. Specific examples of the derivatives include trimethylolpropane/tolylene diisocyanate trimer adduct (for example, Coronate L, manufactured by Tosoh Corporation), trimethylolpropane/hexamethylene diisocyanate trimer adduct (for example, Coronate HL, manufactured by Tosoh Corporation). ), isocyanurate of hexamethylene diisocyanate (for example, Coronate HX manufactured by Tosoh Corporation).

When the adhesive composition (I) contains an isocyanate-based crosslinking agent, the amount thereof is, for example, 0.1 to 10 parts by weight, and 0.2 to 5 parts by weight, based on 100 parts by weight of the polymer (A). , 0.25 to 3 parts by weight, 0.3 to 1 part by weight, or even 0.3 to 0.5 parts by weight.

Examples of peroxide-based crosslinking agents include di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxy Neodecanoate, t-hexyl peroxy pivalate, t-butyl peroxy pivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2 -ethylhexanoate, di(4-methylbenzoyl) peroxide, benzoyl peroxide, t-butylperoxyisobutyrate, and 1,1-di(t-hexylperoxy)cyclohexane. The peroxide-based crosslinking agent may be benzoyl peroxide because it has excellent crosslinking reaction efficiency.

When the adhesive composition (I) contains a peroxide-based crosslinking agent, the amount thereof is, for example, 0.005 to 5 parts by weight, and 0.01 to 3 parts by weight, based on 100 parts by weight of the polymer (A). parts by weight, 0.05-2 parts by weight, 0.07-1 parts by weight, 0.07-0.5 parts by weight, 0.07-0.3 parts by weight, and even 0.07-0.2 parts by weight. It may be.

Examples of silane coupling agents are 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl Epoxy group-containing silane coupling agents such as trimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3 Silane coupling agents containing amino groups such as -dimethylbutylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane; ) Acrylic group-containing silane coupling agent; isocyanate group-containing silane coupling agent such as 3-isocyanatepropyltriethoxysilane.

When the adhesive composition (I) contains a silane coupling agent, the amount thereof is, for example, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, based on 100 parts by weight of the polymer (A). The amount may be 0.5 part by weight or less, 0.2 part by weight or less, 0.1 part by weight or less, or even 0.05 part by weight or less. Adhesive composition (I) may not contain a silane coupling agent.

The type of the adhesive composition (I) is, for example, an emulsion type, a solvent type (solution type), an active energy ray-curable type (photocurable type), or a heat melt type (hot melt type). From the viewpoint of being able to form a pressure-sensitive adhesive sheet with excellent durability, the pressure-sensitive adhesive composition (I) may be a solvent type or an active energy ray-curable type, or may be 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 composition (I) can be used, for example, in an optical laminate. In other words, the adhesive composition (I) may be used for optical laminates. However, the uses of adhesive composition (I) are not limited to the above examples.

(Embodiment 2)
[Adhesive composition]
The adhesive composition (II) of this embodiment contains a polymer (B). The adhesive composition (II) may contain the polymer (B) as a main component. "Principal component" has the meaning described above. Here, the dielectric constant of the polymer (B) at a frequency of 100 kHz is 5.0 or more. In addition, after heating the adhesive sheet formed from the adhesive composition (II) at 105° C. for 120 hours, the adhesive sheet contains 1000 ppm or less formic acid on a mass basis. When the content of formic acid is as low as this, the optical laminate is unlikely to be colored even after being exposed to a high-temperature environment.

According to the studies of the present inventors, (iv) when a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a polymer having a dielectric constant of 5.0 or more at a frequency of 100 kHz is used in an optical laminate, It was later discovered that unnecessary coloration, particularly red coloration, tends to occur, and (v) coloration is often seen when a polarizing plate is included in the optical laminate. It has been found that the cause of this is, for example, that the acid contained in the pressure-sensitive adhesive sheet acts on the polymer contained in the optical film. In addition, the present inventors discovered that the acid that acts on the polymer contained in the optical film is formic acid. As an example of the effect of formic acid on the polymer, conversion of PVA contained in the polarizer into a polyene can be considered. It is presumed that in PVA, exposed OH groups are protonated by formic acid, and a dehydration condensation reaction proceeds. In addition, it is thought that the progress of the above-mentioned reaction by formic acid in the optical film under high temperature, not limited to PVA in the polarizer, can bring about changes in the optical properties of the optical film, such as coloring.

As described above, by heating the optical laminate, formic acid can be generated in the members constituting the optical laminate. Examples of members of the optical laminate that can generate formic acid include adhesive sheets, polarizing plates, OCA (optical clear adhesive) layers, and protective films. The OCA layer is, for example, an adhesive layer formed on the surface of the polarizing plate opposite to the adhesive sheet in the optical laminate. In other words, the polarizing plate may be placed between the adhesive sheet and the OCA layer. The OCA layer is a layer containing an optically transparent adhesive. The material of the adhesive included in the OCA layer is not particularly limited, and for example, (meth)acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine polymer, rubber polymer, etc. are used as the base polymer. include. The protective film is, for example, a film formed on the surface of a polarizer. Details of the protective film will be described later. For example, formic acid may be generated by hydrolysis of the protective film.

After heating the adhesive sheet formed from the adhesive composition (II) at 105 ° C. for 120 hours, the content of formic acid contained in the adhesive sheet is 800 ppm or less, 500 ppm or less, 200 ppm or less, 100 ppm or less, on a mass basis. It may be 70 ppm or less, 50 ppm or less, 25 ppm or less, 5 ppm or less, 2.5 ppm or less, or even less than 2.5 ppm. The lower limit of the content of formic acid is not particularly limited, and is, for example, 0 ppm or more on a mass basis.

The dielectric constant P of the polymer (B) at a frequency of 100 kHz is 5.0 or more. When the dielectric constant P is as high as this, even when an optical film with a low dielectric constant, especially a polarizing film and an adhesive sheet are used in combination, a decrease in the sensitivity of the touch sensor included in the image display device is suppressed. There is a tendency to do so.

The dielectric constant P can be measured by the following method. First, a test piece with a thickness of 30 μm made only of polymer is prepared. Regarding this test piece, the relative dielectric constant at a frequency of 100 kHz is measured by an automatic balancing bridge method (transformer bridge method) in accordance with JIS K6911:1995. The obtained measured value can be regarded as the relative dielectric constant P. Details of the measurement conditions for the dielectric constant are as follows.
・Measurement conditions Measurement method: Capacitive method (Equipment: 4294A Precision Impedance Analyzer manufactured by Agilent Technologies)
Electrode configuration: Aluminum plate with a diameter of 12.1 mm and a thickness of 0.5 mm Counter electrode: 3 oz copper plate Measurement environment: 23 ± 1°C, 52 ± 1% RH

The dielectric constant P may be 6.0 or more, 6.5 or more, 6.8 or more, 7.0 or more, 7.3 or more, or even 7.5 or more. The upper limit of the dielectric constant P is not particularly limited, and is, for example, 10.0 or less.

The polymer (B) contained in the adhesive composition (II) may be, for example, the polymer (A) described in Embodiment 1.

The adhesive composition (II) may further contain a radical scavenger and a peroxide-based crosslinking agent.

The radical scavenger may be an antioxidant. As the radical scavenger, for example, the radical scavenger described in Embodiment 1, that is, various antioxidants can be used. In adhesive composition (II), the molecular weight of the radical scavenger (for example, antioxidant) may be 1000 or more. The upper limit of the molecular weight is, for example, 1,500 or less. According to studies by the present inventors, a radical scavenger having a molecular weight within the above range is particularly suitable for suppressing the amount of formic acid generated in a pressure-sensitive adhesive sheet formed from pressure-sensitive adhesive composition (II). The preferred amount of the radical scavenger in the adhesive composition (II) is as described in Embodiment 1.

As the peroxide-based crosslinking agent, for example, the peroxide-based crosslinking agent described in Embodiment 1 can be used. The preferred amount of the peroxide crosslinking agent in the adhesive composition (II) is as described in Embodiment 1. Excessive blending of a peroxide-based crosslinking agent may promote polyenization of PVA contained in the polarizer. Polyenation may involve reactants of reactions involving peroxide-based crosslinkers, such as benzoic acid. When the pressure-sensitive adhesive composition (II) contains a peroxide-based crosslinking agent, the blending amount within the above range is particularly suitable for suppressing discoloration.

The adhesive composition (II) may further contain an isocyanate-based crosslinking agent in addition to the peroxide-based crosslinking agent. Examples of the isocyanate-based crosslinking agent are as described in Embodiment 1. The preferred amount of the isocyanate crosslinking agent in the adhesive composition (II) is also as explained in Embodiment 1.

The adhesive composition (II) may further contain materials other than the polymer (A), the radical scavenger, and the peroxide-based crosslinking agent. An example of such a material is a conductive agent (antistatic agent). The adhesive composition (II) may contain one or more types of conductive agents. Examples of conductive agents are ionic compounds such as salts. The ionic compound may be an ionic liquid that is liquid at room temperature (25° C.). As the conductive agent, the conductive agent described in Embodiment 1 can be used. Examples of conductive agents are ionic compounds such as salts. Examples of ionic compounds are inorganic and organic cation salts. The conductive agent may contain an organic cation salt. The conductive agent may be an organic cation salt. The blending amount of the conductive agent in the adhesive composition (II) is as described in Embodiment 1.

The adhesive composition (II) may further contain materials other than the polymer (A), the radical scavenger, the peroxide crosslinking agent, and the conductive agent. Examples of such materials are additives. Examples of additives are as described in Embodiment 1.

The type of the adhesive composition (II) is, for example, an emulsion type, a solvent type (solution type), an active energy ray-curable type (photocurable type), or a heat melt type (hot melt type). From the viewpoint of being able to form a pressure-sensitive adhesive sheet with excellent durability, the pressure-sensitive adhesive composition (II) may be a solvent type or an active energy ray-curable type, or may be a solvent type. The solvent-type adhesive composition (II) does not need to contain a photocuring agent such as an ultraviolet curing agent.

The adhesive composition (II) can be used, for example, in optical laminates. In other words, the adhesive composition (II) may be used for optical laminates. However, the use of adhesive composition (II) is not limited to the above example.

In addition, after heating the adhesive sheet formed from adhesive composition (II), the content of acetic acid contained in the adhesive sheet may be low. After heating the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (II) at 105° C. for 120 hours, the pressure-sensitive adhesive sheet may contain 50 ppm or less of acetic acid on a mass basis. When the content of acetic acid is as low as this, the optical laminate is less likely to be colored even after being exposed to a high-temperature environment.

After heating the adhesive sheet formed from the adhesive composition (II) at 105 ° C. for 120 hours, the content of acetic acid contained in the adhesive sheet is 30 ppm or less, 20 ppm or less, 15 ppm or less, 10 ppm or less, on a mass basis. It may be 7 ppm or less, 5 ppm or less, 3 ppm or less, 2.8 ppm or less, or even less than 2.5 ppm. The lower limit of the acetic acid content is not particularly limited, and is, for example, 0 ppm or more on a mass basis.

(Embodiment 3)
[Adhesive sheet]
An example of the adhesive sheet of this embodiment is shown in FIG. The pressure-sensitive adhesive sheet 1 in FIG. 1 is a sheet formed from pressure-sensitive adhesive composition (I) or a sheet formed from pressure-sensitive adhesive composition (II).

When the adhesive sheet 1 is formed from the adhesive composition (I), the adhesive sheet 1 may have a surface resistance value within the range mentioned above in the description of the adhesive composition (I). When the adhesive sheet 1 is formed from the adhesive composition (II), the adhesive sheet may contain formic acid in the range mentioned above in the description of the adhesive composition (II).

The adhesive sheet 1 can be formed from the adhesive composition (I) or the adhesive composition (II) by the following method. The following describes a method for forming the pressure-sensitive adhesive sheet 1 from the pressure-sensitive adhesive composition (I), but the pressure-sensitive adhesive sheet 1 can also be formed using the same method in the case of the pressure-sensitive adhesive composition (II).

For the solvent type, for example, the adhesive composition (I) or a mixture of the adhesive composition (I) and a solvent is applied to a base film to form a coating film, and the formed coating film is dried. An adhesive sheet 1 is formed. The pressure-sensitive adhesive composition (I) is thermally cured by the heat generated during drying. For the active energy ray-curable type (photocurable type), for example, the monomer(s) that becomes polymer (A) by polymerization, and if necessary, a partial polymer of the monomer(s), and a polymerization initiator. A mixture of additives, a solvent, etc. is applied to a base film, and the formed coating film is irradiated with active energy rays to form an adhesive sheet 1. Before irradiation with active energy rays, the coating film may be dried to remove the solvent. The base film may be a film (release liner) whose coated surface has been subjected to a release treatment.

The adhesive sheet 1 formed on the base film can be transferred to any layer. Further, the base film may be an optical film such as a polarizing plate, and in this case, an optical laminate containing the adhesive sheet 1 and the optical film is obtained.

A known method can be used for coating the base film. Applications include, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, etc. It can be implemented by

For solvent-based coatings, the drying temperature after coating is, for example, 40 to 200°C. The drying time may be, for example, 5 seconds to 20 minutes, 5 seconds to 10 minutes, or even 10 seconds to 5 minutes. For the active energy ray-curable type, the drying temperature and drying time when drying after application may be within the above ranges.

Preferably, the compositions and mixtures applied to the base film have a viscosity suitable for handling and application. For this reason, for the active energy ray-curable type, the mixture to be applied preferably contains a partial polymer of the monomer(s).

The thickness of the adhesive sheet 1 is, for example, 2 μm to 55 μm, and may be 2 μm to 30 μm, 5 μm to 25 μm, or even 10 μm to 20 μm.

The adhesive sheet 1 can be used, for example, in an optical laminate. In other words, the adhesive sheet 1 may be used for optical laminates. However, the use of the adhesive sheet 1 is not limited to the above example.

(Embodiment 4)
[Optical laminate]
FIG. 2 shows an example of the optical laminate of this embodiment. The optical laminate 10A in FIG. 2 includes an adhesive sheet 1 and an optical film. The optical film in FIG. 2 is a polarizing plate 2. Polarizing plate 2 includes a polarizer. The adhesive sheet 1 and the polarizing plate 2 are laminated on each other. The optical laminate 10A can be attached to an object (for example, an image display panel) via the adhesive sheet 1. The optical laminate 10A can be used as an optical film with an adhesive sheet, more specifically, as a polarizing plate with an adhesive sheet. Examples of optical films other than the polarizing plate 2 are a retardation film and a laminated film containing a polarizing plate and/or a retardation film. The optical film may be a circularly polarizing plate. However, the optical film is not limited to the above example. The optical film may include a glass film.

<Polarizing plate>
The polarizing plate 2 is typically a laminate including a polarizer and a protective film (transparent protective film). The protective film is placed, for example, in contact with the main surface (the surface with the widest area) of the polarizer. A polarizer may be placed between two protective films. The optical laminate 10A further includes a protective film, and the protective film may be disposed on at least one surface of the polarizer.

The polarizer is not particularly limited, and examples include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, partially saponified ethylene/vinyl acetate copolymer films, iodine, and dichroism. Examples include those obtained by adsorbing dichroic substances such as dyes and uniaxially stretched; polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochloric acid treated polyvinyl chloride. A polarizer typically consists of a polyvinyl alcohol film (polyvinyl alcohol films include partially saponified ethylene/vinyl acetate copolymer films) and a dichroic substance such as iodine.

The thickness of the polarizer is not particularly limited, and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the polarizer is not particularly limited, and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, 20 μm or less in thickness) has suppressed dimensional changes and can contribute to improving the durability of the optical laminate, especially the durability under high temperatures.

As a material for the protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetylcellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, and cyclic resins. Examples include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the protective film may be a thermosetting resin or an ultraviolet curing resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone. When the polarizing plate 2 has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin is attached to one main surface of a polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet curable resin is attached to the other main surface of the polarizer. A protective film made of molded resin may be attached. The protective film may contain one or more types of arbitrary additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like.

The moisture permeability of the protective film is not particularly limited, and may be 200 g/(m ² ·day) or less, or 50 g/(m ² ·day) or less. In this case, it is possible to suppress moisture in the air from entering the inside of the polarizing plate 2, and it is possible to suppress a change in the moisture content of the polarizing plate 2. Thereby, it is possible to suppress the occurrence of curling or dimensional changes in the polarizing plate 2 during storage or the like. Furthermore, when a protective film whose moisture permeability is limited to the above range is placed between the adhesive sheet 1 and the polarizer, it may contribute to inhibiting the movement of radicals from the adhesive sheet 1 at high temperatures. . Examples of materials forming the protective film with low moisture permeability include polyester polymers, polycarbonate polymers, arylate polymers, amide polymers, olefin polymers, cyclic olefin polymers, (meth)acrylic polymers, and Mixtures may be mentioned.

The moisture permeability of the protective film can be measured by the following method according to the moisture permeability test (cup method) of JIS Z0208:1976. First, a protective film is cut into a diameter of 60 mm to prepare a measurement sample. Next, the measurement sample is set in a moisture-permeable cup in which approximately 15 g of calcium chloride is placed. This moisture permeable cup is placed in a constant temperature machine set at a temperature of 40° C. and a humidity of 92% RH, and left for 24 hours to conduct a moisture permeability test. By measuring the increase in weight of calcium chloride before and after the test, the moisture permeability of the protective film can be determined.

The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm from the viewpoint of strength, workability such as handling, thin film properties, etc.

The polarizer and the protective film are usually in close contact with each other via a water-based adhesive or the like. Examples of water-based adhesives include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex, water-based polyurethanes, and water-based polyesters. Examples of adhesives other than the above adhesives include ultraviolet curable adhesives and electron beam curable adhesives. Electron beam-curable adhesives for polarizing plates exhibit suitable adhesion to various types of protective films. The adhesive may include a metal compound filler.

In the polarizing plate, a retardation film or the like may be formed on the polarizer instead of the protective film. It is also possible to provide another protective film, a retardation film, etc. on the protective film.

Regarding the protective film, a hard coat layer may be provided on the surface opposite to the surface bonded to the polarizer, and treatments for the purpose of anti-reflection, anti-sticking, diffusion, anti-glare, etc. can also be applied. .

The light transmittance in the thickness direction of the optical laminate 10A before the heating test is defined as Tsa ₀ , and the light transmittance in the thickness direction of the optical laminate 10A after heating the optical laminate 10A at 95° C. for 500 hours. is defined as Tsa ₅₀₀ . At this time, the difference in light transmittance before and after the heating test ΔTsa=Tsa ₅₀₀ −Tsa ₀ satisfies, for example, ΔTsa>0%. This makes the optical laminate more suitable for use in environments where high temperatures are a consideration. Details of the heating test are described in the Examples column.

The light transmittance in the thickness direction of the optical laminate 10A before the heating test is defined as Tsb ₀ , and the light transmittance in the thickness direction of the optical laminate 10A after heating the optical laminate 10A at 105° C. for 500 hours. is defined as Tsb ₅₀₀ . At this time, the difference in light transmittance before and after the heating test, ΔTsb=Tsb ₅₀₀ −Tsb ₀ , satisfies, for example, ΔTsb>−10%. ΔTsb may satisfy ΔTsb>0%.

Another example of the optical laminate of this embodiment is shown in FIG. The optical laminate 10B in FIG. 3 has a laminated structure in which a release liner 3, an adhesive sheet 1, and a polarizing plate 2 are laminated in this order. The optical laminate 10B can be used as a polarizing plate with an adhesive sheet by peeling off the release liner 3. The following examples may be combined with each other unless technically inconsistent.

Examples of constituent materials of the release liner 3 include polyethylene, polypropylene, polyethylene terephthalate, plastic films such as polyester films, porous materials such as paper, cloth, and nonwoven fabrics, nets, foam sheets, metal foils, and laminates thereof. Examples include suitable thin film materials, but plastic films are preferably used because of their excellent surface smoothness.

The plastic film is not particularly limited as long as it can protect the adhesive sheet 1, and examples thereof include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, and vinyl chloride copolymer. film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, and the like.

The thickness of the release liner 3 is usually about 5 to 200 μm, preferably about 5 to 100 μm. The release liner 3 may be treated with silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agents, mold release and antifouling treatment with silica powder, coating type, kneading type, vapor deposition, etc., as necessary. Antistatic treatment such as a mold may be applied. In particular, by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the release liner 3, the releasability from the pressure-sensitive adhesive sheet 1 can be further improved.

Note that, as described above, the base film used when producing the adhesive sheet 1 may be used as the release liner 3.

Another example of the optical laminate of this embodiment is shown in FIG. The optical laminate 10C in FIG. 4 has a laminate structure in which a release liner 3, an adhesive sheet 1, a retardation film 5, an interlayer adhesive 4, and a polarizing plate 2 are laminated in this order. After peeling off the release liner 3, the optical laminate 10C can be used by being attached to, for example, an image display cell.

As the retardation film 5, one obtained by stretching a polymer film or one obtained by aligning and fixing a liquid crystal material can be used. The retardation film 5 has, for example, birefringence in the plane and/or in the thickness direction.

The retardation film 5 includes a retardation film for antireflection (see JP-A-2012-133303 [0221], [0222], and [0228]) and a retardation film for viewing angle compensation (see JP-A-2012-133303 [0221], [0222], and [0228]). 0225], [0226]), an obliquely oriented retardation film for viewing angle compensation (see JP-A-2012-133303 [0227]), and the like.

The specific configuration of the retardation film 5, for example, retardation value, arrangement angle, three-dimensional birefringence, single layer or multilayer, etc., is not particularly limited, and any known retardation film can be used.

The thickness of the retardation film 5 is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 1 to 9 μm, particularly preferably 3 to 8 μm.

The retardation film 5 may include, for example, a quarter-wave plate and/or a half-wave plate in which a liquid crystal material is oriented and fixed.

A known adhesive can be used as the interlayer adhesive 4. The adhesive sheet 1 may be used as the interlayer adhesive 4.

Another example of the optical laminate of this embodiment is shown in FIG. The optical laminate 10D in FIG. 5 has a laminate structure in which a release liner 3, an adhesive sheet 1, a retardation film 5, an interlayer adhesive 4, a polarizing plate 2, and a protective film 6 are laminated in this order. After peeling off the release liner 3, the optical laminate 10D can be used by being attached to, for example, an image display cell.

The protective film 6 has the function of protecting the polarizing plate 2, which is the outermost layer, during distribution and storage of the optical laminate 10D, and when the optical laminate 10D is incorporated into an image display device. Alternatively, the protective film 6 may function as a window to an external space when incorporated into an image display device. The protective film 6 is typically a resin film. The resin constituting the protective film 6 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 6 is not limited to the above example. The protective film 6 may be a glass film or a laminated film including a glass film. The protective film 6 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

The protective film 6 may be bonded to the polarizing plate 2 with any adhesive. Bonding using the adhesive sheet 1 is also possible.

The optical laminate of this embodiment can be distributed and stored, for example, as a roll of a band-shaped optical laminate or as a sheet-shaped optical laminate. The optical laminate of this embodiment is suitable for use in image display devices, particularly in-vehicle displays, which are used in environments where static electricity is particularly likely to occur. Examples of in-vehicle displays include panels for car navigation devices, cluster panels, mirror displays, and the like. The cluster panel is a panel that displays information such as the vehicle's traveling speed and engine speed.

(Embodiment 5)
[Optical laminate]
Another example of an optical laminate includes an adhesive sheet and an optical film. The optical film is a polarizing plate containing a polarizer. After heating the optical laminate at 105° C. for 120 hours, the polarizer contains no more than 70 ppm formic acid by weight. When the content of formic acid contained in the polarizing plate is as low as this, the optical laminate is unlikely to be colored even after being exposed to a high-temperature environment.

Another example of the optical laminate of this embodiment is shown in FIG. The optical laminate 10E in FIG. 6 includes an adhesive sheet 7 and an optical film. The optical film in FIG. 6 is a polarizing plate 8. Polarizing plate 8 includes a polarizer. The adhesive sheet 7 and the polarizing plate 8 are laminated on each other. The optical laminate 10E can be attached to an object (for example, an image display panel) via the adhesive sheet 7. The optical laminate 10E can be used as an optical film with an adhesive sheet, more specifically, as a polarizing plate with an adhesive sheet. Examples of optical films other than the polarizing plate 8 are a retardation film and a laminated film containing a polarizing plate and/or a retardation film. The optical film may be a circularly polarizing plate. However, the optical film is not limited to the above example. The optical film may include a glass film.

After heating the optical laminate 10E at 105° C. for 120 hours, the content of formic acid contained in the polarizing plate is 65 ppm or less, 60 ppm or less, 55 ppm or less, 50 ppm or less, 45 ppm or less, 40 ppm or less, 35 ppm or less, 30 ppm or less, and may be 28 ppm or less. The lower limit of the content of formic acid is not particularly limited, and is, for example, 0 ppm or more.

According to studies conducted by the present inventors, it has been found that unnecessary coloring tends to occur in optical laminates after being exposed to high-temperature environments. A possible cause of the coloring is polyene conversion of PVA by an acid contained in the polarizing plate, such as formic acid. Details of polyenization of PVA with formic acid are as described in Embodiment 2.

The adhesive sheet 7 is formed from, for example, the adhesive composition (III). The adhesive composition (III) contains, for example, a polymer (C) and a crosslinking agent. The adhesive composition (III) may contain the polymer (C) as a main component. "Principal component" has the meaning described above.

Examples of the polymer (C) are (meth)acrylic polymers, urethane polymers, silicone polymers, and rubber polymers. Polymer (C) is preferably a (meth)acrylic polymer. Polymer (C) can function as a base polymer for an acrylic pressure-sensitive adhesive, for example. The polymer (C) may be a polymer having a dielectric constant of 5.0 or more at a frequency of 100 kHz. The dielectric constant may be 6.0 or more, 6.5 or more, 6.8 or more, 7.0 or more, 7.3 or more, or even 7.5 or more. The upper limit of the dielectric constant is not particularly limited, and is, for example, 10.0 or less.

Polymer (C) may have a structural unit derived from a monomer shown in the following formula (1).

R ¹ in formula (1) is a hydrogen atom or a methyl group. R ² in formula (1) is an alkyl group which may be linear or branched, and is preferably a linear alkyl group. Examples of R ² are methyl and ethyl groups. n is an integer from 1 to 15, preferably from 1 to
It is an integer of 10, more preferably an integer of 1 to 5.

In the polymer (C), the content of the structural unit derived from the monomer shown in formula (1) is not particularly limited, and may be, for example, 15 to 99.5% by weight, or 30 to 99% by weight. The content may be 50 to 98% by weight, 50 to 80% by weight, or 50 to 70% by weight.

In addition to the monomer shown in formula (1), monomers constituting the polymer (C) include (meth)acrylic monomers having an alkyl group having 1 to 30 carbon atoms in the side chain, and hydroxyl group-containing monomers. at least one monomer selected from the group consisting of monomers containing monomers, aromatic ring-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, and polyfunctional monomers. It will be done. These monomers can be used alone or in combination. Examples of these monomers are the same as the monomer (A2) described in Embodiment 1, so the explanation will be omitted.

In the polymer (C), the content of structural units derived from monomers is not particularly limited, and may be, for example, 0.1 to 50% by weight, or 0.5 to 45% by weight. . In some cases, the content of structural units derived from monomers in the polymer (C) may be 1 to 5% by weight. Further, in some cases, the content of structural units derived from monomers in the polymer (C) may be 20 to 45% by weight, 25 to 45% by weight, 30 to 45% by weight. It may be expressed in percent by weight.

In addition to the monomer shown in formula (1) and the monomers mentioned above, the monomer components include (meth)acryloyl groups, vinyl groups, etc. for the purpose of improving the adhesiveness and heat resistance of the pressure-sensitive adhesive sheet. Other monomers having polymerizable functional groups containing unsaturated double bonds can be used. Other monomers can be used alone or in combination.

When using other monomers as monomer components, the content of structural units derived from other monomers in the polymer (C) may be 30% by weight or less, and may be 10% by weight. It may be less than or equal to 0% by weight (not having the structural unit).

The weight average molecular weight (Mw) of the polymer (C) is, for example, 1 million to 3 million, may be 1.2 million to 2.5 million, or may be 1.5 million to 2.3 million. When the weight average molecular weight of the polymer (C) is 1 million to 3 million, cracks in the pressure-sensitive adhesive sheet can be suppressed, and an increase in viscosity and occurrence of gelation tend to be suppressed.

The adhesive composition (III) may contain the above-mentioned polymer (C). The adhesive composition (II) may further contain a polymer other than the polymer (C).

Polymer (C) can be produced by known polymerization methods such as solution polymerization, radiation polymerization such as electron beam or UV radiation, bulk polymerization, and various radical polymerizations such as emulsion polymerization. The resulting polymer (C) may be a random copolymer, a block copolymer, a graft copolymer, or the like.

The method and polymerization conditions for forming the polymer (C) may be the same as the method and polymerization conditions for forming the polymer (A) described in Embodiment 1, respectively. The types of solvent, type of polymerization initiator, etc. used to form the polymer (C) can also be those explained in Embodiment 1.

Examples of the crosslinking agent contained in the adhesive composition (III) are an isocyanate crosslinking agent and a peroxide crosslinking agent. A peroxide-based crosslinking agent and an isocyanate-based crosslinking agent may be used together. The adhesive composition (III) may contain an isocyanate crosslinking agent, a peroxide crosslinking agent, or both an isocyanate crosslinking agent and a peroxide crosslinking agent. Good too. As the isocyanate-based crosslinking agent and the peroxide-based crosslinking agent, the isocyanate-based crosslinking agent and the peroxide-based crosslinking agent described in Embodiment 1 can be used.

Note that the adhesive sheet 7 may be an adhesive sheet formed from the adhesive composition (I) described in Embodiment 1, or may be an adhesive sheet formed from the adhesive composition (II) described in Embodiment 2. It may be a sheet. In the optical laminate 10E, using these adhesive sheets as the adhesive sheet 7 is particularly suitable for reducing the content of formic acid contained in the polarizing plate 8.

The polarizing plate 8 may be similar to the polarizing plate 2 described in the fourth embodiment. Polarizing plate 8 may include a polarizer.

The optical laminate of this embodiment may be the same as the optical laminates 10A to 10D of Embodiment 4, except that adhesive sheet 7 is used instead of adhesive sheet 1.

(Embodiment 6)
[Image display panel]
FIG. 7 shows an example of the image display panel of this embodiment. The image display panel 11A in FIG. 7 includes an optical laminate 10A, and further includes, for example, an image display cell 30A. Specifically, the optical laminate 10A is bonded to the image display cell 30A via the adhesive sheet 1. Note that, instead of the optical laminate 10A, the optical laminate 10B, 10C, or 10D shown in FIGS. 3 to 5 can also be used (excluding the release liner 3). In addition, the optical laminate 10E shown in FIG. 6 can also be used instead of the optical laminate 10A.

The image display cell 30A includes, for example, an image forming layer 32, a first transparent substrate 31, and a second transparent substrate 33. The image forming layer 32 is disposed, for example, between the first transparent substrate 31 and the second transparent substrate 33, and is in contact with each of the first transparent substrate 31 and the second transparent substrate 33. The adhesive sheet 1 of the optical laminate 10A is in contact with, for example, the first transparent substrate 31 of the image display cell 30A.

The image forming layer 32 is, for example, a liquid crystal layer containing liquid crystal molecules that are homogeneously aligned in the absence of an electric field. A liquid crystal layer containing such liquid crystal molecules is suitable for an IPS (In-Plane-Switching) method. However, the liquid crystal layer may be of a TN (Twisted Nematic) type, an STN (Super Twisted Nematic) type, a π type, a VA (Vertical Alignment) type, or the like. In this specification, an image display cell provided with a liquid crystal layer may be referred to as a liquid crystal cell, and an image display panel provided with a liquid crystal cell may be referred to as a liquid crystal panel. Note that the image forming layer 32 may be an EL light emitting layer.

The thickness of the image forming layer 32 is, for example, 1.5 μm to 4 μm.

Examples of materials for the first transparent substrate 31 and the second transparent substrate 33 include glass and polymer. In this specification, a transparent substrate made of a polymer may be referred to as a polymer film. Examples of the polymer constituting the transparent substrate include polyethylene terephthalate, polycycloolefin, polycarbonate, and the like. The thickness of the transparent substrate made of glass is, for example, 0.1 mm to 1 mm. The thickness of the transparent substrate made of polymer is, for example, 10 μm to 200 μm.

The image display cell 30A may further include layers other than the image forming layer 32, the first transparent substrate 31, and the second transparent substrate 33. Examples of other layers include a color filter, an easy-to-adhesion layer, and a hard coat layer. The color filter is arranged, for example, on the viewing side of the image forming layer 32, and is preferably located between the first transparent substrate 31 and the adhesive sheet 1 of the optical laminate 10A. The easily adhesive layer and the hard coat layer are arranged, for example, on the surface of the first transparent substrate 31 or the second transparent substrate 33.

The image display panel 11A may further include members other than the optical laminate 10A and the image display cell 30A. For example, the image display panel 11A may further include a conductive structure (not shown) electrically connected to the side surface of the optical laminate 10A. By connecting the conductive structure to the ground, it is easy to prevent the optical laminate 10A from being charged by static electricity. The conductive structure may cover the entire side surface of the optical laminate 10A, or may partially cover the side surface of the optical laminate 10A. The ratio of the area of the side surface of the optical laminate 10A covered by the conductive structure to the area of the entire side surface of the optical laminate 10A is, for example, 1% or more, preferably 3% or more.

Examples of the material of the conductive structure include conductive paste made of metal such as silver and gold; conductive adhesive; and other conductive materials. The conductive structure may be a wiring extending from the side surface of the optical laminate 10A.

The image display panel 11A may further include an optical film other than the polarizing plate 2. Examples of other optical films include films used in image display devices, such as polarizing plates, reflective plates, anti-transmission plates, viewing angle compensation films, and brightness enhancement films. The image display panel 11A may include one or more of these other optical films.

When the other optical film is a polarizing plate, the polarizing plate is bonded to the second transparent substrate 33 of the image display cell 30A, for example, via an adhesive sheet. This polarizing plate has, for example, the configuration described above for the polarizing plate 2. In a polarizing plate as another optical film, the transmission axis (or absorption axis) of the polarizer is perpendicular to the transmission axis (or absorption axis) of the polarizer in the polarizing plate 2, for example. As the material for the adhesive sheet for bonding the polarizing plate and the second transparent substrate 33 together, those mentioned above for the adhesive sheet 1 can be used. The thickness of this pressure-sensitive adhesive sheet is not particularly limited, and is, for example, 1 to 100 μm, preferably 2 to 50 μm, more preferably 2 to 40 μm, and still more preferably 5 to 35 μm.

Another example of the image display panel of this embodiment is shown in FIG. The image display panel 11B in FIG. 8 further includes a conductive layer 40 disposed between the optical laminate 10A and the image display cell 30A.

The conductive layer 40 is, for example, a layer containing a conductive agent. As the conductive agent, those mentioned above for the adhesive sheet 1 can be used. However, the conductive agent is not limited to the above example. The conductive layer 40 is made of various conductive agents, such as carbon nanotubes, ITO, ATO, and a conductive polymer that is a composite with a dopant (for example, a composite of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid). body: PEDOT/PSS), etc. The thickness of the conductive layer 40 is, for example, 5 nm to 180 nm. The surface resistance value of the conductive layer 40 is, for example, 1.0×10 ⁶ Ω/□ to 1.0×10 ¹⁰ Ω/□, preferably 1.0×10 ⁸ Ω/□ to 1.0×10 ⁹ Ω/□.

Another example of the image display panel of this embodiment is shown in FIG. The image display panel 11C in FIG. 9 includes an image display cell 30B that further includes a touch sensing electrode section 35. In the image display cell 30B, the touch sensing electrode section 35 is arranged between the first transparent substrate 31 and the second transparent substrate 33. The touch sensing electrode section 35 has a touch sensor and touch drive function. The image display panel 11C is a so-called in-cell type image display panel, and the image display cell 30B is a so-called in-cell type image display cell.

The touch sensing electrode section 35 includes, for example, a touch sensor electrode 36 and a touch drive electrode 37. The touch sensor electrode 36 means a (receiving) electrode for touch detection. The touch sensor electrode 36 and the touch drive electrode 37 can be independently formed in various patterns. For example, when the image display cell 30B has a flat plate shape, the touch sensor electrode 36 and the touch drive electrode 37 may be provided independently in the X-axis direction and the Y-axis direction, respectively, and formed in a pattern such that these electrodes intersect at right angles. Can be done. In FIG. 9 , in the touch sensing electrode section 35 , the touch sensor electrode 36 is arranged closer to the viewing side than the touch drive electrode 37 . However, the touch drive electrode 37 may be arranged closer to the viewing side than the touch sensor electrode 36. In the touch sensing electrode section 35, the touch sensor electrode 36 and the touch drive electrode 37 may be integrated.

In FIG. 9, the touch sensing electrode section 35 is arranged between the image forming layer 32 and the first transparent substrate 31 (on the viewing side of the image forming layer 32). However, the touch sensing electrode section 35 may be arranged between the image forming layer 32 and the second transparent substrate 33 (on the side closer to the illumination system than the image forming layer 32).

In the touch sensing electrode section 35, the touch sensor electrode 36 and the touch drive electrode 37 do not need to be in contact with each other. For example, the touch sensor electrode 36 may be arranged between the image forming layer 32 and the first transparent substrate 31, and the touch drive electrode 37 may be arranged between the image forming layer 32 and the second transparent substrate 33.

The drive electrode (the touch drive electrode 37 or the electrode in which the touch sensor electrode 36 and the touch drive electrode 37 are integrated) in the touch sensing electrode section 35 can also serve as a common electrode for controlling the image forming layer 32.

The touch sensor electrode 36 (capacitance sensor), the touch drive electrode 37, or an electrode formed by integrating these, which constitutes the touch sensing electrode section 35, functions as a transparent conductive layer. The material of this transparent conductive layer is not particularly limited, and examples thereof include metals such as gold, silver, copper, platinum, palladium, aluminum, nickel, chromium, titanium, iron, cobalt, tin, magnesium, and tungsten; Examples include alloys. The material of the transparent conductive layer may be an oxide of a metal such as indium, tin, zinc, gallium, antimony, zirconium, or cadmium. Specific examples of this oxide include indium oxide, tin oxide, titanium oxide, cadmium oxide, and mixtures thereof. The material of the transparent conductive layer may be a metal compound such as copper iodide. The material of the transparent conductive layer is preferably indium oxide (ITO) containing tin oxide, tin oxide (ATO) containing antimony, etc., and ITO is particularly preferable. When the material of the transparent conductive layer is ITO, the content of indium oxide in the transparent conductive layer is preferably 80 to 99% by weight, and the content of tin oxide is preferably 1 to 20% by weight.

The electrodes (touch sensor electrode 36, touch drive electrode 37, or an electrode formed by integrating these) constituting the touch sensing electrode section 35 are always placed between the first transparent substrate 31 and the second transparent substrate 33. It can be formed as a transparent electrode pattern by the method. This transparent electrode pattern is electrically connected, for example, to a lead-out line formed at the end of the transparent substrate. The routing line is connected to, for example, a controller IC. The shape of the transparent electrode pattern can be any shape depending on the purpose, such as a comb shape, a stripe shape, or a rhombus shape. The thickness of the transparent electrode pattern is, for example, 10 nm to 100 nm. The width of the transparent electrode pattern is, for example, 0.1 mm to 5 mm.

(Embodiment 7)
[Image display device]
The image display device of this embodiment includes, for example, an image display panel 11A and a lighting system. Note that the image display panels 11B and 11C shown in FIGS. 8 to 9 can also be used in place of the image display panel 11A. In the image display device, the image display panel 11A is arranged, for example, on the viewing side rather than the illumination system. The illumination system includes, for example, a backlight or a reflector, and irradiates the image display panel 11A with light.

The image display device may be an organic EL display or a liquid crystal display. However, the image display device is not limited to this example. The image display device may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device can be used for household appliances, in-vehicle applications, public information displays (PID), etc., and is preferably an in-vehicle display.

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

<Weight average molecular weight of (meth)acrylic polymer>
The weight average molecular weight (Mw) of the (meth)acrylic polymer was measured by GPC (gel permeation chromatography). Mw/Mn of the (meth)acrylic polymer was also measured in the same manner.
・Analyzer: Tosoh Corporation, HLC-8120GPC
・Column: Manufactured by Tosoh Corporation, G7000H _XL +GMH _XL +GMH _XL
・Column size: 7.8mmφ each x 30cm total 90cm
・Column temperature: 40℃
・Flow rate: 0.8mL/min
・Injection volume: 100μL
・Eluent: Tetrahydrofuran ・Detector: Differential refractometer (RI)
・Standard sample: polystyrene

[Preparation of (meth)acrylic polymer A1]
A monomer containing 99 parts by weight of 2-methoxyethyl acrylate (MEA) and 1 part by weight of 4-hydroxybutyl acrylate (HBA) was placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. The body mixture was prepared. Furthermore, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN; manufactured by Kishida Chemical Co., Ltd.) as a polymerization initiator was added together with 100 parts by weight of ethyl acetate to 100 parts by weight of the monomer mixture. . While stirring the mixture gently, nitrogen gas was introduced into the flask to replace the atmosphere with nitrogen. A solution of (meth)acrylic polymer A1 with a weight average molecular weight (Mw) of 1.8 million and Mw/Mn = 4.4 was prepared by maintaining the liquid temperature in the flask at around 55°C and carrying out a polymerization reaction for 8 hours. did.

[Preparation of (meth)acrylic polymer A2]
The weight average molecular weight ( A solution of (meth)acrylic polymer A2 with Mw) 1,750,000 and Mw/Mn=3.5 was prepared.

[Preparation of (meth)acrylic polymer A3]
The weight average molecular weight (Mw) was 2,000,000, and Mw/Mn=4. A solution of (meth)acrylic polymer A3 of No. 5 was prepared.

The monomers used in the synthesis of each (meth)acrylic polymer and the amounts charged are summarized in Table 1 below.

[Preparation of (meth)acrylic adhesive composition]
(Example A1)
Based on 100 parts by weight of the solid content of the solution of (meth)acrylic polymer A1, 0.35 parts by weight of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, Coronate L; trimethylolpropane tolylene diisocyanate), 5 parts by weight as a conductive agent. By further blending 1 part of bis(trifluoromethanesulfonyl)imide lithium (LiTFSI; manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) and 1 part by weight of an antioxidant (manufactured by BASF Corporation, Irganox 1135, molecular weight 390), Example A1 was prepared. A solution of a (meth)acrylic adhesive composition was prepared.

(Example A2)
Same as Example A1, except that 0.1 part by weight of a peroxide-based crosslinking agent (manufactured by NOF Corporation, Niper BMT) was further blended, and the amount of antioxidant was 0.5 part by weight. A solution of the (meth)acrylic pressure-sensitive adhesive composition of Example A2 was prepared.

(Examples A3 to A8)
As shown in Table 2 below, the isocyanate crosslinking agent, peroxide crosslinking agent, antioxidant, and conductive agent are blended with 100 parts by weight of the solid content of the (meth)acrylic polymer solution. Solutions of the (meth)acrylic adhesive compositions of Examples A3 to A8 were prepared.

(Comparative examples A1, A2)
As shown in Table 2 below, the above-mentioned isocyanate-based crosslinking agent, the above-mentioned peroxide-based crosslinking agent, and conductive agent were blended with 100 parts by weight of the solid content of the (meth)acrylic polymer solution, and the comparative example Solutions of (meth)acrylic adhesive compositions A1 and A2 were prepared.

[Preparation of adhesive sheet]
A solution of each adhesive composition was applied to one side of a polyethylene terephthalate film (release liner; manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) whose surface had been treated with a silicone release agent until the thickness of the adhesive sheet after drying was 20 μm. It was applied like this. The obtained coating film was dried at 155° C. for 1 minute to form an adhesive sheet on the surface of the release liner.

<Measurement of surface resistance value>
For each adhesive composition, the surface resistance value when an adhesive sheet was formed was determined by using the adhesive sheet prepared above as a test sample, using Hiresta MCP-HT450 manufactured by Mitsubishi Chemical Analytic Corporation, and applying an applied voltage of 250 V. The measurement was performed under the condition that the application time was 10 seconds. The surface resistance value was measured under an environment of a temperature of 25° C.±5° C. and a relative humidity of 50±5%.

[Preparation of optical laminate]
<Preparation of polarizing plate A>
The polyvinyl alcohol film was stretched up to 3 times between rolls having different speed ratios while being dyed for 1 minute in an iodine solution having a concentration of 0.3% by weight at a temperature of 30°C. Next, it is stretched for 0.5 minutes in an aqueous solution containing boric acid at a concentration of 4% by weight and potassium iodide at a concentration of 10% at a temperature of 60°C until the total stretching ratio becomes 6 times. did. Next, a polarizer with a thickness of 18 μm was prepared by immersing it in an aqueous solution containing potassium iodide at a concentration of 1.5% by weight and washing it for 10 seconds at a temperature of 30°C, and then drying it at 50°C for 4 minutes. Obtained. A 30 μm thick transparent protective film made of a modified acrylic polymer having a lactone ring structure was attached to one side of the polarizer using a polyvinyl alcohol adhesive. Furthermore, a 47 μm thick transparent protective film made of a triacetyl cellulose film (Konica Minolta, KC4UY) with a hard coat layer (HC) was bonded to the other surface of the polarizer using a polyvinyl alcohol adhesive. Polarizing plate A was produced by heating and drying for 5 minutes in an oven set at 70°C.

<Preparation of optical laminate>
Next, each of the adhesive sheets of Examples and Comparative Examples formed on the release liner was transferred to the polarizing plate prepared above to produce an optical laminate (polarizing plate with adhesive sheet). Note that the adhesive sheet was transferred onto the surface of a polarizing plate on the side of a transparent protective film made of a modified acrylic polymer.

<Coloring>
The coloring of the optical laminate under high temperature was evaluated by the following method. The produced optical laminate was cut into a size of 45×40 mm so that the absorption axis of the polarizer was the long side. Next, the cut optical laminate was bonded to a glass plate imitating the outermost layer of an image display panel via the adhesive sheet. Next, a glass plate imitating the front transparent member was attached to the exposed surface of the optical laminate on the polarizing plate side using an adhesive (manufactured by Nitto Denko Corporation, LUCIACS CS9821; acrylic acid monomer-free adhesive, thickness 200 μm). By bonding them together, a laminate for evaluation imitating an image display device was produced. Next, a heating test was conducted in which the evaluation laminate was left in a hot air oven maintained at 105° C. for 120 hours, and the light transmittance in the thickness direction of the laminate before and after the heating test was measured. The light transmittance was determined using a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., LPF-200) as a Y value (corrected for visual sensitivity) according to the 2-degree visual field XYZ system defined in JIS Z8701:1982. A C light source was used as the light source. The measurement wavelength was 380 to 700 nm (every 10 nm). The light transmittance of the laminate was measured near the center where the coloration was considered to be the most advanced. The light transmittance before the heating test is Ts ₀ and the light transmittance after the heating test is Ts ₁₂₀ , and the degree of coloring of the optical laminate under high temperature is evaluated based on the value of the difference ΔTs = Ts ₁₂₀ - Ts ₀ . did.
A: ΔTs is more than 0% B: ΔTs is 0% or less - more than 3% C: ΔTs is -3% or less - more than 10% D: ΔTs is -10% or less

<Durability (high temperature durability) A>
The durability (high temperature durability) of the optical laminate was evaluated by the following method. The produced optical laminate was fixed to the surface of a glass plate (Eagle XG, manufactured by Corning) via the adhesive sheet. Fixation was carried out in an atmosphere of 24° C. and 50% RH. Next, after processing in an autoclave at 50°C and 5 atm (absolute pressure) for 15 minutes, it was left to cool to 24°C to stabilize the bonding of the optical laminate to the glass plate, and then heated at 105°C. It was left in a heated atmosphere for 500 hours. After leaving it for a while, return it to an atmosphere of 24°C and 50% RH, visually check whether the polarizing plate has peeled off from the glass plate or if bubbles have formed between the glass plate and the polarizing plate, and perform the following procedure. , the durability was evaluated.
A: No changes in appearance such as foaming or peeling are observed.
B: Slight peeling or foaming is observed at the edges, but this is within a range that poses no problem for practical use.
C: Slight continuous peeling or foaming is observed at the edges, but this is within a range that poses no problem for practical use.
D: Significant peeling or foaming was observed at the edges, which was a problem in practice.

<Antistatic property>
The antistatic property of the optical laminate was evaluated by the following method (ESD test). The produced optical laminate was fixed to the surface (viewing side surface) of the image display panel shown in FIG. 9 via the adhesive sheet. Next, the liquid crystal display panel to which the optical laminate was fixed was set on a backlight device, and static electricity was emitted at an applied voltage of 15 kV from an electrostatic discharge gun to the surface of the polarizing plate, which was the exposed surface on the viewing side. The time from the point of firing until the white areas due to static electricity disappeared was measured, and the antistatic property was evaluated as follows.
A: Disappears within 1 second B: Disappears within more than 1 second and within 10 seconds C: Disappears within more than 10 seconds and within 60 seconds D: Disappears after more than 60 seconds

The evaluation results of each optical laminate of Examples and Comparative Examples are shown in Table 3 below, along with the surface resistance values of the adhesive sheets used for each optical laminate. Note that coloration (reddening) in each optical laminate at high temperatures occurred mainly in the polarizer.

As shown in Table 3, compared to the optical laminate of Comparative Example A2, the optical laminate of the example achieved a lower surface resistance value of the pressure-sensitive adhesive sheet while suppressing discoloration at high temperatures. In addition, in the optical laminate of Comparative Example A1, the adhesive composition constituting the adhesive sheet does not contain the polymer (A) having a polyether structure, so even though the amount of the conductive agent blended is larger than that of the example. First, the surface resistance value of the adhesive sheet increased. Furthermore, it was considered that the durability as an optical laminate was reduced because the amount of the conductive agent was large.

[Preparation of (meth)acrylic polymer B]
The weight-average molecular weight ( A solution of (meth)acrylic polymer B with Mw) 1.8 million and Mw/Mn=3.5 was prepared.

[Preparation of (meth)acrylic polymer C]
The monomer mixture charged into the flask was 60 parts by weight of MEA, 20 parts by weight of ethyl acrylate, 14 parts by weight of n-butyl acrylate (BA), 5 parts by weight of phenoxyethyl acrylate, and 1 part by weight of HBA. A solution of (meth)acrylic polymer C having a weight average molecular weight (Mw) of 2 million and Mw/Mn=3.9 was prepared in the same manner as in the preparation of Polymer A1.

[Preparation of (meth)acrylic adhesive composition]
(sample b1)
0.3 parts by weight of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals, Takenate D-110N; trimethylolpropane/xylylene diisocyanate adduct) per 100 parts by weight of the solid content of the solution of (meth)acrylic polymer B By further blending 5 parts by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI; manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Elexel AS-110) as a conductive agent, sample b1 was obtained. A solution of a (meth)acrylic adhesive composition was prepared.

(Sample b2)
Samples except that 0.1 parts by weight of a peroxide crosslinking agent (manufactured by NOF Corporation, Niper BMT) and 0.5 parts by weight of an antioxidant (manufactured by BASF, Irganox 1010, molecular weight 1178) were further blended. A solution of the (meth)acrylic adhesive composition of sample b2 was prepared in the same manner as b1.

(Sample b3)
As shown in Table 4 below, the above-described isocyanate crosslinking agent, peroxide crosslinking agent, and conductive agent are blended with 100 parts by weight of the solid content of the solution of (meth)acrylic polymer B. A solution of the (meth)acrylic adhesive composition of sample b3 was prepared.

(sample b4)
As shown in Table 4 below, the above-described isocyanate crosslinking agent, peroxide crosslinking agent, and conductive agent were blended with 100 parts by weight of the solid content of the solution of (meth)acrylic polymer C. A solution of the (meth)acrylic adhesive composition of sample b4 was prepared.

<Measurement of relative dielectric constant>
The dielectric constant P at a frequency of 100 kHz was measured for (meth)acrylic polymer B of Examples and Comparative Examples by the method described above.

[Preparation of adhesive sheet]
A solution of each adhesive composition was applied to one side of a polyethylene terephthalate film (release liner; manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) whose surface had been treated with a silicone release agent until the thickness of the adhesive sheet after drying was 20 μm. It was applied like this. The obtained coating film was dried at 155° C. for 1 minute to form an adhesive sheet on the surface of the release liner.

<Measurement of surface resistance value>
For each adhesive composition, the surface resistance value when an adhesive sheet was formed was determined by using the adhesive sheet prepared above as a test sample, using Hiresta MCP-HT450 manufactured by Mitsubishi Chemical Analytic Corporation, and applying an applied voltage of 250 V. The measurement was performed under the condition that the application time was 10 seconds. The surface resistance value was measured under an environment of a temperature of 25° C.±5° C. and a relative humidity of 50±5%.

<Preparation of polarizing plate A>
As the polarizing plate A, the above-mentioned polarizing plate A was used.

<Preparation of polarizing plate B>
A polarizer with a thickness of 28 μm was obtained in the same manner as in the preparation of polarizing plate A, except that the thickness of the polyvinyl alcohol film used in the preparation of the polarizer and the iodine concentration were changed. Next, two types of transparent protective films were attached to the obtained polarizer in the same manner as in the production of polarizing plate A to produce polarizing plate B.

<Preparation of optical laminate>
Each of the adhesive sheets of Examples and Comparative Examples formed on a release liner was transferred onto the polarizing plate prepared above to produce a polarizing plate with an adhesive sheet. Note that the adhesive sheet was transferred onto the surface of a polarizing plate on the side of a transparent protective film made of a modified acrylic polymer. After that, in the polarizing plate with an adhesive sheet, an OCA layer made of an optically transparent adhesive (OCA) is formed on the surface of the polarizing plate opposite to the adhesive sheet, and the OCA layer, the polarizing plate, the adhesive sheet, and A laminate was prepared in which release liners were laminated in this order. The OCA layer contained butyl acrylate as the base polymer.

Next, the release liner was peeled off from this laminate. In the laminate from which the release liner was removed, glass was laminated on the surface of the adhesive sheet opposite to the polarizing plate and on the surface of the OCA layer opposite to the polarizing plate. In this way, optical laminates of Examples and Comparative Examples were produced in which glass, OCA layer, polarizing plate, adhesive sheet, and glass were laminated in this order.

<Coloring a>
The coloring of the optical laminate at high temperatures was evaluated using the same method as in <Coloring> above, except that a heating test was conducted in which the laminate for evaluation was left in a hot air oven maintained at 95° C. for 500 hours. The light transmittance of the laminate was measured near the center where the coloration was considered to be the most advanced. Assuming that the light transmittance before the heating test is Tsa ₀ and the light transmittance after the heating test is Tsa ₅₀₀ , evaluate the degree of coloring of the optical laminate under high temperature based on the value of the difference ΔTsa = Tsa ₅₀₀ - Tsa ₀ . did.
A: ΔTsa is more than 0% B: ΔTsa is 0% or less - more than 3% C: ΔTsa is -3% or less - more than 10% D: ΔTsa is -10% or less

<Coloring b>
The coloring of the optical laminate at high temperatures was evaluated by the same method as in <Coloring> above, except that a heating test was conducted in which the laminate for evaluation was left in a hot air oven maintained at 105° C. for 500 hours. The light transmittance of the laminate was measured near the center where the coloration was considered to be the most advanced. The light transmittance before the heating test is Tsb ₀ and the light transmittance after the heating test is Tsb ₅₀₀ , and the degree of coloring of the optical laminate under high temperature is evaluated based on the value of the difference ΔTsb = Tsb ₅₀₀ - Tsb ₀ . did.
A: ΔTsb is more than 0% B: ΔTsb is 0% or less - more than 3% C: ΔTsb is -3% or less - more than 10% D: ΔTsb is -10% or less

<Durability (high temperature durability) B>
Except for using the optical laminates of Examples B1 to B4 and Comparative Example B1, the durability (high-temperature durability) of the optical laminate was evaluated by the same method as in <Durability (high-temperature durability) A> above. .

<Measurement of formic acid content and acetic acid content in adhesive sheet>
First, a heating test was conducted in which each of the pressure-sensitive adhesive sheets of Examples and Comparative Examples formed on a release liner was left in a hot air oven maintained at 105° C. for 120 hours.

Approximately 0.1 g of the adhesive sheet after the heating test was weighed and added to the PP container. 50 mL of pure water was further added to this PP container, and the PP container was covered. Then, the PP container was placed in a dryer and heated at 120° C. for 1 hour to perform extraction. The obtained extract was filtered through a membrane filter to obtain a filtrate. An analysis solution for ion chromatography measurement was prepared by removing organic matter from the obtained filtrate using a solid phase extraction cartridge. This analysis solution was used for ion chromatography measurement (IC measurement). The content of formic acid contained in the adhesive sheet and the content of acetic acid contained in the adhesive sheet were determined by quantifying formic acid ions and acetate ions in the analysis solution using an ion chromatograph. For the ion chromatography measurement, ICS-3000 manufactured by Thermo Fisher Scientific was used.

<Measurement of formic acid content in polarizing plate>
First, a heating test was conducted in which the optical laminates of Examples and Comparative Examples were left in a hot air oven maintained at 105° C. for 120 hours. After the optical laminate after the heating test is immersed in liquid nitrogen and frozen, the glass formed on the surface of the OCA layer is peeled off from the optical laminate, and the OCA layer is scraped off to remove the laminate. Obtained. Next, in this laminate, the glass formed on the surface of the adhesive sheet was peeled off, and the adhesive sheet was physically removed from the polarizing plate. In this way, a polarizing plate was obtained from the optical laminate. An analysis solution for ion chromatography measurement was prepared by the method described above, except that the obtained polarizing plate was used. The content of formic acid contained in the polarizing plate was determined by quantifying formic acid ions using an ion chromatograph. The apparatus used for ion chromatography measurements was as described above.

Tables 5 and 6 show the evaluation results of each characteristic of the pressure-sensitive adhesive sheets and optical laminates produced in Examples and Comparative Examples. In Table 5, "<2.5" indicates that the formic acid content or acetic acid content was below the detection limit.

As shown in Tables 5 and 6, in the optical laminate of each example, the content of formic acid contained in the adhesive sheet was 1000 ppm or less on a mass basis, compared to the optical laminate of Comparative Example B1, and Coloring was suppressed. In addition, as shown in Table 6, in the optical laminates of each example, the content of formic acid contained in the polarizing plate was 70 ppm or less on a mass basis, and coloration at high temperatures was suppressed. Note that in the optical laminates of Examples and Comparative Examples, the content of acetic acid was low even after being exposed to high-temperature environments.

The adhesive composition of the present invention can be used, for example, in image display devices such as EL displays and liquid crystal displays.

1 Adhesive sheet 2 Polarizing plate 10A, 10B, 10C, 10D Optical laminate 11A, 11B, 11C Image display panel

Claims (36)

An optical laminate comprising an adhesive sheet formed from an adhesive composition and an optical film ,
The optical film is a polarizing plate containing a polarizer,
The pressure-sensitive adhesive composition includes:
Contains a polymer (A) having a polyether structure as a main component,
further comprising a conductive agent and a radical scavenger,
The polymer (A) has a structural unit derived from a monomer shown in the following formula (1),

In the formula (1), R ¹ is a hydrogen atom or a methyl group, R ² is an alkyl group that may be linear or branched, and n is an alkyl group of 1 to 15. is an integer,
The content of the structural unit in the polymer (A) is 25% by weight or more,
The adhesive sheet is an optical laminate having a surface resistance value of 1×10 ¹⁰ Ω/□ or less. The optical laminate according to claim 1, wherein the surface resistance value is 1×10 ⁹ Ω/□ or less. The optical laminate according to claim 1, wherein the radical scavenger is an antioxidant. The optical laminate according to claim 1, wherein the radical scavenger has a molecular weight of 1000 or less. The optical laminate according to claim 1, wherein the amount of the radical scavenger in the adhesive composition is less than 5 parts by weight based on 100 parts by weight of the polymer (A). The optical laminate according to claim 1, wherein the amount of the conductive agent in the adhesive composition is 8 parts by weight or less based on 100 parts by weight of the polymer (A). The optical laminate according to claim 1, wherein the pressure-sensitive adhesive composition further contains an isocyanate-based crosslinking agent. The optical laminate according to claim 1, wherein the adhesive composition further contains a peroxide-based crosslinking agent. The optical laminate according to claim 1, wherein the adhesive composition is a solvent type. The adhesive composition includes a polymerization initiator for forming the polymer (A), and the polymerization initiator includes at least one selected from the group consisting of a thermal polymerization initiator and a photopolymerization initiator. The optical laminate according to claim 1. The optical laminate according to claim 10 , wherein the polymerization initiator includes at least one selected from the group consisting of an azo polymerization initiator, a peroxide polymerization initiator, and a redox polymerization initiator. The photopolymerization initiator includes a benzoin ether photopolymerization initiator, an acetophenone photopolymerization initiator, an α-ketol photopolymerization initiator, an aromatic sulfonyl chloride photopolymerization initiator, a photoactive oxime photopolymerization initiator, Claim 1 containing at least one selected from the group consisting of a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. The optical laminate according to 0 . Further includes a protective film,
The optical laminate according to claim 1 , wherein the protective film is disposed on at least one surface of the polarizer. An image display panel comprising the optical laminate according to claim 1 . An image display device comprising the image display panel according to claim 14 . An optical laminate comprising an adhesive sheet formed from an adhesive composition and an optical film ,
The optical film is a polarizing plate containing a polarizer,
The adhesive composition includes a polymer (B),
The polymer (B) has a structural unit derived from a monomer shown in the following formula (1),

In the formula (1), R ¹ is a hydrogen atom or a methyl group, R ² is an alkyl group that may be linear or branched, and n is an alkyl group of 1 to 15. is an integer,
The content of the structural unit in the polymer (B) is 25% by weight or more,
The relative dielectric constant of the polymer (B) at a frequency of 100 kHz is 5.0 or more,
An optical laminate, wherein after heating the adhesive sheet at 105° C. for 120 hours, the adhesive sheet contains 1000 ppm or less formic acid on a mass basis. The optical laminate according to claim 16 , wherein after heating the adhesive sheet at 105° C. for 120 hours, the adhesive sheet contains 100 ppm or less formic acid on a mass basis. The optical laminate according to claim 16 , wherein the adhesive composition further contains a peroxide-based crosslinking agent and a radical scavenger. The optical laminate according to claim 18 , wherein the radical scavenger is an antioxidant. The optical laminate according to claim 16 , wherein the pressure-sensitive adhesive composition further contains an isocyanate-based crosslinking agent. The adhesive composition includes a polymerization initiator for forming the polymer (B), and the polymerization initiator includes at least one selected from the group consisting of a thermal polymerization initiator and a photopolymerization initiator. The optical laminate according to claim 16 . The optical laminate according to claim 21 , wherein the polymerization initiator includes at least one selected from the group consisting of an azo polymerization initiator, a peroxide polymerization initiator, and a redox polymerization initiator. The photopolymerization initiator includes a benzoin ether photopolymerization initiator, an acetophenone photopolymerization initiator, an α-ketol photopolymerization initiator, an aromatic sulfonyl chloride photopolymerization initiator, a photoactive oxime photopolymerization initiator, Claim 21 containing at least one selected from the group consisting of a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. The optical laminate described in. The optical laminate according to claim 16 , wherein after heating the optical laminate at 105° C. for 120 hours, the polarizing plate contains 70 ppm or less formic acid on a mass basis. When the light transmittance after a heating test in which the optical laminate is heated at 95° C. for 500 hours is defined as Tsa ₅₀₀ , and the light transmittance of the optical laminate before the heating test is defined as Tsa ₀ , ΔTsa=Tsa 17. The optical laminate according to claim 16 , wherein ₅₀₀ -Tsa ₀ satisfies ΔTsa>0%. Further includes a protective film,
The optical laminate according to claim 16 , wherein the protective film is disposed on at least one surface of the polarizer. An image display panel comprising the optical laminate according to claim 16 . An image display device comprising the image display panel according to claim 27 . An optical laminate including an adhesive sheet and an optical film,
The pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a polymer (C),
The polymer (C) has a structural unit derived from a monomer shown in the following formula (1),

In the formula (1), R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group that may be linear or branched, and n is an alkyl group of 1 to 15. is an integer,
The relative dielectric constant of the polymer (C) at a frequency of 100 kHz is 5.0 or more,
The content of the structural unit in the polymer (C) is 15 to 99.5% by weight or more,
The adhesive composition further includes a peroxide-based crosslinking agent, a radical scavenger, and an isocyanate-based crosslinking agent,
The optical film is a polarizing plate containing a polarizer,
After heating the optical laminate at 105° C. for 120 hours, the polarizing plate contains 70 ppm or less formic acid on a mass basis. The optical laminate according to claim 29 , wherein the polarizer has a thickness of 20 μm or less. The optical laminate according to claim 29 , wherein the radical scavenger is an antioxidant. The adhesive composition includes a polymerization initiator for forming the polymer (C), and the polymerization initiator includes at least one selected from the group consisting of a thermal polymerization initiator and a photopolymerization initiator. The optical laminate according to claim 29 . The optical laminate according to claim 32 , wherein the polymerization initiator includes at least one selected from the group consisting of an azo polymerization initiator, a peroxide polymerization initiator, and a redox polymerization initiator. The photopolymerization initiator includes a benzoin ether photopolymerization initiator, an acetophenone photopolymerization initiator, an α-ketol photopolymerization initiator, an aromatic sulfonyl chloride photopolymerization initiator, a photoactive oxime photopolymerization initiator, Claim 3 containing at least one selected from the group consisting of a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. 2. The optical laminate according to 2. An image display panel comprising the optical laminate according to claim 29 . An image display device comprising the image display panel according to claim 35 .

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