TW202346506A - Adhesive composition and adhesive to provide an adhesive composition that can form an adhesive with high refractive index, improved flexibility, and stability of improved properties - Google Patents

Abstract

A subject of the present invention is to provide an adhesive composition that can form an adhesive with high refractive index, improved flexibility, and stability of improved properties. The solution is to provide an adhesive composition containing acrylic polymer and plasticizer. The monomer component constituting the aforementioned acrylic polymer contains an aromatic ring-containing monomer (A1). Furthermore, the aforementioned plasticizer has two or more rings containing double bonds, and the amount of transforming to the gas phase at 130 DEG C is less than 10%.

Description

Adhesive compositions and adhesives

The present invention relates to adhesive compositions and adhesives.

Generally speaking, adhesives (also called pressure-sensitive adhesives, the same applies below) are in the state of a soft solid (viscoelastic body) in a temperature range near room temperature, and have the ability to easily adhere to the adherend through pressure. nature. Taking advantage of this property, adhesives are widely used in various industrial fields ranging from home appliances to automobiles, various machinery, electrical equipment, and electronic equipment for the purpose of joining, fixing, and protecting. An example of the use of the adhesive is its use in joining polarizing films, retardation films, cover window members, various other light-transmissive members, and other members in display devices such as liquid crystal displays and organic EL displays. Technical documents related to adhesives for optical components include Patent Documents 1 and 2. Prior technical 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 containing (meth)acrylate polymer as the main component and an adhesive obtained by cross-linking the adhesive composition. The (meth)acrylate polymerization The material contains a monomer with a plurality of aromatic rings as a monomer unit; and it is proposed that by using a monomer with a plurality of aromatic rings, the refractive index of the adhesive can be made to be 1.50 or more, preferably 1.51 or more. For example, it is known that some materials that can be adhered to adhesives such as optical components have high refractive index. If a general acrylic adhesive is used to join such high refractive index materials, the difference in refractive index between the two will This causes reflection at the interface. By using an adhesive with a high refractive index as an adhesive for bonding the above-mentioned high-refractive materials, etc., the above-mentioned interface reflection can be prevented or suppressed. In addition, the refractive index of acrylic adhesive is usually around 1.47.

Depending on where it is applied or how it is used, adhesives with good softness can be used appropriately. For example, in recent years, for displays that can be used in organic EL display devices for electronic devices such as smartphones, foldable displays and rollable displays have become practical. Therefore, adhesives used for the above applications must also be compliant and can be bent repeatedly. Improve the softness of the adherend. The adhesive with excellent flexibility also easily conforms to and adheres closely to the surface of curved surfaces such as three-dimensional shapes, making it suitable for electronic devices with curved surfaces. If the adhesive with a high refractive index can improve flexibility, it can also be used in the above-mentioned applications requiring flexibility, which is useful.

However, in the design of adhesives, high refractive index and softness are in a trade-off relationship, and it is difficult to balance both. Specifically, high refractive index materials used for adhesives with high refractive index (monomer components of adhesive polymers, additives for adhesives, etc.) tend to have aromatic rings and have low flexibility, so the use of such high refractive index materials Adhesives formed from refractive index materials tend to have a higher elastic modulus. In addition, adding a plasticizer can be considered as a method to impart flexibility to the adhesive. However, generally speaking, adding a plasticizer will cause the refractive index of the adhesive to decrease, so it is necessary to select a material that can maintain or increase the refractive index of the adhesive. In addition, adhesives containing plasticizers may have characteristics such as changes in refractive index, elastic modulus, etc. due to plasticizer volatilization, deterioration, migration to the surface of the adhesive, etc. There is also concern that the adhesive may be affected by the use environment or factors. Impaired stability due to long-term use. What is more difficult for adhesives containing plasticizers is to have a high refractive index while also stably exhibiting properties such as elastic modulus.

The present invention was created in view of the above situation, and aims to provide an adhesive composition that can form an adhesive with improved characteristics and stability, and the adhesive has a high refractive index and can improve flexibility. Another object of the present invention is to provide an adhesive, which is an adhesive formed from the above-mentioned adhesive composition.

means to solve problems According to this specification, an adhesive composition containing an acrylic polymer and a plasticizer is provided. The monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1). In addition, the aforementioned plasticizer has two or more double bond-containing rings, and the transfer amount into the gas phase at 130°C is 10% or less. 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, since the adhesive composition contains a plasticizer having two or more double bond-containing rings, it has a high refractive index and can provide flexibility to the adhesive. The transfer amount (vaporization amount) of the above-mentioned plasticizer into the gas phase at 130°C is less than 10%. Therefore, the adhesive containing the plasticizer can still perform well even under the use environment or long-term use. Stable characteristics.

In several aspects, the molecular weight of the aforementioned plasticizer is above 350. Plasticizers with large molecular weight are not easy to vaporize. By using a plasticizer having the above molecular weight in an adhesive, an adhesive that exhibits stable characteristics can be easily obtained.

In several aspects, the aforementioned plasticizer contains more than 10 parts by weight relative to 100 parts by weight of the aforementioned acrylic polymer. By including a plasticizer greater than a predetermined amount, the softness of the adhesive can be effectively improved. Furthermore, by using the plasticizer disclosed herein, an adhesive with good stability can be obtained, and therefore more plasticizer can be included than before. This is of great significance in terms of improving the flexibility of the adhesive.

Furthermore, according to this specification, an adhesive formed from any of the adhesive compositions disclosed herein is provided. In other words, according to this specification, an adhesive containing an acrylic polymer and a plasticizer is provided. The monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1). In addition, the aforementioned plasticizer has two or more double bond-containing rings, and the transfer amount into the gas phase at 130°C is 10% or less. The above-mentioned adhesive has a high refractive index and its flexibility is improved by containing a plasticizer. Therefore, it is suitable for applications such as foldable displays that require a high refractive index and flexibility that can withstand repeated bending operations. To join or fix, protect, etc. In addition, because the stability of the elastic modulus and other characteristics of the above-mentioned adhesive has been improved, it can help improve the durability and longevity of the product.

Furthermore, according to this specification, an adhesive containing an acrylic polymer and a plasticizer is provided. The monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1). Furthermore, the aforementioned plasticizer has two or more double bond-containing rings. After the adhesive was kept at 130°C for 1 hour, the amount of the plasticizer in the adhesive was reduced by less than 5%. In the above-mentioned adhesive, the monomer component constituting the acrylic polymer includes an aromatic ring-containing monomer (A1), and the adhesive contains a plasticizer with two or more double-bond-containing rings, so the adhesive has high refractive index and improves softness. Moreover, even if the adhesive is heated under predetermined conditions, the reduction of the plasticizer in the adhesive can still be limited to less than 5%. Therefore, the above-mentioned adhesive has characteristics caused by the plasticizer in response to temperature changes. Changes can be suppressed, so that the adhesive can still exhibit stable properties even under the use environment or long-term use.

Regarding the adhesives in several aspects, the storage elastic modulus G'1 of the adhesive at -20°C after being kept in an environment of 130°C for 1 hour is different from the storage elastic modulus G'1 before being kept in an environment of 130°C for 1 hour. The storage elastic modulus G'0 ratio (G'1/G'0) at -20°C is 50 or less. Even if an adhesive that meets this characteristic is exposed to high temperatures, the change in elastic modulus is still limited to a predetermined range and can exhibit stable characteristics.

The peeling strength of the adhesive to the glass plate in several aspects is above 1.0N/25mm. Even if the adhesive disclosed here contains a plasticizer, it can still exert the stable adhesive force as mentioned above. Therefore, the adhesive can be used in a form such as a sheet or a film, and can adhere well to the adherend.

In several aspects, the adhesive has a total light transmittance of over 85%. Adhesives with such high transparency can be suitably used in applications requiring high light transmittance (for example, optical applications).

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

Preferred embodiments of the present invention will be described below. Matters that are not specifically mentioned in this specification and are necessary for the implementation of the present invention can be understood by those skilled in the art based on the teachings regarding 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 content disclosed in this specification and the technical common sense in this field. In addition, in the following drawings, members and parts that perform the same functions may be described with the same reference numerals, and repeated descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and do not completely accurately represent the dimensions or scale of the products actually provided.

In this specification, the "base polymer" of the adhesive means the main component of the rubbery polymer contained in the adhesive. The above-mentioned rubber-like polymer refers to a polymer that exhibits rubber elasticity in a temperature range near room temperature. In addition, in this specification, "main component" means a component containing more than 50% by weight unless otherwise noted.

In this specification, "acrylic polymer" means a polymer containing the following monomer units as monomer units constituting the polymer: the monomer units are derived from having at least one (methyl) in one molecule Acrylic monomer. Hereinafter, a monomer having at least one (meth)acrylyl group per molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer containing monomer units derived from an acrylic monomer. Typical examples of acrylic polymers include those in which more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of the monomer components constituting the polymer are acrylic monomers.

Moreover, in this specification, "acrylic monomer" means a monomer which has at least 1 (meth)acrylyl group in 1 molecule. Here, "(meth)acrylyl group" means an acrylyl group and a methacrylyl group collectively. Therefore, the concept of acrylic monomer mentioned here can include both monomers with acrylic groups (acrylic monomers) and monomers with methacrylic groups (methacrylic monomers). Likewise, in this specification, "(meth)acrylic acid" refers to acrylic acid and methacrylic acid collectively, and "(meth)acrylate" refers to acrylic acid ester and methacrylic acid ester collectively. The same goes for other similar terms.

＜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 may be, for example, in the following various forms: a solvent-based adhesive composition in which an adhesive-forming component is contained in an organic solvent, or an active energy prepared to form an adhesive by hardening with active energy rays such as ultraviolet rays or radiation. Line-hardening adhesive compositions, water-dispersed adhesive compositions in which the adhesive forming components are dispersed in water, and hot-melt adhesive compositions that form adhesives when applied in a heated and molten state and cooled to near room temperature. Things etc. The technology 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, the effects of the technology disclosed here can be suitably realized.

The adhesive composition disclosed here contains an aromatic ring-containing monomer (A1) as a monomer component constituting the acrylic polymer. Here, the so-called "monomer component constituting the acrylic polymer" in this specification means whether it is included in the adhesive composition in the form of a preformed polymer (which may be an oligomer) or in the form of an unformed polymer. The forms of polymerized monomers included in the adhesive composition are monomers that constitute the repeating units 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 adhesive composition in any form of polymer, non-polymer, or partial polymer. From the viewpoint of ease of preparation of the adhesive composition, etc., in some aspects, 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. adhesive composition.

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

Examples of the ethylenically unsaturated group include (meth)acrylyl group, vinyl group, (meth)allyl group, and the like. From the viewpoint of polymerization reactivity, a (meth)acrylyl group is preferable, and from the viewpoint of flexibility or adhesiveness, an acrylyl group is more preferable. From the viewpoint of suppressing a decrease in the flexibility of the adhesive, a compound having one ethylenically unsaturated group in one molecule (i.e., a monofunctional monomer) can be suitably used as the monomer (A1).

The number of aromatic rings contained in one molecule of the compound that can be used as the monomer (A1) may be 1, or 2 or more. The upper limit of the number of aromatic rings is not particularly limited, but may be 16 or less, for example. In some aspects, from the viewpoint of ease of preparation of the adhesive composition or transparency of the adhesive, the number of the aromatic rings may be, for example, 12 or less, preferably 8 or less, and more preferably 6 or less. It may be 5 or less, it may be 4 or less, it may be 3 or less, or it may be 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 benzene ring constituting a part of the biphenyl structure or the fluorine structure); naphthalene ring, indene ring, azulene ring, anthracene ring, phenanthrene ring Carbocyclic rings such as condensed rings of rings; it can also be pyridine ring, pyrimidine ring, pyridine ring, pyridine ring, tri-pyridine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, ethazole ring, isotriazole ring Heterocycles such as azole ring, thiazole ring, thiophene ring, etc. The heteroatoms contained as ring constituent atoms in the heterocyclic ring may be, for example, one or two or more types selected from the group consisting of nitrogen, sulfur, and oxygen. In several aspects, the heteroatoms constituting the heterocyclic ring may be one or both of nitrogen and sulfur. The monomer (A1) may have a structure in which one or two or more carbocyclic rings and one or two or more heterocyclic rings are condensed, such as a dinaphthothiophene structure.

The above-mentioned aromatic ring (preferably a carbocyclic ring) may have 1 or more substituents on the atoms constituting the ring, or may have no substituents. When there is a substituent, examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, and a propylene oxide group. Oxygen groups, etc., but are not limited by these. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In several aspects, the above-mentioned aromatic ring may be an aromatic ring without substituents on the ring constituent atoms, or may be an aromatic ring with alkyl groups, alkoxy groups and halogen atoms (such as bromine) on the ring constituent atoms. Atom) is an aromatic ring consisting of 1 or more substituents in the group. Furthermore, when the aromatic ring of the monomer (A1) has a substituent on the ring constituting atoms, 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 through a linking group. The above-mentioned linking group may be, for example, one or two selected from the group consisting of an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, and an alkoxyphenyl group. Groups with one or more structures in which the above hydrogen atoms are replaced by hydroxyl groups (such as hydroxyalkylene group), oxygen group (-O- group), thiooxy group (-S- group), etc. . In several aspects, an aromatic ring-containing monomer with a structure in which an aromatic ring and an ethylenically unsaturated group are directly bonded can be suitably used, or a monomer selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly(oxyalkylene group) can be suitably used. Aromatic ring-containing monomer in a structure that is bonded by a linking group composed of a group). The number of carbon atoms of the above-mentioned alkylene group and the above-mentioned oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. The repeat number of the oxyalkylene units in the above poly(oxyalkylene) group may be, for example, 2 to 3.

Examples of compounds that can be suitably used as the monomer (A1) include aromatic ring-containing (meth)acrylate 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.

Among several ideal aspects, a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be used as the monomer (A1) because a high degree of high refractive index-increasing effect 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; The above monomers with a structure in which non-condensed aromatic rings are directly chemically bonded (that is, without other atoms), monomers with a condensed aromatic ring structure, monomers with a fluorine structure, monomers with a dinaphthothiophene structure, Monomers of dibenzothiophene structure, etc. Among them, a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group (for example, m-phenoxybenzyl (meth)acrylate to be described later) can be suitably used. The monomer containing a plurality of aromatic rings can be used individually by 1 type or in combination of 2 or more types.

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

The above-mentioned monomer of a structure in which two or more non-condensed aromatic rings are directly chemically bonded can be, for example, (meth)acrylate containing a biphenyl structure, (meth)acrylate containing a triphenyl structure, or biphenyl containing a vinyl group. wait. Specific examples include o-phenylphenol (meth)acrylate, biphenylmethyl (meth)acrylate, and the like.

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

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

Examples of the monomer having a dinaphthothiophene structure include (meth)acrylyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, (meth)allyl group-containing dinaphthothiophene, and the like. Specific examples include: (meth)acryloxymethyldinaphthothiophene (for example, CH ₂ CH(R ¹ )C(O)OCH ₂ - is bonded to the 5- or 6-position of the dinaphthothiophene ring Compounds with the structure; here, R ¹ is a hydrogen atom or a methyl group), (meth)acryloxyethyl dinaphthothiophene (for example, CH is bonded at the 5- or 6-position of the dinaphthothiophene ring A compound with the structure of ₂ CH(R ¹ )C(O)OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ -; here, R ¹ is a hydrogen atom or methyl group) , Vinyl dinaphthothiophene (for example, a compound with a vinyl group bonded to the 5- or 6-position of the naphthothiophene ring), (meth)allyloxy dinaphthothiophene, etc. In addition, a monomer having a dinaphthothiophene structure is also included in the concept of a monomer having a condensed aromatic ring structure by including a naphthalene structure and a structure having a thiophene ring condensed with two naphthalene structures. .

Examples of the above-mentioned monomer having a dibenzothiophene structure include (meth)acrylyl group-containing dibenzothiophene, vinyl group-containing dibenzothiophene, and the like. In addition, since the monomer having a dibenzothiophene structure has a structure in which a thiophene ring and two benzene rings have been condensed, it is included in the concept of the monomer having a condensed aromatic ring structure. In addition, neither the dinaphthothiophene structure nor the dibenzothiophene structure is a structure in which more than two non-condensed aromatic rings are directly chemically bonded.

In several other aspects, a monomer having one aromatic ring (preferably a carbocyclic ring) per molecule can be used as the monomer (A1). Monomers with one aromatic ring in one molecule (monomers containing an odd number of aromatic rings) can, for example, help improve the flexibility of adhesives, adjust adhesive properties, improve transparency, etc. The monomer containing an odd number of aromatic rings can be used alone or in combination of two or more types. In some aspects, from the viewpoint of increasing the refractive index of the adhesive, a monomer having one aromatic ring per molecule may be used in combination with a monomer having a plurality of aromatic rings.

Examples of monomers having one aromatic ring in one molecule include: (benzylmeth)acrylate, methoxybenzyl(meth)acrylate, phenyl(meth)acrylate, ethoxylated phenol (meth)acrylate acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, toluyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, Carbon-containing aromatic ring (meth)acrylate 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-nonylphenylacrylate, 2 , 6-dibromo-4-dodecylphenyl acrylate and other bromine-containing substituted aromatic ring (meth)acrylates; styrene, α-methylstyrene, vinyltoluene, tertiary butylstyrene, etc. Vinyl compounds with carbon aromatic rings; heteroaromatic rings such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyridine, N-vinylpyrrole, N-vinylimidazole, and N-vinyl㗁azole have vinyl substituents compounds, etc.

The monomer (A1) may also be a monomer having a structure in which an oxygen ethyl chain is sandwiched between the ethylenically unsaturated group and the aromatic ring among the various aromatic ring-containing monomers mentioned above. As mentioned above, a monomer in which an oxygen ethyl chain is sandwiched between an ethylenically unsaturated group and an aromatic ring can be regarded as an ethoxylate of the original monomer. The repeat number of the oxyethyl unit (-CH ₂ CH ₂ O-) in the above oxyethyl chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, for example 1. Specific examples of ethoxylated aromatic ring-containing monomers include: ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated methacrylate Phenol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol di(meth)acrylate, etc.

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 some aspects, the content of the monomer containing multiple aromatic rings in the monomer (A1) can 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. It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. 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 type or two or more types of monomers containing a plurality of aromatic rings may be used. Furthermore, in several other aspects, for example, in consideration of high refractive index and flexibility, and if necessary, further consideration of balance with adhesive force, the monomer (A1) contains a plurality of aromatic ring-containing monomers. The content may be less than 100% by weight, may be less than 98% by weight, may be less than 90% by weight, may be less than 80% by weight, may be less than 70% by weight, may be less than 65% by weight, may be less than 50% by weight, It may be 25% by weight or less, or it may be 10% by weight or less. The technology disclosed here can still be implemented even if the content of the monomer containing a plurality of aromatic rings in the monomer (A1) is less than 5% by weight. It is also not necessary to use monomers containing multiple aromatic rings.

The content of the monomer containing a plurality of aromatic rings among the monomer components constituting the acrylic polymer is not particularly limited, and can be set to achieve an adhesive that achieves both the desired refractive index and flexibility. The content of the monomer containing multiple aromatic rings in the above monomer component 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 perspective of easily realizing an adhesive with a higher refractive index, the content of the monomer containing a plurality of aromatic rings in the above monomer components can be, for example, greater than 35% by weight or greater than 50% by weight. It is advantageous and should be greater 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, it can also be more than 91% by weight, more than 92% by weight, more than 93% by weight, 94% by weight. More than 95% by weight, more than 96% by weight, more than 97% by weight, more than 98% by weight or more than 99% by weight. The content of the monomer containing a plurality of aromatic rings in the above-mentioned monomer components is advantageous to be approximately 99% by weight or less in consideration of high refractive index and flexibility, and, if necessary, balance with adhesive force. , it can be 98 wt% or less, it can be 96 wt% or less, it can be 93 wt% or less, it can be 90 wt% or less, it can be 85 wt% or less, it can be 80 wt% or less, it can be 75 wt% or less. . In several other aspects, from the viewpoint of easily achieving higher adhesive properties and/or optical properties (such as transparency), the content of the monomer containing multiple aromatic rings in the above monomer component may be 70% by weight. It may be 60% by weight or less, it may be 50% by weight or less, it may be 40% by weight or less, it may be 25% by weight or less, it may be 15% by weight or less, or it may be 5% by weight or less. The technology disclosed here can still be implemented even if the content of monomers containing multiple aromatic rings in the above-mentioned monomer components is less than 3% by weight.

The content of the monomer containing a singular aromatic ring 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 a singular aromatic ring in the monomer (A1) can 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. It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Monomer (A1) may also be substantially 100% by weight of a monomer containing an odd number of aromatic rings. That is, as the monomer (A1), only one type or two or more types of monomers containing an odd aromatic ring may be used. Furthermore, in several aspects, for example, in consideration of high refractive index and flexibility, and if necessary, further consideration of balance with adhesive force, the monomer (A1) containing an odd number of aromatic rings is The content may be less than 100% by weight, may be less than 98% by weight, may be less than 90% by weight, may be less than 80% by weight, may be less than 70% by weight, may be less than 65% by weight, may be less than 50% by weight, may be The content may be 25% by weight or less, or 10% by weight or less. The technology disclosed here can still be implemented even if the content of the monomer containing a singular aromatic ring 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 the monomer containing an odd number of aromatic rings among the monomer components constituting the acrylic polymer is not particularly limited, and can be set to an adhesive that achieves both the desired refractive index and flexibility. The content of the monomer containing a singular aromatic ring in the above monomer component 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 perspective of easily realizing an adhesive with a higher refractive index, the content of the monomer containing a single aromatic ring in the above monomer component can be, for example, greater than 35% by weight or greater than 50% by weight. It is advantageous, and it is preferably more than 60% by weight, more 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, it can be more than 95% by weight, it can also be 98 More than % by weight. The content of the monomer containing an odd number of aromatic rings in the above monomer components can be set to about 99% by weight or less, taking into account high refractive index and flexibility, and further considering the balance with adhesive force if necessary. It may be 98% by weight or less, preferably 96% by weight or less, it may be 93% by weight or less, it may be 90% by weight or less, it may be 85% by weight or less, it may be 80% by weight or less, or it may be 75% by weight. the following. In several aspects, from the viewpoint of easily achieving higher adhesive properties and/or optical properties (such as transparency), the content of the monomer containing an odd number of aromatic rings in the above monomer components may be 70% by weight. It 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 still be implemented even if the content of monomers containing odd aromatic rings in the above-mentioned monomer components is less than 3% by weight.

In several ideal aspects, at least a part of the monomer (A1) may be suitably a high refractive index monomer. Here, the "high refractive index monomer" means a monomer whose refractive index is, for example, about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited. However, from the viewpoint of ease of preparation of the adhesive composition or ease of balancing softness suitable for use as an adhesive, it is, for example, 3.000 or less, and may be 2.500. below, it can be below 2.000, below 1.900, below 1.800, or below 1.700. The high refractive index monomer can be used individually by 1 type or in combination of 2 or more types. In addition, the refractive index of the monomer was measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. The Abbe refractometer can use model "DR-M4" manufactured by ATAGO Co., Ltd. or its equivalent. When a nominal value of the refractive index at 25°C is provided from the manufacturer, etc., the nominal value can be used.

The above-mentioned high refractive index monomer can be appropriately selected from the compounds included in the concept of the aromatic ring-containing monomer (A1) disclosed here (for example, the compounds and compound groups exemplified above) having the refractive index. Specific examples include: m-phenoxy benzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthylmethacrylate (refractive index: 1.595, Tg of homopolymer: 31 ℃), ethoxylated o-phenylphenol acrylate (repeat number of oxyethyl units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, homopolymer Tg: 6 ℃), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35 ℃), 6-acryloxymethyldinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacryloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-propene Dihydroxyethyl dinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloxyethyl dinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyl dinaphthothiophene (6VDNT, Refractive index: 1.802), 5-vinyl dinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793), etc., but are not limited by these.

The content of the high refractive index monomer (that is, the aromatic ring-containing monomer with a refractive index of about 1.510 or above, preferably about 1.530 or above, more preferably about 1.550 or above) in the monomer (A1) is not particularly limited. For example, it can be It may be 5% by weight or more, it may be 25% by weight or more, it may be 35% by weight or more, it 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, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be a high refractive index monomer. Furthermore, in several aspects, for example, from the viewpoint of balancing high refractive index and flexibility, and further taking into account adhesive strength if necessary, the content of the high refractive index monomer in the monomer (A1) can be Less than 100% by weight, it may be 98% by weight or less, it may be 90% by weight or less, it may be 80% by weight or less, or it may be 65% by weight or less.

The content of the high refractive index monomer among the monomer components constituting the acrylic polymer is not particularly limited, and can be set to an adhesive that achieves both the desired refractive index and flexibility. In addition, if necessary, it can also be set taking into account the adhesive properties (such as adhesive strength, etc.) and/or optical properties (such as total light transmittance, haze value, etc.). The content of the high refractive index monomer in the above monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In several aspects, among the monomer components constituting the acrylic polymer, the content of the high refractive index monomer can be, for example, greater than 35% by weight, and from the perspective of easily obtaining a higher refractive index, greater than 50% by weight is Advantageously, it should be greater 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, it can also be more than 95% by weight. The content of the high refractive index monomer in the above monomer components is advantageous to be 99% by weight or less from the viewpoint of balancing high refractive index and flexibility, and if necessary, adhesion strength. It may be 98% by weight or less, preferably 96% by weight or less, it may be 93% by weight or less, it may be 90% by weight or less, it may be 85% by weight or less, it may be 80% by weight or less, or it may be 75% by weight or less. .

In some ideal aspects, at least part of the monomer (A1) is an aromatic ring-containing monomer (hereinafter sometimes referred to as "monomer L") whose Tg of the homopolymer is 10° C. or lower. When adding the aromatic ring-containing monomer (A1) in the monomer component (especially equivalent to at least one of the above-mentioned plural aromatic ring-containing monomers, singular aromatic ring-containing monomers and high refractive index monomers) When the content of aromatic ring monomer (A1) is included, the storage elastic modulus G' of the adhesive will generally tend to increase. However, by using monomer L as part or all of the monomer (A1), the storage elasticity can be suppressed. Modulus G' rises. This allows a better balance between high refractive index and softness. 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 Tg of monomer L is not particularly limited. Considering the balance with the refractive index increasing effect, in several aspects, the Tg of the monomer L can be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. In several other aspects, the Tg of the monomer L can be, for example, -30°C or above, -10°C or above, 0°C or above, or 3°C or above. Monomer L can be used individually by 1 type or in combination of 2 or more types.

The monomer L can be appropriately selected from the compounds included in the concept of the aromatic ring-containing monomer (A1) disclosed here (for example, the compounds and compound groups exemplified above) having the Tg. 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 monomer L in monomer (A1) is not particularly limited. For example, it may be 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some aspects, from the viewpoint of easily obtaining an adhesive having both high refractive index and flexibility at a higher level, the content of monomer L in monomer (A1) may be, for example, 50% by weight or more, and From the viewpoint of improving softness, the content is preferably 60% by weight or more, 70% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. . Monomer (A1) may be substantially 100% by weight of monomer L. In addition, in several other aspects, for example, from the viewpoint of balancing high refractive index and flexibility, and further balancing the adhesive strength if necessary, the content of monomer L in monomer (A1) may be less than 100% by weight, it may be 98% by weight or less, it may be 90% by weight or less, it may be 80% by weight or less, or it may be 65% by weight or less.

The content of the monomer L in the monomer component 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 that combines high refractive index and softness at a higher level, the content of monomer L in the monomer component can be, for example, greater than 35% by weight, thereby improving the refractive index. From the viewpoint of weight ratio, it is advantageous to exceed 50% by weight, and preferably exceed 70% by weight. It may be 75% by weight or more, it may be 85% by weight or more, it may be 90% by weight or more, or it may be 95% by weight or more. From the viewpoint of balancing high refractive index with flexibility and, if necessary, adhesion strength, it is advantageous to set the content of monomer L in the above monomer component to about 99% by weight or less, and preferably to 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 or less.

In several aspects, the aromatic ring-containing monomer (A1) can also be combined with monomer L (that is, an aromatic ring-containing monomer with a homopolymer whose Tg is below 10°C) and a monomer with a Tg higher than 10°C. H to use. The Tg of monomer H can be, for example, higher than 10°C, higher than 15°C, or higher than 20°C. By using monomer L and monomer H in combination, in adhesives containing a large amount of aromatic ring-containing monomer (A1) in the monomer components, it is possible to achieve a higher level of both high refractive index and suitability of the adhesive. Due to its softness and close adhesion to the adherend. The usage ratio of monomer L and monomer H can be set to suitably exhibit the above effects, and is not particularly limited.

In several aspects, the aromatic ring-containing monomer (A1) can be suitably selected from compounds that do not have a structure in which two or more non-condensed aromatic rings are directly chemically bonded (for example, a biphenyl structure). For example, it is preferably an acrylic polymer composed of the following monomer components: the content of a compound containing a structure in which two or more non-condensed aromatic rings are directly chemically bonded is less than 5% by weight (preferably less than 3% by weight, It can also be 0% by weight). Regarding the restriction of the usage amount of compounds containing structures in which two or more non-condensed aromatic rings are directly chemically bonded, this is from the perspective of achieving a more balanced adhesive with high refractive index and flexibility, and further balancing adhesion if necessary. It seems to be beneficial.

The content of the monomer (A1) among the monomer components constituting the acrylic polymer is not particularly limited, and can be set to achieve a desired balance of refractive index and flexibility, as well as adhesive properties (such as adhesive strength, etc.) and/or optics. Adhesives with properties (such as total light transmittance, haze value, etc.). In several aspects, the content of the monomer (A1) in the above monomer component 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 some ideal aspects, the content of the monomer (A1) in the monomer components constituting the acrylic polymer can be, for example, greater than 70% by weight, and 75% by weight or more is appropriate; because it is easier to obtain a higher refractive index From the perspective of , more than 94% by weight, more than 95% by weight, more than 96% by weight, more than 97% by weight, more than 98% by weight or more than 99% by weight. The content of monomer (A1) in the above monomer components is typically less than 100% by weight, and from the perspective of balancing high refractive index and flexibility, and further taking into account adhesive strength if necessary, it is about 99% by weight. The following are advantageous, and may be 98% by weight or less, 96% by weight or less, 93% by weight or less, or 90% by weight or less. In several aspects, from the viewpoint of easily achieving higher adhesive properties and/or optical properties (such as transparency), the content of the monomer (A1) in the above monomer components may be less than 90% by weight, and may be less than 85% by weight, or less than 80% by weight.

(Single unit (A2)) In some ideal aspects, the monomer component constituting the acrylic polymer may further contain the monomer (A2) in addition to the above-mentioned monomer (A1). The above-mentioned monomer (A2) is a monomer corresponding to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxyl group (carboxyl group-containing monomer). The above-mentioned hydroxyl-containing monosystem is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The above-mentioned carboxyl group-containing monosystem is a compound containing at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer (A2) can contribute to introducing cross-linking points into the acrylic polymer or imparting appropriate cohesiveness to the adhesive. The monomer (A2) can be used individually by 1 type or in combination of 2 or more types. The monomer (A2) may or may not contain an aromatic ring. As the monomer (A2), a monomer containing no aromatic ring can be suitably used. In addition, monomer (A2) is defined as a monomer different from the aforementioned monomer (A1). For example, the aforementioned monomer (A1) can be defined as a monomer that does not have a hydroxyl group or a carboxyl group.

Examples of the ethylenically unsaturated group that the monomer (A2) has include (meth)acrylyl group, vinyl group, (meth)allyl group, and the like. From the viewpoint of polymerization reactivity, a (meth)acrylyl group is preferable, and from the viewpoint of improving flexibility or adhesiveness, an acrylyl group is more preferable. From the viewpoint of improving the flexibility of the adhesive, a compound having one ethylenically unsaturated group contained in one molecule (i.e., a monofunctional monomer) can be suitably used as the monomer (A2).

In several aspects, the monomer (A2) can use a monomer with a longer distance between the ethylenically unsaturated group (such as (meth)acrylyl group) and the hydroxyl group and/or carboxyl group. Thereby, in the aspect in which the above-mentioned hydroxyl group and/or carboxyl group are used in the cross-linking reaction, a cross-linked structure with high flexibility can be easily obtained. For example, the number of atoms (typically carbon atoms or oxygen atoms) constituting the chain (connecting chain) connecting the ethylenically unsaturated group and the hydroxyl group and/or carboxyl group may be 3 or more (for example, 4 or more, 5 or more, 6 Compounds above, 7 or above, 8 or above, 9 or above, 10 or above, 11 or above, 12 or above, 13 or above, 14 or above, 15 or above, 16 or above, 17 or above, 18 or above or 19 or above) are used as the monomer (A2) . The upper limit of the number of atoms constituting the connecting 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 connecting chain connecting the above-mentioned ethylenically unsaturated group to 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 connecting chain is composed of a linear alkylene group (that is, -(CH ₂ ) _n -group), the number of n becomes the number of atoms constituting the connecting chain. For another example, when the above-mentioned connecting chain is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of the sum of the number of carbon atoms 2 and the number of oxygen atoms 1 constituting the oxyethylene group 3 and n is ( 3n) becomes the number of atoms constituting the above-mentioned connecting chain. As the monomer (A2), an alkylene unit having at least one - for example - (CH ₂ ) _n - between the ethylenically unsaturated group and the hydroxyl group and/or carboxyl group, or - The oxyalkylene unit represented by (C _m H _2m O)- (for example, the oxyethylene unit in the aforementioned formula in which m is 2, the oxypropyl unit in the aforementioned formula in which m is 3, the oxyalkylene unit in the aforementioned formula m is an oxybutyl 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 1 or more (for example, 1 to 15 or 1 to 10 or 2 to 6 or 2 to 4). Furthermore, n in the formula representing the alkylene unit is, for example, an integer from 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. m in the formula representing the above-mentioned oxyalkylene unit is an integer of 2 or more, for example, an integer of 2 to 4. Monomer (A2) may include, in addition to the above-mentioned ethylenically unsaturated groups, hydroxyl and/or carboxyl groups, alkylene units and/or oxyalkylene units, ester bonds or ether bonds, thioether bonds, aromatic rings, Aliphatic rings and heterocyclic rings (for example, 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-hydroxyethylmeth)acrylate, 2-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, and 6-hydroxy(meth)acrylate. Hexyl ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (methyl) ) acrylate and other (meth)hydroxyalkyl acrylates; polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate and other polyesters Alkyl glycol mono(meth)acrylate, etc., but are not subject to these restrictions. 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 in the room temperature range, 4-hydroxybutyl acrylate with a lower Tg is preferred. In addition, in the aspect of using hydroxyalkyl (meth)acrylate as a hydroxyl group-containing monomer and utilizing the hydroxyl group in a cross-linking reaction, from the viewpoint of obtaining a highly flexible cross-linked structure, it is preferable to use the above ( The monomer with a large number of carbon atoms in the hydroxyalkyl group of hydroxyalkyl methacrylate is preferably a monomer with a carbon number of 3 or more (for example, 3 to 12, preferably 4 to 10) in the hydroxyalkyl group mentioned above. ) Hydroxyalkyl acrylate (such as 4-hydroxybutyl acrylate). In several ideal aspects, more than 50% by weight (eg, greater than 50% by weight, greater than 70% by weight, or greater than 85% by weight) of monomer (A2) may be 4-hydroxybutyl acrylate. The hydroxyl group-containing monomer can be used individually by 1 type or in combination of 2 or more types.

In several aspects of using a hydroxyl-containing monomer as the monomer (A2), the above-mentioned hydroxyl-containing monomer may be one or more types selected from compounds that do not have a methacryl group. Suitable examples of the hydroxyl-containing monomer having no methacrylic group include the above-mentioned various hydroxyalkyl acrylates. For example, it is preferred that more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl-containing monomer used as monomer (A2) is hydroxyalkyl acrylate. By using hydroxyalkyl acrylate, hydroxyl groups that help provide cross-linking points or impart appropriate cohesiveness can be introduced into the acrylic polymer more easily than when only the corresponding hydroxyalkyl methacrylate is used. Obtain an adhesive with good softness or adhesion in the room temperature area.

Examples of carboxyl group-containing monomers include, in addition to acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, Crotonic acid, isocrotonic acid, etc., but are not limited by these. Examples of carboxyl group-containing monomers that can be suitably used include acrylic acid and methacrylic acid. Furthermore, in some aspects, from the viewpoint of improving the flexibility of the adhesive, the carboxyl group-containing monomer is suitably used, for example, a compound represented by the following formula (1). 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)), and may be the same 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-mentioned 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: 2-(meth)acryloxyethylhexahydrophthalic acid, 2-(meth)acryloxyethyl-phthalate Acid, 2-(meth)acryloxyethyl-2-hydroxyethyl-phthalic acid, 2-(meth)acryloxyethyl-succinic acid, 2-(meth)acryloxyethyl Propyl hexahydrogen phthalate, 2-(meth)acryloxypropyl hydrogen phthalate, 2-(meth)acryloxypropyl tetrahydrophthalate, etc. The 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 may be used together.

The content of the monomer (A2) among the monomer components constituting the acrylic polymer is not particularly limited and can be set according to the purpose. In some aspects, the content of the above-mentioned monomer (A2) is, for example, 0.01% by weight or more, and 0.1% by weight or more is appropriate, and preferably it is 0.5% by weight or more. From the perspective of obtaining higher use effects, in several aspects, the content of the above-mentioned monomer (A2) can be set to 1% by weight or more, may be set to 2% by weight or more, or may be set to 3% 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 some aspects, it is appropriate to set the content of the above-mentioned monomer (A2) to, for example, 30% by weight or less or 10% by weight or less. However, by making the content of the monomer (A1) relatively large, it is easy to achieve a high refractive index. From this point of view, it is preferable to set it to 5% by weight or less. In several ideal aspects, from the perspective of improving flexibility, the content of the above-mentioned monomer (A2) is less than 5% by weight, preferably less than 3% by weight, and may also be less than 1.5% by weight.

(Single A3) In some aspects, the monomer component constituting the acrylic polymer may further contain (meth)acrylic acid alkyl ester (hereinafter also referred to as "monomer (A3)") in addition to the above-mentioned monomer (A1). Monomer (A3) can help improve the flexibility of the adhesive. In addition, it can also help improve the adhesive properties such as the compatibility of additives in the adhesive or the adhesion force. The monomer (A3) can be used individually by 1 type or in combination of 2 or more types.

The monomer (A3) can be suitably used for (meth)acrylic acid alkyl esters having a linear or branched chain alkyl group having 1 to 20 carbon atoms (i.e., C _1-20 ) at the end of the ester. Specific examples of (meth)acrylic acid C _1-20 alkyl esters include: (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid propyl ester, (meth)acrylic acid isopropyl ester , n-butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, amyl (meth)acrylate, (meth)acrylate ) Isoamyl 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, Decyl (meth)acrylate Diester, tridecyl (meth)acrylate, tetradecanyl (meth)acrylate, pentadecyl (meth)acrylate, cetylacrylate (meth)acrylate, heptadecyl (meth)acrylate, (meth)acrylate stearyl (meth)acrylate, isoctadecyl (meth)acrylate, nonadecanyl (meth)acrylate, eicosyl (meth)acrylate, etc., but are not limited by these.

In several aspects, at least a part of the monomer (A3) can suitably be a (meth)acrylic acid alkane whose Tg of the homopolymer is -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 softness of the adhesive. In addition, it can also help improve adhesive properties such as adhesive strength. The lower limit of Tg of the alkyl (meth)acrylate is not particularly limited, and may be -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the low-Tg (meth)acrylic acid alkyl ester include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), heptyl acrylate, octyl acrylate, and isononyl acrylate (iNA) wait. In several other aspects, at least part of the monomer (A3) may be an alkyl (meth)acrylate whose homopolymer has a Tg higher than -20°C (eg, above -10°C). The upper limit of Tg of the alkyl (meth)acrylate is, for example, 10°C or lower, 5°C or lower, or 0°C or lower. Alkyl (meth)acrylates with a Tg in this range can help adjust the softness of the adhesive. The (meth)acrylic acid alkyl ester having the above-mentioned Tg is preferably used in combination with the above-mentioned low-Tg (meth)acrylic acid alkyl ester, but there is no particular limitation. Specific examples of the (meth)acrylic acid alkyl ester having the above-mentioned Tg include lauryl acrylate (LA).

Among several aspects of using monomer (A3), it is preferable to use C _4-8 alkyl (meth)acrylate as monomer (A3). Among them, C _4-8 alkyl acrylate is preferably used. C _4-8 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 is easy to improve the flexibility of the adhesive and obtain good adhesive properties (adhesion, etc.). In the aspect of using C _4-8 alkyl (meth)acrylate as the monomer (A3), the alkyl (meth)acrylate contained in the monomer component has C _4-8 (meth)acrylate. The ratio of the alkyl ester is appropriately 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.

In several aspects of using monomer (A3), C _1-6 alkyl (meth)acrylate can be used as monomer (A3). By using C _1-6 alkyl (meth)acrylate, the storage elastic modulus in each temperature range can be adjusted. For example, setting the storage elastic modulus of the high-temperature region to a relatively high value can prevent the storage elastic modulus difference between the low-temperature region and the high-temperature region from becoming larger. Furthermore, the C _1-6 alkyl (meth)acrylate also tends to have excellent copolymerizability with the monomer (A1). C _1-6 alkyl (meth)acrylate can be used individually by 1 type or in combination of 2 or more types. In the case where C _1-6 alkyl (meth)acrylate is used as the monomer (A3), the C _1-6 alkyl (meth)acrylate is preferably C _1-6 alkyl acrylate. It is C _2-6 alkyl acrylate, more preferably C _4-6 alkyl acrylate. In several other aspects, the C _1-6 alkyl (meth)acrylate is preferably C _1-4 alkyl (meth)acrylate, and more preferably the C _2-4 alkyl (meth)acrylate , more preferably C _2-4 alkyl acrylate. A suitable example of C _1-6 alkyl (meth)acrylate is BA.

In the monomer components constituting the acrylic polymer, the content of 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 may be 8% by weight or more. In several aspects, from the viewpoint of improving flexibility, adhesion, etc., the content of the C _1-6 alkyl (meth)acrylate may be 10% by weight or more, may be 15% by weight or more, or may be It is 20 weight% or more, and may be 25 weight% or more (for example, 30 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, and may also be less than 35% by weight. In several aspects, from the viewpoint of maintaining a high refractive index, the content of the 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, may also be less than 1% by weight. The technology disclosed herein can be implemented without substantially using C _1-6 alkyl (meth)acrylate.

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

In the monomer component constituting the acrylic polymer, the content of C _7-12 alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or may be 8% by weight or more. In several aspects, from the viewpoint of improving flexibility, adhesion, etc., the content of the C _7-12 alkyl (meth)acrylate may be 10% by weight or more, may be 15% by weight or more, or may be It is 20 weight% or more, and may be 25 weight% or more (for example, 30 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, and may also be less than 35% by weight. In several aspects, from the viewpoint of maintaining a high refractive index, the content of the 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, may also be less than 1% by weight. The technology disclosed herein can be implemented without substantially using C _7-12 alkyl (meth)acrylate.

Among several aspects of using the monomer (A3), from the viewpoint of improving flexibility, at least a part of the monomer (A3) is preferably alkyl acrylate. The use of alkyl acrylate is also advantageous in terms of adhesive properties such as adhesive strength. For example, more than 50% by weight of monomer (A3) is preferably alkyl acrylate, and the ratio of alkyl acrylate in monomer (A3) is preferably more than 75% by weight, more preferably more than 90% by weight. (A3) may be substantially 100% by weight of alkyl acrylate. Only one or more acrylic acid alkyl esters may be used as the monomer (A3) and no alkyl methacrylic acid ester may be used.

In the case where the monomer component contains alkyl (meth)acrylate, the content of alkyl (meth)acrylate in the monomer component can be set so that the use effect can be appropriately exerted. In several aspects, the content of the 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 total 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. Therefore, 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 high. is beneficial. From the above point of view, it is appropriate that the content of monomer (A3) is less than 23% by weight of the monomer components, preferably less than 20% by weight, more preferably less than 17% by weight, can be less than 12% by weight, can be less than 7% by weight , can be less than 3% by weight or less than 1% by weight. The technology disclosed here can be suitably implemented even in a state that does not substantially use the monomer (A3).

(Other monomers) The monomer components constituting the acrylic polymer may also contain monomers other than the above-mentioned monomers (A1), (A2), and (A3) if necessary (hereinafter referred to as "other monomers"). The above-mentioned other monomers can be used, for example, to adjust the Tg of the acrylic polymer, adjust the adhesive properties, improve the compatibility in the adhesive layer, and the like. The above-mentioned other monomers can be used individually by 1 type or in combination of 2 or more types.

Examples of the 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 cohesion or heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphate group-containing monomers, and cyano group-containing monomers. In addition, as monomers that can be introduced into acrylic polymers into functional groups that can become cross-linking base points, or that can help improve the adhesion with the adherend or improve the compatibility in the adhesive, there are the following: Amino-containing monomers (such as (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, etc.), amine-containing monomers (such as amineethyl (meth)acrylate, N, N-dimethylaminoethyl (meth)acrylate, etc.), monomers with nitrogen-containing rings (such as N-vinyl-2-pyrrolidone, N-(meth)acrylomorphine etc.), acyl imine group-containing monomers, epoxy group-containing monomers, ketone group-containing monomers, isocyanate group-containing monomers, alkoxy silicone group-containing monomers, etc. In addition, among the monomers having a nitrogen atom-containing ring, there are those that are also equivalent to amide group-containing monomers, such as N-vinyl-2-pyrrolidone. The same applies to the relationship between the above-mentioned monomer having a nitrogen atom-containing ring and the amine group-containing monomer.

Other monomers that can be used in addition to the above-mentioned functional group-containing monomers include: vinyl ester monomers such as vinyl acetate; non-aromatic ring-containing monomers such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. (Meth)acrylate; olefin monomers such as ethylene, butadiene, isobutylene; chlorine-containing monomers such as vinyl chloride; methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylic acid Alkoxy group-containing monomers such as ester, ethoxyethoxyethyl (meth)acrylate, etc.; vinyl ether monomers such as methyl vinyl ether, etc. A suitable example of other monomers that can be used for the purpose of improving the softness of the adhesive is ethoxyethoxyethyl acrylate (alias: ethyl carbitol acrylate, Tg of the homopolymer: - 67℃).

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

In several aspects, the monomer components constituting the acrylic polymer may be a composition in which the usage amount of the methacrylate group-containing monomer is suppressed to below a predetermined level. The usage amount of the methacrylyl group-containing monomer in the monomer component may be, for example, less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. It is advantageous to limit the amount of the methacryl group-containing monomer used in this way from the viewpoint of achieving an adhesive that balances softness or adhesiveness with a high refractive index. The monomer components constituting the acrylic polymer may also be a composition that does not contain a methacrylate group-containing monomer (for example, a composition consisting only of an acryl group-containing monomer).

In several aspects, the amount of carboxyl group-containing monomers used in the monomer components constituting the acrylic polymer has been limited from the viewpoint of suppressing coloration or discoloration (such as yellowing) of the adhesive. The usage amount of the carboxyl group-containing monomer in the monomer component may be, for example, 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. Such limitation of the amount of the carboxyl group-containing monomer is also advantageous from the viewpoint of inhibiting corrosion of metal materials that can come into contact with the adhesive disclosed herein or that can interact with the adhesive disclosed herein. The adhesive is disposed adjacent to metal materials (such as metal wiring or metal films that may exist on the adherend). The technology disclosed here can be implemented in a state where the monomer components constituting the acrylic polymer do not contain carboxyl group-containing monomers. For the same reason, in several aspects, the usage amount of monomers having acidic functional groups (including, in addition to carboxyl groups, sulfonic acid groups, phosphate groups, etc.) among the monomer components constituting the acrylic polymer is preferably limited. The ideal usage amount of the acidic functional group-containing monomer in the monomer component of the above aspect can be applied to the ideal usage amount of the above-mentioned carboxyl group-containing monomer. The technology disclosed here can be implemented in a state where the monomer component does not contain an acidic group-containing monomer (that is, a state where the acrylic polymer is acid-free).

(glass transition temperature) The monomer component constituting the acrylic polymer preferably has a composition such that the glass transition temperature (Tg) of the monomer component is approximately 15° C. or lower. In several aspects, the above-mentioned Tg is preferably 10°C or lower, more preferably 5°C or lower, more preferably 1°C or lower, and may also be 0°C or lower. In several other aspects, the above-mentioned Tg may be -10°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, or -35°C or lower. From the viewpoint of improving the flexibility of the adhesive, a low Tg is advantageous. In addition, the above-mentioned Tg may be, for example, -60°C or higher. From the viewpoint of making it easy to increase the refractive index of the adhesive, it is preferably -50°C or higher, more preferably higher than -45°C, and may also be higher than -40°C. . In several aspects, the above-mentioned Tg can be higher than -30°C, higher than -20°C, higher than -10°C, or higher than -5°C. An adhesive having both high refractive index and flexibility can be suitably formed by using an acrylic polymer having a composition having a Tg in the above range.

Here, Tg based on the composition of the monomer components constituting the acrylic polymer means the glass transition temperature calculated from the Fox equation based on the composition of the monomer components, unless otherwise specified. The Fox formula is shown below and is a relational formula between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer after each of the monomers constituting the copolymer is homopolymerized. 1/Tg=Σ(Wi/Tgi) In the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the homopolymerization of monomer i. The glass transition temperature of the object (unit: K). Regarding the glass transition temperature of the homopolymer used in the calculation of Tg, the value described in publicly known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) is used. Regarding the monomers with multiple values recorded in the above Polymer Handbook, the highest value is used. When the Tg of the homopolymer is not described in publicly known documents, the value obtained by the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 is used.

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

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

The initiator used for polymerization can be appropriately selected from known polymerization initiators according to the type of polymerization method. For example, one or more types of azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be suitably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide initiators such as benzyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; Aromatic carbonyl compounds, etc. Another example of the polymerization initiator is an oxygen reduction initiator composed of a combination of a peroxide and a reducing agent. A polymerization initiator can be used individually by 1 type or in combination of 2 or more types. The usage amount of the polymerization initiator may be a normal usage amount. For example, it can be selected from the range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) based on 100 parts by weight of the monomer component.

In the above-mentioned polymerization, various conventionally known chain transfer agents may be used as necessary. For example, thiols such as n-dodecylmercaptan, tertiary dodecylmercaptan, hydrogen sulfoacetic acid, and α-thioglycerol can be used. Alternatively, a chain transfer agent containing no sulfur atoms (non-sulfur chain transfer agent) may also be used. Examples of non-sulfur 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 a chain transfer agent is used, the usage amount can be, for example, about 0.01 to 1 part by weight relative to 100 parts by weight of the monomer component.

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited. For example, it is about 30×10 ⁴ or more, and about 50×10 ⁴ or more is suitable. It may be about 70×10 ⁴ or more, or it may be about 80. ×10 ⁴ or more. By using an acrylic polymer whose Mw is equal to or higher than a predetermined value, it is possible to easily obtain appropriate cohesive force that exhibits desired adhesive properties. In addition, more additives such as plasticizers can be contained, which tends to make it easier to achieve desired softness. In addition, the upper limit of Mw of the acrylic polymer is, for example, about 500×10 ⁴ or less. From the viewpoint of adhesive performance, it is preferably about 400×10 ⁴ or less (more preferably about 150×10 ⁴ or less, for example, about 130 ×10 ⁴ or less). In several aspects, the above-mentioned Mw may be less than 100×10 ⁴ , may be 80×10 ⁴ or less, or may be 60×10 ⁴ or less. The effects brought about by the technology disclosed here can be suitably achieved by using an acrylic polymer having an Mw in the above range.

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 trade name "HLC-8220GPC" (manufactured by Tosoh Corporation) as a GPC measurement device and measuring under the following conditions. [GPC measurement conditions] Sample concentration: 0.2% by weight (tetrahydrofuran solution) Sample injection volume: 10µL Eluate: Tetrahydrofuran (THF) Flow (flow rate): 0.6mL/minute Column temperature (measurement temperature): 40℃ Pipe string: Sample column: 1 piece with the brand name "TSKguardcolumn SuperHZ-H" + 2 pieces with the brand name "TSKgel SuperHZM-H" (manufactured by Tosoh Corporation) Reference column: 1 brand name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation) Detector: Differential Refractometer (RI) Standard sample: polystyrene

(Plasticizer) The adhesive composition disclosed here is characterized by containing a plasticizer in addition to the acrylic polymer. By using plasticizers, the flexibility of the adhesive can be improved. In addition, in the state of forming an adhesive, the compliance with deformation can be improved. The plasticizer disclosed here may use a cyclic unsaturated organic compound having two or more rings containing double bonds. In other words, the above-mentioned plasticizer is a compound having two or more double bond-containing rings in one molecule. Therefore, the above-mentioned plasticizer has at least a first double bond-containing ring and a second double bond-containing ring. By having more than two rings containing double bonds, the refractive index of the adhesive can be maintained without damaging it, or the flexibility of the adhesive can be improved while maintaining the refractive index. In addition, by using a plasticizer with two or more double bond-containing rings (such as aromatic rings), the interaction and affinity with acrylic polymers having aromatic rings can be improved, which can help improve the adhesive properties. its stability. From this viewpoint, in several aspects, the number of double bond-containing rings that the plasticizer has is preferably 3 or more, more preferably 4 or more, more preferably 5 or more, and may also be 6 or more. In addition, from the viewpoint of exerting the plasticizing effect, the number of double bond-containing rings that the plasticizer has is preferably 10 or less, for example, and may be 8 or less. In several other aspects, the number of double bond-containing rings of the above-mentioned plasticizer is preferably 6 or less, may be 4 or less, or may be 3 or less. A plasticizer can be used individually by 1 type or in combination of 2 or more types.

In addition, the plasticizer used in the technology disclosed here can be used so that the amount of transfer into the gas phase at 130°C (130°C vaporization amount) is 10% or less on a weight basis (specifically, 0 to 10% by weight). of plasticizer. By using a plasticizer that satisfies these characteristics, changes in the characteristics of the adhesive containing the plasticizer caused by the plasticizer can be suppressed with respect to changes in temperature or humidity. For example, it can become an adhesive that exhibits stable properties even when used in environments exposed to high temperatures or high humidity or used for a long period of time. The vaporization amount of the plasticizer at 130°C is preferably less than 10% by weight, preferably less than 5% by weight, more preferably less than 3% by weight, especially less than 1% by weight (specifically less than 1.0% by weight, such as less than 0.9% by weight, less than 0.8% by weight, less than 0.7% by weight, less than 0.6% by weight, less than 0.5% by weight, less than 0.4% by weight, less than 0.3% by weight, less than 0.2% by weight, less than 0.1% by weight). The transfer amount of the plasticizer into the gas phase at 130°C can be obtained from the weight change before and after keeping the plasticizer at 130°C for 1 hour. More specifically, it can be measured by the method described in the Examples mentioned later.

In addition, the plasticizer is preferably a compound that is liquid at 30°C. In addition, in this specification, "liquid state" means fluidity, and means liquid in the state of matter. The compound includes compounds with a melting point below 30°C. The above-mentioned plasticizer is liquid at 30°C, so it can properly exert its plasticizing effect and effectively improve the flexibility of the adhesive. 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 that has two or more double bond-containing rings and is liquid at 30° C. as the plasticizer, an adhesive having both high refractive index and flexibility can be suitably formed.

In several ideal forms, the molecular weight of the plasticizer is above 350. Plasticizers with a large molecular weight are difficult to vaporize, so by using a plasticizer with a molecular weight of 350 or more in an adhesive, an adhesive that exhibits stable characteristics can be easily obtained. In addition, plasticizers with large molecular weight are difficult to move within the adhesive. Therefore, it is less likely for the plasticizer to move to the surface of the adhesive and affect the adhesive properties. The molecular weight of the above-mentioned plasticizer is preferably above 400, more preferably above 450, especially above 500, and may also be above 530. The upper limit of the molecular weight of the above-mentioned plasticizer is not particularly limited. From the viewpoint of easily exhibiting the plasticizing effect, it is suitable to be 30,000 or less, and 25,000 or less is advantageous. It can 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 below 2000, more preferably below 1200, more preferably below 900, and may also be below 600. From the viewpoint of improving the compatibility in the adhesive layer, it is advantageous that the molecular weight of the plasticizer is not too large. In addition, the molecular weight of the plasticizer can be calculated based on its chemical structure. When a nominal value of molecular weight is provided from the manufacturer or the like, the nominal value can be used.

The double bond-containing ring of 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 type of ring selected from aromatic rings and heterocycles 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 double-bond-containing heterocyclic ring structure different from the aromatic ring. The double bond-containing ring that the plasticizer can have (typically an aromatic ring) can be a benzene ring (which can be a benzene ring that forms part of the biphenyl structure or the fluorine structure); naphthalene ring, indene ring, azulene ring, anthracene ring , a carbon ring such as a condensed ring of a phenanthrene ring; it can also be a pyridine ring, a pyrimidine ring, a pyridine ring, a pyridine ring, a trisulfonate ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an ethyl azole ring, Heterocycles such as isoethazole ring, thiazole ring, thiophene ring, etc. The heteroatoms contained as ring constituent atoms in the heterocyclic ring may be, for example, one or two or more types selected from the group consisting of nitrogen, sulfur, and oxygen. In several aspects, the heteroatoms constituting the heterocyclic ring may be one or both of nitrogen and sulfur. The plasticizer may have a structure in which one or two or more carbocyclic rings and one or two or more heterocyclic rings are condensed, such as a dinaphthothiophene structure.

The above-mentioned double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have 1 or more substituents on the atoms constituting the ring, or may have no substituents. When there is a substituent, examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, and a propylene oxide group. Oxygen groups, etc., but are not limited by these. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In several aspects, the above-mentioned double bond-containing ring may be an aromatic ring without substituents on the ring constituent atoms, or may be an aromatic ring with no substituents on the ring constituent atoms selected from the group consisting of alkyl, alkoxy, and vinyl groups. An aromatic ring with one or more substituents in the group consisting of unsaturated groups (such as (meth)acryloxy groups), hydroxyl groups and hydroxyalkyl groups. As the substituent, an alkyl group, an alkoxy group, or a hydroxyalkyl group can be suitably used.

In several aspects, it may be appropriate to use compounds without ethylenically unsaturated groups as plasticizers. This can prevent the adhesive composition from deteriorating due to heat or light (the progression of gelation or the decrease in leveling properties caused by an increase in viscosity), thereby improving storage stability. The use of plasticizers that do not have ethylenically unsaturated groups suppresses changes in elastic modulus, dimensional changes, or It is also good from the viewpoint of deformation (warping, undulation, etc.), occurrence of optical strain, etc.

As the plasticizer, a high refractive index plasticizer having a refractive index of about 1.50 or more can be suitably used. By using high refractive index plasticizers, high refractive index and improved softness can be achieved at a higher level. From the viewpoint of improving flexibility while maintaining and increasing the refractive index of the adhesive, the refractive index of the plasticizer is preferably about 1.51 or more, more preferably about 1.53 or more, more preferably about 1.55 or more, especially about It can be above 1.56, it can be above about 1.58, it can be above about 1.60, it can be above about 1.62. In several aspects, from the viewpoint of the ease of preparation of the adhesive composition or the compatibility in the adhesive, the refractive index of the plasticizer is 2.50 or less, and it is advantageous to have a refractive index of 2.00 or less. It can be below 1.90, it can be below 1.80, it can also be below 1.70. In addition, the refractive index of the plasticizer was measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C, in the same manner as the refractive index of the monomer. When a nominal value of the refractive index at 25°C is provided from the manufacturer, etc., the nominal value can be used.

In several aspects, the plasticizer may use a compound having a structure in which two or more non-condensed double bond-containing rings (typically aromatic rings) are bonded via a linking group. The above-mentioned linking group can be, for example: oxygen group (-O-), thiooxy group (-S-), oxyalkylene group (such as -O-(CH ₂ ) _n - group, where n is 1 to 3, Preferably, it is 1), thiooxyalkylene group (for example, -S-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1), straight-chain alkylene group (that is, -(CH ₂ ) _n - group, here n is 1 to 6, preferably 1 to 3), the alkylene group in the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group and the above-mentioned linear alkylene group has been partially halogenated or completely halogenated groups, etc. The above-mentioned connecting group may 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) may be selected from the same type as above. From the viewpoint of improving the flexibility of the adhesive, in several aspects, suitable examples of the above-mentioned linking groups include oxyalkylene groups. In this aspect, the number of atoms of the connecting group is, for example, 10 or more, preferably 15 or more, more preferably 20 or more, more preferably 22 or more (for example, 25 or more or 30 or more). Furthermore, the upper limit of the number of atoms of the connecting group is, for example, 50 or less, ideally 40 or less is appropriate, and may be 35 or less. In the aspect of using a plasticizer having an oxyalkylene group as the linking group, the number of atoms of the linking group is suitably used. In several other aspects, suitable examples of the above-mentioned linking groups include siloxane bonds. In this aspect, the number of atoms of the above-mentioned linking group is not particularly limited. For example, it is 1 to 30, preferably 1 to 12, more preferably 1 to 5, and may also be 1 or 2. In addition, the number of atoms of the linking group refers to the minimum number of atoms required from one non-condensed ring containing double bonds to another non-condensed ring containing double bonds. For example, when the linking group is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of the sum of the carbon number 2 and the oxygen atom number 1 that constitute the oxyethylene group 3 and n (3n) It becomes the number of atoms connecting the base.

In some aspects, an ethylene glycol compound having two or more double bond-containing rings per molecule can be used as the plasticizer. The number of oxyethylene units (i.e. -(C ₂ H ₄ O)- units) possessed by the above-mentioned ethylene glycol compound is, for example, 1 or more, and 2 or more is appropriate, preferably 3 or more, more preferably 4 or more ( For example, 5 or more). Moreover, the upper limit of the number of the said oxyethylene units is, for example, 10 or less, 8 or less, or 6 or less. The above-mentioned ethylene glycol compound may be a compound having the following structure: two or more non-condensed double bond-containing ring spacers are bonded with the above-mentioned oxyethyl unit as a linking group. The compound may have one or more ester groups. Examples of the ethylene glycol-based compound include compounds having a structure in which two or more benzoic acids are connected to triethylene glycol or polyethylene glycol via an ester bond.

In the aspect of using an ethylene glycol-based compound having two or more double-bond-containing rings per molecule as a plasticizer, the usage amount of the above-mentioned ethylene glycol-based compound is not particularly limited, and is set to achieve the results disclosed herein. Characteristics and effects of adhesives. From the viewpoint of improving the flexibility of the adhesive, the usage amount of the above-mentioned ethylene glycol compound relative to 100 parts by weight of the acrylic polymer may be, for example, 1 part by weight or more, or may be 10 parts by weight or more. In several aspects, the usage amount of the above-mentioned ethylene glycol compound can be greater than 10 parts by weight, greater than 15 parts by weight, more than 20 parts by weight, or 30 parts by weight relative to 100 parts by weight of the acrylic polymer. above. In several ideal aspects, the usage amount of the above-mentioned ethylene glycol compound is greater than 30 parts by weight relative to 100 parts by weight of the base polymer, preferably 35 parts by weight or more, more preferably 40 parts by weight or more, especially 45 parts by weight. It may be more than 50 parts by weight, more preferably more than 50 parts by weight, it may be more than 55 parts by weight, and it may be more than 60 parts by weight. In addition, from the viewpoint of balancing the high refractive index and flexibility of the adhesive, it is appropriate to set the usage amount of the above-mentioned ethylene glycol compound to approximately 200 parts by weight or less relative to 100 parts by weight of the base polymer. It may be 150 parts by weight or less, preferably 120 parts by weight or less, it may be 100 parts by weight or less, it may be 80 parts by weight or less, or it may be 70 parts by weight or less.

In several aspects, polysiloxane-based plasticizers can be used as the plasticizer. By using polysiloxane plasticizers, it is easy to obtain a stable plasticizing effect and high adhesion. Therefore, the refractive index, softness and adhesion of the adhesive can be improved in a balanced manner. The polysiloxane plasticizer may be a compound having two or more double bond-containing rings and a transfer amount of 10% or less to the gas phase at 130° C., without particular limitation. In addition, the polysiloxane plasticizer is preferably a compound that is liquid at 30°C. The polysiloxane plasticizer is specifically a siloxane compound, and the number of Si atoms in the compound is 1 or more (typically 2 or more). The upper limit is not particularly limited, but may be about 10 or less, for example. In one molecule of polysiloxane plasticizer, the Si atom and the ring containing a double bond may or may not be directly bonded. At least one of the above-mentioned Si atoms is preferably directly bonded to at least one ring containing a double bond. A polysilicone plasticizer can be used individually by 1 type or in combination of 2 or more types.

In some aspects, the polysiloxane plasticizer may be composed of a siloxane compound with a Si atom number of 2 to 5, and at least one of the Si atoms is present in the Si atom. The upper bond has more than 2 rings containing double bonds. The polysiloxane plasticizer composed of the siloxane compound having the above structure can exert a plasticizing effect based on the flexibility of the siloxane structure. At the same time, because the polysiloxane plasticizer has Si The number of atoms is 2 or more and 5 or less and it has at least one Si atom bonded to two or more rings containing double bonds. Therefore, it is possible to balance the ease of blending or compatibility with the material to be plasticized and the above-mentioned plasticization. Stability of effect (for example, for storage under moist heat, the rate of increase in elastic modulus is low). From the viewpoint of chemical stability, the above-mentioned siloxane compound preferably does not have hydrogen atoms bonded to Si atoms. That is, a siloxane compound having no Si-H bond is preferred.

When the number of Si atoms in the siloxane compound is 3 or more, the siloxane compound may be chain-shaped or cyclic. However, from the viewpoint of suppressing volatilization, a chain-shaped siloxane compound is preferred. The chain siloxane compound having Si atoms of 3 or more may be linear or branched, but is preferably linear from the viewpoint of obtaining a higher plasticizing effect. Hereinafter, unless otherwise specified, a 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 plasticizer may be independently a conjugated double bond-containing ring (typically an aromatic ring), or may be a non-conjugated double bond-containing ring. The plasticizer may have at least one type of ring selected from aromatic rings and heterocycles 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 double-bond-containing heterocyclic ring structure different from the aromatic ring. The double bond-containing ring that the plasticizer may have (typically an aromatic ring) 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, an ethazole ring, a thiazole ring, Heterocyclic rings such as thiophene ring. The heteroatoms contained as ring constituent atoms in the heterocyclic ring may be, for example, one or two or more types selected from the group consisting of nitrogen, sulfur, and oxygen. In several aspects, the heteroatoms constituting the heterocyclic ring may be one or both of nitrogen and sulfur.

The above-mentioned double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have 1 or more substituents on the atoms constituting the ring, or may have no substituents. When having a substituent, examples of the substituent include alkyl group, alkoxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidoxy group, etc., However, it is not subject to such restrictions. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In several aspects, each of the double bond-containing rings of the polysiloxane plasticizer is independently selected from the group consisting of aromatic rings that do not have substituents on the ring constituting atoms and aromatic rings that have substituents. , the substituent of the substituent aromatic ring is selected from 1 of 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 plasticizer are independently selected from aromatic rings (preferably carbocyclic rings) without substituents on the atoms constituting the ring. In several ideal forms, each ring containing double bonds in the polysiloxane plasticizer is a benzene ring.

From the perspective of the ease of exerting the plasticizing effect and its stability (for example, suppressing the increase in elastic modulus caused by the volatilization and dissipation of the plasticizer from the material mixed with the plasticizer), The number of Si atoms in the above-mentioned siloxane compound is preferably 3 or more. In addition, 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-based plasticizer in which the number of Si atoms in the above-mentioned siloxane compound is 3, that is, a polysiloxane-based plasticizer composed of a trisiloxane compound is also preferred.

The number of double bond-containing rings (such as benzene rings with or without substituents) of the above-mentioned siloxane compound is at least 2, and the heat resistance due to the plasticizing effect (for example, for storage under moist heat, elasticity From the viewpoint of low module increase rate), it is preferably 3 or more, more preferably 4 or more, and it may be 5 or more. Furthermore, when the number of Si atoms of the siloxane compound is n, the number of double bond-containing rings that the siloxane compound has is typically 2n+2 or less. From the viewpoint of improving the plasticizing effect, it is 2n+1 or less is appropriate, preferably 2n or less, 2n-1 or less, or 2n-2 or less. For example, in the aspect where the above-mentioned siloxane compound is a trisiloxane compound, the number of double bond-containing rings that the trisiloxane compound has is typically 8 or less, and may be, for example, 2 or more and 7. Below, the number may be 3 or more and 7 or less, or the number 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 preferred.

In several aspects, at least one of the Si atoms (typically the Si atoms constituting the siloxane chain) contained in the above-mentioned siloxane compound is Si bonded with two or more rings containing double bonds. atom. From the viewpoint of improving the stability of the plasticizing effect, the number of Si atoms bonded with two or more double bond-containing rings 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 rings containing double bonds may be 2 or more, or may be 3 or more. In addition, let the Si of the above siloxane compound be When the number of atoms is n, it may be n or less, n-1 or less, or n-2 or less. In several aspects, from the viewpoint of improving the plasticizing effect, at least one Si atom contained in the siloxane compound (preferably a siloxane compound with 3 or more Si atoms) is used. , the number of rings containing double bonds 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) rings containing double bonds, and the two Si atoms A siloxane compound in which the Si atoms other than the terminals independently have a ring containing a double bond or a structure that does not have a ring containing a double bond.

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

In several aspects, the above-mentioned siloxane compound preferably does not have ethylenically unsaturated groups (including those in which the double bond in the ring containing double bonds 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 about by the plasticizer, and it also contains From the viewpoint of the storage stability of the adhesive sheet of the adhesive layer of the above-mentioned polysiloxane plasticizer, or to suppress the change in elastic modulus, dimensional change or deformation (warping, undulation, etc.) caused by the reaction of the ethylenically unsaturated group ), the occurrence of optical strain, etc. are also good.

In several aspects of the polysiloxane plasticizer disclosed here, from the viewpoint of improving the plasticizing effect, at least one Si atom (the number of Si atoms is 3) contained in the above-mentioned siloxane compound It is preferable that the Si atom has at least 1 methyl group (at least 2 of the above siloxane compounds). For example, the Si atoms located at both ends of the siloxane chain preferably independently have 1 or 2 (preferably 1) methyl groups. In several ideal aspects, the Si atoms contained in the above-mentioned siloxane compound each independently have 1 or 2 methyl groups. According to the polysiloxane plasticizer composed of the siloxane compound of the above structure, the plasticizing effect brought by the flexibility of the siloxane structure and the ability to bond to at least one Si atom can be balanced The stability of the above-mentioned plasticizing effect brought about by the structure of more than two 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 2 of them are rings containing double bonds. In several aspects, the ratio SR of the number of double bond-containing rings (preferably aromatic carbon rings, such as benzene rings) in the total number of substituents of the polysiloxane plasticizer is at least 16%, which can be It is more than 20%, and it can also be more than 25%. If the above-mentioned ratio SR becomes higher, the heat resistance of the polysilicone-based plasticizer or the stability of the plasticizing effect provided by the polysilicone-based plasticizer will generally tend to increase. In several aspects, it is advantageous for the above ratio SR to be 33% or more, preferably 40% or more, more preferably 50% or more (for example, 60% or more), 65% or more, or 75% or more. The above 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, 75% or less, 65% or less, or is less than 60% (for example, less than 50%).

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

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

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

In the aspect of using a polysiloxy plasticizer as the plasticizer, the usage amount of the above-mentioned ethylene glycol compound is not particularly limited, and is set to achieve the adhesive properties and effects disclosed here. From the viewpoint of improving the flexibility of the adhesive, the usage amount of the above-mentioned polysiloxane plasticizer relative to 100 parts by weight of the acrylic polymer may be, for example, 1 part by weight or more, or may be 10 parts by weight or more. In several ideal aspects, the usage amount of the above-mentioned polysiloxy plasticizer relative to 100 parts by weight of the acrylic polymer can be greater than 10 parts by weight, can be greater than 15 parts by weight, can be more than 20 parts by weight, and can be 30 parts by weight. It may be more than 30 parts by weight, it may be more than 35 parts by weight, or it may be more than 40 parts by weight. Furthermore, from the viewpoint of balancing the high refractive index and flexibility of the adhesive, it is appropriate to set the usage amount of the above-mentioned polysiloxane plasticizer to approximately 200 parts by weight or less relative to 100 parts by weight of the base polymer. It is preferably 150 parts by weight or less, more preferably 100 parts by weight or less, more preferably 80 parts by weight or less, especially 60 parts by weight or less (for example, less than 60 parts by weight), it can be 55 parts by weight or less, it can be It may be 50 parts by weight or less, or 45 parts by weight or less.

The amount of plasticizer used is not particularly limited. In order to obtain the target softness, it can be set according to the relationship with other adhesive-containing components (typically acrylic polymers). From the viewpoint of improving the flexibility of the adhesive, the usage amount of the plasticizer relative to 100 parts by weight of the acrylic polymer may be, for example, 1 part by weight or more, or may be 10 parts by weight or more. In some ideal aspects, the plasticizer can be used in an amount greater than 10 parts by weight relative to 100 parts by weight of the acrylic polymer. In addition, by using the plasticizer disclosed herein, an adhesive with good stability can be obtained, so that it can contain more plasticizers than before, and the flexibility of the adhesive can be further improved. From this point of view, the usage amount of the plasticizer is more than 15 parts by weight relative to 100 parts by weight of the acrylic polymer, may be more than 20 parts by weight, or may be more than 30 parts by weight (for example, more than 30 parts by weight). In several aspects, the usage amount of the plasticizer relative to 100 parts by weight of the acrylic polymer is preferably 40 parts by weight or more, more preferably 50 parts by weight or more, and may also be 55 parts by weight or more. For example, when using the above-mentioned ethylene glycol compound as a plasticizer, it is preferable to use more than 30 parts by weight (for example, 40 parts by weight or more, further 50 parts by weight or more, 55 parts by weight or more) based on 100 parts by weight of the acrylic polymer. In addition, from the viewpoint of balancing the high refractive index and flexibility of the adhesive, it is appropriate to set the usage amount of the plasticizer to approximately 200 parts by weight or less relative to 100 parts by weight of the acrylic polymer, and preferably 150 parts by weight. parts by weight or less, preferably 120 parts by weight or less, 100 parts by weight or less, 80 parts by weight or less, or 70 parts by weight or less. In several aspects that pay more attention to the adhesive properties, the usage amount of the plasticizer relative to 100 parts by weight of the acrylic polymer can be 45 parts by weight or less, or it can be 35 parts by weight or less.

In addition, the adhesive composition disclosed here may also contain one or more than two kinds of plasticizers with a vaporization amount of more than 10% by weight at 130°C (for example, plasticizers with a molecular weight of less than 350) within the scope that does not significantly impair the effect of the invention. agent). It is appropriate that the usage amount of any plasticizer (such as phenoxybenzyl acrylate used in the examples described below) is less than 50% by weight of the total plasticizer used in the adhesive composition, and preferably less than 30% % by weight, preferably less than 10% by weight (for example, less than 9% by weight, less than 8% by weight, less than 7% by weight, less than 6% by weight, less than 5% by weight, less than 4% by weight, less than 3% by weight, less than 2% by weight or less than 1% by weight). The techniques disclosed herein can be suitably implemented using adhesive compositions that do not substantially contain any of the plasticizers described above.

(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 included as an additive used as desired. Hereinafter, the organic material may be expressed as "additive (H _RO )". Here, the above-mentioned “H _RO ” represents an organic material with a high refractive index (High Refractive index). By using a combination of additives (H _RO ) and acrylic polymers, an adhesive that is more suitable for both refractive index and adhesive properties (peel strength, softness, etc.) can be realized. Organic materials that can be used as additives (H _RO ) can be polymers or non-polymers. Moreover, it may or may not have a polymerizable functional group. In addition, in this specification, the additive (H _RO ) is defined as a compound that is different from the compound that can be used as the above-mentioned plasticizer. Therefore, the additive (H _RO ) may specifically be one that is not liquid (liquid) at 30°C (eg, 25°C or 20°C). The additive (H _RO ) can be used individually by 1 type or in combination of 2 or more types.

The refractive index of the additive (H _RO ) can be set to an appropriate range in relation to the refractive index of the acrylic polymer, and is therefore 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 with a higher refractive index 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 advantageous to be 1.58 or higher, preferably 1.60 or higher, more preferably 1.63 or higher, and may be 1.65 or higher. , can be above 1.70, or above 1.75. By using an additive with a higher refractive index (H _RO ), the target refractive index can still be achieved even with a smaller amount of additive (H _RO ). This is preferable from the viewpoint of suppressing deterioration in adhesive properties or optical properties. The upper limit of the refractive index of the additive (H _RO ) is not particularly limited. However, from the viewpoint of compatibility in the adhesive, ease of achieving a high refractive index, and flexibility suitable for use as an adhesive, for example, it is 3.000 or less. It can be below 2.500, below 2.000, below 1.950, below 1.900, or below 1.850. In addition, the refractive index of the additive (H _RO ) was measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C, in the same manner as the refractive index of the monomer. When a nominal value of the refractive index at 25°C is provided from the manufacturer, etc., the nominal value can be used.

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. The molecular weight of the additive (H _RO ) may be, for example, 130 or more or 150 or more. In several 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, 230 or more, and 250 or more. It can be more than 270, it can be more than 300, it can be more than 500, it can be more than 1,000, it can be more than 2,000. In addition, from the viewpoint of balancing the effect of increasing the refractive index with 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 approximately Less than 10,000 is appropriate, preferably less than 5,000, preferably less than 3,000 (for example, less than 1,000), can be less than 800, can be less than 600, can be less than 500, can also be less than 400. From the viewpoint of improving the compatibility in the adhesive, it is advantageous that the molecular weight of the additive (H _RO ) is not too large. In several aspects, polymers with molecular weights of about 1,000 to 10,000 (for example, more than 1,000 and less than 5,000) can be used as additives (H _RO ). The molecular weight of the additive (H _RO ) can be calculated based on the chemical structure of a non-polymer or polymer with a low degree of polymerization (for example, around 2 to 5 polymers), or matrix-assisted laser desorption time-of-flight mass analysis can be used. The measured value obtained by the method (MALDI-TOF-MS). When the additive (H _RO ) is a polymer with a higher degree of polymerization, the weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. When a nominal value of molecular weight is provided from the manufacturer or the like, the nominal value can be used.

Examples of organic materials that can be optional additives (H _RO ) include organic compounds with aromatic rings, organic compounds with heterocyclic rings (which can be aromatic rings or non-aromatic heterocyclic rings), etc., but are not subject to this etc. are limited.

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 the compound that can be used as the monomer (A1). Choose from similar items.

The above-mentioned aromatic ring may have one or more substituents on the ring constituting atoms, or may have no substituents. When there is a substituent, examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, and a propylene oxide group. Oxygen groups, etc., but are not limited by these. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1 to 10, 1 to 6 is advantageous, preferably 1 to 4, more preferably 1 to 3, for example, it can be 1 or 2. In several aspects, the above-mentioned aromatic ring may be an aromatic ring without substituents on the ring constituent atoms, or may be an aromatic ring with alkyl groups, alkoxy groups and halogen atoms (such as bromine) on the ring constituent atoms. Atom) is an aromatic ring consisting of 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 monomer (A1); oligomers containing compounds that can be used as monomer (A1) as monomer units; The group having an ethylenically unsaturated group (which may be a substituent bonded to a ring constituting atom) or the part constituting the ethylenically unsaturated group in the group is removed from the compound that can be used as the monomer (A1), and Structure substituted with hydrogen atoms or groups without ethylenically unsaturated groups (such as hydroxyl, amine, halogen atom, alkyl, alkoxy, hydroxyalkyl, hydroxyalkyloxy, glycidoxy, etc.) compounds, etc., and may include those that do not conform to the plasticizers disclosed here, but are not limited thereto.

Among several aspects, organic compounds having two or more aromatic rings per molecule (hereinafter also referred to as "compounds containing multiple aromatic rings") can be suitably used because a high refractive index-increasing effect can be easily obtained. ) as additive (H _RO ). The compound containing a plurality of aromatic rings may or may not have polymerizable functional groups such as ethylenically unsaturated groups. In addition, the compound containing multiple aromatic rings may be a polymer or a non-polymer. In addition, the above-mentioned polymer may be an oligomer containing a monomer containing a plurality of aromatic rings as a monomer unit (an oligomer with a molecular weight of approximately 5,000 or less, more preferably approximately 1,000 or less; for example, a 2- to 5-mer unit) Low polymer of left and right). The above-mentioned oligomer can be, for example, a homopolymer of a monomer containing a plurality of aromatic rings; a copolymer of two or more monomers containing a plurality of aromatic rings; one or more types of monomers containing a plurality of aromatic rings. Copolymers with other monomers, etc. The above-mentioned other monomers may be aromatic ring-containing monomers that do not qualify as monomers containing multiple aromatic rings, may be monomers without aromatic rings, or may be a combination thereof. In the case of using an oligomer as an additive (H _RO ), the oligomer can be obtained by polymerizing the corresponding monomer component by a known method.

Non-limiting examples of compounds containing multiple aromatic rings include: compounds having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, compounds having two or more non-condensed aromatic rings directly (that is, not separated by other atoms) ) compounds with a chemically bonded structure, compounds with a condensed aromatic ring structure, compounds with a fluorine structure, compounds with a dinaphthothiophene structure, compounds with a dibenzothiophene structure, etc. The compound containing a plurality of aromatic rings can be used individually by 1 type or in combination of 2 or more types.

Examples of organic compounds having a heterocyclic ring (hereinafter also referred to as heterocyclic-containing organic compounds) that can be optional additives (H _RO ) include thioepoxy compounds, compounds having a tricyclic ring, and the like. Examples of thioepoxy compounds 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 tri-𠯤 ring include a compound having at least one (for example, 3 to 40, preferably 5 to 20) tri-𠯤 rings per molecule. In addition, the three-𠯤 ring is aromatic, so the compounds with the three-𠯤 ring are also included in the above-mentioned concept of compounds containing aromatic rings, and the compounds with multiple tri-𠯤-rings are also included in the above-mentioned compounds containing multiple aromatic rings. in the concept.

In several aspects, it may be appropriate to use compounds without ethylenically unsaturated groups as additives (H _RO ). This can prevent the adhesive composition from deteriorating due to heat or light (the progression of gelation or the decrease in leveling properties caused by an increase in viscosity), thereby improving storage stability. The use of an additive (H _RO ) that does not have an ethylenically unsaturated group prevents dimensional changes or deformation caused by the reaction of the ethylenically unsaturated group (H _RO ) in an adhesive sheet having an adhesive layer containing the additive (H RO ). It is also good from the viewpoint of the occurrence of warpage, undulation, etc.) and the occurrence of optical strain.

The additive (H _RO ) may be used in an appropriate amount within a range that does not significantly impair the effects of the technology disclosed herein. In some aspects, the usage amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer (the total amount when using multiple compounds) can be set to, for example, 80 parts by weight or less, taking into account the balance. From the viewpoint of increasing the refractive index of the adhesive and suppressing deterioration in adhesive properties or optical properties, it is advantageous to set the content to 60 parts by weight or less, and preferably 45 parts by weight or less. In several aspects where more emphasis is placed on adhesive properties or optical properties, the usage 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, 10 parts by weight or less, or 3 parts by weight. The amount may be less than 1 part by weight, or less than 1 part by weight. By limiting the usage amount of the additive (H _RO ) within a predetermined range, it is easy to form an adhesive with good characteristics and stability. The techniques disclosed herein may be suitably implemented using adhesive compositions that do not contain additives ( _HRO ). Furthermore, from the viewpoint of increasing the refractive index of the adhesive, the usage 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 at 3 parts by weight or more. , preferably 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, may be 20 parts by weight or more.

(cross-linking agent) The adhesive composition disclosed here may contain a cross-linking agent if necessary in order to adjust the cohesive force of the adhesive. Cross-linking agents can use isocyanate-based cross-linking agents, epoxy-based cross-linking agents, azazoline-based cross-linking agents, oxazoline-based cross-linking agents, melamine-based resins, metal chelate-based cross-linking agents, etc. in the field of adhesives A well-known cross-linking agent. Among them, isocyanate cross-linking agents and epoxy cross-linking agents can be suitably used. Other examples of the cross-linking agent include monomers having two or more ethylenically unsaturated groups in one molecule, that is, polyfunctional monomers. A cross-linking agent can be used individually by 1 type or in combination of 2 or more types.

As the isocyanate cross-linking agent, an isocyanate compound having two or more functions can be used. Examples include: trimethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), Aliphatic polyisocyanates such as diisocyanate; cyclopentyl diisocyanate, cyclohexyl diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane Alicyclic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, styrene diisocyanate (XDI) and other aromatic isocyanates; isocyanate compounds are treated with ureaformic acid Polyisocyanate modified bodies modified by ester bonds, biuret bonds, isocyanate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, ditriketone bonds, etc. (for example HDI melanoisocyanate, HDI allophanate, etc.). Examples of commercially available products include: brand names TAKENATE 300S, TAKENATE 500, TAKENATE 600, TAKENATE D165N, TAKENATE D178N, TAKENATE D178NL (above, manufactured by Mitsui Chemicals Co., Ltd.), Sumidur T80, Sumidur L, Desmodur N3400 (above, Sumika Bayer Urethane) Corporation), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX, Coronate 2770 (above, manufactured by Tosoh Corporation), trade name Duranate A201H (above, manufactured by Asahi Kasei Corporation), etc. The 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 be used together.

Examples of the epoxy cross-linking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylidene glycidyl ether, polyethylene glycol diepoxypropyl ether, and glycerin diepoxypropyl ether. Ether, glyceryl triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diaminoglycidyl amine, N,N,N',N'-tetraepoxypropyl-m-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, and polypropylene glycol di(meth)acrylate. , neopentyl glycol di(meth)acrylate, neopentylerythritol di(meth)acrylate, neopentylerythritol tri(meth)acrylate, dineopenterythritol hexa(meth)acrylate, Ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate 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, hexyl glycol di(meth)acrylate, etc. The polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

In several aspects, at least a portion of the cross-linking agent may use a bifunctional cross-linking agent having two cross-linking reactive groups (eg, isocyanate groups) per molecule. By using a bifunctional cross-linking agent, a soft cross-linked structure can be easily formed. A bifunctional crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Furthermore, a bifunctional crosslinking agent may be used in combination with a trifunctional or higher than trifunctional crosslinking agent.

In several aspects, the cross-linking agent may suitably use a non-cyclic cross-linking agent (also known as 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 cross-linking agents, it is preferable to use an isocyanate-based compound that does not have a ring structure such as an aromatic ring or a isocyanate ring. By using a non-cyclic isocyanate-based compound as a cross-linking agent, a cross-linking agent with high flexibility can be easily formed. Specific examples of the above-mentioned non-cyclic isocyanate include: aliphatic isocyanate compounds (such as PDI or HDI), or modified forms of aliphatic isocyanate compounds (such as PDI or HDI via allophanate bond, biuret bond) , urea bond, carbodiimide bond modified polyisocyanate modified body). Acyclic cross-linking agent can be used individually by 1 type or in combination of 2 or more types. In several ideal aspects, a non-cyclic bifunctional cross-linking agent can be used as the above-mentioned cross-linking agent.

In several aspects, a cross-linking agent with a longer distance between one cross-linking reactive group (eg, isocyanate group) and another cross-linking reactive group in one molecule can be used as the cross-linking agent. Thereby, a soft cross-linked structure having a predetermined or longer length can be formed. For example, a compound in which the number of atoms constituting a connecting chain connecting a cross-linking reactive group and other cross-linking reactive groups in one molecule of the cross-linking agent is 10 or more (for example, 12 or more or 14 or more) can be used as the cross-linking agent. . The upper limit of the number of atoms constituting the connecting chain can be adjusted according to the purpose through polymerization or the like, and is therefore not particularly limited. For example, it may be 2,000 or less, it may be 1,000 or less, it may be 500 or less, it may be 100 or less, it may be 50 or less, it may be Below 30, it can also be below 20. In addition, the number of atoms constituting the connecting chain connecting the cross-linking reactive groups means that in one cross-linking agent molecule, from one cross-linking reactive group to another cross-linking reactive group (when there are three or more cross-linking reactive groups) , is the minimum number of atoms required for the cross-linking reactive group closest to the above-mentioned cross-linking reactive group). The cross-linking agent having the above-described connecting chain can be used alone or in combination of two or more types. In several ideal aspects, a non-cyclic bifunctional cross-linking agent can be used as the above-mentioned cross-linking agent. Commercially available examples of the cross-linking agent include trade name Coronate 2770 (manufactured by Tosoh Corporation), trade name TAKENATE D178NL (manufactured by Mitsui Chemicals Co., Ltd.), trade name Duranate A201H (manufactured by Asahi Kasei Co., Ltd.), and the like.

The usage amount of the cross-linking agent is not particularly limited, but may be in the range of approximately 0.001 to 5.0 parts by weight relative to 100 parts by weight of the acrylic polymer. From the perspective of improving the softness of the adhesive or the adhesion to the adherend, in several aspects, the usage amount of the cross-linking agent relative to 100 parts by weight of the acrylic polymer is preferably 3.0 parts by weight or less. It is preferably 2.0 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, or 0.2 parts by weight or less. In addition, from the viewpoint of appropriately exerting the effect of the cross-linking agent, in some aspects, the usage amount of the cross-linking agent relative to 100 parts by weight of the acrylic polymer may be, for example, 0.005 parts by weight or more, and may be 0.01 parts by weight. Parts or more 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 make the cross-linking reaction proceed more efficiently, a cross-linking catalyst can also be used. Examples of cross-linking catalysts include: tetra-n-butyl titanate, tetraisopropyl titanate, zirconium tetraacetyl acetonate, iron (III) acetyl acetonate, butyl tin oxide, dioctyl tin dilaurate and other metal systems Cross-linking catalysts, etc. Among them, tin-based cross-linking catalysts such as dioctyl tin dilaurate are preferred. There is no particular restriction on the amount of cross-linking catalyst used. Taking into account the balance between the speed of the cross-linking reaction and the service life of the adhesive composition, the usage amount of the cross-linking catalyst relative to 100 parts by weight of the acrylic polymer can be, for example, approximately 0.0001 to 1 part by weight. The range of is preferably 0.001 parts by weight or more and 0.5 parts by weight or less.

The adhesive composition may contain a compound that can produce keto-enol tautomerism as a cross-linking retardant. This can achieve the effect of extending the service life of the adhesive composition. For example, a compound that can produce keto-enol tautomerism can be suitably used in an adhesive composition containing an isocyanate cross-linking agent. Various β-dicarbonyl compounds can be used as compounds capable of producing keto-enol tautomerism. For example, β-diketones (acetyl acetone, 2,4-hexanedione, etc.) or acetyl acetate esters (methyl acetyl acetate, ethyl acetate acetate, etc.) can be suitably used. The compound which can produce keto-enol tautomerism can be used individually by 1 type, or in combination of 2 or more types. The usage amount of the compound that can generate keto-enol tautomerism can be, for example, 0.1 to 20 parts by weight, or 0.5 to 10 parts by weight based on 100 parts by weight of the acrylic polymer. parts or less, and may be 1 part by weight or more and 5 parts by weight or less.

(Adhesive agent) The adhesive compositions disclosed herein may also contain adhesive agents. The tackifying agent can use rosin-based tackifying resin, terpene-based tackifying resin, phenol-based tackifying resin, hydrocarbon-based tackifying resin, ketone-based tackifying resin, polyamide-based tackifying resin, epoxy-based tackifying resin, Well-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 usage amount of the tackifying resin is not particularly limited and can be set according to the purpose and use to achieve appropriate adhesive properties. In some aspects, from the viewpoint of refractive index or transparency, it is appropriate to set the usage amount of the tackifier to 30 parts by weight or less based on 100 parts by weight of the acrylic polymer, and preferably 10 parts by weight or less. , preferably 5 parts by weight or less. The techniques disclosed herein may be suitably implemented without the use of adhesion promoters.

(High refractive index particles) The adhesive composition disclosed here 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 expressed as "particles P _HRI ". HRI means high refractive index. The type of particle P _HRI is not particularly limited. One or two 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. Particle P _HRI can be suitably used from inorganic oxides (such as metal oxides) that can increase the refractive index of the adhesive. Suitable examples of materials constituting the particles P _HRI include titanium oxide (titania, TiO ₂ ), zirconium oxide (zirconia, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and 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 singly or in combination of two or more types. The average particle diameter of the particles P _HRI (referring to the 50% volume average particle diameter obtained by the laser scattering diffraction method) is not particularly limited, and may be selected from the range of approximately 1 nm or more and 1000 nm or less, for example.

The particles P _HRI in the adhesive composition can be used in an appropriate amount within the range that does not impair the effects of the technology disclosed herein. In addition, the content of the above particles P _HRI may vary according to the refractive index of the target. For example, the content of the above-mentioned particle P _HRI can be appropriately set so that the refractive index becomes a predetermined or higher level in consideration of the required adhesive properties and the like. In several aspects, the content of the particles P _HRI in the adhesive composition is, for example, less than 10% by weight, less than 1% by weight, or less than 0.1% by weight in the adhesive formed from the adhesive composition. The techniques disclosed herein can be implemented in such a manner that the adhesive composition is substantially free of particle P _HRI .

(leveling agent) In several aspects, the adhesive composition may contain modifiers as needed 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 coating properties of the adhesive composition. Leveling agent. Non-limiting examples of leveling agents include acrylic leveling agents, fluorine leveling agents, silicone leveling agents, and the like. The leveling agent can be appropriately selected from commercially available leveling agents and used in a conventional manner.

(Other additives) In addition, the adhesive composition disclosed here may also contain softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, and anti-aging agents as required within the scope that does not significantly hinder the effects of the present invention. Well-known additives that can be used in the adhesive composition include agents, ultraviolet absorbers, antioxidants, light stabilizers, and preservatives. As for the various additives mentioned above, conventionally known ones can be used in a conventional manner, and since they do not particularly impart any features to the present invention, detailed descriptions thereof are omitted.

The effect brought about by the technology disclosed here is through the use of adhesives containing the above-mentioned acrylic polymer and a specific plasticizer (a plasticizer with a vaporization capacity of less than 10% at 130°C, such as a plasticizer with a molecular weight of 350 or more) agent composition to achieve. The technology disclosed here can be suitably implemented in an aspect using an adhesive composition mainly composed of the above-mentioned acrylic polymer and the above-mentioned specific plasticizer. Therefore, in some ideal aspects, a composition in which the content of the acrylic polymer and components other than the specific plasticizer (other components) is limited can be used. For example, in the adhesive composition (and thus the adhesive formed from the adhesive composition), the total amount of the above-mentioned acrylic polymer and the above-mentioned specific plasticizer can be set as the non-volatile component of the adhesive composition (i.e. adhesive) of more than 75% by weight (for example, more than 75% by weight and less than 100% by weight or less than 100% by weight), it can be more than 85% by weight, it can be more than 90% by weight, it can be more than 95% by weight, it can be 98 It may be more than 99% by weight (for example, more than 99% by weight). The fact that the use of components other than the above-mentioned acrylic polymer and the above-mentioned specific plasticizer is suppressed is advantageous in terms of improving the stability of the characteristics of the adhesive.

＜Adhesive＞ The adhesive disclosed herein can be formed using any of the above adhesive compositions, for example. The adhesive can be an adhesive that is hardened by drying, cross-linking, polymerizing, cooling, etc., from solvent-based, active energy ray-hardening, water-dispersed, hot-melt, etc. adhesive compositions, that is, It may be a hardened product of the above-mentioned adhesive composition. Only one method of hardening the adhesive composition (such as drying, cross-linking, polymerization, cooling, etc.) can be used, or two or more methods can be used simultaneously or in multiple stages. For solvent-based adhesive compositions, the composition is typically dried (preferably further cross-linked) to form the adhesive. For active energy ray-curable adhesive compositions, the adhesive is typically formed by irradiating active energy rays to proceed with polymerization and/or cross-linking reactions. When the active energy ray curable adhesive composition must be dried, active energy rays can be irradiated after drying.

(Heating loss of plasticizer in adhesive) The adhesive disclosed here can be the following, which is characterized in that: after being kept in an environment of 130°C for 1 hour, the reduction of the plasticizer in the adhesive is less than 5% on a weight basis (specifically: 0~5% by weight). Regarding an adhesive that satisfies this characteristic, even if the adhesive is heated under predetermined conditions, almost all the plasticizer in the adhesive will remain in the adhesive and its effect (mainly the plasticizing effect) can be maintained. Therefore, the above-mentioned adhesive has suppressed the change in characteristics caused by the plasticizer, so that it can still exhibit stable characteristics even under the use environment or long-term use. The above-mentioned reduction of the plasticizer in the adhesive after being kept at 130°C for 1 hour should be less than 3% by weight, more preferably less than 1% by weight, more preferably less than 0.5% by weight, it can be less than 0.3% by weight, or it can be 0.1% by weight. the following. The above-mentioned loss of the plasticizer in the adhesive after being kept at 130°C for 1 hour can be calculated from the weight change of the plasticizer in the adhesive before and after being kept at 130°C for 1 hour. The amount of plasticizer in the adhesive can be quantified, for example, by liquid chromatography. More specifically, it can be measured by the method described in the Examples mentioned later.

(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 technology disclosed here, it is possible to provide an adhesive having a refractive index of, for example, 1.55 or more, an adhesive composition capable of forming the adhesive, and an adhesive sheet including the adhesive. The refractive index of the above-mentioned adhesive is more than 1.560, preferably greater than 1.570. In several ideal aspects, the refractive index of the adhesive can be above 1.575, above 1.580, above 1.585, above 1.590, or above 1.595. The adhesive having the above refractive index can suitably suppress light reflection at the interface with the adherend when it is attached to a material with a high refractive index. The ideal upper limit of the refractive index of the adhesive may vary depending on the refractive index of the adherend, etc., so it is not limited to a specific range. It may be, for example, 1.700 or less, 1.670 or less, 1.650 or less, 1.620 or less, or Can be below 1.600.

The refractive index of the adhesive can be adjusted, for example, by the composition of the adhesive (eg, the composition of the monomer components constituting the acrylic polymer). Specifically, an adhesive exhibiting a refractive index above a predetermined level can be prepared by using an acrylic polymer containing a large amount of monomer (A1) in the monomer component or by selecting a type of plasticizer.

In addition, in this specification, the refractive index of the adhesive means the refractive index of the surface (adhesive surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) at a measuring wavelength of 589 nm and a measuring temperature of 25°C. An Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO Co., Ltd. or its equivalent can be used. The measurement sample can use an adhesive layer composed of the adhesive of the evaluation object. The refractive index of the adhesive can be measured specifically by the method described in the Examples described below.

(Storage elastic modulus G') Although not limited to a specific range, the storage elastic modulus G' (0°C) of the adhesive at 0°C can be, for example, less than 1.0×10 ⁸ Pa, or less than 5.0×10 ⁷ Pa, or It is less than 1.0×10 ⁷ Pa and can also be less than 5.0×10 ⁶ Pa. The adhesive with 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, but may be, 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 higher than a predetermined value, the adhesive can easily have moderate cohesion in a normal temperature range to a high temperature range. In several aspects, the storage elastic modulus G' (0°C) of the adhesive is, for example, 1.0×10 ⁶ Pa or less, preferably 5.0×10 ⁵ Pa or less, 2.0×10 ⁵ Pa or less, or 1.0 ×10 ⁵ Pa or less, 7.0 × 10 ⁴ Pa or less, 5.0 × 10 ⁴ Pa or less, or 3.0 × 10 ⁴ Pa or less. In addition, the storage elastic modulus G' (0°C) is preferably 1.0×10 ⁴ Pa or more, more preferably 2.0×10 ⁴ Pa or more, more preferably 4.0×10 ⁴ Pa or more, and may be 6.0×10 ⁴ Pa or more. , it can also be 1.0×10 ⁵ Pa or more. An adhesive with a storage elastic modulus G' (0°C) in the above range can have both high refractive index and flexibility, and has flexibility that can withstand repeated bending operations.

The storage elastic modulus G' (-20°C) of the adhesive disclosed here is not particularly limited, for example, it can be less than 1.0×10 ¹⁰ Pa, it can be less than 1.0×10 ⁹ Pa, it can be 5.0×10 ⁸ Pa The following are suitable: 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. An adhesive whose storage elastic modulus G' (-20°C) is limited as mentioned above can become one with particularly excellent softness. For example, it can have good flexibility in a lower temperature range and flexibility that can withstand repeated bending operations in a wide temperature range including a low temperature range. The lower limit of the above-mentioned storage elastic modulus G' (-20°C) is not particularly limited. For example, it is 1.0×10 ² Pa or more, and 1.0×10 ³ Pa or more is appropriate. It is preferably 1.0×10 ⁴ Pa or more, and more preferably 1.0×10 ⁵ Pa or above, may be 5.0×10 ⁵ Pa or above, or may be 1.0×10 ⁶ Pa or above. An adhesive having the above-mentioned storage elastic modulus G' (-20°C) can be flexible and have moderate cohesion. In addition, according to the adhesive having the above-mentioned storage elastic modulus G' (-20° C.), there is a tendency that it is easy to achieve both high refractive index and flexibility even in a low-temperature region.

The storage elastic modulus G' (25°C) of the adhesive disclosed here is not particularly limited. For example, less than 1.0×10 ⁶ Pa is appropriate, preferably less than 5.0×10 ⁵ Pa, and more preferably less than 3.0×10 ⁵ Pa may be less than 1.0×10 ⁵ Pa or less than 5.0×10 ⁴ Pa. An adhesive with a limited storage elastic modulus G' (25°C) as mentioned above has good flexibility under normal use temperatures such as room temperature. The lower limit of the storage elastic modulus G' (25°C) is not particularly limited. For example, it is 1.0×10 ² Pa or more, and 5.0×10 ² Pa or more is appropriate. It is preferably 1.0×10 ³ Pa or more, and more preferably 5.0. ×10 ³ Pa or more, or 1.0 × 10 ⁴ Pa or more. Adhesives with the above-mentioned storage elastic modulus G' (25°C) tend to have moderate cohesion at normal operating temperatures.

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

In several aspects, the ratio of the storage elastic modulus G'(-20°C) at -20°C to the storage elastic modulus G'(25°C) at 25°C (G'(-20°C) can be used )/G'(25℃)) in the range of 1~1000 is used as the adhesive. Adhesives that satisfy the above characteristics can exhibit characteristics (flexibility, etc.) that are stable against temperature changes because the change in elastic modulus is suppressed in a wide temperature range from a lower temperature range to a room temperature range. The above ratio (G'(-20°C)/G'(25°C)) may be 500 or less, 300 or less, 150 or less, or 100 or less. The lower limit of the ratio (G'(-20°C)/G'(25°C)) may be, for example, 5 or more, 50 or more, 100 or more, or 200 or more.

(Change in elastic modulus after holding at 130°C for 1 hour) In several aspects, it is advisable to use the following adhesive: the storage elastic modulus G'1 at -20°C after the adhesive is kept at 130°C for 1 hour, and the storage elastic modulus G'1 at 130°C. The ratio of storage elastic modulus G'0 (G'1/G'0) at -20°C hours ago was 50 or less (specifically, 1 to 50). Even if an adhesive that meets this characteristic is exposed to high temperatures, the change in elastic modulus is still limited to a predetermined range and can exhibit stable characteristics. The above ratio (G'1/G'0) is preferably 30 or less, more preferably 10 or less, more preferably 3 or less, it may be 2 or less, or it may be less than 1.5.

(glass transition temperature) The glass transition temperature (Tg) of the adhesive is not particularly limited, but can be set taking into account the flexibility in low-temperature areas or the cohesion (heat resistance, etc.) in high-temperature areas. In several aspects, the Tg of the adhesive is, for example, 30°C or lower, may be 15°C or lower, or may be 10°C or lower. In several ideal aspects, from the perspective of flexibility, the Tg of the adhesive is below 5°C, may be below 0°C, may be below -5°C, may be below -10°C, may be below -15 ℃ or below (for example, below -20 ℃). The lower the Tg of an adhesive, the more excellent the adhesive properties such as adhesion to the adherend tend to be. In addition, by setting the Tg of the adhesive to be low, the elastic modulus change in a temperature range higher than Tg can be suppressed. The lower limit of the Tg of the adhesive is, for example, -50°C or higher, preferably -40°C or higher, and may also be -30°C or higher. According to the adhesive having the above-mentioned Tg, appropriate cohesive force tends to be easily obtained. Furthermore, it tends to form an adhesive that has both high refractive index and flexibility. In several aspects, the Tg of the adhesive can be above -25°C, above -12°C, above -3°C, or above 0°C.

The storage elastic modulus G' of the adhesive at each of the above temperatures and the Tg of the adhesive can be measured by the method described in the examples described below, and each storage elastic modulus ratio can be calculated from the results. The change in elastic modulus after holding at 130° C. for 1 hour can be measured specifically by the method described in the examples below. Each storage elastic modulus G' of the adhesive, each storage elastic modulus ratio, the elastic modulus change after holding at 130°C for 1 hour, and Tg can be determined by, for example, selecting the composition of the monomer components constituting the acrylic polymer ( For example, select the type and content of monomer (A1)), select the type or amount of plasticizer, whether to use cross-linking agent and select the type and amount, whether to use additives, and select the type and amount, etc. to adjust.

(Haze value) In several aspects, the haze value of the adhesive (such as the adhesive layer constituting the adhesive sheet) can be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, It may be 0.9% or less, it may be 0.8% or less, it may be 0.5% or less, or it may be 0.3% or less. Adhesives with such high transparency can be suitably used in applications that require high light transmittance (such as optical applications) or applications that require good visibility of the performance of the adherend through the adhesive. There is no particular lower limit for the haze value of the adhesive. From the perspective of improving transparency, the smaller the haze value, the better. On the other hand, in several aspects, the haze value may be, for example, 0.05% or more, or 0.10% or more, taking into account the refractive index or adhesive properties. These haze values regarding the adhesive can also be appropriately applied to the haze of the adhesive sheet when the technology disclosed herein is implemented in the form of an adhesive sheet without a substrate (typically an adhesive sheet composed of an adhesive layer). degree value.

The "haze value" here means the ratio of diffusely transmitted light to total transmitted light when a measurement object is irradiated with visible light. Also known as Haze Value. The haze value can be expressed 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 haze value can be measured according to the method described in the examples below. The haze value of the adhesive can be adjusted by, for example, selecting the composition or thickness of the adhesive layer.

(total light transmittance) In several aspects, the total light transmittance of the adhesive (layer) is preferably above 85.0% (for example, above 88.0%, above 90.0%, or above 90.0%). Adhesives with such high transparency can be suitably used in applications that require high light transmittance (such as optical applications) or applications that require good visibility of the performance of the adherend through the adhesive. Practically, 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 may be about 94% or less, may be about 93% or less, or may be about 92% or less, taking into account refractive index or adhesive properties. The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the trade 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 can be adjusted, for example, by selecting the composition or thickness of the adhesive.

In addition, in several aspects, the total light transmittance of the bending part of the adhesive after repeated bending tests for 10 times (total light transmittance after the bending test) should be maintained at the total light transmittance before the bending test. The rate is more than 85%. The aforementioned bending test is a test in which each side of the sheet adhesive is bent into a U-shape with a radius of 2 mm at 25°C and this operation is regarded as one group. Adhesives that satisfy the above characteristics have little change in optical properties (such as whitening) even if they are repeatedly bent, so they are suitable for optical applications where bending is expected, such as foldable displays. The total light transmittance after the above-mentioned bending test is preferably more than 90% of the total light transmittance before the bend test, more preferably more than 95%, especially more than 98% (for example, more than 99%). The total light transmittance after the above-mentioned bending test can be determined by selecting the composition of the monomer components constituting the base polymer, setting the weight average molecular weight (Mw) of the base polymer, selecting the type or amount of plasticizer, and whether cross-linking is used Adjust by selecting the type and amount of additives, whether or not to use additives, and selecting the type and amount.

The total light transmittance after the above-mentioned bending test was measured by the following method. That is, the adhesive layer was cut into a rectangular shape of 2 cm×10 cm to obtain a test piece for measurement. A cylindrical rod with a diameter of 4 mm is fixed horizontally at a height sufficient for measurement, and the test piece obtained above is placed on the rod, and one side is bent into a U-shape with a radius of 2 mm and held for 1 minute. Specifically, the center portion of the test piece in the longitudinal direction is placed on a rod to form an inverted U shape. Then, fix the two ends below the test piece with a clamp (13g), hang a 60g weight on the clamp through a 1cm long wire and fix it, and apply a load to the flexural part of the test piece. In this state, the test piece is kept in a predetermined temperature environment (or 25° C.) for 1 minute, and after 1 minute, the test piece is removed from the rod. Next, under the same temperature environment, the other side of the test piece (the side opposite to the above-mentioned one side) is bent into a U-shape with a radius of 2 mm using the opposite side of the bending part of the above-mentioned one side in the same manner as the above-mentioned one side. Hold for 1 minute. After repeatedly performing a bending test on the above-mentioned bent portion of the same test piece 10 times as a set, the bending test of the above-mentioned bent portion was measured using the same method as the measurement method of the total light transmittance described in the Examples described later. Total light transmittance after refraction [%].

(deformation characteristics) Although there is no particular limit, in several aspects, the deformation amount of the adhesive in the deformation test carried out at a temperature of -20°C and a speed of 300mm/min is preferably more than 350%. Adhesives that meet this characteristic can deform at high speed and fully even in low temperature environments, and can withstand large deformations. An adhesive that satisfies the above characteristics would ideally have a high refractive index and be able to withstand use in applications involving large deformation, such as foldable display applications.

In addition, in the deformation test of the adhesive disclosed here at a temperature of -20°C and a speed of 300 mm/min, the stress at a deformation amount of 350% is preferably 5.0 N/mm ² or less. Adhesives that meet the above characteristics have a high refractive index, can maintain flexibility above a predetermined level even in low-temperature environments, and can be fully deformed at high speeds. Therefore, it is suitable for use in applications involving large deformations. In several ideal forms, the stress at 350% deformation can be 4.9N/mm ² or less, 4.8N/mm ² or less, 4.7N/mm ² or less, or 4.6N/mm ² or less, or 4.5 N/mm ² or less, 4.4N/mm ² or less, 4.3N/mm ² or less, 4.2N/mm 2 or less, 4.1N/mm ² or less, 4.0N/mm ² or less, 3.9N/mm ^{2 or} less, 3.8N /mm ² or less, 3.7N/mm ² or less, 3.6N/mm ² or less, 3.5N/mm 2 or less, 3.4N/mm ² or less, 3.3N/mm ² or less, 3.2N/mm ^{2 or} less, 3.1N/ mm ² or less, 3.0N/mm ² or less, 2.9N/mm ² or less, 2.8N/mm ² or less, 2.7N/mm 2 or less, 2.6N/mm ² or less, 2.5N/mm ^{2 or} less, 2.4N/mm ² or less, 2.3N/mm ² or less or 2.2N/mm ² or less. The lower limit of the above-mentioned stress at 350% deformation can theoretically be 0.0N/mm ² or more, and in several ideal forms it can be 0.1N/mm ² or more, 0.2N/mm ² or more, or 0.3N/mm ² or more, 0.4N/mm ² or more, 0.5N/mm ² or more, 0.6N/mm ² or more, 0.7N/mm ² or more, 0.8N/mm ² or more, 0.9N/mm ² or more, 1.0N/mm ² Above, 1.1N/mm ² and above, 1.2N/mm ² and above, 1.3N/mm ² and above, 1.4N/mm 2 and above, 1.5N/mm ^{2 and} above, 1.6N/mm ² and above, 1.7N/mm ² and above , 1.8N/mm ² or more, 1.9N/mm ² or more, 2.0N/mm ² or more, 2.1N/mm 2 or more or 2.2N/mm ^{2 or} more, it can also be 2.3N/mm ² or more, 2.4N/mm 2 or more ² or more, 2.5N/mm ² or more, 2.6N/mm ² or more, 2.7N/mm ² or more, 2.8N/mm ² or more, 2.9N/mm ² or more, 3.0N/mm ² or more, 3.1N/mm ² Above, 3.2N/mm ² and above, 3.3N/mm ² and above, 3.4N/mm ² and above, 3.5N/mm 2 and above, 3.6N/mm ² and above, 3.7N/mm ^{2 and} above, 3.8N/mm ² and above , 3.9N/mm ² or more, 4.0N/mm ² or more, 4.1N/mm ² or more, 4.2N/mm ² or more, 4.3N/mm ² or more, 4.4N/mm ² or more, 4.5N/mm ² or more or 4.6N/mm ² or more. An adhesive having the above-mentioned stress of 350% deformation can be flexible and have moderate cohesion.

In several aspects, the stress S (-20°C) at a deformation amount of 350% in the deformation test of the adhesive at a temperature of -20°C and a speed of 300mm/min is the same as that at a temperature of 25°C and a speed of 300mm/min. In a deformation test conducted under conditions of 10 minutes, the ratio of stress S (25°C) at a deformation amount of 350% (S(-20°C)/S(25°C)) should be 50 or less. Adhesives that satisfy the above characteristics can provide stable performance in a wide temperature range, including low-temperature areas. In several ideal aspects, the above ratio (S(-20°C)/S(25°C)) may be 49 or less, 48 or less, 47 or less, 46 or less, 45 or less, 44 or less, 43 or less, 42 or less, 41 or less, 40 or less, 39 or less, 38 or less, 37 or less, 36 or less, 35 or less, 34 or less, 33 or less, 32 or less or 31 or less. It can also be 30 or less, 29 or less, 28 or less, 27 or less or 26 or less. , 25 or less, 24 or less, 23 or less, 22 or less, 21 or less, 20 or less, 19 or less, 18 or less, 17 or less, 16 or less or 15 or less. The lower limit of the above ratio (S(-20°C)/S(25°C)) is usually 0 or more. In several ideal aspects, it can be 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 6 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 or 15 or more, it can also be 16 or more, 17 or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 Above, above 23, above 24, above 25, above 26, above 27, above 28, above 29, above 30, or above 31.

The deformation test carried out under the above conditions of -20°C or 25°C and speed of 300mm/min can be carried out specifically by the following method. [Deformation test] Cut the adhesive layer into a length of 300mm and a cross-sectional area of 1mm ² in width, and roll the adhesive layer into a cylinder in an environment of 23°C and 50% RH to obtain a test piece. Using a tensile testing machine (manufactured by Shimadzu Corporation, device name "Precision Universal Testing Machine Autograph AG-X plus 5kN"), the above test pieces were tested at -20°C, the distance between the clamps is 100mm, and the tensile speed is 300mm/min. The deformation test (tensile test) determines the SS curve and evaluates whether the test piece is deformed (elongated) by 350% or more. When the test piece is deformed by more than 350%, measure the stress at 350% deformation [N/mm ² ]. In the above deformation test, adhesives that can deform more than 350% at -20°C are judged as adhesives that can withstand large deformation. Moreover, except that the temperature of the said deformation test was changed to 25 degreeC, the deformation test was carried out in the same manner as above, and the stress [N/ ^mm2 ] at 350% deformation was measured. From the obtained results, the stress S (-20°C) at a deformation amount of 350% in the deformation test conducted at a temperature of -20°C and a speed of 300mm/min was calculated, and the stress S (-20°C) at a temperature of 25°C and a speed of 300mm/min was calculated. The ratio of stress S (25°C) at 350% deformation in the deformation test carried out (S(-20°C)/S(25°C)). In addition, when the thickness of the adhesive layer is small, in order to improve operability, etc., a test piece adjusted to a thickness of 5µm or more (for example, about 5µm~200µm) can be used to perform the above deformation test. The thickness of the test piece can be adjusted, for example, by appropriately laminating the adhesive layer. Alternatively, the same adhesive composition used to form the adhesive layer to be measured can be used to produce a test piece with a thickness that is easy to perform a deformation test, and the above-mentioned deformation test can be performed on the test piece. The above-mentioned deformation test can be carried out using a test piece with a thickness of about 10µm to 50µm, for example. Also, during testing, it is advisable to apply powder on the adhesive surface of the clamping area to remove the influence of the adhesive in advance.

The 350% deformability of the adhesive at a temperature of -20°C and a speed of 300mm/min, the stress at 350% and the ratio (S(-20°C)/S(25°C)) can be selected to form a base polymerization The composition of the monomer components of the product, setting the weight average molecular weight (Mw) of the base polymer, selecting the type or amount of plasticizer, whether to use a cross-linking agent and selecting the type and amount, whether to use additives, and selecting the type and amount Wait to adjust.

(adhesive layer) The adhesive disclosed here (for example, an adhesive film (adhesive film), an adhesive layer of an adhesive sheet) can be obtained by applying (for example, coating) an adhesive composition to an appropriate surface and then hardening the composition. form. The adhesive composition can be coated by, for example, a gravure roll coater, a reverse roll coater, a contact roll coater, a dip roll coater, a rod coater, a blade coater, a spray coater, or other conventional coating machines. cloth machine to implement.

The thickness of the adhesive (specifically, the thickness of the adhesive film (adhesive film), such as the thickness of the adhesive layer constituting the adhesive sheet) is not particularly limited, but may be, for example, 3 μm or more. In several aspects, the thickness of the adhesive (layer) is appropriate, for example, 5 µm or more, it can be 10 µm or more, it can be 15 µm or more, it can be 20 µm or more, it can be 30 µm or more, it can be 50 µm or more, it can be Above 70µm or above 85µm. By increasing the thickness of the adhesive (layer), the adhesion will tend to increase. Furthermore, in several aspects, the thickness of the adhesive (layer) may be, for example, 300µm or less, 250µm or less, 200µm or less, 150µm or less, or 120µm or less. In several ideal aspects, the thickness of the adhesive (layer) is 100µm or less, preferably 75µm or less, more preferably 70µm or less, 50µm or less, or 30µm or less. From the viewpoint of thinning the adhesive sheet, etc., it is advantageous that the thickness of the adhesive (layer) is not too large. In addition, thin adhesives (layers) tend to have excellent compliance with adherends. The technology disclosed here can be suitably implemented when the thickness of the adhesive (layer) is in the range of 3µm to 200µm (preferably 5µm to 100µm, more preferably 5µm to 75µm), for example. In addition, when it is an adhesive sheet with a first adhesive layer and a second adhesive layer on the first and second sides of the base material, the thickness of the above-mentioned adhesive (layer) can be at least the thickness of the first adhesive layer. . The thickness of the second adhesive layer can also be selected from the same range. In addition, when it is an adhesive sheet without a base material, the thickness of the adhesive sheet is consistent with the thickness of the adhesive layer.

＜Adhesive sheet＞ According to this specification, an adhesive sheet having an adhesive layer is provided. The adhesive constituting the above-mentioned adhesive layer may be an adhesive formed from any adhesive composition disclosed herein (for example, a hardened product of the adhesive composition). The above-mentioned adhesive sheet may be an adhesive sheet with a base material in the form of having the above-mentioned adhesive layer on one or both sides of a non-releasable base material (support base material), or may be in the form of a form in which the above-mentioned adhesive layer is maintained on a release liner. Such adhesive sheets without base materials (that is, adhesive sheets without non-releasable base materials, typically adhesive sheets composed of adhesive layers). The concept of adhesive sheet mentioned here may include adhesive tape, adhesive label, adhesive film, etc. The adhesive sheet disclosed here can be in roll form or in single sheet form. Or it may be an adhesive sheet further processed into various shapes.

An example of the structure of a double-sided adhesive type baseless adhesive sheet (baseless double-sided adhesive sheet) is shown in Figures 1 and 2. The adhesive sheet 1 shown in FIG. 1 has a structure in which both sides 21A and 21B of an adhesive layer 21 without a base material are respectively protected by release liners 31 and 32 having at least the adhesive layer side serving as the release surface. The adhesive sheet 2 shown in Figure 2 has a structure in which one surface (adhesive surface) 21A of the adhesive layer 21 without a base material is protected by a release liner 31 with both sides serving as release surfaces, and can be configured as follows: During winding, the other surface (adhesive surface) 21B of the adhesive layer 21 is in contact with the back surface of the release liner 31 , so that the other surface 21B is also protected by the release liner 31 . From the viewpoint of being able to be bent repeatedly and conforming to the softness of the adherend, the technology disclosed here is suitable for implementation in the form of an adhesive sheet composed of an adhesive layer without a base material. The above-mentioned 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.

The adhesive sheet disclosed here may, for example, have the cross-sectional structure schematically shown in FIG. 3 . The adhesive sheet 3 shown in FIG. 3 includes a support base material 10 and a first adhesive layer 21 and a second adhesive layer 22 respectively supported by the first surface 10A and the second surface 10B of the support base material 10 . Both the first surface 10A and the second surface 10B are non-releasable surfaces (non-releasable 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, respectively. That is, the adhesive sheet 3 is configured in the form of a double-sided adhesive sheet (double-sided adhesive sheet). The adhesive sheet 3 before use has a structure in which the first adhesive surface 21A and the second adhesive surface 22A are each protected by release liners 31 and 32 having at least the adhesive surface side as a releasable surface (release surface). Alternatively, the release liner 32 may be omitted, and a release liner 31 with both sides serving as release surfaces may be used, and the adhesive sheet 3 may be wound so that the second adhesive surface 22A contacts the back surface of the release liner 31. The second adhesive surface 22A is also protected by the release liner 31 .

The technology disclosed here is suitable for fixing or joining components (such as optical components) in the form of the above-mentioned double-sided adhesive sheet without a base material or with a base material. Alternatively, although not particularly illustrated, the adhesive sheet disclosed here may be in the form of a single-sided adhesive sheet with a base material having an adhesive layer on only one side of a non-releasable base material (support base material). As an example of the form of the single-sided adhesive sheet, there is a form that does not include either the first adhesive layer 21 or the second adhesive layer 22 in the structure shown in FIG. 3 .

In several aspects, the haze value of the adhesive sheet can be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, 0.9% or less, or 0.8%. below, it can be 0.5% or below, or 0.3% or below. The highly transparent adhesive sheet can be suitably used in applications that require high light transmittance (such as optical applications) or applications that require the performance of the adherend to be well visible through the adhesive sheet. The lower limit of the haze value of the adhesive sheet is not particularly limited. From the perspective of improving transparency, the smaller the haze value, the better. On the other hand, in several aspects, the haze value may be, for example, 0.05% or more, or 0.10% or more, taking into account the refractive index or adhesive properties. The haze value of the adhesive sheet can be measured using the same method as the haze value of the adhesive layer described above. The above-mentioned haze value of the adhesive sheet can be obtained by selecting the composition of the above-mentioned adhesive layer, etc. or by selecting the type of base material or the thickness of the base material in a structure having a base material.

In several aspects, the total light transmittance of the adhesive sheet is preferably above 85.0% (for example, above 88.0%, above 90.0%, or above 90.0%). The highly transparent adhesive sheet can be suitably used in applications that require high light transmittance (such as optical applications) or applications that require the performance of the adherend to be well visible through the adhesive sheet. Practically, 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 sheet can be about 94% or less, about 93% or less, or about 92% or less, taking into account the refractive index or adhesive properties. The total light transmittance of the adhesive sheet can be measured using the same method as the measurement of the total light transmittance of the adhesive layer described above. The total light transmittance of the adhesive sheet can be obtained by selecting the composition of the above-mentioned adhesive layer or by selecting the type of base material or the thickness of the base material in a composition having a base material.

(peel strength) The peeling strength of the adhesive sheet to the glass plate is not particularly limited. In several aspects, the peeling strength of the adhesive sheet to the glass plate is, for example, 0.1N/25mm or more, or 0.5N/25mm or more. In several ideal aspects, the above-mentioned peeling strength to the glass plate is above 1.0N/25mm, 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. The adhesive disclosed herein can still exert the stable adhesive force as mentioned above even if it contains a plasticizer. As mentioned above, an adhesive sheet having a peeling strength of a glass plate or more than a predetermined value is suitable for joining or fixing glass members, for example. The upper limit of the peel strength is not particularly limited, but may be, for example, 30 N/25 mm or less, 25 N/25 mm or less, or 20 N/25 mm or less. In addition, when the adhesive sheet is an adhesive sheet without a base material and is composed only of an adhesive layer, the above-mentioned peeling strength to the glass plate may be the peeling strength of the adhesive to the glass plate.

Here, the above-mentioned peel strength is controlled by the following method: After pressing the alkali glass plate as the adherend and leaving it in an environment of 23°C and 50% RH for 30 minutes, the peeling angle is 180 degrees, and the The peel strength was measured under the conditions of elongation speed of 300mm/min. During measurement, an appropriate substrate (such as a polyethylene terephthalate (PET) film with a thickness of about 25µm to about 50µm) may be attached to the adhesive sheet of the measurement object for reinforcement if necessary. More specifically, the peel strength can be measured according to the method described in the Examples mentioned later.

(Thickness of adhesive sheet) The thickness of the adhesive sheet (adhesive sheet without base material or adhesive sheet with base material) disclosed here can be, for example, 1000 µm or less, 350 µm or less, 200 µm or less, 120 µm or less, 75 µm or less, or Can be below 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, 15 µm or more, 25 µm or more, 80 µm or more, or 130 µm or more. In addition, the thickness of the adhesive sheet means the thickness of the portion attached to the adherend. For example, in the adhesive sheet 3 having the structure shown in FIG. 3 , the thickness refers to the thickness from the first adhesive surface 21A to the second adhesive surface 22A, and does not include the thickness of the release liners 31 and 32 .

＜Support base material＞ Several forms of adhesive sheets may be in the form of an adhesive sheet with an adhesive layer on one or both sides of a supporting base material. The material of the supporting base material is not particularly limited and can be appropriately selected according to the purpose of use or usage pattern of the adhesive sheet. Non-limiting examples of base materials that can be used include: polyolefin films mainly composed of polyolefins such as polypropylene (PP) or ethylene-propylene copolymer, polyethylene terephthalate (PET), polyethylene Plastic films such as polyester films whose main components are polyesters such as butylene terephthalate (PBT) and polyethylene naphthalate (PEN), and polyvinyl chloride films whose main components are polyvinyl chloride; Foam sheets 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.) alone or blended, etc.; Japanese paper, Dowling paper, kraft paper, crepe paper and other paper types; aluminum foil, copper foil Metal foil, etc. It can also be the base material composed of these composites. Examples of the composite base material include a base material having a structure 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.

Various film substrates may be suitably used in several aspects. The above-mentioned film base material may be a porous base material such as a foam film or a non-woven sheet, or may be a non-porous base material, or may be a structure in which a porous layer and a non-porous layer are laminated. base material. In several aspects, the above-mentioned film base material may suitably use one that includes an independent and shape-maintainable (self-standing or non-dependent) resin film as the base film. Here, the "resin film" refers to a resin film that has a non-porous structure and typically does not contain substantially bubbles (no holes). Therefore, the above-mentioned resin film is a concept that can be distinguished from a foam film or a nonwoven fabric. As the above-mentioned resin film, one that is independent and can maintain its shape (self-standing type or non-dependent type) can be suitably used. The above-mentioned resin film may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

Examples of resin materials constituting the resin film include: polyester; polyolefin; polycyclic olefin derived from monomers having aliphatic ring structures such as norphenylene structure; nylon 6, nylon 66, partially aromatic polyamide and other polyamides. Polyamide (PA); transparent polyimide (CPI) and other polyamide (PI); polyamide imide (PAI); polyether ether ketone (PEEK); polyether styrene (PES); polyethylene Phenyl sulfide (PPS); polycarbonate (PC); polyurethane (PU); ethylene-vinyl acetate copolymer (EVA); polytetrafluoroethylene (PTFE) and other fluororesins; acrylic resin; triacetate Cellulose-based polymers such as cellulose (TAC); polyarylate; polystyrene; polyvinyl chloride; polyvinylidene chloride and other resins.

The resin film may be formed using a resin material containing only one type of the resin, or may be formed using a mixture of two or more types of resin materials. The above-mentioned resin film may be unstretched or stretched (eg, 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, cyclic olefin polymer (COP) film, CPI film, TAC film, etc. From the viewpoint of strength or dimensional stability, examples of ideal resin films include PET films, PEN films, PPS films and PEEK films. From the viewpoint of ease of acquisition, etc., PET film and PPS film are particularly suitable, and among these, PET film is preferred.

In the resin film, light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slipping agents, etc. can be blended as needed within the range that does not significantly hinder the effects of the present invention. Anti-adhesive agents and other well-known additives. The amount of additives blended is not particularly limited and can be appropriately set according to the purpose of the adhesive sheet.

The manufacturing method of 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 appropriately used.

The base material may be substantially composed of the base film. Alternatively, the above-mentioned base material may also include an auxiliary layer in addition to the above-mentioned base film. Examples of the above-mentioned auxiliary layer include an optical property adjustment layer (for example, a colored layer, an antireflection layer), a printing layer or a laminated layer for imparting a desired appearance to the base material, an antistatic layer, and a primer layer. , peeling layer and other surface treatment layers.

In some aspects, a light-transmissive base material (hereinafter also referred to as a light-transmissive base material) can be suitably used as the supporting base material. In this way, an adhesive sheet with a light-transmissive base material can be formed. The total light transmittance of the light-transmissive base material may be, for example, greater than 50%, or may be greater than 70%. In several ideal aspects, the total light transmittance of the supporting substrate is above 80%, preferably above 90%, and may also be above 95% (for example, 95~100%). The above total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used. A suitable example of the light-transmissive base material is a light-transmissive resin film. The above-mentioned light-transmissive base material 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 usage pattern of the adhesive sheet. The thickness of the base material can be, for example, 500µm or less. From the viewpoint of the rationality or processability of the adhesive sheet, it is preferably 300µm or less, 150µm or less, 100µm or less, 50µm or less, or 25µm or less. It can also be 10µm or less. If the thickness of the base material becomes smaller, the compliance with the surface shape of the adherend will tend to increase. In addition, from the viewpoint of handleability or processability, the thickness of the base material 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 the formation of a primer by applying a primer (primer) as required. Conventionally known surface treatments such as coatings. The surface treatment may be a treatment used to improve the anchoring property of the adhesive layer to the substrate. The composition of the primer used to form the undercoat layer is not particularly limited and can be appropriately selected from publicly known materials. The thickness of the primer layer is not particularly limited, but is usually about 0.01µm~1µm, and preferably about 0.1µm~1µm. Other treatments that can be performed on the substrate according to the needs include antistatic layer formation treatment, coloring layer formation treatment, printing treatment, etc. These treatments may be applied individually 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 (adhesive surface) of the adhesive layer is in contact with the release surface of the release liner. Therefore, according to this specification, an adhesive sheet with a release liner (adhesive product) is provided, which includes any of the adhesive sheets disclosed herein and a release liner having a release surface that contacts the adhesive surface of the adhesive sheet.

The release liner is not particularly limited. For example, a release liner that has a release layer on the surface of a liner base material such as a resin film or paper (can be paper laminated with resins such as polyethylene), or a release liner made of fluorine Release liners made of resin films made of low-adhesion materials such as polymers (polytetrafluoroethylene, etc.) or polyolefin resins (polyethylene, polypropylene, etc.). Since it has 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. Examples include polyethylene (PE) film, polypropylene (PP) film, polybutylene film, polybutadiene film, and polymethylpentene film. , polyvinyl chloride film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-ethyl acetate copolymer film, etc. The above-mentioned release layer can be formed using, for example, polysiloxane-based release treatment agents, long-chain alkyl-based release treatment agents, olefin-based release treatment agents, fluorine-based release treatment agents, fatty amide-based release treatment agents, molybdenum sulfide, or dioxide. Well-known stripping agents such as silicon powder.

＜Use＞ The adhesives or adhesive sheets disclosed here are not limited in their uses and can be used for various purposes. The adhesive or adhesive sheet disclosed here is an adhesive having a high refractive index and flexibility, 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 panel. It is particularly suitable as an adhesive or adhesive sheet for foldable displays or rollable displays in equipment (optical equipment) such as input devices such as panels. For example, it can be suitably used as a mechanism for joining, fixing, and protecting members with high refractive index in foldable displays and rollable displays. The adhesive or adhesive sheet disclosed here has a high refractive index and is flexible enough to withstand repeated bending operations. Therefore, it can well adapt to repeated bending while being attached to a foldable display or a rollable display. The adherend (folding monitor, etc.). Examples of the attachment object in the usage form include glass members such as window glass and cover glass that can be used for foldable displays or roll-up displays. Moreover, the adhesive or adhesive sheet disclosed here can easily conform to and adhere closely to the surface of a curved surface such as a three-dimensional shape of a portable electronic device, and is therefore suitable for use in electronic devices with such a curved surface. In addition, the adhesive also has improved stability of properties such as elastic modulus. The above-mentioned portable electronic devices are sometimes used in high-temperature environments, and the internal space may be heated due to the heat generated by the electronic components. Therefore, there are great advantages in using adhesives or adhesive sheets with good stability as mentioned above.

Examples of the above-mentioned portable electronic devices also include: mobile phones, smart phones, tablet computers, notebook computers, various wearable devices (such as watches, wristbands worn on the wrist, straps or hangings, etc. Modular types that are attached to a part of the body, eye-mounted types including eyeglass types (single-eyed or double-eyed; including head-mounted types), clothes that are attached to shirts, socks, hats, etc. in the form of accessories, for example models, earphones, which are ear-worn types that are attached to the ears, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), computers (electronic computers, etc.), portable games Computers, electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In addition, in this specification, the so-called "portable" is not enough just to be portable, but also refers to portability to the extent that an individual (standard adult) can carry it relatively easily.

The material (adherent material) to which the adhesive or adhesive sheet disclosed here can be attached is not particularly limited, and examples include copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc. Or metal materials such as alloys containing two or more of these, or polyimide resins, acrylic resins, polyether nitrile resins, polyether ester resins, polyester resins (PET resins, Polyethylene naphthalate resin, etc.), polyvinyl chloride resin, polyphenylene sulfide resin, polyether ether ketone resin, polyamide resin (so-called arylamide resin, etc.), polyarylene resin Various resin materials (typically plastic materials) such as ester resins, polycarbonate resins, cellulose polymers such as cellulose diacetate and cellulose triacetate, vinyl butyral polymers, and liquid crystal polymers, Alumina, zirconia, alkali glass, alkali-free glass, quartz glass, carbon and other inorganic materials, etc. The adhesive or adhesive sheet disclosed here can be used by being attached to a member (for example, an optical member) made of the above-mentioned materials.

The member or material to which the adhesive or adhesive sheet disclosed herein is attached (at least one adherend in a double-sided adhesive sheet) may be made of a material with a higher refractive index than a general acrylic adhesive. The refractive index of the adherend material is, for example, 1.50 or more. There are adherend materials with a refractive index of 1.55 or more or 1.58 or more, and there are also adherend materials with a refractive index of 1.62 or more (for example, about 1.66). The adherend material with high refractive index is typically a resin material. More specifically, polyester-based resins such as PET, polyimide-based resins, arylamide resins, polyphenylene sulfide-based resins, polycarbonate-based resins, etc. may be used. For such materials, the effect of using the adhesive or adhesive sheet disclosed here (suppressing the reflection of light caused by a difference in refractive index) can be suitably exerted. The upper limit of the refractive index of the adherend material is, for example, 1.80 or less, and may be 1.70 or less. The adhesive or adhesive sheet disclosed here is suitable for use in the state of being attached to an adherend (such as a component) with a high refractive index as mentioned above. A suitable example of the adherend is a resin film with a refractive index of 1.50 to 1.80 (preferably 1.55 to 1.75, such as 1.60 to 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 which the adhesive or adhesive sheet is attached (at least one adherend in a double-sided adhesive sheet) may be light-transmissive. In the case of 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 can be easily obtained. The total light transmittance of the adherend can be, for example, greater than 50%, preferably more than 70%. In several ideal aspects, the total light transmittance of the adherend is above 80%, preferably above 90%, and may be above 95% (for example, 95~100%). The adhesive or adhesive sheet disclosed here is suitable for use in a state where it is attached to an adherend (for example, an optical component) whose total light transmittance is higher than a predetermined value. The above total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used.

In several ideal aspects, the adherend (such as a component) to which the adhesive or adhesive sheet is attached can have the above-mentioned refractive index and the above-mentioned total light transmittance. Specifically, the adhesive or adhesive sheet disclosed herein can be suitably attached to a film with a refractive index of more than 1.50 (for example, more than 1.55, more than 1.58, more than 1.62, about 1.66, etc.) and a total light transmittance of more than 50% (for example, 70 % or more, preferably 80% or more, more preferably 90% or more, and more preferably 95% or more) of the adherend, such as a component. The effects of the technology disclosed herein are particularly suitable when attached to the component.

An example of a preferred use is optical use. More specifically, for example, the adhesive sheet disclosed here can be suitably used for optical purposes such as lamination of optical members (for optical member lamination) or manufacturing of products using the optical members (optical products). Use adhesive or optical adhesive sheet.

The above-mentioned optical components refer to components with optical properties (such as polarization, light refraction, light scattering, light reflectivity, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.). The above-mentioned optical member is not particularly limited as long as it has optical properties. Examples thereof include members constituting machines (optical machines) such as display devices (image display devices) and input devices, or members used in such machines. Examples thereof include polarizers. plate, wavelength plate, phase difference plate, optical compensation film, brightness enhancement film, light guide plate, reflective film, anti-reflective film, hard coating (HC) film, impact absorption film, antifouling film, photochromic film, dimming film , transparent conductive film (ITO film), design film, decorative film, surface protection plate, lens, lens, color filter, transparent substrate, or further laminated components (these are sometimes collectively referred to as " "Functional film"), etc. In addition, the above-mentioned "plate" and "film" are respectively taken to include those in the form of plate, film, sheet, etc., for example, "polarizing film" is taken to include "polarizing plate" or "polarizing sheet", and " "Light guide plate" is taken to include "light guide film" or "light guide sheet". In addition, the above-mentioned "polarizing plate" is assumed to include a circularly polarizing plate.

Examples of the display device include a liquid crystal display device, an organic EL display device, a micro LED (µLED), a mini LED (miniLED), a PDP, and electronic paper. In addition, the input device may include a touch panel or the like.

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

The technology disclosed here can be suitably used, for example, to join optical films such as films or fluorescent films having one or more functions such as light transmission, reflection, diffusion, waveguide, light concentrating, diffraction, etc. to other optical members (which may be other optical films). Among them, in the bonding of optical films that have at least one of the functions of light waveguide, light condensation, and diffraction, the entire bonding layer should have a high refractive index, which makes it an ideal application target of the technology disclosed here.

The adhesive disclosed here can be suitably used for bonding optical films such as light guide films, diffusion films, fluorescent films, toning films, cylindrical films, lenticular films, microlens array films, and the like. In these applications, from the viewpoint of the tendency of miniaturization of optical components or the improvement of performance, there is a demand for thinning or improvement of light capture efficiency. The adhesives disclosed herein can be suitably utilized as adhesives that meet these requirements. More specifically, for example, when joining a light guide film or a diffusion film, adjusting (for example, making the refractive index high) the refractive index of the adhesive (layer) serving as the joining layer can contribute to thinning. The bonding of fluorescent films can improve light capture efficiency (which can also be regarded as luminous efficiency) by appropriately adjusting the refractive index difference between the fluorescent emitter and the adhesive. For the bonding of toning films, by appropriately adjusting the refractive index of the adhesive to reduce the refractive index difference with the toning pigment, scattering components can be reduced and help improve light transmittance. When bonding lenses, cylindrical films, microlens array films, etc., controlling the diffraction of light by appropriately adjusting the refractive index of the adhesive can help improve brightness and/or viewing angles.

The adhesive or adhesive sheet disclosed here can be suitably used in a state of being attached to an adherend with a high refractive index (which may be a layer or member with a high refractive index, etc.), and can inhibit the interaction with the adherend. Interface reflection. The adhesive agent or 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 mentioned above. In addition, from the viewpoint of improving the uniformity of appearance, the thickness uniformity 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, 5 µm or less, 4 µm or less, or 2 µm or less), from the viewpoint of suppressing coloration or color unevenness caused by interference of reflected light, reflection at the interface is suppressed. One thing is particularly meaningful. An example of the use aspect is the following aspect: it can be used in a polarizing plate with a retardation layer including a polarizer, a first retardation layer, and a second retardation layer in this order. The bonding of the above-mentioned first phase difference layer and/or the bonding of the above-mentioned first phase difference layer and the above-mentioned second phase difference layer.

In addition, since the adhesive or adhesive sheet disclosed here is suitable for increasing the refractive index, it can be suitably attached to a light-emitting layer (for example, a high-refractive light-emitting layer mainly composed of inorganic materials) of an optical semiconductor or the like. used in any situation. By reducing the refractive index difference between the luminescent layer and the adhesive (layer), reflection at their interfaces can be suppressed and the light capture efficiency can be improved. The adhesive or adhesive sheet that can be used in the above-mentioned aspect should preferably have an adhesive (layer) with a high refractive index. In addition, from the viewpoint of improving brightness, the adhesive or adhesive sheet is preferably low in coloration. It is also advantageous from the viewpoint of suppressing unintentional coloring caused by adhesives or adhesive sheets.

In addition, in this specification, a self-luminous element means a light-emitting element that can control the luminous brightness by the value of the flowing current. The self-luminous element can be constructed as a single body or as an assembly. 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 self-luminous element as a component. Examples of the above-mentioned light-emitting devices also include light source module devices used as lighting (such as planar light-emitting modules) or display devices formed with pixels, but are not limited thereto.

The adhesive disclosed here can be suitably used as a cover for lens surfaces of microlenses and other lens members used as components of cameras, light-emitting devices, etc. (for example, microlenses constituting a microlens array film or microlenses for cameras, etc.) A coating layer, a bonding layer with 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. Since the adhesive disclosed here is suitable for high refractive index, even a lens with a high refractive index (for example, a lens made of a high refractive index resin or a lens with a surface layer made of a high refractive index resin) can still be used. Reduce the refractive index difference with the lens. This is advantageous from the viewpoint of thinning the lens and products including the lens, and can also help suppress aberrations or increase the Abbe number. The adhesive disclosed here can also be used as a lens resin by itself, for example, in the form of being filled in the recesses or voids of an appropriate transparent member.

The method of bonding optical components using the adhesive or adhesive sheet disclosed herein is not particularly limited. For example, it can be in the following manner: (1) The optical components are bonded to each other through the adhesive or adhesive sheet disclosed herein. or (2) the optical component is bonded to a component other than the optical component through the adhesive or adhesive sheet disclosed herein; or (3) the adhesive sheet disclosed herein includes the optical component. The adhesive sheet is bonded to an optical member or a member other than the optical member. Furthermore, in the aspect (3) above, the adhesive sheet having the form of an optical member may be, for example, an adhesive sheet in which the support is an optical member (for example, an optical film). The adhesive sheet in the form of including an optical member as a support can also be regarded as an adhesive optical member (for example, an adhesive optical film). Furthermore, when the adhesive sheet disclosed here is an adhesive sheet having a support and the above-mentioned functional film is used as the above-mentioned support, the adhesive sheet disclosed here can also be regarded as having this on at least one side of the functional film. "Adhesive functional film" with an adhesive layer revealed.

From the above, based on the technology disclosed here, there is provided a laminated body including the adhesive sheet disclosed here and a member to which the adhesive sheet is attached. The member to which the adhesive sheet can be attached may have the refractive index of the adherend material mentioned above. In addition, the difference between the refractive index of the adhesive sheet and the refractive index of the member (refractive index difference) may be the refractive index difference between the adherend and the adhesive sheet. The components constituting the laminated body are as described above using the above-mentioned components, materials, and adherends, so the description will not be repeated.

Example Various embodiments of the present invention will be described below, but the specific examples shown are not intended to limit the present invention. In addition, in the following description, "parts" and "%" indicating the usage amount or content are based on weight unless otherwise specified.

＜Example 1＞ (Preparation of acrylic polymer solution) Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet pipe and a cooler, the monomer component phenoxybenzyl acrylate (manufactured by Kyeisha Chemical Co., Ltd., trade name "LIGHT ACRYLATE POB-A" ", refractive index: 1.566, hereinafter referred to as "POB-A") 99 parts and 2-acryloxyethyl succinate (manufactured by Kyeisha Chemical Co., Ltd., trade name "HOA-MS(N)", below 1 part (denoted as "HOA-MS"), 0.2 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator, and ethyl acetate as a polymerization solvent, introduce nitrogen gas while stirring slowly, and place the contents in the flask The liquid temperature was kept near 60°C and polymerization reaction was carried out for 6 hours to prepare a solution of acrylic polymer P1. The Mw of acrylic polymer P1 is 500,000.

(Preparation of adhesive composition) The solution of the above-mentioned acrylic polymer P1 was diluted with ethyl acetate to a polymer concentration of 30%, and trimethylpentaphenyltrisiloxy as plasticizer A1 was added to 334 parts of the solution (100 parts of non-volatile components). 20 parts of alkane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name "HIVAC F-5", molecular weight: 546, refractive index: 1.575, liquid at 20°C) and an epoxy cross-linking agent (Mitsubishi gas) as a cross-linking agent Chemical Co., Ltd., trade name "TETRAD C", 0.3 parts of 1,3-bis(N,N-diepoxypropylaminomethyl)cyclohexane) and stirred to prepare the acrylic adhesive in this example composition.

(Production of adhesive sheets) The acrylic adhesive composition prepared above was coated on the polysiloxane-treated surface of a single-sided polysiloxane-treated polyethylene terephthalate (PET) film R1 (thickness: 50 μm) at 130°C. Heat for 2 minutes to form an adhesive layer with a thickness of 20µm. Then, the polysilicone-treated side of the PET film R2 (thickness 25 μm), which is polysilicone-treated on one side, is bonded to the surface of the above-mentioned adhesive layer. A substrate-free double-sided adhesive sheet composed of the adhesive layer is obtained in the above manner. Both sides of the adhesive sheet are protected by PET films (release liners) R1 and R2.

＜Example 2＞ In addition to changing the composition of the monomer components to 95 parts of POB-A, 2 parts of lauryl acrylate (LA), 2 parts of 2-ethylhexyl acrylate (2EHA) and 1 part of 4-hydroxybutyl acrylate (4HBA), A solution of acrylic polymer P2 was prepared in the same manner as the acrylic polymer solution in Example 1. The Mw of acrylic polymer P2 is 500,000. The solution of the above-mentioned acrylic polymer P2 was diluted with ethyl acetate to a polymer concentration of 30%, and 20 parts of the above-mentioned plasticizer A1 (HIVAC F-5) was added to 334 parts of the solution (100 parts of non-volatile components), as The cross-linking agent is 0.3 parts of a non-cyclic bifunctional isocyanate cross-linking agent (manufactured by Tosoh Co., Ltd., trade name "Coronate 2770", hexamethylene diisocyanate (HDI) allophanate body), as Mix 2 parts of acetyl acetone as a cross-linking retarder and 1 part of a 1% ethyl acetate solution of iron (III) acetyl acetonate as a cross-linking catalyst (0.01 part of non-volatile components) to prepare the acrylic acid in this example. It is an adhesive composition. Except 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 the adhesive sheet in Example 1.

＜Example 3＞ A solution of acrylic polymer P3 was prepared in the same manner as the acrylic polymer solution in Example 1, 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 acrylic polymer P3 is 500,000. The solution of the above-mentioned acrylic polymer P3 was diluted with ethyl acetate to a polymer concentration of 30%, and 40 parts of the above-mentioned plasticizer A1 (HIVAC F-5) and the above-mentioned plasticizer were added to 334 parts of the solution (100 parts of non-volatile components) 0.5 parts of isocyanate cross-linking agent, 2 parts of acetyl acetone as a cross-linking retarder, 1 part of a 1% ethyl acetate solution of iron (III) acetyl acetonate as a cross-linking catalyst (0.01 part of non-volatile components) and Stir and mix to prepare the acrylic adhesive composition of this example. Except 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 the adhesive sheet in Example 1.

＜Example 4＞ Except that the composition of the monomer components was changed to 95 parts of POB-A, 3 parts of 4HBA and 2 parts of HOA-MS, an acrylic polymer P4 was prepared in the same manner as the acrylic polymer solution in Example 1. solution. The Mw of acrylic polymer P4 is 500,000. The solution of the above-mentioned acrylic polymer P4 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of the solution (100 parts of non-volatile components) were added with polyethylene glycol benzoate (polyethylene glycol benzoate) as the plasticizer A2. Manufactured by Sanyo Chemical Industry Co., Ltd., trade name "Sumflex EB-300", molecular weight: 538, refractive index: 1.515, liquid at 20°C, hereinafter referred to as "EB-300") 60 parts, the above-mentioned isocyanate cross-linking agent 0.3 2 parts of acetyl acetone as a cross-linking retardant, 1 part of a 1% ethyl acetate solution of iron acetyl acetonate (III) as a cross-linking catalyst (0.01 part of non-volatile components) and stir and mix to prepare this product. An example is an acrylic adhesive composition. Except using the obtained acrylic adhesive composition, the adhesive sheet of each example (a double-sided adhesive sheet without a base material composed of an adhesive layer) was produced in the same manner as the adhesive sheet in Example 1.

＜Example 5＞ Use 60 parts of the above-mentioned plasticizer A2 (EB-300) instead of 20 parts of the above-mentioned plasticizer A1 (HIVAC F-5), and change the usage amount of the above-mentioned epoxy cross-linking agent to 0.5 parts. The acrylic adhesive composition of this example was prepared in the same manner as in Example 1, and the obtained acrylic adhesive composition was used. In addition, the adhesive sheet in Example 1 was produced in the same manner as in Example 1. The adhesive sheet in this example (a double-sided adhesive sheet without a base material composed of an adhesive layer).

＜Example 6＞ Except that the composition of the monomer components was changed to 98 parts of POB-A, 1 part of 4HBA, and 1 part of HOA-MS, an acrylic polymer P5 was prepared in the same manner as the acrylic polymer solution in Example 1. solution. The Mw of acrylic polymer P5 is 500,000. Dilute the solution of the above-mentioned acrylic polymer P5 with ethyl acetate to a polymer concentration of 30%, and add 30 parts of the above-mentioned plasticizer A2 (EB-300) and the above-mentioned isocyanate to 334 parts of the solution (100 parts of non-volatile components) It is composed of 0.1 part of cross-linking agent, 2 parts of acetyl acetone as a cross-linking retardant, and 1 part of a 1% ethyl acetate solution of iron (III) acetyl acetonate as a cross-linking catalyst (0.01 part of non-volatile components) and stirred Mix to prepare the acrylic adhesive composition of this example. Except 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 the adhesive sheet in Example 1.

＜Examples 7~8＞ Prepare the acrylic polymer solution in the same manner as in Example 1, except that the composition of the monomer components is changed to 85 parts of POB-A, 14 parts of n-butyl acrylate (BA), and 1 part of acrylic acid (AA). A solution of acrylic polymer P6 was obtained. Furthermore, 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, an acrylic polymer P7 was prepared in the same manner as the acrylic polymer solution in Example 1. solution. The Mw of acrylic polymers P6 and P7 are 500,000 each. The solution of the above-mentioned acrylic polymer P6 or P7 was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts (100 parts of non-volatile components) of the solution were added with 3-phenoxybenzyl alcohol as plasticizer A3. (Manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 200, refractive index: 1.591, liquid at 20°C) 60 parts and 0.1 part (Example 7) or 0.5 part (Example 8) of the above-mentioned epoxy cross-linking agent are stirred and mixed. The acrylic adhesive compositions of each example were prepared. In addition to using the obtained acrylic adhesive composition, the adhesive sheets of each example (double-sided adhesive sheets without a base material composed of an adhesive layer) were produced in the same manner as the adhesive sheet in Example 1.

＜Evaluation method＞ (Transfer amount of plasticizer into gas phase) About 1 g of the plasticizer (measurement sample) used in each example was dropped into an aluminum cup, and weighed to 0.01 mg unit (W0g) using an electronic balance in an environment of 23°C and 45% RH. Next, the cup containing the above-mentioned measurement sample was kept in an oven at 130°C for 1 hour. Use an oven that has sufficient capacity for the measurement sample and can be heated while exhausting the gas. In this evaluation, an oven manufactured by espec was used. After maintaining the temperature at 130°C for 1 hour, take out the cup containing the measurement sample from the oven, return to room temperature, and then weigh (W1g). Substituting the weight W0 [g] of the measurement sample before oven heating and the weight W1 [g] of the measurement sample after oven heating into the formula: 1-W1/W0, the transfer value of the measurement sample at 130°C is obtained. Amount of gas phase transfer [%]. The measurement was performed on 3 samples (n=3), and the average value was used.

(Heating loss of plasticizer in adhesive) The acrylic adhesive compositions of each example were applied to the silicone-treated surface of the single-sided silicone-treated PET film R1, and heated at 130°C for 3 minutes to form an adhesive layer with a thickness of 20 µm. Then, the polysilicone-treated surface of the PET film R2, which is polysilicone-treated on one side, is bonded to the surface of the above-mentioned adhesive layer. Peel off one of the release liners from the adhesive layer (release liner/adhesive layer/release liner) with the release liner, and keep it in an oven at 130°C for 1 hour. Use an oven that has sufficient capacity for the measurement sample and can be heated while exhausting the gas. In this evaluation, an oven manufactured by espec was used. For the adhesive before and after heating in the oven, liquid chromatography (LC) was measured under the following conditions. From the above LC results, calculate the amount of plasticizer contained in the adhesive before and after heating, and from the weight ratio, calculate the decrease [%] of the plasticizer in the adhesive after being kept in an environment of 130°C for 1 hour. ]. The measurement was performed on 3 samples (n=3), and the average value was used. In addition, in this measurement, before the above-mentioned adhesive is subjected to LC measurement, the plasticizer monomer is subjected to LC measurement, a calibration curve is prepared, and the plasticizer in the adhesive is quantified based on the calibration curve. [LC measurement conditions] Take about 0.01g of adhesive, add 2mL of chloroform, and shake overnight. 8 mL of acetonitrile was added to the solution to reprecipitate the polymer component, and the supernatant was filtered with a 0.45 μm membrane filter. The obtained filtrate was appropriately diluted and injected into an analysis device (HPLC Prominence manufactured by Shimadzu Corporation) to perform measurement. Column: GL Sciences, Inertsil ODS-3 (4.6mmφ×250mm, 5µm) Tube string temperature: 40℃ Column flow: 1.0mL/min Eluent: ultrapure water/acetonitrile gradient conditions Injection volume: 1µL Detector: DAD (select 190nm~400nm, 272nm)

(refractive index) For the adhesive layer (double-sided adhesive sheet without base material) of each example, an Abbe refractometer (manufactured by ATAGO CO., LTD., model "DR-M4") was used at a measurement wavelength of 589 nm 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 laminated to a thickness of approximately 1.5 mm, and punched into a disc shape with a diameter of 7.9 mm, which was used as a measurement sample. Dynamic viscoelasticity was measured under the following conditions using "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific. From the measurement results, the storage elastic modulus G' [Pa] of the adhesive at each temperature (-20°C, 0°C and 25°C) is calculated. Furthermore, the temperature corresponding to the peak temperature of the loss tangent tan δ (loss elastic modulus G"/storage elastic modulus G') in the above dynamic viscoelasticity measurement is defined as the glass transition temperature (Tg) [°C] of the adhesive. [Measurement conditions] Transformation mode: twist Measuring frequency: 1Hz Temperature range: -50℃~150℃ Heating rate: 5℃/min Shape: parallel plate 7.9mmφ

(Change in elastic modulus after holding at 130°C for 1 hour) The acrylic adhesive compositions of each example were applied to the silicone-treated surface of the single-sided silicone-treated PET film R1, and heated at 130°C for 3 minutes to form an adhesive layer with a thickness of 20 µm. Then, the polysilicone-treated surface of the PET film R2, which is polysilicone-treated on one side, is bonded to the surface of the above-mentioned adhesive layer. Peel off one of the release liners from the adhesive layer (release liner/adhesive layer/release liner) with the release liner, and keep it in an oven at 130°C for 1 hour. Use an oven that has sufficient capacity for the measurement sample and can be heated while exhausting the gas. In this evaluation, an oven manufactured by espec was used. The above-mentioned adhesive (layer) kept at 130°C for 1 hour was laminated to a thickness of about 1.5mm, and then autoclaved (0.5MPa, 50°C, 15 minutes) to make each layer adhere closely. For the measurement sample obtained in the above manner, the storage elastic modulus G' at -20°C after being kept in an environment of 130°C for 1 hour was determined by the same method as the above-mentioned storage elastic modulus G' ( G'1)[Pa]. Then, find the ratio of the storage elastic modulus G'1 [Pa] obtained above to the storage elastic modulus G'0 [Pa] measured in advance at -20°C before being kept in an environment of 130°C for 1 hour (G '1/G'0).

(Total light transmittance and haze) A test piece in which the adhesive layer of each example was bonded to alkali-free glass (thickness 0.8~1.0mm, total light transmittance 92%, haze 0.4%) was used, and a haze meter (manufactured by Murakami Color Technology Research Institute) was used. "HM-150"), measure the total light transmittance and haze of the above test piece under a measurement environment of 23°C. The total light transmittance and haze of the above-mentioned alkali-free glass are subtracted from the measured value as the total light transmittance [%] and haze [%] of the adhesive (layer). Regarding the base-less adhesive sheet composed of the above-mentioned 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 to glass plate) In a measurement environment of 23°C and 50% RH, peel off the release liner from one side of the adhesive sheet, laminate a PET film with a thickness of 50µm as a backing, and cut it 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 2kg roller was pressed back and forth once on the surface of an alkali glass plate (manufactured by Shonami Glass Industry Co., Ltd., thickness 1.35mm, frosted blue glass) as the adherend. After leaving it in the same 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 uses the "Tensile Compression Testing Machine, TG-1kN" manufactured by Minebea Co., Ltd. In addition, when it is a single-sided adhesive sheet with a base material, it is not possible to use a PET film as a backing.

The summary and evaluation results of the adhesives of each example are shown in Table 1.

[Table 1]

As shown in Table 1, Examples 1 to 6 use the following adhesive composition. The adhesive composition includes: an acrylic polymer polymerized using an aromatic ring-containing monomer (A1); and a plasticizer, It has more than 2 rings containing double bonds and the transfer amount into the gas phase at 130°C is less than 10%; Examples 1 to 6 have high refractive index, and by including a plasticizer, the elastic modulus is reduced, And the elastic modulus change (G'1/G'0) after holding at 130°C for 1 hour is within the range of 50 or less. That is, the adhesives in these examples have high refractive index and improved flexibility, and can still exhibit stable characteristics against temperature changes. On the other hand, Examples 7 to 8 use materials with a transfer amount of more than 10% into the gas phase at 130°C as plasticizers. It can be confirmed that the elasticity of Examples 7 to 8 after being maintained at 130°C for 1 hour The modulus change (G'1/G'0) is greater than 50, and the characteristics of Examples 7 to 8 tend to change due to temperature changes. It can be seen from the above results that an acrylic polymer polymerized using an aromatic ring-containing monomer (A1) and an acrylic polymer having two or more double bond-containing rings and the transfer amount to the gas phase at 130°C is 10% or less. The adhesive composition of the plasticizer can form an adhesive with a high refractive index, increased flexibility, and improved stability of properties.

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 technology described in the scope of the patent application includes the specific examples illustrated above with various modifications and changes.

1,2,3: Adhesive sheet 10: Support base material 10A:Side 1 10B:Side 2 21: Adhesive layer, first adhesive layer 21A: Adhesive surface, first adhesive surface 21B:Adhesive surface 22: 2nd adhesive layer 22A: 2nd 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 according to another embodiment. FIG. 3 is a cross-sectional view schematically showing the structure of an adhesive sheet according to another embodiment.

(without)

Claims (8)

An adhesive composition including an acrylic polymer and a plasticizer; The monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1); The aforementioned plasticizer has more than two rings containing double bonds and the amount of transfer into the gas phase at 130°C is less than 10%. Such as the adhesive composition of claim 1, wherein the molecular weight of the aforementioned plasticizer is 350 or more. The adhesive composition of claim 1 or 2, wherein the plasticizer contains more than 10 parts by weight relative to 100 parts by weight of the acrylic polymer. An adhesive formed from the adhesive composition according to any one of claims 1 to 3. An adhesive including an acrylic polymer and a plasticizer; The monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1); The aforementioned plasticizer has more than 2 rings containing double bonds; and After the aforementioned adhesive is maintained in an environment of 130°C for 1 hour, the amount of the aforementioned plasticizer in the adhesive is reduced to less than 5%. For example, for the adhesive in claim 4 or 5, the storage elastic modulus G'1 of the adhesive at -20°C after being kept at 130°C for 1 hour is the same as the storage elastic modulus G'1 before being kept at 130°C for 1 hour. The storage elastic modulus G'0 ratio (G'1/G'0) at -20°C is 50 or less. For example, the adhesive according to any one of the requirements 4 to 6 has a peeling strength of 1.0N/25mm or more to the glass plate. For example, the adhesive according to any one of requirements 4 to 7 has a total light transmittance of more than 85%.

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