TW202144526A - Pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet - Google Patents

Abstract

Provided is a pressure-sensitive adhesive composition which comprises: an acrylic polymer (A) including an aromatic-ring-containing monomer (m1) as monomer units; and an additive (HRO) that is an organic material having a higher refractive index than the acrylic polymer (A). Also provided is a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition.

Description

Adhesive composition, adhesive and adhesive sheet

The present invention relates to an adhesive composition, an adhesive and an adhesive sheet. This application claims to rely on Japanese Patent Application No. 2020-052408 filed on March 24, 2020, Japanese Patent Application No. 2020-166426 filed on September 30, 2020, and Japanese Patent Application No. 2020-166426 filed on March 2021 The priority of Japanese Patent Application No. 2021-049059 filed on March 23, and the entire contents of these applications are incorporated herein by reference.

Generally speaking, adhesives (also known as pressure-sensitive adhesives, the same below) exhibit a soft solid (viscoelastic) state at a temperature near room temperature, and have the ability to be easily adhered to the adherend by pressure. nature. Taking advantage of this property, adhesives are widely used for the purpose of bonding, fixing, and protection in various industrial fields ranging from home appliances to automobiles, various machinery, electrical equipment, and electronic equipment. An example of the application of the adhesive includes the application of bonding polarizing films, retardation films, cover window members, various other light-transmitting members, and other members in display devices such as liquid crystal display devices and organic EL display devices. Patent documents 1 and 2 are mentioned as technical documents about the adhesive for optical members. prior art literature Patent Literature

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 propose an adhesive composition containing a (meth)acrylate polymer as a main component, and an adhesive obtained by crosslinking the adhesive composition, and the (meth)acrylate The polymer contains a monomer having a plurality of aromatic rings as a monomer unit. However, with the techniques described in Patent Documents 1 and 2, it is difficult to obtain an adhesive having a refractive index higher than that of the above-mentioned (meth)acrylate polymer. On the other hand, there is also known a technique for increasing the refractive index by mixing particles made of inorganic materials with high refractive index (for example, inorganic particles such as zirconia particles or titanium oxide particles) into resins to increase the refractive index. Adhesives are difficult to apply in the field of adhesives because the refractive index and adhesive properties (such as peel strength, flexibility, etc.) are in a trade-off relationship. In the case of adhesives for optical applications, there is also a concern that the optical properties may be lowered due to the incorporation of inorganic particles.

Therefore, an object of the present invention is to provide an adhesive whose refractive index has been raised by a method suitable for optical applications. Another related object is to provide an adhesive composition capable of forming the adhesive and an adhesive sheet comprising the adhesive.

MEANS TO SOLVE THE PROBLEM The adhesive composition provided according to this specification comprises: an acrylic polymer (A), which contains an aromatic ring-containing monomer (m1) as a monomer unit; and an additive (H _RO ), which is An organic material having a higher refractive index than the above-mentioned acrylic polymer (A). The acrylic polymer (A) containing the aromatic ring-containing monomer (m1) as a monomer unit may be one having a high refractive index. The adhesive composition disclosed herein, in addition to the acrylic polymer (A), further comprises an organic material additive (H _RO ) having a higher refractive index than the acrylic polymer (A), thereby forming An adhesive that balances the improvement of the refractive index and the suppression of the deterioration of the adhesive properties by the above-mentioned additive (H _{RO ).} In addition, the above-mentioned additive (H _RO ) can suppress the reduction of optical properties (eg, transmittance, haze, etc.), and at the same time, can effectively increase the refractive index of the adhesive.

In several ideal aspects of the technology disclosed herein (including adhesive compositions, adhesives, adhesive sheets and technologies implemented in other forms; the same applies hereinafter), the refractive index of the _{above-mentioned additive (H RO ) may be, for example,} Above about 1.60. The refractive index of the adhesive can be effectively increased _{by the additive (H RO} ) of an organic material whose refractive index is higher than that of the acrylic polymer (A) and whose refractive index satisfies about 1.60 or more.

In several aspects, the content of the above-mentioned additive (H _RO ) with respect to 100 parts by weight of the acrylic polymer (A) is, for example, greater than 0 parts by weight and not more than 60 parts by weight. _{The adhesive composition containing the additive (HRO} ) in the stated content is easy to form an adhesive that balances the use of the additive ( _HRO ) to increase the refractive index and suppress the decrease in the adhesive properties and/or the optical properties. good.

In several aspects, the above-mentioned additive (H _RO ) includes at least one compound selected from the group consisting of an aromatic ring-containing compound and a heterocyclic ring-containing compound. The techniques disclosed herein may suitably be practiced in the context of using the compound as an additive ( _HRO ).

In several aspects, the said additive (H _RO ) contains the compound which has two or more aromatic rings in 1 molecule. The techniques disclosed herein may suitably be practiced in the context of using the compound as an additive ( _HRO ). The above-mentioned compound having two or more aromatic rings in one molecule can be, for example, a compound that satisfies at least one of the following: (i) a structure containing two non-condensed aromatic rings that are directly chemically bonded; and (ii) a structure containing two aromatic rings that have been The structure of row condensation. The techniques disclosed herein may suitably be practiced in the context of using the compound as an additive ( _HRO ).

In some aspects, in the monomer component which comprises the said acrylic polymer (A), content of the said aromatic ring containing monomer (m1) is 50 weight% or more. The acrylic polymer (A) constituted by the monomer components of the above-mentioned composition can have a high refractive index, and thus is suitable as the acrylic polymer (A) in the technique disclosed herein.

In some aspects, in the monomer component which comprises the said acrylic polymer (A), content of the said aromatic ring containing monomer (m1) is more than 70 weight% and less than 100 weight%. Such an acrylic polymer (A) is preferable because it is easy to increase the refractive index, and it is easy to form an adhesive with good adhesive properties.

In some aspects, the glass transition temperature at which 50% by weight or more of the above-mentioned aromatic ring-containing monomer (m1) contained in the monomer component constituting the above-mentioned acrylic polymer (A) may be a homopolymer is 10° C. the following monomers. Thereby, even if the content of the aromatic ring-containing monomer (m1) in the above-mentioned monomer component is increased, it is easy to form an adhesive that balances high refractive index and adhesive properties. In addition, in the following, the Tg of the homopolymer of a monomer may be represented as the Tg of the said monomer.

In some desirable aspects, the above-mentioned aromatic ring-containing monomer (m1) includes an aromatic ring-containing monomer having two or more aromatic rings in one molecule (hereinafter also referred to as "monomer containing plural aromatic rings"). The refractive index of the adhesive can be effectively increased by using a monomer containing a plurality of aromatic rings. The aromatic ring-containing monomer (m1) may contain only one monomer containing a plurality of aromatic rings (for example, a monomer containing a plurality of aromatic rings whose Tg of a homopolymer is below 10°C), or a combination of two or more Included in monomers containing plural aromatic rings.

In some desirable aspects, the monomer having two or more aromatic rings in one molecule includes a monomer having a structural portion in which two aromatic rings are bonded via a linking group. For a monomer having the structural moiety containing a plurality of aromatic rings, for example, compared to the structural moiety, it is changed to a structural moiety (such as a biphenyl structure) that has a direct chemical bond between two aromatic rings and a plurality of aromatic rings. Monomers tend to have lower Tg homopolymers. By the aromatic ring-containing monomer (m1) containing the monomer containing a plurality of aromatic rings of the structure, flexibility and high refractive index suitable for use as an adhesive can be more balanced.

In some aspects, the monomer component constituting the above-mentioned acrylic polymer (A) may further contain a monomer (m2) having at least one of a hydroxyl group and a carboxyl group in addition to the above-mentioned aromatic ring-containing monomer (m1). . With the acrylic polymer (A) composed of the monomer components of the above-mentioned composition, it is easy to form an adhesive with good adhesive properties.

In addition, in the following, the aromatic ring-containing monomer (m1) may be expressed as "monomer (m1)", and the monomer (m2) having at least one of a hydroxyl group and a carboxyl group may be expressed as "monomer (m2)" )” situation.

The adhesive compositions disclosed herein may further comprise a cross-linking agent. By using a cross-linking agent, the adhesive can be given a moderate cohesiveness, and the rationality of the adhesive sheet during manufacture, processing, storage, and adhesion to the adherend can be improved.

According to this specification, an adhesive formed from any of the adhesive compositions disclosed herein can be provided. _{The adhesive contains the above-mentioned additive (H RO} ) in addition to the above-mentioned acrylic polymer (A), thereby suppressing the reduction of the adhesive properties and/or the optical properties while increasing the refractive index. In an ideal aspect, the refractive index of the above-mentioned adhesive may be, for example, greater than 1.570 (preferably 1.575 or more, more preferably 1.580 or more).

According to this specification, an adhesive sheet can be provided, which comprises an adhesive layer composed of an adhesive, and the adhesive is an adhesive formed from any of the adhesive compositions disclosed herein (for example, the refractive index is greater than 1.570, preferably 1.575 or more, preferably 1.580 or more adhesive). The pressure-sensitive adhesive sheet is suitably used in a state of being attached to a member (for example, an optical member).

In several aspects of the adhesive sheet disclosed herein, the haze value of the adhesive layer is 1.0% or less. The pressure-sensitive adhesive sheet having the above-mentioned high-transparency pressure-sensitive adhesive layer can be suitably used, for example, in the optical field.

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

Preferred embodiments of the present invention will be described below. Matters not specifically mentioned in this specification that are required for the implementation of the present invention can be understood by those skilled in the art based on the teachings on the implementation of the invention described in this specification and the technical common sense at the time of application. The present invention can be implemented according to the contents disclosed in this specification and common technical knowledge in the field. In addition, in the following drawings, the same code|symbol is attached|subjected to the member and the part which perform the same function and it demonstrates, and the repeated description may abbreviate|omit or simplify. In addition, the embodiment described in the drawings is schematic for clearly explaining the present invention, and does not completely accurately represent the size or scale of the product actually provided.

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

In this specification, the "base polymer" of the adhesive means the main component of the rubber-like polymer contained in the adhesive, and no limited explanation is given otherwise. The aforementioned rubbery polymer refers to a polymer that exhibits rubbery elasticity in a temperature region around room temperature. In addition, in this specification, the "main component" means containing more than 50 weight% of components unless it mentions in particular.

In the present specification, "acrylic polymer" means a polymer including, as a monomer unit constituting the polymer, a monomer unit derived from having at least 1 (methyl group) in 1 molecule Acryloyl monomer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. A typical example of an acrylic polymer may be a polymer in which the ratio of acrylic monomer in the total monomers that can be used for the synthesis of the polymer is greater than 50% by weight (preferably greater than 70% by weight, eg, greater than 90% by weight).

In addition, in this specification, a "(meth)acryloyl group" means an acryl group and a methacryloyl group in general. Similarly, "(meth)acrylate" means acrylate and methacrylate collectively, and "(meth)acrylic acid" means acrylic acid and methacrylic acid collectively. Therefore, the concept of the acrylic monomer mentioned here may include both a monomer having an acryl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

<Adhesive composition> As long as the adhesive composition disclosed herein can form an adhesive containing an acrylic polymer (A) (preferably an adhesive containing an acrylic polymer (A) as a base polymer), its form is not particularly limited. limited. The above-mentioned adhesive composition can be, for example, in the following various forms: a solvent-based adhesive composition in the form of an adhesive-forming component contained in an organic solvent, an active energy prepared so as to be hardened by active energy rays such as ultraviolet rays or radiation to form an adhesive Wire-curable adhesive composition, water-dispersible adhesive composition in which the adhesive-forming components are dispersed in water, and hot-melt adhesive composition that forms an adhesive when applied in a heated and melted state and cooled to around room temperature things etc.

(acrylic polymer (A)) The adhesive composition disclosed herein contains an acrylic polymer (A), and the acrylic polymer (A) contains an aromatic ring-containing monomer (m1) as a monomer unit. The said acrylic polymer (A) is a polymer which contains the aromatic ring containing monomer (m1) as a monomer component which comprises this acrylic polymer. Here, the term "monomer components constituting an acrylic polymer" in this specification means whether it is contained in the adhesive composition in the form of a pre-formed polymer (which may be an oligomer), or is not contained in the adhesive composition. The form of the polymerized monomer is included in the adhesive composition, and all of the monomers constitute the repeating unit of the acrylic polymer in the adhesive formed from the adhesive composition. That is, the monomer component which comprises an acrylic polymer can be contained in the said adhesive composition in any form of a polymer, a non-polymer, and a partial polymer. From the viewpoint of the ease of preparation of the adhesive composition, in several aspects, substantially all (for example, 95% by weight or more, preferably 99% by weight or more) of the monomer component is preferably contained in the form of a polymer. adhesive composition. An adhesive composition containing substantially all of the monomer components in the form of a polymer is also preferable from the viewpoint of easily forming an adhesive sheet with little strain or warpage.

(Single (m1)) As the monomer (m1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule can be used. The monomer (m1) may be used alone or in combination of two or more of these compounds.

As an example of the said ethylenically unsaturated group, a (meth)acryloyl group, a vinyl group, a (meth)allyl group etc. are mentioned. A (meth)acryloyl group is preferable from the viewpoint of polymerization reactivity, and an acryl group is preferable from the viewpoint of flexibility and adhesiveness. From the viewpoint of suppressing the decrease in the flexibility of the adhesive, a compound (ie, a monofunctional monomer) having a number of ethylenically unsaturated groups contained in one molecule of the monomer (m1) can be suitably used.

The number of aromatic rings contained in one molecule of the compound that can be used as the monomer (m1) may be one, or two or more. The upper limit of the number of aromatic rings contained in the monomer (m1) is not particularly limited, and may be, for example, 16 or less. In some aspects, the number of the above-mentioned aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6, from the viewpoint of the ease of preparation of the acrylic polymer (A) or the transparency of the adhesive. Hereinafter, 5 or less may be sufficient, 4 or less may be sufficient, 3 or less may be sufficient, and 2 or less may be sufficient.

The compound which can be used as the monomer (m1) has an aromatic ring such as a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a perylene structure); The carbocyclic ring such as the condensed ring, etc.; can also be, for example, a pyridine ring, a pyrimidine ring, a pyridine ring, a pyridine ring, a triazole ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring azole ring, thiazole ring, thiophene ring and other heterocycles. The heteroatom contained as a ring constituent atom in the above-mentioned heterocycle may be, for example, one or two or more kinds selected from the group consisting of nitrogen, sulfur, and oxygen. In several aspects, the heteroatoms that make up the heterocycle can be one or both of nitrogen and sulfur. The monomer (m1) may have a structure in which 1 or more carbocycles and 1 or more heterocycles have been condensed like a dinaphthothiophene structure, for example.

The above-mentioned aromatic ring (preferably a carbocyclic ring) may have one or more substituents on the atoms constituting the ring, or may not have a substituent. When having a substituent, the substituent may be exemplified by an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkoxy group, and a glycidoxy group. basis, but 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, the aromatic ring may be an aromatic ring having no substituents on the ring constituent atoms, or may have a ring constituent atom selected from an alkyl group, an alkoxy group, and a halogen atom (eg, bromine) Atom) is an aromatic ring of 1 or 2 or more substituents in the group. Moreover, the aromatic ring which the monomer (m1) has has a substituent on a ring constituent atom means that this aromatic ring has a substituent other than the substituent which has an ethylenically unsaturated group.

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

Examples of the compound that can be suitably used as the monomer (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylate and the aromatic ring-containing vinyl compound can be used alone or in combination of two or more. You may use it in combination of 1 type or 2 or more types of aromatic ring-containing (meth)acrylates and 1 type or 2 or more types of aromatic ring-containing vinyl compounds.

The content of the monomer (m1) in the monomer component constituting the acrylic polymer (A) is not particularly limited, and can be set to achieve both the desired refractive index and adhesive properties (eg peel strength, flexibility, etc.) and/or Or the adhesive layer of optical properties (such as total light transmittance, haze value, etc.). In several aspects, the content of the monomer (m1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, 60% by weight or more, or 70% by weight or more . From the viewpoint of easily obtaining a higher refractive index, in several ideal aspects, the content of the above-mentioned monomer (m1) may be, for example, more than 70% by weight, may be more than 75% by weight, may be more than 80% by weight, and may be It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. The upper limit of the content of the monomer (m1) in the above-mentioned monomer component is 100% by weight. From the viewpoint of balancing high refractive index with adhesive properties and/or optical properties, it is advantageous to set the content of the above-mentioned monomer (m1) to be less than 100 wt %, for example, preferably about 99 wt % or less, more preferably 98 wt %. % by weight or less may be 97% by weight or less, or may be 96% by weight or less. In several aspects, the content of the monomer (m1) may be 93 wt % or less, 90 wt % or less, 80 wt % or less, or 75 wt % or less. In some aspects that place more emphasis on adhesive properties and/or optical properties, the content of the above-mentioned monomer (m1) in the above-mentioned monomer component may be 70% by weight or less, 60% by weight or less, or 45% by weight. %the following.

In several aspects of the technology disclosed herein, a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be suitably used as the monomer in view of the ease of obtaining a higher refractive index enhancement effect. (m1). Examples of monomers having two or more aromatic rings in one molecule (hereinafter also referred to as "monomers containing plural aromatic rings") include: Monomers having a structure in which two or more non-condensed aromatic rings are bonded via a linking group. monomers, monomers with a structure in which two or more non-condensed aromatic rings are directly (that is, not separated by other atoms) chemically bonded, monomers with a condensed aromatic ring structure, monomers with a perylene structure, and a dinaphthothiophene structure monomers, monomers with dibenzothiophene structure, etc. The monomer containing a plurality of aromatic rings can be used alone or in combination of two or more.

The above-mentioned linking group can be, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (such as -O-(CH ₂ ) _n - group, where n is 1-3, and It is preferably 1), a thiooxyalkylene group (such as -S-(CH ₂ ) _n - group, where n is 1 to 3, and is preferably 1), a straight-chain alkylene group (that is, -(CH _{2 )} ) _n -group, where n is 1 to 6, and is preferably 1 to 3), the alkylene in the above-mentioned oxyalkylene, the above-mentioned thiooxyalkylene and the above-mentioned straight-chain alkylene has been partially halogenated or Fully halogenated groups, etc. From the viewpoint of the flexibility of the adhesive, etc., suitable examples of the above-mentioned linking group include an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain 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, benzyl benzyl (meth)acrylate, etc.

The above-mentioned monomers with a structure in which two or more non-condensed aromatic rings are directly chemically bonded can be, for example, (meth)acrylate containing biphenyl structure, (meth)acrylate containing triphenyl structure, and biphenyl containing vinyl group. Wait. Specific examples thereof 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 naphthalene, vinyl 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-naphthoxyethylacrylate, 2-(4-methoxy-1-naphthyloxy)ethyl (meth)acrylate, and the like.

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

Examples of the monomer having the above-mentioned dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include: (meth)acryloyloxymethyl dinaphthothiophene (for example, CH ₂ CH(R ¹ )C(O)OCH ₂ - A compound of the structure; here, R ¹ is a hydrogen atom or a methyl group), (meth)acryloyloxyethyl dinaphthothiophene (for example, a CH is bonded to the 5- or 6-position of the dinaphthothiophene ring) ₂ CH(R ¹ )C(O)OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ - structure; here, R ¹ is a hydrogen atom or a methyl group) , vinyl dinaphthothiophene (for example, a compound in which a vinyl group is bonded to the 5-position or 6-position of the naphthothiophene ring), (meth)allyloxydinaphthothiophene, and the like. In addition, the monomer system having a dinaphthothiophene structure is also included in the concept of the monomer having a condensed aromatic ring structure by including a naphthalene structure and a structure having a thiophene ring and two naphthalene structures that have been condensed .

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

As the monomer (m1) of the technique disclosed here, a monomer having one aromatic ring (preferably a carbocyclic ring) in one molecule can also be used. A monomer having one aromatic ring in one molecule contributes to, for example, improving the flexibility of the adhesive, adjusting the adhesive properties, improving transparency, and the like. In some aspects, from the viewpoint of raising the refractive index of the adhesive, a monomer having one aromatic ring per molecule is preferably used in combination with a monomer having a plurality of aromatic rings.

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

As the monomer (m1), a monomer having a structure in which an oxyethyl-extended chain is sandwiched between the ethylenically unsaturated group and the aromatic ring in the above-mentioned various aromatic ring-containing monomers can also be used. As described above, a monomer in which an oxyethyl-extended chain is sandwiched between an ethylenically unsaturated group and an aromatic ring can be regarded as an ethoxylate of the original monomer. The repeating number of the oxyethylidene unit (-CH ₂ CH ₂ O-) in the above oxyethylidene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, and for example, 1. Specific examples of ethoxylated aromatic ring-containing monomers include: ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated methyl Phenol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol di(meth)acrylate, and the like.

The content of the monomer containing a plurality of aromatic rings in the monomer (m1) 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 plurality of aromatic rings in the monomer (m1) may be, for example, 50% by weight or more, from the viewpoint of easily realizing an adhesive with a higher refractive index, and it is suitable It may be 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The monomer (m1) may be substantially 100% by weight of the monomer containing a plurality of aromatic rings. That is, as the monomer (m1), only one type or two or more types of monomers containing plural aromatic rings may be used. In addition, in several aspects, for example, considering the balance between high refractive index and adhesive properties and/or optical properties, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) may be less than 100% by weight, and may be It may be 98 wt % or less, 90 wt % or less, 80 wt % or less, or 65 wt % or less. In several aspects, in consideration of adhesive properties and/or optical properties, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) may be 70 wt % or less, may be 50 wt % or less, may be 25% by weight or less, or 10% by weight or less. The technique disclosed here can be implemented even if the content of the monomer containing a plurality of aromatic rings in the monomer (m1) is less than 5% by weight. A monomer containing a plurality of aromatic rings may not be used.

The content of the monomer containing a plurality of aromatic rings in the monomer component constituting the acrylic polymer (A) is not particularly limited, and can be set to achieve both desired refractive index and adhesive properties (such as peel strength, flexibility, etc. ) and/or an adhesive layer with optical properties (eg total light transmittance, haze value, etc.). The content of the monomer containing a plurality of aromatic rings in the 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 viewpoint of easily realizing an adhesive with a higher refractive index, the content of the monomer containing a plurality of aromatic rings in the above-mentioned monomer components may be, for example, greater than 35 wt %, preferably greater than 50 wt % %, may be greater than 70% by weight, may be greater than or equal to 75% by weight, may be greater than or equal to 85% by weight, may be greater than or equal to 90% by weight, or greater than or equal to 95% by weight. The content of the monomer containing a plurality of aromatic rings in the above-mentioned monomer components may be 100% by weight, but from the viewpoint of balancing high refractive index and adhesive properties and/or optical properties, it is advantageous to set it to less than 100% by weight is preferably about 99 wt % or less, preferably 98 wt % or less, can be 96 wt % or less, can be 93 wt % or less, can be 90 wt % or less, can be 85 wt % or less, can be 80 wt % or less The weight % or less may be 75 weight % or less. In several aspects, considering the adhesive properties and/or optical properties, the content of the monomers containing a plurality of aromatic rings in the above-mentioned monomer components may be 70 wt % or less, 50 wt % or less, and 25 wt % or less. % by weight or less may be 15% by weight or less, or may be 5% by weight or less. The technique disclosed here can be implemented even in the state in which the content of the monomer containing a plurality of aromatic rings in the above-mentioned monomer components is less than 3% by weight.

In several aspects of the technology disclosed herein, a high refractive index monomer may preferably be employed as at least a portion of the monomer (m1). 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, and more preferably about 1.550 or more. The upper limit of the refractive index of the high-refractive-index monomer is not particularly limited, but from the viewpoint of ease of preparation of the adhesive composition or ease of compatibility with flexibility suitable for use as an adhesive, it is, for example, 3.000 or less, and may be 2.500 Hereinafter, it may be 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less. A 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 under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C using an Abbe refractometer. The Abbe refractometer can use the type "DR-M4" manufactured by ATAGO or its equivalent. When there is a nominal value of the refractive index at 25°C provided from the manufacturer or the like, the nominal value can be used.

The above-mentioned high-refractive-index monomers can be appropriately used from among the compounds included in the concept of the aromatic ring-containing monomer (m1) disclosed herein (for example, the compounds and compound groups exemplified above) having such a refractive index. Specific examples include: m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthalene methacrylate (refractive index: 1.595, Tg of homopolymer: 31) ℃), ethoxylated o-phenylphenol acrylate (repetition number of oxyethylidene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6 ℃), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35 ℃), 6-acryloyloxymethyl dinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacrylooxymethyl dinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-propene Ethyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-propenyloxyethyldinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, Refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793), etc., but not limited thereto.

The content of the high-refractive-index monomer (that is, the aromatic-ring-containing monomer with a refractive index of about 1.510 or more, preferably about 1.530 or more, preferably about 1.550 or more) in the monomer (m1) is not particularly limited, for example, it can be 5% by weight or more, 25% by weight or more, 35% by weight or more, or 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 (m1) may be, for example, 50 wt % or more, preferably 70 wt % or more, or It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. The monomer (m1) may be substantially 100% by weight of the high refractive index monomer. In addition, in several aspects, for example, from the viewpoint of balancing high refractive index with adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer (m1) may be less than 100 wt %, and may be It may be 98 wt % or less, 90 wt % or less, 80 wt % or less, or 65 wt % or less. In several aspects, the content of the high refractive index monomer in the monomer (m1) may be 70 wt % or less, may be 50 wt % or less, and may be 25 wt % in consideration of adhesive properties and/or optical properties Hereinafter, it may be 15% by weight or less, or 10% by weight or less. The technique disclosed here can be implemented even in a state where the content of the high refractive index monomer in the monomer component (m1) is less than 5 wt %. It is also possible not to use a high refractive index monomer.

The content of the high-refractive-index monomer in the monomer component constituting the acrylic polymer (A) is not particularly limited, and can be set to achieve both the desired refractive index and adhesive properties (such as peel strength, flexibility, etc.) and/or Or the adhesive layer of optical properties (such as total light transmittance, haze value, etc.). The content of the high refractive index monomer in the 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 viewpoint of easily realizing an adhesive with a higher refractive index, the content of the high-refractive-index monomer in the above-mentioned monomer components may be, for example, greater than 35% by weight, preferably greater than 50% by weight, or It may be more than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The content of the high-refractive-index monomer in the above-mentioned monomer components may be 100% by weight, but from the viewpoint of balancing high refractive index and adhesive properties and/or optical properties, it is advantageous to set it to less than 100% by weight. 99 wt % or less, preferably 98 wt % or less, 96 wt % or less, 93 wt % or less, 90 wt % or less, 85 wt % or less, 80 wt % or less, It may be 75% by weight or less. In several aspects, in consideration of adhesive properties and/or optical properties, the content of the high-refractive index monomer in the monomer component may be 70 wt % or less, 50 wt % or less, or 25 wt % or less , may be 15 wt % or less, or 5 wt % or less. The technique disclosed here can be implemented even in the state where the content of the high-refractive-index monomer in the above-mentioned monomer components is less than 3% by weight.

In several desirable aspects of the technology disclosed herein, at least a part of the monomer (m1) is a homopolymer with a Tg of 10°C or less (preferably 5°C or less, or 0°C or less, preferably -10°C) Hereinafter, the aromatic ring-containing monomer (hereafter referred to as "monomer L") is more preferably -20°C or lower, for example, -25°C or lower. When increasing the aromatic ring-containing monomer (m1) in the monomer component (especially the aromatic ring-containing monomer (m1) corresponding to one or both of the above-mentioned monomers containing a plurality of aromatic rings and high-refractive index monomers )), the storage elastic modulus G' of the adhesive tends to increase substantially, but by using the monomer L as a part or all of the monomer (m1), the storage elastic modulus G' can be suppressed. rise. Thereby, the flexibility suitable as an adhesive can be maintained better, and the refractive index can be raised. The lower limit of the Tg of the monomer L is not particularly limited. Considering the balance with the refractive index raising effect, in several aspects, the Tg of the monomer L may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. The monomer L can be used alone or in combination of two or more.

As the monomer L, one having the Tg can be appropriately used from among the compounds included in the concept of the aromatic ring-containing monomer (m1) disclosed herein (for example, the compounds and compound groups exemplified above). A suitable example of the aromatic ring-containing monomer that can be used as the monomer L includes m-phenoxybenzyl acrylate (Tg of homopolymer: -35°C). Another suitable example is phenoxydiethylene glycol acrylate (Tg of homopolymer: -35°C).

The content of the monomer L in the monomer (m1) 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 L in the monomer (m1) may be, for example, 50 wt It may be 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. The monomer (A1) may be substantially the monomer L in 100% by weight. In addition, in several aspects, for example, from the viewpoint of balancing flexibility suitable for use as an adhesive and high refractive index, the content of the monomer L in the monomer (m1) may be less than 100% by weight, and may be 98% by weight. % by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 50% by weight or less, 25% by weight or less, or 10% by weight or less. The technique disclosed here can be implemented even in the state in which the content of the monomer L in the monomer (m1) is less than 5 wt %. Monomer L may not be used.

The content of the monomer L in the monomer component constituting the acrylic polymer (A) may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In several aspects, the content of the monomer L in the monomer component may be, for example, greater than 35 wt %, and may be greater than 50 wt %, from the viewpoint of easily obtaining an adhesive with a higher level of high refractive index and flexibility. %, may be greater than 70% by weight, may be greater than or equal to 75% by weight, may be greater than or equal to 85% by weight, may be greater than or equal to 90% by weight, or greater than or equal to 95% by weight. The content of the monomer L in the above-mentioned monomer components may be 100% by weight, but considering the balance between high refractive index and adhesive properties and/or optical properties, it is advantageous to set it to less than 100% by weight, and preferably about 99% by weight % or less, preferably 98 wt % or less, 96 wt % or less, 95 wt % or less, 93 wt % or less, 90 wt % or less, 85 wt % or less, 80 wt % or less % or less, and may be 75% by weight or less. In several aspects, the content of the monomer L in the above-mentioned monomer components may be 70 wt % or less, 50 wt % or less, 25 wt % or less, 15 wt % or less, or 5 wt % or less. % by weight or less. The technique disclosed here can be implemented even in the state where the content of the monomer L in the above-mentioned monomer components is less than 3% by weight.

In several aspects, from the viewpoint of the flexibility of the adhesive, it _{is advantageous for the glass transition temperature Tg m1 to} be about 20°C or lower, preferably 10°C or lower (eg, 5°C), depending on the composition of the monomers (m1). below), preferably 0°C or lower, more preferably -10°C or lower, may be -20°C or lower, or -25°C or lower. The lower limit of the glass transition temperature Tg _{m1 is not particularly limited.} Considering the balance with the refractive index raising effect, in several aspects, the glass transition temperature Tg _m1 may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. The technique disclosed herein can be suitably implemented even when the glass transition temperature Tg _m1 is, for example, -40°C or higher, -35°C or higher, -33°C or higher, -30°C or higher, or -25°C or higher.

Here, the glass transition temperature Tg _m1 according to the composition of the monomer (m1) means only the composition of the monomer (m1) in the monomer component constituting the acrylic polymer (A), and is obtained by the following Fox formula the Tg. The glass transition temperature Tg _m1 can be obtained by applying the below-described Fox formula only to the monomer (m1) among the monomer components constituting the acrylic polymer (A), and from each aromatic ring-containing monomer used as the monomer (m1). The glass transition temperature of the bulk homopolymer and the weight fraction of each aromatic ring-containing monomer in the total amount of monomers (m1) were calculated. In an aspect in which only one monomer is used as the monomer (m1), the Tg of the homopolymer of the monomer corresponds to the glass transition temperature Tg _m1 .

In several aspects, the aromatic ring-containing monomer (m1) can be combined with the monomer L (that is, the Tg of the homopolymer is 10°C or lower, preferably 5°C or lower, or 0°C or lower, preferably -10°C). ℃ or lower, more preferably -20 ℃ or lower, for example, -25 ℃ or less aromatic ring-containing monomer) and monomer H whose Tg is higher than 10 ℃ are used. The Tg of the monomer H may be higher than 10°C, higher than 15°C, or higher than 20°C, for example. By combining the monomer L and the monomer H, for example, in the composition with a large content of the aromatic ring-containing monomer (m1) in the monomer component, the high refractive index and flexibility of the adhesive can be taken into account at a higher level. . The usage-amount ratio of the monomer L and the monomer H can be set so that the effect can be appropriately exhibited, and is not particularly limited. For example, it is preferable to set the usage ratio of the monomer L to the monomer H so as to satisfy any one of the above-mentioned glass transition temperatures Tg _m1 .

In several aspects, the aromatic ring-containing monomer (m1) can be suitably selected from compounds that do not contain a structure in which two or more non-condensed aromatic rings are directly chemically bonded (eg, a biphenyl structure). For example, it is suitable to be an acrylic polymer composed of the following monomer components: the content of the 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, may also be 0% by weight). Limiting the amount of the compound containing two or more non-condensed aromatic rings that are directly chemically bonded as described above is advantageous from the viewpoint of realizing an adhesive that balances flexibility or adhesiveness with a high refractive index.

(Single (m2)) In some aspects of the technology disclosed herein, the monomer component constituting the acrylic polymer (A) may further contain a monomer (m2) in addition to the above-mentioned monomer (m1). The above-mentioned monomer (m2) is a monomer corresponding to at least one of a hydroxyl group-containing monomer (hydroxyl group-containing monomer) and a carboxyl group-containing monomer (carboxyl group-containing monomer). The above-mentioned hydroxyl group-containing monomer 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 monomer is a compound containing at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer (m2) contributes to the introduction of a crosslinking point into the acrylic polymer (A), or to impart appropriate cohesiveness to the adhesive. A monomer (m2) can be used individually by 1 type or in combination of 2 or more types. Monomer (m2) is typically a monomer that does not contain an aromatic ring.

As an example of the ethylenically unsaturated group which the monomer (m2) has, a (meth)acryloyl group, a vinyl group, a (meth)allyl group, etc. are mentioned. A (meth)acryloyl group is preferable from the viewpoint of polymerization reactivity, and an acryl group is preferable from the viewpoint of flexibility and adhesiveness. From the viewpoint of suppressing the decrease in the flexibility of the adhesive, a compound (ie, a monofunctional monomer) having a number of ethylenically unsaturated groups contained in one molecule can be suitably used as the monomer (m2).

Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxy (meth)acrylate Hexyl ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (methyl) ) acrylates and other hydroxyalkyl (meth)acrylates, but not limited thereto. Examples of the hydroxyl group-containing monomer that can be suitably used include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl acrylate (Tg: -15°C). From the viewpoint of improving the flexibility in the room temperature region, 4-hydroxybutyl acrylate having a lower Tg is preferred. In an ideal aspect, more than 50 wt % (eg, greater than 50 wt %, greater than 70 wt %, or greater than 85 wt %) of the monomer (m2) may be 4-hydroxybutyl acrylate. The hydroxyl group-containing monomer may be used alone or in combination of two or more.

In several aspects using a hydroxyl-containing monomer as a monomer (m2), the said hydroxyl-containing monomer may be 1 type or 2 or more types selected from the compound which does not have a methacryloyl group. Suitable examples of the hydroxyl group-containing monomer having no methacryloyl group include the aforementioned various hydroxyalkyl acrylates. For example, more than 50% by weight, more than 70% by weight or more than 85% by weight of the hydroxyl group-containing monomer used as the monomer (m2) is preferably hydroxyalkyl acrylate. By using hydroxyalkyl acrylate, a hydroxyl group that contributes to providing a crosslinking point or imparting moderate cohesiveness can be introduced into the acrylic polymer (A), compared to the case of using only the corresponding hydroxyalkyl methacrylate It is easier to obtain an adhesive with good softness or adhesion in the room temperature region.

In addition to acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate, examples of carboxyl group-containing monomers include itonic acid, maleic acid, fumaric acid, Crotonic acid and isocrotonic acid, etc., but not limited thereto. Examples of carboxyl group-containing monomers that can be suitably used include acrylic acid and methacrylic acid. The carboxyl group-containing monomer can be used alone or in combination of two or more. A hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used in combination.

The content of the monomer (m2) in the monomer component constituting the acrylic polymer (A) is not particularly limited, and can be set according to the purpose. In several aspects, the content of the above-mentioned monomer (m2) may be, for example, 0.01 wt % or more, 0.1 wt % or more, or 0.5 wt % or more. From the viewpoint of obtaining a higher use effect, in several aspects, the content of the above-mentioned monomer (A2) is preferably 1% by weight or more, may be 2% by weight or more, and may be 4% by weight. above. The upper limit of the content of the monomer (m2) in the monomer component is set so that the total of the content of the monomer (m1) does not exceed 100% by weight. In some aspects, the content of the above-mentioned monomer (m2) is suitable, for example, to be 30 wt % or less or 25 wt % or less, and it is easy to increase the refractive index by making the content of the monomer (m1) relatively large. From a viewpoint, it is preferably 20 wt % or less, more preferably 15 wt % or less, may be less than 12 wt %, may be less than 10 wt %, or may be less than 7 wt %.

In the aspect of using the hydroxyl group-containing monomer as the monomer (m2), the content of the hydroxyl group-containing monomer in the monomer component is not particularly limited, for example, it may be 0.01% by weight or more (preferably 0.1% by weight or more, 0.5% by weight or more). In several aspects, the content of the hydroxyl group-containing monomer is preferably 1 wt % or more of the monomer component, may be 2 wt % or more, and may be 4 wt % or more. The upper limit of the content of the hydroxyl group-containing monomer in the monomer component is set so that the total of the content of the monomer (m1) does not exceed 100% by weight. For example, it is appropriate to set it to 30% by weight or less or 25% by weight or less. From the viewpoint of making the content of the monomer (m1) relatively large to easily increase the refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, and may be less than 10% by weight , can also be less than 7% by weight.

In the aspect of using the carboxyl group-containing monomer as the monomer (m2), the content of the carboxyl group-containing monomer in the monomer component is not particularly limited, for example, it may be 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.3% by weight or more). In some aspects, the content of the carboxyl group-containing monomer may be 1% by weight or more, 2% by weight or more, or 4% by weight or more. The upper limit of the content of the carboxyl group-containing monomer in the monomer component is set so that the total amount of the monomer (m1) does not exceed 100% by weight. For example, it is appropriate to set it to 30% by weight or less or 25% by weight or less, and From the viewpoint of making the content of the monomer (m1) relatively large to easily increase the refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, or may be less than 10% by weight. weight%. In several aspects, from the viewpoint of improving the flexibility of the adhesive, it is advantageous to set the content of the carboxyl group-containing monomer to less than 7% by weight, preferably less than 5% by weight, and may be less than 3% by weight %, may be less than 1% by weight, or may be less than 0.5% by weight. The technique disclosed here can be suitably implemented, for example, in a state in which only a hydroxyl group-containing monomer is used as the monomer (m2), that is, in a state in which a carboxyl group-containing monomer is not used.

The total content of the monomer (m1) and the monomer (m2) in the monomer components constituting the acrylic polymer (A) may be, for example, 31% by weight or more, preferably 51% by weight or more, and may be 61% by weight or more , may be 71% by weight or more. In some aspects, the total content of the monomer (m1) and the monomer (m2) in the monomer components constituting the acrylic polymer (A) is from the viewpoint that the effects of these monomers are easily exerted appropriately, For example, it may be 76 wt % or more, preferably 81 wt % or more, 86 wt % or more, 91 wt % or more, 96 wt % or more, 99 wt % or more, or substantially 100 wt % %.

(single m3) The monomer components constituting the acrylic polymer (A) may also contain monomers other than the above-mentioned monomer (m1) and the above-mentioned monomer (m2) as required. An example of the said arbitrary component is an alkyl (meth)acrylate (henceforth "monomer (m3)"). The monomer (m3) helps to adjust the flexibility of the adhesive or improve the compatibility within the adhesive.

The monomer (m3) can be suitably used for an alkyl (meth)acrylate having a linear or branched alkyl group _{having 1 to 20 carbon atoms (ie, C 1-20) at the ester end.} Specific examples of (meth)acrylate C _1-20 alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and isopropyl (meth)acrylate , n-butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary 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, ten (meth)acrylate Diester, Tridecyl (meth)acrylate, Myristyl (meth)acrylate, Pentadecyl (meth)acrylate, Cetyl (meth)acrylate, Heptadecyl (meth)acrylate, (meth)acrylate base) octadecyl acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc., but not limited thereto.

In several aspects, at least a portion of the monomer (m3) may suitably be an alkane (meth)acrylate whose Tg of the homopolymer is below -20°C (preferably below -40°C, eg, below -50°C). base ester. The low Tg alkyl (meth)acrylate helps to improve the softness of the adhesive. The lower limit of Tg of the above-mentioned alkyl (meth)acrylate is not particularly limited, but may be, for example, -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the above-mentioned low Tg (meth)acrylate alkyl ester include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isononyl acrylate (iNA), and the like.

In some aspects using the monomer (m3), it is preferable that at least a part of the above-mentioned monomer (m3) is an alkyl acrylate from the viewpoint of flexibility, adhesiveness, and the like. For example, 50% by weight or more (preferably 75% by weight or more, more preferably 90% by weight or more) of the monomer (m3) is preferably an alkyl acrylate. As a monomer (m3), only 1 type or 2 or more types of alkyl acrylates may be used, and the aspect which does not use alkyl methacrylates may be sufficient.

In the aspect in which the monomer component contains the alkyl (meth)acrylate, the content of the alkyl (meth)acrylate in the monomer component can be set so that its use effect can be appropriately exhibited. In several aspects, the content of the above-mentioned alkyl (meth)acrylate may be, for example, 1 wt % or more, 3 wt % or more, 5 wt % or more, or 8 wt % or more. In several aspects, the content of the above-mentioned alkyl (meth)acrylate may be 15% by weight or more, 30% by weight or more, or 45% by weight or more. The upper limit of the content of the monomer (m3) in the monomer component is set so that the total of the content of other monomers does not exceed 100% by weight, for example, it may be less than 50% by weight. In several aspects, the content of the aforementioned monomer (m3) may be, for example, less than 35% by weight. Generally speaking, the refractive index of alkyl (meth)acrylate is low. Therefore, in order to increase the refractive index, the content of the monomer (m3) in the monomer component is limited and the content of the monomer (m1) is relatively large. is beneficial. From this point of view, it is advantageous that the content of the monomer (m3) is 24% by weight or less of the monomer components, preferably less than 23% by weight, more preferably less than 20% by weight, may be 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, and may also be less than 1% by weight. The monomer (m3) may not be used substantially.

(other monomers) The monomer components constituting the acrylic polymer (A) may also contain monomers other than the above-mentioned monomers (m1), (m2) and (m3) (hereinafter referred to as "other monomers") as required. The other monomers mentioned above can be used, for example, in order to adjust the Tg of the acrylic polymer (A), adjust the adhesive properties, improve the compatibility in the adhesive layer, and the like. These other monomers can be used alone or in combination of two or more.

As an example of the said other monomer, the monomer (functional group containing monomer) which has a functional group other than a hydroxyl group and a carboxyl group is mentioned. For example, as other monomers which can improve the cohesive force or heat resistance of the adhesive, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a cyano group-containing monomer, and the like can be mentioned. Moreover, as a monomer which can introduce a functional group which can become a crosslinking point in the acrylic polymer (A), or can contribute to the improvement of peeling strength or the compatibility in the adhesive layer, acyl group-containing monomers can be mentioned. Amine group monomers (such as (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amine group-containing monomers (such as amine ethyl (meth)acrylate, N,N- Dimethylaminoethyl (meth)acrylate, etc.), monomers with a nitrogen-containing ring (such as N-vinyl-2-pyrrolidone, N-(meth)acryloyl morpholin, etc.) , Imide-containing monomers, epoxy-containing monomers, ketone-containing monomers, isocyanate-containing monomers, alkoxysilicon-containing monomers, etc. In addition, among the monomers having a nitrogen atom-containing ring, for example, N-vinyl-2-pyrrolidone is also equivalent to an amide group-containing monomer. The same applies to the relationship between the above-mentioned monomer having a nitrogen atom-containing ring and an amine group-containing monomer.

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

When the above-mentioned other monomers are used, the usage amount thereof 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. In several aspects, the content of the above-mentioned other monomers in the monomer component may be, for example, about 35% by weight or less, from the viewpoint of easily exerting the refractive index raising effect obtained by using the monomer (m1). 25 wt % or less (eg, 0 to 25 wt %) is suitable, about 20 wt % or less (eg, 0 to 20 wt %), about 10 wt % or less, about 5 wt % or less, or about 1 wt % or less % by weight or less. The techniques disclosed herein may suitably be implemented in a state where the monomer component is substantially free of the other monomers described above.

In some aspects, the monomer component constituting the acrylic polymer (A) may be a composition in which the use amount of the methacryloyl group-containing monomer is kept below a predetermined level. The use amount of the methacryloyl group-containing monomer in the monomer component may be, for example, less than 5% by weight, may be less than 3% by weight, may be less than 1% by weight, or may be less than 0.5% by weight. Limiting the amount of the methacryloyl group-containing monomer to be used as described above is advantageous from the viewpoint of realizing an adhesive that balances flexibility or tackiness with a high refractive index. The monomer component constituting the acrylic polymer (A) may be a composition that does not contain a methacryloyl group-containing monomer (for example, a composition that is composed of only an acryl group-containing monomer).

In several aspects, from the viewpoint of inhibiting coloration or discoloration (eg, yellowing) of the adhesive, the amount of the carboxyl group-containing monomer used in the monomer component constituting the acrylic polymer (A) is preferably limited. The use amount of the carboxyl group-containing monomer in the monomer component may be, for example, less than 1% by weight, preferably less than 0.5% by weight, preferably less than 0.3% by weight, may be less than 0.1% by weight, or may be less than 0.05% by weight. If the amount of the carboxyl group-containing monomer is limited, corrosion of metal materials (such as metal wiring or metal films that may be present on the adherend) that can be in contact with or disposed adjacent to the adhesive disclosed herein is inhibited by inhibiting corrosion It is also beneficial from a point of view. The techniques disclosed herein can be suitably implemented in a state in which the above-mentioned monomer components do not contain a carboxyl group-containing monomer. For the same reason, in several aspects, the use amount of the monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, etc. in addition to the carboxyl group) in the monomer component constituting the acrylic polymer (A) is appropriate Industry restrictions. The use amount of the acid functional group-containing monomer in the monomer component of the aspect can be applied to the above-mentioned ideal use amount of the carboxyl group-containing monomer. The technique disclosed herein can be suitably implemented in a state in which the above-mentioned monomer components do not contain an acid group-containing monomer (that is, in a state in which the acrylic polymer (A) is acid-free).

(Glass Transition Temperature Tg _T ) In some aspects, among the monomer components constituting the acrylic polymer (A), it _{is appropriate that the glass transition temperature Tg T} of the monomer components is about 20° C. or lower depending on the composition of the monomer components , preferably below about 10°C, preferably below 0°C, below -10°C, below -20°C, below -25°C, below -28°C, and below -30°C. From the viewpoint of improving the flexibility of the adhesive, it is advantageous _{that the glass transition temperature Tg T is low.} In addition, the glass transition temperature Tg _T may be, for example, -60°C or higher, but from the viewpoint of easily increasing the refractive index of the adhesive, it is preferably -50°C or higher, more preferably higher than -45°C, and may be higher than - 40°C, higher than -35°C, higher than -25°C, higher than -15°C, or higher than -5°C.

Here, the glass transition temperature Tg _T means the glass transition temperature obtained by the Fox formula from the composition of the above-mentioned monomer components, unless otherwise specified. As shown below, Fox's formula 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 formula of Fox, Tg represents the glass transition temperature of the copolymer (unit: K), and Wi represents the weight fraction of the monomer i in the copolymer (the copolymerization ratio based on weight). ), Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i. As for the glass transition temperature of the homopolymer used for the calculation of Tg, the value described in known data such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) was used. Regarding the monomers with a plurality of values described in the above-mentioned Polymer Handbook, the highest value is used. When the Tg of the homopolymer is not described in the known data, the value obtained by the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 is used.

(Preparation method of acrylic polymer (A)) In the technique disclosed herein, the method for obtaining the acrylic polymer (A) composed of the above-mentioned monomer components is not particularly limited, and a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a suspension polymerization method can be appropriately used Various polymerization methods, such as photopolymerization methods, are well known as methods for synthesizing acrylic polymers. For example, a solution polymerization method can be suitably used. The polymerization temperature during solution polymerization can be appropriately selected according to the type of monomer and solvent 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 (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixed solvent of two or more selected from the following can be used: aromatic compounds (typically aromatic hydrocarbons) such as toluene; acetates such as ethyl acetate; hexane or cyclohexane Aliphatic or alicyclic hydrocarbons such as hexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (such as monohydric alcohols with 1 to 4 carbon atoms); tertiary butyl methyl Ethers such as ethers; ketones such as methyl ethyl ketone, etc.

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

In the above-mentioned polymerization, various chain transfer agents known in the past can be used as necessary. For example, thiols such as n-dodecyl mercaptan, tertiary dodecyl mercaptan, thioglycolic acid, and α-thioglycerol can be used. Alternatively, chain transfer agents containing no sulfur atoms (non-sulfur-tethered chain transfer agents) 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 Styrenics 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 about 0.01-1 weight part with respect to 100 weight part of monomer raw materials, for example.

The weight average molecular weight (Mw) of the said acrylic polymer (A) is not specifically limited, For example, it may be the range of about 10*10<^4>-500*10<^4> . From the viewpoint of adhesive properties, the Mw of the acrylic polymer (A) is preferably about 20×10 ⁴ to 400×10 ⁴ (preferably about 30×10 ⁴ to 150×10 ⁴ , for example, about 50×10 ^{4 ).} ~130×10 ⁴ ) range.

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

(Additives (H _RO)) as the technique disclosed herein of the additive (H _RO), a higher refractive index may be used an organic material at a relative relationship with the acrylic polymer (A) of. Here, the above-mentioned “H _RO ” means an organic material with a high refractive index (High Refractive index). By using the additive (H _RO ) in combination with the acrylic polymer (A), it is possible to achieve a suitable balance between refractive index and adhesive properties (peel strength, flexibility, etc.) and/or optical properties (total light transmittance, Haze value, etc.) adhesive. The organic material that can be used as the additive (H _RO ) can be a polymer or a non-polymer. Moreover, it may have a polymerizable functional group, and may not have a polymerizable functional group. The additives (H _RO ) may be used alone or in combination of two or more.

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

Refractive index additives (H _RO) n _B and the acrylic polymer (A) of _a difference of n, i.e. n _b -n _a (hereinafter known as "Δn _A") is set to be greater than zero. In several aspects, Δn _A may be, for example, 0.02 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more. By selecting the acrylic polymer (A) and the additive (H _RO ) so as to increase Δn _A , the effect of increasing the refractive index using the additive (H _{RO ) tends to increase.} In addition, from _{the viewpoint of the compatibility of the additive (H RO} ) in the adhesive layer, in several aspects, Δn _A may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40. below or below 0.35.

In several _aspects , the difference between the refractive index n _b of the additive (H _RO ) and the refractive index n _T of the adhesive layer comprising the additive (H RO ), that is, n _b −n _T (hereinafter also referred to as “Δn _B ”) is set to be greater than 0. In several aspects, Δn _B may be, for example, 0.02 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more. By selecting the composition of the adhesive layer and the additive (H _RO ) so as to increase Δn _B , the effect of increasing the refractive index using the additive (H _{RO ) tends to increase.} In addition, from the viewpoints of compatibility in the adhesive layer, transparency of the adhesive layer, etc., in several aspects, Δn _B may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, or may be is 0.40 or less or 0.35 or less.

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. In several aspects, the molecular weight of the _{additive (H RO ) is about less than} 10000 is suitable, preferably less than 5000, more preferably less than 3000 (eg less than 1000), may be less than 800, may be less than 600, may be less than 500, and may be less than 400. The fact that _{the molecular weight of the additive (H RO} ) is not too large is advantageous from the viewpoint of improving the compatibility in the adhesive layer. Moreover, the molecular weight of an additive (H _RO ) may be 130 or more, for example, and 150 or more may be sufficient as it. 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, may be 230 or more, and may be 250 or more More than 270 may be sufficient, 500 or more may be sufficient, 1000 or more may be sufficient, and 2000 or more may be sufficient. In several aspects, a polymer having a molecular weight of about 1,000 to 10,000 (eg, 1,000 or more and less than 5,000) can be used as an additive (H _RO ). The molecular weight of the additive (H _RO ) can be calculated based on the chemical structure of polymers with non-polymer or low degree of polymerization (such as about 2-5 polymers), or by matrix-assisted laser desorption free time-of-flight mass analysis 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 there is a nominal value of molecular weight provided from the manufacturer or the like, the nominal value can be used.

Examples of organic materials that can be an _{option for the additive (H RO} ) include organic compounds having an aromatic ring, organic compounds having a heterocyclic ring (which may be an aromatic ring or a non-aromatic heterocyclic ring), etc. etc. limited.

The aromatic ring possessed by 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 aroma possessed by the compound that can be used as a monomer (m1).} Ring the same thing to choose.

The said aromatic ring may have 1 or 2 or more substituents on a ring constituent atom, and may not have a substituent. When having a substituent, the substituent may be exemplified by an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkoxy group, and a glycidoxy group. basis, but not subject to such restrictions. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1 to 10, preferably 1 to 6, preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In several aspects, the aromatic ring may be an aromatic ring having no substituents on the ring constituent atoms, or may have a ring constituent atom selected from an alkyl group, an alkoxy group, and a halogen atom (eg, bromine) Atom) is an aromatic ring of 1 or 2 or more substituents in the group.

Examples of the aromatic ring-containing compound usable as the additive (H _RO ) include: a compound usable as a monomer (m1); an oligomer including a compound usable as a monomer (m1) as a monomer unit ; Removal of a group having an ethylenically unsaturated group (which may be a substituent bound to a ring constituent atom) or a portion of the group constituting an ethylenically unsaturated group from the compound that can be used as a monomer (m1) and Substituted into a hydrogen atom or a group without an ethylenically unsaturated group (such as a hydroxyl group, an amine group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkoxy group, a glycidoxy group, etc.) Compounds, etc., but are not limited by these. Non-limiting specific examples of the aromatic ring-containing compound that can be used as the additive (H _RO ) include: benzyl acrylate, m-phenoxybenzyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, Phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxy polyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, the above-mentioned monomers with a perylene structure, with two Monomers with naphthothiophene structure, monomers with dibenzothiophene structure and other aromatic ring-containing monomers; 3-phenoxybenzyl alcohol, dinaphthothiophene and their derivatives (such as bonds on the dinaphthothiophene ring Aromatic ring-containing compounds without ethylenically unsaturated groups such as compounds with one or more structures of one or more substituents selected from hydroxyl, methanol, diethanol and glycidyl) Wait. In addition, the aromatic ring-containing compound may be an oligomer comprising the aromatic ring-containing monomer as a monomer unit (preferably an oligomer with a molecular weight of about 5000 or less, more preferably about 1000 or less; for example, a 2-5 polymer low polymer around). The above-mentioned oligomers can be, for example: homopolymers of aromatic ring-containing monomers; copolymers of one or more aromatic ring-containing monomers; copolymers of one or more aromatic ring-containing monomers and other monomers things etc. As the other monomers mentioned above, one type or two or more types of monomers which do not have an aromatic ring can be used.

In some aspects, since it is easy to obtain a high refractive index-enhancing effect, an organic compound having two or more aromatic rings in one molecule (hereinafter also referred to as "compound containing plural aromatic rings") can be suitably used. as an additive (H _RO ). The compound containing a plurality of aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. In addition, the compound containing a plurality of aromatic rings may be a polymer or a non-polymer. In addition, the above-mentioned polymer may be an oligomer containing a monomer containing a plurality of aromatic rings as a monomer unit (preferably an oligomer with a molecular weight of about 5,000 or less, more preferably about 1,000 or less; for example, 2-5 polymers low polymer around). The above-mentioned oligomers can be, for example: homopolymers of monomers containing plural aromatic rings; copolymers of one or more monomers containing plural aromatic rings; one or more than two types of monomers containing plural aromatic rings Copolymers of its monomers and other monomers, etc. The above-mentioned other monomer may be an aromatic ring-containing monomer which is not a monomer containing a plurality of aromatic rings, a monomer without an aromatic ring, or a combination thereof.

Non-limiting examples of compounds containing a plurality of aromatic rings include: compounds having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, compounds having two or more non-condensed aromatic rings directly (that is, without intervening other atoms) ) compounds with chemically bonded structures, compounds with condensed aromatic ring structures, compounds with perylene structures, compounds with dinaphthothiophene structures, compounds with dibenzothiophene structures, and the like. The compound containing a plurality of aromatic rings can be used alone or in combination of two or more.

In addition to the above-mentioned monomer having a fluoride structure, or an oligomer of a homopolymer or a copolymer of the above-mentioned monomer, 9,9-bis(4-hydroxybenzene can also be mentioned as a specific example of the compound having a fluoride structure. base) fluoride (refractive index: 1.68), 9,9-bis(4-aminophenyl) fluoride (refractive index: 1.73), 9,9-bis(4-hydroxy-3-methylphenyl) fluoride ( Refractive index: 1.68), 9,9-bis[4-(2-hydroxyethoxy)phenyl] fluoride (refractive index: 1.65), etc. 9,9-bisphenyl fluoride and its derivatives.

In addition to the above-mentioned monomers having a dinaphthothiophene structure, or oligomers of homopolymers or copolymers of the monomers, specific examples of the above-mentioned compounds having a dinaphthothiophene structure may also include: dinaphthothiophene Thiophene (refractive index: 1.808); hydroxyalkyldinaphthothiophene such as 6-hydroxymethyldinaphthothiophene (refractive index: 1.766); 2,12-dihydroxydinaphthothiophene (refractive index: 1.750), etc. Dihydroxydinaphthothiophene; 2,12-dihydroxyethyloxydinaphthothiophene (refractive index: 1.677) and other dihydroxyalkyloxydinaphthothiophenes; 2,12-diglycidyl Diglycidoxydinaphthothiophene such as oxydinaphthothiophene (refractive index 1.723); 2,12-diallyloxydinaphthothiophene (abbreviation: 2,12-DAODNT, refractive index 1.729) and the like having two or more ethylenically unsaturated groups such as dinaphthothiophenes and their derivatives.

In addition to the above-mentioned monomer having a dibenzothiophene structure, or an oligomer of a homopolymer or a copolymer of the above-mentioned monomer, dibenzothiophene can also be cited as a specific example of the compound having the dibenzothiophene structure. (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), 4,6-dimethyldibenzothiophene (refractive index: 1.617), and the like.

Examples of the organic compound having a heterocyclic ring (hereinafter also referred to as a heterocyclic ring-containing organic compound) which can be an option of the additive (H _{RO ) include a thioepoxy compound, a compound having a tricyclic ring, and the like.} Examples of the thioepoxy compound include bis(2,3-epithiopropyl)disulfide and polymers thereof (refractive index 1.74) described in Japanese Patent No. 3712653. As an example of the compound having a tris' ring, a compound having at least one (eg, 3 to 40, preferably 5 to 20) tris' rings in one molecule can be mentioned. In addition, the tricyclic ring is aromatic, so the compound having the tricyclic ring is also included in the concept of the above-mentioned aromatic ring-containing compound, and the compound having a plurality of tricyclic rings is also included in the above-mentioned compound containing a plurality of aromatic rings. in the concept.

In several aspects, compounds without ethylenically unsaturated groups may suitably be employed as additives (H _RO ). Thereby, deterioration of the adhesive composition due to heat or light (deterioration of leveling properties due to progress of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. The use of an additive (H _RO ) without an ethylenically unsaturated group suppresses the ethylenic unsaturated group in an adhesive sheet having an adhesive layer containing the additive (H _{RO ) or a laminate containing the adhesive sheet, etc.} It is also preferable from the viewpoint of dimensional change or deformation (warpage, waviness, etc.) caused by the reaction, generation of optical strain, and the like.

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

The usage-amount of the additive (H _RO ) with respect to 100 parts by weight of the acrylic polymer (A) (the total amount in the case of using a plurality of compounds) is not particularly limited as long as it is more than 0 part by weight, and can be set according to the purpose. In several aspects, the usage-amount of the additive (H _RO ) with respect to 100 parts by weight of the acrylic polymer (A) can be set to, for example, 80 parts by weight or less, so that the high refractive index of the adhesive and the inhibition of sticking can be achieved in a balanced manner. From the viewpoint of degradation of properties or optical properties, it is advantageous to be 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 amount of the additive (H _RO ) used relative to 100 parts by weight of the acrylic polymer (A) may be, for example, 30 parts by weight or less, or 20 parts by weight or less, It may be 15 parts by weight or less, or 10 parts by weight or less. In addition, from the viewpoint of _{increasing the refractive index of the adhesive, the usage-amount of the additive (H RO} ) with respect to 100 parts by weight of the acrylic polymer (A) can be, for example, 1 part by weight or more, or 3 parts by weight or more. It is advantageous, it should be set to 5 parts by weight or more, 7 parts or more by weight, 10 parts by weight or more, 15 parts by weight or more, and 20 parts by weight or more.

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

As the isocyanate-based crosslinking agent, a bifunctional or more functional isocyanate compound can be used, and examples thereof include aliphatic polyisocyanates such as trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HDI), and dimer acid diisocyanate. cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane and other cycloaliphatic isocyanates; 2,4 -Aromatic isocyanates such as toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and diphenyl diisocyanate (XDI); the isocyanate compounds are converted through allophanate bonds, diurea bonds, trimeric isocyanates Bond, uretdione bond, urea bond, carbodiimide bond, uretonimine bond, urethane bond, etc. modified polyisocyanates, etc. Examples of commercially available products include trade names TAKENATE 300S, TAKENATE 500, TAKENATE 600, TAKENATE D165N, TAKENATE D178N (above, manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidur T80, Sumidur L, Desmodur N3400 (above, manufactured by Sumika Bayer Urethane Co., Ltd.) manufactured), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX (above, manufactured by Tosoh Corporation), etc. An isocyanate compound can be used individually by 1 type or in combination of 2 or more types. A bifunctional isocyanate compound and a trifunctional or more isocyanate compound may be used in combination.

Examples of epoxy-based crosslinking agents include bisphenol A, epichlorohydrin-type epoxy-based resins, ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, and glycerol diglycidyl ether. , glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N , N,N',N'-tetraglycidyl-diamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. These can be used individually by 1 type or in combination of 2 or more types.

Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate. , Neopentaerythritol di(meth)acrylate, Neopentaerythritol di(meth)acrylate, Neotaerythritol tri(meth)acrylate, Dipivalerythritol hexa(meth)acrylate, Ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate base) acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, bisphenoxyethanol, di(meth)acrylic acid Esters, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyl glycol di(meth)acrylate, hexyl glycol di(meth)acrylate Acrylate etc. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The usage-amount when using a crosslinking agent (may be a polyfunctional monomer) is not specifically limited, For example, it can be set to the range of about 0.001 weight part - 5.0 weight part with respect to 100 weight part of said monomer components. From the viewpoint of improving the flexibility of the adhesive, in several aspects, the use amount of the crosslinking agent relative to 100 parts by weight of the monomer component is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and can be 1.0 part by weight or less, 0.5 part by weight or less, or 0.2 part by weight or less. In addition, from the viewpoint of appropriately exerting the effect of use of the crosslinking agent, in several aspects, the use amount of the crosslinking agent may be, for example, 0.005 part by weight or more, or 0.01 part by weight relative to 100 parts by weight of the monomer component. The above may be 0.05 part by weight or more, or 0.08 part by weight or more.

In order to make the crosslinking reaction proceed more efficiently, a crosslinking catalyst may also be used. Examples of the crosslinking catalyst include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, iron(III) acetylacetonate, butyltin oxide, and dioctyltin dilaurate. Among them, tin-based cross-linking catalysts such as dioctyl tin dilaurate are preferred. The amount of the cross-linking catalyst used is not particularly limited. Considering 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 monomer component can be set to, for example, about 0.0001 part by weight or more and 1 part by weight or less. range, and it is preferable to set it as the range of 0.001 weight part or more and 0.5 weight part or less.

The adhesive composition may contain a compound capable of generating keto-enol tautomerism as a crosslinking retarder. Thereby, the effect of extending the service life of the adhesive composition can be achieved. For example, a compound capable of generating keto-enol tautomerism can be suitably used in an adhesive composition containing an isocyanate-based crosslinking agent. Various β-dicarbonyl compounds can be used as compounds that can produce keto-enol tautomerism. For example, β-diketones (acetone acetone, 2,4-hexanedione, etc.) or acetoacetates (methyl acetoacetate, ethyl acetoacetate, etc.) can be suitably used. The compound which can generate keto-enol tautomerism can be used individually by 1 type or in combination of 2 or more types. The usage-amount of the compound capable of generating keto-enol tautomerism can be, for example, 0.1 part by weight or more and 20 parts by weight or less, and can be 0.5 part by weight or more and 10 parts by weight with respect to 100 parts by weight of the monomer component. Hereinafter, it may be 1 part by weight or more and 5 parts by weight or less.

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

(Plasticizing Material) In several aspects of the adhesive composition disclosed herein, the adhesive composition may further comprise a plasticizing material having a lower molecular weight than that of the acrylic polymer (A) as an additive that can be used as desired . By using a plasticized material, the flexibility of the adhesive layer can be improved, thereby improving the adhesion to the adherend, the flexibility of the entire adhesive sheet, or the followability to deformation. From the viewpoint of compatibility or transparency in the adhesive layer, an organic material can be suitably used as the plasticizing material. The plasticizing material may also be a material that can be used as the above-mentioned additive (H _RO ).

The molecular weight of the plasticizing material may be lower than that of the acrylic polymer (A), and is not particularly limited. In several aspects, the molecular weight of the plasticizing material may be less than 30,000, less than 25,000, less than 10,000, preferably less than 5,000, preferably less than 3,000 (eg, less than 1,000) from the viewpoint of easily exhibiting the plasticizing effect. , can be less than 800, can be less than 600, can be less than 500, can also be less than 400. The fact that the molecular weight of the plasticizing material is not too large is advantageous from the viewpoint of enhancing the compatibility in the adhesive layer. In addition, in several aspects, from the viewpoint of easily exerting a sufficient plasticizing effect, the molecular weight of the plasticizing material is preferably 130 or more, preferably 150 or more, more preferably 170 or more, and may be 200 or more , which can be more than 250 or more than 300. In several aspects, the molecular weight of the plasticizing material may be greater than 500, greater than or equal to 1000, or greater than or equal to 2000. The fact that the molecular weight of the plasticizing material is not too low is also desirable from the viewpoint of the heat resistance of the adhesive sheet or the suppression of contamination by the adhesive.

Non-limiting examples of compounds that can be used as options for plasticizing materials include: compounds that can be used as monomers (m1) (such as (meth)acrylates with aromatic rings such as benzyl, phenoxy, naphthyl, etc., structural monomers, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure, etc.); oligomers containing compounds that can be used as monomers (m1) as monomer units; The compound used for the monomer (m1) is a compound having a structure in which a part having an ethylenically unsaturated group is removed and replaced with a hydrogen atom or a group without an ethylenically unsaturated group (for example, 3-phenoxybenzyl alcohol). From the viewpoint of improving flexibility, low Tg monomers such as n-butyl acrylate or 2-ethylhexyl Copolymerization. As the plasticizing material, well-known plasticizers (for example, phthalate-based, terephthalate-based, adipate-based, adipic acid-based polyester, ethylene benzoate, etc.) can also be used. etc.) one or more of them.

In several aspects, an organic material having a refractive index of about 1.50 or higher (preferably 1.53 or higher) may be suitably used as the plasticizing material. Specific examples of compounds that can be selected as plasticizing materials include: diethylene glycol dibenzoate (refractive index 1.55), dipropylene glycol dibenzoate (refractive index 1.54), 3-phenoxytoluene ( Refractive index 1.57), 3-ethylbiphenyl (refractive index 1.59), 3-methoxybiphenyl (refractive index 1.61), 4-methoxybiphenyl (refractive index 1.57), polyethylene glycol diphenylmethane Acid ester, 3-phenoxybenzyl alcohol (refractive index 1.59), triphenyl phosphate (refractive index 1.56), benzyl benzoate (refractive index 1.57), 4-(tertiary butyl)phenyldiphenyl Phosphate (refractive index 1.56), trimethylphenyl phosphate (refractive index 1.55), butyl benzyl phthalate (refractive index 1.54), methyl rosin (refractive index 1.53), alkyl benzyl phthalate Ester (refractive index 1.53), butyl (phenylsulfonyl)amine (refractive index 1.53), trimethyl trimellitate (refractive index 1.52), benzyl phthalate (refractive index 1.52), 2- Ethylhexyl diphenyl phosphate (refractive index 1.51), sham (2,4-di-tertiary butylphenyl) phosphite, etc., are not limited by these. From the viewpoint of refractive index and compatibility, for example, diethylene glycol dibenzoate can be suitably used. The upper limit of the refractive index of the plasticizing material is not particularly limited, and may be, for example, 3.00 or less. In some aspects, from the viewpoint of the ease of preparation of the adhesive composition or the compatibility in the adhesive, it is suitable that the refractive index of the plasticizing material is 2.50 or less, and 2.00 or less is advantageous. It may be 1.90 or less, may be 1.80 or less, or may be 1.70 or less. In addition, the refractive index of the plasticizing material was measured under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C. using an Abbe refractometer in the same manner as the refractive index of the monomer. When there is a nominal value of the refractive index at 25°C provided from the manufacturer or the like, the nominal value can be used.

In the aspect of using the plasticizing material, the usage amount of the plasticizing material with respect to 100 parts by weight of the acrylic polymer (A) is not particularly limited, and can be set according to the purpose. From the viewpoint of improving the plasticizing effect, the amount of the plasticizing material to be used relative to 100 parts by weight of the acrylic polymer (A) may be, for example, 0.1 part by weight or more, or 0.5 part by weight or more. From the viewpoint of plasticizing effect, it is preferably 1 part by weight or more, preferably 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, and 15 parts by weight. part or more, and may be 20 parts by weight or more. In addition, from the viewpoint of balancing the high refractive index of the adhesive, the transparency and the plasticizing effect of the adhesive, the amount of the plasticizer to be used with respect to 100 parts by weight of the acrylic polymer (A) is set to be about 100 parts by weight or less. Appropriately, it is preferably 80 parts by weight or less, preferably 60 parts by weight or less, 45 parts by weight or less, 35 parts by weight or less, or 25 parts by weight or less. In some aspects where more emphasis is placed on adhesive properties or optical properties, the amount of plasticizing material used relative to 100 parts by weight of the acrylic polymer (A) may be, for example, 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less.

(leveler) In the adhesive composition disclosed herein, 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 coatability of the above-mentioned adhesive composition, it may contain a leveling agent as required. agent. Non-limiting examples of the leveling agent include acrylic leveling agents, fluorine-based leveling agents, polysiloxane-based leveling agents, and the like. The leveling agent can be appropriately selected from, for example, commercially available leveling agents, and can be used by an ordinary method.

In several aspects, the above-mentioned leveling agent can suitably use the following polymers (hereinafter also referred to as "polymer (B)"), which are monomers comprising a polyorganosiloxane skeleton (hereinafter also referred to as "monomers") S1") and a polymer of a monomer raw material of an acrylic monomer (hereinafter also referred to as "monomer raw material B"). The polymer (B) can be referred to as a copolymer of the monomer S1 and an acrylic monomer. The polymer (B) may be used alone or in combination of two or more.

The monomer S1 is not particularly limited, and any monomer containing a polyorganosiloxane skeleton can be used. Monomer S1 can be suitably used for a structure having a polymerizable reactive group at one end. Among them, monomer S1 having a structure having a polymerizable reactive group at one end and a functional group that does not have a crosslinking reaction with the acrylic polymer (A) at the other end can be suitably used. Commercially available products include, for example, terminal-reactive polysiloxane oil (for example, models such as X-22-174ASX, X-22-2426, X-22-2475, and KF-2012) manufactured by Shin-Etsu Chemical Co., Ltd. Monomer S1 may be used alone or in combination of two or more.

The functional group equivalent of the monomer S1 may be, for example, about 100 g/mol to 30000 g/mol. In several ideal aspects, the functional group equivalent weight may be, for example, 500 g/mol or more, 800 g/mol or more, 1500 g/mol or more, or 2000 g/mol or more. In addition, the functional group equivalent may be, for example, 20,000 g/mol or less, less than 10,000 g/mol, 7,000 g/mol or less, or 5,500 g/mol or less. If the functional group equivalent of the monomer S1 is within the above-mentioned range, it is easy to exhibit a good leveling effect. In addition, when two or more monomers with different functional group equivalents are used as the monomer S1, the functional group equivalent of the monomer S1 can be the sum of the products of the functional group equivalents of various monomers and the weight fraction of the monomer.

Here, "functional group equivalent" means the weight of the main skeleton (eg, polydimethylsiloxane) bonded to each functional group. The relevant labeling unit g/mol is converted into 1 mol of the functional group. The functional group equivalent of the monomer S1 can be ^{calculated, for example, from the spectral intensity of 1} H-NMR (proton NMR) by nuclear magnetic resonance (NMR). Functional group equivalent of the monomer is carried out according to the S1 ¹ H-NMR spectral intensity of (g / mol) is calculated, it can be resolved according to the relevant general ¹ H-NMR spectrum of the structure analysis method, and if necessary, refer to Japanese Patent No. 5951153 i.e. The records in the Bulletin No. In the functional group equivalent of the monomer S1, the above-mentioned functional group means a polymerizable functional group (for example, an ethylenically unsaturated group such as a (meth)acryloyl group, a vinyl group, and an allyl group).

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

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

Another example of the said acryl-type monomer is the (meth)acrylate which has an alicyclic hydrocarbon group. For example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, 1-adamantyl (meth)acrylate can be used esters, etc. The (meth)acrylate which has an alicyclic hydrocarbon group may not be used.

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

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

The Mw of the polymer (B) may be, for example, 5,000 or more, preferably 10,000 or more, or 15,000 or more. Moreover, Mw of the polymer (B) may be, for example, 200,000 or less, preferably 100,000 or less, 50,000 or less, or 30,000 or less. By setting the Mw of the polymer (B) in an appropriate range, good compatibility and leveling properties can be exhibited.

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

The usage amount of the polymer (B) relative to 100 parts by weight of the acrylic polymer (A) can be, for example, 0.001 part by weight or more, and from the viewpoint of obtaining a higher use effect, it can be 0.01 part by weight or more, You may make it 0.03 weight part or more. Moreover, the usage-amount of the said polymer (B) may be, for example, 3 parts by weight or less, but from the viewpoint of reducing the influence on the refractive index, 1 part by weight or less is suitable, it may be 0.5 part by weight or less, or It may be 0.1 part by weight or less.

(Inorganic Particles) The technology disclosed herein can be suitably implemented without substantially using inorganic particles for increasing the refractive index, but as long as the application effect of the technology disclosed herein is not greatly impaired, except for additives ( In addition to H _RO ), high-refractive-index inorganic particles can be used as an auxiliary, without hindrance. Examples of the above-mentioned inorganic particles include titanium oxide (titania, TiO ₂ ), zirconia (zirconia, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide (Nb ₂ O _{5 ).} Inorganic particles composed of inorganic oxides (specifically, metal oxides) such as The average particle diameter of the above-mentioned inorganic particles (referring to the 50% volume average particle diameter obtained by the laser scattering diffraction method) can be selected from, for example, a range of about 10 nm to 100 nm. The usage-amount of the said inorganic particle should be less than 5 weight part with respect to 100 weight part of acryl-type polymer (A), Preferably it is less than 1 weight part. In the aspect of the use of additives (H _RO) of, the amount of the inorganic particles (weight basis) or less should be set to 2-fold amount of the additive (H _RO) of, and set to 1 times or less or 0.5 times or less than good.

(other additives) The adhesive composition disclosed herein may optionally contain plasticizers, softeners, colorants, antistatic agents, antiaging agents, ultraviolet absorbers, antioxidants, light A stabilizer, an antiseptic|preservative, etc. can be used for well-known additives of an adhesive composition. For the above-mentioned various additives, conventionally known ones can be used in accordance with a conventional method, and no particular feature is given to the present invention, so detailed descriptions are omitted.

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

(refractive index) The adhesives disclosed herein can be those that exhibit a refractive index above a predetermined level. According to the technology disclosed herein, it is possible to provide an adhesive having a refractive index of, for example, 1.560 or more (preferably 1.570 or more, preferably more than 1.570), an adhesive composition capable of forming the adhesive, and an adhesive comprising the above-mentioned adhesive piece.

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

In several aspects, the refractive index of the above-mentioned adhesive is preferably 1.575 or higher (eg, greater than 1.575), preferably 1.580 or higher, more preferably 1.585 or higher, and particularly preferably 1.590 or higher (eg, 1.595 or higher). By using the adhesive with the refractive index, the difference in refractive index between the adhesive and the adherend can be used to effectively control the behavior of light. In several aspects of the adhesives disclosed herein, the adhesive may have a refractive index of, for example, 1.600 or more or 1.600, 1.605 or more or more than 1.605, or 1.610 or more or more than 1.610. The ideal upper limit of the refractive index of the adhesive may vary according to the refractive index of the adherend, etc., so it is not limited to a specific range. In several aspects, the refractive index of the adhesive may be, for example, 1.700 or less, 1.670 or less, or 1.650 or less, in consideration of a balance with adhesive properties or transparency.

＜Adhesive Sheet＞ According to the present 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 of the adhesive compositions disclosed herein (eg, a hardened product of the adhesive composition). The above-mentioned adhesive sheet may be a substrate-attached adhesive sheet in the form of having an adhesive layer on one side or both sides of a non-peelable substrate (supporting substrate), or a form in which the above-mentioned adhesive layer is held on a release liner, etc. A non-substrate adhesive sheet (ie, an adhesive sheet without a non-peelable substrate, typically an adhesive sheet composed of an adhesive layer). The concept of the adhesive sheet mentioned herein may include those called adhesive tapes, adhesive labels, adhesive films, and the like. The adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, it may be an adhesive sheet further processed into various shapes.

A configuration example of the adhesive sheet disclosed here is shown in FIG. 1 . The pressure-sensitive adhesive sheet 1 is constituted as a single-sided adhesive pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet), and includes an adhesive layer 10 whose first surface 10A serves as an adhesion surface (adhesive surface) to adhere to an adherend and the supporting substrate 20, which is laminated on the second surface 10B of the adhesive layer 10. The second surface 10B of the adhesive layer 10 is bonded to the first surface (non-peelable surface) 20A of the support substrate 20 . As the support substrate 20, a plastic film such as a polyester film can be used, for example. The support substrate 20 may also be an optical film such as a polarizing plate. For example, as shown in FIG. 1 , the adhesive sheet 1 before use (before being attached to the adherend) can be in the form of a release liner-attached adhesive sheet 50 in which the adhesive surface 10A is protected by the release liner 30 , and the release liner 30 series is that at least the adhesive layer side becomes the peelable surface (peelable surface). Alternatively, the second surface 20B (the surface on the opposite side to the first surface 20A, also referred to as the back surface) of the support substrate 20 may be the peeling surface, and the second surface 20B may be brought into contact with the adhesive surface 10A. It is wound or laminated in such a way as to protect the adhesive surface 10A. The adhesive layer 10 may be a single-layer structure, or may be a laminated structure in which two or more sub-adhesive layers with different compositions are in direct contact (ie, not separated by layers composed of non-adhesive materials) laminated.

The release liner is not particularly limited, for example, a release liner with a surface of a liner substrate such as a resin film or paper that has been peeled off, or a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based release liner can be used. Release liners, etc., made of low-adhesion materials of resins (polyethylene, polypropylene, etc.). For the above-mentioned peeling treatment, for example, a peeling treatment agent such as polysiloxane-based and long-chain alkyl-based can be used. In several aspects, a release-treated resin film may suitably be used as a release liner.

The adhesive sheet disclosed herein may also be in the form of a substrateless double-sided adhesive sheet composed of an adhesive layer. As shown in FIG. 2 , the double-sided adhesive sheet 2 without substrate can be in the following form before use: the first surface (first adhesive surface) 10A and the second surface (second adhesive surface) 10B of the adhesive layer 10 are At least the side of the adhesive layer is protected by the release liners 31 and 32 of the releasable surface (release surface). Alternatively, the back surface of the release liner 31 (the surface on the opposite side to the adhesive side) may be the release surface, and the adhesive surface 10B may be wound or laminated so that the back surface of the release liner 31 abuts, Thereby, the adhesive surfaces 10A and 10B are protected. The double-sided adhesive sheet without a substrate can be used, for example, by bonding a substrate (which may be an optical member such as an optical film) on at least one of the first adhesive surface and the second adhesive surface. Like the adhesive layer 10 in the adhesive sheet 1 shown in FIG. 1, the adhesive layer constituting the double-sided adhesive sheet without the base material can be a single-layer structure, or it can also be two or more sub-adhesive layers with different compositions in direct contact with each other. Laminated structure.

The adhesive sheet disclosed herein may be a constituent element of the optical member of the adhesive sheet to which the optical member is bonded to one surface of the adhesive layer. For example, as shown in FIG. 3 , the adhesive sheet 1 shown in FIG. 1 may be a constituent element of the optical member 100 of the adhesive sheet with the optical member 70 bonded to one surface 10A of the adhesive layer 10 . The above-mentioned optical member may be, for example, a glass plate, a resin film, a metal plate, or the like. Furthermore, in the adhesive sheet 1 shown in FIG. 1 , when the support substrate 20 is an optical member such as an optical film, the adhesive sheet 1 can be regarded as an adhesive sheet in which the optical member is bonded to the second surface 10B of the adhesive layer 10 of optical components.

In addition, although there is no special illustration, the adhesive sheet disclosed here can also be in the form of the following double-sided adhesive sheet with substrate (double-sided adhesive sheet with substrate): The support base material on the first surface and the second surface, wherein the first adhesive layer is fixed and laminated on the first surface, and the second adhesive layer is fixed and laminated on the second surface. As an example of the configuration of the double-sided adhesive sheet with the substrate, in the single-sided adhesive sheet 1 shown in FIG. 1 , the second surface 20B of the support substrate 20 is a non-peelable surface and the second surface A second adhesive layer is provided on the two surfaces 20B, the second surface of the second adhesive layer is bonded to the second surface 20B of the support substrate 20, and the first surface (and the second surface of the second adhesive layer) The surface on the opposite side) becomes the second adhesive surface of the double-sided adhesive sheet with the base material. The composition of the adhesive constituting the second adhesive layer may be the same as or different from the composition of the adhesive constituting the first adhesive layer. The double-sided adhesive sheet with the base material before use may be in a form in which the first adhesive surface and the second adhesive surface are protected by a release liner, similarly to the above-described double-sided adhesive sheet without a base material.

The adhesive sheet disclosed here is a double-sided adhesive sheet with both sides being the adhesive side (including both a double-sided adhesive sheet without a substrate and a double-sided adhesive sheet with a substrate; unless otherwise specified, the same applies hereinafter) In this form, the refractive index of the first adhesive surface and the second adhesive surface is not particularly limited. In several aspects, at least the first adhesive surface preferably satisfies any one of the above-mentioned refractive indices, and may be a double-sided adhesive sheet in which both the first and second adhesive surfaces satisfy any of the above-mentioned refractive indices. In several aspects, the refractive index n _{2 of} the second adhesive surface may be approximately the same as the refractive index n _{1 of the first adhesive surface.} More specifically, the absolute value of the difference between the refractive indices of the two adhesive surfaces, ie |n ₁ -n ₂ |, may be, for example, less than 0.05, or less than 0.03, or less than 0.01. The lower limit of |n ₁ -n ₂ | may be 0.00 or more than 0.00. The relative relationship between the refractive indices of the two adhesive surfaces may be n ₁ >n ₂ , n ₁ <n ₂ , or n ₁ =n ₂ . In several other aspects, the adhesive surface of the first adhesive sheet of refractive index n ₁ n ₂ the refractive index difference between the second surface of the adhesive, i.e., n ₁ -n _2, may be greater than 0.00 e.g., 0.01 or more can be , may be 0.03 or more, 0.05 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more. The magnitude relationship between n ₁ and n ₂ can also be reversed. A double-sided adhesive sheet having different refractive indices on the first adhesive surface and the second adhesive surface can be realized, for example, by the following method: in the double-sided adhesive sheet with a substrate, the refractive index is laminated on a non-peelable support substrate Different first and second adhesive layers; or, the adhesive layer constituting the double-sided adhesive sheet without the base material is made into a laminated structure of two or more sub-adhesive layers with different refractive indices.

The adhesive layer of the adhesive sheet disclosed herein can be formed by hardening the adhesive composition after imparting (eg, coating) the adhesive composition to a suitable surface. The adhesive composition can be applied by, for example, a gravure roll coater, a reverse roll coater, a touch roll coater, a dip roll coater, a bar coater, a blade coater, a spray coater, and the like. cloth machine to implement.

The adhesive layer of the adhesive sheet disclosed herein may be an adhesive layer with post-curing properties or an adhesive layer without post-curing properties. Here, the adhesive layer having post-curability refers to an adhesive layer that can be further hardened by irradiation of heat or active energy rays (eg, ultraviolet rays). Examples of the adhesive layer having post-curing properties include an adhesive layer having an unreacted ethylenically unsaturated group in the side chain of a base polymer (eg, acrylic polymer (A)), or an adhesive layer containing an unreacted polyamide. Adhesive layer of functional monomers. In several aspects, the adhesive layer preferably does not have post-hardening properties. The adhesive layer without post-curing properties does not undergo dimensional changes accompanying the post-curing reaction (that is, good dimensional stability), so it is easy to suppress the warpage of the adhesive sheet or the adherend to which the adhesive sheet is attached. It is also advantageous from the viewpoint of suppressing the optical strain of the adhesive layer that dimensional changes caused by post-hardening (eg, hardening shrinkage) do not occur.

The thickness of the adhesive layer is not particularly limited, but can be set to, for example, 3 µm or more. In several aspects, the thickness of the adhesive layer may be, for example, 5 µm or more, 10 µm or more, 20 µm or more, 30 µm or more, 50 µm or more, 70 µm or more, or 85 µm or more. Furthermore, in several aspects, the thickness of the adhesive layer may be, for example, 300 µm or less, 250 µm or less, 200 µm or less, 150 µm or less, or 120 µm or less. The fact that the thickness of the adhesive layer is not too large is advantageous from the viewpoint of thinning of the adhesive sheet. For example, the technique disclosed here is suitable to be implemented in a state where the thickness of the adhesive layer is in the range of 3 µm to 200 µm (preferably 5 µm to 100 µm). In addition, in the case of an adhesive sheet having a first adhesive layer and a second adhesive layer on the first and second surfaces of the substrate, the thickness of the above-mentioned adhesive layer can be applied to 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, in the double-sided adhesive sheet without a substrate composed of an adhesive layer, the thickness of the adhesive layer is the thickness of the adhesive sheet.

(total light transmittance) In the technique disclosed herein, the total light transmittance of the adhesive layer is suitable, for example, greater than 50%, and preferably 70% or more. In several ideal forms, the total light transmittance of the adherend is above 85%, preferably above 86%, preferably above 88%, preferably above 90% (for example, above 90.0%), or More than 90.5%. The adhesive sheet with the above-mentioned high-transparency adhesive layer can have the structure of the base material or the structure without the base material. For good visibility of the properties of the adherend. In several aspects, the total light transmittance of the adhesive layer may be 93% or higher, or 95% or higher. The upper limit of the total light transmittance is theoretically a value obtained by excluding the light loss (Fresnel loss) caused by reflection at the air interface by 100%. About 96% or less, and also about 95% or less. In several aspects, the total light transmittance of the adhesive layer may be about 94% or less, may be about 93% or less, or may be about 92% or less, considering refractive index or adhesive properties. The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. For the transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Laboratory or its equivalent can be used. More specifically, for example, the total light transmittance of the adhesive layer can be measured according to the following examples. The total light transmittance of the adhesive layer can be adjusted by, for example, selecting the composition or thickness of the adhesive layer.

When the adhesive sheet disclosed here is in the form of a substrate-attached double-sided adhesive sheet in which the first adhesive layer and the second adhesive layer are fixed and laminated on the support substrate, at least the first adhesive layer preferably satisfies any one of the above Total light transmittance. In the use state in which light penetrates in the thickness direction of the adhesive sheet, both the first adhesive layer and the second adhesive layer preferably satisfy any one of the above-mentioned total light transmittances. The relative relationship between the total light transmittances of the two adhesive layers can be the first adhesive layer > the second adhesive layer, the first adhesive layer < the second adhesive layer, or the first adhesive layer = the first adhesive layer. 2 Adhesive layers.

(Haze value) In several aspects, the haze value of the adhesive layer constituting the adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less (eg, 2.0% or less), preferably 1.0% or less, and more preferably 0.9% or less. The adhesive sheet with the above-mentioned high-transparency adhesive layer can have the structure of the base material or the structure without the base material. For good visibility of the properties of the adherend. In several aspects, the haze value of the adhesive layer may be 0.8% or less, 0.5% or less, or 0.3% or less. The lower limit of the haze value of the adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the better. On the other hand, in several aspects, the haze value may be, for example, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or more in consideration of refractive index or adhesive properties. above 0.4%. These haze values for the adhesive layer can also be suitably applied to the application of the adhesive sheet when the technique disclosed herein is implemented in the form of an adhesive sheet without a substrate (typically, an adhesive sheet composed of an adhesive layer). haze value.

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

When the adhesive sheet disclosed here is in the form of a substrate-attached double-sided adhesive sheet in which the first adhesive layer and the second adhesive layer are fixed and laminated on the support substrate, as long as at least the first adhesive layer satisfies any one of the above The haze value may be sufficient, and the haze value of the second adhesive layer is not particularly limited. In the use state in which light penetrates in the thickness direction of the adhesive sheet, the haze value of the second adhesive layer should preferably satisfy any one of the haze values of the first adhesive layer. The relative relationship between the haze values of the two adhesive layers can be the first adhesive layer > the second adhesive layer, the first adhesive layer < the second adhesive layer, or the first adhesive layer = the second adhesive layer.

(Surface smoothness of adhesive surface) In the several aspects of the adhesive sheet disclosed herein, the adhesive surface of the adhesive sheet preferably has a high surface smoothness.

For example, the arithmetic mean thickness Ra of the above-mentioned adhesive surfaces is preferably limited to a predetermined value or less. From the viewpoint of optical homogeneity, it is preferable to have an adhesive surface designed to have a low arithmetic mean roughness Ra. By limiting the arithmetic mean roughness Ra, for example, in the use state where light is captured through the above-mentioned adhesive surface (the adhesive sheet arranged on the viewpoint side of the light-emitting device in a light-emitting device, etc.), it is possible to exert a restraint due to sticking. The effect of uneven brightness occurs due to the surface state of the agent layer. The fact that the arithmetic mean roughness Ra of the adhesive surface is low also helps to suppress optical strain, and the suppression of optical strain also helps to improve optical homogeneity. When the adhesive sheet disclosed here is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, at least the arithmetic mean thickness Ra of the first adhesive surface should be limited to a predetermined value or less, preferably two adhesive surfaces. The arithmetic mean roughness Ra of the planes is limited to a predetermined value or less. Since each adhesive surface of the double-sided adhesive sheet has high surface smoothness, it is possible to suitably realize the bonding with excellent optical homogeneity.

In several aspects, the arithmetic mean roughness Ra of the adhesive surface is preferably about 70 nm or less, preferably about 65 nm or less, more preferably about 55 nm or less, may be less than 50 nm, may be less than 45 nm, and may be less than 40 nm. From the viewpoint of production efficiency, etc., in several aspects, the arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet may be, for example, about 10 nm or more, about 20 nm or more, or about 30 nm or more (for example, about 40 nm or more). ). When the adhesive sheet has a first adhesive surface and a second adhesive surface, the arithmetic mean thickness Ra of the first adhesive surface and the arithmetic mean thickness Ra of the second adhesive surface may be the same or different.

Also, for example, the maximum height Rz of the above-mentioned adhesive surface is preferably limited to a predetermined value or less. From the viewpoint of optical homogeneity, it is preferable to have a structure with an adhesive surface designed to have a lower maximum height Rz. By limiting the maximum height Rz, the effect of suppressing uneven brightness due to the surface state of the adhesive layer can be exhibited, for example, in the use aspect in which light is captured through the adhesive surface as described above. The fact that the maximum height Rz of the adhesive surface is low is also beneficial for suppressing optical strain. When the adhesive sheet disclosed here is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that at least the maximum height Rz of the first adhesive surface be limited to a predetermined value or less, preferably the height of the two adhesive surfaces The maximum heights Rz are all limited below a predetermined value. Since each adhesive surface of the double-sided adhesive sheet has high surface smoothness, it is possible to suitably realize the bonding with excellent optical homogeneity.

In several aspects, the maximum height Rz of the adhesive surface is preferably about 600 nm or less, preferably about 500 nm or less, more preferably about 450 nm or less, especially about 400 nm or less, may be less than 350 nm, may be less than 300 nm, or less than 250nm. From the viewpoint of production efficiency and the like, in several aspects, the maximum height Rz of the adhesive surface of the adhesive sheet may be, for example, about 10 nm or more, about 50 nm or more, about 100 nm or more, or about 200 nm or more. In an aspect in which the adhesive sheet has a first adhesive surface and a second adhesive surface, the maximum height Rz of the first adhesive surface and the maximum height Rz of the second adhesive surface may be the same or different.

The arithmetic mean roughness Ra and the maximum height Rz of the adhesive surface were measured using a non-contact surface roughness measuring device. As the non-contact surface roughness measuring device, an optical interference method surface roughness measuring device can be used, for example, a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO Corporation) or its equivalent can be used. Specifically, the arithmetic mean roughness Ra and the maximum height Rz can be measured by, for example, the following measurement method or by setting the measurement operation or measurement conditions so as to obtain the same or corresponding results as in the case of using the measurement method. That is, using a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO Corporation), the surface shape of the measurement sample was measured under the following conditions in an environment of 23°C and 50% RH. From the measured data, the arithmetic surface roughness Ra was calculated in accordance with JIS B 0601-2001. The maximum height Rz is based on the data obtained by the above measurement (roughness curve), and the height Rp from the average line of the thickness curve to the highest top on the upper side and the depth Rv from the average line to the deepest valley on the lower side are obtained. and. Five determinations of Ra and Rz were performed (ie, N=5), and the average of these was used. The measurement sample can be prepared by cutting, for example, an adhesive layer to be measured or an adhesive sheet including the adhesive layer into a size of about 150 mm in length and 50 mm in width. When the adhesive surface has been protected by the release liner, peel off the release liner smoothly (for example, under the conditions of a stretching speed of 300 mm/min and a peeling angle of 180°) to expose the adhesive surface. After exposing the adhesive surface, it is advisable to stand for about 30 minutes before measuring. [Measurement conditions] Measurement area: 5.62mm×4.22mm (objective lens: 2.5 times, inner lens: 0.5 times) Parsing mode: Remove: Cylinder Data Fill: ON (Max: 25) Remove Spikes: ON (xRMS: 1) Filter: OFF

The arithmetic mean roughness Ra and the maximum height Rz of the adhesive surface can be determined by the composition or properties (viscosity, leveling, etc.) of the adhesive composition used to form the adhesive layer, the surface of the release liner protecting the adhesive surface (peeling surface) properties, etc. to adjust.

(stored elastic modulus G') In the adhesive sheet disclosed herein, the storage elastic modulus G' (hereinafter also referred to as "storage elastic modulus G' (25)") of the adhesive constituting the adhesive layer at 25°C can be adjusted according to the purpose of use or the state of use and other appropriate settings, not limited to a specific range. The storage elastic modulus G'(25) of the adhesive may be, for example, about 700 kPa or less. In several aspects, from the viewpoint of the ease of attachment to the adherend, etc., the storage elastic modulus G'(25) of the adhesive is preferably about 600 kPa or less, preferably 500 kPa or less, more preferably 400kPa or less (for example, 350kPa or less). In several aspects, from the viewpoint of improving the flexibility of the adhesive at room temperature (eg, 25°C) and making it easy to adhere to the adherend, the storage elastic modulus G'(25) of the adhesive is About 330 kPa or less is advantageous, and preferably 300 kPa or less. In aspects where adherence or softness in the room temperature region is more important, the storage elastic modulus G'(25) of the adhesive may be, for example, less than 270 kPa or less than 250 kPa, with less than 200 kPa being advantageous, and It is preferably less than 180kPa, more preferably less than 160kPa (for example, less than 140kPa). In several aspects, the storage elastic modulus G'(25) of the adhesive may be less than 100 kPa or less than 90 kPa. The lower limit of the storage elastic modulus G'(25) of the adhesive is not particularly limited, but from the viewpoint of processability and handling properties, it may be, for example, 30 kPa or more, 50 kPa or more, or 70 kPa or more. In several aspects, considering the high refractive index, the storage elastic modulus G'(25) may be 100 kPa or more, 150 kPa or more, 200 kPa or more, 250 kPa or more, or 300 kPa or more.

In the adhesive sheet disclosed herein, the storage elastic modulus G' (hereinafter also referred to as "storage elastic modulus G'(50)") of the adhesive constituting the adhesive layer at 50°C is not particularly limited, for example, it may be less than 100 kPa . In several aspects, the storage elastic modulus G'(50) is suitably less than 60 kPa, preferably less than 40 kPa, more preferably less than 38 kPa (eg, less than 36 kPa). Such as the adhesive with limited storage elastic modulus G'(50), the adhesiveness to the adherend can be easily improved by performing moderate heating as required, thereby improving the adhesiveness to the adherend . The lower limit of the storage elastic modulus G'(50) of the adhesive is not particularly limited. In some aspects, from the viewpoint of the heat resistance properties of the adhesive, the storage elastic modulus G'(50) may be, for example, 10 kPa or more, 15 kPa or more, 20 kPa or more, or 23 kPa or more.

In the several aspects of the adhesive disclosed herein, the adhesive preferably satisfies at least one of the following conditions: (a) the storage elastic modulus G'(25) at 25°C is below 350kPa (preferably below 200kPa, for example below 180kPa); and (b) The storage elastic modulus G'(50) at 50°C is less than 60kPa (preferably less than 50kPa, more preferably less than 40kPa, eg less than 38kPa). An adhesive that satisfies at least the above-mentioned condition (a) is ideal from the viewpoint of the adhesiveness to the adherend in a room temperature region (eg, 25° C.). The adhesive that satisfies at least the above-mentioned condition (b) is preferable because the adhesiveness (adhesion) to the adherend can be easily improved by heating to a temperature slightly higher than room temperature. Adhesives that do not satisfy the above condition (a) and satisfy the above (b) can be used as heat-activated adhesives, which have good reworkability (re-adhesion) at the initial stage of attachment at room temperature. A temperature slightly higher than room temperature can effectively improve the peel strength of the adherend. The above-mentioned thermal activation can also be performed by heating the adhesive to a temperature slightly higher than room temperature when it is attached to an adherend. The above-mentioned temperature slightly higher than room temperature is, for example, about 60°C or less, and preferably about 55°C or less (for example, about 50°C or less).

In several aspects of the adhesive sheet disclosed herein, the ratio of the storage elastic modulus G'(50) [kPa] of the adhesive constituting the adhesive layer to the storage elastic modulus G'(25) [kPa], That is, the storage elastic modulus ratio G'(50)/G'(25) may be, for example, 70% or less, 40% or less, 30% or less, or 20% or less. Adhesives with small G'(50)/G'(25) are suitable for use as the above heat-activated adhesives. The lower limit of G'(50)/G'(25) is not particularly limited. G'(50)/G'(25) is, for example, 5% or more. From the viewpoint of the heat resistance of the adhesive, it is preferably 10% or more, and may be 12% or more, or 15% or more.

The storage elastic moduli G'(25) and G'(50) can be obtained by dynamic viscoelasticity measurement, and G'(50)/G'(25) can be calculated from the results. The dynamic viscoelasticity measurement can be performed by a conventional method using a commercially available dynamic viscoelasticity measuring apparatus, for example, "Advanced Rheometric Expansion System (ARES)" manufactured by TA Instruments, or its equivalent, under the following measurement conditions. As the measurement sample, the adhesive layer of the evaluation object was adjusted to a thickness of about 1.5 mm by laminating or the like according to requirements. [Measurement conditions] Deformation Mode: Twist Measurement frequency: 1Hz Heating rate: 5°C/min Shape: parallel plate 7.9mmφ

The storage elastic modulus G'(25), G'(50) and storage elastic modulus ratio of the adhesive layer can be determined by selecting the composition of the monomer components constituting the acrylic polymer (A) (for example, selecting the monomer ( m1) type and content), whether to use cross-linking agent, select the type and use amount, whether to use the above-mentioned additives (H _RO ) or plasticizing materials, and select the type and use amount to adjust. For example, as the monomer (m1), in addition to the first monomer which is the main component of the monomer (m1), a smaller amount of the second monomer having a different chemical structure from the first monomer may be used and When the first monomer is used in combination, G'(50)/G'(25) can be reduced in addition to the reduction of G'(50) when the first monomer is used alone as the monomer (m1).

The adhesive sheet disclosed here is a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface (for example, a double-sided adhesive sheet with a first adhesive layer and a second adhesive layer attached to a substrate, constituting a first adhesive layer) A double-sided adhesive sheet without a substrate in which the sub-adhesive layer on the adhesive surface and the sub-adhesive layer constituting the second adhesive surface are laminated without a non-adhesive substrate interposed therebetween; the same applies to other similar descriptions) In the form of storage elastic modulus G'(25), G'(50) and storage elastic modulus ratio are at least applied to the adhesive layer constituting the first adhesive surface, and should be applied to the adhesive constituting the first adhesive surface layer and both the adhesive layer constituting the second adhesive surface. The storage elastic modulus G' of the adhesive layer constituting the first adhesive surface and the storage elastic modulus G' of the adhesive layer constituting the second adhesive surface may be the same or different.

In several aspects of the technology disclosed herein, the peak temperature of the tan δ of the adhesive constituting the adhesive layer is preferably about -50°C or higher, and preferably about 50°C or lower. Here, the tanδ (loss tangent) of the adhesive means the ratio of the loss elastic modulus G" to the storage elastic modulus G' of the adhesive. That is, tanδ=G"/G'. The tanδ of the adhesive can be used to sandwich a disc-shaped adhesive sample with a thickness of about 2mm and a diameter of 7.9mm with parallel plates, while applying a shear strain with a frequency of 1Hz using a viscoelasticity test device, while measuring the temperature range -60 ℃ Under the conditions of ~60°C and heating rate of 5°C/min, the temperature dispersion test of the adhesive was carried out in shear mode, and the storage elastic modulus G'(Pa) and loss elastic modulus G"(Pa) It is obtained by the following formula: tanδ=G"/G'. The peak temperature of tanδ of the adhesive can be obtained from the transition of tanδ in the above-mentioned temperature range (it may be referred to as Tpeak hereinafter). As the viscoelasticity test device, ARES or its equivalent manufactured by TA Instruments can be used.

In several aspects, it is advantageous for the Tpeak of the adhesive to be 45°C or lower or 35°C or lower, and preferably 30°C or lower (eg, 25°C or lower), may be 20°C or lower, or 15°C or lower. With an adhesive with a lower Tpeak, there is a tendency to easily obtain good initial adhesion or adhesion in the room temperature region. On the other hand, the fact that the Tpeak of the adhesive is not too low is ideal from the viewpoint of imparting moderate cohesiveness to the adhesive, and it tends to be suitable for both high refractive index. From this viewpoint, in several aspects, the Tpeak of the adhesive may be, for example, -40°C or higher, -30°C or higher, -20°C or higher, -5°C or higher, or 5°C or higher. ℃ or higher, may be 15°C or higher, more preferably 25°C or higher. When the adhesive with higher Tpeak is attached to the adherend, it can be used in a state where one or both of the adhesive and the adherend are heated to a temperature slightly higher than room temperature as required. . The Tpeak of the adhesive can be determined by selecting the composition of the adhesive (for example, the composition of the monomer components constituting the acrylic polymer (A), the presence or absence of additives ( _HRO ) or plasticizing materials, and the selection of types and amounts), etc. adjust. When the adhesive sheet disclosed here is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, the Tpeak of the above-mentioned adhesive is preferably applied to at least the adhesive layer constituting the first adhesive surface, and is applied to the adhesive layer constituting the first adhesive surface. Both the adhesive layer on the first adhesive surface and the adhesive layer constituting the second adhesive surface are preferable. The Tpeak of the adhesive layer constituting the first adhesive surface and the Tpeak of the adhesive layer constituting the second adhesive surface may be the same or different.

(water absorption rate) In the several aspects of the adhesive sheet disclosed herein, the water absorption of the adhesive layer constituting the adhesive sheet is preferably limited below a predetermined value. By limiting the water absorption rate of the adhesive layer, there is a tendency to suppress the dimensional change of the adhesive layer due to fluctuations in the moisture content in the adhesive layer (eg, absorption and release of moisture such as moisture in the environment). Thereby, the adhesive sheet or the adherend to which the adhesive sheet is attached can be suppressed due to the inconsistency of the dimensional change between the adhesive layer and the adjoining layer (which may be a support substrate, a release liner, an adherend, etc.). warping. It is also preferable from the viewpoint that the flatness, transparency, refractive index, etc. of the adhesive layer can be fixed and maintained because the fluctuation of the water content in the adhesive layer can be suppressed. Moreover, since the adhesive layer with a low water absorption rate does not easily absorb water, it is suitable as an adhesive sheet for a member or a product containing an element that does not like water, such as an organic EL element, for example.

In several aspects, the water absorption of the adhesive layer is suitably about 1.0% or less, preferably 0.7% or less, more preferably 0.5% or less (eg, less than 0.5%), may be 0.4% or less, may be 0.3% or less % or less, may be 0.2% or less, or 0.1% or less. The lower limit of the water absorption rate of the adhesive layer is not particularly limited, but from practical viewpoints such as compatibility with adhesive properties, it may be, for example, 0.01% or more, 0.05% or more, 0.1% or more, or 0.15% or more. . When the adhesive sheet disclosed here is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that the water absorption rate of at least the adhesive layer constituting the first adhesive surface is limited to a predetermined value or less. From the viewpoint of obtaining a higher effect, it is preferable to limit the water absorption rate of the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface to a predetermined value or less.

In addition, the water absorption rate (also called moisture content) of an adhesive bond layer was measured by the following method. [Measurement of Moisture Content] The adhesive layer of the evaluation object was cut into a size of 4 cm×5 cm (area: 20 cm ² ) together with two release liners arranged on one side and the other side, and the peeling on one side was removed. After liner, fit to pre-weighed aluminum foil. Next, the release liner on the other side of the adhesive layer was removed, put into a constant temperature and humidity tank with a temperature of 60° C. and a relative humidity of 90%, and taken out after 72 hours. After weighing the test piece laminated with the adhesive layer and the aluminum foil, a moisture meter (Mitsubishi Chemical Analytech CA-200 type) equipped with a heating vaporization device (Mitsubishi Chemical Analytech VA-200 type) was used. The coulometric titration method measures the moisture content under the following conditions. Anolyte: AQUAMICRON AKX (manufactured by Mitsubishi Chemical) Catholyte: AQUAMICRON CXU (manufactured by Mitsubishi Chemical) Heating vaporization temperature: 150°C

(gel fraction) The gel fraction of the adhesive layer can be appropriately set according to the purpose of use or the state of use, and is not limited to a specific range. The said gel fraction is suitably about 99% or less, for example, about 97% or less. From the viewpoint of easiness to properly balance high refractive index and adhesive properties, in several ideal aspects, the gel fraction is about 95% or less, preferably about 92% or less (eg, about 90% or less). The reason that the gel fraction is not too high can be properly followed by the concavities and convexities existing on the surface of the adherend (for example, the concavo-convex structure provided in the light-emitting device to improve the light extraction efficiency, etc.), and it is also good from the viewpoint of good adhesion. In several aspects, the gel fraction may be about 88% or less, about 75% or less, or about 65% or less. In addition, from the viewpoint of imparting appropriate cohesiveness to the adhesive and appropriately exhibiting the adhesive properties, the gel fraction of the adhesive layer is, for example, about 10% or more, preferably about 20% or more, and may be about 10% or more. more than 30%. From the viewpoint of the deformation resistance of the adhesive layer (prevention of overflow due to pressure or air bubbles due to entrapment of foreign objects, etc.), the above-mentioned gel fraction is preferably about 30% or more, more preferably about 40% or more, It can be about 45% or more, it can be about 50% or more, it can be about 65% or more, and it can be about 75% or more. The gel fraction of the adhesive sheet (typically, an adhesive sheet without a substrate) is also preferably set to the range exemplified above. The gel fraction can be adjusted by the molecular weight or molecular structure, concentration, degree of crosslinking, etc. of the acrylic polymer (A). The gel fraction was measured by the following method.

[Determination of Gel Fraction] A predetermined amount of adhesive sample (weight Wg _{1 ) was wrapped into a small bag with a porous polytetrafluoroethylene membrane (weight Wg 2} ) with an average pore diameter of 0.2 µm, and a kite string (weight Wg ₃ ) Tie the opening. The above-mentioned porous polytetrafluoroethylene (PTFE) film used the trade name "Nitoflon (registered trademark) NTF1122" available from Nitto Denko Corporation (average pore diameter 0.2 µm, porosity 75%, thickness 85 µm) or its equivalent. The package was immersed in a sufficient amount of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days, and only the sol in the adhesive was eluted out of the film, and then the package was taken out and adhered by wiping. The bale was dried at 130°C for 2 hours with ethyl acetate on the outer surface, and the weight (Wg ₄ ) of the bale was determined. The gel fraction of the adhesive layer can be obtained by substituting each value into the following formula. Gel fraction (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

When the adhesive sheet disclosed here is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, the above gel fraction should be applied at least to the adhesive layer constituting the first adhesive surface, and preferably applied to the adhesive layer constituting the first adhesive surface. 1. Both the adhesive layer on the adhesive surface and the adhesive layer constituting the second adhesive surface. The gel fraction of the adhesive layer constituting the first adhesive surface and the gel fraction of the adhesive layer constituting the second adhesive surface may be the same or different.

(peel strength) In several aspects of the adhesive sheet disclosed herein, it is appropriate that the peel strength of the adhesive sheet to the glass plate is about 1.0N/25mm or more (for example, 1.5N/25mm or more), preferably 2N/25mm or more, more preferably 3N/25mm or more, 4N/25mm or more, 6N/25mm or more, 8N/25mm or more, 10N/25mm or more, and 12N/25mm or more. 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.

Here, the above-mentioned peeling strength is obtained by the following method: press-bonding on an alkali glass plate as an adherend, leaving it for 30 minutes in an environment of 23° C. and 50% RH, and then putting it into a pressurized defoaming apparatus ( Autoclave) at a temperature of 50°C and a pressure of 0.5MPa for 30 minutes, and then placed in a gas environment of 23°C and 50% RH for 24 hours. 180° peeling was carried out under the condition of minutes, and the adhesion was measured. During the measurement, a suitable backing material (such as a polyethylene terephthalate (PET) film with a thickness of about 25µm to about 50µm) can be attached to the adhesive sheet of the object to be measured for reinforcement. More specifically, the peel strength can be measured according to the method described in the examples described later. When the adhesive sheet disclosed here is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, in several aspects, the above-mentioned peel strength is preferably applied to at least the first adhesive surface, and is preferably applied to Both the first adhesive surface and the second adhesive surface. The peeling strength of the first adhesion facing the glass plate and the peeling strength of the second adhesion facing the glass may be the same or different.

(Support Substrate) The adhesive sheets of several aspects may be in the form of a substrate-attached adhesive sheet provided with an adhesive layer on one side or both sides of the support substrate. The material of the support substrate is not particularly limited, and can be appropriately selected according to the purpose of use of the adhesive sheet and the state of use. Non-limiting examples of substrates that can be used include polyolefin films mainly composed of polyolefins such as polypropylene (PP) or ethylene-propylene copolymer, polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyolefin films, etc. Polyester film mainly composed of polyester such as butylene terephthalate (PBT) and polyethylene naphthalate (PEN), and plastic film such as polyvinyl chloride film mainly composed of polyvinyl chloride; Foamed sheet composed of polyurethane foam, polyethylene (PE) foam, polychloroprene foam and other foams; various fibrous substances (can be natural fibers such as hemp, cotton, etc.) , polyester, vinylon and other synthetic fibers, acetate and other semi-synthetic fibers, etc.) woven and non-woven fabrics alone or blended; Japanese paper, Dowling paper, kraft paper, crepe paper and other papers; aluminum foil, copper foil etc. Metal foil etc. It can also be a base material composed of these composite materials. Examples of the composite base material include, for example, a base material with 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.

In several aspects, various film substrates can be suitably used. The above-mentioned film substrate can be a porous substrate such as a foamed film or a non-woven sheet, a non-porous substrate, or a structure in which a porous layer and a non-porous layer are laminated. substrate. In several aspects, as the above-mentioned film base material, a resin film containing an independent and shape-maintainable (self-supporting or non-dependent) resin film can be suitably used as a base film. Here, the "resin film" refers to a non-porous structure and is typically a resin film substantially free of bubbles (voids). Therefore, the above-mentioned resin film is a concept that can be distinguished from a foamed film or a nonwoven fabric. As the above-mentioned resin film, one that is independent and can maintain its shape (self-supporting or non-dependent) can be suitably used. The above-mentioned resin film may have a single-layer structure, or may have a multilayer structure of two or more layers (for example, a three-layer structure).

The material constituting the resin film may be, for example, polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN) as main components Polyester resins, polyolefin resins mainly composed of polyolefins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer, and cellulose such as triacetate Resins, acetate-based resins, polyamide-based resins, polyether-based resins, polycarbonate-based resins, nylon 6, nylon 66, polyamide (PA)-based resins such as partially aromatic polyamides, polyamides Cyclic polyolefin resins such as amine (PI) resins, transparent polyimide resins, polyimide imide (PAI), polyether ether ketone (PEEK), polyether ether (PES), and norbornene-based resins , (meth)acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl alcohol resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl alcohol copolymer Resin, polyarylate-based resin, polyphenylene sulfide (PPS)-based resin, polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE) or fluorinated poly Fluorine resins such as imide, etc.

The said resin film may be formed using the resin material which contains 1 type of the said resin independently, and may be formed using the resin material which mixed 2 or more types. The above-mentioned resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched). For example, PET film, PBT film, PEN film, non-stretch polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene ( LLDPE) film, PP/PE blend film, etc. From the viewpoint of strength or dimensional stability, examples of desirable resin films include PET films, PEN films, PPS films, and PEEK films. From the viewpoint of ease of acquisition, etc., PET films and PPS films are particularly suitable, and among them, PET films are more preferable.

In the resin film, light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slipping agents, Anti-blocking agent and other well-known additives. The blending amount of the additive is not particularly limited, and can be appropriately set according to the application of the adhesive sheet and the like.

The manufacturing method of a resin film is not specifically limited. For example, conventionally known general resin film forming methods, such as extrusion forming, air forming, T-die casting forming, and calender roll forming, can be suitably used.

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

In some aspects, a light-transmitting substrate (hereinafter also referred to as a light-transmitting substrate) can be suitably used as the support substrate. Thereby, the adhesive sheet with the light-transmitting base material can be formed. The total light transmittance of the light-transmitting substrate may be greater than 50%, for example, or may be greater than or equal to 70%. In several ideal aspects, the total light transmittance of the support substrate is above 80%, preferably above 90%, and may be above 95% (eg, 95-100%). The above-mentioned total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. For the transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Laboratory or its equivalent can be used. As a suitable example of the said light-transmitting base material, the resin film which has light-transmitting property is mentioned. The said light-transmitting base material may be an optical film.

The thickness of the base material is not particularly limited, and can be selected according to the purpose of use of the adhesive sheet or the state of use. The thickness of the base material may be, for example, 500 µm or less, and from the viewpoint of the rationality or workability of the adhesive sheet, it is preferably 300 µm or less, and may be 150 µm or less, 100 µm or less, 50 µm or less, or 25 µm or less. , can also be 10µm or less. When the thickness of the base material becomes smaller, the followability to the surface shape of the adherend tends to improve. In addition, from the viewpoints of handleability and workability, the thickness of the base material may be, for example, 2 µm or more, 10 µm or more, or 25 µm or more.

The side of the substrate 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 formation of a primer by coating a primer (primer). Conventionally known surface treatment such as coating. The surface treatment may be a treatment for improving the anchorage of the adhesive layer to the substrate. The composition of the primer for forming the primer layer is not particularly limited, and can be appropriately selected from known materials. The thickness of the primer layer is not particularly limited, and is usually about 0.01µm~1µm, and preferably about 0.1µm~1µm. Other treatments that can be performed on the substrate according to requirements include antistatic layer formation treatment, colored layer formation treatment, printing treatment, and the like. These treatments can be applied individually or in combination.

When the adhesive sheet disclosed herein is in the form of an adhesive sheet with a base material, the thickness of the adhesive sheet may be, for example, 1000µm or less, 350µm or less, 200µm or less, 120µm or less, 75µm or less, or 50µm or less. In addition, from the viewpoint of handling properties, the thickness of the adhesive sheet may be, for example, 10 µm or more, 25 µm or more, 80 µm or more, or 130 µm or more. In addition, the thickness of an adhesive sheet means the thickness of the part attached to the adherend. For example, in the adhesive sheet 1 having the structure shown in FIG. 1 , the thickness from the first surface (adhesive surface) 10A of the adhesive layer to the second surface 20B of the support base material does not include the thickness of the release liner 30 .

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

The release liner is not particularly limited, for example, it can be used for a release liner with a release layer on the surface of a liner substrate such as a resin film or paper (it can be a paper laminated with a resin such as polyethylene), or a release liner made of fluorine Release liners, etc., are made of resin films made of low-adhesion materials such as polymers (polytetrafluoroethylene, etc.) or polyolefin resins (polyethylene, polypropylene, etc.). From the viewpoint of excellent surface smoothness, it can be suitably used for a release liner having a release layer on the surface of a resin film serving 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, and examples thereof include polyethylene (PE) films, polypropylene (PP) films, polybutene films, polybutadiene films, and polymethylpentene films. , PVC film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-ethyl acetate copolymer film, etc. For the formation of the above-mentioned peeling layer, for example, a polysiloxane-based peeling agent, a long-chain alkyl-based peeling agent, an olefin-based peeling agent, a fluorine-based peeling agent, an aliphatic amide-based peeling agent, molybdenum sulfide, and carbon dioxide can be used. Silicon powder and other well-known peeling treatment agents.

<Application> The adhesive sheet disclosed here can be used by being attached to various adherends. The constituent material of the above-mentioned adherend (the adherend material) is not particularly limited, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, etc. or including two or more metal materials such as alloys, or, for example, polyimide-based resins, acrylic resins, polyether nitrile-based resins, polyether-based resins, polyester-based resins (PET-based resins, polyethylene naphthalate resins) Diester-based resins, etc.), polyvinyl chloride-based resins, polyphenylene sulfide-based resins, polyetheretherketone-based resins, polyamide-based resins (so-called aramid resins, etc.), polyarylate-based resins, fluorine resins, polycarbonate resins, cellulose polymers such as cellulose diacetate or cellulose triacetate, vinyl butyral polymers, liquid crystal polymers, and carbon materials such as graphene (typically Plastic materials), aluminum oxide, zirconium oxide, titanium oxide, SiO ₂ , ITO (indium tin oxide), ATO (antimony doped tin oxide) and other metal oxides and their mixtures, aluminum nitride, silicon nitride, nitride Titanium, gallium nitride, indium nitride and other nitrides and their composites, alkali glass, alkali-free glass, quartz glass, borosilicate glass, sapphire glass and other inorganic materials. The adhesive sheet disclosed herein can be used by being at least surface-attached to a member (eg, an optical member) composed of the above-mentioned materials.

The adhesive sheet disclosed here can be used in the following attachment state: after being attached to the adherend, it does not need to be heated to a temperature higher than room temperature (for example, 20°C to 35°C). The attached state. In addition, under the conditions permitted by the constituent material of the adhesive sheet (such as the material of the base material) or the type of the adherend, it is also possible to perform at least any Heat treatment is performed at one point in time. The heat treatment can be performed for the purpose of improving the adhesion of the adhesive to the adherend or promoting adhesion. The heat treatment temperature can be appropriately set to obtain the desired effect in consideration of the surface state of the adherend, etc., within the allowable range according to the constituent material of the adhesive sheet or the type of the adherend. Below, it may be 80°C or lower, 60°C or lower, or 50°C or lower.

The member or material to which the adhesive sheet is attached (at least one adherend in the double-sided adhesive sheet) may be light-transmitting. For the adherend, the technology disclosed herein can be applied to easily obtain the advantage of suppressing the decrease in optical properties (transparency, etc.) and simultaneously increasing the refractive index. The total light transmittance of the adherend may be greater than 50%, for example, or may be greater than 70%. In several ideal forms, the total light transmittance of the adherend is above 80%, preferably above 90%, more preferably above 95% (eg, 95-100%). The adhesive sheet disclosed here is suitable for use in a state of being attached to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The above-mentioned total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. For the transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Laboratory or its equivalent can be used.

The refractive index of the adhesive layer and the refractive index of the adherend may be the same or different. For example, by making the refractive index of the adhesive layer relatively high relative to the refractive index of the adherend, the light incident on the adhesive layer at an angle below the critical angle from the adherend side can be refracted on the front side, increasing the frontal brightness. At this time, the refractive index of the adherend may be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, or less than 1.45, and, for example, may be 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. Moreover, by the adherend having a relatively high refractive index with respect to the adhesive layer, the light incident on the adherend from the adhesive layer side can be refracted on the front side, and the front brightness can be improved. At this time, the refractive index of the adherend may be, for example, 1.60 or more, 1.65 or more, or 1.70 or more, for example, 3.00 or less, 2.50 or less, or 2.00 or less. On the other hand, by narrowing the difference in refractive index between the adhesive layer and the adherend, light reflection at the interface can be suppressed. At this time, the refractive index of the adherend may be about 1.55 to 1.80, about 1.55 to 1.75, or about 1.60 to 1.70. The refractive index of the adherend can be measured in the same way as the refractive index of the adhesive.

In several ideal aspects, the adherend may have any of the above-mentioned refractive indices and any of the above-mentioned total light transmittances. In the form of being attached to the adherend, the effects of the technology disclosed herein can be suitably exerted.

An example of a preferable application is an optical application. More specifically, for example, the adhesive sheet disclosed herein can be suitably used for optical applications such as applications that can be used to bond optical members (for optical member bonding), or applications for manufacturing products (optical products) using the above-mentioned optical members. adhesive sheet to use.

The above-mentioned optical member refers to a member having optical properties (such as polarization, light refraction, light scattering, light reflectivity, light transmittance, light absorption, light diffraction, optical rotation, visual discrimination, etc.). The above-mentioned optical member is not particularly limited as long as it is a member having optical properties, and examples thereof include members constituting devices (optical devices) such as display devices (image display devices) and input devices, or members used in such devices, and examples include polarized light plate, wave plate, retardation plate, optical compensation film, brightness enhancement film, light guide plate, reflective film, anti-reflection film, hard coating (HC) film, shock 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 set to include forms such as plate, film, sheet, etc., for example, "polarizing film" is set to include "polarizing plate" or "polarizer", and "polarizing film" The "light guide plate" is set to include a "light guide film", a "light guide sheet", or the like. In addition, the above-mentioned "polarizing plate" is assumed to include a circular polarizing plate.

Examples of the display device include liquid crystal display devices, organic EL (electroluminescence) display devices, micro LEDs (µLEDs), mini LEDs (miniLEDs), PDPs (plasma display panels), electronic paper, and the like. Moreover, a touch panel etc. are mentioned as the said input device.

The said optical member is not specifically limited, For example, the member (for example, sheet-like, film-like, plate-like member) which consists of glass, acrylic resin, polycarbonate, polyethylene terephthalate, a metal thin film, etc. is mentioned. In addition, the "optical member" in this specification is also set to include a member (design film, decorative film, surface protection film, etc.) that performs a decorative or protective function while maintaining the visibility of a display device or an input device.

For example, the technology disclosed herein can be suitably used for bonding optical films such as films having functions such as light transmission, reflection, diffusion, waveguide, condensing, diffraction, etc., or fluorescent films, to other optical members (which may be other optical films). Among them, in the bonding of optical films having at least one of the functions of waveguide, condensing, and diffracting light, the entire bonding layer should preferably have a high refractive index, which can be an ideal application object of the technology disclosed herein.

The adhesives disclosed herein can be suitably used for bonding optical films such as light guide films, diffusion films, fluorescent films, toning films, wafers, lenticular films, and microlens array films, for example. In these applications, reduction in thickness and improvement in light extraction efficiency are required from the viewpoint of the tendency of miniaturization of optical members or the improvement of performance. The adhesives disclosed herein can be suitably utilized as adhesives that can meet the requirements. In more detail, for example, in the case of bonding a light guide film or a diffusion film, it is possible to contribute to thinning by adjusting the refractive index (eg, increasing the refractive index) of the adhesive layer serving as the bonding layer. The bonding of the fluorescent films can improve the light extraction efficiency (also regarded as the luminous efficiency) by appropriately adjusting the refractive index difference between the fluorescent light-emitting body and the adhesive. In the bonding of the toner film, by appropriately adjusting the refractive index of the adhesive so that the difference in refractive index with the toner pigment becomes smaller, scattering components can be reduced, thereby contributing to the improvement of light transmittance. During the bonding of the wafer, the lenticular film, the microlens array film, etc., the diffraction of light can be controlled by appropriately adjusting the refractive index of the adhesive, which can help to improve the brightness and/or viewing angle.

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

In addition, since the adhesive sheet disclosed here is suitable for increasing the refractive index, it can be suitably used in the form of being attached to a light-emitting layer such as an optical semiconductor (for example, a high-refractive light-emitting layer mainly composed of an inorganic material). . By reducing the refractive index difference between the light-emitting layer and the adhesive layer, the reflection at these interfaces can be suppressed, and the light extraction efficiency can be improved. The adhesive sheet that can be used in this state preferably has an adhesive layer with a high refractive index. In addition, from the viewpoint of preventing deterioration of the self-luminous element due to moisture in advance, the water absorption rate of the adhesive layer is preferably low. From the viewpoint of improving brightness, the adhesive sheet is preferably low in coloration. It is also advantageous from the viewpoint of suppressing unintentional coloring caused by the adhesive sheet.

The adhesive disclosed herein can be suitably used as a cover lens surface in microlenses and other lens members (for example, lens members such as microlenses constituting microlens array films or microlenses for cameras) used as constituent members of cameras and light-emitting devices. The coating layer, the bonding layer of the member facing the lens surface (for example, a member having a surface shape corresponding to the lens surface), the filling layer filled between the lens surface and the member, etc. are used. Since the adhesive disclosed here is suitable for increasing the refractive index, even if it is a lens with a high refractive index (for example, a lens made of a high refractive index resin, or a lens having a surface layer made of a high refractive index resin), it can still be used. Reduce the refractive index difference with the lens. This is advantageous from the viewpoint of thinning of the above-mentioned lens and a product provided with the lens, and also contributes to suppressing aberrations and increasing the Abbe number. The adhesive disclosed here can also be used itself as a lens resin in the form of filling in the concave portion or the void of a suitable transparent member, for example.

The aspect of bonding optical members using the adhesive sheet disclosed herein is not particularly limited, and for example, the following aspects can be used: (1) an aspect in which optical members are bonded to each other through the adhesive sheet disclosed here; or (2) A form in which the optical member is attached to a member other than the optical member through the adhesive sheet disclosed herein; (3) the form in which the adhesive sheet disclosed herein includes an optical member and the adhesive sheet is attached to the optical member or The state of components other than optical components. Moreover, in the aspect of said (3), the adhesive sheet of the form containing an optical member can be, for example, the adhesive sheet whose support body is an optical member (for example, an optical film). The adhesive sheet in the form including the optical member as a support as described above can also be regarded as an adhesive optical member (eg, an adhesive optical film). Also, when the adhesive sheet disclosed here is an adhesive sheet of a type with 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 the above-mentioned functional film on at least one side of the functional film. The "adhesive functional film" of the adhesive layer is disclosed.

From the above, according to the technology disclosed herein, a laminate including the adhesive sheet disclosed herein and a member to which the adhesive sheet is attached can be provided. The member to which the adhesive sheet can be attached may have the refractive index of the above-mentioned adherend material. In addition, the difference (refractive index difference) between the refractive index of the adhesive sheet and the refractive index of the member may be the difference in refractive index between the above-mentioned adherend and the adhesive sheet. The members constituting the laminate are described above with reference to the members, materials, and adherends, and therefore, the description will not be repeated.

As can be understood from the above description and the following examples, the matters disclosed by this specification include the following matters. [1] An adhesive sheet comprising an adhesive layer; and It has an adhesive surface formed by the above-mentioned adhesive layer; The refractive index of the above-mentioned adhesive layer is greater than 1.570, the total light transmittance is more than 86%, and the haze value is less than 3.0%. [2] The adhesive sheet according to the above [1], wherein the thickness of the above-mentioned adhesive layer is 5 µm or more. [3] The adhesive sheet according to the above [1] or [2], which has a peel strength (adhesive force) to a glass plate of 3 N/25 mm or more. [4] The adhesive sheet according to any one of the above [1] to [3], wherein the arithmetic mean roughness Ra of the adhesive surface is 100 nm or less. [5] The adhesive sheet according to any one of the above [1] to [4], wherein the water absorption rate of the adhesive layer is 1.0% or less. [6] The adhesive sheet according to any one of the above [1] to [5], which is constituted in the form of a laminate including the above-mentioned adhesive layer and a light-transmitting base material. [7] The adhesive sheet according to the above [6], wherein the light-transmitting base material is a resin film. [8] The adhesive sheet according to any one of the above [1] to [5], which is a double-sided adhesive sheet composed of the above-mentioned adhesive layer. [9] An adhesive sheet with a release liner, comprising: The adhesive sheet according to any one of the above [1] to [8]; and A release liner arranged on the adhesive surface of the above-mentioned adhesive sheet. [10] An adhesive composition for forming an adhesive layer of the adhesive sheet according to any one of the above [1] to [8].

[11] An adhesive composition, comprising: an acrylic polymer (A) comprising an aromatic ring-containing monomer (m1) as a monomer unit; and an additive (H _RO ), the refractive index of which is higher than the above-mentioned acrylic polymer (A) higher organic material. [12] The adhesive composition of the above-mentioned [11], wherein _{the refractive index of the above-mentioned additive (H RO} ) is 1.60 or more. [13] The adhesive composition according to the above [11] or [12], wherein the content of the above-mentioned additive (H _RO ) relative to 100 parts by weight of the above-mentioned acrylic polymer (A) is greater than 0 parts by weight and not more than 60 parts by weight . [14] The adhesive composition according to any one of the above [11] to [13], wherein the additive (H _RO ) comprises at least one selected from the group consisting of an aromatic-ring-containing compound and a heterocyclic-containing compound 1 compound. [15] The adhesive composition according to any one of the above [11] to [14], wherein the additive (H _RO ) includes a compound having two or more aromatic rings in one molecule. [16] The adhesive composition according to the above [15], wherein the additive (H _RO ) contains a compound satisfying at least one of the following as the compound having two or more aromatic rings in one molecule: (i) Two or more aromatic rings are contained: A structure in which non-condensed aromatic rings are directly chemically bonded; and (ii) a structure in which two aromatic rings have been condensed. [17] The adhesive composition according to any one of the above [11] to [16], wherein in the monomer components constituting the above-mentioned acrylic polymer (A), the content of the above-mentioned aromatic ring-containing monomer (m1) is 50% by weight or more. [18] The adhesive composition according to any one of the above [11] to [17], wherein in the monomer components constituting the above-mentioned acrylic polymer (A), the content of the above-mentioned aromatic ring-containing monomer (m1) is greater than 70% by weight and less than 100% by weight, and 50% by weight or more of the above-mentioned aromatic ring-containing monomers (m1) are monomers whose glass transition temperature of the homopolymer is 10°C or lower. [19] The adhesive composition according to any one of the above [11] to [18], wherein the monomer component constituting the above-mentioned acrylic polymer (A) further contains a monomer (m2), and the monomer (m2) Has at least one of a hydroxyl group and a carboxyl group. [20] The adhesive composition according to any one of the above [11] to [18], which is used to form an adhesive layer of the adhesive sheet according to any one of the above [1] to [8]. [21] An adhesive comprising the adhesive composition according to any one of the above [11] to [20], and having a refractive index higher than 1.570. [22] An adhesive sheet comprising an adhesive layer composed of an adhesive, wherein the adhesive is formed from the adhesive composition according to any one of the above [11] to [20]. [23] The pressure-sensitive adhesive sheet according to the above-mentioned [22], wherein the haze value of the pressure-sensitive adhesive layer is 1.0% or less.

[24] An interlayer sheet that is used between layers of a laminate for optical purposes; and which comprises a _{viscoelastic layer V 1 having a refractive index n 1} of 1.570 or more, and satisfies: total light transmittance of 86% or more ; The haze value is below 1.0%; and the storage elastic modulus G' at 25°C is 30kPa~700kPa. [25] The thickness of the interlayer sheet in the above [24] is 5 µm or more. [26] The interlayer sheet according to the above [24] or [25], wherein the viscoelastic layer V ₁ comprises a main polymer and a plasticizing material with a lower molecular weight than the main polymer. [27] The interlayer sheet according to the above [26], wherein the weight average molecular weight of the plasticizing material is 30,000 or less. [28] The interlayer sheet according to any one of the above [24] to [27], further comprising a viscoelastic layer V _{2 laminated on the viscoelastic layer V 1} , and the viscoelastic layer V _{2 is} heated at 25° C. storage elastic modulus G _'V2 viscoelastic layer is less than the V ₁ stored at 25 deg.] C of the elastic modulus G' _V1. [29] As the inter [28] of the plies, wherein the refractive index of the viscoelastic layer of V ₂ n ₂ is less than the refractive index of the viscoelastic layer V ₁ n _1. [30] The interlayer sheet according to any one of the above [24] to [29], wherein the viscoelastic layer V ₁ is a layer formed of the adhesive composition according to any one of the above [11] to [18] . [31] The interlayer sheet according to any one of the above [24] to [29], wherein the viscoelastic layer V ₁ is the adhesive layer in the adhesive sheet according to any one of the above [1] to [5]. [32] An optical laminate comprising: the interlayer sheet according to any one of the above [24] to [31], and a resin film laminated on the interlayer sheet. [33] An interlayer sheet with a release liner, comprising: the interlayer sheet according to any one of the above [24] to [31], and a release liner covering at least one surface of the interlayer sheet.

Example Various embodiments related to the present invention will be described below, but the specific examples 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 introduction pipe, and a cooler, phenoxybenzyl acrylate (co-prosperity) was introduced as a monomer component. Manufactured by Shaka Chemical Co., Ltd., trade name "LIGHT ACRYLATE POB-A", refractive index: 1.566, Tg of homopolymer: -35°C; hereinafter referred to as "POB-A") 95 parts and 4-hydroxybutyl acrylate ( 4HBA) 5 parts, 0.2 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 100 parts of toluene as a polymerization solvent, nitrogen gas was introduced while stirring slowly, and the liquid in the flask was The temperature was maintained at around 60°C, and the polymerization reaction was performed for 6 hours to prepare a solution (50%) of the acrylic polymer A1. The polymerization average molecular weight (Mw) of the acrylic polymer A1 was 500,000. In the above-mentioned acrylic polymer A1, Tg according to the composition of the monomer components (ie, Tg _T ) is -35°C, and Tg according to the composition of the aromatic ring-containing monomer (ie, Tg _m1 ) is -35°C.

(Preparation of adhesive composition) The solution (50%) of the above-mentioned acrylic polymer A1 was diluted with ethyl acetate to 30%, and 334 parts of the solution (100 parts of non-volatile components) was added as an additive ( _HRO ) 5 parts of 6-acrylooxymethyl dinaphthothiophene (Dinaphthothiophene-6-methacrylate body manufactured by SUGAI Chemical Industry Co., Ltd., trade name "6MDNTA", refractive index 1.75), as a cross 10 parts of 1% ethyl acetate solution (0.1 part of non-volatile content) of hexamethylene diisocyanate trimeric isocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX", trifunctional isocyanate compound) as a linking agent 2 parts of acetone acetone as a linking retarder, 1 part of a 1% ethyl acetate solution of iron (III) acetoacetate as a cross-linking catalyst (0.01 part of non-volatile content) and stirred and mixed to prepare an acrylic adhesive composition Substance C1.

(production of adhesive sheet) The acrylic adhesive composition C1 prepared above was coated on the polysiloxane-treated surface of the polyethylene terephthalate (PET) film R1 (thickness 50µm) treated with polysiloxane on one side. Heating at 130°C for 2 minutes forms an adhesive layer with a thickness of 25µm. Next, the polysiloxane-treated side of the PET film R2 (thickness 25µm) that has been treated with polysiloxane on one side is attached to the surface of the above-mentioned adhesive layer. In the above-described manner, a base-free double-sided adhesive sheet S1 composed of the above-described adhesive layer is obtained. Both sides of the adhesive sheet S1 are protected by PET films (release liners) R1 and R2.

<Examples 2 to 5> Except for changing the type of additives ((H _RO ) and the usage amount (phr; per hundred resin) relative to 100 parts of acrylic polymer as shown in Table 1, the same as those in Example 1. Preparation of Acrylic Adhesive Composition C1 In the same manner, acrylic adhesive compositions C2 to C5 of Examples 2 to 5 were prepared. Here, "BPFL" in Table 1 represents 9,9-bis(4-hydroxyl) Phenyl) fluoride (manufactured by Osaka Gas Chemicals Co., Ltd., refractive index 1.68), "BAFL" means 9,9-bis(4-aminophenyl) fluoride (manufactured by Osaka Gas Chemicals Co., Ltd., refractive index The adhesive sheets of Examples 2 to 5 were produced in the same manner as the production of the adhesive sheets in Example 1, except that the acrylic adhesive compositions C2 to C5 were used to replace the acrylic adhesive composition C1, respectively. (A double-sided adhesive sheet without a substrate composed of an adhesive layer) S2~S5.

<Example 6> Into a separable flask equipped with a thermometer, a stirrer, a reflux cooling tube, and a nitrogen gas introduction tube, 20 parts of POB-A, 1-naphthalene methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "" LIGHT ACRYLATE NMT-A", refractive index: 1.595, Tg of homopolymer: 31°C; hereinafter referred to as "NMT-A") 80 parts, 0.2 part of AIBN as a polymerization initiator, α- as a chain transfer agent After 3.5 parts of thioglycerol and 67 parts of methyl ethyl ketone, nitrogen gas was introduced, and nitrogen substitution was performed for about 1 hour while stirring. Then, the flask was heated to 70° C. and reacted for 12 hours to obtain an acrylic oligomer (hereinafter referred to as oligomer B) having a weight average molecular weight (Mw) of 4000 and a refractive index of 1.63. . The type of the additive (H _RO ) was changed to the above-mentioned oligomer B, and its usage amount was 30 parts (30 phr) relative to 100 parts of the acrylic polymer, except that it was adhered to the acrylic in Example 1. In the same manner as the preparation of the agent composition C1, the acrylic adhesive composition C6 of this example was prepared. The adhesive sheet of this example (consisting of an adhesive layer without a base material) was produced in the same manner as the production of the adhesive sheet in Example 1, except that the acrylic adhesive composition C6 was used instead of the acrylic adhesive composition C1. The double-sided adhesive sheet) S6.

<Example 7> An acrylic adhesive composition C7 was prepared in the same manner as the preparation of the acrylic adhesive composition C1 in Example 1, except that the additive (H _{RO ) was not used.} This example was produced in the same manner as the production of the adhesive sheet in Example 1, except that the acrylic adhesive composition C7 was used instead of the acrylic adhesive composition C1, and the thickness of the adhesive layer was set to 20 µm The adhesive sheet (a double-sided adhesive sheet without a base material composed of an adhesive layer) S7.

<Example 8> The preparation of the acrylic polymer solution in Example 1 was the same as the preparation of the acrylic polymer solution in Example 1, except that the composition of the monomer components was changed to 72 parts of POB-A, 23 parts of NMT-A, and 5 parts of 4HBA In the same manner, a solution of the acrylic polymer A2 was prepared. The polymerization average molecular weight (Mw) of the acrylic polymer A2 was 450,000. An acrylic adhesive composition C8 of this example was prepared in the same manner as the preparation of the adhesive composition in Example 1, except that the solution of the acrylic polymer A2 was used instead of the solution of the acrylic polymer A1. In the same manner as the production of the adhesive sheet in Example 1, except that the acrylic adhesive composition C8 was used instead of the acrylic adhesive composition C1, the adhesive sheet of this example (consisting of an adhesive layer without a base material) was produced. The double-sided adhesive sheet) S8.

<Examples 9 to 13> Example 9 was prepared in the same manner as in the preparation of the acrylic adhesive composition C8 in Example 8, _{except that the type and amount of the additive ((H RO ) were changed as shown in Table 1.} The acrylic adhesive compositions C9 to C13 of Example 13. Except that the acrylic adhesive compositions C9 to C13 were respectively used to replace the acrylic adhesive composition C1, in the same manner as the production of the adhesive sheet in Example A1, The adhesive sheets of Examples 9 to 13 (a double-sided adhesive sheet without a base material composed of an adhesive layer) S9 to S13 were produced.

<Example 14> The acrylic adhesive composition C14 of Example 14 was prepared in the same manner as the preparation of the acrylic adhesive composition C8 in Example 8, except that the additive (( _{HRO) was not used.} In the same way as the production of the adhesive sheet in Example 8, except that the adhesive composition C14 was replaced by the acrylic adhesive composition C8, the adhesive sheet of this example (a double-sided adhesive sheet without a substrate composed of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 8. sheet) S14.

<Example 15> The same procedure as the preparation of the acrylic polymer solution in Example 1 was carried out, except that the composition of the monomer components was changed to 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of 4HBA , to prepare a solution (40%) of acrylic polymer A3. The solution (40%) of the above-mentioned acrylic polymer A3 was diluted with ethyl acetate to 20%, and 10 parts of zirconia particle dispersion liquid based on solid content was added to 500 parts of the solution (100 parts of non-volatile content). , 10 parts of 1% ethyl acetate solution (0.1 part of non-volatile content) of hexamethylene diisocyanate trimeric isocyanate (Tosoh Corporation, trade name "Coronate HX", trifunctional isocyanate compound) as a crosslinking agent , 2 parts of acetone acetone as a cross-linking retarder, 1 part of a 1% ethyl acetate solution (0.01 part of non-volatile content) of iron (III) acetoacetate as a cross-linking catalyst, and stirred and mixed to prepare an acrylic Adhesive composition C15. The above-mentioned zirconia particle dispersion system used surface-treated zirconia particles (average particle diameter: 20 nm, solid content refractive index: 1.64, surface treatment: carboxylic acid-based/phosphoric acid-based hydrophobic treatment, manufactured by Kyeisha Chemical Co., Ltd. ) surface-treated zirconia particle dispersion in propylene glycol monomethyl ether (PGME). Example 15 was produced in the same manner as the production of the adhesive sheet in Example 1, except that the acrylic adhesive composition C15 was used instead of the acrylic adhesive composition C1, and the thickness of the adhesive layer was set to 20 µm. The adhesive sheet (a double-sided adhesive sheet without a substrate composed of an adhesive layer) S15.

<Example 16> Acrylic acid was prepared in the same manner as in the preparation of the acrylic polymer solution in Example 1, except that the composition of the monomer components was changed to POB-A/n-butyl acrylate (BA)/4HBA=79/20/1 It is a solution of polymer A4. The polymerization average molecular weight (Mw) of the acrylic polymer A4 was 520,000. The acrylic adhesive composition C16 of this example was prepared in the same manner as in Example 2, except that the solution of the acrylic polymer A4 was used instead of the solution of the acrylic polymer A1, and an adhesive sheet (consisting of an adhesive layer) was produced. The double-sided adhesive sheet without substrate) S16.

<Example 17> Except that the composition of the monomer components was changed to POB-A/ethylcarbitol acrylate (CBA)/4HBA=79/20/1, in the same manner as the preparation of the acrylic polymer solution in Example 1, A solution of acrylic polymer A5 was prepared. The polymerization average molecular weight (Mw) of the acrylic polymer A5 was 460,000. The acrylic adhesive composition C17 of this example was prepared in the same manner as in Example 2 except that the solution of the acrylic polymer A4 was used instead of the solution of the acrylic polymer A1, and an adhesive sheet (consisting of an adhesive layer) was produced. The double-sided adhesive sheet without substrate) S17.

<Example 18> Prepared in the same manner as the preparation of the acrylic polymer solution in Example 1, except that the composition of the monomer components was changed to POB-A/phenoxydiethylene glycol acrylate/4HBA=79/20/1 A solution of acrylic polymer A6 was dispensed. As the phenoxydiethylene glycol acrylate, the trade name "LIGHT ACRYLATE P2H-A" manufactured by Kyōeisha Chemical Co., Ltd. was used. The polymerization average molecular weight (Mw) of the acrylic polymer A6 was 480,000. The acrylic adhesive composition C18 of this example was prepared in the same manner as in Example 2, except that the solution of the acrylic polymer A6 was used instead of the solution of the acrylic polymer A1, and an adhesive sheet (consisting of an adhesive layer) was produced. The double-sided adhesive sheet without substrate) S18.

<Example 19> Except having changed the additive (H _RO ) to 2,12-diallyloxydinaphthothiophene (manufactured by Sugai Chemical Industry Co., Ltd., abbreviation: 2,12-DAODNT, refractive index: 1.729), The acrylic pressure-sensitive adhesive composition C19 of this example was prepared in the same manner as in Example 2, and the pressure-sensitive adhesive sheet (the double-sided pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer without a base material) S19 was produced.

<Examples 20 to 22> Acrylic adhesive compositions C20 to 22 were prepared in the same manner as in Examples 16 to 18, respectively, _{except that no additive (H RO ) was used, to produce adhesive sheets (non-adhesive sheets composed of an adhesive layer).} Double-sided adhesive sheet for substrate) S20~22.

<Measurement and Evaluation> (refractive index) For the adhesive layer (double-sided adhesive sheet without substrate) of each example, an Abbe refractometer (manufactured by ATAGO CO., LTD., type "DR-M4") was used at a measurement wavelength of 589 nm and a measurement temperature of 25°C. Refractive index was measured. The results are listed in Tables 1 and 2.

(Total light transmittance and haze value) Using a test piece in which the adhesive layer of each example was attached to an alkali-free glass (thickness 0.8~1.0mm, total light transmittance 92%, haze 0.4%), a haze meter (manufactured by Murakami Color Technology Laboratory) was used. , trade name "HAZEMETER HM-150", measure the total light transmittance and haze of the above-mentioned test piece under the measurement environment of 23 ℃. The total light transmittance and haze of the above-mentioned alkali-free glass will be subtracted from the measured value. The values are taken as the total light transmittance and haze value of the adhesive layer. The results are listed in Tables 1 and 2.

(stored elastic modulus G') The adhesive laminated layer of each example was made into a thickness of about 1.5 mm, and it was set as a measurement sample. Using ARES manufactured by TA Instruments, dynamic viscoelasticity was measured under the following conditions. The storage elastic modulus G' at 25°C was read from the measurement results. The results are listed in Tables 1 and 2. [Measurement conditions] Deformation Mode: Twist Measurement frequency: 1Hz Heating rate: 5°C/min Shape: parallel plate 7.9mmφ

(peel strength) The peel strength to the glass plate was measured for the adhesive sheet of each example. That is, under the measurement environment of 23°C and 50%RH, peel off the release liner from one side of the adhesive sheet, and attach a PET film with a thickness of 50µm as a backing, and then cut it into a size of 25mm in width and 100mm in length for testing. piece. The release liner on the other side was peeled off from the test piece, and a 2 kg roller was pressed to the surface of an alkali glass plate (manufactured by Matsunami Glass Industrial Co., Ltd., thickness 1.35 mm, cyan plate frosted product) as a to-be-adhered body by one reciprocation. It was placed in this environment for 30 minutes, then put into a pressurized defoaming device (autoclave), and subjected to autoclave treatment for 30 minutes at a temperature of 50°C and a pressure of 0.5MPa, and then at 23°C and 50% RH. After being placed in a gas environment for 24 hours, use a universal tensile and compression tester to measure the peel strength (adhesion) [N/25mm] under the conditions of a tensile speed of 300mm/min and a peel angle of 180 degrees in accordance with JIS Z 0237:2000. . The universal tensile and compressive testing machine used "Tensile Compression Testing Machine, TG-1kN" manufactured by Minebea Corporation. The results are listed in Tables 1 and 2.

[Table 1]

[Table 2]

EXAMPLE adhesive as shown in Table 1, not containing the additive (H _RO) of Example 7 was added an additive (H _RO) of the adhesive 1 to 6, compared to the Example 7 shows a higher refractive index. These adhesives have high transparency and good peel strength. The same tendency is also seen in the comparison between Example 14 and Examples 8 to 13. On the other hand, compared with Examples 1 to 14, Example 15 in which the refractive index was increased by mixing inorganic particles with high refractive index was obviously poor in transparency (especially, the haze was significantly higher), and did not appear to be suitable for use as an adhesive The practical adhesion properties (peel strength).

Similarly, in Examples 16 to 19 shown in Table 2, it was confirmed that the effect of raising the refractive index was _{exhibited by using the additive (H RO ).} The adhesives of Examples 16 to 19 have high transparency and good peel strength. From the above, it can be seen that the adhesives of Examples 1 to 6, Examples 8 to 13, and Examples 16 to 19 have suppressed the decrease in optical properties and have a high refractive index, so they are suitable for optical components (such as waveguides having at least one type of light, poly Uses such as bonding of optical films with functions of light and diffraction.

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

1,2: Adhesive sheet 10: Adhesive layer 10A: 1st surface (adhesive surface) 10B: 2nd surface 20: Support substrate 20A: Side 1 (non-peelable surface) 20B: Side 2 (Back) 30, 31, 32: Release liner 50: Adhesive sheet with release liner 70: Optical components 100: Component with adhesive sheet

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 configuration of an adhesive sheet according to another embodiment. 3 is a cross-sectional view schematically showing an optical member in which the adhesive sheet according to an embodiment is attached to the optical member.

1: adhesive sheet

10: Adhesive layer

10A: 1st surface (adhesive surface)

10B: 2nd surface

20: Support substrate

20A: Side 1 (non-peelable surface)

20B: Side 2 (Back)

30: Release liner

50: Adhesive sheet with release liner

Claims (12)

An adhesive composition, comprising: an acrylic polymer (A) comprising an aromatic ring-containing monomer (m1) as a monomer unit; and an additive (H _RO ), the refractive index of which is higher than that of the aforementioned acrylic polymer (A) ) higher organic materials. The adhesive composition of claim 1, wherein _{the refractive index of the additive (H RO} ) is 1.60 or more. The adhesive composition of claim 1 or 2, wherein the content of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer (A) is greater than 0 parts by weight and less than 60 parts by weight. The adhesive composition according to any one of claims 1 to 3, wherein the additive (H _RO ) comprises at least one compound selected from the group consisting of an aromatic ring-containing compound and a heterocyclic ring-containing compound. The adhesive composition according to any one of claims 1 to 4, wherein the additive (H _RO ) comprises a compound having two or more aromatic rings in one molecule. The adhesive composition according to claim 5, wherein the additive (H _RO ) comprises a compound satisfying at least one of the following as the compound having two or more aromatic rings in one molecule: (i) Contains two non-condensed aromatic rings structure of direct chemical bond; and (ii) structure comprising 2 aromatic rings which have been condensed. The adhesive composition according to any one of claims 1 to 6, wherein in the monomer component constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is 50% by weight or more. The adhesive composition according to any one of claims 1 to 7, wherein in the monomer component constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is greater than 70% by weight and less than 100% % by weight, and 50% by weight or more of the above-mentioned aromatic ring-containing monomer (m1) is a monomer whose glass transition temperature of the homopolymer is 10°C or lower. The adhesive composition according to any one of claims 1 to 8, wherein the monomer component constituting the aforementioned acrylic polymer (A) further comprises a monomer (m2), and the monomer (m2) has one of a hydroxyl group and a carboxyl group. at least one. An adhesive is formed from the adhesive composition according to any one of claims 1 to 9, and has a refractive index higher than 1.570. An adhesive sheet, comprising an adhesive layer composed of an adhesive, and the adhesive is formed from the adhesive composition according to any one of Claims 1 to 9. The adhesive sheet according to claim 11, wherein the haze value of the adhesive layer is 1.0% or less.

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