TW202321402A - Adhesive composition and adhesive sheet - Google Patents

Abstract

The present invention provides an adhesive composition with which it is possible to form an adhesive having both a high refractive index and low elastic modulus. Provided is an adhesive composition including an acrylic polymer and a plasticizer. A monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1). The plasticizer is a liquid compound at 30 DEG C and has two or more double bond-containing rings.

Description

Adhesive composition and adhesive sheet

The present invention relates to an adhesive composition and an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2021-127817 filed on August 3, 2021 and Japanese Patent Application No. 2022-061160 filed on March 31, 2022, and its The entire contents of the applications such as , etc. are incorporated in this specification as a reference.

In general, adhesives (also called pressure-sensitive adhesives, hereinafter also the same) are in the state of soft solid (viscoelastic body) in the temperature range around room temperature, and have the property of being easily adhered to the adherend by pressure. nature. Taking advantage of this property, adhesives are widely used for the purpose of joining, fixing, and protecting in various industrial fields ranging from home appliances to automobiles, various machines, electric equipment, and electronic equipment. Examples of applications of the adhesive include bonding polarizing films, retardation films, cover window members, various other light-transmitting members, and other members in display devices such as liquid crystal display devices and organic EL display devices. Patent Documents 1 and 2 can be cited as technical documents related to adhesives for optical components. prior art literature patent documents

Patent Document 1: Japanese Patent Application Publication No. 2014-169382 Patent Document 2: Japanese Patent Application Publication No. 2017-128732

The problem to be solved by the invention Patent Documents 1 and 2 disclose an adhesive composition mainly composed of a (meth)acrylate polymer and an adhesive obtained by crosslinking the adhesive composition. The (meth)acrylate polymer The compound contains a monomer having a plurality of aromatic rings as a monomer unit; and it is proposed that the refractive index of the adhesive be 1.50 or more, preferably 1.51 or more, by using a monomer having a plurality of aromatic rings. For example, it is known that there are materials with a high refractive index among the materials that can be attached with adhesives such as optical components. If a general acrylic adhesive is used in the bonding of such high refractive index materials, the difference in refractive index between the two will This causes reflection at the interface. By using an adhesive having a high refractive index as the adhesive used for joining the above-mentioned high-refractive materials, etc., the above-mentioned interface reflection can be prevented or suppressed. In addition, the refractive index of the acrylic adhesive is usually about 1.47.

Adhesives with good flexibility can be suitably used depending on the place where they are applied or the way they are used. For example, in recent years, in terms of displays such as organic EL display devices that can be used in electronic devices such as smartphones, foldable displays or rollable displays have been put into practical use, so the adhesives used for the above applications must also be flexible and bendable repeatedly. The softness of the adherend. Adhesives with excellent flexibility are also easy to conform and adhere to surfaces with curved surfaces such as 3-dimensional shapes, so they are also suitable for electronic devices with curved surfaces. As for the adhesive having a high refractive index, if the flexibility can be improved, it can also be applied to the above-mentioned applications requiring flexibility, which is useful. However, the monomer component of the adhesive polymer or the high-refractive-index material that can be used as an additive for the adhesive tends to have a high glass transition temperature such as an aromatic ring, so the adhesive formed by using a high-refractive-index material will have an elastic modulus. Tendency to increase. In the design of adhesives, high refractive index and low modulus of elasticity have a trade-off relationship, and it will be beneficial in practical applications if an adhesive that takes both into account can be realized.

The present invention is created in view of the above circumstances, and aims to provide an adhesive composition that can form an adhesive with both high refractive index and low elastic modulus. Another object of the present invention is to provide an adhesive sheet comprising an adhesive layer formed from the above adhesive composition.

means to solve problems According to the specification, an adhesive composition comprising an acrylic polymer and a plasticizer is provided. The monomer component constituting the aforementioned acrylic polymer contains an aromatic ring-containing monomer (A1). Also, the aforementioned plasticizer is a compound having two or more double bond-containing rings and is liquid at 30°C. In the above-mentioned adhesive composition, the monomer component constituting the acrylic polymer includes the aromatic ring-containing monomer (A1), so it is suitable for forming an adhesive with a high refractive index. In addition, the above-mentioned adhesive composition contains a compound having two or more double bond-containing rings and is liquid at 30° C. as a plasticizer, so that an adhesive having a high refractive index and a low modulus of elasticity can be formed.

In several ideal aspects, the aforementioned compounds are liquid compounds at 20°C. By using a compound that is liquid at 20°C as a plasticizer, it is easy to form an adhesive with a low modulus of elasticity.

In several desirable aspects, the aforementioned plasticizer system contains more than 15 parts by weight relative to 100 parts by weight of the aforementioned acrylic polymer. In several aspects, the aforementioned plasticizer system contains more than 30 parts by weight relative to 100 parts by weight of the aforementioned acrylic polymer. According to the above-mentioned adhesive composition, an adhesive having both high refractive index and low elastic modulus can be suitably formed.

In some desirable aspects, the plasticizer has at least one ring selected from aromatic rings and heterocyclic rings as the double bond-containing ring. By using a compound having the above chemical structure as a plasticizer, an adhesive having both a high refractive index and a low modulus of elasticity can be easily obtained.

In several desirable aspects, the aforementioned plasticizer has a first double bond-containing ring and a second double bond-containing ring. Furthermore, the first double bond-containing ring and the second double bond-containing ring are connected through a linking group having 1 to 5 atoms. Since the plasticizer has a linking group between two or more double bond-containing rings, it has a high refractive index and tends to lower the modulus of elasticity of the adhesive. By using the plasticizer of the structure, the high refractive index and the low elastic modulus can be more balanced.

In several aspects, the molecular weight of the aforementioned plasticizer is in the range of 100-2000. A plasticizer having a molecular weight within the above-mentioned range is easy to be compatible with the adhesive, and is easy to exert a plasticizing effect.

In several aspects, the monomer component constituting the aforementioned acrylic polymer further contains a monomer (A2) in addition to the aforementioned aromatic ring-containing monomer (A1), and the monomer (A2) has at least one of a hydroxyl group and a carboxyl group. By. By using the acrylic polymer having the above-mentioned monomer composition, a high-refractive-index adhesive having both flexibility and good cohesive force can be obtained suitably.

In several aspects, in the said monomer component, content of the said aromatic ring containing monomer (A1) is 60 weight% or more. By using the acrylic polymer whose polymerization rate of the aromatic ring containing monomer (A1) is 60 weight% or more, the adhesive agent which has a high refractive index can be obtained easily.

In some aspects, 50% by weight or more of the aromatic ring-containing monomers (A1) are monomers whose homopolymer glass transition temperature is 10° C. or lower. Thereby, even if the polymerization ratio of the aromatic ring-containing monomer (A1) is increased, a high refractive index and a low modulus of elasticity can still be balanced.

The adhesive composition disclosed herein preferably further includes a crosslinking agent. By using a cross-linking agent, moderate cohesiveness can be imparted to the adhesive, which improves the handling properties of the adhesive sheet during manufacture, processing, storage, and attachment to an adherend.

Also, according to the specification, there is provided an adhesive sheet comprising an adhesive layer composed of any adhesive disclosed herein (it may be an adhesive formed of any adhesive composition disclosed herein). The adhesive disclosed here can balance high refractive index and low elastic modulus. Therefore, the adhesive sheet containing the above-mentioned adhesive should have a high refractive index for folding display applications, etc., and can be suitable for applications that require repeated bending operations. Bonding or fixing, protection, etc. for the purpose of flexibility.

In addition, an appropriate combination of elements described in this specification may also be included in the scope of the invention for which patent protection is sought through this patent application.

Preferred embodiments of the present invention will be described below. Except for matters not specifically mentioned in this specification and necessary for the implementation of the present invention, those who are familiar with the art can understand it based on the teachings about the implementation of the invention contained in this specification and the technical common sense at the time of application. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the field. In addition, in the following drawings, members and locations that perform the same functions are sometimes described with the same symbols, and repeated descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematic for clearly explaining the present invention, and do not completely and accurately represent the dimensions or scales of products actually provided.

In this specification, the "base polymer" of the adhesive means the main component of the rubber-like polymer contained in the adhesive. The aforementioned rubber-like polymer refers to a polymer exhibiting rubber elasticity in a temperature region around room temperature. Moreover, in this specification, a "main component" means containing more than 50 weight% of a component unless it mentions especially.

In this specification, "acrylic polymer" means a polymer comprising, as a monomer unit constituting the polymer, a monomer unit derived from at least one (methyl) Acryl monomer. Hereinafter, a monomer having at least one (meth)acryl group in one molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer comprising a monomer unit derived from an acrylic monomer. Typical examples of acrylic polymers include acrylic monomers in which more than 50% by weight (preferably more than 70% by weight, such as more than 90% by weight) of the monomer components constituting the polymer are acrylic monomers.

Moreover, in this specification, "acrylic monomer" means the monomer which has at least 1 (meth)acryl group in 1 molecule. Here, "(meth)acryl" refers to both acryl and methacryl. Therefore, the concept of acrylic monomers mentioned here may include both monomers with acryl groups (acrylic monomers) and monomers with methacryl groups (methacrylic monomers). Similarly, in this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid, and "(meth)acrylate" means both acrylate and methacrylate. The same applies to other similar expressions.

＜Adhesive composition＞ The adhesive composition disclosed here is not particularly limited as long as it can form an adhesive containing an acrylic polymer (preferably an adhesive containing the acrylic polymer as a base polymer). The above-mentioned adhesive composition can be, for example, the following various forms: a solvent-based adhesive composition in which an adhesive-forming component is contained in an organic solvent, and an active energy prepared to be hardened by active energy rays such as ultraviolet rays or radiation to form an adhesive. Line-curing adhesive composition, water-dispersed adhesive composition in which adhesive forming components are dispersed in water, hot-melt adhesive composition that forms an adhesive when applied in a heated and molten state and cooled to around room temperature things etc. The technique disclosed here can be suitably implemented using a solvent-based adhesive composition, but is not particularly limited. In an aspect having a solvent-based adhesive layer formed of a solvent-based adhesive composition, it is possible to suitably achieve both a high refractive index and a low modulus of elasticity.

The adhesive composition disclosed here contains an aromatic ring-containing monomer (A1) as a monomer component constituting the above-mentioned acrylic polymer. Here, the term "monomer components constituting the acrylic polymer" in this specification means whether it is contained in the adhesive composition in the form of a preformed polymer (which may be an oligomer) or is not The form of the polymerized monomer is included in the adhesive composition, and all monomers that constitute the repeating unit of the acrylic polymer in the adhesive formed from the adhesive composition. That is, the monomer component constituting the acrylic polymer may be contained in the above-mentioned adhesive composition in any form of polymer, unpolymerized, or partially polymerized. From the viewpoint of easiness of preparation of the adhesive composition, etc., it is preferable to include substantially all of the monomer components (for example, 95% by weight or more, preferably 99% by weight or more) in the form of a polymer in several aspects. adhesive composition.

(monomer (A1)) As the monomer (A1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule can be used. A monomer (A1) can be used individually by 1 type or in combination of 2 or more types.

Examples of the above-mentioned ethylenically unsaturated groups include (meth)acryl, vinyl, (meth)allyl and the like. A (meth)acryl group is preferable from the viewpoint of polymerization reactivity, and an acryl group is preferable from the viewpoint of flexibility or adhesiveness. As the monomer (A1), a compound (that is, a monofunctional monomer) in which the number of ethylenically unsaturated groups contained in 1 molecule is 1 can be suitably used from the viewpoint of suppressing a reduction in the flexibility of the adhesive.

The number of aromatic rings contained in the molecule of Compound 1 which can be used as a monomer (A1) may be 1 or 2 or more. The upper limit of the number of the above-mentioned aromatic rings is not particularly limited, and may be 16 or less, for example. In several aspects, the number of the above-mentioned aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, from the viewpoint of the ease of preparation of the adhesive composition or the transparency of the adhesive. It may be 5 or less, 4 or less, 3 or less, or 2 or less.

The aromatic ring of the compound that can be used as the monomer (A1) can also be: benzene ring (which can be a part of the biphenyl structure or the fluorine structure); naphthalene ring, indene ring, azulene ring, anthracene ring, phenanthrene ring A carbocyclic ring such as a condensed ring of a ring; it can also be a pyridine ring, a pyrimidine ring, a pyridine ring, a pyridyl ring, a three-ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, a azole ring, or an iso Heterocycles such as azole ring, thiazole ring, and thiophene ring. The heteroatoms contained as ring constituting atoms in the heterocyclic ring may be, for example, one or two or more kinds selected from the group consisting of nitrogen, sulfur and oxygen. In several aspects, the above-mentioned heteroatoms constituting the heterocycle may be one or both of nitrogen and sulfur. The monomer (A1) may have, for example, a structure in which one or more carbocycles and one or more heterocycles are condensed like a dinaphthothiophene structure.

The aforementioned aromatic ring (preferably a carbocyclic ring) may have one, two or more substituents, or no substituents on ring constituting atoms. When there is a substituent, the substituent can be exemplified by an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyl group Oxygen, etc., but not limited thereto. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1-4, more preferably 1-3, for example, 1 or 2. In several aspects, the above-mentioned aromatic ring may be an aromatic ring having no substituent on the ring constituting atom, or may have an aromatic ring selected from an alkyl group, an alkoxy group, and a halogen atom (such as bromine) on the ring constituting atom. Atom) aromatic ring with 1 or more substituents in the group. In addition, when the aromatic ring of the monomer (A1) has a substituent on the ring constituting atom, it means that the aromatic ring has a substituent other than a substituent having an ethylenically unsaturated group.

The aromatic ring and the ethylenically unsaturated group may be bonded directly or bonded via a linking group. The above-mentioned linking group may include, for example, 1 or 2 selected from alkylene, oxyalkylene, poly(oxyalkylene) group, phenyl, alkylphenyl, alkoxyphenyl, and such groups. One or more groups of structures in which the above hydrogen atoms are replaced by hydroxyl groups (such as hydroxyalkylene groups), oxy (-O-groups), thiooxyl groups (-S-groups), etc. . In several aspects, an aromatic ring-containing monomer having a structure in which an aromatic ring is directly bonded to an ethylenically unsaturated group, or an aromatic ring-containing monomer selected from an alkylene group, an oxyalkylene group, and a poly(oxyalkylene group) may be suitably used. An aromatic ring-containing monomer having a structure in which a linking group in a group constitutes a group and is bonded. The number of carbon atoms in the above-mentioned alkylene group and the above-mentioned oxyalkylene group is preferably 1-4, more preferably 1-3, for example, 1 or 2. The repeating number of the oxyalkylene units in the poly(oxyalkylene) group may be, for example, 2-3.

Examples of compounds that can be suitably used as the monomer (A1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylate and the aromatic ring-containing vinyl compound can be used individually by 1 type or in combination of 2 or more types. One or more aromatic ring-containing (meth)acrylates and one or more aromatic ring-containing vinyl compounds may be used in combination.

In some aspects, a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be used as the monomer (A1) from the viewpoint that a higher effect of increasing the refractive index can be easily obtained. Examples of monomers having two or more aromatic rings in one molecule (monomers containing multiple aromatic rings) include monomers having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, monomers having two The above monomers with the structure of direct (that is, without intervening other atoms) chemical bonding of non-condensed aromatic rings, monomers with condensed aromatic ring structures, monomers with fennel structures, monomers with dinaphthothiophene structures, monomers with Monomers with dibenzothiophene structure, etc. The monomer containing a plurality of aromatic rings can be used alone or in combination of two or more.

The above linking group can be, for example: oxy (-O-), thiooxy (-S-), oxyalkylene (such as -O-(CH ₂ ) _n -group, where n is 1~3, It is preferably 1), thiooxyalkylene (such as -S-(CH ₂ ) _n -group, where n is 1~3, preferably 1), straight chain alkylene (ie -(CH ₂ ) _n -group, where n is 1~6, preferably 1~3), the alkylene group in the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group and the above-mentioned linear chain alkylene group has been partially or fully halogenated group etc. From the viewpoint of the flexibility of the adhesive, etc., suitable examples of the above linking group include an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. Specific examples of monomers having a structure in which two or more non-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate (such as m-phenoxybenzyl (meth)acrylate) , thiophenoxybenzyl (meth)acrylate, benzylbenzyl (meth)acrylate, etc.

The above-mentioned monomers with two or more non-condensed aromatic rings directly chemically bonded can be, for example, biphenyl-containing (meth)acrylates, triphenyl-containing (meth)acrylates, vinyl-containing biphenyls wait. Specific examples include o-phenylphenol (meth)acrylate, biphenylmethyl (meth)acrylate, and the like.

Examples of the above-mentioned monomer having a condensed aromatic ring structure include naphthalene ring-containing (meth)acrylate, anthracene ring-containing (meth)acrylate, vinyl naphthalene, vinyl anthracene, and the like. Specific examples can be cited: 1-naphthylmethyl (meth)acrylate (alias: 1-naphthylmethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthylethyl ( Meth)acrylate, 2-naphthyloxyethyl acrylate, 2-(4-methoxy-1-naphthyloxy)ethyl (meth)acrylate, and the like.

Specific examples of the above-mentioned monomers having a fennel structure include 9,9-bis(4-hydroxyphenyl) fennel (meth)acrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl ] fennel (meth) acrylate, etc. In addition, a monomer having a fennel structure is included in the concept of a monomer having a structure in which two or more non-condensed aromatic rings are directly chemically bonded because it contains a structural portion in which two benzene rings are directly chemically bonded.

The aforementioned monomers having a dinaphthothiophene structure include (meth)acryl-containing dinaphthothiophene, vinyl-containing dinaphthothiophene, (meth)allyl-containing dinaphthothiophene, and the like. Specific examples include: (meth)acryloxymethyl dinaphthothiophene (for example, CH ₂ CH(R ¹ )C(O)OCH ₂ - A compound of the structure; here, R ¹ is a hydrogen atom or a methyl group), (meth)acryloxyethyl dinaphthothiophene (for example, CH is bonded to the 5-position or 6-position of the dinaphthothiophene ring ₂ CH(R ¹ )C(O)OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ - compounds; here, R ¹ is a hydrogen atom or a methyl group) , Vinyl dinaphthothiophene (for example, a compound having a structure in which a vinyl group is bonded to the 5- or 6-position of the naphthothiophene ring), (meth)allyloxy dinaphthothiophene, and the like. In addition, the monomer system having a dinaphthothiophene structure includes a naphthalene structure and a condensed structure having a thiophene ring and two naphthalene structures, and is also included in the above-mentioned concept of a monomer having a condensed aromatic ring structure .

The aforementioned monomers having a dibenzothiophene structure include (meth)acryl-containing dibenzothiophene, vinyl-containing dibenzothiophene, and the like. In addition, since a monomer having a dibenzothiophene structure has a condensed structure of a thiophene ring and two benzene rings, it is included in the concept of the above-mentioned monomer having a condensed aromatic ring structure. In addition, neither the dinaphthothiophene structure nor the dibenzothiophene structure belongs to the structure in which two or more non-condensed aromatic rings are directly chemically bonded.

In several ideal aspects, the monomer (A1) can use the monomer which has 1 aromatic ring (preferably carbocyclic ring) in 1 molecule. A monomer having one aromatic ring in one molecule (a monomer containing an odd number of aromatic rings) contributes to, for example, improving the flexibility of an adhesive, adjusting adhesive properties, improving transparency, and the like. Monomers containing an odd number of aromatic rings can be used alone or in combination of two or more. In some aspects, from the viewpoint of increasing the refractive index of the adhesive, a monomer having one aromatic ring in one molecule may be used in combination with a monomer including a plurality of aromatic rings.

Examples of monomers having one aromatic ring in one molecule include: benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (methyl) base) acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, Carbon-containing aromatic ring (meth)acrylates such as chlorobenzyl (meth)acrylate; 2-(4,6-dibromo-2-secondary butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, 6-(4,6-dibromo-2-secondary butylphenoxy)hexyl ( Meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, 2 , 6-dibromo-4-dodecylphenyl acrylate and other bromine-substituted aromatic ring (meth)acrylates; styrene, α-methylstyrene, vinyltoluene, tertiary butylstyrene, etc. Vinyl compounds with carbon aromatic rings; N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrrole, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole and other heteroaromatic rings have vinyl substituents compounds etc.

As the monomer (A1), a monomer having a structure in which an oxyethylene chain is sandwiched between the ethylenically unsaturated group and the aromatic ring in the above-mentioned various aromatic ring-containing monomers can also be used. A monomer in which an oxyethylidene chain is sandwiched between an ethylenically unsaturated group and an aromatic ring as described above can be regarded as an ethoxylate of the original monomer. The repetition number of the oxyethylene unit (-CH ₂ CH ₂ O-) in the oxyethylene chain is typically 1-4, preferably 1-3, more preferably 1-2, for example 1. Specific examples of ethoxylated aromatic ring-containing monomers include: ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated methyl Phenol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol di(meth)acrylate, and the like.

The content of the monomer containing multiple aromatic rings in the monomer (A1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In several aspects, the content of the monomer containing multiple aromatic rings in the monomer (A1) may be, for example, 50% by weight or more, and from the viewpoint of easily obtaining a higher refractive index, it is preferably 70% by weight The above may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. The monomer (A1) may be substantially 100% by weight of a monomer containing a plurality of aromatic rings. That is, as the monomer (A1), only one or two or more monomers containing a plurality of aromatic rings may be used. Also, in several aspects, for example, considering the high refractive index and low elastic modulus, and further considering the balance with adhesive force if necessary, the monomer containing multiple aromatic rings in the monomer (A1) The body content can be less than 100% by weight, 98% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 65% by weight or less, 50% by weight or less , may be 25% by weight or less, or may be 10% by weight or less. The technology disclosed here can be implemented even when the content of the monomer containing a plurality of aromatic rings in the monomer (A1) is less than 5% by weight. A monomer containing a plurality of aromatic rings may not be used.

The content of the monomer containing multiple aromatic rings in the monomer components constituting the acrylic polymer is not particularly limited, and it can be set to achieve an adhesive with both the desired refractive index and elastic modulus. The content of the monomer containing a plurality of aromatic rings in the above-mentioned monomer components may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In several aspects, from the viewpoint of easily realizing an adhesive with a higher refractive index, the content of the monomer containing multiple aromatic rings in the above-mentioned monomer components can be, for example, more than 35% by weight, more than 50% by weight It is advantageous, preferably more than 70% by weight, can be more than 75% by weight, can be more than 85% by weight, can be more than 90% by weight, can also be more than 91% by weight, more than 92% by weight, more than 93% by weight, 94% by weight % by weight or more, 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more. The content of the monomer containing multiple aromatic rings in the above-mentioned monomer components is set at about 99% by weight or less in consideration of the high refractive index and low elastic modulus, and if necessary, further considering the balance with the adhesive force. Advantageously, it should be less than 98% by weight, more preferably less than 96% by weight, it can be less than 93% by weight, it can be less than 90% by weight, it can be less than 85% by weight, it can be less than 80% by weight, or it can be 75% by weight or less. In some aspects, from the viewpoint of easy realization of higher adhesive properties and/or optical properties (such as transparency), the content of the monomer containing multiple aromatic rings in the above-mentioned monomer components may be 70% by weight The following may be 60% by weight or less, 50% by weight or less, 40% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technique disclosed here can be carried out even when the content of the monomer containing multiple aromatic rings in the above-mentioned monomer component is less than 3% by weight.

The content of the monomer containing an odd number of aromatic rings in the monomer (A1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In several aspects, the content of the monomer containing an odd number of aromatic rings in the monomer (A1) may be, for example, 50% by weight or more, and from the viewpoint of easily obtaining a higher refractive index, it is preferably 70% by weight The above may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. The monomer (A1) may be substantially 100% by weight of a monomer containing an odd number of aromatic rings. That is, as the monomer (A1), only one or two or more monomers containing an odd number of aromatic rings may be used. Also, in several aspects, for example, considering the high refractive index and low elastic modulus, and further considering the balance with the adhesive force if necessary, the monomer containing an odd number of aromatic rings in the monomer (A1) The body content can be less than 100% by weight, 98% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 65% by weight or less, 50% by weight or less , may be 25% by weight or less, or may be 10% by weight or less. The technology disclosed here can be implemented even if the content of the monomer containing an odd number of aromatic rings in the monomer (A1) is less than 5% by weight. Monomers containing an odd number of aromatic rings may not be used.

The content of monomers containing an odd number of aromatic rings in the monomer components constituting the acrylic polymer is not particularly limited, and it can be set to achieve an adhesive with both the desired refractive index and elastic modulus. The content of the monomer containing an odd number of aromatic rings in the above-mentioned monomer components may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In several aspects, from the viewpoint of easily realizing an adhesive with a higher refractive index, the content of monomers containing an odd number of aromatic rings in the above-mentioned monomer components can be, for example, more than 35% by weight, more than 50% by weight It is advantageous, preferably more than 60% by weight, more preferably more than 70% by weight, can be more than 75% by weight, can be more than 85% by weight, can be more than 90% by weight, can be more than 95% by weight, and can also be 98% by weight % by weight or more. The content of the monomer containing an odd number of aromatic rings in the above-mentioned monomer components can be set at about 99% by weight or less in consideration of the high refractive index and low elastic modulus, and if necessary, further considering the balance with the adhesive force , preferably set to 98% by weight or less, more preferably set to 96% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, or may be 75% by weight or less Weight% or less. In several aspects, the content of the monomer containing an odd number of aromatic rings in the above-mentioned monomer components may be 70% by weight from the viewpoint of easy realization of higher adhesive properties and/or optical properties (such as transparency) The following may be 60% by weight or less, 50% by weight or less, 40% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technology disclosed here can be carried out even when the content of the monomer containing an odd number of aromatic rings in the above-mentioned monomer components is less than 3% by weight.

In several aspects of the technology disclosed here, a high-refractive-index monomer can be suitably used as at least a part of the monomer (A1). Here, "high refractive index monomer" means a monomer whose refractive index is, for example, about 1.510 or higher, preferably about 1.530 or higher, more preferably about 1.550 or higher. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, but from the viewpoint of the ease of preparation of the adhesive composition or the ease of compatibility with the flexibility suitable as an adhesive, for example, it is 3.000 or less, and may be 2.500 Below, may be 2.000 or less, may be 1.900 or less, may be 1.800 or less, may be 1.700 or less. The high-refractive-index monomers can be used alone or in combination of two or more. In addition, the refractive index of a monomer was measured on conditions of a measurement wavelength of 589 nm and a measurement temperature of 25 degreeC using the Abbe refractometer. As the Abbe refractometer, model "DR-M4" manufactured by ATAGO Corporation or its equivalent can be used. When there is a nominal value of the refractive index at 25° C. provided from a manufacturer or the like, the nominal value may be adopted.

The said high-refractive-index monomer can suitably employ the one which has this refractive index among the compounds contained in the concept of the aromatic ring containing monomer (A1) disclosed here (for example, the compound and compound group exemplified above). Specific examples include: m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthyl methacrylate (refractive index: 1.595, Tg of homopolymer: 31 ℃), ethoxylated o-phenylphenol acrylate (repeating number of oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6 ℃), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35 ℃), 6-acryloxymethyl dinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacryloxymethyl dinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-propene Acyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloxyethyldinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, Refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793), etc., but not limited thereto.

The content of the high refractive index monomer (that is, the aromatic ring-containing monomer with a refractive index of about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more) in the monomer (A1) is not particularly limited, for example, it can be 5% by weight or more, may be 25% by weight or more, may be 35% by weight or more, and may be 40% by weight or more. In several aspects, from the viewpoint of easily obtaining a higher refractive index, the content of the high refractive index monomer in the monomer (A1) may be, for example, 50% by weight or more, preferably 70% by weight or more, and may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be a high refractive index monomer. Also, in several aspects, for example, from the perspective of high refractive index and low elastic modulus, and if necessary, to further balance the adhesive force, the content of the high refractive index monomer in the monomer (A1) It may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, and may be 65% by weight or less.

The content of the high-refractive-index monomer in the monomer components constituting the acrylic polymer is not particularly limited, and can be set to achieve an adhesive with both the desired refractive index and elastic modulus. In addition, if necessary, it can also be set in consideration of both adhesive properties (such as adhesive force, etc.) and/or optical properties (such as total light transmittance, haze value, etc.). The content of the high refractive index monomer in the above-mentioned monomer components may be, for example, not less than 3% by weight, not less than 10% by weight, or not less than 25% by weight. In several aspects, in the monomer components constituting the acrylic polymer, the content of the high refractive index monomer can be greater than 35% by weight, for example, and from the viewpoint of easily obtaining a higher refractive index, greater than 50% by weight is the best Advantageously, it is preferably more than 70% by weight, may be more than 75% by weight, may be more than 85% by weight, may be more than 90% by weight, or may be more than 95% by weight. The content of the high-refractive-index monomer in the above-mentioned monomer components is advantageously set to 99% by weight or less from the viewpoint of a high refractive index and a low elastic modulus, and if necessary, a balance between the adhesive force and the adhesive force. 98% by weight or less, preferably 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight the following.

In some ideal aspects, at least a part of the monomer (A1) is an aromatic ring-containing monomer whose Tg of the homopolymer is 10°C or lower (hereinafter referred to as "monomer L"). When increasing the aromatic ring-containing monomer (A1) in the monomer component (especially equivalent to at least one of the above-mentioned monomers containing multiple aromatic rings, monomers containing a single aromatic ring, and high-refractive index monomers) When the content of the aromatic ring-containing monomer (A1)) is increased, the storage elastic modulus G' of the adhesive tends to increase, but by using the monomer L as part or all of the monomer (A1), it can be suppressed The storage elastic modulus G' rises. Thereby, the low modulus of elasticity can be better maintained, and the refractive index can be increased. The Tg of the monomer L may be, for example, 5°C or lower, 0°C or lower, -10°C or lower, -20°C or lower, or -25°C or lower. The lower limit of the Tg of the monomer L is not particularly limited. Considering the balance with the effect of increasing the refractive index, in several aspects, the Tg of the monomer L may be -70°C or higher, -55°C or higher, or -45°C or higher. In several other aspects, the Tg of the monomer L may be, for example, -30°C or higher, -10°C or higher, 0°C or higher, or 3°C or higher. Monomer L can be used individually by 1 type or in combination of 2 or more types.

As the monomer L, one having such a Tg can be appropriately employed among compounds included in the concept of the aromatic ring-containing monomer (A1) disclosed here (for example, the compounds and compound groups exemplified above). Suitable examples of aromatic ring-containing monomers that can be used as the monomer L include: m-phenoxybenzyl acrylate (Tg of homopolymer: -35°C), benzyl acrylate (Tg of homopolymer: 6°C ), phenoxyethyl acrylate (Tg of homopolymer: 2°C), phenoxydiethylene glycol acrylate (Tg of homopolymer: -35°C).

The content of the monomer L in the monomer (A1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In several aspects, the content of monomer L in the monomer (A1) may be, for example, 50% by weight or more from the viewpoint of easily obtaining an adhesive having a high refractive index and a low elastic modulus at a higher level , and from the point of view of low elastic modulus, it is preferably 60% by weight or more, can be 70% by weight or more, can be 75% by weight or more, can be 85% by weight or more, can be 90% by weight or more, or can be More than 95% by weight. The monomer (A1) may be substantially 100% by weight of the monomer L. Also, in several aspects, for example, from the perspective of high refractive index and low elastic modulus, and if necessary, to further balance the adhesive force, the content of the monomer L in the monomer (A1) can be less than 100% by weight may be 98% by weight or less, 90% by weight or less, 80% by weight or less, or 65% by weight or less.

The content of the monomer L in the monomer components constituting the acrylic polymer may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In several aspects, from the viewpoint of easily obtaining an adhesive with a higher level of high refractive index and low modulus of elasticity, the content of monomer L in the monomer component can be greater than 35% by weight, for example, and From the point of view of increasing the refractive index, it is advantageous to be more than 50% by weight, preferably more than 70% by weight, it can be more than 75% by weight, it can be more than 85% by weight, it can be more than 90% by weight, and it can be 95% by weight above. The content of the monomer L in the above-mentioned monomer components is advantageously set to about 99% by weight or less from the viewpoint of balancing the high refractive index and the low elastic modulus, and further balancing the adhesive force if necessary. 98% by weight or less, preferably 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight the following.

In some aspects, from the viewpoint of lowering the modulus of elasticity, it is appropriate that the glass transition temperature Tg _A1 is about 20°C or lower depending on the composition of the monomer (A1), preferably 10°C or lower, for example, It may be below 5°C, may be below 0°C, may be below -10°C, may be below -20°C, or may be below -25°C. The lower limit of the glass transition temperature Tg _A1 is not particularly limited. Considering the balance with the effect of raising the refractive index, in several aspects, the glass transition temperature Tg _A1 may be, for example, not less than -70°C, not less than -55°C, or not less than -45°C. The technology disclosed here can be suitably implemented even when the glass transition temperature Tg _A1 is, for example, -40°C or higher, -35°C or higher, -33°C or higher, -30°C or higher, or -25°C or higher. In several other aspects, the glass transition temperature Tg _A1 may be, for example, not less than -10°C, not less than 0°C, or not less than 3°C.

Here, the glass transition temperature Tg _A1 based on the composition of the monomer (A1) means Tg obtained by the Fox formula described later based only on the composition of the monomer (A1) among the monomer components constituting the acrylic polymer. The glass transition temperature Tg _A1 can be obtained by applying the Fox formula only to the monomer (A1) in the monomer components constituting the acrylic polymer, and from the homopolymerization of each aromatic ring-containing monomer used as the monomer (A1) The glass transition temperature of the compound and the weight fraction of each aromatic ring-containing monomer in the total amount of the monomer (A1) were calculated. In an aspect using only one type of monomer as the monomer (A1), the Tg of the homopolymer of the monomer coincides with the glass transition temperature Tg _A1 .

In several aspects, the aromatic ring-containing monomer (A1) can combine monomer L (that is, an aromatic ring-containing monomer whose homopolymer Tg is below 10°C) and monomer H whose Tg is higher than 10°C to use. The Tg of monomer H may be higher than 10°C, higher than 15°C, or higher than 20°C, for example. By using the combination of monomer L and monomer H, in the adhesive with a high content of the aromatic ring-containing monomer (A1) in the monomer component, the high refractive index of the adhesive and the suitability for the adhesive can be achieved at a higher level. The softness of adhesion to the adherend. The usage ratio of the monomer L and the monomer H can be set so that the above effect can be exhibited suitably, and it is not specifically limited. For example, it is preferable to set the usage ratio of the monomer L to the monomer H so as to satisfy any one of the above-mentioned glass transition temperatures Tg _A1 .

In several aspects, the aromatic ring-containing monomer (A1) can be suitably selected from compounds that do not contain two or more non-condensed aromatic rings directly chemically bonded (such as a biphenyl structure). For example, it is preferably an acrylic polymer composed of monomer components of the following composition: the content of the compound containing two or more non-condensed aromatic rings directly chemically bonded is less than 5% by weight (preferably less than 3% by weight, It may also be 0% by weight). Limiting the usage amount of the compound containing two or more non-condensed aromatic rings directly chemically bonded as mentioned above is to achieve high refractive index and low modulus of elasticity, and to further balance the adhesion of the adhesive if necessary. From a point of view it is beneficial.

The content of the monomer (A1) in the monomer components constituting the acrylic polymer is not particularly limited, and it can be set to achieve both the desired refractive index and modulus of elasticity, as well as adhesive properties (such as adhesive force, etc.) and/or Adhesives with optical properties (such as total light transmittance, haze value, etc.). In several aspects, the content of the monomer (A1) in the above-mentioned monomer components may be, for example, 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, or 70% by weight %above. In several ideal forms, the content of the monomer (A1) in the monomer components constituting the acrylic polymer can be greater than 70% by weight, for example, it is appropriate to be more than 75% by weight; and because it is easy to obtain a higher refractive index From the point of view, it is preferably 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, may be 91% by weight or more, 92% by weight or more, 93% by weight or more, 94% by weight or more, or 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more. The content of the monomer (A1) in the above-mentioned monomer components is typically less than 100% by weight, and from the perspective of high refractive index and low elastic modulus, and if necessary, a further balance and consideration of adhesive force, about 99% by weight % or less is advantageous, preferably 98% by weight or less, more preferably 96% by weight or less, may be 93% by weight or less, and may be 90% by weight or less. In several aspects, from the viewpoint of easy realization of higher adhesive properties and/or optical properties (such as transparency), the content of the monomer (A1) in the above-mentioned monomer components may be less than 90% by weight, may be less than 85% by weight, or less than 80% by weight.

(monomer (A2)) In several desirable aspects, the monomer component constituting the acrylic polymer may further contain a monomer (A2) in addition to the above-mentioned monomer (A1). The said monomer (A2) is a monomer corresponding to at least one of the monomer which has a hydroxyl group (hydroxyl group-containing monomer) and the monomer which has a carboxyl group (carboxyl group-containing monomer). The aforementioned hydroxyl-containing monomer is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The aforementioned carboxyl group-containing monomer is a compound containing at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer (A2) can be used to introduce crosslinking points into the acrylic polymer, or to impart moderate cohesion to the adhesive. A monomer (A2) can be used individually by 1 type or in combination of 2 or more types. The monomer (A2) is typically a monomer not containing an aromatic ring.

Examples of the ethylenically unsaturated group that the monomer (A2) has include a (meth)acryl group, a vinyl group, a (meth)allyl group, and the like. A (meth)acryl group is preferable from the viewpoint of polymerization reactivity, and an acryl group is preferable from the viewpoint of low elastic modulus and adhesiveness. From the viewpoint of suppressing the lowering of the elastic modulus of the adhesive, as the monomer (A2), a compound (that is, a monofunctional monomer) in which the number of ethylenically unsaturated groups contained in 1 molecule is 1 can be suitably used.

In several aspects, the monomer (A2) can use a monomer having a long distance between an ethylenically unsaturated group (for example, (meth)acryl group) and a hydroxyl group and/or a carboxyl group. Thereby, in the aspect in which the above-mentioned hydroxyl group and/or carboxyl group are used for the crosslinking reaction, a highly flexible crosslinked structure can be easily obtained. For example, the number of atoms (typically carbon atoms or oxygen atoms) constituting the chain (connecting chain) linking the ethylenically unsaturated group with the hydroxyl group and/or carboxyl group can be 3 or more (for example, 4 or more, 5 or more, 6 or more). or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, or 19 or more) are used as monomers (A2) . The upper limit of the number of atoms constituting the linking chain is, for example, 45 or less, and may be 20 or less (for example, 19 or less, 18 or less, 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less or 8 or less). In addition, the number of atoms constituting the chain linking the ethylenically unsaturated group with the hydroxyl group and/or carboxyl group refers to the minimum number of atoms required to reach the hydroxyl group or carboxyl group from the ethylenically unsaturated group. For example, when the above-mentioned connecting chain is composed of straight-chain alkylene (ie -(CH ₂ ) _n -group), the number of n becomes the number of atoms constituting the above-mentioned connecting chain. For another example, when the above-mentioned linking chain is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of the sum of 2 carbon atoms and 1 oxygen atom constituting the oxyethylene group and the product of n ( 3n) becomes the number of atoms constituting the above-mentioned connecting chain. As the monomer (A2), there can be used an alkylene unit having at least one - for example - (CH ₂ ) _n - between the above-mentioned ethylenically unsaturated group and the above-mentioned hydroxyl and/or carboxyl group, or - (C _m H _2m O)-The oxyalkylene unit shown (for example, the oxyethylene unit in which m is 2 in the aforementioned formula, the oxypropylene unit in which m is 3 in the aforementioned formula, the oxypropylene unit in the aforementioned formula m is an oxybutylene unit of 4), but is not particularly limited. The number of the above-mentioned alkylene units or oxyalkylene units is not particularly limited, and may be more than 1 (for example, 1-15 or 1-10 or 2-6 or 2-4). In addition, n in the formula representing the above-mentioned alkylene unit is, for example, an integer of 1 to 10, and may be 2 or more, 3 or more, or 4 or more, and may be 6 or less, or 5 or less. In the formula representing the above-mentioned oxyalkylene unit, m is an integer of 2 or more, for example, an integer of 2-4. The monomer (A2) may contain ester bond or ether bond, thioether bond, aromatic ring, Aliphatic rings, heterocyclic rings (such as rings containing nitrogen atoms (N), oxygen atoms (O), and sulfur atoms (S)). Moreover, the above-mentioned alkylene unit or oxyalkylene unit may have a substituent.

Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyl (meth)acrylate Hexyl ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (methyl) ) acrylates and other hydroxyalkyl (meth)acrylates, subject to such limitations. Examples of hydroxyl-containing monomers that can be suitably used include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl acrylate (Tg: -15°C). From the viewpoint of improving flexibility at room temperature, 4-hydroxybutyl acrylate with a lower Tg is preferable. Also, in the aspect of using hydroxyalkyl (meth)acrylate as a hydroxyl group-containing monomer and utilizing the hydroxyl group in a crosslinking reaction, it is preferable to use the above ( The monomer with more carbon atoms in the hydroxyalkyl group in the meth)acrylate hydroxyalkyl ester is preferably a (methyl hydroxyalkyl group) whose carbon number is 3 or more (for example, 3~12, preferably 4~10). ) hydroxyalkyl acrylates (eg 4-hydroxybutyl acrylate). In an ideal aspect, more than 50% by weight (for example more than 50% by weight, more than 70% by weight or more than 85% by weight) of the monomer (A2) can be 4-hydroxybutyl acrylate. A hydroxyl group-containing monomer can be used individually by 1 type or in combination of 2 or more types.

In some aspects of using a hydroxyl group-containing monomer as the monomer (A2), the above-mentioned hydroxyl group-containing monomer may be one or two or more types selected from compounds having no methacryl group. Suitable examples of the hydroxyl group-containing monomer having no methacryl group include the above-mentioned various hydroxyalkyl acrylates. For example, more than 50% by weight, more than 70% by weight or more than 85% by weight of the hydroxyl-containing monomer used as the monomer (A2) is preferably hydroxyalkyl acrylate. By using hydroxyalkyl acrylate, hydroxyl groups that contribute to providing crosslinking points or imparting moderate aggregation can be introduced into acrylic polymers, and can be obtained more easily than the case of using only the corresponding hydroxyalkyl methacrylate Adhesives with good flexibility or adhesion at room temperature.

Examples of carboxyl group-containing monomers include itaconic acid, maleic acid, fumaric acid, Crotonic acid and isocrotonic acid, etc., but not limited thereto. Examples of carboxyl group-containing monomers that can be suitably used include acrylic acid and methacrylic acid. Moreover, in several aspects, it is preferable to use the compound represented by following formula (1) as a carboxyl group containing monomer from a viewpoint of reducing the elastic modulus of an adhesive agent, for example. CH ₂ =CR ¹ -COO-R ² -OCO-R ³ -COOH (1) Here, R ¹ in the above formula (1) is hydrogen or methyl. R ² and R ³ are divalent linking groups (specifically, organic groups with 1 to 20 carbon atoms (for example, 2 to 10, preferably 2 to 5)), which may be the same as or different from each other. R ² and R ³ in the above formula (1) may be, for example, a divalent aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group. For example, the above R ² and R ³ may be an alkylene group having 2 to 5 carbon atoms. Specific examples of the carboxyl group-containing monomer represented by the above formula (1) include, for example: 2-(meth)acryloxyethyl hexahydrophthalic acid, 2-(meth)acryloxyethyl-phthalein acid, 2-(meth)acryloxyethyl-2-hydroxyethyl-phthalic acid, 2-(meth)acryloxyethyl-succinic acid, 2-(meth)acryloxy Propyl hexahydrogen phthalate, 2-(meth)acryloxypropyl hydrogen phthalate, 2-(meth)acryloxypropyl tetrahydrohydrogen phthalate, and the like. A carboxyl group-containing monomer can be used individually by 1 type or in combination of 2 or more types. A hydroxyl group-containing monomer and a carboxyl group-containing monomer can also be used together.

The content of the monomer (A2) in the monomer component constituting the acrylic polymer is not particularly limited, and can be set according to the purpose. In several aspects, the content of the above-mentioned monomer (A2) may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. From the viewpoint of obtaining a higher use effect, in some aspects, the content of the above-mentioned monomer (A2) is preferably 1% by weight or more, may be 2% by weight or more, or may be 4% by weight above. The upper limit of the content of the monomer (A2) in the monomer component is set so that the total of the content of the monomer (A1) does not exceed 100% by weight. In several aspects, it is appropriate to set the content of the above-mentioned monomer (A2) to be, for example, 30% by weight or less or 25% by weight or less, and it is easy to increase the refractive index by making the content of the monomer (A1) relatively large From this point of view, it is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, may be less than 10% by weight, or may be less than 7% by weight. In several desirable aspects, from the viewpoint of lowering the modulus of elasticity of the adhesive, the content of the above-mentioned monomer (A2) is less than 5% by weight, preferably less than 3% by weight, or less than 1.5% by weight.

The total content of the monomer (A1) and the monomer (A2) in the monomer component constituting the acrylic polymer may be, for example, 31% by weight or more, preferably 51% by weight or more, may be 61% by weight or more, or may be More than 71% by weight. In some aspects, the total content of the monomer (A1) and the monomer (A2) in the monomer components constituting the acrylic polymer may be, for example, 76% by weight or more, preferably 81% by weight or more, may be 86% by weight or more, may be 91% by weight or more, may be 96% by weight or more, may be 99% by weight or more, and may be substantially 100% by weight.

(Single A3) In several desirable aspects, the monomer component constituting the acrylic polymer may further contain an alkyl (meth)acrylate (hereinafter also referred to as "monomer (A3)") in addition to the aforementioned monomer (A1). Monomer (A3) can help reduce the modulus of elasticity of the adhesive. In addition, it can also help to improve the compatibility of additives in the adhesive or adhesive properties such as adhesive force. A monomer (A3) can be used individually by 1 type or in combination of 2 or more types.

The monomer (A3) can be suitably used as an alkyl (meth)acrylate having a straight-chain or branched-chain alkyl group with 1-20 carbon atoms (ie C _1-20 ) at the end of the ester. Specific examples of C _1-20 alkyl (meth)acrylates include: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate , n-butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, pentyl (meth)acrylate, (meth) ) isopentyl acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate , nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, ten (meth)acrylate Diester, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, (meth)acrylate base) octadecyl acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc., but not limited thereto.

In several aspects, at least a part of the monomer (A3) can suitably be a (meth)acrylic acid alkyl having a Tg of a homopolymer of -20°C or lower (preferably -40°C or lower, for example -50°C or lower). base ester. The low Tg alkyl (meth)acrylate can help improve the low elastic modulus of the adhesive. In addition, it can also contribute to the improvement of adhesive properties such as adhesive force. The lower limit of the Tg of the alkyl (meth)acrylate is not particularly limited, and may be, for example, -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the aforementioned low Tg alkyl (meth)acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), heptyl acrylate, octyl acrylate, and isononyl acrylate (iNA). wait. In several other aspects, at least a part of the monomer (A3) may be an alkyl (meth)acrylate whose homopolymer Tg is higher than -20°C (for example, -10°C or higher). The upper limit of Tg of the said alkyl (meth)acrylate is, for example, 10 degreeC or less, may be 5 degreeC or less, and may be 0 degreeC or less. Alkyl (meth)acrylates having a Tg in this range can help adjust the modulus of elasticity of the adhesive. The alkyl (meth)acrylate having the above-mentioned Tg is preferably used together with the above-mentioned low-Tg alkyl (meth)acrylate, but it is not particularly limited. Lauryl acrylate (LA) is mentioned as a specific example of the alkyl (meth)acrylate which has the said Tg.

Among the aspects of using the monomer (A3), it is preferable to use a C _4-8 alkyl (meth)acrylate as the monomer (A3). Among them, C _4-8 alkyl acrylate is preferably used. The _C4-8 alkyl (meth)acrylate can be used individually by 1 type or in combination of 2 or more types. By using C _4-8 alkyl (meth)acrylate, it tends to be easy to lower the modulus of elasticity of the adhesive and obtain good adhesive properties (adhesive force, etc.). In the aspect of using C _4-8 alkyl (meth)acrylate as the monomer (A3), the C _4-8 (meth)acrylic acid in the alkyl (meth)acrylate contained in the monomer component The ratio of the alkyl ester is suitably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, more preferably 90% by weight or more, and may be substantially 100% by weight.

Among the several aspects of using the monomer (A3), C _1-6 alkyl (meth)acrylate can be suitably used as the monomer (A3). By using C _1-6 alkyl (meth)acrylate, the storage modulus of elasticity in each temperature region can be adjusted. For example, setting the storage elastic modulus in the high temperature region to be relatively high can suppress the difference between the storage elastic modulus in the low temperature region and the high temperature region from increasing. In addition, C _1-6 alkyl (meth)acrylate tends to be excellent in copolymerizability with the monomer (A1). C _1-6 alkyl (meth)acrylates can be used alone or in combination of two or more. The C _1-6 alkyl (meth)acrylate is preferably a C _1-6 alkyl acrylate, more preferably a C _2-6 alkyl acrylate, more preferably a C _4-6 alkyl acrylate. In several other aspects, C _1-6 alkyl (meth)acrylate is preferably C _1-4 alkyl (meth)acrylate, more preferably C _2-4 alkyl (meth)acrylate , more preferably C _2-4 alkyl acrylate. A suitable example of C _1-6 alkyl (meth)acrylate includes BA.

In the monomer components constituting the acrylic polymer, the content of the C _1-6 alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. In some aspects, the content of the above-mentioned C _1-6 alkyl (meth)acrylate may be 10% by weight or more, and may be 15% by weight or more from the viewpoint of lowering the modulus of elasticity and adhesive force. , may be 20% by weight or more, or may be 25% by weight or more (for example, 30% by weight or more). The upper limit of the content of C _1-6 alkyl (meth)acrylate in the monomer component is, for example, less than 50% by weight, or less than 35% by weight. In several aspects, from the viewpoint of maintaining a high refractive index, the content of the above-mentioned C _1-6 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, more preferably less than 17% by weight %, may be less than 12% by weight, may be less than 7% by weight, may be less than 3% by weight, or may be less than 1% by weight. The technique disclosed here can be carried out even without substantially using C _1-6 alkyl (meth)acrylate.

Among other several aspects of using the monomer (A3), C _7-12 alkyl (meth)acrylate can be suitably used as the monomer (A3). By using C _7-12 alkyl (meth)acrylate, the storage elastic modulus can be suitably reduced. _C7-12 alkyl (meth)acrylates can be used individually by 1 type or in combination of 2 or more types. The C _7-12 alkyl (meth)acrylate is preferably a C _7-10 alkyl acrylate, more preferably a C _7-9 alkyl acrylate, more preferably a C ₈ alkyl acrylate. Examples of C _7-12 alkyl (meth)acrylates include 2EHA, iNA, and LA, and suitable examples include 2EHA.

In the monomer components constituting the acrylic polymer, the content of the _C7-12 alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. In several aspects, the content of the above-mentioned C _7-12 alkyl (meth)acrylate may be 10% by weight or more, and may be 15% by weight or more from the viewpoint of low elastic modulus and adhesive force. , may be 20% by weight or more, or may be 25% by weight or more (for example, 30% by weight or more). The upper limit of the content of C _7-12 alkyl (meth)acrylate in the monomer component is, for example, less than 50% by weight, or less than 35% by weight. In several aspects, from the viewpoint of maintaining a high refractive index, the content of the above-mentioned C _7-12 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, more preferably less than 17% by weight %, may be less than 12% by weight, may be less than 7% by weight, may be less than 3% by weight, or may be less than 1% by weight. The technique disclosed here can be carried out even without substantially using the C _7-12 alkyl (meth)acrylate.

Among the aspects using the monomer (A3), at least a part of the monomer (A3) is preferably an alkyl acrylate from the viewpoint of lowering the modulus of elasticity. The use of alkyl acrylate is also advantageous in terms of adhesive properties such as adhesive force. For example, more than 50% by weight of the monomer (A3) is preferably an alkyl acrylate, and the ratio of the alkyl acrylate in the monomer (A3) is preferably more than 75% by weight, more preferably more than 90% by weight. (A3) may be substantially 100 weight% of an alkyl acrylate. An aspect in which only one or more alkyl acrylates are used as the monomer (A3) and no alkyl methacrylates are used may also be used.

In the aspect in which the monomer component contains the monomer (A3) (alkyl (meth)acrylate), the content of the alkyl (meth)acrylate in the monomer component can be set so that the use effect can be exhibited suitably. In several aspects, the content of the above-mentioned alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. The upper limit of the content of the monomer (A3) in the monomer component is set so that the sum of the content of the monomers (A1) and (A2) does not exceed 100% by weight, for example, less than 50% by weight, or less than 35% by weight. In several aspects, the content of the above-mentioned monomer (A3) may be, for example, 24% by weight or less. Generally speaking, the refractive index of alkyl (meth)acrylate is low, so in order to increase the refractive index, the content of monomer (A3) in the monomer component is limited, so that the content of monomer (A1) is relatively large is advantageous. From the above point of view, the content of the monomer (A3) is suitable to be less than 23% by weight of the monomer components, preferably less than 20% by weight, more preferably less than 17% by weight, may be less than 12% by weight, may be less than 7% by weight , may be less than 3% by weight, or less than 1% by weight. The technique disclosed here can be implemented suitably also in the aspect which does not use a monomer (A3) substantially.

(other monomers) The monomer component constituting the acrylic polymer may optionally contain monomers other than the aforementioned monomers (A1), (A2), and (A3) (hereinafter referred to as "other monomers"). The above-mentioned other monomers can be used, for example, to adjust Tg of the acrylic polymer, adjust adhesive performance, improve compatibility in the adhesive layer, and the like. These other monomers may be used alone or in combination of two or more.

Examples of the above-mentioned other monomers include monomers having functional groups other than hydroxyl groups and carboxyl groups (functional group-containing monomers). For example, other monomers that can improve the cohesive force or heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, and the like. In addition, examples of monomers that can introduce functional groups that can serve as crosslinking sites into acrylic polymers, or that can contribute to improving the adhesion with an adherend or improve compatibility in adhesives include: Amide-containing monomers (such as (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amine-containing monomers (such as aminoethyl (meth)acrylate, N, N-dimethylaminoethyl (meth)acrylate, etc.), monomers with nitrogen atom rings (such as N-vinyl-2-pyrrolidone, N-(meth)acryloylmoephrine etc.), imide-containing monomers, epoxy-containing monomers, ketone-containing monomers, isocyanate-containing monomers, alkoxysilyl-containing monomers, etc. In addition, monomers having nitrogen atom rings, such as N-vinyl-2-pyrrolidone, also correspond to amide group-containing monomers. The same applies to the relationship between the above-mentioned monomer having a nitrogen atom-containing ring and the amino group-containing monomer.

Other monomers that can be used other than the above-mentioned functional group-containing monomers include: vinyl ester-based monomers such as vinyl acetate; cyclohexyl (meth)acrylate, isocamphoryl (meth)acrylate, etc. (Meth)acrylate; Olefin-based monomers such as ethylene, butadiene, and isobutylene; Chlorine-containing monomers such as vinyl chloride; Methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylic acid Alkoxy-containing monomers such as esters, ethoxyethoxyethyl (meth)acrylate, etc.; vinyl ether-based monomers such as methyl vinyl ether, etc. A suitable example of other monomers that can be used for the purpose of improving the flexibility of the adhesive is ethoxyethoxyethyl acrylate (alias: ethyl carbitol acrylate, Tg of homopolymer:- 67°C).

When using the above-mentioned other monomers, the usage amount is not particularly limited, and can be appropriately set within the range where the total amount of the monomer components does not exceed 100% by weight. From the viewpoint of making it easier to exhibit the effect of increasing the refractive index obtained by using the monomer (A1), the content of the above-mentioned other monomers in the monomer component can be set to, for example, about 35% by weight or less, or about 25% by weight or less (for example, 0~25% by weight) is appropriate, but about 20% by weight or less (for example, 0~20% by weight), it is advantageous to set it as about 10% by weight or less (for example, 0~10% by weight), preferably about 5% by weight Below, for example, about 1% by weight or less. The technique disclosed here can be preferably carried out in a state where the monomer component does not substantially contain the above-mentioned other monomers.

In several aspects, the monomer component constituting the acrylic polymer may be a composition in which the amount of the methacryl group-containing monomer used is suppressed to a predetermined value or less. The amount of the methacryl group-containing monomer in the monomer component may be less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. Limiting the usage amount of the methacryl group-containing monomer as mentioned above is advantageous from the viewpoint of achieving a balance between flexibility and adhesiveness and a high refractive index of the adhesive. The monomer component constituting the acrylic polymer may also be a composition that does not contain a methacryl group-containing monomer (for example, a composition composed only of an acryl group-containing monomer).

In several aspects, the usage amount of the carboxyl group-containing monomer in the monomer components constituting the acrylic polymer is limited from the viewpoint of suppressing coloring or discoloration (eg, yellowing) of the adhesive. The usage amount of the carboxyl group-containing monomer in the monomer component may be less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, or less than 0.05% by weight. If the amount of the carboxyl group-containing monomer used is limited, the corrosion of metal materials (such as metal wiring or metal films that may exist on the adherend) that can be contacted or disposed adjacent to the adhesive disclosed herein can be suppressed. It is also beneficial from this point of view. The technique disclosed here can be carried out in a state where the monomer component constituting the acrylic polymer does not contain a carboxyl group-containing monomer. For the same reason, in several aspects, the amount of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc. in addition to carboxyl groups) in the monomer components constituting the acrylic polymer should be limited. The usage amount of the acidic functional group-containing monomer in the monomer component of the above-mentioned aspect can be applied to the ideal usage amount of the above-mentioned carboxyl group-containing monomer. The technique disclosed here can be suitably implemented in a state in which the above-mentioned monomer components do not contain an acidic group-containing monomer (that is, in a state in which the acrylic polymer is acid-free).

(Glass transition temperature Tg _T ) The monomer components constituting the acrylic polymer preferably have a composition in which the glass transition temperature Tg _T of the monomer components is approximately 15°C or lower. In several aspects, the glass transition temperature Tg _T is preferably below 10°C, more preferably below 5°C, more preferably below 1°C, and may also be below 0°C. In several other aspects, the glass transition temperature Tg _T may be lower than -10°C, lower than -20°C, lower than -25°C, lower than -30°C, or lower than -35°C. From the viewpoint of reducing the modulus of elasticity of the adhesive, it is advantageous to have a low glass transition temperature Tg _T. In addition, the glass transition temperature Tg _T may be, for example, -60°C or higher, but from the viewpoint of facilitating the high refractive index of the adhesive, it is preferably -50°C or higher, more preferably higher than -45°C, or higher than -45°C. -40°C. In several ideal aspects, the above-mentioned glass transition temperature Tg _T may be higher than -30°C, higher than -20°C, higher than -10°C, or higher than -5°C. An adhesive having both a high refractive index and a low modulus of elasticity can be suitably formed by using an acrylic polymer having a glass transition temperature Tg _T in the above-mentioned range.

Here, the glass transition temperature Tg _T means the glass transition temperature obtained by Fox's formula from the composition of the above-mentioned monomer components unless otherwise specified. Fox's formula, as shown below, is a relationship between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing the monomers constituting the copolymer. 1/Tg=Σ(Wi/Tgi) In the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), and Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight ), Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i. As for the glass transition temperature of the homopolymer used in the calculation of Tg, values described in known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) are used. The highest value is adopted for the individual of plural values described in the above-mentioned Polymer Handbook. When the Tg of the homopolymer is not described in the known materials, the value obtained by the measuring method described in JP-A-2007-51271 is used.

(Preparation method of acrylic polymer) In the technique disclosed here, the method for obtaining the acrylic polymer composed of the above-mentioned monomer components is not particularly limited, and solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method can be suitably used Various polymerization methods known as synthesis methods of acrylic polymers, such as methods. For example, a solution polymerization method can be suitably used. The polymerization temperature during solution polymerization can be appropriately selected according to the type of monomers and solvents used, the type of polymerization initiator, etc., for example, it can be set at about 20°C~170°C (typically about 40°C~140°C).

The solvent used for the solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixture of two or more solvents selected from the following can be used: aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; hexane or cyclic Aliphatic or alicyclic hydrocarbons such as hexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (such as monohydric alcohols with 1 to 4 carbon atoms); tertiary butylmethyl Ethers such as ether; ketones such as methyl ethyl ketone, etc.

The initiator used for the polymerization can be appropriately selected from known polymerization initiators according to the type of polymerization method. For example, 1 type or 2 or more types of azo-type polymerization initiators, such as 2,2'- azobisisobutyronitrile (AIBN), can be used suitably. Other examples of the polymerization initiator include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; Aromatic carbonyl compounds, etc. Still another example of the polymerization initiator includes a redox initiator in which a peroxide and a reducing agent are combined. A polymerization initiator can be used individually by 1 type or in combination of 2 or more types. The usage-amount of a polymerization initiator should just be a usual usage amount, For example, it can select from the range of about 0.005-1 weight part (typically about 0.01-1 weight part) with respect to 100 weight part of monomer components.

In the above-mentioned polymerization, various conventionally known chain transfer agents can be used as needed. For example, mercaptans such as n-dodecylmercaptan, tertiary dodecylmercaptan, hydrothioacetic acid, and α-thioglycerol can be used. Alternatively, chain transfer agents containing no sulfur atoms (non-sulfur-based chain transfer agents) can also be used. Examples of non-sulfur-based chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methylbenzene Styrenes such as ethylene, α-methylstyrene dimer, etc. A chain transfer agent can be used individually by 1 type or in combination of 2 or more types. When using a chain transfer agent, the usage-amount can be about 0.01-1 weight part with respect to 100 weight part of monomer components, for example.

The weight average molecular weight (Mw) of the above-mentioned acrylic polymer is not particularly limited, for example, it is about 30×10 ⁴ or more, preferably about 50×10 ⁴ or more, about 70×10 ⁴ or more, or about 80 ×10 ⁴ or more. By using the acrylic polymer whose Mw is more than a predetermined value, it becomes easy to obtain the moderate cohesive force which can exhibit the desired adhesive characteristic. Moreover, additives, such as a plasticizer, can be contained more, and it exists in the tendency which becomes easy to realize a desired elastic modulus. Also, the upper limit of the Mw of the acrylic polymer is, for example, about 500×10 ⁴ or less, and from the viewpoint of adhesive performance, it is preferably about 400×10 ⁴ or less (preferably about 150×10 ⁴ or less, for example, about 130 ×10 ⁴ or less).

Here, the Mw of the acrylic polymer can be obtained by converting it into polystyrene by gel permeation chromatography (GPC). Specifically, it can be obtained by using the product name "HLC-8220GPC" (manufactured by Tosoh Co., Ltd.) as a GPC measuring device, and measuring under the following conditions. [Measurement conditions of GPC] Sample concentration: 0.2% by weight (tetrahydrofuran solution) Sample injection volume: 10µL Eluent: Tetrahydrofuran (THF) Flow rate (flow rate): 0.6mL/min Column temperature (measurement temperature): 40°C String: Sample column: 1 piece of product name "TSKguardcolumn SuperHZ-H" + 2 pieces of product name "TSKgel SuperHZM-H" (manufactured by Tosoh Corporation) Reference column: 1 piece of product name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation) Detector: Differential Refractometer (RI) Standard sample: polystyrene

(Plasticizer) The adhesive composition disclosed herein is characterized by containing a plasticizer in addition to the acrylic polymer. By using a plasticizer, the modulus of elasticity of the adhesive can be reduced. In addition, in the form of an adhesive sheet, flexibility or compliance to deformation can be improved. As the plasticizer disclosed here, a cyclic unsaturated organic compound having two or more double bond-containing rings can be used. In other words, the plasticizer is a compound having two or more double bond-containing rings in one molecule. Therefore, the plasticizer has at least a first double bond-containing ring and a second double bond-containing ring. By having two or more double bond-containing rings, it is possible to contribute to lowering the modulus of elasticity of the adhesive without impairing the refractive index of the adhesive or maintaining the refractive index. From the viewpoint of exhibiting the plasticizing effect, the number of double bond-containing rings contained in the plasticizer is preferably 6 or less, may be 4 or less, and may be 3 or less. A plasticizer can be used individually by 1 type or in combination of 2 or more types.

Also, the plasticizer used in the technique disclosed here is a compound that is liquid at 30°C. In addition, in this specification, "liquid state" means fluidity, and means liquid in terms of the state of matter. The compounds include those having a melting point below 30°C. The above-mentioned plasticizer is in a liquid state at 30° C., so that the plasticizing effect can be properly exerted, and the low elastic modulus of the adhesive can be effectively realized. The above-mentioned plasticizer is preferably a compound that is liquid at 25°C, more preferably a compound that is liquid at 20°C. By using a compound having two or more double bond-containing rings and being liquid at 30° C. as the plasticizer, an adhesive having both a high refractive index and a low modulus of elasticity can be formed.

The double bond-containing ring contained in the plasticizer disclosed here may be either a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. The plasticizer may have at least one ring selected from an aromatic ring and a heterocycle (heterocycle) as a double bond-containing ring. In addition, the above-mentioned heterocyclic ring may have a structure included in an aromatic ring, or may have a heterocyclic structure having a double bond different from the aromatic ring. The double bond-containing ring (typically an aromatic ring) that the plasticizer can have can be a benzene ring (it can be a benzene ring that constitutes a part of a biphenyl structure or a fennel structure); a naphthalene ring, an indene ring, an azulene ring, an anthracene ring , condensed ring of phenanthrene ring and other carbocyclic rings; it can also be pyridine ring, pyrimidine ring, pyridine ring, pyrrole ring, tri-pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, Heterocycles such as isoxazole ring, thiazole ring, and thiophene ring. The heteroatoms contained as ring constituting atoms in the heterocyclic ring may be, for example, one or two or more kinds selected from the group consisting of nitrogen, sulfur and oxygen. In several aspects, the above-mentioned heteroatoms constituting the heterocycle may be one or both of nitrogen and sulfur. The plasticizer may have, for example, a structure in which one or more carbocyclic rings and one or more heterocyclic rings are condensed, like the dinaphthothiophene structure.

The aforementioned double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have 1, 2 or more substituents on ring constituting atoms, or may have no substituents. When there is a substituent, the substituent can be exemplified by an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyl group Oxygen, etc., but not limited thereto. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1-4, more preferably 1-3, and may be 1 or 2, for example. In several aspects, the above-mentioned double bond-containing ring may be an aromatic ring having no substituents on the ring constituting atoms, or may have an aromatic ring selected from the group consisting of alkyl, alkoxy, and ethylenic groups on the ring constituting atoms. An aromatic ring with 1 or more substituents in the group consisting of an unsaturated group (such as (meth)acryloyloxy group), hydroxyl group and hydroxyalkyl group. As a substituent, an alkyl group, an alkoxy group, and a hydroxyalkyl group can be used suitably.

In several aspects, compounds without ethylenically unsaturated groups may be suitably used as plasticizers. Thereby, deterioration of the adhesive composition due to heat or light (progress of gelation or decrease in leveling property due to increase in viscosity) can be suppressed, and storage stability can be improved. The use of a plasticizer without an ethylenically unsaturated group is to suppress the change in elastic modulus, dimensional change or It is also preferable from the viewpoint of deformation (warping, undulation, etc.), occurrence of optical strain, and the like.

As the plasticizer, a high-refractive-index plasticizer with a refractive index of about 1.50 or higher can be suitably used. By using a high refractive index plasticizer, a higher level of high refractive index and low elastic modulus can be achieved. From the point of view of maintaining and increasing the refractive index of the adhesive while reducing the elastic modulus, the refractive index of the plasticizer is preferably about 1.51 or more, more preferably about 1.53 or more, and more preferably about 1.55 or more. About 1.56 or more, about 1.58 or more, about 1.60 or more, or about 1.62 or more. In several aspects, from the viewpoint of the ease of preparation of the adhesive composition and the compatibility in the adhesive, the refractive index of the plasticizer is suitable to be 2.50 or less, and is advantageous to be 2.00 or less. It may be 1.90 or less, may be 1.80 or less, and may be 1.70 or less. In addition, the refractive index of the plasticizer was measured on conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C. using an Abbe refractometer similarly to the refractive index of a monomer. When there is a nominal value of the refractive index at 25° C. provided from a manufacturer or the like, the nominal value may be adopted.

The molecular weight of the plasticizer is not particularly limited, and one with a molecular weight smaller than the above-mentioned acrylic polymer is usually used. From the viewpoint of easily exhibiting the plasticizing effect, the molecular weight of the plasticizer is suitably below 30,000, advantageously below 25,000, and may be less than 10,000 (for example, less than 5,000), or less than 3,000. In several aspects, the molecular weight of the plasticizer is preferably less than 2000, more preferably less than 1200, more preferably less than 900, less than 600, less than 500, less than 400, less than 300, and It may be 250 or less (for example, 220 or less). The fact that the molecular weight of the plasticizer is not too large is advantageous from the viewpoint of improving the compatibility in the adhesive layer. In addition, from the viewpoint of easily exhibiting a sufficient plasticizing effect, the molecular weight of the plasticizer is preferably 100 or more, preferably 130 or more, more preferably 150 or more, may be 170 or more, may be 200 or more, may be 220 or more, or 250 or more. It is also preferable that the molecular weight of the plasticizer is not too low from the standpoint of heat resistance of the adhesive sheet or suppression of contamination by the adhesive. In some aspects, the molecular weight of the plasticizer is, for example, 300 or more, preferably 315 or more, and may be 350 or more. A plasticizer with a large molecular weight is not easy to vaporize, so by using a plasticizer with a large molecular weight in an adhesive, an adhesive that can exhibit stable characteristics can be easily obtained. Also, a plasticizer with a large molecular weight is less likely to move in the adhesive. Therefore, for example, it is difficult for plasticizers to move to the surface of the adhesive to affect the adhesive properties. The molecular weight of the above-mentioned plasticizer is more preferably 400 or more, more preferably 450 or more, especially 500 or more, and may be 530 or more. In addition, the molecular weight of a plasticizer can use the molecular weight calculated from a chemical structure. When there is a nominal value of molecular weight provided from a manufacturer or the like, this nominal value can be adopted.

In several aspects, the plasticizer can be one or more compounds selected from the following compounds: one having two or more non-condensed double bond-containing rings (typically aromatic rings) bonded via a linking group Compounds with two or more non-condensed double bond-containing rings (typically aromatic rings) chemically bonded directly (that is, without intervening other atoms), compounds with condensed double bond-containing rings (typically aromatic rings) Compounds having an aromatic ring) structure, a compound having a fennel structure, a compound having a dinaphthothiophene structure, a compound having a dibenzothiophene structure, etc., which are liquid at 30°C (eg, 25°C or 20°C).

In the aspect of using a compound having a structure in which two or more non-condensed double bond-containing rings are bonded via a linking group as a plasticizer, the linking group may be, for example, an oxygen group (-O-), a thiooxy group (-S-), oxyalkylene (such as -O-(CH ₂ ) _n -group, where n is 1~3, preferably 1), thiooxyalkylene (such as -S-(CH ₂ ) _n -base, where n is 1~3, preferably 1), straight chain alkylene (ie -(CH ₂ ) _n -base, where n is 1~6, preferably 1~3), The above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group, and the above-mentioned straight-chain alkylene group have been partially or completely halogenated. The above linking group may also have a siloxane bond (-SiOR-) or an ester bond. In the plasticizer, the linking group connecting the first double bond-containing ring (non-condensed ring) and the second double bond-containing ring (non-condensed ring) can also be selected from the same types as above. From the viewpoint of reducing the modulus of elasticity of the adhesive, suitable examples of the linking group include an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. The number of atoms of the above linking group is not particularly limited, for example, it is 1-30, it can be 1-25, it can be 1-20, it is appropriate to be 1-18, it is preferably 1-12, more preferably 1-10, More preferably 1~8, especially preferably 1~5, may be 1~3, may also be 1 or 2. In addition, the number of atoms of the linking group refers to the minimum number of atoms required to reach from one non-condensed double bond-containing ring to another non-condensed double bond-containing ring. For example, when the linking group is composed of a straight-chain alkylene group (ie -(CH ₂ ) _n -group), the number of n becomes the number of atoms in the linking group. For another example, when the linking group is an oxyethylene group (ie -(C ₂ H ₄ O) _n -group), the product of the sum of 2 carbon atoms and 1 oxygen atom constituting the oxyethylene group and the product of n (3n ) becomes the atomic number of the linking group. Preferable examples of the above compounds include compounds having a phenoxybenzyl group. Examples of the above-mentioned compounds include phenoxybenzyl (meth)acrylate (such as m-phenoxybenzyl (meth)acrylate), phenoxybenzyl alcohol, oxybis[(alkoxyalkyl) Benzene] (e.g. 4,4'-oxybis[(methoxymethyl)benzene]) and the like. Other examples of the above compound include silicone-based plasticizers (specifically, silicone compounds) described later.

The compound having a structure in which two or more double bond-containing rings (non-condensed rings) are directly chemically bonded may be, for example, a compound containing a biphenyl structure, a compound containing a triphenyl structure, or the like. Also, examples of the compound having a condensed double bond-containing ring structure include naphthalene ring-containing compounds, anthracene ring-containing compounds, and the like. Specific examples include 1-naphthylethanone and the like. In addition, the above-mentioned compound having a fennel structure is included in the concept of a compound having a structure having two or more double bond-containing rings (non-condensed rings) directly chemically bonded because it contains a structural part in which two benzene rings are directly chemically bonded. The above-mentioned compound having a dinaphthothiophene structure is also included in the concept of the above-mentioned compound having a condensed double bond-containing ring structure because it includes a naphthalene structure and a structure in which a thiophene ring is condensed with two naphthalene structures. The above-mentioned compound having a dibenzothiophene structure is included in the concept of the above-mentioned compound having a condensed double bond-containing ring structure because it has a structure in which a thiophene ring and two benzene rings are condensed.

In several aspects, polysiloxane-based plasticizers can be used as plasticizers. By using polysiloxane-based plasticizers, it is easy to obtain stable plasticizing effect and high adhesive force, so the refractive index, flexibility and adhesive force of the adhesive can be improved in a balanced manner. As the polysiloxane-based plasticizer, a compound having two or more double bond-containing rings and being liquid at 30° C. can be used without particular limitation. The polysiloxane-based plasticizer is specifically a siloxane compound, and the number of Si atoms in the compound is 1 or more (typically 2 or more), and the upper limit is not particularly limited, for example, it may be about 10 or less. In one molecule of the polysiloxane-based plasticizer, the Si atom may or may not be directly bonded to the double bond-containing ring. At least one of the aforementioned Si atoms is preferably directly bonded to at least one double bond-containing ring. The silicone-based plasticizers can be used alone or in combination of two or more.

In several aspects, polysiloxane-based plasticizers can be those that are composed of a siloxane compound with Si atoms of 2 to 5, and at least one of the Si atoms is contained in the Si atom. There are two or more rings containing double bonds on the upper bond. The polysiloxane-based plasticizer composed of a siloxane compound having the above-mentioned structure can exert a plasticizing effect according to the flexibility of the siloxane structure, and by having at least one Si atom number of 2 or more and 5 or less In addition, Si atoms bonded with two or more rings containing double bonds can balance the ease of mixing or compatibility with the plasticized object material and the stability of the above-mentioned plasticized effect (such as storage under humid heat, elasticity, etc.) The rate of rise of the modulus is low). From the viewpoint of chemical stability, the above-mentioned siloxane compound preferably does not have a hydrogen atom bonded to an Si atom. That is, it is preferably a siloxane compound not having an Si-H bond.

When the number of Si atoms in the above-mentioned siloxane compound is 3 or more, the above-mentioned siloxane compound may be chain or cyclic, but from the viewpoint of suppressing volatilization, a chain siloxane compound is preferable. The aforementioned chain siloxane compound having 3 or more Si atoms may be linear or branched, but is preferably linear from the viewpoint of obtaining a higher plasticizing effect. Hereinafter, unless otherwise specified, the siloxane compound having 3 or more Si atoms refers to a chain (typically linear) siloxane compound having 3 or more Si atoms.

Each of the double bond-containing rings of the polysiloxane-based plasticizer may be independently a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. The plasticizer may have at least one ring selected from an aromatic ring and a heterocycle (heterocycle) as a double bond-containing ring. In addition, the above-mentioned heterocyclic ring may have a structure included in an aromatic ring, or may have a heterocyclic structure having a double bond different from the aromatic ring. The double bond-containing ring (typically an aromatic ring) that the plasticizer can have can be a carbon ring such as a benzene ring or a naphthalene ring; it can also be a pyridine ring, an imidazole ring, a triazole ring, a azole ring, a thiazole ring, Heterocycles such as thiophene rings. The heteroatoms contained as ring constituting atoms in the heterocyclic ring may be, for example, one or two or more kinds selected from the group consisting of nitrogen, sulfur and oxygen. In several aspects, the above-mentioned heteroatoms constituting the heterocycle may be one or both of nitrogen and sulfur.

The aforementioned double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have 1, 2 or more substituents on ring constituting atoms, or may have no substituents. When there is a substituent, the substituent can be exemplified by an alkyl group, an alkoxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidoxy group, etc., But not subject to such restrictions. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1-4, more preferably 1-3, and may be 1 or 2, for example. In several aspects, the double bond-containing rings of polysiloxane plasticizers are independently selected from the group consisting of aromatic rings without substituents and aromatic rings with substituents on ring constituting atoms. , the substituent of the aromatic ring with a substituent is selected from the group consisting of alkyl, alkoxy, hydroxyl and hydroxyalkyl (preferably the group consisting of alkyl and alkoxy) or 2 or more. For example, the double bond-containing rings of the polysiloxane-based plasticizer are independently selected from aromatic rings (preferably carbocyclic rings) that have no substituents on ring constituting atoms. In several ideal forms, the double bond-containing rings of the polysiloxane-based plasticizer are all benzene rings.

From the point of view of the ease of exerting the plasticizing effect and inhibiting its stability (for example, inhibiting the increase of the elastic modulus due to the volatilization and dissipation of the plasticizer from the material mixed with the plasticizer), the Si of the above-mentioned siloxane compound The number of atoms is preferably 3 or more. Also, from the viewpoint of compatibility in the adhesive, etc., the number of Si atoms in the siloxane compound is preferably 4 or less, more preferably 3 or less. Among them, a polysiloxane plasticizer having 3 Si atoms in the above-mentioned siloxane compound, that is, a polysiloxane plasticizer composed of a trisiloxane compound is preferable.

The number of double bond-containing rings (such as substituted or unsubstituted benzene rings) of the above-mentioned siloxane compound is at least 2, and the heat resistance due to the plasticizing effect (such as the elastic modulus to the From the standpoint of low rate of increase in preservation), it is preferably 3 or more, more preferably 4 or more, and may be 5 or more. Also, when the number of Si atoms in the siloxane compound is n, the number of double bond-containing rings in the siloxane compound is typically 2n+2 or less, and from the viewpoint of improving the plasticizing effect, it is 2n+1 or less is suitable, preferably 2n or less, may be 2n-1 or less, and may be 2n-2 or less. For example, in the aspect in which the above-mentioned siloxane compound is a trisiloxane compound, the number of double bond-containing rings contained in the trisiloxane compound is typically 8 or less, for example, 2 or more and 7 or more. The following may be 3 or more and 7 or less, and may be 4 or more and 7 or less. Among them, a trisiloxane compound in which the number of double bond-containing rings (for example, unsubstituted benzene rings) is 4 or more and 6 or less (for example, 4 or 5) is preferable.

In several aspects, at least one of the Si atoms (typically Si atoms constituting the siloxane chain) contained in the above-mentioned siloxane compound is Si bonded to two or more rings containing double bonds. atom. From the standpoint of enhancing the stability of the plasticizing effect, the number of Si atoms to which two or more double bond-containing rings are bonded in the siloxane compound may be two or more. In a siloxane compound having 3 or more Si atoms, the number of Si atoms bonded to two or more double bond-containing rings may be 2 or more, or 3 or more. When the number of atoms is n, it may be n or less, n-1 or less, or n-2 or less. In some aspects, from the viewpoint of improving the plasticizing effect, at least one of the Si atoms contained in the above-mentioned siloxane compound (preferably a siloxane compound having 3 or more Si atoms), The number of double bond-containing rings bonded to the Si atom is 1 or 0. For example, it is preferably a linear siloxane compound with Si atoms of 3 or more and 5 or less, and the Si atoms at both ends independently have 2 or 3 (preferably 2) double bond-containing rings, and the two A siloxane compound having a structure in which the Si atoms other than the terminal each independently have a double-bond-containing ring or a double-bond-containing ring.

The above-mentioned siloxane compound may also contain a Si atom bonded to a group other than a double bond-containing ring. Groups other than the above double bond-containing ring include: alkyl, aralkyl, alkoxy, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), fluoroalkyl, hydroxyl, hydroxyalkyl, hydroxyalkane oxy, epoxy, glycidoxy, amine, monoalkylamino, dialkylamino, carboxyl, carboxyalkyl, mercapto, etc., but not limited thereto. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1-8, preferably 1-4, more preferably 1-3, for example, 1 or 2. Groups other than the double bond-containing ring bonded to each Si atom contained in the siloxane compound may be independently selected from the group consisting of the groups exemplified above.

In several aspects, the above-mentioned siloxane compound preferably does not have an ethylenically unsaturated group (including those in which the double bond in the double bond-containing ring is an ethylenic double bond). A polysiloxane plasticizer composed of a siloxane compound without an ethylenically unsaturated group is advantageous from the viewpoint of the stability of the plasticizing effect brought by the plasticizer, and has From the point of view of the storage stability of the adhesive sheet of the adhesive layer of the silicone plasticizer, or to suppress the change of the elastic modulus, dimensional change or deformation (warping, undulation, etc.) caused by the reaction of the ethylenically unsaturated group, It is also preferable from the viewpoint of occurrence of optical strain.

Among the several aspects of the polysiloxane-based plasticizer disclosed here, from the viewpoint of improving the plasticizing effect, at least one of the Si atoms contained in the above-mentioned siloxane compound (the number of Si atoms is 3 Among the above siloxane compounds, at least 2) preferably have at least 1 methyl group on the Si atom. For example, Si atoms located at both ends of the siloxane chain preferably independently have one or two (preferably one) methyl groups. In several ideal aspects, the Si atoms contained in the above-mentioned siloxane compound each independently have one or two methyl groups. According to the polysiloxane-based plasticizer composed of the siloxane compound of the above-mentioned structure, it is possible to balance the plasticizing effect brought by the flexibility of the siloxane structure and the bond with at least one Si atom. The stability of the above-mentioned plasticizing effect brought about by the structure with two or more rings containing double bonds.

In several aspects, when the number of Si atoms contained in the above-mentioned siloxane compound is n, the value obtained by summing the number of substituents bonded to the Si atoms (hereinafter also referred to as the total number of substituents) is typical. above is 2n+2, and at least two of them are rings containing double bonds. In several aspects, the ratio SR of the number of rings containing double bonds (preferably aromatic carbocycles, such as benzene rings) in the total number of substituents of polysiloxane-based plasticizers is at least 16%. 20% or more, or 25% or more. When the above-mentioned ratio SR becomes higher, the heat resistance of the silicone-based plasticizer and the stability of the plasticizing effect by the silicone-based plasticizer tend to generally increase. In several aspects, the ratio SR is advantageously 33% or more, preferably 40% or more, more preferably 50% or more (for example, 60% or more), may be 65% or more, and may be 75% or more. The above-mentioned ratio SR may be 100%, but from the viewpoint of ease of blending or compatibility, it is advantageous to be 85% or less, preferably 80% or less, may be 75% or less, may be 65% or less, or may be 60% or less (for example, 50% or less).

Among several aspects, from the viewpoint of the stability of the plasticizing effect, the molecular weight of the polysiloxane-based plasticizer (specifically, a silicone compound) is preferably 400 or more, and 430 or more is advantageous. It is preferably more than 460, may be more than 490, or may be more than 520. In addition, from the viewpoint of plasticizing effect, ease of blending, compatibility, etc., the molecular weight of the above-mentioned siloxane compound is suitably 900 or less, advantageously 850 or less, preferably 700 or less, and more preferably 650 or less. , can be less than 600, can be less than 560, can be less than 540, can also be less than 500.

The molecular weight of the above-mentioned siloxane compound can be a molecular weight calculated from the chemical structure, or a measured value obtained by using matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS). When there is a nominal value of molecular weight provided from a manufacturer or the like, this nominal value can be adopted.

The refractive index of the polysiloxane-based plasticizer disclosed here is not particularly limited, and may be within a range of about 1.30-1.80, for example. From the viewpoint of suppressing the decrease in the refractive index of the material (such as an adhesive) in which the plasticizer is mixed and at the same time achieving a low modulus of elasticity, the polysiloxane-based plasticizer in several aspects has a refractive index of 1.45 or more is appropriate, preferably 1.50 or higher, more preferably 1.52 or higher (for example, 1.53 or higher or 1.54 or higher), and more preferably 1.55 or higher (for example, 1.56 or higher or 1.57 or higher). In addition, the refractive index of the polysiloxane-based plasticizer may be, for example, 1.70 or less, 1.65 or less, or 1.60 or less from the viewpoint of ease of blending or compatibility.

In several aspects, the plasticizer can use the ethylene glycol type compound which has 2 or more double bond containing rings in 1 molecule. The number of oxyethylene units (ie -(C ₂ H ₄ O)- units) contained in the above-mentioned ethylene glycol compound is, for example, 1-10, 1-6, or 2-4. The above-mentioned ethylene glycol-based compound may be a compound having the following structure: two or more non-condensed double bond-containing rings interspersed with oxyethylene units (for example, 1 to 10, ideally 1 to 6, typically 1 to 6) as linking groups 2~4 oxyethylenyl units) bonded. This compound may have 1 or 2 or more ester groups. Examples of the above-mentioned ethylene glycol-based compound include compounds having a structure in which two or more benzoic acids are linked to ethylene glycol, diethylene glycol, triethylene glycol, or polyethylene glycol via ester bonds.

In addition, the technology disclosed here can be implemented without using the above-mentioned ethylene glycol-based compound as a plasticizer or limiting the usage amount thereof. For example, in the plasticizer contained in the adhesive composition, the content ratio of the above-mentioned ethylene glycol-based compound can be made to be less than 90% by weight. The content ratio of the above-mentioned ethylene glycol-based compound in the above-mentioned plasticizer may be less than 50% by weight, may be less than 10% by weight, may be less than 3% by weight, or may be less than 1% by weight, and the adhesive composition may be substantially free of The above-mentioned ethylene glycol-based compound serves as a plasticizer. Similarly, in the adhesive composition, the amount of the above-mentioned ethylene glycol compound relative to 100 parts by weight of the acrylic polymer may be less than 0.5 parts by weight, or less than 0.1 parts by weight.

In several other aspects, liquid rosins such as liquid rosin esters can be used as plasticizers. The aforementioned liquid rosins (for example, liquid rosin esters) may correspond to the aforementioned compounds having a condensed double bond-containing ring structure.

The amount of plasticizer used is not particularly limited and can be set according to the purpose. From the viewpoint of reducing the modulus of elasticity of the adhesive, the amount of the plasticizer used may be, for example, 1 part by weight or more, or 10 parts by weight or more relative to 100 parts by weight of the acrylic polymer. In several ideal forms, the amount of plasticizer relative to 100 parts by weight of the acrylic polymer is greater than 15 parts by weight, can be more than 20 parts by weight, can be more than 30 parts by weight (for example, greater than 30 parts by weight), relatively It is preferably at least 40 parts by weight, more preferably at least 50 parts by weight, especially preferably at least 60 parts by weight, may be at least 75 parts by weight, and may be at least 90 parts by weight. For example, when using the above-mentioned ethylene glycol-based compound as a plasticizer, it is preferable to use more than 30 parts by weight (for example, 40 parts by weight or more, more preferably 50 parts by weight or more) with respect to 100 parts by weight of the acrylic polymer. Also, from the standpoint of achieving a balance between high refractive index and low elastic modulus of the adhesive, it is appropriate to set the amount of the plasticizer to about 200 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. It may be 150 parts by weight or less, preferably 120 parts by weight or less, may be 100 parts by weight or less, may be 80 parts by weight or less, and may be 70 parts by weight or less. In several aspects in which more emphasis is placed on adhesive properties, the amount of the plasticizer used may be 45 parts by weight or less, or 35 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.

(Additive (H _RO )) In the adhesive composition disclosed herein, an organic material with a higher refractive index than the above-mentioned acrylic polymer may be contained as an additive that can be used as desired. Hereinafter, the organic material may be described as "additive (H _RO )". Here, the above-mentioned “H _RO ” means an organic material with a high refractive index (High Refractive index). By combining additives (H _RO ) and acrylic polymers, it is possible to achieve an adhesive that can better balance the refractive index and adhesive properties (peel strength, flexibility, etc.). Organic materials that can be used as additives (H _RO ) can be polymeric or non-polymeric. Moreover, it may have a polymerizable functional group, and may not have a polymerizable functional group. In addition, in this specification, an additive (H _RO ) is defined as a compound different from the compound that can be used as the above-mentioned plasticizer. Therefore, the additive (H _RO ) is specifically not in a liquid state (liquid) at 30°C (for example, 25°C or 20°C). The additive (H _RO ) can be used alone or in combination of two or more.

Since the refractive index of the additive (H _RO ) can be set in an appropriate range in relation to the refractive index of the acrylic polymer, it is not limited to a specific range. The refractive index of the additive (H _RO ) is, for example, greater than 1.55, greater than 1.56 or greater than 1.57, and can be selected from a range higher than that of the acrylic polymer. From the viewpoint of increasing the refractive index of the adhesive, in several aspects, the refractive index of the additive (H _RO ) is advantageously 1.58 or higher, preferably 1.60 or higher, more preferably 1.63 or higher, and may be 1.65 or higher , can be more than 1.70, and can also be more than 1.75. With a higher refractive index additive (H _RO ), the target refractive index can be achieved even with a smaller amount of additive (H _RO ). This is preferable from the viewpoint of suppressing reduction in adhesive properties or optical properties. The upper limit of the refractive index of the additive (H _RO ) is not particularly limited, but it is, for example, 3.000 or less from the viewpoint of compatibility in the adhesive, high refractive index and flexibility suitable for the adhesive, etc. It may be 2.500 or less, 2.000 or less, 1.950 or less, 1.900 or less, or 1.850 or less. In addition, the refractive index of the additive (H _RO ) was measured under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C. using an Abbe refractometer in the same manner as the refractive index of the monomer. When there is a nominal value of the refractive index at 25° C. provided from a manufacturer or the like, the nominal value may be adopted.

The difference between the refractive index n _b of the additive (H _RO ) and the refractive index n _a of the acrylic polymer, that is, n _b −n _a (hereinafter also referred to as “Δn _A ”) is set to be greater than zero. In several aspects, Δn _A is, for example, 0.02 or more, may be 0.05 or more, may be 0.07 or more, may be 0.10 or more, may be 0.15 or more, may be 0.20 or more, or may be 0.25 or more. By selecting the acrylic polymer and the additive (H _RO ) so as to increase Δn _A , the effect of increasing the refractive index using the additive (H _RO ) tends to increase. Also, from the viewpoint of the compatibility of the additive (H _RO ) in the adhesive, in some aspects, Δn _A may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less. or less than 0.35.

In several aspects, the difference between the refractive index n _b of the additive (H _RO ) and the refractive index n _T of the adhesive containing the additive (H _RO ), that is, n _b -n _T (hereinafter also referred to as "Δn _B ”) is set to be greater than 0. In some aspects, Δn _B is, for example, 0.02 or more, may be 0.05 or more, may be 0.07 or more, may be 0.10 or more, may be 0.15 or more, may be 0.20 or more, or may be 0.25 or more. By selecting the composition of the adhesive and the additive (H _RO ) so as to increase Δn _B , the effect of increasing the refractive index by using the additive (H _RO ) tends to increase. In some aspects, Δn _B may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 from the viewpoint of compatibility in the adhesive or the transparency of the adhesive. below or below 0.35.

The molecular weight of the organic material used as the additive (H _RO ) is not particularly limited and can be selected according to the purpose. From the point of view of balancing the effect of high refractive index and other properties (such as optical properties such as flexibility and haze suitable for adhesives), in several aspects, the molecular weight of the additive (H _RO ) is about less than 10000 is appropriate, preferably less than 5000, more preferably less than 3000 (eg less than 1000), may be less than 800, may be less than 600, may be less than 500, may also be less than 400. It is advantageous from the viewpoint of improving the compatibility in the adhesive that the molecular weight of the additive (H _RO ) is not too large. In addition, the molecular weight of the additive (H _RO ) may be, for example, 130 or more, or may be 150 or more. In some aspects, from the viewpoint of increasing the refractive index of the additive (H _RO ), the molecular weight of the additive (H _RO ) is preferably 170 or more, more preferably 200 or more, may be 230 or more, and may be 250 It may be more than 270, it may be more than 500, it may be more than 1000, and it may be more than 2000. In several aspects, a polymer having a molecular weight of about 1000 to 10000 (for example, more than 1000 and less than 5000) can be used as an additive (H _RO ). The molecular weight of the additive (H _RO ) can be calculated based on the molecular weight of a polymer with a non-polymer or a low degree of polymerization (for example, about 2~5 polymers), or by matrix-assisted laser desorption free time-of-flight mass analysis The measured value obtained by MALDI-TOF-MS. When the additive (H _RO ) is a polymer with a higher degree of polymerization, the weight average molecular weight (Mw) according to GPC performed under appropriate conditions can be used. When there is a nominal value of molecular weight provided from a manufacturer or the like, this nominal value can be adopted.

Examples of organic materials that can be an option for additives (H _RO ) include organic compounds with aromatic rings, organic compounds with heterocycles (either aromatic or non-aromatic heterocycles), but are not subject to this and so on.

The aromatic ring of the above-mentioned organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") that can be used as an additive (H _RO ) can be derived from the aromatic ring of a compound that can be used as a monomer (A1). Ring the same thing to choose.

The above-mentioned aromatic ring may have one, two or more substituents, or no substituents on ring constituting atoms. When there is a substituent, the substituent can be exemplified by an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyl group Oxygen, etc., but not limited thereto. In the substituting group comprising carbon atoms, the number of carbon atoms contained in the substituting group is, for example, 1 to 10, 1 to 6 is advantageous, preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. In several aspects, the above-mentioned aromatic ring may be an aromatic ring having no substituent on the ring constituting atom, or may have an aromatic ring selected from an alkyl group, an alkoxy group, and a halogen atom (such as bromine) on the ring constituting atom. Atom) aromatic ring with 1 or more substituents in the group.

Examples of aromatic ring-containing compounds that can be used as additives (H _RO ) include, for example: compounds that can be used as monomers (A1); oligomers that include compounds that can be used as monomers (A1) as monomer units; A group having an ethylenically unsaturated group (which may be a substituent bonded to a ring constituting atom) or a part constituting an ethylenically unsaturated group in the group is removed from a compound usable as a monomer (A1), and The structure of a group substituted with a hydrogen atom or an ethylenically unsaturated group (such as a hydroxyl group, an amino group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidoxy group, etc.) Compounds, etc., which may not correspond to the plasticizers disclosed here, but are not limited thereto.

Among several aspects, organic compounds having two or more aromatic rings in one molecule (hereinafter also referred to as "compounds containing multiple aromatic rings") can be suitably used because it is easy to obtain a higher effect of increasing the refractive index. As an additive (H _RO ). A compound containing a plurality of aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. In addition, the compound containing a plurality of aromatic rings may be a polymer or a non-polymer. Also, the above-mentioned polymer may be an oligomer comprising a monomer containing multiple aromatic rings as a monomer unit (preferably an oligomer with a molecular weight of about 5000 or less, preferably about 1000 or less; for example, a 2-5 polymer left and right low polymers). The above oligomers can be, for example: homopolymers of monomers containing multiple aromatic rings; copolymers of two or more monomers containing multiple aromatic rings; one or more monomers containing multiple aromatic rings Copolymers with other monomers, etc. The aforementioned other monomers may be aromatic ring-containing monomers other than monomers containing a plurality of aromatic rings, monomers without aromatic rings, or a combination thereof.

Non-limiting examples of compounds containing a plurality of aromatic rings include: compounds having a structure in which two or more non-condensed aromatic rings are bonded via a linking group; ) chemically bonded structure, compound with condensed aromatic ring structure, compound with fennel structure, compound with dinaphthothiophene structure, compound with dibenzothiophene structure, etc. Compounds containing a plurality of aromatic rings can be used alone or in combination of two or more.

Examples of an organic compound having a heterocycle (hereinafter also referred to as a heterocycle-containing organic compound) that can be used as an option for the additive (H _RO ) include thioepoxide compounds, compounds having a three-ring ring, and the like. Examples of thioepoxides include bis(2,3-epithiopropyl)disulfide and its polymer (refractive index: 1.74) described in Japanese Patent No. 3712653. Examples of the compound having a three-ring include a compound having at least one (for example, 3 to 40, preferably 5 to 20)) three-ring in one molecule. In addition, the three rings are aromatic, so compounds with three rings are also included in the above-mentioned concept of aromatic ring-containing compounds, and compounds with multiple three rings are also included in the above-mentioned compounds containing multiple aromatic rings in the concept.

In several aspects, it may be convenient to use a compound without ethylenically unsaturated groups as the additive (H _RO ). Thereby, deterioration of the adhesive composition due to heat or light (progress of gelation or decrease in leveling property due to increase in viscosity) can be suppressed, and storage stability can be improved. The use of an additive (H _RO ) that does not have an ethylenically unsaturated group is to suppress dimensional change or deformation due to the reaction of the ethylenically unsaturated group in an adhesive sheet having an adhesive layer containing the additive (H _RO ) ( It is also preferable from the viewpoint of warpage, undulation, etc.), occurrence of optical strain, etc.

In the aspect where an oligomer is used as the additive (H _RO ), the oligomer can be obtained by polymerizing the corresponding monomer component by a known method. When the above-mentioned oligomer is produced by radical polymerization, a polymerization initiator, a chain transfer agent, an emulsifier, etc. which can be used for radical polymerization are appropriately added to the above-mentioned monomer components, and the polymerization is carried out. The above-mentioned polymerization initiators, chain transfer agents, emulsifiers and the like that can be used for radical polymerization are not particularly limited, and can be appropriately selected and used. In addition, the weight-average molecular weight of the oligomer can be controlled by the usage amount of the polymerization initiator and the chain transfer agent, and the reaction conditions, and the usage amount can be appropriately adjusted according to the types of these. The chain transfer agent mentioned above can be, for example, lauryl mercaptan, epoxypropyl mercaptan, thioglycolic acid, 2-mercaptoethanol, α-thioglycerol, hydrogen thioacetic acid, 2-ethylhexyl hydrogen thioacetate, 2,3- Dimercapto-1-propanol, etc. A chain transfer agent may be used individually by 1 type, and may mix and use 2 or more types. The usage-amount of a chain transfer agent can be set so that the oligomer of desired weight average molecular weight can be obtained according to the composition of the monomer component which can be used for the synthesis of an oligomer, the kind of chain transfer agent, etc. In several aspects, it is appropriate to set the amount of the chain transfer agent to about 15 parts by weight or less with respect to 100 parts by weight of the total amount of monomers that can be used in the synthesis of oligomers, and it may be 10 parts by weight or less, or About 5 parts by weight or less may be sufficient. The lower limit of the usage amount of the chain transfer agent is not particularly limited with respect to 100 parts by weight of the total amount of monomers that can be used in the synthesis of oligomers. For example, it may be 0.01 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight. The above may be 1 part by weight or more.

The amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer (the total amount when a plurality of compounds are used) is not particularly limited if it exceeds 0 parts by weight, and can be set according to the purpose. In several aspects, the amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer can be set to, for example, 80 parts by weight or less, so that the high refractive index of the adhesive and the suppression of adhesion properties or optical properties can be balanced. From the viewpoint of property degradation, it is advantageous to set it as 60 parts by weight or less, and it is preferably 45 parts by weight or less. In several aspects where more emphasis is placed on adhesive properties or optical properties, the amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer may be, for example, 30 parts by weight or less, 20 parts by weight or less, or 15 parts by weight. It may be less than or equal to 10 parts by weight. Also, from the viewpoint of increasing the refractive index of the adhesive, the amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer can be, for example, 1 part by weight or more, and it is advantageous to set it as 3 parts by weight or more , should be more than 5 parts by weight, may be more than 7 parts by weight, may be more than 10 parts by weight, may be more than 15 parts by weight, may be more than 20 parts by weight.

(crosslinking agent) The adhesive composition disclosed herein may optionally contain a crosslinking agent in order to adjust the cohesive force of the adhesive or the like. The cross-linking agent can use isocyanate-based cross-linking agent, epoxy-based cross-linking agent, acridine-based cross-linking agent, oxazoline-based cross-linking agent, melamine-based resin, metal chelate-based cross-linking agent, etc. in the field of adhesives A well-known crosslinking agent in China. Among these, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent can be suitably used. As another example of the crosslinking agent, a monomer having two or more ethylenically unsaturated groups in one molecule, that is, a polyfunctional monomer may be mentioned. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based crosslinking agent can use isocyanate compounds with more than two functions, such as: trimethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), Aliphatic polyisocyanates such as dimer acid diisocyanate; cyclopentyl diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane Alicyclic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, stubble diisocyanate (XDI) and other aromatic isocyanates; Modified polyisocyanate modified by ester bond, biuret bond, isocyanurate bond, uretdione bond, urea bond, carbodiimide bond, uretonimine bond, diketone bond, etc. (such as HDI trimeric isocyanate body, HDI alloformate body, etc.), etc. Examples of commercially available products include: trade names TAKENATE 300S, TAKENATE 500, TAKENATE 600, TAKENATE D165N, TAKENATE D178N, TAKENATE D178NL (above, manufactured by Mitsui Chemicals), Sumidur T80, Sumidur L, Desmodur N3400 (above, Sumika Bayer Urethane Co., Ltd.), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX, Coronate 2770 (above, manufactured by Tosoh Corporation), brand name Duranate A201H (above, manufactured by Asahi Kasei Co., Ltd.), etc. An isocyanate compound can be used individually by 1 type or in combination of 2 or more types. A bifunctional isocyanate compound and a trifunctional or higher isocyanate compound may also be used together.

Epoxy-based crosslinking agents include, for example, bisphenol A, epichlorohydrin-type epoxy-based resins, ethylidene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl Ether, Glycerin Triglycidyl Ether, 1,6-Hexanediol Glycidyl Ether, Trimethylolpropane Triglycidyl Ether, Diglycidylaniline, Diaminoglycidylamine, N,N,N',N'-tetraepoxypropyl-stubble diamine and 1,3-bis(N,N-diepoxypropylaminomethyl)cyclohexane, etc. These can be used individually by 1 type or in combination of 2 or more types.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate , Neopentyl Glycol Di(meth)acrylate, Neopentyl Glycol Di(Meth)acrylate, Neopentyl Glycol Tri(Meth)acrylate, DiNeopentyl Glycol Hexa(Meth)acrylate, Ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate base) acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, bisphenol A di(meth)acrylate, Epoxy acrylate, polyester acrylate, urethane acrylate, butyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, etc. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

In several aspects, a bifunctional crosslinking agent having two crosslinking reactive groups (for example, isocyanate groups) per molecule can be used as at least a part of the crosslinking agent. By using a bifunctional cross-linking agent, it is easy to form a flexible cross-linked structure. The bifunctional crosslinking agent can be used individually by 1 type or in combination of 2 or more types. In addition, a bifunctional crosslinking agent may be used in combination with a trifunctional or higher crosslinking agent.

In several aspects, the cross-linking agent may suitably be an acyclic cross-linking agent (also called a chain cross-linking agent) that does not have a ring structure such as an aromatic ring or an aliphatic ring. For example, among the above-mentioned isocyanate-based crosslinking agents, it is preferable to use isocyanate-based compounds that do not have ring structures such as aromatic rings and isocyanurate rings. By using an acyclic isocyanate compound as a crosslinking agent, it is easy to form a highly flexible crosslinking agent. Specific examples of the above-mentioned acyclic isocyanates include: aliphatic isocyanate-based compounds (such as PDI or HDI), or modified products of aliphatic isocyanate-based compounds (such as PDI or HDI via allophanate bonds, biuret bonds, etc.) , urea bond, carbodiimide bond modified polyisocyanate modified body). The acyclic crosslinking agent can be used individually by 1 type or in combination of 2 or more types. In several desirable aspects, acyclic bifunctional crosslinkers can be used as crosslinkers.

In several aspects, a cross-linking agent having a longer distance between one cross-linking reactive group (such as isocyanate group) and the other cross-linking reactive group in one molecule can be used as the cross-linking agent. Thereby, a flexible cross-linked structure having a predetermined length or more can be formed. For example, a compound having 10 or more atoms (for example, 12 or more or 14 or more) constituting a linking chain linking a crosslinking reactive group and other crosslinking reactive groups in one molecule of the crosslinking agent can be used as a crosslinking agent . The upper limit of the number of atoms constituting the linking chain can be adjusted according to the purpose by polymerization or the like, so it is not particularly limited, for example, it can be 2000 or less, it can be 1000 or less, it can be 500 or less, it can be 100 or less, it can be 50 or less, it can be 30 or less, or 20 or less. In addition, the above-mentioned number of atoms constituting the linking chain linking the crosslinking reactive group means that in one molecule of the crosslinking agent, from one crosslinking reactive group to another crosslinking reactive group (when there are 3 or more crosslinking reactive groups) , is the minimum number of atoms required for the cross-linking reactive group closest to the above-mentioned one cross-linking reactive group). The crosslinking agent which has the said linking chain can be used individually by 1 type or in combination of 2 or more types. In several desirable aspects, an acyclic bifunctional crosslinking agent may be used as the above crosslinking agent. Examples of commercially available crosslinking agents include Coronate 2770 (manufactured by Tosoh), TAKENATE D178NL (manufactured by Mitsui Chemicals), and Duranate A201H (manufactured by Asahi Kasei).

The amount used when using a crosslinking agent (which may be a polyfunctional monomer) is not particularly limited, and can be, for example, in the range of about 0.001 to 5.0 parts by weight relative to 100 parts by weight of the above-mentioned monomer components. From the viewpoint of improving the adhesion to the adherend, in several aspects, the amount of the crosslinking agent used is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, relative to 100 parts by weight of the monomer component , may be 1.0 parts by weight or less, may be 0.5 parts by weight or less, and may be 0.2 parts by weight or less. Also, from the viewpoint of appropriately exerting the effect of the crosslinking agent, in several aspects, the amount of the crosslinking agent used relative to 100 parts by weight of the monomer component may be, for example, 0.005 parts by weight or more, and may be 0.01 parts by weight. The above may be 0.05 parts by weight or more, 0.08 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.4 parts by weight or more.

In order to carry out the crosslinking reaction more efficiently, a crosslinking catalyst may also be used. Examples of cross-linking catalysts include metals such as tetra-n-butyl titanate, tetraisopropyl titanate, zirconium tetraacetylacetonate, iron (III) acetylacetonate, butyltin oxide, and dioctyltin dilaurate. Cross-linking catalyst, etc. Among them, tin-based cross-linking catalysts such as dioctyltin dilaurate are preferred. The usage amount of the cross-linking catalyst is not particularly limited. In consideration of the balance between the speed of the cross-linking reaction and the length of service life of the adhesive composition, the amount of the cross-linking catalyst relative to 100 parts by weight of the monomer component can be set at about 0.0001 part by weight or more and less than 1 part by weight. The range is preferably in the range of 0.001 part by weight or more and 0.5 part by weight or less.

The adhesive composition may contain a compound capable of producing keto-enol tautomerism as a cross-linking retarder. Thereby, the effect of prolonging the service life of the adhesive composition can be achieved. For example, a compound capable of producing keto-enol tautomerism can be suitably used in an adhesive composition containing an isocyanate-based crosslinking agent. Various β-dicarbonyl compounds can be used as compounds capable of keto-enol tautomerism. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) or acetylacetate esters (methyl acetylacetate, ethyl acetylacetate, etc.) can be suitably used. Compounds capable of keto-enol tautomerism can be used alone or in combination of two or more. The amount of the compound capable of producing keto-enol tautomerism can be, for example, 0.1 to 20 parts by weight, or 0.5 to 10 parts by weight relative to 100 parts by weight of the monomer component. Below, it may be 1 weight part or more and 5 weight part or less.

(tackifier) Adhesives may also be included in the adhesive compositions disclosed herein. As the tackifier, rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, Known tackifying resins such as elastic system tackifying resins. These can be used individually by 1 type or in combination of 2 or more types. The amount of tackifying resin used is not particularly limited, and can be set according to the purpose and application so that it can exert appropriate adhesive performance. In several aspects, from the viewpoint of refractive index or transparency, it is appropriate to use an amount of the tackifier relative to 100 parts by weight of the monomer component to be 30 parts by weight or less, preferably 10 parts by weight or less, It is more preferable to set it as 5 weight part or less. The technique disclosed here can be suitably implemented without using a tackifier.

(leveling agent) In several aspects, in order to improve the appearance of the adhesive layer formed by the composition (for example, to improve the uniformity of thickness) or to improve the applicability of the adhesive composition, etc., the adhesive composition may contain adjusting leveling agent. Non-limiting examples of leveling agents include acrylic leveling agents, fluorine leveling agents, and silicone leveling agents. As a leveling agent, for example, an appropriate one can be selected from commercially available leveling agents, and it can be used by a normal method.

In several aspects, the above-mentioned leveling agent can suitably use the following polymer (hereinafter also referred to as "polymer (B)"), which is a monomer comprising a polyorganosiloxane skeleton (hereinafter also referred to as "monomer (B)") S1") and acrylic monomer monomer raw material (hereinafter also referred to as "monomer raw material B") polymer. Polymer (B) may be referred to as a copolymer of monomer S1 and an acrylic monomer. A polymer (B) can be used individually by 1 type or in combination of 2 or more types.

The monomer S1 is not particularly limited, and any monomer having a polyorganosiloxane skeleton can be used. Monomer S1 can be suitably used as a structure having a polymerizable reactive group at one end. Among them, the monomer S1 having a structure having a polymerizable reactive group at one end and having no functional group having a crosslinking reaction with an acrylic polymer at the other end can be suitably used. Commercially available products include, for example, terminally reactive polysiloxane oils manufactured by Shin-Etsu Chemical Co., Ltd. (such as models X-22-174ASX, X-22-2426, X-22-2475, KF-2012, etc.). Monomer S1 can be used individually by 1 type or in combination of 2 or more types.

The functional group equivalent weight of the monomer S1 may be, for example, about 100 g/mol to 30000 g/mol. In several ideal aspects, the equivalent weight of the above-mentioned functional groups is, for example, 500 g/mol or more, may be 800 g/mol or more, may be 1500 g/mol or more, or may be 2000 g/mol or more. In addition, the above-mentioned functional group equivalent may be, for example, 20000 g/mol or less, may be less than 10000 g/mol, may be 7000 g/mol or less, or may be 5500 g/mol or less. If the functional group equivalent weight of the monomer S1 is within the above range, it is easy to exert a good leveling effect. In addition, when using two or more monomers with different functional group equivalents as the monomer S1, the functional group equivalent of the monomer S1 can be the sum of the products of the functional group equivalents of various types of monomers and the weight fraction of the monomers.

Here, "functional group equivalent" means the weight of the main skeleton (such as polydimethylsiloxane) bonded to each functional group. The related marking unit g/mol is converted into 1 mol of functional group. The functional group equivalent of the monomer S1 can be calculated from the spectral intensity of ¹ H-NMR (proton NMR) of nuclear magnetic resonance (NMR), for example. The functional group equivalent (g/mol) of monomer S1 based on the spectral intensity of ¹ H-NMR can be calculated according to the general structure analysis method related to ¹ H-NMR spectral analysis, and if necessary, refer to Japanese Patent No. 5951153 It shall be carried out according to the records in the Publication No. In the functional group equivalent of the monomer S1, the above-mentioned functional group means a polymerizable functional group (for example, ethylenically unsaturated groups such as (meth)acryl, vinyl, and allyl).

The content of the monomer S1 in the monomer raw material B can take an appropriate value within the range in which the desired effect can be exhibited by using the monomer S1, and is not limited to a specific range. In several aspects, the content of the monomer S1 in the monomer raw material B may be, for example, 5 to 60% by weight, 10 to 50% by weight, or 15 to 40% by weight.

The monomer raw material B includes, in addition to the monomer S1, an acrylic monomer that can be copolymerized with the monomer S1. Thereby, the compatibility of a polymer (B) in an adhesive layer can be improved. Acrylic monomers that can be used as the monomer raw material B include, for example, alkyl acrylates. The "alkyl group" mentioned here refers to a chain (including straight chain and branched chain) alkyl (group), and does not include the alicyclic hydrocarbon group described later. In several aspects, the monomer raw material B may contain a C _4-12 alkyl (meth)acrylate (preferably a C _4-10 alkyl (meth)acrylate, such as a C _{6- 10} alkyl esters). In several other aspects, monomer raw material B may contain C _1-18 alkyl methacrylate (preferably C _1-14 alkyl methacrylate, such as C _1-10 alkyl (meth)acrylate ester) at least one. Monomer raw material B may include, for example, one or two or more selected from methyl methacrylate (MMA), n-butyl methacrylate (BMA) and 2-ethylhexyl methacrylate (2EHMA) as an acrylic monomer.

Other examples of the above-mentioned acrylic monomers include (meth)acrylates having an alicyclic hydrocarbon group. For example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, 1-adamantyl (meth)acrylate Esters etc. A (meth)acrylate having an alicyclic hydrocarbon group may not be used.

The content of the (meth)acrylate having the above-mentioned alkyl (meth)acrylate and the above-mentioned alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10% by weight or more and 95% by weight or less, or may be 20% by weight or more and 95% by weight or less, 30% by weight or more and 90% by weight or less, 40% by weight or more and 90% by weight or less, or 50% by weight or more and 85% by weight or less.

Other examples of monomers that can be included in monomer raw material B together with monomer S1 include carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl-containing monomers, Epoxy-containing monomers, cyano-containing monomers, isocyanate-containing monomers, amide-containing monomers, monomers with nitrogen atom rings, aminoalkyl (meth)acrylates, vinyl esters , vinyl ethers, olefins, (meth)acrylates with aromatic hydrocarbon groups, (meth)acrylates with halogen atoms, etc.

The Mw of the polymer (B) may be, for example, not less than 5,000, preferably not less than 10,000, and may be not less than 15,000. Also, the Mw of the polymer (B) may be, for example, 200,000 or less, preferably 100,000 or less, 50,000 or less, or 30,000 or less. By setting the Mw of the polymer (B) within an appropriate range, good compatibility and leveling properties can be exhibited.

The polymer (B) can be produced, for example, by polymerizing the above-mentioned monomers by known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization. In order to adjust the molecular weight of the polymer (B), a chain transfer agent may be used as needed. Examples of chain transfer agents used include: tertiary dodecyl mercaptan, mercaptoethanol, α-thioglycerol and other compounds with mercapto groups; hydrogen thioacetates such as hydrogen thioacetic acid and methyl hydrogen thioacetate; Methylstyrene dimer, etc. The usage-amount of a chain transfer agent is not specifically limited, It can set suitably so that the polymer (B) which has a desired molecular weight can be obtained. In several aspects, the amount of the chain transfer agent relative to 100 parts by weight of the monomers may be, for example, 0.1-5 parts by weight, 0.2-3 parts by weight, or 0.5-2 parts by weight.

The usage-amount of polymer (B) can be 0.001 weight part or more with respect to 100 weight part of acrylic polymers, and can be 0.01 weight part or more from a viewpoint of obtaining a higher use effect, and can also be 0.01 weight part or more. 0.03 parts by weight or more. In addition, the amount of the polymer (B) used may be, for example, 3 parts by weight or less, and from the viewpoint of reducing the influence on the refractive index, it is appropriate to set it as 1 part by weight or less, and it may be 0.5 parts by weight or less. It may be 0.1 weight part or less. The technique disclosed here can be carried out in a state where the adhesive composition does not substantially contain the polymer (B).

(High Refractive Index Particles) The adhesive composition disclosed herein may contain high refractive index particles as an optional component. Here, the high-refractive-index particles mean particles that can increase the refractive index of the adhesive by including them in the adhesive. Hereinafter, high refractive index particles may be described as "particles P _HRI ". HRI means high refractive index (high refractive index).

For the particle P _HRI , for example, one or two or more types of particles made of materials having a refractive index of 1.60 or more, preferably 1.70 or more (maybe 1.80 or more, may be 1.90 or more, and may be 2.00 or more) may be used. The upper limit of the refractive index of the material constituting the particle P _HRI is not particularly limited, and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, 2.20 or less, or 2.00 or less. The refractive index of the material constituting the particle P _HRI is based on a single-layer film of the material (using a film thickness that can be measured for the refractive index), using a commercially available spectroscopic ellipsometer, under the conditions of a measurement wavelength of 589nm and a measurement temperature of 25°C Refractive index for measurement. As the spectroscopic ellipsometer, for example, a product name "EC-400" (manufactured by JA. Woolam Co., Ltd.) or an equivalent thereof can be used.

The type of particle P _HRI is not particularly limited, and one or more materials that can increase the refractive index of the adhesive can be selected from metal particles, metal compound particles, organic particles, and organic-inorganic composite particles. The particle P _HRI can be suitably used among inorganic oxides (such as metal oxides) that can increase the refractive index of the adhesive sheet. Suitable examples of materials constituting the particle P _HRI include titanium oxide (titania, TiO ₂ ), zirconia (zirconia, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide (Nb ₂ O ₅ , etc.) and other inorganic oxides (specifically, metal oxides). Particles composed of these inorganic oxides (for example, metal oxides) can be used alone or in combination of two or more. Among them, particles made of titanium oxide or zirconia are preferable, and particles made of zirconia are particularly preferable. In addition, metal particles, such as iron-based or zinc-based, tungsten-based, and platinum-based materials can have a high refractive index. Regarding organic particles, particles made of resins such as styrene-based resins, phenol resins, polyester-based resins, and polycarbonate-based resins have a relatively high refractive index. Examples of organic-inorganic composite particles include inorganic particles coated with an organic material such as a composite of the above-mentioned inorganic material and organic material, or a resin. From the viewpoint of compatibility with the adhesive components, the particle P _HRI can also use the above-mentioned organic and inorganic particles that have been surface-treated with a surface treatment agent.

The average particle diameter of the particles P _HRI is not particularly limited, and particles of an appropriate size that can achieve a desired increase in the refractive index can be used by including the binder. The average particle diameter of the particles P _HRI can be set to, for example, about 1 nm or more, and it is suitable to be about 5 nm or more. The average particle size of the particles P _HRI is preferably not less than about 10 nm, may be not less than about 20 nm, or may be not less than about 30 nm, from the viewpoint of increasing the refractive index or handling properties. Also, from the standpoint of maintaining adhesive properties, the upper limit of the average particle size is, for example, about 300 nm or less; and from the standpoint of increasing the refractive index, it is preferably about 100 nm or less, more preferably about 70 nm or less. It is about 50 nm or less, or about 35 nm or less (for example, about 25 nm or less).

In addition, the average particle diameter of the above-mentioned particle P _HRI refers to the volume average particle diameter, specifically, refers to the cumulative value in the particle size distribution measured for the particle P _HRI dispersion liquid using a particle size distribution measuring device based on the laser scattering diffraction method. 50% particle size (50% volume average particle size; hereinafter referred to as D ₅₀ ). As the measurement device, for example, "Microtrac MT3000II" manufactured by MicrotracBEL or its equivalent can be used.

The content of particle P _HRI in the adhesive composition is not particularly limited. The content of the particle P _HRI mentioned above may vary according to the refractive index of the object. For example, the content of the particle P _HRI described above can be appropriately set in consideration of the required adhesive properties and the like so that the refractive index can become a predetermined value or more. In several aspects, the content of the particles P _HRI in the adhesive composition can be set in the adhesive formed from the adhesive composition, for example, about 75% by weight or less, and from the viewpoint of adhesive properties or transparency From the point of view, it can be set to about 50% by weight or less, and can also be set to about 30% by weight or less. The lower limit of the content of particle P _HRI is not particularly limited, for example, it may be greater than 0% by weight, may be more than 1% by weight, or may be more than 5% by weight. In several other aspects, the content of the particle P _HRI in the adhesive composition in the adhesive formed from the adhesive composition, for example, is less than 10% by weight, may be less than 1% by weight, or may be less than 0.1% by weight . The technique disclosed here can be implemented in the state that the adhesive composition does not substantially contain particle P _HRI .

The content of particle P _HRI in the adhesive can also be specified in relation to the amount of acrylic polymer contained in the adhesive. With respect to 100 parts by weight of the acrylic polymer, the content of the particle P _HRI can be set to, for example, about 100 parts by weight or less, and from the viewpoint of adhesive properties or transparency, it can be set to about 60 parts by weight or less, or it can be set to about 100 parts by weight or less. 40 parts by weight or less. The lower limit of the content of the particles P _HRI is not particularly limited, and may be greater than 0 parts by weight, 1 part by weight or more, or 5 parts by weight or more relative to 100 parts by weight of the acrylic polymer. In several aspects, relative to 100 parts by weight of the acrylic polymer, the content of particle _PHRI is, for example, less than 30 parts by weight, may be less than 10 parts by weight, may be less than 1 part by weight, or may be less than 0.1 parts by weight.

(other additives) In addition, the adhesive composition disclosed here may also include softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, anti-aging Well-known additives such as UV absorbers, antioxidants, light stabilizers, and preservatives can be used in the adhesive composition. Also, in addition to the plasticizers disclosed here, known plasticizers (such as phthalate-based, terephthalate-based, adipate-based, adipate-based polymers, etc.) may also be included. One or more plasticizing materials such as ester, ethylene glycol benzoate, etc.) or liquid camphenol. As for the above-mentioned various additives, conventionally known ones can be used according to conventional methods, and since they do not give any characteristics to the present invention, detailed description thereof will be omitted.

＜Adhesive＞ The adhesive disclosed herein can be formed, for example, using any of the above-mentioned adhesive compositions. The adhesive may be an adhesive obtained by curing adhesive compositions in the form of solvent type, active energy ray curing type, water dispersion type, hot melt type, etc. by drying, crosslinking, polymerization, cooling, etc., that is, It may be a hardened product of the above-mentioned adhesive composition. The hardening means of the adhesive composition (such as drying, cross-linking, polymerization, cooling, etc.) can be applied only by one type, or two or more types can be applied simultaneously or in multiple stages. In the case of solvent-based adhesive compositions, typically the composition can be dried (preferably further cross-linked) to form the adhesive. In the case of an active energy ray-curable adhesive composition, typically, an adhesive is formed by irradiating an active energy ray to proceed a polymerization reaction and/or a crosslinking reaction. When the active energy ray-curable adhesive composition must be dried, the active energy ray may be irradiated after drying.

(refractive index) The refractive index of the adhesive formed from the adhesive composition disclosed herein is higher than that of conventional acrylic adhesives. According to the technique disclosed here, there can be provided an adhesive having a refractive index of, for example, 1.55 or higher, an adhesive composition capable of forming the adhesive, and an adhesive sheet including the above adhesive. The refractive index of the above-mentioned adhesive is more than 1.560, preferably greater than 1.570. In several aspects, the refractive index of the above-mentioned adhesive may be 1.575 or higher, 1.580 or higher, or 1.585 or higher. According to the adhesive having the above-mentioned refractive index, it is possible to suitably suppress light reflection at the interface with the adherend in the use mode where it is attached to a material with a high refractive index. The ideal upper limit of the refractive index of the adhesive can vary depending on the refractive index of the adherend, so it is not limited to a specific range. For example, it can be 1.700 or less, 1.670 or less, 1.650 or less, 1.620 or less, or It can be below 1.600.

The refractive index of the adhesive can be adjusted by, for example, the composition of the adhesive (eg, the composition of monomer components constituting an acrylic polymer). Specifically, by including an acrylic polymer or an additive (H _RO ) with a large content of the monomer (A1) in the monomer component, it is possible to prepare an adhesive exhibiting a predetermined or higher refractive index.

In addition, in this specification, the refractive index of an adhesive means the refractive index of the surface (adhesive surface) of this adhesive. The refractive index of the adhesive can be measured under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C. using a commercially available refractive index measuring device (Abbe refractometer). As an Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO Corporation or its equivalent can be used. As the measurement sample, an adhesive layer composed of the adhesive to be evaluated can be used. Specifically, the refractive index of the adhesive can be measured by the method described in Examples described later.

(Storage elastic modulus G') According to the technology disclosed here, it is possible to have a high refractive index and at the same time realize a low elastic modulus of the adhesive. Although not limited to a specific range, the storage elastic modulus G'(0°C) of the adhesive at 0°C, for example, may be less than 1.0×10 ⁸ Pa, may be less than 5.0×10 ⁷ Pa, may be less than 1.0×10 ⁷ Pa, or It can be less than 5.0×10 ⁶ Pa. The adhesive having the above-mentioned storage elastic modulus G'(0°C) has moderate flexibility in the temperature range from around 0°C to above, and can adhere well to the adherend, for example. The lower limit of the storage elastic modulus G'(0°C) is not particularly limited, and is, for example, 1.0×10 ² Pa or more, or 1.0×10 ³ Pa or more. When the storage elastic modulus G'(0° C.) is equal to or greater than a predetermined value, the adhesive, for example, tends to have an appropriate cohesive force in a range from normal temperature to high temperature. In several ideal forms, the storage elastic modulus G'(0°C) of the adhesive is less than 1.0×10 ⁶ Pa, preferably less than 5.0×10 ⁵ Pa, may be less than 2.0×10 ⁵ Pa, may be 1.0×10 ⁵ Pa or less, may be 7.0×10 ⁴ Pa or less, may be 5.0×10 ⁴ Pa or less, or may be 3.0×10 ⁴ Pa or less. Also, the storage elastic modulus G'(0°C) is preferably at least 1.0×10 ⁴ Pa, more preferably at least 2.0×10 ⁴ Pa, more preferably at least 4.0×10 ⁴ Pa, and may be at least 6.0×10 ⁴ Pa. , can also be 1.0×10 ⁵ Pa or more. Adhesives having a storage modulus of elasticity G'(0°C) in the above range can have both high refractive index and flexibility, and have the flexibility to withstand repeated bending operations.

The storage elastic modulus G'(80°C) of the adhesive disclosed here is not particularly limited, for example, less than 1.0×10 ⁵ Pa is appropriate, preferably less than 5.0×10 ⁴ Pa, more preferably less than 3.0×10 ⁴ Pa, may be less than 1.0×10 ⁴ Pa, or may be less than 5.0×10 ³ Pa. Adhesives with limited storage elastic modulus G'(80°C) have good flexibility in high temperature regions. The lower limit of the storage elastic modulus G'(80°C) is not particularly limited, for example, it is 1.0×10 ² Pa or more, preferably 5.0×10 ² Pa or more, preferably 1.0×10 ³ Pa or more, more preferably 3.0 ×10 ³ Pa or more, or 5.0×10 ³ Pa or more. An adhesive having the above-mentioned storage elastic modulus G' (80° C.) has moderate cohesive force even in a high-temperature region, and tends to be excellent in heat resistance, so it is desirable.

The storage elastic modulus G'(-10°C) of the adhesive disclosed here is not particularly limited, for example, it may be less than 1.0×10 ⁹ Pa, less than 1.0×10 ⁸ Pa, or less than 1.0×10 ⁷ Pa It is appropriate, and it is preferably 5.0×10 ⁶ Pa or less, may be 1.0×10 ⁶ Pa or less, may be 5.0×10 ⁵ Pa or less, and may be 1.0×10 ⁵ Pa or less. Adhesives whose storage modulus of elasticity G'(-10°C) is limited as above can have more excellent flexibility. For example, it can have good flexibility in a low-temperature range and flexibility to withstand repeated bending operations in a wide temperature range including a low-temperature range. The lower limit of the storage elastic modulus G'(-10°C) is not particularly limited, for example, it is 1.0×10 ² Pa or more, 1.0×10 ³ Pa or more is appropriate, preferably 5.0×10 ³ Pa or more, more preferably 1.0×10 ⁴ Pa or more, may be 5.0×10 ⁴ Pa or more, may be 1.0×10 ⁵ Pa or more, or may be 5.0×10 ⁵ Pa or more. Adhesives having the above-mentioned storage elastic modulus G'(-10°C) can be soft and have moderate cohesive force. Moreover, according to the adhesive agent which has the said storage elastic modulus G'(-10 degreeC), it tends to be easy to achieve both high refractive index and flexibility even in a low temperature range.

The storage elastic modulus G'(-20°C) of the adhesive disclosed here is not particularly limited, for example, it may be less than 1.0×10 ¹⁰ Pa, may be less than 1.0×10 ⁹ Pa, and may be 5.0×10 ⁸ Pa The following are suitable, and may be 1.0×10 ⁸ Pa or less, 5.0×10 ⁷ Pa or less, 1.0×10 ⁷ Pa or less, 5.0×10 ⁶ Pa or less, 1.0×10 ⁶ Pa or less, It may be 5.0×10 ⁵ Pa or less. Adhesives whose storage elastic modulus G'(-20°C) is limited as above can have particularly excellent flexibility. For example, it can have good flexibility in a lower temperature range, and can withstand repeated bending operations in a wide temperature range including a low temperature range. The lower limit of the storage elastic modulus G'(-20°C) is not particularly limited, for example, it is 1.0×10 ² Pa or more, preferably 1.0×10 ³ Pa or more, preferably 1.0×10 ⁴ Pa or more, more preferably 1.0×10 ⁵ Pa or more, may be 5.0×10 ⁵ Pa or more, or may be 1.0×10 ⁶ Pa or more. Adhesives having the above-mentioned storage elastic modulus G'(-20°C) can be soft and have moderate cohesive force. Moreover, according to the adhesive agent which has the said storage elastic modulus G'(-20 degreeC), it exists in the tendency for a high refractive index and flexibility to be easily compatible even in a low temperature range.

(Storage elastic modulus ratio) In several aspects, as an adhesive, the ratio of the storage elastic modulus G'(0°C) at 0°C to the storage elastic modulus G'(80°C) at 80°C (G'(0°C) can be used ℃)/G'(80℃)) in the range of 1~1000. According to the adhesive that satisfies the above characteristics, since the elastic modulus change can be suppressed in a wide temperature range from 0°C to a high temperature range, it is easy to exhibit stable characteristics (flexibility, etc.) against temperature changes. The above ratio (G'(0°C)/G'(80°C)) is suitably 300 or less, preferably 100 or less, more preferably 50 or less, may be 25 or less, may be 10 or less, or may be 5 or less . The lower limit of the ratio (G'(0°C)/G'(80°C)) may be, for example, 2 or more, or may be 3 or more.

In several aspects, as an adhesive, the ratio of the storage modulus of elasticity G' at -10°C (-10°C) to the storage modulus of elasticity G' at 80°C (80°C) can be used (G' (-10°C)/G'(80°C)) in the range of 1~1000. According to an adhesive satisfying the above-mentioned characteristics, since the change in elastic modulus can be suppressed in a wide temperature range from a low temperature range to a high temperature range, it is easy to exhibit stable characteristics (flexibility, etc.) against temperature changes, which is ideal. The ratio (G'(-10°C)/G'(80°C)) is suitably 300 or less, preferably 150 or less, more preferably 100 or less, may be 50 or less, may be 30 or less, may be 20 or less, It may be 10 or less. The lower limit of the ratio (G'(-10°C)/G'(80°C)) may be, for example, 2 or more, or 3 or more.

In several aspects, as an adhesive, the ratio of the storage modulus of elasticity G' at -20°C (-20°C) to the storage modulus of elasticity G' at 80°C (80°C) (G' (-20°C)/G'(80°C)) in the range of 1~1000. According to the adhesive that satisfies the above characteristics, since the change in elastic modulus can be suppressed in a wide temperature range from a lower temperature range to a high temperature range, stable properties (flexibility, etc.) against temperature changes can be exhibited. The ratio (G'(-20°C)/G'(80°C)) may be 500 or less, 300 or less, 150 or less, 100 or less, 50 or less, or 30 or less. The lower limit of the ratio (G'(-20°C)/G'(80°C)) may be, for example, 5 or more, 10 or more, 50 or more, or 100 or more.

The glass transition temperature (Tg) of the adhesive is not particularly limited, and can be set in consideration of flexibility in a low-temperature region or cohesive force (heat resistance, etc.) in a high-temperature region. In several aspects, the Tg of the adhesive is, for example, 30°C or lower, may be 15°C or lower, or may be 5°C or lower. In several ideal aspects, from the viewpoint of flexibility, the Tg of the adhesive is below 0°C, more preferably below -5°C, more preferably below -10°C, and may also be below -15°C (for example below -20°C). The lower the Tg of the adhesive, the better the adhesive properties such as the adhesion to the adherend tend to be. Also, by setting the Tg of the adhesive low, the change in elastic modulus in the temperature region higher than Tg can be suppressed. The lower limit of Tg of the adhesive is, for example, -50°C or higher, preferably -40°C or higher, and may be -30°C or higher. According to the adhesive having the above Tg, it tends to be easy to obtain an appropriate cohesive force. Also, it tends to be easy to form an adhesive having both a high refractive index and a low modulus of elasticity.

The storage elastic modulus G' of the adhesive at the above-mentioned temperatures and the glass transition temperature Tg of the adhesive can be measured by the method described in the examples below, and the storage elastic modulus ratios can be calculated from the results. The storage elastic modulus G', the storage elastic modulus ratio and the glass transition temperature Tg of the adhesive, for example, can be selected by selecting the composition of the monomer components constituting the acrylic polymer (such as selecting the type and content of the monomer (A1) ), choose the type or amount of plasticizer, whether to use cross-linking agent and choose the type and amount, whether to use additives, choose the type and amount to adjust.

＜Adhesive sheet＞ According to this specification, there is provided an adhesive sheet having an adhesive layer. The adhesive constituting the above-mentioned adhesive layer may be an adhesive formed of any adhesive composition disclosed herein (for example, a cured product of the adhesive composition). The above-mentioned adhesive sheet may be an adhesive sheet with a substrate in the form of having the above-mentioned adhesive layer on one or both sides of a non-peelable substrate (supporting substrate), or may be in a form in which the above-mentioned adhesive layer is held on a release liner Adhesive sheets without a base material (that is, an adhesive sheet without a non-peelable base material, typically an adhesive sheet composed of an adhesive layer). The concept of an adhesive sheet mentioned here may include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. The adhesive sheet disclosed here may be in the form of a roll or a single sheet. Alternatively, it may be an adhesive sheet that is further processed into various shapes.

Figures 1 and 2 show configuration examples of a double-sided adhesive type non-substrate adhesive sheet (substrate-less double-sided adhesive sheet). The adhesive sheet 1 shown in FIG. 1 has a structure in which both surfaces 21A, 21B of an adhesive layer 21 without a base material are protected by release liners 31, 32, at least on which the adhesive layer side is a release surface. The adhesive sheet 2 shown in FIG. 2 has a structure in which one surface (adhesive surface) 21A of the adhesive layer 21 without a substrate is protected by a release liner 31 whose both sides are release surfaces, and can be made into the following structure: During winding, the other surface (adhesive surface) 21B of the adhesive layer 21 abuts against the back surface of the release liner 31 , whereby the other surface 21B is also protected by the release liner 31 . From the point of view of the flexibility of the conformable adherend that can be bent repeatedly, the technology disclosed here is suitable for implementation in the form of an adhesive sheet without a base material composed of an adhesive layer. The aforementioned adhesive sheet without a base material is also preferable from the viewpoint of reducing the thickness of the adhesive sheet or improving the transparency of the adhesive sheet, for example.

The adhesive sheet disclosed here may have, for example, the cross-sectional structure schematically shown in FIG. 3 . The adhesive sheet 3 shown in FIG. 3 includes a support substrate 10 , and a first adhesive layer 21 and a second adhesive layer 22 each supported by the first surface 10A and the second surface 10B of the support substrate 10 . Both the first surface 10A and the second surface 10B are non-peeling surfaces (non-peeling surfaces). The adhesive sheet 3 is used by attaching the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 to an adherend. That is, the adhesive sheet 3 is constituted as a double-sided adhesive sheet (adhesive sheet with double-sided adhesiveness). The adhesive sheet 3 before use has a structure in which each of the first adhesive surface 21A and the second adhesive surface 22A is protected by release liners 31 and 32 , which are at least the adhesive surface side as a releasable surface (release surface). Alternatively, the following configuration can also be made: the release liner 32 is omitted, and the release liner 31 is used with both sides as the release surface, and the adhesive sheet 3 is wound so that the second adhesive surface 22A abuts against the inner surface of the release liner 31. This second adhesive surface 22A is also protected by a release liner 31 .

The technology disclosed here is preferably implemented in the form of the above-mentioned substrate-less or substrate-attached double-sided adhesive sheet for fixing or bonding components (eg, optical components). Alternatively, although not shown in particular, the adhesive sheet disclosed here may be in the form of a single-sided adhesive sheet with a substrate having an adhesive layer on only one side of a non-peelable substrate (support substrate). As an example of the form of a single-sided adhesive sheet, the form which does not have any of the 1st adhesive agent layer 21 and the 2nd adhesive agent layer 22 in the structure shown in FIG. 3 is mentioned.

(adhesive layer) The adhesive layer of the adhesive sheet disclosed here can be formed by applying (for example, coating) an adhesive composition to an appropriate surface and then hardening the composition. For the coating of the adhesive composition, conventional coating methods such as gravure roll coater, reverse roll coater, touch roll coater, dip roll coater, rod coater, knife coater, spray coater, etc. can be used. cloth machine to implement.

The thickness of the adhesive layer is not particularly limited, for example, it can be set to 3 µm or more. In several aspects, the thickness of the adhesive layer is, for example, 5 µm or more, 10 µm or more, 15 µm or more, 20 µm or more, 30 µm or more, 50 µm or more, or 70 µm or more. Or more than 85µm. By increasing the thickness of the adhesive layer, the adhesion tends to increase. Also, in several aspects, the thickness of the adhesive layer may be, for example, 300 µm or less, 250 µm or less, 200 µm or less, 150 µm or less, or 120 µm or less. In several ideal aspects, the thickness of the adhesive layer is less than 100 µm, more preferably less than 75 µm, more preferably less than 70 µm, may be less than 50 µm, or may be less than 30 µm. The fact that the thickness of the adhesive layer is not too large is advantageous from the viewpoint of reducing the thickness of the adhesive sheet. Furthermore, a thin adhesive layer tends to be excellent in compliance with an adherend. For example, the technique disclosed here can be suitably implemented in an aspect in which the thickness of the adhesive layer is in the range of 3 µm to 200 µm (preferably 5 µm to 100 µm, more preferably 5 µm to 75 µm). In addition, in the case of an adhesive sheet having a first adhesive layer and a second adhesive layer on the first surface and the second surface of the substrate, the thickness of the above-mentioned adhesive layer can be applied at least to the thickness of the first adhesive layer. The thickness of the second adhesive layer can also be selected from the same range. Also, in the case of an adhesive sheet without a substrate, the thickness of the adhesive sheet is the same as the thickness of the adhesive layer.

In several aspects, the product of the storage elastic modulus G'(0°C) [Pa] of the adhesive at 0°C and the thickness T [µm] of the adhesive layer (G'(0°C)×T) is for example It is appropriate to be within the range of 5.0×10 ⁴ ~7.5×10 ⁷ , preferably within the range of 5.0×10 ⁴ ~5.0×10 ⁷ . In a thin adhesive layer, even if it has a relatively high modulus of elasticity, since it has the product (G'(0°C)×T) in the above range, it is easy to have good flexibility. Also, by limiting the above-mentioned product (G'(0°C)×T) below a predetermined value, the thickness of the adhesive layer and the upper limit of the storage elastic modulus G'(0°C) are limited, thereby making it easy to obtain Excellent flexibility. In some ideal aspects, the above-mentioned area (G'(0°C)×T) may be 1.0×10 ⁵ or more, 2.0×10 ⁵ or more, or 8.0×10 ⁵ or more. In addition, the above-mentioned product (G'(0°C)×T) may be 2.0×10 ⁷ or less, 1.0×10 ⁷ or less, or 6.0×10 ⁶ or less.

(haze value) In several aspects, the haze value of the adhesive layer constituting the adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, and may be 0.9% or less , can be 0.8% or less, can be 0.5% or less, can also be 0.3% or less. The adhesive sheet having the above-mentioned high-transparency adhesive layer can have a base material or no base material, and is suitable for applications that require high light transmission (such as optical applications), or that can pass through the adhesive sheet. For the purpose of visually identifying the performance of the adherend. The lower limit of the haze value of the adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the better. On the other hand, in some aspects, the haze value may be, for example, 0.05% or more, or may be 0.10% or more in consideration of the refractive index and adhesive properties. These haze values regarding the adhesive layer can also be suitably applied to the adhesive sheet when the technique disclosed here is implemented in the form of an adhesive sheet without a base material (typically, an adhesive sheet composed of an adhesive layer). haze value.

Here, the "haze value" means the ratio of diffusely transmitted light to total transmitted light when visible light is irradiated to the measurement object. Also known as Haze Value. The haze value can be represented by the following formula. Th(%)=Td/Tt×100 In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total light transmittance. The measurement of the haze value can be performed according to the method described in the examples described later. The haze value of the adhesive layer can be adjusted by, for example, selecting the composition or thickness of the adhesive layer.

In several aspects, the haze value of the adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, may be 0.9% or less, may be 0.8% It may be less than 0.5%, or less than 0.3%. An adhesive sheet with high transparency as described above can be suitably used in applications requiring high light transmittance (such as optical applications), or applications requiring the performance of an adherend to be seen well through the adhesive sheet. The lower limit of the haze value of the adhesive sheet is not particularly limited, and from the viewpoint of improving transparency, the lower the haze value, the better. On the other hand, in some aspects, the haze value may be, for example, 0.05% or more, or may be 0.10% or more in consideration of the refractive index and adhesive properties. The haze value of the adhesive sheet can be measured by the same method as the measurement of the haze value of the above-mentioned adhesive layer. The above-mentioned haze value of the adhesive sheet can be obtained by selecting the composition of the above-mentioned adhesive layer, etc., or selecting the type of substrate or the thickness of the substrate in the configuration with a substrate.

In several aspects, the total light transmittance of the adhesive layer is preferably 85.0% or more (for example, 88.0% or more, 90.0% or more or greater than 90.0%). The adhesive sheet having the above-mentioned high-transparency adhesive layer can have a base material or no base material, and is suitable for applications that require high light transmission (such as optical applications), or that can pass through the adhesive sheet. For the purpose of visually identifying the performance of the adherend. In practice, the upper limit of the total light transmittance may be, for example, about 98% or less, about 96% or less, or about 95% or less. In several aspects, the total light transmittance of the adhesive layer may be less than about 94%, may be less than about 93%, or may be less than about 92%, considering the refractive index or adhesive properties. The total light transmittance was measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used. The total light transmittance can be measured according to the method described in the examples described later. The total light transmittance of the adhesive layer can be adjusted by, for example, selecting the composition or thickness of the adhesive layer.

In several aspects, the total light transmittance of the adhesive sheet is preferably 85.0% or more (for example, 88.0% or more, 90.0% or more or greater than 90.0%). An adhesive sheet with high transparency as described above can be suitably used in applications requiring high light transmittance (such as optical applications), or applications requiring the performance of an adherend to be seen well through the adhesive sheet. In practice, the upper limit of the total light transmittance may be, for example, about 98% or less, about 96% or less, or about 95% or less. In several aspects, considering the refractive index or adhesive properties, the total light transmittance of the adhesive sheet may be less than about 94%, less than about 93%, or less than about 92%. The total light transmittance of the adhesive sheet can be measured by the same method as the measurement of the total light transmittance of the above-mentioned adhesive layer. The total light transmittance of the adhesive sheet can be obtained by selecting the composition of the above-mentioned adhesive layer, or selecting the type of substrate or the thickness of the substrate in the configuration with the substrate.

(peel strength) The peel strength of the adhesive sheet to the glass plate is not particularly limited. In some aspects, the peeling strength of the adhesive sheet to the glass plate is, for example, 0.1 N/25 mm or more, and may be 0.5 N/25 mm or more. In several ideal forms, the above-mentioned peel strength to the glass plate is above 1.0N/25mm, more preferably above 1.5N/25mm, more preferably above 2.0N/25mm, can be above 3.0N/25mm, can be 5.0N/25mm or more, or 10N/25mm or more. As mentioned above, the adhesive sheet whose peeling strength with respect to a glass plate is more than predetermined value is suitable for joining or fixing glass members etc., for example. The upper limit of the peel strength is not particularly limited, and may be, for example, 30 N/25 mm or less, 25 N/25 mm or less, or 20 N/25 mm or less.

Here, the above-mentioned peeling strength is grasped by the following method: After being crimped on an alkali glass plate as an adherend and left in an environment of 23°C and 50%RH for 30 minutes, at a peeling angle of 180 degrees, pulling Peel strength was measured under the condition of elongation speed 300mm/min. During the measurement, an appropriate substrate (such as a polyethylene terephthalate (PET) film with a thickness of about 25 μm to about 50 μm) can be attached to the adhesive sheet of the measurement object for reinforcement. More specifically, the peel strength can be measured in accordance with the method described in the examples described later.

(thickness of adhesive sheet) The thickness of the adhesive sheet disclosed here (adhesive sheet without substrate or adhesive sheet with substrate) may be, for example, 1000 µm or less, 350 µm or less, 200 µm or less, 120 µm or less, 75 µm or less, or It can be less than 50µm. In addition, from the viewpoint of handleability, etc., the thickness of the adhesive sheet may be, for example, 5 µm or more, 10 µm or more, 25 µm or more, 80 µm or more, or 130 µm or more. In addition, the thickness of an adhesive sheet means the thickness of the part attached to the adherend. For example, in the adhesive sheet 3 having the configuration shown in FIG. 3 , the thickness from the first adhesive surface 21A to the second adhesive surface 22A does not include the thickness of the release liners 31 and 32 .

＜Support base material＞ The adhesive sheet of several aspects may be in the form of an adhesive sheet with a substrate having an adhesive layer on one side or both sides of the supporting substrate. The material of the supporting base material is not particularly limited, and can be appropriately selected according to the purpose or mode of use of the adhesive sheet. Non-limiting examples of substrates that can be used include: polyolefin films mainly composed of polyolefins such as polypropylene (PP) and ethylene-propylene copolymers, polyethylene terephthalate (PET), polyethylene Plastic films such as polyester films mainly composed of polyesters such as butylene terephthalate (PBT), polyethylene naphthalate (PEN), and polyvinyl chloride films mainly composed of polyvinyl chloride; Foam sheet composed of polyurethane foam, polyethylene (PE) foam, polychloroprene foam and other foams; various fibrous materials (can be hemp, cotton and other natural fibers , polyester, vinylon and other synthetic fibers, acetate and other semi-synthetic fibers, etc.) woven and non-woven fabrics alone or blended; Japanese paper, Dorin paper, kraft paper, crepe paper and other papers; aluminum foil, copper foil and other metal foils, etc. It can also be used as a base material for such a composite structure. Examples of the composite base material include a base material in which a metal foil and the above-mentioned plastic film are laminated, a plastic base material reinforced with inorganic fibers such as glass cloth, and the like.

In several aspects, various film substrates may be suitably used. The above-mentioned film base material may be a porous base material such as a foam film or a non-woven sheet, a non-porous base material, or a structure composed of a porous layer and a non-porous laminated layer. Substrate. In several aspects, the above-mentioned film base material can preferably use a resin film that is independent and maintains its shape (self-supporting or independent) as a base film. Here, the "resin film" refers to a resin film having a non-porous structure and typically substantially free of air bubbles (no holes). Therefore, the above-mentioned resin film is a concept that can be distinguished from a foam film or a nonwoven fabric. The above-mentioned resin film can be suitably used independently and can maintain its shape (self-supporting or independent). The above-mentioned resin film may have a single-layer structure, or may have a multi-layer structure of two or more layers (for example, a three-layer structure).

The resin material constituting the resin film can be used, for example: polyester; polyolefin; polycycloolefin derived from a monomer having an aliphatic ring structure such as norcamphene structure; Polyamide (PA); transparent polyimide (CPI) and other polyimide (PI); polyamide imide (PAI); polyetheretherketone (PEEK); Phenylsulfide (PPS); Polycarbonate (PC); Polyurethane (PU); Ethylene-vinyl acetate copolymer (EVA); Fluorine resins such as polytetrafluoroethylene (PTFE); Acrylic resin; Triacetic acid Cellulosic polymers such as cellulose (TAC); polyarylate; polystyrene; polyvinyl chloride; polyvinylidene chloride and other resins.

The above-mentioned resin film may be formed using a resin material containing one of the above-mentioned resins alone, or may be formed using a resin material in which two or more types are blended. The aforementioned resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched). For example, PET film, PBT film, PEN film, non-stretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low-density polyethylene (LDPE) film, linear low-density polyethylene ( LLDPE) film, PP/PE blend film, cycloolefin polymer (COP) film, CPI film, TAC film, etc. From the standpoint of strength or dimensional stability, examples of desirable resin films include PET films, PEN films, PPS films, and PEEK films. From the standpoint of availability and the like, PET films and PPS films are particularly preferred, and PET films are particularly preferred.

In the resin film, light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slipping agents (slipping agents), Known additives such as anti-caking agents. The blending amount of additives is not particularly limited, and can be appropriately set according to the application of the adhesive sheet.

The method for producing the resin film is not particularly limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be suitably used.

The aforementioned substrate may be substantially composed of the base film. Alternatively, the base material may also include an auxiliary layer in addition to the base film. Examples of the auxiliary layer mentioned above include an optical characteristic adjustment layer (such as a coloring layer, an antireflection layer), a printing layer or a lamination layer for imparting a desired appearance to a base material, an antistatic layer, and a primer layer. , peeling layer and other surface treatment layers.

In some aspects, a light-transmitting substrate (hereinafter also referred to as a light-transmitting substrate) can be suitably used as the support substrate. In this way, an adhesive sheet with a light-transmitting base material can be formed. The total light transmittance of the light-transmitting substrate may be, for example, greater than 50%, and may also be greater than 70%. In several ideal aspects, the total light transmittance of the supporting substrate is above 80%, more preferably above 90%, and may also be above 95% (eg, 95-100%). The above-mentioned total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used. A suitable example of the above-mentioned light-transmitting base material is a resin film having light-transmitting properties. The above light transmissive substrate may also be an optical film.

The thickness of the base material is not particularly limited, and can be selected according to the purpose or mode of use of the adhesive sheet. The thickness of the substrate may be, for example, 500 µm or less, and from the standpoint of handling or processability of the adhesive sheet, it is preferably 300 µm or less, may be 150 µm or less, may be 100 µm or less, may be 50 µm or less, and may be 25 µm or less. It can also be 10 µm or less. When the thickness of the substrate becomes smaller, the conformability to the surface shape of the adherend tends to increase. In addition, from the standpoint of handleability, processability, etc., the thickness of the substrate may be, for example, 2 µm or more, 10 µm or more, or 25 µm or more.

The surface of the base material on which the adhesive layer is to be laminated can also be subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and primer formation by coating a primer (primer) as required. Conventionally known surface treatment such as coating. The surface treatment may be a treatment for improving the anchorage of the adhesive layer to the substrate. The composition of the primer for forming the primer layer is not particularly limited, and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, and is usually about 0.01 µm to 1 µm, and preferably about 0.1 µm to 1 µm. Other treatments that can be performed on the base material according to the needs include antistatic layer forming treatment, colored layer forming treatment, printing treatment, etc. These treatments can be applied alone or in combination.

＜Adhesive sheet with release liner＞ The adhesive sheet disclosed here can take the form of an adhesive product in which the surface of the adhesive layer (adhesive surface) is in contact with the release surface of the release liner. Therefore, according to the present specification, there is provided an adhesive sheet with a release liner (adhesive product), which comprises any adhesive sheet disclosed herein and a release liner having a release surface abutting against the adhesive surface of the adhesive sheet.

The release liner is not particularly limited. For example, it can be used for a release liner with a release layer on the surface of a liner substrate such as a resin film or paper (it can be a paper laminated with a resin such as polyethylene), or a release liner made of fluorine. A release liner made of a resin film formed of a low adhesive material such as a polymer (polytetrafluoroethylene, etc.) or a polyolefin resin (polyethylene, polypropylene, etc.). In terms of excellent surface smoothness, it can be suitably used as a release liner having a release layer on the surface of a resin film as a liner base material, or a release liner composed of a resin film formed of a low-adhesion material. The resin film is not particularly limited as long as it can protect the adhesive layer, for example, polyethylene (PE) film, polypropylene (PP) film, polybutene film, polybutadiene film, polymethylpentene film , polyvinyl chloride film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-ethyl acetate copolymer film, etc. Formation of the above peeling layer can use, for example, silicone-based peeling agents, long-chain alkyl-based peeling agents, olefin-based peeling agents, fluorine-based peeling agents, aliphatic amide-based peeling agents, molybdenum sulfide, Known peeling agent such as silicon powder.

＜Use＞ The use of the adhesive sheet disclosed here is not limited, and it can be used for various purposes. The adhesive sheet disclosed here has an adhesive having both a high refractive index and a low modulus of elasticity, so its characteristics can be utilized in various applications requiring high refractive index and flexibility. For example, in electronic equipment such as portable electronic equipment, it is suitable as a display device (image display device) such as a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), electronic paper, or a touch screen. Adhesive sheets for devices such as input devices such as panels (optical devices), especially foldable displays or rollable displays. For example, in foldable displays and rollable displays, it can be suitably used as a mechanism for joining, fixing, and protecting members having a high refractive index. The adhesive sheet disclosed here can have a high refractive index and at the same time have the flexibility to withstand repeated bending operations, so it can be adhered to the repeated bending when it is attached to a foldable display or a rollable display. body (foldable display, etc.). The object to be attached in the above-mentioned usage form includes glass members such as window glass or cover glass that can be used for foldable displays or rollable displays. Moreover, the adhesive sheet disclosed here is also easy to conform and adhere to curved surfaces such as 3-dimensional shapes of portable electronic devices, so it is also suitable for use in electronic devices with such curved shapes. In addition, in several ideal aspects, the adhesive may be excellent in heat resistance in addition to having a high refractive index and a low modulus of elasticity. The above-mentioned portable electronic equipment is sometimes used in a high-temperature environment, and its internal space may be heated due to heat generated by electronic parts, so the use of the above-mentioned heat-resistant adhesive sheet has great advantages.

Examples of the above-mentioned portable electronic devices also include: mobile phones, smart phones, tablet computers, notebook computers, various wearable devices (such as wristbands worn on the wrist such as watches, in the form of clips or pendants, etc.) Modular type attached to a part of the body, eye-mounted type including glasses type (single eye type or binocular type; including head-mounted type), clothing type attached to shirts or socks, hats, etc. in the form of accessories, for example , earphones and other ear-mounted earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), computers (computers, etc.), portable game consoles , electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information machines, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. In addition, in this specification, the term "portable" is not enough to merely be portable, but also refers to a degree of portability that can be relatively easily carried by an individual (standard adult).

The material (material of the adherend) that can be attached to the adhesive sheet disclosed here is not particularly limited, for example: copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc. or containing such Metal materials such as alloys of two or more kinds, or polyimide resins, acrylic resins, polyether nitrile resins, polyether nitrile resins, polyester resins (PET resins, polynaphthalene di ethylene formate-based resin, etc.), polyvinyl chloride-based resin, polyphenylene sulfide-based resin, polyetheretherketone-based resin, polyamide-based resin (so-called aramid resin, etc.), polyarylate-based resin , polycarbonate-based resins, cellulose-based polymers such as cellulose diacetate or cellulose triacetate, vinyl butyral-based polymers, liquid crystal polymers, and other resin materials (typically plastic materials), alumina, Inorganic materials such as zirconia, alkali glass, alkali-free glass, quartz glass, carbon, etc. The adhesive sheet disclosed here can be attached to a member (such as an optical member) made of the above-mentioned materials.

The member or material to be attached to the adhesive sheet disclosed here (at least one adherend in the double-sided adhesive sheet) may be made of a material with a higher refractive index than general acrylic adhesives. The refractive index of the material to be adhered is, for example, 1.50 or more. Among them, there are also adherend materials with a refractive index of 1.55 or more or 1.58 or more, and there are also those with a refractive index of 1.62 or more (for example, about 1.66). The adherend material with a high refractive index is typically a resin material. More specifically, polyester-based resins such as PET, polyimide-based resins, aramid resins, polyphenylene sulfide-based resins, polycarbonate-based resins, and the like may be used. Such a material can suitably exhibit the effect of using the adhesive sheet disclosed here (suppression of reflection of light due to a difference in refractive index). The upper limit of the refractive index of the said to-be-adhered body material is 1.80 or less, for example, and may be 1.70 or less. The adhesive sheet disclosed here is suitably used in a state of being attached to the above-mentioned high-refractive-index adherend (for example, a member). A suitable example of the adherend may be a resin film with a refractive index of 1.50-1.80 (preferably 1.55-1.75, eg 1.60-1.70). The above-mentioned refractive index can be measured by the same method as the refractive index of the adhesive.

The member or material to be attached to the adhesive sheet (at least one adherend in the double-sided adhesive sheet) may be light transmissive. For the adherend, the advantage of the effect (suppression of light reflection at the interface between the adherend and the adhesive sheet) brought about by the technology disclosed here is easily obtained. The total light transmittance of the above-mentioned adherend may be, for example, greater than 50%, preferably greater than 70%. In several ideal aspects, the total light transmittance of the above-mentioned adherend is above 80%, preferably above 90%, and may be above 95% (for example, 95-100%). The adhesive sheet disclosed here is preferably used in a state of being attached to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The above-mentioned total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used.

In several ideal aspects, the adherend (for example, a member) to which the adhesive sheet is attached may have the above-mentioned refractive index and the above-mentioned total light transmittance. Specifically, the adhesive sheet disclosed here can be suitably attached to a film with a refractive index of 1.50 or higher (such as 1.55 or higher, 1.58 or higher, 1.62 or higher, 1.66 or so) and a total light transmittance greater than 50% (such as 70% or higher, 1.66 or higher, etc.) It should be more than 80%, preferably more than 90%, more preferably more than 95%) of the adherend, such as a member. In the form attached to the member, the effects brought by the technology disclosed here can be suitably exerted.

Optical use is mentioned as an example of preferable use. More specifically, for example, the adhesive sheet disclosed here can be suitably used as an optical product that can be used for bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the above-mentioned optical members. Adhesive sheet to use.

The aforementioned optical member refers to a member having optical properties (such as polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.). The aforementioned optical member is not particularly limited as long as it is a member having optical properties, and examples thereof include members constituting devices such as display devices (image display devices) and input devices (optical devices) or members used in such devices, such as polarizers Plate, Wavelength Plate, Retardation Plate, Optical Compensation Film, Brightness Enhancement Film, Light Guide Plate, Reflective Film, Antireflective Film, Hard Coating (HC) Film, Shock Absorbing Film, Antifouling Film, Photochromic Film, Dimming Film , transparent conductive film (ITO film), design film, decorative film, surface protection plate, 稜鏡, lens, color filter, transparent substrate, or further components formed by such layers (these are sometimes collectively referred to as " Functional film"), etc. In addition, the above-mentioned "plate" and "film" are defined to include forms such as plate, film, sheet, etc., for example, "polarizing film" is defined to include "polarizing plate" or "polarizer", and " "Light guide plate" is assumed to include "light guide film" or "light guide sheet". In addition, the above-mentioned "polarizing plate" is assumed to include circular polarizing plates.

The above-mentioned display device may, for example, be a liquid crystal display device, an organic EL display device, a micro LED (µLED), a mini LED (mini LED), a PDP, an electronic paper, or the like. Moreover, a touch panel etc. are mentioned as the said input device.

The above-mentioned optical member is not particularly limited, and examples thereof include members made of glass, acrylic resin, polycarbonate, PET, and metal thin films (for example, sheet-like, film-like, and plate-like members). In addition, the "optical member" in this specification is also taken to include a member (design film, decorative film, or surface protection film, etc.) that performs a decorative or protective function while maintaining the visibility of a display device or an input device.

For example, the technology disclosed here can be suitably used to join optical films such as thin films or fluorescent films with one or more functions of light transmission, reflection, diffusion, waveguide, light concentration, and diffraction to other optical members (which can be other optical films). Among them, in the bonding of optical films having at least one of the functions of waveguide, light collection, and diffraction of light, the entirety of the bonding layer should preferably have a high refractive index, and it can be an ideal application target of the technology disclosed here.

The adhesive disclosed here can be suitably used for bonding of optical films such as light guide film, diffusion film, fluorescent film, toner film, tinted film, lenticular film, microlens array film, etc., for example. In these applications, reduction in thickness or improvement in light extraction efficiency is required from the viewpoint of the trend toward miniaturization of optical components or enhancement of performance. The adhesive disclosed here can be suitably utilized as an adhesive that meets the above-mentioned requirements. More specifically, for example, when bonding a light guide film or a diffusion film, adjusting the refractive index (for example, increasing the refractive index) of the adhesive layer as the bonding layer can contribute to thinning. The bonding of fluorescent films can improve the light extraction efficiency (also known as luminous efficiency) by properly adjusting the refractive index difference between the fluorescent luminous body and the adhesive. For the bonding of toning films, by properly adjusting the refractive index of the adhesive to reduce the refractive index difference with the toning pigment, the scattering components can be reduced, which contributes to the improvement of light transmittance. During the bonding of lamina sheets, lenticular films, microlens array films, etc., by properly adjusting the refractive index of the adhesive to control the diffraction of light, it can help to improve the brightness and/or viewing angle.

The adhesive sheet disclosed here can be suitably used in a state where it is attached to a high-refractive-index adherend (it may be a high-refractive-index layer or member, etc.), and can suppress interface reflection with the above-mentioned adherend. The adhesive sheet that can be used in the above-mentioned aspect preferably has a small refractive index difference with the adherend and high adhesion at the interface with the adherend as described above. Also, from the viewpoint of improving the uniformity of the appearance, the uniformity of the thickness of the adhesive layer should be high, for example, the surface smoothness of the adhesive surface should be high. When the thickness of the adherend with a high refractive index is small (for example, 5µm or less, 4µm or less, or 2µm or less), from the viewpoint of suppressing coloring or color unevenness caused by the interference of reflected light, the reflection at the interface is suppressed One thing is very meaningful. As an example of the usage, the following aspect can be mentioned: In a polarizing plate with a retardation layer provided with a polarizer, a first retardation layer, and a second retardation layer in this order, the polarizer and the polarizer can be used. The bonding of the first retardation layer and/or the bonding of the first retardation layer and the second retardation layer.

Also, since the adhesive sheet disclosed here is suitable for increasing the refractive index, it can be suitably used in a state where it is attached to a light-emitting layer such as an optical semiconductor (for example, a high-refraction light-emitting layer mainly composed of an inorganic material). . By narrowing the refractive index difference between the light-emitting layer and the adhesive layer, the reflection at their interfaces can be suppressed, and the light extraction efficiency can be improved. The adhesive sheet that can be used in the above-mentioned aspect preferably has an adhesive layer with a high refractive index. Also, from the viewpoint of improving brightness, the adhesive sheet is preferably low-colored. It is also advantageous from the viewpoint of suppressing unintentional coloring by the adhesive sheet.

In addition, in this specification, a self-luminous element means a light-emitting element whose luminance can be controlled by the value of the current flowing therethrough. The self-luminous element may be configured as a single body or as an aggregate. Specific examples of self-luminous elements include light-emitting diodes (LEDs) and organic ELs, but are not limited thereto. In addition, in this specification, a light-emitting device means a device including the above-mentioned self-light-emitting element as a constituent element. Examples of the above-mentioned light-emitting devices also include light source module devices used as lighting (such as planar light-emitting body modules) or display devices formed with pixels, but are not limited thereto.

The adhesive disclosed here can be suitably used as a covering lens surface in microlenses used as components of cameras or light-emitting devices and other lens components (for example, microlenses constituting a microlens array film or lens components such as microlenses for cameras). The coating layer, the bonding layer of a member facing the lens surface (for example, a member having a surface shape corresponding to the lens surface), a filling layer filled between the lens surface and the member, etc. are used. The adhesive disclosed here is suitable for high refractive index, so even if it is a lens with high refractive index (such as a lens made of high refractive index resin, or a lens with a surface layer made of high refractive index resin), it can still be used. Reduce the refractive index difference with the lens. This is advantageous from the viewpoint of thinning the above-mentioned lens and products including the lens, and can also contribute to suppression of aberrations and improvement of Abbe's number. The adhesive disclosed here can also be used as a lens resin itself, for example, in the form of being filled in a concave portion or a void of an appropriate transparent member.

There is no particular limitation on the aspect of using the adhesive sheet disclosed here to bond optical components, for example, the following aspects can be used: (1) the aspect of bonding optical components to each other through the adhesive sheet disclosed here; or (2) The form of attaching the optical member to a member other than the optical member through the adhesive sheet disclosed here; it may also be (3) that the adhesive sheet disclosed here includes the form of the optical member and the adhesive sheet is attached to the optical member Or the form of components other than optical components. In addition, in the aspect of (3) above, the adhesive sheet in the form of including an optical member may be an adhesive sheet in which the support is an optical member (such as an optical film), for example. An adhesive sheet comprising an optical member as a support as described above can also be regarded as an adhesive optical member (for example, an adhesive optical film). In addition, when the adhesive sheet disclosed here is a type of adhesive sheet having a support and the above-mentioned functional film is used as the support, the adhesive sheet disclosed here can also be regarded as having the above-mentioned adhesive sheet on at least one side of the functional film. The "adhesive functional film" of the adhesive layer disclosed.

From the above, according to the technique disclosed here, there is provided a laminate comprising the adhesive sheet disclosed herein and a member attached with the adhesive sheet. The member to which the adhesive sheet can be attached may have the above-mentioned refractive index of the adherend material. Moreover, the difference (refractive index difference) between the refractive index of an adhesive sheet and a member may be the refractive index difference of the said to-be-adhered body and an adhesive sheet. As for the members constituting the laminate, the above-mentioned members, materials, and adherends have been described, so the description will not be repeated.

As can be understood from the above description and the following examples, the matters disclosed in this specification include the following matters. [1] An adhesive composition comprising an acrylic polymer and a plasticizer; The monomer component constituting the aforementioned acrylic polymer contains an aromatic ring-containing monomer (A1); The aforementioned plasticizer is a compound having two or more double bond-containing rings and is liquid at 30°C. [2] The adhesive composition according to the above [1], wherein the compound is a liquid compound at 20°C. [3] The adhesive composition according to the above [1] or [2], wherein the plasticizer is contained in more than 15 parts by weight relative to 100 parts by weight of the acrylic polymer. [4] The adhesive composition according to any one of the above [1] to [3], wherein the plasticizer is contained in more than 30 parts by weight relative to 100 parts by weight of the acrylic polymer. [5] The adhesive composition according to any one of [1] to [4] above, wherein the plasticizer has at least one ring selected from aromatic rings and heterocyclic rings as the double bond-containing ring. [6] The adhesive composition according to any one of the above [1] to [5], wherein the plasticizer has a first double bond-containing ring and a second double bond-containing ring, and the first double bond-containing ring The bonded ring is connected to the aforementioned second double bond-containing ring through a linking group having 1 to 5 atoms. [7] The adhesive composition according to any one of the above-mentioned [1]-[6], wherein the molecular weight of the plasticizer is in the range of 100-2000. [8] The adhesive composition according to any one of the above-mentioned [1] to [7], wherein the monomer component constituting the aforementioned acrylic polymer further contains a monomer (A2) in addition to the aforementioned aromatic ring-containing monomer (A1). ), the monomer (A2) has at least one of a hydroxyl group and a carboxyl group. [9] The adhesive composition according to any one of [1] to [8] above, wherein the content of the aromatic ring-containing monomer (A1) in the monomer components is 60% by weight or more. [10] The adhesive composition according to any one of [1] to [9] above, wherein at least 50% by weight of the aromatic ring-containing monomer (A1) is a homopolymer and the glass transition temperature is 10°C or lower. monomer.

[11] An adhesive comprising the adhesive composition according to any one of [1] to [9] above. [12] The adhesive according to the above [11], which has a refractive index of 1.55 or more and a storage elastic modulus G'(0°C) at 0°C in the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. [13] The adhesive according to the above [11] or [12], which has a glass transition temperature in the range of -50°C to 0°C. [14] The adhesive according to any one of the above [11] to [13], wherein the ratio of the storage elastic modulus G'(0°C) to the storage elastic modulus G'(80°C) at 80°C (G'(0°C)/G'(80°C)) is in the range of 1~1000. [15] The adhesive according to any one of the above [11] to [14], wherein the storage elastic modulus G'(-10°C) at -10°C is relative to the storage elastic modulus G'( 80°C) ratio (G'(-10°C)/G'(80°C)) is in the range of 1~1000.

[16] An adhesive sheet comprising an adhesive layer formed of the adhesive composition according to any one of [1] to [10] above. [17] An adhesive sheet comprising an adhesive layer composed of the adhesive according to any one of [11] to [15] above. [18] The adhesive sheet according to the above [16] or [17], wherein the thickness of the adhesive layer is in the range of 5 to 75 µm. [19] The adhesive sheet according to any one of the above [16] to [18], wherein the storage elastic modulus G'(0°C) [Pa] of the adhesive at 0°C and the thickness T [µm of the adhesive layer ] product (G'(0°C)×T) is in the range of 5.0×10 ⁴ ~5.0×10 ⁷ . [20] The adhesive sheet according to any one of [16] to [19] above, which has a total light transmittance of 85% or more. [21] The adhesive sheet according to any one of [16] to [20] above, which has a haze value of 3% or less. [22] The adhesive sheet according to any one of the above [16] to [21], which has a peel strength to a glass plate of 0.1 N/25mm or more.

Example Various embodiments related to the present invention will be described below, but those shown in the specific examples are not intended to limit the present invention. In addition, in the following description, "part" and "%" which show the usage-amount or content are weight basis unless otherwise specified.

<Example 1> (Preparation of Acrylic Polymer Solution) In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler, m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "LIGHT ACRYLATE POB-A") was charged as a monomer component. ", Refractive Index: 1.566, Tg of Homopolymer: -35°C; hereinafter expressed as "POB-A") 95 parts and 4-hydroxybutyl acrylate (4HBA) 5 parts, as a polymerization initiator 2, 0.2 parts of 2'-azobisisobutyronitrile, and 150 parts of ethyl acetate as a polymerization solvent, introduce nitrogen gas while stirring slowly, and keep the liquid temperature in the flask at around 60°C for 6 hours of polymerization reaction to prepare A solution (40%) of acrylic polymer P1 was prepared. The Mw of the acrylic polymer P1 was 500,000.

(Preparation of Adhesive Composition) The solution (40%) of the above-mentioned acrylic polymer P1 was diluted to 20% with ethyl acetate, and 500 parts of the solution (100 parts of non-volatile components) was added as a cross-linking agent. 10 parts of 1% ethyl acetate solution (0.1 part of non-volatile content) of polyisocyanate body (manufactured by Tosoh, trade name "Coronate HX", trifunctional isocyanate compound), 2 parts of acetylacetone as a crosslinking retarder, as 1 part of a 1% ethyl acetate solution of iron (III) acetylacetonate as a crosslinking catalyst (0.01 part of non-volatile components) was stirred and mixed to prepare the acrylic adhesive composition of this example.

(Production of Adhesive Sheet) Coat the acrylic adhesive composition prepared above on the polysiloxane-treated surface of polyethylene terephthalate (PET) film R1 (thickness 50 μm) treated with polysiloxane on one side, at 130 Heat at ℃ for 2 minutes to form an adhesive layer with a thickness of 20µm. Next, the silicone-treated side of the PET film R2 (thickness 25 μm) treated with silicone on one side was attached to the surface of the above-mentioned adhesive layer. A substrate-less double-sided adhesive sheet composed of the above-mentioned adhesive layer was obtained in the above-mentioned manner. Both sides of this adhesive sheet were protected by PET film (release liner) R1, R2.

<Example 2> (Preparation of Acrylic Polymer Solution) In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler, benzyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #160", refractive index: 1.519, Tg of homopolymer: 6°C; hereinafter referred to as "BZA") 99 parts and 1 part of 4HBA, 0.2 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator, and ethyl acetate as a polymerization solvent 100 parts, nitrogen gas was introduced while slowly stirring, and the liquid temperature in the flask was kept at around 60°C to carry out polymerization reaction for 6 hours to prepare a solution of acrylic polymer P2 (polymer concentration: 50%). The Mw of the acrylic polymer P2 was 1 million.

(Preparation of Adhesive Composition) Dilute the above-mentioned acrylic polymer P2 solution (polymer concentration 50%) with ethyl acetate to a polymer concentration of 30%, and add hexamethasone as a crosslinking agent to 334 parts of the solution (100 parts of non-volatile components). 10 parts of a 1% ethyl acetate solution (0.1 part of non-volatile components) of a trimeric isocyanate body of methyl diisocyanate (manufactured by Tosoh, trade name "Coronate HX", a trifunctional isocyanate compound), ethyl alcohol as a crosslinking retarder 2 parts of acetylacetone, 1 part of 1% ethyl acetate solution of iron (III) acetylacetonate as a cross-linking catalyst (0.01 part of non-volatile components) were stirred and mixed to prepare the acrylic adhesive composition of this example.

(Production of Adhesive Sheet) Using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as in Example 1.

＜Example 3~Example 5＞ In the preparation of the acrylic adhesive composition in Example 2, POB-A (Kyoeisha Chemical Co., Ltd. Made by the company, trade name "LIGHT ACRYLATE POB-A", m-phenoxybenzyl acrylate, refractive index: 1.566, liquid at 20°C) 30 parts (Example 3), 45 parts (Example 4) or 60 parts (Example 5), except for this, the acrylic adhesive composition of each example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 2. Except for using the obtained acrylic adhesive compositions, in the same manner as the adhesive sheet in Example 1, the adhesive sheets of each example (double-sided adhesive sheets without substrates composed of adhesive layers) were produced. .

<Example 6> The composition of the monomer component was changed to phenoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #192", refractive index: 1.517, Tg of homopolymer: 2°C; hereinafter referred to as "PEA") Except for 99 parts and 1 part of 4HBA, the solution of acrylic polymer P3 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2. The Mw of the acrylic polymer P3 was 1 million. Except for using the solution of acrylic polymer P3 to replace the solution of acrylic polymer P2, the acrylic adhesive composition of this example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 2, and Using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as in Example 1.

<Example 7> In the preparation of the acrylic adhesive composition in Example 3, the solution of acrylic polymer P3 was used instead of the solution of acrylic polymer P2. For the rest, prepare the acrylic adhesive composition of this example in the same manner as the preparation of the acrylic adhesive composition in Example 3, and use the obtained acrylic adhesive composition to make this acrylic adhesive composition in the same manner as in Example 1. An example of an adhesive sheet (a double-sided adhesive sheet without a base material consisting of an adhesive layer).

<Example 8> A solution of acrylic polymer P4 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer components was changed to 99 parts of BZA and 1 part of acrylic acid (AA). The Mw of the acrylic polymer P4 was 1 million. Dilute the above acrylic polymer P4 solution (polymer concentration 50%) with ethyl acetate to a polymer concentration of 30%, and add epoxy as a crosslinking agent to 334 parts of the solution (100 parts of non-volatile components). A cross-linking agent (manufactured by MITSUBISHI GAS CHEMICAL, trade name "TETRAD C", 0.1 part of 1,3-bis(N,N-diecidylaminomethyl)cyclohexane) was stirred and mixed to prepare The acrylic adhesive composition of this example. Except for using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as that of the adhesive sheet in Example 1.

＜Example 9~Example 12＞ In the preparation of the acrylic adhesive composition in Example 8, 60 parts of POB-A was further added as plasticizer A1 (Example 9 ), 60 parts of 4,4'-oxybis[(methoxymethyl)benzene] (manufactured by Tokyo Chemical Industry Co., Ltd., refractive index: 1.56, liquid at 20°C) as plasticizer A2 (Example 10 ), 60 parts of 3-phenoxybenzyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd., refractive index: 1.591, liquid at 20°C; hereinafter sometimes referred to as "POB-AL") as plasticizer A3 (Example 11 ), or 60 parts of 1-naphthyl ethyl ketone (manufactured by Tokyo Chemical Industry Co., Ltd., refractive index: 1.63, liquid at 20 ° C) as plasticizer A4 (Example 12), in addition to the same as in Example 8 Preparation of Acrylic Adhesive Composition The same method was used to prepare the acrylic adhesive composition of each example. Except for using the obtained acrylic adhesive compositions, in the same manner as the adhesive sheet in Example 1, the adhesive sheets of each example (double-sided adhesive sheets without substrates composed of adhesive layers) were produced. .

<Example 13> In addition to changing the composition of the monomer components to 90 parts of BZA, 9 parts of n-butyl acrylate (BA) and 1 part of AA, in the same manner as the preparation of the acrylic polymer solution in Example 2, an acrylic polymer solution was prepared. Solution of substance P5. The Mw of the acrylic polymer P5 was 1 million. The solution of the above-mentioned acrylic polymer P5 (polymer concentration 50%) was diluted with ethyl acetate to a polymer concentration of 30%, and the above-mentioned plasticizer A3 (POB -AL) 60 parts and 0.1 part of the above-mentioned epoxy-based crosslinking agent were stirred and mixed to prepare the acrylic adhesive composition of this example. Except for using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as that of the adhesive sheet in Example 1.

<Example 14> In the preparation of the acrylic adhesive composition in Example 13, 15 parts of biscresol (Osaka Gas Chemicals Co., Ltd., 9,9-bis(4-hydroxy-3-methylphenyl) fluorene, refractive index: 1.68; hereinafter sometimes referred to as "BCF") as an additive, in addition to In the same manner as the preparation of the acrylic adhesive composition in Example 13, the acrylic adhesive composition of this example was prepared. The above additives were added as 10% ethyl acetate solution. Except for using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as that of the adhesive sheet in Example 1.

＜Example 15~Example 16＞ Except changing the composition of the monomer components to 90 parts of BZA, 9 parts of 2-ethylhexyl acrylate (2EHA) and 1 part of AA, acrylic acid was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2. It is a solution of polymer P6. The Mw of the acrylic polymer P6 was 1 million. In the preparation of the acrylic adhesive composition in Examples 13 to 14, the solution of acrylic polymer P6 was used instead of the solution of acrylic polymer P5. For the rest, prepare the acrylic adhesive compositions of Examples 15 to 16 in the same manner as the preparation of the acrylic adhesive compositions in Examples 13 to 14, and use the obtained acrylic adhesive compositions to Adhesive sheets (double-sided adhesive sheets without base material composed of an adhesive layer) of each example were prepared in the same manner as in Example 1.

＜Example 17~Example 18＞ A solution of acrylic polymer P7 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer components was changed to 80 parts of BZA, 19 parts of BA, and 1 part of AA. Also, a solution of acrylic polymer P8 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer components was changed to 66 parts of BZA, 33 parts of BA, and 1 part of AA. The Mw of the acrylic polymers P7 and P8 was 1 million. In the preparation of the acrylic adhesive composition in Example 13, the solution of the acrylic polymer P7 (Example 17) or P8 (Example 18) was used instead of the solution of the acrylic polymer P5. For the rest, prepare the acrylic adhesive compositions of Examples 17-18 in the same manner as the preparation of the acrylic adhesive composition in Example 13, and use the obtained acrylic adhesive compositions to compare with Example 1. Adhesive sheets (double-sided adhesive sheets without base material composed of an adhesive layer) of each example were produced in the same manner.

<Example 19> A solution of acrylic polymer P9 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer components was changed to 85 parts of POB-A, 14 parts of BA, and 1 part of AA. The Mw of the acrylic polymer P9 was 1 million. In the preparation of the acrylic adhesive composition in Example 13, the solution of acrylic polymer P9 was used instead of the solution of acrylic polymer P5. For the rest, prepare the acrylic adhesive composition of this example in the same manner as the preparation of the acrylic adhesive composition in Example 13, and use the obtained acrylic adhesive composition to prepare this acrylic adhesive composition in the same manner as in Example 1. An example of an adhesive sheet (a double-sided adhesive sheet without a base material consisting of an adhesive layer).

<Example 20> In the preparation of the acrylic adhesive composition in Example 19, 23 parts of 6-acryloxymethylbinaphtho was further added to 100 parts of non-volatile components contained in the solution of acrylic polymer P9. Thiophene (trade name "6MDNTA" manufactured by SUGAI Chemical Industry Co., Ltd., dinaphthothiophene-6-methacrylate body, refractive index 1.75; hereinafter may be described as "6MDNTA") was used as an additive. For the rest, prepare the acrylic adhesive composition of this example in the same manner as the preparation of the acrylic adhesive composition in Example 19, and use the obtained acrylic adhesive composition to produce this acrylic adhesive composition in the same manner as in Example 1. An example of an adhesive sheet (a double-sided adhesive sheet without a base material consisting of an adhesive layer). The above additives were added as 10% ethyl acetate solution.

＜Example 21~Example 22＞ A solution of acrylic polymer P10 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer components was changed to 80 parts of POB-A, 19 parts of BA, and 1 part of AA. The Mw of the acrylic polymer P10 was 1 million. In the preparation of the acrylic adhesive composition in Example 13, the solution of acrylic polymer P10 was used instead of the solution of acrylic polymer P5. For the rest, the acrylic adhesive composition of Example 21 was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 13. Also, in the preparation of the acrylic adhesive composition of Example 21, the amount of the epoxy-based crosslinking agent used was changed to 0.5 parts with respect to 100 parts of non-volatile components contained in the solution of the acrylic polymer P10. , prepared the acrylic adhesive composition of Example 22. Using each of the obtained acrylic adhesive compositions, an adhesive sheet (double-sided adhesive sheet without a base material composed of an adhesive layer) of each example was produced in the same manner as in Example 1.

<Example 23> In addition to changing the composition of the monomer components to 99 parts of POB-A and 2-acryloxyethyl-succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., trade name "HOA-MS(N)", hereinafter expressed as "HOA -MS"), in the same manner as the preparation of the acrylic polymer solution in Example 1, a solution of acrylic polymer P11 was prepared. The Mw of the acrylic polymer P11 was 500,000. The solution of the above-mentioned acrylic polymer P11 was diluted with ethyl acetate to a polymer concentration of 30%, and 40 parts of the above-mentioned plasticizer A3 (POB-AL) was added to 334 parts of the solution (100 parts of non-volatile components), as Plasticizer A5 trimethylpentaphenyltrisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "HIVAC F-5", molecular weight: 546, refractive index: 1.575, liquid at 20°C) 20 parts and 0.3 parts of the above-mentioned epoxy-based cross-linking agent (hereinafter also referred to as cross-linking agent C1) were stirred and mixed to prepare the acrylic adhesive composition of this example. Except for using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as that of the adhesive sheet in Example 1.

<Example 24> Except changing the composition of monomer components to 95 parts of POB-A, 2 parts of lauryl acrylate (LA), 2 parts of 2EHA and 1 part of 4HBA, prepare in the same way as the preparation of the acrylic polymer solution in Example 23 A solution of acrylic polymer P12 was produced. The Mw of the acrylic polymer P12 was 500,000. Dilute the solution of the above-mentioned acrylic polymer P12 with ethyl acetate to a polymer concentration of 30%, and add 40 parts of the above-mentioned plasticizer A3 (POB-AL) and the above-mentioned 20 parts of plasticizer A5 (HIVAC F-5), non-cyclic 2-functional isocyanate-based cross-linking agent as cross-linking agent C2 (manufactured by Tosoh Company, trade name "Coronate 2770", hexamethylene diisocyanate (HDI ) alloformate body) 0.3 parts, 2 parts of acetylacetone as a crosslinking retarder, 1 part of 1% ethyl acetate solution of iron (III) acetylacetonate as a crosslinking catalyst (0.01 part of non-volatile components ) and stirred to prepare the acrylic adhesive composition of this example. Except for using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as that of the adhesive sheet in Example 1.

<Example 25> A solution of acrylic polymer P13 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 23, except that the composition of the monomer components was changed to 90 parts of POB-A, 9 parts of 2EHA and 1 part of 4HBA. The Mw of the acrylic polymer P13 was 500,000. The solution of the above-mentioned acrylic polymer P13 was diluted with ethyl acetate to a polymer concentration of 30%, and 80 parts of the above-mentioned plasticizer A5 (HIVAC F-5) were added to 334 parts of the solution (100 parts of non-volatile components), 0.5 parts of the above-mentioned crosslinking agent C2 (Coronate 2770), 2 parts of acetylacetone as a crosslinking retarder, 1 part of 1% ethyl acetate solution of iron (III) acetylacetonate as a crosslinking catalyst (non-volatile 0.01 parts) and stirred and mixed to prepare the acrylic adhesive composition of this example. Except for using the obtained acrylic adhesive composition, the adhesive sheet of this example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as that of the adhesive sheet in Example 1.

＜Example 26~28＞ Except for changing the composition of the monomer components as shown in Table 3, the solutions of acrylic polymers P14 and P15 were prepared in the same manner as the preparation of the acrylic polymer solution in Example 23. The Mw of the acrylic polymers P14 and P15 were 500,000, respectively. Dilute the solution of the above-mentioned acrylic polymer P11, P14 or P15 with ethyl acetate to a polymer concentration of 30%, and add the above-mentioned plasticizer A3 to 334 parts of the solution (100 parts of non-volatile components) as shown in Table 3 , the above-mentioned crosslinking agent C1 or C2, and for examples 26 and 28, further add 2 parts of acetylacetone as a crosslinking retarder, 1% ethyl acetate solution of iron acetylacetonate (III) as a crosslinking catalyst 1 part (0.01 part of non-volatile components) and stirred and mixed to prepare the acrylic adhesive composition of each example. Except for using the obtained acrylic adhesive composition, the adhesive sheets of each example (double-sided adhesive sheet without base material composed of an adhesive layer) were produced in the same manner as that of the adhesive sheet in Example 1.

＜Evaluation method＞ (refractive index) For the adhesive layer (double-sided adhesive sheet without base material) of each example, use an Abbe refractometer (manufactured by ATAGO CO., LTD., type "DR-M4") at a measurement wavelength of 589nm and a measurement temperature of 25°C. Measure the refractive index under the conditions.

(Storage elastic modulus G' and glass transition temperature) The adhesive layer of each example was made into a thickness of about 1.5mm, and it was used as a sample for measurement. Using "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific, dynamic viscoelasticity was measured under the following conditions. From the measurement results, the storage elastic modulus G'[Pa] of the adhesive at various temperatures (-20°C, -10°C, 0°C and 80°C) was obtained. In addition, the temperature corresponding to the peak temperature of the loss tangent tanδ (loss elastic modulus G"/storage elastic modulus G') in the above-mentioned dynamic viscoelasticity measurement was taken as the glass transition temperature (Tg) [°C] of the adhesive. [measurement conditions] Deformation Mode: Twist Measurement frequency: 1Hz Temperature range: -50℃~150℃ Heating rate: 5°C/min Shape: parallel plate 7.9mmφ

(total light transmittance and haze) Using the test piece with the adhesive layer of each example attached to the alkali-free glass (thickness 0.8~1.0mm, total light transmittance 92%, haze 0.4%), use a haze meter (manufactured by Murakami Color Technology Research Institute) "HM-150"), the total light transmittance and haze of the above-mentioned test piece were measured in a measurement environment of 23°C. The values obtained by subtracting the total light transmittance and haze of the above-mentioned alkali-free glass from the measured values were taken as the total light transmittance [%] and haze [%] of the adhesive (layer). Regarding the base-less adhesive sheet composed of the above adhesive layer, the total light transmittance [%] and haze [%] of the adhesive layer will become the total light transmittance [%] and haze [%] of the adhesive sheet .

(Peel strength against glass plate) Under the measurement environment of 23°C and 50%RH, the release liner was peeled off from one side of the adhesive sheet, and a PET film with a thickness of 50µm was attached as a substrate, and then cut into a size of 25mm in width and 100mm in length to make a test piece. The release liner on the other side was peeled off from the test piece, and a 2 kg roller was pressed back and forth on the surface of an alkali glass plate (manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.35mm, blue plate frosted product) as an adherend. After leaving it in this environment for 30 minutes, use a universal tensile and compression testing machine to measure the peel strength (adhesion force) [N /25mm]. The universal tensile and compression testing machine is "tensile and compression testing machine, TG-1kN" manufactured by Minebea Corporation. In addition, when it is a single-sided adhesive sheet with a substrate, it cannot be used as a substrate for PET film.

(bending test) The adhesive sheet with release liner of each example was cut into a rectangle of 2 cm x 10 cm to obtain a test piece for measurement. A cylindrical rod of φ4mm is fixed horizontally at a height sufficient for the measurement, and the test piece obtained above is placed on the rod to be deflected. Specifically, the central part of the above-mentioned test piece in the longitudinal direction is covered on the rod so as to form an inverted U shape. Next, fix the two ends below the test piece with a jig (13g), and hang and fix a 60g weight on the jig through a wire with a length of 1cm, and apply a load to the flexure of the test piece. In this state, the test piece was maintained in a predetermined temperature environment (-20°C, -10°C, or 0°C) for 1 minute, and after 1 minute passed, the test piece was removed from the rod. Then, in this temperature environment, the test piece was left still on a horizontal surface so that the convex side of the flexure portion was below, and it was left still for 10 minutes. Measure the time until the end (short side end) of the test piece after standing for 10 minutes touches the horizontal surface. The test was carried out at -20°C, -10°C, and 0°C, respectively, and the softness was evaluated according to the following criteria. E (Excellent): In the bending test under all temperature conditions (-20°C, -10°C and 0°C), the end of the test piece touches the horizontal surface within 10 minutes. G (Good): In the bending test under the temperature conditions of -10°C and 0°C, the end of the test piece touches the horizontal surface within 10 minutes. A (Acceptable): In the bending test at a temperature of 0°C, the end of the test piece touches the horizontal surface within 10 minutes. P (Poor): In the bending test under all temperature conditions, the end of the test piece did not touch the horizontal surface or the adhesive layer was peeled off from the release liner within 10 minutes.

The summary and evaluation results of the adhesives in each example are shown in Tables 1-3.

[Table 1]

[Table 2]

[table 3]

As shown in Tables 1 to 3, Examples 3 to 5, Examples 7, and Examples 9 to 28 use the following adhesive composition. Polymers and compounds that have more than two rings containing double bonds and are liquid at 30°C are used as plasticizers, so Examples 3~5, Examples 7, and Examples 9~28 can form a plasticizer with a refractive index of 1.55 or more and a storage elastic modulus. Adhesives with a number G'(0°C) below 1.0×10 ⁶ Pa can form adhesives with high refractive index and low modulus of elasticity at the same time. The results of the bending test of the adhesive sheets of these examples are all acceptable (above A). On the other hand, Examples 1-2, Example 6, and Example 8 are adhesives with a high refractive index successfully formed by using an acrylic polymer containing an aromatic ring-containing monomer (A1) as a monomer unit, but the storage elastic modulus G'(0°C) is greater than 1.0×10 ⁶ Pa, rather than having a low modulus of elasticity. The result of the bending test of the adhesive sheet of these examples was unacceptable (P).

More specifically, from the results of Examples 3 to 5, it can be seen that by increasing the amount of the above-mentioned plasticizer, the storage elastic modulus G' at each temperature can be reduced while maintaining a high refractive index, and a more stable plastic can be produced. Adhesive with low modulus of elasticity. In addition, Examples 9 to 12 are examples in which the type of plasticizer is changed. From these results, it can be seen that by using a compound having two or more double bond-containing rings and being liquid at 30°C as the plasticizer, both High refractive index and low elastic modulus. Examples 13-16 and Example 20 are the research results of additives. It can be known that a higher refractive index can be achieved by using various additives. Also, from the comparison of Example 13 and Example 15, it can be seen that by selecting the type of alkyl (meth)acrylate as the monomer component, the adhesive can be lowered in elastic modulus, and at the same time, for example, the storage elastic modulus in the high temperature region can be increased. The adjustment of the number G', etc. Examples 17 to 18 are examples in which the usage ratio of the aromatic ring-containing monomer (A1) is changed. It can be seen that even if the usage amount of the aromatic ring-containing monomer (A1) is limited, a high refractive index can still be maintained. In addition, Examples 17 to 18 have better suppression of the difference in storage elastic modulus G' between the low temperature region and the high temperature region. We speculate that it is caused by the increase of alkyl (meth)acrylate (specifically, BA) as the aromatic ring-containing monomer (A1) decreases. Examples 21-22 are examples where the amount of cross-linking agent is changed. It can be seen that the storage elastic modulus G' can be increased by increasing the amount of cross-linking agent. Examples 23 to 28 are examples of changing the monomer composition of the polymer, the type of plasticizer, the type of crosslinking agent and/or the use ratio of each component. It can be seen that by adjusting the monomer composition of the acrylic polymer, selecting the The type of adhesive, the amount of plasticizer used, etc. are designed to design the composition of the adhesive to maintain a high refractive index, and at the same time adjust the storage elastic modulus of the adhesive to the desired range.

The specific examples of the present invention have been described in detail above, but these are only examples and do not limit the scope of the patent application. The technologies described in the claims include various modifications and changes of the specific examples exemplified above.

1,2,3: Adhesive sheet 10: Support substrate 10A:Side 1 10B: Side 2 21: Adhesive layer, first adhesive layer 21A: Adhesive surface, first adhesive surface 21B: Adhesive surface 22: The second adhesive layer 22A: The second adhesive surface 31,32: Release liner

Fig. 1 is a cross-sectional view schematically showing the structure of an adhesive sheet according to an embodiment. Fig. 2 is a cross-sectional view schematically showing the structure of an adhesive sheet in another embodiment. Fig. 3 is a cross-sectional view schematically showing the structure of an adhesive sheet in another embodiment.

1: Adhesive sheet

21: Adhesive layer

21A, 21B: Adhesive surface

31,32: Release liner

Claims (10)

An adhesive composition comprising an acrylic polymer and a plasticizer; The monomer component constituting the aforementioned acrylic polymer contains an aromatic ring-containing monomer (A1); The aforementioned plasticizer is a compound having two or more double bond-containing rings and is liquid at 30°C. The adhesive composition according to claim 1, wherein the aforementioned compound is a liquid compound at 20°C. The adhesive composition according to claim 1 or 2, wherein the aforementioned plasticizer contains more than 15 parts by weight relative to 100 parts by weight of the aforementioned acrylic polymer. The adhesive composition according to any one of claims 1 to 3, wherein the aforementioned plasticizer contains more than 30 parts by weight relative to 100 parts by weight of the aforementioned acrylic polymer. The adhesive composition according to any one of claims 1 to 4, wherein the plasticizer has at least one ring selected from aromatic rings and heterocyclic rings as the double bond-containing ring. The adhesive composition according to any one of claims 1 to 5, wherein the aforementioned plasticizer has a first double bond-containing ring and a second double bond-containing ring, and the aforementioned first double bond-containing ring and the aforementioned first double bond-containing ring 2. Rings containing double bonds are linked via linking groups with 1 to 5 atoms. The adhesive composition according to any one of claims 1 to 6, wherein the molecular weight of the aforementioned plasticizer is in the range of 100-2000. The adhesive composition according to any one of claims 1 to 7, wherein the monomer component constituting the aforementioned acrylic polymer also contains a monomer (A2) in addition to the aforementioned aromatic ring-containing monomer (A1), the monomer ( A2) It has at least one of a hydroxyl group and a carboxyl group. The adhesive composition according to any one of claims 1 to 8, wherein the content of the aromatic ring-containing monomer (A1) in the monomer components is 60% by weight or more. An adhesive sheet comprising an adhesive layer formed of the adhesive composition according to any one of claims 1 to 9.

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