KR20220153085A - Pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet - Google Patents

Abstract

An adhesive composition containing an acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit and an additive (H _RO ) that is an organic material having a higher refractive index than the acrylic polymer (A) is provided. In addition, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition is provided.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet

The present invention relates to an adhesive composition, an adhesive and an adhesive sheet.

This application relates to Japanese Patent Application No. 2020-052408 filed on March 24, 2020, Japanese Patent Application No. 2020-166426 filed on September 30, 2020, and filed on March 23, 2021. Priority based on Japanese Patent Application No. 2021-049059 is claimed, and the entire contents of those applications are incorporated herein by reference.

In general, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) exhibit a flexible solid (viscoelastic material) state in a temperature range around room temperature, and have a property of being easily adhered to an adherend by pressure. Taking advantage of these properties, adhesives are widely used for purposes such as bonding, fixing, and protection in various industrial fields such as home appliances, automobiles, various machines, electrical devices, and electronic devices. As an example of the use of the pressure-sensitive adhesive, in a display device such as a liquid crystal display device or an organic EL display device, a polarizing film, a retardation film, a cover window member, and other various light-transmitting members and other members may be bonded together. . Patent Literatures 1 and 2 can be cited as technical documents relating to adhesives for optical members.

Japanese Patent Application Publication No. 2014-169382 Japanese Patent Application Publication No. 2017-128732

Patent Literatures 1 and 2 propose a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer as a main component containing a monomer having a plurality of aromatic rings as a monomer unit, and a pressure-sensitive adhesive formed by crosslinking the pressure-sensitive adhesive composition. However, in the techniques described in Patent Literatures 1 and 2, it is difficult to obtain an adhesive having a higher refractive index than the refractive index of the (meth)acrylic acid ester polymer. On the other hand, a technique for increasing the refractive index by blending particles made of a high refractive index inorganic material (for example, inorganic particles such as zirconium oxide particles and titanium oxide particles) with a resin is also known, but an adhesive containing inorganic particles has a high refractive index and adhesive strength. Since properties (eg, peel strength, flexibility, etc.) are in a trade-off relationship, application to the field of pressure-sensitive adhesive is difficult. In the pressure-sensitive adhesive for optical use, a decrease in optical properties due to mixing of inorganic particles is also a concern.

Therefore, an object of the present invention is to provide a pressure-sensitive adhesive having an improved refractive index by a method suitable for optical use. Another related object is to provide a pressure-sensitive adhesive composition capable of forming such a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive.

The pressure-sensitive adhesive composition provided by this specification contains an acrylic polymer (A) containing 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 acrylic polymer (A). do. The acrylic polymer (A) containing the aromatic ring-containing monomer (m1) as a monomer unit may have a high refractive index. The pressure-sensitive adhesive composition disclosed herein further includes, in addition to the acrylic polymer (A), an additive (H _RO ), which is an organic material having a higher refractive index than the acrylic polymer (A), so that the refractive index is improved by the additive (H _RO ). It is possible to form a pressure-sensitive adhesive compatible with the suppression of decrease in adhesive properties with a good balance. In addition, according to the additive (H _RO ), the refractive index of the pressure-sensitive adhesive can be effectively improved while suppressing a decrease in optical properties (eg transmittance, haze, etc.).

In some preferred embodiments of the technology disclosed herein (including technologies implemented in adhesive compositions, adhesives, adhesive sheets, and other forms. The same applies hereinafter), the refractive index of the additive (H _RO ) is, for example, For example, it may be approximately 1.60 or greater. According to the additive (H _RO ), which is an organic material having a higher refractive index and a refractive index of about 1.60 or higher than that of the acrylic polymer (A), the refractive index of the pressure-sensitive adhesive can be effectively improved.

In some embodiments, the content of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer (A) may be, for example, greater than 0 part by weight and 60 parts by weight or less. The pressure-sensitive adhesive composition containing the additive (H _RO ) at such a content is preferable because it is easy to form an adhesive in which the improvement of the refractive index and the suppression of the decrease in adhesive properties and/or optical properties are compatible with the use of the additive (H _RO ) in a well-balanced manner. do.

In some aspects, the additive (H _RO ) contains at least one compound selected from the group consisting of an aromatic ring-containing compound and a heterocycle-containing compound. The technology disclosed herein can be preferably implemented in an aspect using such a compound as an additive (H _RO ).

In some embodiments, the additive (H _RO ) includes a compound having two or more aromatic rings in one molecule. The technology disclosed herein can be preferably implemented in an aspect using such a compound as an additive (H _RO ). A compound having two or more aromatic rings in one molecule, for example

(i) containing a structure in which two non-condensed aromatic rings are directly chemically bonded, and

(ii) containing a structure in which two aromatic rings are condensed

It may be a compound that satisfies at least one of them. The technology disclosed herein can be preferably implemented in an aspect using such a compound as an additive (H _RO ).

In some aspects, the content of the aromatic ring-containing monomer (m1) in the monomer component constituting the acrylic polymer (A) is 50% by weight or more. Since the acrylic polymer (A) constituted by the monomer component having such a composition can have a high refractive index, it is suitable as the acrylic polymer (A) in the technique disclosed herein.

In some aspects, the content of the aromatic ring-containing monomer (m1) in the monomer component constituting the acrylic polymer (A) is greater than 70% by weight and less than 100% by weight. Such an acrylic polymer (A) is preferable because it is easy to increase the refractive index and easily form a pressure-sensitive adhesive having good adhesive properties.

In some embodiments, 50% by weight or more of the aromatic ring-containing monomer (m1) contained in the monomer component constituting the acrylic polymer (A) may be a monomer having a homopolymer glass transition temperature of 10°C or less. Thereby, even if the content of the aromatic ring-containing monomer (m1) in the monomer component is increased, it is easy to form an adhesive that achieves both a high refractive index and adhesive properties in a well-balanced manner. In the following, the Tg of a homopolymer of a monomer may be expressed as the Tg of the monomer.

In some preferred embodiments, the 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 "a monomer containing multiple aromatic rings"). The refractive index of the pressure-sensitive adhesive can be effectively improved by using a monomer containing a plurality of aromatic rings. The aromatic ring-containing monomer (m1) may contain only one type of aromatic ring-containing monomer (for example, an aromatic ring-containing monomer having a homopolymer Tg of 10°C or less), or two or more aromatic ring-containing monomers. may be included in combination.

In some preferred embodiments, 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. A monomer containing a plurality of aromatic rings having such a structural moiety is a homopolymer, compared to a monomer containing a plurality of aromatic rings having a structural moiety (for example, a biphenyl structure) in which two aromatic rings are directly chemically bonded instead of the structural moiety. Tg of tends to be lower. According to the aromatic ring-containing monomer (m1) containing a monomer containing multiple aromatic rings having such a structure, it is possible to achieve both flexibility suitable as an adhesive and high refractive index in a more well-balanced manner.

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

In the following, when an aromatic ring-containing monomer (m1) is sometimes referred to as "monomer (m1)" and a monomer (m2) having at least one of a hydroxyl group and a carboxyl group is referred to as "monomer (m2)" there is

The pressure-sensitive adhesive composition disclosed herein may further contain a crosslinking agent. By using a crosslinking agent, appropriate cohesiveness can be imparted to the pressure-sensitive adhesive, and handling of the pressure-sensitive adhesive sheet during production, processing, storage, sticking to adherends, and the like can be improved.

According to this specification, a pressure-sensitive adhesive formed from any of the pressure-sensitive adhesive compositions disclosed herein is provided. Such an adhesive may have an improved refractive index while suppressing a decrease in adhesive properties and/or optical properties by including the additive (H _RO ) in addition to the acrylic polymer (A). In one preferred aspect, the refractive index of the pressure-sensitive adhesive may be, for example, greater than 1.570 (preferably 1.575 or more, more preferably 1.580 or more).

According to this specification, a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive (for example, a pressure-sensitive adhesive having a refractive index of more than 1.570, preferably 1.575 or more, more preferably 1.580 or more) formed from any of the pressure-sensitive adhesive compositions disclosed herein. is provided. Such an adhesive sheet can be preferably used in an aspect bonded to a member (for example, an optical member).

In some aspects of the PSA sheet disclosed herein, the Haze value of the PSA layer is 1.0% or less. Such a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having high transparency can be preferably used, for example, in the field of optics.

In addition, an appropriate combination of each element described in this specification may also be included in the scope of the invention requiring protection by a patent according to the present patent application.

1 is a cross-sectional view schematically showing the configuration 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.
Fig. 3 is a cross-sectional view schematically showing an optical member provided with an adhesive sheet in which an adhesive sheet according to an embodiment is attached to an optical member.

Preferred embodiments of the present invention will be described below. Matters other than matters specifically mentioned in this specification and necessary for the practice of the present invention can be understood by those skilled in the art based on the teachings for the practice of the invention described in this specification and common technical knowledge at the time of filing. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

Note that in the following drawings, the same reference numerals may be given to members and parts exhibiting the same action, and overlapping explanations may be omitted or simplified. In addition, the embodiments described in the drawings are modeled in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of products actually provided.

In this specification, a self-luminous element means a light-emitting element capable of controlling the luminance of light emitted by a value of current flowing therethrough. The self-luminous element may be composed of a single body or may be composed of an aggregate. Specific examples of self-luminous devices include, but are not limited to, light emitting diodes (LEDs) and organic ELs. When referring to a light emitting device in this specification, the light emitting device may include such a self-light emitting element as a component. Examples of the light emitting device include, but are not limited to, a light source module device (eg, area light emitting module) used as illumination and a display device in which pixels are formed.

In this specification, the "base polymer" of the pressure-sensitive adhesive refers to the main component of the rubber-like polymer contained in the pressure-sensitive adhesive, and is not construed limitedly at all other than this. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In addition, in this specification, a "main component" refers to a component contained in excess of 50% by weight, unless otherwise specified.

In this specification, "acrylic polymer" refers to a polymer containing a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. 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. As a typical example of the acrylic polymer, a polymer having an acrylic monomer ratio of more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of the total monomers used in the synthesis of the polymer is exemplified.

In addition, in this specification, "(meth)acryloyl" is the meaning which points out acryloyl and methacryloyl comprehensively. Similarly, "(meth)acrylate" means acrylate and methacrylate, and "(meth)acryl" means acryl and methacryl respectively comprehensively. Therefore, the concept of the acrylic monomer here may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

<Adhesive composition>

The pressure-sensitive adhesive composition disclosed herein may form a pressure-sensitive adhesive containing the acrylic polymer (A) (preferably, a pressure-sensitive adhesive containing the acrylic polymer (A) as a base polymer), and the form thereof is not particularly limited. don't The pressure-sensitive adhesive composition is, for example, a solvent-type pressure-sensitive adhesive composition containing a pressure-sensitive adhesive forming component in an organic solvent, an active energy ray-curable pressure-sensitive adhesive composition prepared to form a pressure-sensitive adhesive by being cured by active energy rays such as ultraviolet rays or radiation, pressure-sensitive adhesive It may be in various forms, such as a water-dispersible pressure-sensitive adhesive composition in which forming components are dispersed in water, a hot-melt pressure-sensitive adhesive composition that is applied in a heated and molten state and forms an adhesive when cooled to around room temperature.

(Acrylic Polymer (A))

The pressure-sensitive adhesive composition disclosed herein contains an acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit. The acrylic polymer (A) is a polymer containing an aromatic ring-containing monomer (m1) as a monomer component constituting the acrylic polymer. Here, in the present specification, the "monomer component constituting the acrylic polymer" refers to whether it is included in the pressure-sensitive adhesive composition in the form of a preformed polymer (which may be an oligomer) or an unpolymerized monomer, regardless of whether it is included in the pressure-sensitive adhesive composition. , In the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition, it means a monomer constituting a repeating unit of an acrylic polymer. That is, the monomer component constituting the acrylic polymer may be contained in the pressure-sensitive adhesive composition in any form of a polymer, unpolymer, or partially polymer. From the viewpoint of ease of preparation of the pressure-sensitive adhesive composition, in some embodiments, a pressure-sensitive adhesive composition containing substantially all of the monomer components (for example, 95% by weight or more, preferably 99% by weight or more) in the form of a polymer desirable. A pressure-sensitive adhesive composition containing substantially all of the monomer components in the form of a polymer is also preferable from the viewpoint of being easy to form a pressure-sensitive adhesive sheet with little deformation or warping.

(monomer (m1))

As the monomer (m1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule is used. As a monomer (m1), 1 type of these compounds can be used individually or in combination of 2 or more types.

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 acryloyl group is more preferable from the viewpoint of flexibility or adhesiveness. From the viewpoint of suppressing the decrease in flexibility of the pressure-sensitive adhesive, as the monomer (m1), a compound in which the number of ethylenically unsaturated groups contained in one molecule is 1 (ie, a monofunctional monomer) is preferably used.

The number of aromatic rings contained in one molecule of the compound 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 16 or less, for example. In some aspects, from the viewpoint of the ease of preparation of the acrylic polymer (A) and the transparency of the pressure-sensitive adhesive, the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, It may be 5 or less, 4 or less, 3 or less, or 2 or less.

The aromatic ring of the compound used as the monomer (m1) is, for example, a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); condensed rings of naphthalene rings, indene rings, azulene rings, anthracene rings, and phenanthrene rings; etc. may be a carbocyclic ring, for example, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, thiophene ring; etc., may be a heterocyclic ring. In the heterocycle, heteroatoms included as ring-constituting atoms may be, for example, one or two or more selected from the group consisting of nitrogen, sulfur, and oxygen. In some aspects, the heteroatom constituting the heterocycle may be one or both of nitrogen and sulfur. The monomer (m1) may have a structure in which one or two or more carbocycles and one or two or more heterocycles are condensed, such as a dinaphthothiophene structure.

The aromatic ring (preferably carbocyclic ring) may have one or two or more substituents on the ring-constituting atoms, or may have no substituents. When it has a substituent, examples of the substituent include 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 hydroxyalkyloxy group, a glycidyloxy group, and the like. Although exemplified, it is not limited thereto. In the substituent containing carbon atoms, the number of carbon atoms included in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the aromatic ring is an aromatic ring having no substituents on ring atoms or having one or two or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (for example, a bromine atom). can In addition, that the aromatic ring of the monomer (m1) has a substituent on the ring-constituting atom means that the aromatic ring has a substituent other than the substituent having an ethylenically unsaturated group.

The aromatic ring and the ethylenically unsaturated group may be bonded directly or through a linking group. The linking group is, for example, an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, a group having a structure in which one or two or more hydrogen atoms are substituted with hydroxyl groups in these groups (eg , hydroxyalkylene group), an oxy group (-O- group), a thiooxy group (-S- group), and the like. In some embodiments, an aromatic ring having a structure in which an aromatic ring and an ethylenically unsaturated group are bonded directly or through a linking group selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly(oxyalkylene) group. A monomer can be preferably employed. The number of carbon atoms in the alkylene group and the oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. The number of repetitions of oxyalkylene units in the poly(oxyalkylene) group may be, for example, 2 to 3.

Examples of compounds that can be preferably employed as the monomer (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. An aromatic ring-containing (meth)acrylate and an aromatic ring-containing vinyl compound can be used individually by 1 type or in combination of 2 or more types, respectively. You may use combining 1 type, or 2 or more types of aromatic ring-containing (meth)acrylate, 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 the desired refractive index and adhesive properties (eg peel strength, flexibility, etc.) and/or optical properties (eg, For example, total light transmittance, haze value, etc.) can be set so as to realize an adhesive layer that achieves both. In some embodiments, 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. It can be more than that. From the viewpoint of making it easier to obtain a higher refractive index, in some preferred embodiments, the content of the monomer (m1) may be, for example, more than 70% by weight, 75% by weight or more, or 80% by weight or more. , 85% by weight or more may be sufficient, 90% by weight or more may be sufficient, or 95% by weight or more may be sufficient. The upper limit of the content of the monomer (m1) in the monomer component is 100% by weight. From the viewpoint of achieving both a high refractive index and adhesive characteristics and/or optical characteristics in a well-balanced manner, the content of the monomer (m1) is advantageously less than 100% by weight, for example, preferably approximately 99% by weight or less, and 98 It is more preferably less than or equal to weight%, may be less than or equal to 97% by weight, or less than or equal to 96% by weight. In some embodiments, the content of the monomer (m1) may be 93% by weight or less, 90% by weight or less, 80% by weight or less, or 75% by weight or less. In some embodiments in which adhesive properties and/or optical properties are more important, the content of the monomer (m1) in the monomer component may be 70% by weight or less, 60% by weight or less, or 45% by weight may be below.

In some aspects of the technology disclosed herein, as the monomer (m1), a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule is selected from the viewpoint of easily obtaining a high refractive index effect. can be preferably employed. As an example of a monomer having two or more aromatic rings in one molecule (hereinafter also referred to as "a monomer containing multiple aromatic rings"), a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, and two or more non-condensed aromatic rings are directly ( That is, a monomer having a chemically bonded structure without passing through another atom), a monomer having a condensed aromatic ring structure, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, and the like. can A monomer containing multiple aromatic rings can be used individually by 1 type or in combination of 2 or more types.

The linking group, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (eg -O-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1), a thiooxyalkylene group (eg -S-(CH ₂ ) _n -group, where n is 1 to 3, preferably 1), a straight-chain alkylene group (ie -(CH ₂ ) _n -group, where n is 1 to 6, preferably 1 to 3), the alkylene groups in the oxyalkylene group, the thiooxyalkylene group and the straight-chain alkylene group may be partially halogenated or fully halogenated groups, etc. . From the standpoint of the flexibility of the pressure-sensitive adhesive, etc., suitable examples of the linking group include an oxy group, a thiooxy group, an oxyalkylene group and a straight-chain alkylene group. As a specific example of a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, phenoxybenzyl (meth)acrylate (eg, m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl ( meth)acrylate, benzylbenzyl (meth)acrylate, etc. are mentioned.

The monomer having a structure in which two or more non-condensed aromatic rings are directly chemically bonded may be, for example, biphenyl structure-containing (meth)acrylate, triphenyl structure-containing (meth)acrylate, or vinyl group-containing biphenyl. As a specific example, o-phenylphenol (meth)acrylate, biphenylmethyl (meth)acrylate, etc. are mentioned.

Examples of the monomer having the condensed aromatic ring structure include (meth)acrylate containing a naphthalene ring, (meth)acrylate containing an anthracene ring, naphthalene containing a vinyl group, and anthracene containing a vinyl group. As specific examples, 1-naphthylmethyl (meth)acrylate (alias: 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2- Naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, etc. are mentioned.

As a specific example of the monomer which has the said fluorene structure, 9,9-bis (4-hydroxyphenyl) fluorene (meth) acrylate, 9,9-bis [4- (2-hydroxyethoxy) phenyl] flu Orene (meth)acrylate etc. are mentioned. In addition, since a monomer having a fluorene structure includes a structural portion in which two benzene rings are directly chemically bonded, it is included in the concept of a monomer having a structure in which two or more non-condensed aromatic rings are directly chemically bonded.

Examples of the monomer having the dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include (meth)acryloyloxymethyldinaphthothiophene (for example, a compound having a structure in which CH ₂ CH(R ¹ )C(O)OCH ₂ - is bonded to the 5-position or 6-position of the dinaphthothiophene ring). Here, R ¹ is a hydrogen atom or a methyl group), (meth) acryloyloxyethyl dinaphthothiophene (for example, at the 5-position or 6-position of the dinaphthothiophene ring, CH ₂ CH (R ¹ ) C (O) OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ - compound having a bonded structure, wherein R ¹ is a hydrogen atom or a methyl group), vinyldinaphthothiophene ( For example, a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), (meth)allyloxydinaphthothiophene, and the like. In addition, a monomer having a dinaphthothiophene structure is included in the concept of a monomer having the above-mentioned condensed aromatic ring structure by including a naphthalene structure and also by having a structure obtained by condensing a thiophene ring and two naphthalene structures.

Examples of the monomer having the dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophene and vinyl group-containing dibenzothiophene. In addition, since a monomer having a dibenzothiophene structure has a structure in which a thiophene ring and two benzene rings are condensed, it is included in the concept of a monomer having a condensed aromatic ring structure.

In addition, both a dinaphthothiophene structure and a dibenzothiophene structure do not correspond to the structure which two or more non-condensed aromatic rings chemically bonded directly.

As the monomer (m1) in the technique disclosed herein, a monomer having one aromatic ring (preferably a carbocyclic ring) in one molecule may be used. A monomer having one aromatic ring per molecule can be useful, for example, for improving the flexibility of the pressure-sensitive adhesive, adjusting the adhesive properties, and improving the transparency. In some embodiments, a monomer having one aromatic ring per molecule is preferably used in combination with a monomer containing a plurality of aromatic rings from the viewpoint of improving the refractive index of the pressure-sensitive adhesive.

Examples of monomers having one aromatic ring per molecule include benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, and phenoxypropyl (meth)acrylate. ) Carbon aromatic rings such as acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and chlorobenzyl (meth)acrylate containing (meth)acrylate; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl(meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl(meth)acrylate , 6-(4,6-dibromo-2-s-butylphenoxy)hexyl(meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl(meth)acrylate bromine-substituted aromatic ring-containing (meth)acrylates such as late, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; carbon aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; compounds having a vinyl substituent on the heteroaromatic ring, such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole; etc. can be mentioned.

As the monomer (m1), you may use a monomer having a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group in the various aromatic ring-containing monomers described above and the aromatic ring. In this way, a monomer having an oxyethylene chain interposed between an ethylenically unsaturated group and an aromatic ring can be regarded as an ethoxide product of the original monomer. The repeating number of oxyethylene units (-CH ₂ CH ₂ O-) in the oxyethylene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, for example is 1 Specific examples of the ethoxylated aromatic ring-containing monomer include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, and phenoxyethyl (meth)acrylate. , phenoxydiethylene glycol di(meth)acrylate, etc. are mentioned.

The content of the monomer containing multiple 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 some embodiments, from the viewpoint of facilitating realization of a pressure-sensitive adhesive having a higher refractive index, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) may be, for example, 50% by weight or more, and 70% by weight. It is preferably above, 85% by weight or more may be sufficient, 90% by weight or more may be sufficient, and 95% by weight or more may be sufficient. Substantially 100% by weight of the monomer (m1) may be a monomer containing multiple aromatic rings. That is, as the monomer (m1), only one or two or more aromatic ring-containing monomers may be used. In some aspects, for example, considering the balance between the high refractive index and the adhesive properties and/or optical properties, the content of the monomer containing a plurality of aromatic rings in the monomer (m1) is less than 100% by weight. 98% by weight or less, 90% by weight or less, 80% by weight or less, or 65% by weight or less. In some embodiments, in consideration of adhesive properties and/or optical properties, the content of the monomer containing multiple aromatic rings in the monomer (m1) may be 70% by weight or less, may be 50% by weight or less, or 25% by weight It may be % or less, and may be 10% by weight or less. The technique disclosed herein can also be implemented in an aspect in which the content of the monomer containing multiple aromatic rings in the monomer (m1) is less than 5% by weight. It is not necessary to use a monomer containing multiple aromatic rings.

The content of the monomer component containing a plurality of aromatic rings in the monomer component constituting the acrylic polymer (A) is not particularly limited, and the desired refractive index and adhesive properties (eg peel strength, flexibility, etc.) and/or optical properties (eg For example, total light transmittance, haze value, etc.) can be set so as to realize an adhesive layer that achieves both. 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 some embodiments, from the viewpoint of facilitating realization of a pressure-sensitive adhesive having a higher refractive index, the content of the aromatic ring-containing monomer in the monomer component may be, for example, greater than 35% by weight, or greater than 50% by weight It is preferably 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 aromatic ring-containing monomer in the monomer component may be 100% by weight, but from the viewpoint of achieving a well-balanced high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, It is preferably approximately 99% by weight or less, more preferably 98% by weight or less, may be 96% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, It may be 80% by weight or less, and may be 75% by weight or less. In some embodiments, the content of the aromatic ring-containing monomer in the monomer component may be 70% by weight or less, 50% by weight or less, or 25% by weight in consideration of adhesive properties and / or optical properties. It may be less than, 15 weight% or less may be sufficient, and 5 weight% or less may be sufficient. The technique disclosed herein can also be implemented in an aspect in which the content of the monomer containing multiple aromatic rings in the monomer component is less than 3% by weight.

In some aspects of the technology disclosed herein, as at least a part of the monomer (m1), a high refractive index monomer can be preferably employed. Here, "high refractive index monomer" refers to a monomer whose refractive index is, for example, approximately 1.510 or higher, preferably approximately 1.530 or higher, and more preferably approximately 1.550 or higher. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, but is, for example, 3.000 or less, may be 2.500 or less, or may be 2.000 or less, from the viewpoint of the ease of preparation of the pressure-sensitive adhesive composition and the ease of compatibility with the flexibility suitable as the pressure-sensitive adhesive. It may be 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 a monomer is measured on conditions of a measurement wavelength of 589 nm and a measurement temperature of 25 degreeC using the Abbe refractometer. As an Abbe refractometer, model "DR-M4" by ATAGO or its equivalent can be used. When a nominal value of the refractive index at 25°C is provided by a manufacturer or the like, the nominal value can be employed.

As the high refractive index monomer, those having a corresponding refractive index can be appropriately employed from among the compounds (for example, the compounds and compound groups exemplified above) included in the concept of the aromatic ring-containing monomer (m1) disclosed herein. have. Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, homopolymer Tg: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, homopolymer Tg: 31°C), ethoxylated o- Phenylphenol acrylate (repeating number of oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6 ° C), phenoxyethyl acrylate (refractive index (nD20): 1.517, homopolymer Tg: 2 ℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, homopolymer Tg: -35 ℃), 6-acryloyloxymethyldinaphthothiophene (6MDNTA, refractive index: 1.75) , 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyldinaphthothiophene Opene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793) and the like, but are not limited thereto. does not

The content of the high refractive index monomer (ie, an aromatic ring-containing monomer having a refractive index of about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more) in the monomer (m1) is not particularly limited, and examples include For example, it may be 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some aspects, from the viewpoint of making it easier to obtain a higher refractive index, the content of the high refractive index monomer in the monomer (m1) may be, for example, 50% by weight or more, preferably 70% by weight or more, and 85 It may be 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (m1) may be a high refractive index monomer. In some aspects, for example, from the viewpoint of achieving a well-balanced balance between high refractive index and adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer (m1) may be less than 100% by weight. , 98 wt% or less may be sufficient, 90 wt% or less may be sufficient, 80 wt% or less may be sufficient, and 65 wt% or less may be sufficient. In some embodiments, considering the adhesive properties and / or optical properties, the content of the high refractive index monomer in the monomer (m1) may be 70% by weight or less, 50% by weight or less, or 25% by weight or less may be present, may be 15% by weight or less, or may be 10% by weight or less. The technique disclosed herein can also be implemented in an aspect in which the content of the high refractive index monomer in the monomer component (m1) is less than 5% by weight. It is not necessary 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 the desired refractive index and adhesive properties (eg peel strength, flexibility, etc.) and/or optical properties (eg, 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 some aspects, from the viewpoint of making it easier to realize an adhesive having a higher refractive index, the content of the high refractive index monomer in the monomer component may be, for example, more than 35% by weight, and more than 50% by weight It is preferably 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. Although the content of the high refractive index monomer in the monomer component may be 100% by weight, it is advantageous to set it to less than 100% by weight from the viewpoint of achieving a well-balanced high refractive index and adhesive properties and/or optical properties, and 99% by weight It is preferably 98% by weight or less, more preferably 98% by weight or less, 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less It may be less than or equal to 75% by weight or less. In some embodiments, considering adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer component may be 70% by weight or less, 50% by weight or less, or 25% by weight or less. It may be 15% by weight or less, and may be 5% by weight or less. The technique disclosed herein can also be implemented in an aspect in which the content of the high refractive index monomer in the monomer component is less than 3% by weight.

In some preferred embodiments of the technology disclosed herein, as at least a part of the monomer (m1), the homopolymer has a Tg of 10 ° C or less (preferably 5 ° C or less or 0 ° C or less, more preferably -10 ° C or less) , more preferably -20°C or less, for example -25°C or less) of an aromatic ring-containing monomer (hereinafter sometimes referred to as "monomer L") is employed. When the content of the aromatic ring-containing monomer (m1) in the monomer component (particularly, the aromatic ring-containing monomer (m1) corresponding to one or both of the above-mentioned monomer containing a plurality of aromatic rings and the high refractive index monomer) is increased, the pressure-sensitive adhesive is stored. Since the elastic modulus G' generally tends to increase, the increase in the storage elastic modulus G' can be suppressed by adopting the monomer L as part or all of the monomer (m1). Thereby, the refractive index can be improved while maintaining the flexibility suitable as an adhesive. The lower limit of the Tg of the monomer L is not particularly limited. Considering the balance with the refractive index improving effect, in some embodiments, the Tg of the monomer L may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. Monomer L can be used individually by 1 type or in combination of 2 or more types.

As the monomer L, 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), those having a corresponding Tg can be appropriately employed. One preferred example of the aromatic ring-containing monomer that can be used as the monomer L is m-phenoxybenzyl acrylate (Tg of homopolymer: -35°C). Another preferred 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 some aspects, from the viewpoint of making it easier to obtain an adhesive that achieves both a high refractive index and flexibility at a higher level, the content of the monomer L in the monomer (m1) may be, for example, 50% by weight or more, and 60% by weight It may be % or more, may be 70% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, may be 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be the monomer L. Further, in some aspects, from the viewpoint of, for example, balancing the flexibility and high refractive index suitable as an adhesive, the content of the monomer L in the monomer (m1) may be less than 100% by weight, or 98% by weight. It may be less than, 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 herein can be implemented also in an aspect in which the content of the monomer L in the monomer (m1) is less than 5% by weight. It is not necessary to use monomer L.

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 some aspects, from the viewpoint of making it easier to obtain an adhesive that achieves both a high refractive index and flexibility at a higher level, the content of the monomer L in the monomer component may be, for example, greater than 35% by weight, or greater than 50% by weight It is preferably 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 monomer L in the monomer component may be 100% by weight, but considering the balance between the high refractive index and adhesive properties and/or optical properties, it is advantageous to set it to less than 100% by weight, and about 99% by weight It is preferably less than or equal to, preferably 98% by weight or less, more preferably 96% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80 It may be less than 75% by weight or less than 75% by weight. In some embodiments, the content of the monomer L in the monomer component may be 70% by weight or less, 50% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight may be below. The technique disclosed herein can also be implemented in an aspect in which the content of the monomer L in the monomer component is less than 3% by weight.

In some embodiments, the glass transition temperature Tg _m1 based on the composition of the monomer (m1) is advantageously approximately 20 ° C. or less, and preferably 10 ° C. or less (eg 5 ° C. or less), more preferably 0°C or less, still more preferably -10°C or less, -20°C or less, or -25°C or less. The lower limit of the glass transition temperature Tg _m1 is not particularly limited. Considering the balance with the refractive index improving effect, in some embodiments, the glass transition temperature Tg _m1 may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. The technology disclosed herein may be suitably implemented in an aspect in which 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 based on the composition of the monomer (m1) is Tg obtained by Fox's formula described later based on the composition of only the monomer (m1) among the monomer components constituting the acrylic polymer (A). say The glass transition temperature Tg _m1 is a homopolymer of each aromatic ring-containing monomer used as the monomer (m1) by applying the formula of Fox described below to only the monomer (m1) among the monomer components constituting the acrylic polymer (A). It can be calculated from the glass transition temperature of and the weight fraction of each aromatic ring-containing monomer to the total amount of monomers (m1). In an aspect in which only one type of monomer is used as the monomer (m1), the Tg of the homopolymer of the monomer and the glass transition temperature Tg _m1 are the same.

In some embodiments, as the aromatic ring-containing monomer (m1), monomer L (that is, the Tg of the homopolymer is 10 ° C. or less, preferably 5 ° C. or less or 0 ° C. or less, more preferably -10 ° C. or less, More preferably -20°C or lower, for example, -25°C or lower aromatic ring-containing monomer) and monomer H having a Tg higher than 10°C can be used in combination. The Tg of the monomer H may be, for example, greater than 10°C, greater than 15°C, or greater than 20°C. By using the monomer L and the monomer H in combination, for example, in a configuration in which the content of the aromatic ring-containing monomer (m1) in the monomer component is relatively high, the high refractive index and flexibility of the pressure-sensitive adhesive can be achieved at a higher level. The usage ratio of the monomer L and the monomer H can be set so as to suitably express these effects, and is not particularly limited. For example, it is preferable to set the usage ratio of the monomer L and the monomer H so as to satisfy the glass transition temperature Tg _m1 of any of the above.

In some aspects, the aromatic ring-containing monomer (m1) can be preferably selected from compounds that do not contain a structure in which two or more non-condensed aromatic rings are directly chemically bonded (for example, a biphenyl structure). For example, the content of a compound containing a structure in which two or more non-fused aromatic rings are directly chemically bonded is less than 5% by weight (more preferably less than 3% by weight, and may be 0% by weight) composed of monomer components of a composition. Acrylic polymers are preferred. In this way, limiting the amount of a compound containing a structure in which two or more non-condensed aromatic rings are directly chemically bonded can be advantageous from the viewpoint of realizing a pressure-sensitive adhesive having a well-balanced balance between flexibility and adhesiveness and high refractive index.

(monomer (m2))

In some aspects of the technique disclosed herein, the monomer component constituting the acrylic polymer (A) may further contain a monomer (m2) in addition to the above monomer (m1). The monomer (m2) is a monomer corresponding to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxy group (carboxy group-containing monomer). The hydroxyl group-containing monomer is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The carboxy group-containing monomer is a compound containing at least one carboxy group and at least one ethylenically unsaturated group in one molecule. The monomer (m2) can be useful for introducing a crosslinking point into the acrylic polymer (A) or imparting appropriate cohesiveness to the pressure-sensitive adhesive. Monomer (m2) can be used individually by 1 type or in combination of 2 or more types. The 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 acryloyl group is more preferable from the viewpoint of flexibility or adhesiveness. From the viewpoint of suppressing the decrease in flexibility of the pressure-sensitive adhesive, as the monomer (m2), a compound in which the number of ethylenically unsaturated groups contained in one molecule is 1 (ie, a monofunctional monomer) is preferably used.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and (meth)acrylic acid. Hydroxy (meth)acrylates such as 8-hydroxyoctyl, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate alkyl, but is not limited thereto. Examples of the hydroxyl group-containing monomer that can be preferably 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 more preferred. In a preferred aspect, 50% by weight or more (eg, greater than 50% by weight, greater than 70% by weight or greater than 85% by weight) of the monomer (m2) may be 4-hydroxybutyl acrylate. A hydroxyl group-containing monomer can be used individually by 1 type or in combination of 2 or more types.

In some embodiments using a hydroxyl group-containing monomer as the monomer (m2), the hydroxyl group-containing monomer may be one or two or more selected from compounds having no methacryloyl group. Preferable examples of the hydroxyl group-containing monomer having no methacryloyl group include the various hydroxyalkyl acrylates described above. For example, it is preferable that more than 50 weight%, more than 70 weight%, or more than 85 weight% of the hydroxyl-containing monomer used as a monomer (m2) is hydroxyalkyl acrylate. By using hydroxyalkyl acrylate, a hydroxyl group useful for providing a crosslinking point and imparting appropriate cohesiveness can be introduced into the acrylic polymer (A), and compared to the case where only the corresponding hydroxyalkyl methacrylate is used. It is easy to obtain an adhesive with good flexibility and adhesiveness in the room temperature range.

Examples of the carboxyl group-containing monomer include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. It is not limited to these. Examples of the carboxy group-containing monomer that can be preferably used include acrylic acid and methacrylic acid. Carboxy group-containing monomers can be used individually by 1 type or in combination of 2 or more types. A hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used together.

The content of the monomer (m2) in the monomer component constituting the acrylic polymer (A) is not particularly limited and can be set according to the purpose. In some embodiments, the content of the monomer (m2) may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. From the viewpoint of obtaining a higher use effect, in some embodiments, the content of the monomer (A2) is preferably 1% by weight or more, may be 2% by weight or more, or may be 4% by weight or more. . The upper limit of the content of the monomer (m2) in the monomer component is set such that the sum of the content of the monomer (m1) does not exceed 100% by weight. In some embodiments, the content of the monomer (m2) is suitably, for example, 30% by weight or less or 25% by weight or less, and the content of the monomer (m1) is relatively increased to facilitate high refractive index. From the viewpoint of making it possible, it is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

In the aspect in which a hydroxyl group-containing monomer is used as the monomer (m2), the content of the hydroxyl group-containing monomer in the monomer component is not particularly limited, and is, for example, 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.5% by weight or more). In some aspects, the content of the hydroxyl group-containing monomer is preferably 1% by weight or more, 2% by weight or more, or 4% by weight or more of the monomer component. 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 suitably 30% by weight or less or 25% by weight or less. And, from the viewpoint of relatively increasing the content of the monomer (m1) to facilitate high refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight, It may be less than 10% by weight or less than 7% by weight.

In the aspect using a carboxyl group-containing monomer as the monomer (m2), the content of the carboxy group-containing monomer in the monomer component is not particularly limited, and is, for example, 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.1% by weight or more). preferably 0.3% by weight or more). In some embodiments, the content of the carboxy 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) used does not exceed 100% by weight, and, 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 relatively increasing the content of the monomer (m1) to facilitate high refractive index, it is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight , may be less than 10% by weight. In some aspects, from the viewpoint of improving the flexibility of the pressure-sensitive adhesive, the content of the carboxy group-containing monomer is advantageously less than 7% by weight, preferably less than 5% by weight, and may be less than 3% by weight , It is good also as less than 1 weight%, and good also as less than 0.5 weight%. The technique disclosed herein can be preferably carried out in an aspect using, for example, only a hydroxyl group-containing monomer as the monomer (m2), ie, no carboxyl group-containing monomer.

The total content of the monomer (m1) and the monomer (m2) in the monomer component constituting the acrylic polymer (A) may be, for example, 31% by weight or more, preferably 51% by weight or more, and 61% by weight or more. It may be, or it may be 71% by weight or more. In some aspects, the total content of the monomer (m1) and the monomer (m2) in the monomer component constituting the acrylic polymer (A) is, from the viewpoint of making it easy to exhibit the effect of these monomers appropriately, for example 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%. do.

(monomer m3)

The monomer component constituting the acrylic polymer (A) may contain monomers other than the above-mentioned monomer (m1) and the above-mentioned monomer (m2) as needed. An example of such an optional component is an alkyl (meth)acrylate (hereinafter also referred to as "monomer (m3)"). The monomer (m3) can be useful for adjusting the flexibility of the pressure-sensitive adhesive and improving compatibility within the pressure-sensitive adhesive.

As the monomer (m3), an alkyl (meth)acrylate having a C 1 to C 20 (ie, C _1-20 ) linear or branched chain alkyl group at the ester end can be preferably used. Specific examples of the C _{1-20 alkyl} (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. Isobutyl acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate , (meth)acrylate 2-ethylhexyl, (meth)acrylate isooctyl, (meth)acrylate nonyl, (meth)acrylate isononyl, (meth)acrylate decyl, (meth)acrylate isodecyl, (meth)acrylate undecyl , (meth)acrylate dodecyl, (meth)acrylate tridecyl, (meth)acrylate tetradecyl, (meth)acrylate pentadecyl, (meth)acrylate hexadecyl, (meth)acrylate heptadecyl, (meth)acrylate stearyl, Although isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. are mentioned, it is not limited to these.

In some embodiments, as at least a part of the monomer (m3), an alkyl (meth)acrylate having a homopolymer Tg of -20 ° C or lower (more preferably -40 ° C or lower, for example -50 ° C or lower) can be preferably employed. Such low Tg alkyl (meth)acrylates can be useful for improving the flexibility of the pressure-sensitive adhesive. The lower limit of the Tg of the alkyl (meth)acrylate is not particularly limited, and may be, for example, -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the low-Tg alkyl (meth)acrylate include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and isononyl acrylate (iNA).

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

In the aspect in which the monomer component contains an alkyl (meth)acrylate, the content of the alkyl (meth)acrylate in the monomer component can be set so that the effect of use thereof is exhibited appropriately. In some embodiments, the content of the alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. In some aspects, the content of the 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 such that the sum of the content of the other monomers does not exceed 100% by weight, and may be, for example, less than 50% by weight. In some embodiments, the content of the monomer (m3) may be less than 35% by weight, for example. In general, since the refractive index of alkyl (meth)acrylate is relatively low, it is advantageous to limit the content of the monomer (m3) in the monomer component and increase the content of the monomer (m1) relatively in order to increase the refractive index. . From this point of view, the content of the monomer (m3) is advantageously 24% by weight or less, preferably less than 23% by weight, more preferably less than 20% by weight, may be less than 17% by weight, or 12% by weight of the monomer component. It may be less than 7% by weight, may be less than 3% by weight, or may be less than 1% by weight. It is not necessary to substantially use the monomer (m3).

(other monomers)

The monomer component constituting the acrylic polymer (A) may contain monomers other than the above-mentioned monomers (m1), (m2), and (m3) (hereinafter referred to as “other monomers”) as needed. The above other monomers can be used for purposes such as adjusting the Tg of the acrylic polymer (A), adjusting the adhesive performance, and improving the compatibility in the pressure-sensitive adhesive layer. Said other monomer can be used individually by 1 type or in combination of 2 or more types.

As an example of the said other monomer, the monomer (functional group containing monomer) which has functional groups other than a hydroxyl group and a carboxy group is mentioned. For example, other monomers capable of improving the cohesive force and heat resistance of the pressure-sensitive adhesive include a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and a cyano group-containing monomer. In addition, as a monomer capable of introducing a functional group that can serve as a crosslinking origin in the acrylic polymer (A) or contributing to improvement of peel strength and improvement of compatibility in the pressure-sensitive adhesive layer, an amide group-containing monomer (for example, , (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amino group-containing monomers (eg, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), A monomer having a nitrogen atom-containing ring (eg, N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), an imide group-containing monomer, an epoxy group-containing monomer, a keto group-containing monomer, isocyanate A group-containing monomer, an alkoxysilyl group-containing monomer, etc. are mentioned. In addition, among the monomers having a nitrogen atom-containing ring, there are also those corresponding to amide group-containing monomers, such as N-vinyl-2-pyrrolidone. The same applies to the relationship between the monomer having a nitrogen atom-containing ring and the amino group-containing monomer.

Examples of other monomers that can be used other than the functional group-containing monomer include vinyl ester monomers such as vinyl acetate; non-aromatic ring-containing (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; olefinic monomers such as ethylene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and ethoxyethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether; etc. can be mentioned. As a suitable example of another monomer that can be used for the purpose of improving the flexibility of the pressure-sensitive adhesive, etc., ethoxyethoxyethyl acrylate (alias: ethyl carbitol acrylate, homopolymer Tg: -67°C) can be mentioned.

In the case of using the above other monomers, the amount used is not particularly limited, and the total amount of the monomer components can be appropriately set within a range not exceeding 100% by weight. In some embodiments, from the viewpoint of facilitating the use of the monomer (m1) to exhibit the effect of improving the refractive index, the content of the other monomers in the monomer component can be, for example, approximately 35% by weight or less. It is appropriate to be about 25% by weight or less (for example, 0 to 25% by weight), about 20% by weight or less (eg 0 to 20% by weight), or about 10% by weight or less. It may be 5% by weight or less, and may be approximately 1% by weight or less. The technology disclosed herein can be preferably implemented in an aspect in which the monomer component does not substantially contain the other monomers.

In some aspects, the monomer component constituting the acrylic polymer (A) may be a composition in which the amount of the methacryloyl group-containing monomer used is suppressed to a predetermined level or less. The amount of the methacryloyl group-containing monomer used in the monomer component may be, for example, less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. Limiting the amount of the methacryloyl group-containing monomer used in this way can be advantageous from the viewpoint of realizing a pressure-sensitive adhesive in which flexibility, adhesiveness, and high refractive index are well-balanced. 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 consisting only of an acryloyl group-containing monomer).

In some aspects, it is preferable that the monomer component constituting the acrylic polymer (A) uses a limited amount of the carboxy group-containing monomer from the viewpoint of suppressing coloring or discoloration (for example, yellowing) of the pressure-sensitive adhesive. The amount of the carboxyl group-containing monomer used in the monomer component may be, for example, less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.3% by weight, less than 0.1% by weight, or less than 0.05% by weight. may be continued The reason why the amount of the carboxy group-containing monomer is limited is because of the corrosion of a metal material (eg, a metal wire or a metal film that may be present on an adherend) that may be placed in contact with or in proximity to the pressure-sensitive adhesive disclosed herein. It is also advantageous from the point of view of suppressing The technology disclosed herein can be preferably implemented in an aspect in which the monomer component does not contain a carboxy group-containing monomer.

For the same reason, in some embodiments, the monomer component constituting the acrylic polymer (A) has an acidic functional group (including a sulfonic acid group, a phosphoric acid group, etc. in addition to a carboxyl group). It is preferable that the amount of monomer used is limited. do. As the usage amount of the acidic functional group-containing monomer in the monomer component of this aspect, the preferred usage amount of the carboxyl group-containing monomer described above can be applied. The technology disclosed herein can be preferably implemented in an aspect in which the monomer component does not contain an acidic group-containing monomer (ie, an aspect in which the acrylic polymer (A) is acid-free).

(glass transition temperature Tg _T )

In some aspects, the monomer component constituting the acrylic polymer (A) has a glass transition temperature Tg _T based on the composition of the monomer component, preferably about 20 ° C. or less, preferably about 10 ° C. or less, It is more preferably 0°C or lower, and may be -10°C or lower, -20°C or lower, -25°C or lower, -28°C or lower, or -30°C or lower. A low glass transition temperature Tg _T can be advantageous from the viewpoint of improving the flexibility of the pressure-sensitive adhesive. Further, the glass transition temperature Tg _T may be, for example, -60°C or higher, and from the viewpoint of facilitating high refractive index of the pressure-sensitive adhesive, it is preferably -50°C or higher, more preferably -45°C or higher, It may be more than -40°C, may be more than -35°C, may be more than -25°C, may be more than -15°C, may be more than -5°C.

Here, glass transition temperature Tg _T means the glass transition temperature calculated|required by Fox's formula based on the composition of the said monomer component, unless otherwise specified. As described below, Fox's formula is a relational expression between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerization of each of the monomers constituting the copolymer.

1/Tg = Σ (Wi/Tgi)

In the above formula of Fox, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio by weight), and Tgi is the homopolymer of the monomer i Shows the glass transition temperature (unit: K).

As the glass transition temperature of the homopolymer used for calculation of Tg, a value described in known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For a monomer for which a plurality of types of values are described in the above Polymer Handbook, the highest value is adopted. When the Tg of the homopolymer is not described in publicly known materials, the value obtained by the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 shall be used.

(Preparation method of acrylic polymer (A))

In the technology disclosed herein, the method for obtaining the acrylic polymer (A) composed of such monomer components is not particularly limited, and solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. , various polymerization methods known as methods for synthesizing acrylic polymers can be appropriately employed. For example, a solution polymerization method can be preferably employed. The polymerization temperature when performing solution polymerization can be appropriately selected according to the types of monomers and solvents used, the type of polymerization initiator, etc., and is, for example, about 20°C to 170°C (typically about 40°C to 140°C). can do.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) such as toluene; Acetate esters, such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one type of solvent selected from the like or a mixed solvent of two or more types can be used.

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

For the above polymerization, conventionally known various chain transfer agents can be used as needed. For example, mercaptans such as n-dodecylmercaptan, t-dodecylmercaptan, thioglycolic acid, and α-thioglycerol can be used. Alternatively, a chain transfer agent (non-sulfur chain transfer agent) that does not contain a sulfur atom may 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; styrenes such as α-methylstyrene and α-methylstyrene dimer; etc. can be mentioned. A chain transfer agent can be used individually by 1 type or in combination of 2 or more types. The usage amount in the case of using a chain transfer agent can be, for example, about 0.01 to 1 part by weight with respect to 100 parts by weight of the monomer raw material.

The weight average molecular weight (Mw) of the acrylic polymer (A) is not particularly limited, and may be, for example, approximately in the range of 10×10 ⁴ to 500×10 ⁴ . From the standpoint of adhesive performance, the Mw of the acrylic polymer (A) is approximately 20×10 ⁴ to 400×10 ⁴ (more preferably approximately 30×10 ⁴ to 150×10 ⁴ , for example approximately 50×10 4 to approximately 50×10 ⁴ to It is preferably in the range of 130×10 ⁴ ).

Here, Mw of the acrylic polymer (A) can be calculated in terms of 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: 10 μL

Eluent: tetrahydrofuran (THF)

Flow rate (flow rate): 0.6 mL/min

Column temperature (measurement temperature): 40°C

column:

Sample column: 1 brand name "TSKguardcolumn SuperHZ-H" + 2 brand names "TSKgel SuperHZM-H" (manufactured by Tosoh Corporation)

Reference column: 1 product name “TSKgel SuperH-RC” (manufactured by Tosoh Corporation)

Detector: Differential Refractometer (RI)

Standard Sample: Polystyrene

(Additive (H _RO ))

As the additive (H _RO ) in the technique disclosed herein, an organic material having a higher refractive index is used in a relative relationship with the acrylic polymer (A) described above. Here, "H _RO " indicates that it is an organic material with a high refractive index. By using such an additive (H _RO ) in combination with the acrylic polymer (A), an adhesive that satisfies the refractive index and adhesive properties (peel strength, flexibility, etc.) and/or optical properties (total light transmittance, haze value, etc.) can be obtained. It can be realized. The organic material used as the additive (H _RO ) may be a polymer or a non-polymer. In addition, it may or may not have a polymerizable functional group. The additive (H _RO ) can be used individually by 1 type or in combination of 2 or more types.

Since the refractive index of the additive (H _RO ) can be set within a suitable range in relation to the refractive index of the acrylic polymer (A), 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 pressure-sensitive adhesive, in some embodiments, the refractive index of the additive (H _RO ) is advantageously 1.58 or higher, preferably 1.60 or higher, more preferably 1.63 or higher, may be 1.65 or higher, or may be 1.70 or higher. It may be greater than or equal to 1.75. According to the additive (H _RO ) having a higher refractive index, the target refractive index can be achieved even by using a smaller amount of the additive (H _RO ). This is preferable from the viewpoint of suppressing deterioration of adhesive properties and optical properties. The upper limit of the refractive index of the additive (H _RO ) is not particularly limited, but is, for example, 3.000 or less, or 2.500 or less, from the viewpoints of compatibility in the adhesive, high refractive index, and compatibility of flexibility suitable for the adhesive. It may be 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 ) is measured using an Abbe refractometer under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C, similarly to the refractive index of the monomer. When a nominal value of the refractive index at 25°C is provided by a manufacturer or the like, the nominal value can be employed.

The difference between the refractive index n _b of the additive ( _HRO ) and the refractive index n _a of the acrylic polymer (A), that is, n _b -n _a (hereinafter also referred to as "Δn _A ") is set to be larger than zero. In some 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 that Δn _A becomes larger, the effect of improving the refractive index by use of the additive (H _RO ) tends to increase. Further, from the viewpoint of the compatibility of the additive (H _RO ) in the pressure-sensitive adhesive layer, in some embodiments, Δn _A may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or It may be 0.35 or less.

In some embodiments, the difference between the refractive index n _b of the additive (H _RO ) and the refractive index n _T of the pressure-sensitive adhesive layer containing the additive (H _RO ), that is, n _b -n _T (hereinafter also referred to as "Δn _B " ) can be set to be greater than 0. In some 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 pressure-sensitive adhesive layer and the additive (H _RO ) so that Δn _B becomes larger, the effect of improving the refractive index by use of the additive (H _RO ) tends to increase. Further, from the viewpoints of compatibility in the pressure-sensitive adhesive layer, transparency of the pressure-sensitive adhesive layer, etc., in some embodiments, Δn _B may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 It may be less than 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. From the viewpoint of balancing the effect of high refractive index with other properties (for example, optical properties such as flexibility and haze suitable for pressure-sensitive adhesives) in a well-balanced manner, in some embodiments, the molecular weight of the additive (H _RO ) is approximately 10000 It is suitably less than 5000, preferably less than 3000 (for example, less than 1000), more preferably less than 800, less than 600, less than 500, or less than 400. The fact that the molecular weight of the additive (H _RO ) is not too large can be advantageous from the viewpoint of improving the compatibility in the pressure-sensitive adhesive layer. In addition, the molecular weight of the additive (H _RO ) may be, for example, 130 or more, or 150 or more. In some embodiments, the molecular weight of the additive (H _RO ) is preferably 170 or more, more preferably 200 or more, may be 230 or more, or 250 or more, from the viewpoint of increasing the refractive index of the additive (H _RO ) It may be 270 or more, 500 or more, 1000 or more, or 2000 or more may be sufficient. In some aspects, a polymer having a molecular weight of about 1000 to about 10000 (for example, 1000 or more and less than 5000) can be used as the additive (H _RO ).

As the molecular weight of the additive (H _RO ), for non-polymers or polymers with low polymerization degree (for example, about 2 to 5 polymers), the molecular weight calculated based on the chemical structure, or matrix-assisted laser desorption ionization time-of-flight mass spectrometry ( MALDI-TOF-MS) can be used. When the additive (H _RO ) is a polymer having a higher polymerization degree, a weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. When a nominal value of molecular weight is provided by a manufacturer or the like, the nominal value can be employed.

Examples of organic materials that can be selected as the additive (H _RO ) include organic compounds having an aromatic ring, organic compounds having a heterocyclic ring (which may be an aromatic ring or non-aromatic heterocycle), and the like. is not limited to

The aromatic ring of the organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") used as the additive (H _RO ) may be selected from the same aromatic rings as those of the compound used as the monomer (m1). can

The aromatic ring may have one or two or more substituents on ring-constituting atoms, and may have no substituents. When it has a substituent, examples of the substituent include 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 hydroxyalkyloxy group, a glycidyloxy group, and the like. Although exemplified, it is not limited thereto. In the substituent containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1 to 10, advantageously 1 to 6, preferably 1 to 4, more preferably 1 to 10. 3, and may be, for example, 1 or 2. In some embodiments, the aromatic ring is an aromatic ring having no substituents on ring atoms or having one or two or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (for example, a bromine atom). can

Examples of aromatic ring-containing compounds that can be used as the additive (H _RO ) include, for example: compounds that can be used as the monomer (m1); an oligomer containing as a monomer unit a compound that can be used as the monomer (m1); From the compound that can be used as the monomer (m1), a hydrogen atom or an ethylenically unsaturated group, except for a group having an ethylenically unsaturated group (which may be a substituent bonded to a ring constituent atom) or a portion constituting an ethylenically unsaturated group in the group Compounds with structures substituted with groups not having (eg, hydroxyl group, amino group, halogen atom, alkyl group, alkoxy group, hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc.); Although the etc. are mentioned, it is not limited to these. Non-limiting examples of aromatic ring-containing compounds that can be used as additives (H _RO ) include benzyl acrylate, m-phenoxybenzyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, and phenoxyethyl acrylate. rate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, a monomer having the above-mentioned fluorene structure, a monomer having a dinaphthothiophene structure, dibenzothio aromatic ring-containing monomers such as monomers having an opene structure; 3-phenoxybenzyl alcohol, dinaphthothiophene and derivatives thereof (for example, the dinaphthothiophene ring has one or two or more substituents selected from a hydroxyl group, a methanol group, a diethanol group, a glycidyl group, etc. aromatic ring-containing compounds having no ethylenically unsaturated group, such as compounds having a structure in which 1 or 2 or more are bonded together); etc. may be included. Further, the aromatic ring-containing compound is an oligomer containing such an aromatic ring-containing monomer as a monomer unit (preferably an oligomer having a molecular weight of about 5000 or less, more preferably about 1000 or less. For example, about 2 to 5 monomers low polymers). The oligomer may be, for example: a homopolymer of an aromatic ring-containing monomer; copolymers of one or two or more aromatic ring-containing monomers; copolymers of one or two or more aromatic ring-containing monomers with other monomers; etc. As said other monomer, 1 type(s) or 2 or more types of monomers which do not have an aromatic ring can be used.

In some aspects, as an additive (H _RO ), an organic compound having two or more aromatic rings in one molecule (hereinafter also referred to as “a compound containing multiple aromatic rings”) from the viewpoint that a high refractive index-raising effect is easily obtained ) can be preferably employed. The compound containing multiple aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. In addition, the compound containing multiple aromatic rings may be a polymer or a non-polymer. In addition, the above-mentioned polymer is an oligomer (preferably an oligomer having a molecular weight of about 5000 or less, more preferably about 1000 or less. For example, a low polymer of about 2 to 5 monomers) containing a monomer containing a plurality of aromatic rings as a monomer unit. can be The oligomer may be, for example: a homopolymer of a monomer containing a plurality of aromatic rings; copolymers of one or two or more aromatic ring-containing monomers; copolymers of one or two or more aromatic ring-containing monomers and other monomers; etc. The other monomer may be an aromatic ring-containing monomer that does not correspond to the monomer containing multiple aromatic rings, a monomer without an aromatic ring, or a combination thereof.

Non-limiting examples of compounds containing multiple aromatic rings include compounds having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, compounds having a structure in which two or more non-condensed aromatic rings are directly (ie, not through other atoms) chemically bonded, A compound having a condensed aromatic ring structure, a compound having a fluorene structure, a compound having a dinaphthothiophene structure, a compound having a dibenzothiophene structure, and the like are exemplified. A compound containing multiple aromatic rings can be used individually by 1 type or in combination of 2 or more types.

As a specific example of the compound having the fluorene structure, 9,9-bis (4-hydroxyphenyl) fluorene (refractive index: 1.68, in addition to the monomer having the above-mentioned fluorene structure and oligomers that are homopolymers or copolymers of these monomers) ), 9,9-bis (4-aminophenyl) fluorene (refractive index: 1.73), 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (refractive index: 1.68), 9,9-bis [ 9,9-bisphenylfluorene and derivatives thereof, such as 4-(2-hydroxyethoxy)phenyl]fluorene (refractive index: 1.65).

As a specific example of the compound which has the said dinaphthothiophene structure, Dinaphthothiophene (refractive index: 1.808) other than the monomer which has the above-mentioned dinaphthothiophene structure, the oligomer which is a homopolymer or a copolymer of this monomer; hydroxyalkyl dinaphthothiophenes such as 6-hydroxymethyldinaphthothiophene (refractive index: 1.766); dihydroxydinaphthothiophenes such as 2,12-dihydroxydinaphthothiophene (refractive index: 1.750); dihydroxyalkyloxydinaphthothiophenes such as 2,12-dihydroxyethyloxydinaphthothiophene (refractive index: 1.677); diglycidyloxydinaphthothiophenes such as 2,12-diglycidyloxydinaphthothiophene (refractive index: 1.723); dinaphthothiophenes having two or more ethylenically unsaturated groups such as 2,12-diallyloxydinaphthothiophene (abbreviation: 2,12-DAODNT, refractive index: 1.729); and the like, dinaphthothiophene and derivatives thereof.

As specific examples of the compound having the dibenzothiophene structure, dibenzothiophene (refractive index: 1.607), 4-dimethyldi, in addition to monomers having the above-mentioned dibenzothiophene structure and oligomers that are homopolymers or copolymers of these monomers. Benzothiophene (refractive index: 1.617), 4,6-dimethyldibenzothiophene (refractive index: 1.617), and the like.

Examples of the organic compound having a heterocycle (hereinafter, also referred to as a heterocycle-containing organic compound) that can be used as an additive (H _RO ) include a thioepoxy compound and a compound having a triazine ring. Examples of the thioepoxy compound include bis(2,3-epithiopropyl) disulfide described in Japanese Patent No. 3712653 and a polymer thereof (refractive index: 1.74). Examples of the compound having a triazine ring include compounds having at least one (for example, 3 to 40, preferably 5 to 20) triazine rings in one molecule. In addition, since the triazine ring has aromaticity, the compound having a triazine ring is also included in the concept of the compound containing an aromatic ring, and the compound having a plurality of triazine rings is also included in the concept of the compound containing a plurality of aromatic rings.

In some aspects, as the additive (H _RO ), a compound having no ethylenically unsaturated group can be preferably employed. Thereby, deterioration (advance of gelation or decrease in leveling property due to increase in viscosity) of the pressure-sensitive adhesive composition due to heat or light can be suppressed, and storage stability can be improved. Adoption of an additive (H _RO ) having no ethylenically unsaturated group is a reaction of ethylenically unsaturated groups in a PSA sheet having a PSA layer containing the additive (H _RO ) or a laminate including the PSA sheet. It is also preferable from the viewpoint of suppressing dimensional change or deformation (bending, waviness, etc.), occurrence of optical distortion, and the like due to .

In the aspect using an oligomer as the additive (H _RO ), the oligomer can be obtained by polymerizing a corresponding monomer component by a known method. When the oligomer is produced by radical polymerization, polymerization can be performed by appropriately adding a polymerization initiator, chain transfer agent, emulsifier, etc. used for radical polymerization to the monomer component. The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited, and can be appropriately selected and used. In addition, the weight average molecular weight of an oligomer is controllable by the usage-amount of a polymerization initiator and chain transfer agent, and reaction conditions, and the usage-amount is adjusted suitably according to these types.

As said chain transfer agent, for example, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, α-thioglycerol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, 2,3-dimer Capto-1-propanol etc. are mentioned. A chain transfer agent may be used individually by 1 type, and may mix and use 2 or more types. The amount of chain transfer agent used can be set so as to obtain an oligomer having a desired weight average molecular weight, depending on the composition of the monomer component used in the synthesis of the oligomer, the type of chain transfer agent, and the like. In some embodiments, the amount of chain transfer agent used for 100 parts by weight of the total amount of monomers used in the synthesis of oligomers is suitably about 15 parts by weight or less, may be 10 parts by weight or less, or about 5 parts by weight or less. may be The lower limit of the amount of the chain transfer agent used per 100 parts by weight of the total amount of monomers used in the synthesis of the oligomer is not particularly limited, but may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more. , 1 part by weight or more may be sufficient.

The amount of the additive (H _RO ) used (in the case of using a plurality of compounds, the total amount thereof) relative to 100 parts by weight of the acrylic polymer (A) is not particularly limited as long as it exceeds 0 parts by weight, and can be set according to the purpose. have. In some embodiments, the amount of the additive ( _HRO ) relative to 100 parts by weight of the acrylic polymer (A) can be, for example, 80 parts by weight or less, and the refractive index of the pressure-sensitive adhesive is increased and the adhesive properties and optical properties are improved. It is advantageous to set it as 60 parts by weight or less, and it is preferable to set it as 45 parts by weight or less from the viewpoint of achieving both suppression of decrease in a well-balanced manner. In some aspects in which adhesive properties and optical properties are more important, the amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer (A) may be, for example, 30 parts by weight or less, even if it is 20 parts by weight or less. It may be 15 parts by weight or less, and may be 10 parts by weight or less. In addition, from the viewpoint of increasing the refractive index of the pressure-sensitive adhesive, the amount of the additive (H _RO ) relative to 100 parts by weight of the acrylic polymer (A) can be, for example, 1 part by weight or more, and it is advantageous to set it to 3 parts by weight or more. It is preferably 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more.

(crosslinking agent)

The pressure-sensitive adhesive composition disclosed herein may contain a crosslinking agent as necessary for the purpose of adjusting the cohesive force of the pressure-sensitive adhesive. As the crosslinking agent, crosslinking agents known in the field of pressure-sensitive adhesives such as isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, oxazoline crosslinking agents, melamine resins, and metal chelate crosslinking agents can be used. Among them, an isocyanate-based crosslinking agent can be preferably employed. Other examples of the crosslinking agent include monomers having two or more ethylenically unsaturated groups in one molecule, that is, polyfunctional monomers. 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 higher 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; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), and 1,3-bis(isocyanatomethyl)cyclohexane; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate (XDI); modified polyisocyanate obtained by modifying the isocyanate compound with an allophanate bond, a biuret bond, an isocyanurate bond, a uretdione bond, a urea bond, a carbodiimide bond, a uretonimine bond, an oxadiazinetrione bond, or the like; etc. can be mentioned. As an example of a commercial item, the trade name Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N (above, Takeda Yakuhin Kogyo Co., Ltd.), Smidur T80, Smidur L, Desmodur N3400 (above, Sumika Bayer Urethane Co., Ltd.), Milionate MR, Milionate MT, Coronate L, Coronate HL, Coronate HX (above, manufactured by Tosoh Corporation), etc. are mentioned. An isocyanate compound can be used individually by 1 type or in combination of 2 or more types. A bifunctional isocyanate compound and a trifunctional or higher functional isocyanate compound may be used together.

As an epoxy crosslinking agent, for example, bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6 -hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N', N'-tetraglycidyl-m-xylylenediamine and 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane etc. are mentioned. 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, polypropylene glycol di(meth)acrylate, neopentyl glycol di( meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexane Dioldi(meth)acrylate, 1,12-dodecanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetri(meth)acrylate, allyl(meth)acrylate, vinyl (meth)acrylate, divinylbenzene, bisphenoxyethanol fluorenedi(meth)acrylate, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, ) acrylate, hexyldioldi(meth)acrylate, etc. are mentioned. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The amount used in the case of using a crosslinking agent (which may be a polyfunctional monomer) is not particularly limited, and may be, for example, in the range of about 0.001 part by weight to about 5.0 parts by weight based on 100 parts by weight of the monomer component. . From the viewpoint of improving the flexibility of the pressure-sensitive adhesive, in some embodiments, the amount of the crosslinking agent based on 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, even if it is 1.0 parts by weight or less. It may be 0.5 parts by weight or less, or 0.2 parts by weight or less. Further, from the viewpoint of appropriately exhibiting the effect of using the crosslinking agent, in some embodiments, the amount of the crosslinking agent relative to 100 parts by weight of the monomer component may be, for example, 0.005 parts by weight or more, or 0.01 parts by weight or more, 0.05 part by weight or more may be sufficient, and 0.08 part by weight or more may be sufficient.

In order to advance a crosslinking reaction more effectively, you may use a crosslinking catalyst. Examples of the cross-linking catalyst include metal-based cross-linking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, butyl tin oxide, and dioctyl tin dilaurate. Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst relative to 100 parts by weight of the monomer component may be, for example, approximately 0.0001 part by weight or more and 1 part by weight or less, in consideration of the balance between the speed of the crosslinking reaction rate and the length of the pot life of the pressure-sensitive adhesive composition. , It is preferable to set it as the range of 0.001 weight part or more and 0.5 weight part or less.

The pressure-sensitive adhesive composition may contain a compound that generates keto-enol tautomerism as a crosslinking retardant. Thereby, the effect of extending the pot life of the pressure-sensitive adhesive composition can be realized. For example, in the pressure-sensitive adhesive composition containing an isocyanate-based crosslinking agent, a compound that generates keto-enol tautomerism can be preferably used. As the compound generating keto-enol tautomerism, various β-dicarbonyl compounds can be used. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetate esters (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably employed. Compounds that generate keto-enol tautomerism can be used alone or in combination of two or more. The amount of the compound generating keto-enol tautomerism can be, for example, 0.1 part by weight or more and 20 parts by weight or less, or 0.5 part by weight or more and 10 parts by weight or less, based on 100 parts by weight of the monomer component. It is good also considering it as 5 parts weight or less by weight part or more.

(tackifier)

The adhesive composition disclosed herein may contain a tackifier. As the tackifier, rosin-based tackifying resin, terpene-based tackifying resin, phenol-based tackifying resin, hydrocarbon-based tackifying resin, ketone-based tackifying resin, polyamide-based tackifying resin, epoxy-based tackifying resin, elastomer-based Well-known tackifying resins, such as tackifying resin, can be used. These can be used individually by 1 type or in combination of 2 or more types. The amount of the tackifying resin used is not particularly limited, and can be set so that appropriate adhesion performance is exhibited depending on the purpose or use. In some embodiments, from the viewpoint of refractive index or transparency, the amount of the tackifier used per 100 parts by weight of the monomer component is suitably 30 parts by weight or less, preferably 10 parts by weight or less, and 5 parts by weight It is more preferable to set it as part or less. The technique disclosed herein can be preferably carried out in an aspect without using a tackifier.

(plasticized material)

In some aspects of the pressure-sensitive adhesive composition disclosed herein, the pressure-sensitive adhesive composition may further contain, as desired, a plasticizing material having a lower molecular weight than the acrylic polymer (A) as an additive. By using a plasticizing material, the flexibility of the pressure-sensitive adhesive layer can be enhanced, and the adhesion to the adherend, the flexibility of the entire pressure-sensitive adhesive sheet, and the conformability to deformation can be improved. As the plasticizing material, an organic material can be preferably employed from the viewpoint of compatibility and transparency in the pressure-sensitive adhesive layer. The plasticizing material may be a material that can be used also as the above-mentioned additive (H _RO ).

The molecular weight of the plasticizing material should just be lower than that of the acrylic polymer (A), and is not particularly limited. In some embodiments, the molecular weight of the plasticizing material may be 30000 or less, 25000 or less, or less than 10000, preferably less than 5000, preferably less than 3000 (eg, For example, less than 1000) is more preferable, and may be less than 800, less than 600, less than 500, or less than 400. If the molecular weight of the plasticizing material is not too large, it may be advantageous from the viewpoint of improving the compatibility in the pressure-sensitive adhesive layer. Further, in some embodiments, the molecular weight of the plasticizing material is preferably 130 or more, preferably 150 or more, may be 170 or more, or may be 200 or more, from the viewpoint of making it easy to exhibit a sufficient plasticizing effect. 250 or more may be sufficient, and 300 or more may be sufficient. In some aspects, the molecular weight of the plasticizing material may be 500 or more, 1000 or more, or 2000 or more. It is preferable also from the viewpoint of the heat resistance performance of the pressure-sensitive adhesive sheet and the stain suppression of the adherend that the molecular weight of the plasticizing material is not too low.

Non-limiting examples of compounds that can be selected as plasticizing materials include compounds that can be used as the monomer (m1) (eg, (meth)acrylates having an aromatic ring such as a benzyl group, a phenoxy group, or a naphthyl group). , a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, etc.); an oligomer containing as a monomer unit a compound that can be used as the monomer (m1); Compounds having a structure substituted with hydrogen atoms or groups having no ethylenically unsaturated groups, excluding portions having ethylenically unsaturated groups, from compounds that can be used as the monomer (m1) (eg, 3-phenoxybenzyl alcohol); etc. are included. From the viewpoint of improving flexibility, a low Tg monomer such as n-butyl acrylate or 2-ethylhexyl acrylate may be copolymerized in the oligomer containing the compound that can be used as the monomer (m1) as a monomer unit, for example. As the plasticizer, one or two or more of known plasticizers (for example, phthalic acid esters, terephthalic acid esters, adipic acid esters, adipic acid polyesters, benzoic acid glycol esters, etc.) may be used.

In some aspects, as the plasticizing material, an organic material having a refractive index of approximately 1.50 or more (more preferably 1.53 or more) can be preferably used. 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-ethyl Biphenyl (refractive index 1.59), 3-methoxybiphenyl (refractive index 1.61), 4-methoxybiphenyl (refractive index 1.57), polyethylene glycol dibenzoate, 3-phenoxybenzyl alcohol (refractive index 1.59), triphenyl phosphate (refractive index 1.56 ), benzyl benzoate (refractive index 1.57), 4-(tert-butyl)phenyldiphenylphosphate (refractive index 1.56), trimethylphenylphosphate (refractive index 1.55), butylbenzylphthalate (refractive index 1.54), rosin methyl ester (refractive index 1.53), alkyl Benzyl phthalate (refractive index 1.53), butyl (phenylsulfonyl)amine (refractive index 1.53), trimethyl trimellitate (refractive index 1.52), benzyl phthalate (refractive index 1.52), 2-ethylhexyldiphenyl phosphate (refractive index 1.51), trisphosphite ( 2,4-di-tert-butylphenyl) and the like, but are not limited thereto. From the viewpoint of refractive index and compatibility, for example, diethylene glycol dibenzoate can be preferably employed. 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 viewpoints of ease of preparation of the pressure-sensitive adhesive composition and compatibility within the pressure-sensitive adhesive, the refractive index of the plasticized material is suitably 2.50 or less, preferably 2.00 or less, may be 1.90 or less, or 1.80 It may be less than or equal to 1.70.

In addition, the refractive index of a plasticized material is measured using the Abbe refractometer similarly to the refractive index of a monomer on condition of a measurement wavelength of 589 nm and a measurement temperature of 25 degreeC. When a nominal value of the refractive index at 25°C is provided by a manufacturer or the like, the nominal value can be employed.

In the aspect of using the plasticizing material, the amount of the plasticizing material used per 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 enhancing the plasticizing effect, the amount of the plasticizing material used per 100 parts by weight of the acrylic polymer (A) may be, for example, 0.1 parts by weight or more, or 0.5 parts by weight or more, from the viewpoint of obtaining a higher plasticizing effect is preferably 1 part by weight or more, more preferably 3 parts by weight or more, may be 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, 20 parts by weight or more may be sufficient. In addition, from the viewpoint of achieving both the high refractive index of the pressure-sensitive adhesive and the transparency and plasticizing effect in a well-balanced manner, the amount of plasticizer used per 100 parts by weight of the acrylic polymer (A) is suitably approximately 100 parts by weight or less, and 80 parts by weight It is preferably less than 60 parts by weight, more preferably less than 60 parts by weight, may be 45 parts by weight or less, may be 35 parts by weight or less, or may be 25 parts by weight or less. In some aspects in which adhesive properties and optical properties are more important, the amount of plasticizing material used per 100 parts by weight of the acrylic polymer (A) may be 15 parts by weight or less, may be 10 parts by weight or less, or 5 parts by weight may be below.

(leveling agent)

The pressure-sensitive adhesive composition disclosed herein may contain a leveling agent as necessary for the purpose of improving the appearance of the pressure-sensitive adhesive layer formed of the composition (for example, improving the uniformity of thickness) or improving the coatability of the pressure-sensitive adhesive composition. can Non-limiting examples of the leveling agent include acrylic leveling agents, fluorine-based leveling agents, silicone-based leveling agents, and the like. An appropriate leveling agent can be selected from commercially available leveling agents and used according to a conventional method, for example.

In some aspects, as the leveling agent, a monomer having a polyorganosiloxane skeleton (hereinafter also referred to as "monomer S1") and a monomer raw material containing an acrylic monomer (hereinafter also referred to as "monomer raw material B") of A polymer that is a polymer (hereinafter, also referred to as "polymer (B)") can be preferably used. Polymer (B) can be said to be a copolymer of monomer S1 and an acrylic monomer. Polymer (B) can be used individually by 1 type or in combination of 2 or more types.

It does not specifically limit as monomer S1, Any monomer containing a polyorganosiloxane skeleton can be used. As monomer S1, one of a structure having a polymerizable reactive group at one end can be preferably used. Among them, monomer S1 having a structure having a polymerizable reactive group at one end and not having a functional group causing a crosslinking reaction with the acrylic polymer (A) at the other end can be preferably employed. Examples of commercially available products include single-end reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd. (for example, product numbers such as X-22-174ASX, X-22-2426, X-22-2475, and KF-2012). have. Monomer S1 can be used individually by 1 type or in combination of 2 or more types.

The functional group equivalent of monomer S1 may be about 100 g/mol to 30000 g/mol, for example. In some preferred 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, 20000 g/mol or less, less than 10000 g/mol, 7000 g/mol or less, or 5500 g/mol or less. When the functional group equivalent of monomer S1 is within the above range, a favorable leveling effect is likely to be exhibited.

In the case of using two or more types of monomers having different functional group equivalents as the monomer S1, the functional group equivalent of the monomer S1 can be the sum of the products of the functional group equivalents of each type of monomer and the weight fraction of the monomer.

Here, "functional group equivalent" means the weight of the main skeleton (for example, polydimethylsiloxane) bonded to each functional group. Regarding the notational unit g/mol, it is converted to 1 mol of the functional group. The functional group equivalent of monomer S1 can be calculated, for example, from the spectral intensity of ¹ H-NMR (proton NMR) based on nuclear magnetic resonance (NMR). Calculation of the functional group equivalent (g/mol) of monomer S1 based on the spectrum intensity of ¹ H-NMR is based on a general structural analysis method related to ¹ H-NMR spectrum analysis, and, if necessary, is described in Japanese Patent No. 5951153. can be done with reference to In the functional group equivalent of monomer S1, the functional group means a polymerizable functional group (for example, an ethylenically unsaturated group such as a (meth)acryloyl group, a vinyl group, or an allyl group).

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

The monomer raw material B contains, in addition to monomer S1, an acrylic monomer copolymerizable with monomer S1. Thereby, the compatibility of the polymer (B) in the pressure-sensitive adhesive layer can be improved. Examples of the acrylic monomer that can be used for the monomer raw material B include acrylic acid alkyl esters. "Alkyl" here refers to a chain (including straight-chain and branched-chain) alkyl (group), and does not contain an alicyclic hydrocarbon group described later. In some embodiments, the monomer raw material B is (meth)acrylic acid C _4-12 alkyl ester (preferably (meth)acrylic acid C _4-10 alkyl ester, for example (meth)acrylic acid C _6-10 alkyl ester ) may contain at least one of them. In some other aspects, the monomer raw material B is methacrylic acid C _1-18 alkyl ester (preferably methacrylic acid C _1-14 alkyl ester, for example methacrylic acid C _1-10 alkyl ester) It may contain at least 1 type. The monomer raw material B is an acrylic monomer, for example, one or two or more selected from methyl methacrylate (MMA), n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (2EHMA). can include

Other examples of the acrylic monomer include (meth)acrylic acid esters having an alicyclic hydrocarbon group. For example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 1-adamantyl (meth) acrylate, etc. can be used It is not necessary to use a (meth)acrylic acid ester having an alicyclic hydrocarbon group.

The content of the alkyl (meth)acrylic acid ester and the (meth)acrylic acid ester having an 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 20% by weight or more and 95% by weight. It may be below, 30 weight% or more and 90 weight% or less may be sufficient, 40 weight% or more and 90 weight% or less may be sufficient, and 50 weight% or more and 85 weight% or less may be sufficient.

As other examples of monomers that can be included in the monomer raw material B together with monomer S1, as monomers that can be used for acrylic polymers, the carboxy group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, and cyano group-containing monomers exemplified above Monomer, isocyanate group-containing monomer, amide group-containing monomer, monomer having a nitrogen atom-containing ring, (meth)acrylic acid aminoalkyls, vinyl esters, vinyl ethers, olefins, (meth)acrylic acid esters having an aromatic hydrocarbon group, halogen An atom-containing (meth)acrylate etc. are mentioned.

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

Polymer (B) can be produced, for example, by polymerizing the above-mentioned monomers by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or photopolymerization.

In order to adjust the molecular weight of polymer (B), a chain transfer agent can be used as needed. Examples of the chain transfer agent to be used include compounds having a mercapto group such as t-dodecylmercaptan, mercaptoethanol, and α-thioglycerol; thioglycolic acid esters such as thioglycolic acid and methyl thioglycolate; α-methylstyrene dimer; etc. can be mentioned. The amount of the chain transfer agent used is not particularly limited and can be appropriately set so as to obtain a polymer (B) having a desired molecular weight. In some embodiments, the amount of chain transfer agent used per 100 parts by weight of monomers may be, for example, 0.1 to 5 parts by weight, 0.2 to 3 parts by weight, or 0.5 to 2 parts by weight.

The amount of polymer (B) used per 100 parts by weight of the acrylic polymer (A) can be, for example, 0.001 part by weight or more. can be done with In addition, the amount of the polymer (B) used may be, for example, 3 parts by weight or less, and from the viewpoint of reducing the effect on the refractive index, it is appropriate to be 1 part by weight or less, 0.5 parts by weight or less, or 0.1 parts by weight. may be below.

(inorganic particles)

The technology disclosed herein may be preferably implemented in an aspect that does not substantially use inorganic particles for increasing the refractive index, but to the extent that the application effect of the technology disclosed herein is not significantly impaired, an additive (H _RO ) In addition, it is free to use inorganic particles having a high refractive index as an aid. Examples of the inorganic particles include titania (titanium oxide, TiO ₂ ), zirconia (zirconium oxide, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide (Nb ₂ O ₅ , etc.), and the like. and inorganic particles composed of inorganic oxides (specifically, metal oxides). The average particle diameter of the inorganic particles (referring to a 50% volume average particle diameter based on the laser scattering/diffraction method) can be selected from, for example, a range of about 10 nm to 100 nm. The amount of the inorganic particles used is preferably less than 5 parts by weight, more preferably less than 1 part by weight, based on 100 parts by weight of the acrylic polymer (A). In the aspect using the additive (H _RO ), the amount of the inorganic particles used is preferably 2 times or less, and is 1 time or less or 0.5 times or less, based on weight, of the amount of the additive (H _RO ) used. more preferable

(other additives)

The pressure-sensitive adhesive composition disclosed herein may be used in the pressure-sensitive adhesive composition, such as a plasticizer, a softener, a colorant, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, and an antiseptic, to the extent that the effects of the present invention are not significantly impaired. Known additives that can be used may be included as needed. Regarding these various additives, conventionally known ones can be used by conventional methods, and since they do not particularly characterize the present invention, detailed descriptions are omitted.

<Adhesive>

The pressure-sensitive adhesive disclosed herein can be formed using, for example, any of the pressure-sensitive adhesive compositions described above. Such a pressure-sensitive adhesive may be a pressure-sensitive adhesive obtained by curing a pressure-sensitive adhesive composition in a form such as a solvent type, active energy ray curable type, water dispersion type, hot melt type, etc., by drying, crosslinking, polymerization, cooling, or the like, that is, a cured product of the above pressure-sensitive adhesive composition. . As for the curing means (for example, drying, crosslinking, polymerization, cooling, etc.) of the pressure-sensitive adhesive composition, only one type may be applied, or two or more types may be applied simultaneously or in multiple steps. In the solvent-type pressure-sensitive adhesive composition, the pressure-sensitive adhesive can be formed by drying (preferably, further crosslinking) the composition typically. In an active energy ray-curable pressure-sensitive adhesive composition, a pressure-sensitive adhesive is typically formed by irradiating an active energy ray to advance a polymerization reaction and/or a crosslinking reaction. What is necessary is just to irradiate an active energy ray after drying, when it is necessary to dry with an active energy ray-curable adhesive composition.

(refractive index)

The pressure-sensitive adhesive disclosed herein may have a refractive index higher than or equal to a predetermined level. According to the technology disclosed herein, a pressure-sensitive adhesive having a refractive index of, for example, 1.560 or more (preferably 1.570 or more, more preferably more than 1.570), a pressure-sensitive adhesive composition capable of forming the pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive may be provided.

In addition, in this specification, the refractive index of an adhesive means the refractive index of the surface (adhesive surface) of this adhesive. The refractive index of the pressure-sensitive adhesive can be measured using a commercially available refractive index measuring device (Abe refractometer) under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, for example, a type "DR-M4" manufactured by ATAGO or an equivalent thereof is used. As a measurement sample, the adhesive layer which consists of the adhesive of evaluation object can be used. The refractive index of the pressure-sensitive adhesive can be specifically measured by the method described in Examples described later. The refractive index of the pressure-sensitive adhesive can be adjusted by the composition of the pressure-sensitive adhesive, for example.

In some embodiments, the refractive index of the pressure-sensitive adhesive is preferably 1.575 or more (eg greater than 1.575), more preferably 1.580 or more, still more preferably 1.585 or more, particularly preferably 1.590 or more (eg 1.595 or higher). According to the pressure-sensitive adhesive having such a refractive index, the behavior of light can be effectively controlled by using the difference in refractive index between the pressure-sensitive adhesive and the adherend. In some embodiments of the pressure-sensitive adhesive disclosed herein, the pressure-sensitive adhesive may have a refractive index of, for example, 1.600 or greater or greater than 1.600, 1.605 or greater or greater than 1.605, or 1.610 or greater or greater than 1.610. The preferable upper limit of the refractive index of the pressure-sensitive adhesive is not limited to a specific range since it may vary depending on the refractive index of the adherend and the like. In some aspects, the refractive index of the pressure-sensitive adhesive may be, for example, 1.700 or less, 1.670 or less, or 1.650 or less, in consideration of the balance with adhesive properties and transparency.

<Adhesive Sheet>

According to this specification, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer may be a pressure-sensitive adhesive formed from any of the pressure-sensitive adhesive compositions disclosed herein (eg, a cured product of the pressure-sensitive adhesive composition).

The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet having a base material having a pressure-sensitive adhesive layer on one side or both sides of a non-peelable base material (supporting base material), or an inorganic pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is held by a release liner. (That is, an adhesive sheet having no non-peelable base material. Typically, an adhesive sheet composed of an adhesive layer) may be used. The concept of the pressure-sensitive adhesive sheet herein may include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. The PSA sheet disclosed herein may be in the form of a roll or sheet. Alternatively, it may be a pressure-sensitive adhesive sheet processed into more diverse shapes.

1 shows a configuration example of the pressure-sensitive adhesive sheet disclosed herein. This PSA sheet 1 is laminated on the PSA layer 10, the first surface 10A of which serves as an adhesion surface (adhesive surface) to the adherend, and the second surface 10B of the PSA layer 10. It is constituted as a single-sided adhesive PSA sheet (single-sided PSA sheet) including a supporting substrate 20. The second surface 10B of the pressure-sensitive adhesive layer 10 is bonded to the first surface (non-peelable surface) 20A of the supporting substrate 20 . As the support substrate 20, a plastic film such as a polyester film may be used, for example. The supporting substrate 20 may be, for example, an optical film such as a polarizing plate. In the PSA sheet 1 before use (before sticking to an adherend), as shown in, for example, FIG. It may be in the form of an adhesive sheet 50 having a release liner, protected by the release liner 30 thereon. Alternatively, the second surface 20B of the supporting substrate 20 (a surface opposite to the first surface 20A, also referred to as a back surface) is a release surface, and an adhesive surface ( 10A) may be wound or laminated so that the adhesive surface 10A is protected. The pressure-sensitive adhesive layer 10 may have a single-layer structure, or may have a laminated structure in which two or more sub-pressure-sensitive adhesive layers having different compositions are stacked in direct contact (that is, not separated by a layer made of a non-adhesive material).

The release liner is not particularly limited. For example, a release liner in which the surface of a liner substrate such as a resin film or paper is subjected to a release treatment, a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene) etc.) can be used. For the peeling treatment, for example, a silicone-based, long-chain alkyl-based, or other peeling agent may be used. In some embodiments, a resin film subjected to release treatment can be preferably employed as a release liner.

The PSA sheet disclosed herein may be an inorganic double-sided PSA sheet composed of a PSA layer. As shown in FIG. 2 , the inorganic double-sided pressure-sensitive adhesive sheet 2 has the first surface (first adhesive surface) 10A and the second surface (second adhesive surface) of the pressure-sensitive adhesive layer 10 before use. 10B may be of a form protected by release liners 31 and 32 in which at least the pressure-sensitive adhesive layer side is a release surface (release surface). Alternatively, the back surface of the release liner 31 (surface on the opposite side to the adhesive side) is a release surface, and the adhesive surface 10A is formed by winding or stacking so that the adhesive surface 10B is in contact with the back surface of the release liner 31. 10B) may be in a protected form. Such an inorganic double-sided pressure-sensitive adhesive sheet may be used by bonding a substrate (which may be an optical member such as an optical film) to at least one of the first and second adhesive surfaces, for example. The pressure-sensitive adhesive layer constituting the inorganic double-sided pressure-sensitive adhesive sheet may have a single-layer structure, similarly to the pressure-sensitive adhesive layer 10 in the pressure-sensitive adhesive sheet 1 shown in FIG. may be a laminated structure.

The pressure-sensitive adhesive sheet disclosed herein may be a component of an optical member comprising a pressure-sensitive adhesive sheet in which an optical member is bonded to one surface of a pressure-sensitive adhesive layer. For example, as shown in FIG. 3 , the PSA sheet 1 shown in FIG. 1 is provided with an optical member 70 bonded to one surface 10A of the PSA layer 10. It may be a component of the optical member 100. The optical member may be, for example, a glass plate, a resin film, or a metal plate. In addition, in the PSA sheet 1 shown in FIG. 1 , when the supporting substrate 20 is an optical member such as an optical film, the PSA sheet 1 has a second surface 10B of the PSA layer 10 It can be understood as an optical member having an adhesive sheet to which an optical member is bonded.

Further, although not particularly shown, the PSA sheet disclosed herein includes a support substrate having a non-releasable first surface and a second surface, a first pressure-sensitive adhesive layer is fixedly laminated on the first surface, and the first surface is fixedly laminated. It may be in the form of a double-sided adhesive pressure-sensitive adhesive sheet having a base material in which the second pressure-sensitive adhesive layer is fixedly laminated on two surfaces (double-sided pressure-sensitive adhesive sheet having a base material). As an example of the configuration of a double-sided pressure-sensitive adhesive sheet having such a base material, in the single-sided pressure-sensitive adhesive sheet 1 shown in FIG. A second pressure-sensitive adhesive layer is provided on (20B), the second surface of the second pressure-sensitive adhesive layer is bonded to the second surface 20B of the supporting base material 20, and the first surface (first surface of the second pressure-sensitive adhesive layer) The surface on the opposite side to 2 surface) is a form in which it becomes the 2nd adhesive surface of the double-sided adhesive sheet provided with a base material is mentioned. The composition of the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer may be the same as or different from the composition of the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer. The double-sided pressure-sensitive adhesive sheet provided with the substrate before use may have a form in which the first adhesive surface and the second adhesive surface are protected by a release liner, similarly to the inorganic double-sided pressure-sensitive adhesive sheet described above.

The pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet in which both sides are adhesive surfaces (including both an inorganic double-sided pressure-sensitive adhesive sheet and a double-sided pressure-sensitive adhesive sheet having a base material. The same applies hereinafter unless otherwise specified). In this case, the refractive indices of the first adhesive surface and the second adhesive surface are not particularly limited. In some aspects, it is preferable that at least the first adhesive surface satisfy any of the refractive indices described above, and a double-sided pressure-sensitive adhesive sheet in which both the first adhesive surface and the second adhesive surface satisfy any of the refractive indices described above may be used.

In some aspects, the refractive index n ₂ of the second adhesive surface may be substantially 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, that is, |n ₁ -n ₂ |, may be, for example, less than 0.05, less than 0.03, or less than 0.01. The lower limit of |n ₁ -n ₂ | may be 0.00 or larger than 0.00. The relative relationship between the refractive indices of both adhesive surfaces may be n ₁ > n ₂ , n ₁ < n ₂ , or n ₁ =n ₂ .

In some other aspects, the difference between the refractive index n ₁ of the first adhesive surface of the adhesive sheet and the refractive index n ₂ of the second adhesive surface, that is, n ₁ -n ₂ , may be greater than 0.00 or greater than 0.01, for example. It 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 may be reversed. The double-sided pressure-sensitive adhesive sheet having different refractive indices between the first adhesive surface and the second adhesive surface is, for example, a double-sided pressure-sensitive adhesive sheet having a base material by laminating first and second pressure-sensitive adhesive layers having different refractive indices on a non-peelable support base material. However, it can be realized by setting the pressure-sensitive adhesive layer constituting the non-material double-sided pressure-sensitive adhesive sheet to a laminated structure of two or more sub-pressure-sensitive adhesive layers having mutually different refractive indices.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein may be formed by applying (for example, applying) a pressure-sensitive adhesive composition to an appropriate surface and then curing the composition. Application of the pressure-sensitive adhesive composition can be performed using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater, for example.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive layer having post-curing properties or may be a pressure-sensitive adhesive layer having no post-curing properties. Here, the pressure-sensitive adhesive layer having post-curing properties refers to a pressure-sensitive adhesive layer that can be further cured by irradiation with heat or active energy rays (for example, ultraviolet rays). As examples of the pressure-sensitive adhesive layer having post-curing properties, a pressure-sensitive adhesive layer having an unreacted ethylenically unsaturated group in the side chain of the base polymer (eg, acrylic polymer (A)) or a pressure-sensitive adhesive layer containing an unreacted polyfunctional monomer can be heard In some aspects, it is preferable that the pressure-sensitive adhesive layer does not have post-curing properties. A pressure-sensitive adhesive layer having no post-curing property does not cause dimensional change accompanying a post-curing reaction (that is, has good dimensional stability), so it is easy to suppress warpage of the pressure-sensitive adhesive sheet or the adherend to which the pressure-sensitive adhesive sheet is attached. The fact that dimensional change (for example, curing shrinkage) due to post-curing does not occur can be advantageous also from the viewpoint of suppressing optical distortion of the pressure-sensitive adhesive layer.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 3 μm or more. In some aspects, the thickness of the pressure-sensitive 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 micrometers or more may be sufficient. In some embodiments, the pressure-sensitive adhesive layer may have a thickness of, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. A thickness of the pressure-sensitive adhesive layer that is not too large may be advantageous from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet or the like. The technology disclosed herein can be preferably implemented in an aspect in which the thickness of the pressure-sensitive adhesive layer is in the range of, for example, 3 μm to 200 μm (more preferably 5 μm to 100 μm). In addition, in the case of a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on the first and second surfaces of the substrate, the thickness of the pressure-sensitive adhesive layer described above may be applied to at least the thickness of the first pressure-sensitive adhesive layer. The thickness of the second pressure-sensitive adhesive layer can also be selected from the same range. In addition, in the case of an inorganic double-sided pressure-sensitive adhesive sheet composed of an adhesive layer, the thickness of the pressure-sensitive adhesive layer becomes the thickness of the pressure-sensitive adhesive sheet.

(total light transmittance)

In the technique disclosed herein, the total light transmittance of the pressure-sensitive adhesive layer is suitably greater than 50%, for example, and is preferably 70% or more. In some preferred embodiments, the adherend has a total light transmittance of 85% or more, preferably 86% or more, more preferably 88% or more, and more preferably 90% or more (for example, more than 90.0%). , 90.5% or more may be sufficient. Such a pressure-sensitive adhesive sheet having a high-transparency pressure-sensitive adhesive layer can be used for applications requiring high light transmittance (for example, optical applications), with or without a base material, and for adherends through the pressure-sensitive adhesive sheet. It can be preferably applied to applications requiring visible performance. In some aspects, the total light transmittance of the pressure-sensitive adhesive layer may be 93% or more, or 95% or more. The upper limit of the total light transmittance is, theoretically, a value obtained by subtracting light loss (Fresnel loss) due to reflection occurring at the air interface from 100%, and may be approximately 98% or less or approximately 96% or less in practical use. , may be approximately 95% or less. In some aspects, the total light transmittance of the pressure-sensitive adhesive layer may be approximately 94% or less, approximately 93% or less, or approximately 92% or less, in consideration of the refractive index and adhesive properties. The total light transmittance is measured using a commercially available transmittance meter based on JIS K 7136:2000. As the transmittance meter, a trade name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Genkyujo Co., Ltd. or an equivalent thereof is used. More specifically, for example, the total light transmittance of the pressure-sensitive adhesive layer can be measured according to Examples described later. The total light transmittance of the pressure-sensitive adhesive layer can be adjusted by selecting the composition, thickness, or the like of the pressure-sensitive adhesive layer, for example.

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet comprising a substrate in which a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer are fixedly laminated on a support substrate, at least the first pressure-sensitive adhesive layer has a total light transmittance of any of the above. It is desirable to meet In a usage mode in which light escapes in the thickness direction of the pressure-sensitive adhesive sheet, it is preferable that both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer satisfy any of the above-described total light transmittances. The relative relationship between the total light transmittance of both pressure-sensitive adhesive layers may be 1st pressure-sensitive adhesive layer > 2nd pressure-sensitive adhesive layer, 1st pressure-sensitive adhesive layer < 2nd pressure-sensitive adhesive layer, or 1st pressure-sensitive adhesive layer = 2nd pressure-sensitive adhesive layer.

(Haze value)

In some embodiments, the haze value of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less (eg 2.0% or less), and more preferably 1.0% or less. and more preferably 0.9% or less. Such a pressure-sensitive adhesive sheet having a high-transparency pressure-sensitive adhesive layer can be used for applications requiring high light transmittance (for example, optical applications), with or without a base material, and for adherends through the pressure-sensitive adhesive sheet. It can be preferably applied to applications requiring visible performance. In some aspects, the haze value of the pressure-sensitive 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 pressure-sensitive adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the lower the haze value, the better. On the other hand, in some aspects, considering the refractive index and adhesion characteristics, the haze value may be, for example, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more. may be continued These haze values for the pressure-sensitive adhesive layer are preferably applied to the haze value of the pressure-sensitive adhesive sheet in the case where the technology disclosed herein is implemented in the form of an inorganic pressure-sensitive adhesive sheet (typically, a pressure-sensitive adhesive sheet made of a pressure-sensitive adhesive layer). can

Here, "haze value" refers to the ratio of diffused transmitted light to total transmitted light when visible light is irradiated to a measurement object. Also called cloudiness. A haze value can be represented by the following formula.

Th(%)=Td/Tt×100

In the above formula, Th is haze value (%), Td is scattered light transmittance, and Tt is total light transmittance. The haze value can be measured according to the method described in Examples described later. The haze value of the pressure-sensitive adhesive layer can be adjusted by selection of the composition, thickness, or the like of the pressure-sensitive adhesive layer, for example.

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet having a base material in which the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are fixedly laminated on a support base material, at least the first pressure-sensitive adhesive layer has a haze value of any of the above. It just needs to be satisfied, and the haze value of the second pressure-sensitive adhesive layer is not particularly limited. In a usage aspect in which light escapes in the thickness direction of the pressure-sensitive adhesive sheet, it is preferable that the haze value of the second pressure-sensitive adhesive layer satisfies any one of the above-described haze values of the first pressure-sensitive adhesive layer. The relative relationship between the haze values of both pressure-sensitive adhesive layers may be 1st pressure-sensitive adhesive layer > 2nd pressure-sensitive adhesive layer, 1st pressure-sensitive adhesive layer < 2nd pressure-sensitive adhesive layer, or 1st pressure-sensitive adhesive layer = 2nd pressure-sensitive adhesive layer.

(Surface smoothness of adhesive surface)

In some aspects of the PSA sheet disclosed herein, the PSA sheet preferably has high surface smoothness on the PSA surface.

For example, it is preferable that the arithmetic average roughness Ra of the adhesive surface is limited to a predetermined value or less. A structure provided with an adhesive surface designed so that the arithmetic mean roughness Ra is low is preferable from the viewpoint of optical homogeneity. By limiting the arithmetic average illuminance Ra, for example, in a usage mode in which light is extracted through the adhesive surface (a pressure-sensitive adhesive sheet disposed on the viewpoint side of a self-light emitting device in a light emitting device, etc.), it is due to the surface state of the pressure-sensitive adhesive layer It is possible to exert an effect of suppressing the occurrence of luminance non-uniformity. A low arithmetic average roughness Ra of the adhesive surface is advantageous for suppression of optical distortion, and suppression of optical distortion also contributes to improvement in optical homogeneity. When the PSA sheet disclosed herein is in the form of a double-sided PSA sheet having a first adhesive surface and a second adhesive surface, it is preferable that the arithmetic average roughness Ra of at least the first adhesive surface is limited to a predetermined value or less, and both sides It is more preferable that all of the arithmetic average roughness Ra of the adhesive surface be limited to a predetermined value or less. When each adhesive face of the double-sided pressure-sensitive adhesive sheet has high surface smoothness, adhesion excellent in optical homogeneity can be preferably realized.

In some embodiments, the arithmetic average roughness Ra of the adhesive surface is preferably approximately 70 nm or less, more preferably approximately 65 nm or less, still more preferably approximately 55 nm or less, and may be less than 50 nm. , may be less than 45 nm or less than 40 nm. From the viewpoint of production efficiency and the like, in some embodiments, the arithmetic average roughness Ra of the adhesive surface of the pressure-sensitive adhesive sheet may be, for example, approximately 10 nm or more, approximately 20 nm or more, or approximately 30 nm or more (for example, For example, it may be about 40 nm or more). In the aspect in which the PSA sheet has the first adhesive surface and the second adhesive surface, the arithmetic average roughness Ra of the first adhesive surface and the arithmetic average roughness Ra of the second adhesive surface may be the same or different.

Further, for example, it is preferable that the maximum height Rz of the adhesive face is limited to a predetermined value or less. A configuration having an adhesive surface designed to have a low maximum height Rz is preferable from the viewpoint of optical homogeneity. By restricting the maximum height Rz, for example, in a usage mode in which light is taken out through the adhesive surface as described above, an effect of suppressing occurrence of luminance nonuniformity due to the surface state of the adhesive layer can be exhibited. The low maximum height Rz of the adhesive surface is also advantageous for suppression of optical distortion. When the PSA sheet disclosed herein is in the form of a double-sided PSA 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 is limited to a predetermined value or less, and both sides are adhered to each other. It is more preferable that all of the maximum heights Rz of the surfaces are limited to a predetermined value or less. When each adhesive face of the double-sided pressure-sensitive adhesive sheet has high surface smoothness, adhesion excellent in optical homogeneity can be preferably realized.

In some embodiments, the maximum height Rz of the adhesive surface is preferably about 600 nm or less, more preferably about 500 nm or less, even more preferably about 450 nm or less, and particularly preferably about 400 nm or less. It may be less than 350 nm, less than 300 nm, or less than 250 nm. From the viewpoint of production efficiency and the like, in some embodiments, the maximum height Rz of the adhesive face of the pressure-sensitive adhesive sheet may be, for example, approximately 10 nm or more, approximately 50 nm or more, approximately 100 nm or more, or approximately 200 nm or more may be sufficient. In the aspect in which the adhesive sheet has the first adhesive face and the second adhesive face, the maximum height Rz of the first adhesive face and the maximum height Rz of the second adhesive face may be the same or different.

The arithmetic average roughness Ra and the maximum height Rz of the adhesive surface are measured using a non-contact type surface roughness measuring device. As a non-contact type surface roughness measuring device, a surface roughness measuring device of an optical interference method is used, and for example, a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO) or its equivalent can be used. Specifically, for example, the arithmetic mean roughness Ra and the maximum height Rz can be measured by the following measuring method or by setting measurement operation and measurement conditions so that equivalent or corresponding results are obtained with the measuring method. can

That is, in an environment of 23°C and 50% RH, the surface shape of the measurement sample is measured under the following conditions using a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO). Arithmetic surface roughness Ra is calculated from the measured data according to JIS B 0601-2001. The maximum height Rz is obtained as the sum of the height Rp of the highest peak upward from the average line of the roughness curve and the depth Rv of the deepest valley downward from the average line with respect to the data (roughness curve) obtained by the measurement. Ra and Rz were measured 5 times (i.e. N = 5), and their average values were used.

The sample for measurement can be prepared, for example, by cutting the pressure-sensitive adhesive layer to be measured or the pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer to a size of about 150 mm in length and 50 mm in width. When the adhesive face is protected by a peeling liner, the peeling liner is gently peeled off (for example, under conditions of a pulling speed of 300 mm/min and a peeling angle of 180°) to expose the adhesive face. It is preferable to measure after leaving still for about 30 minutes after exposing the adhesive surface.

[Measuring conditions]

Measuring area: 5.62 mm × 4.22 mm

(Objective lens: 2.5x, inner lens: 0.5x)

Interpretation mode:

Remove: Cylinder

Data Fill: ON (Max: 25)

Remove Spikes: ON (xRMS: 1)

Filter: OFF

The arithmetic average roughness Ra and maximum height Rz of the adhesive surface are determined by the composition and properties (viscosity, leveling properties, etc.) of the adhesive composition used for forming the adhesive layer, the properties of the surface (release surface) of the release liner that protects the adhesive surface, etc. can be regulated by

(Storage modulus G')

In the PSA sheet disclosed herein, the storage elastic modulus G' (hereinafter also referred to as "storage elastic modulus G'(25)") at 25°C of the PSA constituting the PSA layer is appropriate depending on the purpose of use or the mode of use. It is set to be, and is not limited to a specific range. The storage elastic modulus G'(25) of the pressure-sensitive adhesive may be, for example, approximately 700 kPa or less. In some embodiments, from the viewpoint of ease of sticking to an adherend, etc., the storage elastic modulus G '(25) of the pressure-sensitive adhesive is preferably approximately 600 kPa or less, preferably 500 kPa or less, and 400 kPa or less (eg For example, 350 kPa or less) is more preferable. In some aspects, from the viewpoint of enhancing the flexibility of the pressure-sensitive adhesive in the room temperature region (eg, 25 ° C.) and making it easier to adhere to the adherend, the storage elastic modulus G' (25) of the pressure-sensitive adhesive is approximately 330 kPa or less It is advantageous, and it is preferable that it is 300 kPa or less. In some aspects in which adhesion and flexibility in the room temperature region are more important, the storage modulus G '(25) of the pressure-sensitive adhesive may be, for example, less than 270 kPa or less than 250 kPa, and less than 200 kPa is advantageous, It is preferably less than 180 kPa, and more preferably less than 160 kPa (for example, less than 140 kPa). In some aspects, the storage elastic modulus G' (25) of the pressure-sensitive adhesive may be less than 100 kPa or less than 90 kPa. The lower limit of the storage elastic modulus G' (25) of the pressure-sensitive adhesive is not particularly limited, but may be, for example, 30 kPa or more, 50 kPa or more, or 70 kPa or more from the viewpoint of processability or handling. In some 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 may be continued

In the PSA sheet disclosed herein, the storage elastic modulus G' at 50°C (hereinafter also referred to as "storage modulus G' (50)") of the PSA constituting the PSA layer is not particularly limited. For example, it may be less than 100 kPa. In some embodiments, the storage modulus G' (50) is suitably less than 60 kPa, preferably less than 40 kPa, and more preferably less than 38 kPa (for example, less than 36 kPa). In this way, the adhesive having a limited storage elastic modulus G' (50) can be easily improved in adhesion to an adherend by appropriately heating as necessary, thereby improving the adhesiveness to an adherend. The lower limit of the storage elastic modulus G' (50) of the pressure-sensitive adhesive is not particularly limited. In some aspects, from the viewpoint of heat resistance characteristics of the pressure-sensitive adhesive, the storage 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 some embodiments of the pressure-sensitive adhesive disclosed herein, the pressure-sensitive adhesive is subject to the following conditions:

(a) The storage elastic modulus G'(25) at 25 degreeC is 350 kPa or less (preferably less than 200 kPa, for example, 180 kPa or less); and

(b) a storage elastic modulus G'(50) at 50°C of less than 60 kPa (preferably less than 50 kPa, more preferably less than 40 kPa, for example less than 38 kPa);

It is desirable to satisfy at least one of them. A pressure-sensitive adhesive that satisfies at least the above condition (a) is preferable from the viewpoint of adhesion to an adherend in a room temperature region (for example, 25°C). A pressure-sensitive adhesive that satisfies at least the above condition (b) is preferable because it can easily improve adhesion to an adherend (adhesiveness) by heating at a temperature slightly higher than room temperature. The adhesive that does not satisfy the above condition (a) and satisfies the above (b) has good reworkability (re-adhesion property) in the initial stage of sticking at room temperature, and is suitable for heating at a temperature slightly higher than room temperature. It can be used as a heat-activated type of pressure-sensitive adhesive that can effectively increase peeling strength from an adherend. The thermal activation may be performed by heating the pressure-sensitive adhesive to a temperature slightly higher than room temperature at the time of application to an adherend. The temperature slightly higher than room temperature is, for example, about 60°C or less, and preferably about 55°C or less (eg, about 50°C or less).

In some aspects of the PSA sheet disclosed herein, the ratio of the storage modulus G'(50)[kPa] to the storage modulus G'(25)[kPa] of the PSA constituting the PSA layer, that is, the storage modulus ratio G'(50)/G'(25) may be, for example, 70% or less, 40% or less, 30% or less, or 20% or less. A pressure-sensitive adhesive having a small G'(50)/G'(25) is suitable for use as the heat-activated type pressure-sensitive adhesive. The lower limit of G'(50)/G'(25) is not particularly limited. G'(50)/G'(25) is, for example, 5% or more, and is preferably 10% or more, may be 12% or more, or may be 15% or more from the viewpoint of the heat resistance property of the pressure-sensitive adhesive.

The storage modulus G'(25) and G'(50) can be determined by dynamic viscoelasticity measurement, and G'(50)/G'(25) can be calculated from the result. The dynamic viscoelasticity measurement can be performed by a conventional method using a commercially available dynamic viscoelasticity measuring device, for example, using "Advanced Rheometric Expansion System (ARES)" manufactured by TA Instruments or an equivalent thereof, under the following measurement conditions. can be done in As a sample for measurement, what was prepared to about 1.5 mm in thickness by laminating|stacking the adhesive layer of evaluation target as needed is used.

[Measuring conditions]

Deformation Mode: Torsion

Measurement frequency: 1Hz

Heating rate: 5°C/min

Shape: Parallel plate 7.9mmφ

The storage modulus G'(25), G'(50) and the storage modulus ratio of the pressure-sensitive adhesive layer are determined by the selection of the composition of the monomer component constituting the acrylic polymer (A) (for example, the type and content of the monomer (m1) selection), whether or not to use a crosslinking agent, selection of the type and amount of use, selection of the use of the aforementioned additive (H _RO ) or plasticizing material, type and amount of use, and the like. For example, as the monomer (m1), in addition to the first monomer, which is the main component of the monomer (m1), a second monomer having a chemical structure different from that of the first monomer is used in combination with the first monomer in a relatively small amount. , In addition to the case of using the first monomer alone as the monomer (m1), G'(50) can be made small, and G'(50)/G'(25) can be reduced.

The pressure-sensitive adhesive sheet disclosed herein includes a double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive surface and a second pressure-sensitive adhesive surface (eg, a double-sided pressure-sensitive adhesive sheet having a base material having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, the first pressure-sensitive adhesive surface When the constituting sub-adhesive layer and the sub-adhesive layer constituting the second adhesive surface are laminated without passing through a non-adhesive substrate, such as an inorganic double-sided adhesive sheet, etc. (the same applies to other similar substrates), the storage described above The elastic modulus G'(25), G'(50), and the storage elastic modulus ratio are applied to at least the pressure-sensitive adhesive layer constituting the first adhesive surface, and preferably the pressure-sensitive adhesive layer constituting the first adhesive surface and the second adhesive surface. It is applied to both sides of the constituting pressure-sensitive adhesive layer. The storage elastic modulus G' of the pressure-sensitive adhesive layer constituting the first adhesive surface and the storage elastic modulus G' of the pressure-sensitive adhesive layer constituting the second adhesive surface may be about the same or different.

In some aspects of the technology disclosed herein, the peak temperature of tan δ of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably approximately -50°C or higher, and is preferably approximately 50°C or lower. Here, the tan δ (loss tangent) of the pressure-sensitive adhesive refers to the ratio of the loss modulus G" to the storage modulus G' of the pressure-sensitive adhesive. That is, tan δ = G"/G'. The tanδ of the pressure-sensitive adhesive was measured by inserting a disk-shaped pressure-sensitive adhesive sample having a thickness of about 2 mm and a diameter of 7.9 mm between parallel plates, and applying shear strain at a frequency of 1 Hz using a viscoelasticity tester in a measurement temperature range of -60°C to 60°C. , under the conditions of a temperature increase rate of 5 ° C./min, the temperature dispersion test of the pressure-sensitive adhesive was conducted in shear mode, and from the storage modulus G' (Pa) and loss modulus G" (Pa) at that time, the following formula: tanδ = G" / It is obtained by G';. From the transition of tan δ in the above temperature range, the peak temperature of tan δ of the pressure-sensitive adhesive (hereinafter sometimes referred to as Tpeak) is obtained. As the viscoelasticity tester, ARES manufactured by TA Instruments or an equivalent product thereof can be used.

In some embodiments, the Tpeak of the pressure-sensitive adhesive is preferably 45 ° C or less or 35 ° C or less, preferably 30 ° C or less (eg 25 ° C or less), 20 ° C. or less, 15 ° C. or less . A pressure-sensitive adhesive having a lower Tpeak tends to be easier to obtain good initial adhesion and adhesion in the room temperature region. On the other hand, a pressure-sensitive adhesive having a Tpeak that is not too low is preferable from the viewpoint of imparting appropriate cohesiveness to the pressure-sensitive adhesive, and tends to be compatible with high refractive index. From this point of view, in some embodiments, the Tpeak of the pressure-sensitive 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. It may be, it may be 15 ° C. or higher, and further 25 ° C. or higher may be sufficient. A pressure-sensitive adhesive having a relatively high Tpeak can be preferably used in an aspect in which one or both of the pressure-sensitive adhesive and the adherend are heated to a temperature slightly higher than room temperature, as needed, when the pressure-sensitive adhesive has a relatively high Tpeak. The Tpeak of the pressure-sensitive adhesive is determined by the selection of the composition of the pressure-sensitive adhesive (for example, the composition of the monomer component constituting the acrylic polymer (A), whether or not an additive ( _HRO ) or plasticizing material is used, the type, and the amount used), etc. can be adjusted

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet having a first adhesive surface and a second adhesive surface, the Tpeak of the above-described pressure-sensitive adhesive is preferably applied to at least the pressure-sensitive adhesive layer constituting the first adhesive surface, More preferably, it is applied to both the pressure-sensitive adhesive layer constituting the first adhesive surface and the pressure-sensitive adhesive layer constituting the second adhesive surface. The Tpeak of the pressure-sensitive adhesive layer constituting the first adhesive surface and the Tpeak of the pressure-sensitive adhesive layer constituting the second adhesive surface may be the same or different.

(absorption rate)

In some aspects of the PSA sheet disclosed herein, it is preferable that the PSA layer constituting the PSA sheet has a water absorption rate limited to a predetermined value or less. By limiting the water absorption rate of the pressure-sensitive adhesive layer, dimensional change of the pressure-sensitive adhesive layer due to fluctuations in the amount of moisture in the pressure-sensitive adhesive layer (eg, absorption and release of moisture such as moisture in the environment) tends to be suppressed. As a result, warpage of the PSA sheet or the adherend to which the PSA sheet is attached due to mismatch in dimensional change between the PSA layer and the layer adjacent to the PSA layer (which may be a support substrate, a release liner, an adherend, or the like) can be suppressed. It is preferable also from the viewpoint of keeping the flatness, transparency, refractive index, etc. of an adhesive layer constant that the fluctuation|variation of the moisture content in an adhesive layer can be suppressed. In addition, since a pressure-sensitive adhesive layer having a low water absorption rate is difficult to absorb moisture, it is suitable as a pressure-sensitive adhesive sheet used for products or members containing elements vulnerable to moisture, such as organic EL devices, for example.

In some embodiments, the water absorption of the pressure-sensitive adhesive layer is suitably approximately 1.0% or less, preferably 0.7% or less, more preferably 0.5% or less (for example, less than 0.5%), and may be 0.4% or less. , 0.3% or less may be sufficient, 0.2% or less may be sufficient, or 0.1% or less may be sufficient. The lower limit of the water absorption of the pressure-sensitive adhesive layer is not particularly limited, but may be, for example, 0.01% or more, 0.05% or more, 0.1% or more, or 0.15% or more from the viewpoint of practicality such as compatibility with adhesive properties. do. When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet having a first adhesive surface and a second pressure-sensitive adhesive surface, it is preferable that at least the water absorption of the pressure-sensitive 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 more preferable that the water absorption rates of the pressure-sensitive adhesive layer constituting the first adhesive surface and the pressure-sensitive adhesive layer constituting the second adhesive surface are restricted to a predetermined value or less.

In addition, the water absorption (also referred to as water content) of the pressure-sensitive adhesive layer is measured by the following method.

[Measurement of moisture content]

The pressure-sensitive adhesive layer to be evaluated was cut out to a size of 4 cm × 5 cm (area: 20 cm 2 ) together with two release liners disposed on one side and the other side, and the release liner on one side was cut out. is removed and bonded to a pre-weighed aluminum foil. Next, the peeling liner on the other side of the pressure-sensitive adhesive layer is removed, put into a constant temperature and humidity chamber at a temperature of 60°C and a relative humidity of 90%, and taken out after 72 hours. After weighing the test piece in which the adhesive layer and the aluminum foil are laminated, using a moisture meter (Mitsubishi Chemical Analytec CA-200 type) equipped with a heat vaporization device (Mitsubishi Chemical Analytec CA-200 type), Karl Fischer coulometric titration method By this, the moisture content is measured under the following conditions.

Anolyte: Aquamicron AKX (manufactured by Mitsubishi Chemical)

Catholyte: Aquamicron CXU (manufactured by Mitsubishi Chemical)

Heat vaporization temperature: 150°C

(gel fraction)

The gel fraction of the pressure-sensitive adhesive layer is appropriately set according to the purpose of use, the mode of use, and the like, and is not limited to a specific range. The gel fraction is, for example, about 99% or less, and about 97% or less is appropriate. From the viewpoint of making it easy to suitably achieve both a high refractive index and adhesive properties, in some preferred embodiments, the gel fraction may be approximately 95% or less, more preferably approximately 92% or less (for example, approximately 90% or less). have. If the gel fraction is not too high, it properly follows irregularities that may exist on the surface of the adherend (for example, a concave-convex structure provided for the purpose of improving light extraction efficiency in a light emitting device) and adheres well. It is also desirable from the point of view. In some embodiments, the gel fraction may be approximately 88% or less, approximately 75% or less, or approximately 65% or less. The gel fraction of the pressure-sensitive adhesive layer is, for example, about 10% or more, preferably about 20% or more, and about 30% or more, from the viewpoint of imparting appropriate cohesiveness to the pressure-sensitive adhesive and appropriately expressing adhesive properties. may be continued From the viewpoint of resistance to deformation of the pressure-sensitive adhesive layer (prevention of bubbles due to protrusion due to pressure or inclusion of foreign matter, etc.), the gel fraction is preferably about 30% or more, more preferably about 40% or more, It may be about 45% or more, about 50% or more, about 65% or more, or about 75% or more. It is preferable that the gel fraction of the PSA sheet (typically, the inorganic PSA sheet) also falls within the range exemplified above. The gel fraction can be adjusted by the molecular weight, molecular structure, concentration, degree of crosslinking, etc. of the acrylic polymer (A). Gel fraction is measured by the following method.

[Measurement of Gel Fraction]

A predetermined amount of the pressure-sensitive adhesive sample (weight Wg ₁ ) was wrapped in a drawstring bag with a porous polytetrafluoroethylene film (weight Wg ₂ ) having an average pore diameter of 0.2 μm, and the inlet was tied with a twine (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, a trade name "Nitoflon (registered trademark) NTF1122" available from Nitto Denko (average pore diameter: 0.2 µm, porosity: 75%, thickness: 85 µm) or an equivalent thereof is used. do.

The wrapped material is immersed in a sufficient amount of ethyl acetate, maintained at room temperature (typically 23° C.) for 7 days to elute only the sol content in the adhesive to the outside of the film, and then the wrapped material is taken out and the ethyl acetate adhering to the outer surface is obtained. is wiped off, and the wrapped thing is dried at 130°C for 2 hours, and the weight (Wg ₄ ) of the wrapped thing is measured. The gel fraction of the pressure-sensitive adhesive layer is obtained by substituting each value into the following formula.

Gel fraction (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet having a first adhesive surface and a second pressure-sensitive adhesive surface, the gel fraction described above is applied to at least the pressure-sensitive adhesive layer constituting the first adhesive surface, and preferably It is applied to both the pressure-sensitive adhesive layer constituting the first adhesive surface and the pressure-sensitive adhesive layer constituting the second adhesive surface. The gel fraction of the pressure-sensitive adhesive layer constituting the first adhesive surface and the gel fraction of the pressure-sensitive adhesive layer constituting the second adhesive surface may be the same or different.

(peel strength)

In some embodiments of the PSA sheet disclosed herein, the peel strength of the PSA sheet to the glass plate is suitably approximately 1.0 N/25 mm or more (eg 1.5 N/25 mm or more), preferably is 2 N/25 mm or more, more preferably 3 N/25 mm or more, may be 4 N/25 mm or more, may be 6 N/25 mm or more, may be 8 N/25 mm or more, may be 10 N/25 mm or more, 12 N/25 mm or more may be sufficient. The upper limit of the peel strength is not particularly limited, and may be, for example, 30 N/25 mm or less, 25 N/25 mm or less, or 20 N/25 mm or less.

Here, the peel strength is measured by bonding to 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 pressure defoaming device (autoclave) under conditions of a temperature of 50°C and a pressure of 0.5 MPa. After performing an autoclave treatment for 30 minutes and leaving it to stand for 24 hours in an atmosphere of 23 ° C. and 50% RH, it is understood by measuring the 180 ° peel adhesive force under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. In the measurement, if necessary, an appropriate adhesive backing material (for example, a polyethylene terephthalate (PET) film having a thickness of about 25 μm to about 50 μm) can be attached to the adhesive sheet to be measured for reinforcement. Peel strength can be measured more specifically according to the method described in the Example mentioned later.

When the PSA sheet disclosed herein is in the form of a double-sided PSA sheet having a first adhesive surface and a second adhesive surface, in some embodiments, the above-described peel strength is preferably applied to at least the first adhesive surface, , more preferably applied to both the first adhesive face and the second adhesive face. The peel strength of the first adhesive surface to the glass plate and the peel strength of the second adhesive surface to the glass may be the same or different.

(supporting material)

The pressure-sensitive adhesive sheet according to some aspects may be in the form of a pressure-sensitive adhesive sheet comprising a substrate having an adhesive layer on one side or both surfaces of the supporting substrate. The material of the supporting base material is not particularly limited and can be appropriately selected according to the purpose of use of the pressure-sensitive adhesive sheet or the mode of use. As a non-limiting example of the base material that can be used, a polyolefin film mainly composed of polyolefin such as polypropylene (PP) or ethylene-propylene copolymer, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene plastic films such as a polyester film containing polyester such as phthalate (PEN) as a main component and a polyvinyl chloride film containing polyvinyl chloride as a main component; foam sheets made of foams such as polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; woven fabrics and non-woven fabrics of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate) alone or blended; Paper, such as washi paper, fine paper, kraft paper, and crepe paper; metal foils such as aluminum foil and copper foil; etc. can be mentioned. A base material having a structure in which these are compounded may be used. Examples of such a composite substrate include, for example, a substrate having a structure in which metal foil and the aforementioned plastic film are laminated, and a plastic substrate reinforced with inorganic fibers such as glass cloth.

In some embodiments, various film substrates can be preferably used. The film substrate may be a porous substrate, such as a foam film or a non-woven fabric sheet, or a non-porous substrate, or a substrate having a structure in which a porous layer and a non-porous layer are laminated. In some aspects, as the film base material, one containing an independently shape-retainable (self-supporting or independent) resin film as a base film can be preferably used. Here, the "resin film" has a non-porous structure and typically means a resin film substantially free of air bubbles (voidless). Therefore, the resin film is a concept different from a foam film or a nonwoven fabric. As the resin film, one capable of independently maintaining its shape (self-supporting or independent) can be preferably used. The resin film may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

As a material constituting the resin film, for example, a polyester-based resin containing polyester as a main component, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyethylene (PE) , polyolefin resins mainly composed of polyolefins such as polypropylene (PP), ethylene-propylene copolymers, and ethylene-butene copolymers, cellulose resins such as triacetyl cellulose, acetate-based resins, polysulfone-based resins, and polyethersulfone-based resins. Resin, polycarbonate-based resin, polyamide (PA)-based resin such as nylon 6, nylon 66, partially aromatic polyamide, polyimide (PI)-based resin, transparent polyimide resin, polyamideimide (PAI), polyimide Ether ether ketone (PEEK), polyether sulfone (PES), cyclic polyolefin resins such as norbornene resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl alcohol copolymer resin, polyarylate resin, polyphenylene sulfide (PPS) resin, polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), and fluorine-based resins such as polytetrafluoroethylene (PTFE) and fluorinated polyimide.

The resin film may be formed using a resin material containing one type of such resin alone, or may be formed using a resin material in which two or more types are blended. The resin film may be unstretched or stretched (for example, uniaxial stretching or biaxial stretching). For example, PET film, PBT film, PEN film, unstretched polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, PP/ A PE blend film or the like can be preferably used. Examples of preferable resin films from the viewpoint of strength and dimensional stability include PET film, PEN film, PPS film and PEEK film. From the standpoint of availability, etc., a PET film and a PPS film are particularly preferred, and among these, a PET film is preferred.

In the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents are necessary to the extent that the effects of the present invention are not significantly impaired. can be combined according to The blending amount of the additive is not particularly limited and can be appropriately set according to the use of the pressure-sensitive adhesive sheet.

The manufacturing method of a resin film is not specifically limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die cast molding, and calender roll molding can be appropriately employed.

The substrate may be substantially constituted of such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an optical property adjustment layer (e.g., a coloring layer, an antireflection layer), a printed layer for imparting a desired appearance to the base material, a laminate layer, an antistatic layer, an undercoat layer, and a surface treatment layer such as a release layer. can be heard

In some aspects, as the support substrate, a substrate having light transmission properties (hereinafter, also referred to as a light transmission substrate) can be preferably employed. This makes it possible to construct a pressure-sensitive adhesive sheet comprising a base material having light transmission properties. The total light transmittance of the light transmissive substrate may be, for example, greater than 50% or greater than 70%. In some preferred aspects, the total light transmittance of the supporting substrate is 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a trade name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Genkyujo Co., Ltd. or an equivalent thereof is used. A preferable example of the light-transmitting substrate is a resin film having light-transmitting properties. An optical film may be sufficient as the said light transmissive base material.

The thickness of the base material is not particularly limited and can be selected according to the purpose of use of the pressure-sensitive adhesive sheet or the usage mode. The thickness of the substrate may be, for example, 500 μm or less, preferably 300 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, or 25 It may be ㎛ or less, and 10 ㎛ or less may be sufficient. When the thickness of the base material is reduced, the conformability to the surface shape of the adherend tends to be improved. Further, from the viewpoint of handleability, processability, etc., the thickness of the substrate may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

Conventionally, corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, formation of an undercoating layer by application of an undercoating agent (primer), etc. A known surface treatment may be performed. Such surface treatment may be a treatment for improving anchoring properties of the pressure-sensitive adhesive layer to the base material. The composition of the primer used for formation of the undercoat layer is not particularly limited, and can be appropriately selected from known ones. The thickness of the undercoating layer is not particularly limited, but is usually about 0.01 μm to 1 μm, and preferably about 0.1 μm to 1 μm. Other treatments that can be applied to the base material as needed include antistatic layer formation treatment, colored layer formation treatment, printing treatment, and the like. These treatments can be applied alone or in combination.

When the PSA sheet disclosed herein is in the form of a PSA sheet having a substrate, the thickness of the PSA sheet may be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, or 120 μm or less. It may be 75 μm or less, or 50 μm or less. In addition, 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 from the viewpoint of handleability or the like.

In addition, the thickness of an adhesive sheet means the thickness of the part affixed to the adherend. For example, in the PSA sheet 1 having the configuration shown in FIG. 1 , the thickness from the first surface (adhesive surface) 10A of the PSA layer to the second surface 20B of the supporting substrate is indicated, and the release liner 30 ) is not included.

<Adhesive Sheet with Release Liner>

The PSA sheet disclosed herein may take the form of an adhesive product in which the surface (adhesive surface) of the PSA layer is brought into contact with the release surface of the release liner. Therefore, according to this specification, a pressure-sensitive adhesive sheet (adhesive product) provided with a release liner is provided, including any of the pressure-sensitive adhesive sheets disclosed herein and a release liner having a release surface in contact with the adhesive surface of the pressure-sensitive adhesive sheet.

The release liner is not particularly limited, and examples thereof include a release liner having a release layer on the surface of a liner substrate such as a resin film or paper (which may be paper laminated with a resin such as polyethylene) or a fluorine-based polymer (polyethylene). A release liner made of a resin film formed of a low-adhesive material such as tetrafluoroethylene or the like) or a polyolefin-based resin (polyethylene, polypropylene, or the like) can be used. In terms of surface smoothness, a release liner having a release layer on the surface of a resin film as a liner base material or a release liner made of a resin film formed of a low-adhesive material can be preferably employed. The resin film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples include a polyethylene (PE) film, a polypropylene (PP) film, a polybutene film, a polybutadiene film, a polymethylpentene film, and a polymethylpentene film. A vinyl chloride film, a vinyl chloride copolymer film, a polyester film (PET film, PBT film, etc.), a polyurethane film, an ethylene-vinyl acetate copolymer film, etc. are mentioned. For the formation of the release layer, known release agents such as silicone-based release agents, long-chain alkyl-based release agents, olefin-based release agents, fluorine-based release agents, fatty acid amide-based release agents, molybdenum sulfide, and silica powder can be used. have.

<Use>

The pressure-sensitive adhesive sheet disclosed herein can be used by being bonded to various adherends. The constituent material of the adherend (adherent material) is not particularly limited, and examples thereof include copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, etc., or among these Metal materials such as alloys containing two or more types, for example, polyimide-based resins, acrylic resins, polyethernitrile-based resins, polyethersulfone-based resins, polyester-based resins (PET-based resins, polyethylene naphthalate-based resins) etc.), polyvinyl chloride-based resins, polyphenylene sulfide-based resins, polyether ether ketone-based resins, polyamide-based resins (so-called aramid resins, etc.), polyarylate-based resins, fluorine-based resins, polycarbonate-based resins, Cellulose polymers such as acetyl cellulose and triacetyl cellulose, vinyl butyral polymers, liquid crystal polymers, various resin materials (typically plastic materials) such as carbon materials such as graphene, alumina, zirconia, titania, SiO ₂ , ITO ( metal oxides and mixtures thereof, such as indium tin oxide) and ATO (antimony-doped tin oxide), nitrides and composites thereof, such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, and indium nitride, alkali glass, alkali-free glass, quartz glass, Inorganic materials, such as borosilicate glass and sapphire glass, etc. are mentioned. The pressure-sensitive adhesive sheet disclosed herein may be used by being attached to a member (for example, an optical member) having at least a surface composed of the above material.

The PSA sheet disclosed herein can be used in an adhesive mode that does not require heating at a temperature higher than a temperature range of about room temperature (for example, 20° C. to 35° C.) after being bonded to an adherend. In addition, if it is allowed depending on the constituent material of the adhesive sheet (for example, the material of the base material) or the type of adherend, heat treatment is performed at at least any timing of after bonding to the adherend, at the time of bonding, and before bonding. You can do it. The heat treatment can be performed for the purpose of improving the adhesion of the pressure-sensitive adhesive to the adherend or promoting adhesion. The heat treatment temperature can be appropriately set so as to obtain a desired effect, taking into consideration the surface state of the adherend, etc. within an allowable range depending on the material of the adhesive sheet and the type of adherend, and is, for example, about 100°C or higher. It may be less than or equal to 80°C, may be less than or equal to 60°C, or may be less than or equal to 50°C.

The member or material to which the PSA sheet is applied (at least one of the adherends in the PSA sheet on both sides) may have light transmission properties. In such an adherend, it is easy to obtain the advantage of increasing the refractive index while suppressing a decrease in optical properties (such as transparency) by applying the technique disclosed herein. The total light transmittance of the adherend may be, for example, greater than 50% or greater than 70%. In some preferred embodiments, the adherend has a total light transmittance of 80% or more, more preferably 90% or more, still more preferably 95% or more (for example, 95 to 100%). The pressure-sensitive adhesive sheet disclosed herein can be preferably used in an aspect of sticking to an adherend having a total light transmittance of a predetermined value or higher (for example, an optical member). The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a trade name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Genkyujo Co., Ltd. or an equivalent thereof is used.

The refractive index of the pressure-sensitive adhesive layer and the refractive index of the adherend may be the same or different. For example, by making the refractive index of the pressure-sensitive adhesive layer relatively high compared to the refractive index of the adherend, light incident from the adherend side to the pressure-sensitive adhesive layer at an angle of less than a critical angle is refracted toward the front side, and the front luminance can be increased. In this case, 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 may be, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. In addition, according to the adherend having a relatively high refractive index compared to the pressure-sensitive adhesive layer, light incident on the adherend from the pressure-sensitive adhesive layer side is refracted toward the front side, and the front luminance can be increased. In this case, the refractive index of the adherend may be, for example, 1.60 or more, 1.65 or more, or 1.70 or more, and may be, for example, 3.00 or less, 2.50 or less, or 2.00 or less. On the other hand, light reflection at the interface can be suppressed by reducing the refractive index difference between the pressure-sensitive adhesive layer and the adherend. In this case, 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 pressure-sensitive adhesive.

In some preferred aspects, the adherend may have any of the refractive indexes described above and may have a total light transmittance of any of the above. In such an aspect of sticking to an adherend, the effect of the technique disclosed herein is particularly preferably exhibited.

An example of a preferred application is an optical application. More specifically, it is a pressure-sensitive adhesive sheet for optics used, for example, for bonding optical members (for bonding optical members) or for manufacturing a product (optical product) using the optical member, which is disclosed herein. can be preferably used.

The optical member refers to a member having optical properties (eg, polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, rotation, visibility, etc.). The optical member is not particularly limited as long as it has optical properties, but examples include members constituting devices (optical devices) such as display devices (image display devices) and input devices, or members used in these devices. It may be, for example, a polarizing plate, a wave plate, a retardation plate, an optical compensation film, a brightness enhancement film, a light guide plate, a reflective film, an anti-reflection film, a hard coat (HC) film, an impact absorbing film, an antifouling film, a photochromic film, Light control film, transparent conductive film (ITO film), design film, decorative film, surface protection plate, prism, lens, color filter, transparent substrate, and further members laminated thereon (these are collectively referred to as “functional film” in some cases) ) and the like. In addition, the said "plate" and "film" shall include forms, such as a plate shape, a film shape, and a sheet shape, respectively, For example, a "polarizing film" includes a "polarizing plate", a "polarizing sheet", etc. , "light guide plate" includes "light guide film" or "light guide sheet". In addition, the said "polarizing plate" shall contain a circular polarizing plate.

Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a micro LED (μLED), a mini LED (miniLED), a PDP (plasma display panel), and electronic paper. Moreover, as said input device, a touchscreen etc. are mentioned.

Examples of the optical member include, but are not particularly limited to, members made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin film, etc. (for example, sheet-like, film-like, or plate-like members) can be heard In addition, the "optical member" in this specification includes members (decorative film, decorative film, surface protection film, etc.) that play a role of decoration or protection while maintaining the visibility of the display device or input device.

The technology disclosed herein is, for example, a film having one or more functions such as light transmission, reflection, diffusion, waveguide, condensation, diffraction, etc., or an optical film such as a fluorescent film, other optical members (can be other optical films). in) can be preferably used for bonding. Among them, in bonding an optical film having at least one function of light guide, light condensation, and diffraction, it is preferable that the entire bulk of the bonding layer has a high refractive index, and the technology disclosed herein can be a preferable application target.

The pressure-sensitive adhesive disclosed herein can be suitably used for bonding optical films such as a light guide film, a diffusion film, a fluorescent film, a toning film, a prism sheet, a lenticular film, and a microlens array film. In these applications, from the viewpoints of miniaturization and high performance of optical members, reduction in thickness and improvement in light extraction efficiency are required. As a pressure-sensitive adhesive that can meet such a request, the pressure-sensitive adhesive disclosed herein can be preferably used. In more detail, for example, in bonding of a light guide film or a diffusion film, it is possible to contribute to thickness reduction by adjusting the refractive index of the pressure-sensitive adhesive layer as a bonding layer (for example, increasing the refractive index). In the bonding of the fluorescent film, the light extraction efficiency (which can also be understood as luminous efficiency) can be improved by appropriately adjusting the difference in refractive index between the fluorescent light emitting body and the pressure-sensitive adhesive. In the bonding of the toning film, scattering components can be reduced by appropriately adjusting the refractive index of the pressure-sensitive adhesive so that the refractive index difference with the coloring pigment is reduced, thereby contributing to improvement in light transmittance. In bonding such as a prism sheet, a lenticular film, a microlens array film, etc., diffraction of light can be controlled by appropriately adjusting the refractive index of the pressure-sensitive adhesive, thereby contributing to improvement in luminance and/or viewing angle.

The adhesive sheet disclosed herein is preferably used in an aspect of being adhered to an adherend having a high refractive index (which may be a layer or a member having a high refractive index), and can suppress interfacial reflection with the adherend. As described above, the pressure-sensitive adhesive sheet used in this aspect preferably has a small difference in refractive index with the adherend and high adhesion at the interface with the adherend. Further, from the viewpoint of enhancing the homogeneity of appearance, it is preferable that the pressure-sensitive adhesive layer has high uniformity in thickness, and for example, it is preferable that the surface smoothness of the adhesive surface is high. When the thickness of the high refractive index adherend is relatively small (for example, 5 μm or less, 4 μm or less, or 2 μm or less), reflection at the interface is prevented from the viewpoint of suppressing coloration and color unevenness due to interference of reflected light. suppression is particularly meaningful. As an example of such a usage aspect, in a polarizing plate having a polarizer, a first retardation layer, and a retardation layer including a second retardation layer in this order, bonding of the polarizer and the first retardation layer and / or the first retardation An aspect used for bonding the layer and the second retardation layer may be mentioned.

In addition, since the pressure-sensitive adhesive sheet disclosed herein is suitable for high refractive index, it can be preferably used in an aspect attached to a light-emitting layer such as an optical semiconductor (for example, a high-refractive light-emitting layer mainly composed of inorganic materials). By reducing the difference in refractive index between the light-emitting layer and the pressure-sensitive adhesive layer, reflection at the interface between them can be suppressed and the light extraction efficiency can be improved. It is preferable that the pressure-sensitive adhesive sheet used in this aspect includes a pressure-sensitive adhesive layer having a high refractive index. In addition, from the viewpoint of preventing deterioration of the self-luminous element due to moisture, it is preferable that the water absorption rate of the pressure-sensitive adhesive layer is low. From the viewpoint of improving the brightness, the pressure-sensitive adhesive sheet is preferably low-colored. This can also be advantageous from the viewpoint of suppressing unintentional coloring caused by the pressure-sensitive adhesive sheet.

The adhesive disclosed herein is applied to microlenses and other lens members (for example, microlenses constituting a microlens array film and lens members such as microlenses for cameras) used as constituent members of cameras, light emitting devices, and the like. In this case, it is preferable as a coating layer covering the lens surface, a bonding layer with a member facing the lens surface (eg, a member having a surface shape corresponding to the lens surface), a filling layer filled between the lens surface and the member, and the like. can be used Since the pressure-sensitive adhesive disclosed herein is suitable for high refractive index, even if it is a high refractive index lens (for example, a lens made of a high refractive index resin or a lens having a surface layer of a high refractive index resin), the refractive index of the lens car can be reduced. This is advantageous from the viewpoint of reducing the thickness of the lens and the product provided with the lens, and can also contribute to suppression of aberration and improvement of Abbe's number. The pressure-sensitive adhesive disclosed herein may be used as a lens resin by itself, for example, in the form of being filled in the recesses or voids of an appropriate transparent member.

The aspect of bonding optical members using the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, but examples include (1) an aspect of bonding optical members together through the pressure-sensitive adhesive sheet disclosed herein, and (2) here may be an aspect in which the optical member is bonded to a member other than the optical member through the PSA sheet disclosed herein, (3) the PSA sheet disclosed herein includes an optical member, and the PSA sheet is attached to an optical member or a member other than the optical member. An aspect joined to a member may be sufficient. In the aspect (3) above, the pressure-sensitive adhesive sheet having an optical member may be, for example, a pressure-sensitive adhesive sheet in which the support is an optical member (eg, an optical film). Such a pressure-sensitive adhesive sheet including an optical member as a support may also be regarded as a pressure-sensitive adhesive optical member (eg, a pressure-sensitive adhesive optical film). In addition, when the PSA sheet disclosed herein is a PSA sheet having a support and the functional film is used as the support, the PSA sheet disclosed herein includes a PSA layer disclosed herein on at least one side of the functional film. It can also be understood as an "adhesive functional film" having.

From the above, according to the technology disclosed herein, a laminate comprising the PSA sheet disclosed herein and a member to which the PSA sheet is attached is provided. The member to which the adhesive sheet is affixed may have the refractive index of the above-mentioned adherend material. Further, the difference between the refractive index of the adhesive sheet and the refractive index of the member (difference in refractive index) may be the above-described difference in refractive index between the adherend and the adhesive sheet. Since the members constituting the laminate are as described above as the members, materials, and adherends, overlapping descriptions will not be repeated.

As understood from the above description and the following examples, the matters disclosed by this specification include the following.

[1] A pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer,

It has an adhesive surface constituted by the pressure-sensitive adhesive layer,

The pressure-sensitive adhesive layer has a refractive index of more than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

[2] The pressure-sensitive adhesive sheet according to [1], wherein the pressure-sensitive adhesive layer has a thickness of 5 µm or more.

[3] The adhesive sheet according to [1] or [2], wherein the peel strength (adhesive force) to the glass plate is 3 N/25 mm or more.

[4] The adhesive sheet according to any one of [1] to [3], wherein the adhesive surface has an arithmetic mean roughness Ra of 100 nm or less.

[5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the pressure-sensitive adhesive layer has a water absorption of 1.0% or less.

[6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], configured as a laminate comprising the pressure-sensitive adhesive layer and a light-transmitting substrate.

[7] The adhesive sheet according to [6], wherein the light-transmitting substrate is a resin film.

[8] The pressure-sensitive adhesive sheet according to any one of [1] to [5], which is a double-sided adhesive pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer.

[9] The pressure-sensitive adhesive sheet according to any one of [1] to [8] above;

A release liner disposed on the adhesive side of the adhesive sheet

A pressure-sensitive adhesive sheet comprising a release liner.

[10] A pressure-sensitive adhesive composition used to form a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to [8].

[11] an acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit;

Additive (H _RO ) which is an organic material having a higher refractive index than the acrylic polymer (A)

Containing, the pressure-sensitive adhesive composition.

[12] The adhesive composition according to [11], wherein the additive (H _RO ) has a refractive index of 1.60 or more.

[13] The adhesive composition according to [11] or [12], wherein the content of the additive (H _RO ) with respect to 100 parts by weight of the acrylic polymer (A) is greater than 0 parts by weight and not greater than 60 parts by weight.

[14] The adhesive composition according to any one of [11] to [13], wherein the additive (H _RO ) contains at least one compound selected from the group consisting of an aromatic ring-containing compound and a heterocycle-containing compound.

[15] The adhesive composition according to any one of [11] to [14], wherein the additive (H _RO ) contains a compound having two or more aromatic rings in one molecule.

[16] The additive (H _RO ) is a compound having two or more aromatic rings in one molecule,

(i) containing a structure in which two non-condensed aromatic rings are directly chemically bonded, and

(ii) containing a structure in which two aromatic rings are condensed

The pressure-sensitive adhesive composition according to [15] above, comprising a compound satisfying at least one of the above.

[17] The pressure-sensitive adhesive composition according to any one of [11] to [16], wherein, in the monomer components constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is 50% by weight or more.

[18] 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,

The adhesive composition according to any one of [11] to [17] above, wherein 50% by weight or more of the aromatic ring-containing monomer (m1) is a monomer having a homopolymer glass transition temperature of 10°C or less.

[19] The adhesive composition according to any one of [11] to [18], wherein the monomer component constituting the acrylic polymer (A) further contains a monomer (m2) having at least one of a hydroxyl group and a carboxy group.

[20] The pressure-sensitive adhesive composition according to any one of [11] to [18], which is used for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to [8].

[21] A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition according to any one of [11] to [20], and having a refractive index higher than 1.570.

[22] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition according to any one of [11] to [20].

[23] The pressure-sensitive adhesive sheet according to [22], wherein the pressure-sensitive adhesive layer has a haze value of 1.0% or less.

[24] An interlayer sheet used by placing it between the layers of a laminate in optical applications,

a viscoelastic layer V ₁ having a refractive index n ₁ of 1.570 or more; and

Those with a total light transmittance of 86% or more;

Haze value is 1.0 % or less; and,

Those whose storage elastic modulus G' at 25°C is 30 kPa to 700 kPa;

to meet the interlayer sheet.

[25] The interlayer sheet according to [24] above, having a thickness of 5 μm or more.

[26] The interlayer sheet according to [24] or [25], wherein the viscoelastic layer V ₁ includes a main polymer and a plasticizing material having a molecular weight lower than that of the main polymer.

[27] The interlayer sheet according to [26], wherein the plasticizing material has a weight average molecular weight of 30000 or less.

[28] Further comprising a viscoelastic layer V ₂ laminated on the viscoelastic layer V ₁ ,

The storage modulus G′ _V2 of the viscoelastic layer V ₂ at 25° C. is lower than the storage modulus G′ _V1 of the viscoelastic layer V ₁ at 25° C. between layers according to any one of [24] to [27]. Sheet.

[29] The interlayer sheet according to [28], wherein the refractive index n ₂ of the viscoelastic layer V ₂ is lower than the refractive index n ₁ of the viscoelastic layer V ₁ .

[30] The interlayer sheet according to any one of [24] to [29], wherein the viscoelastic layer V ₁ is a layer formed of the pressure-sensitive adhesive composition according to any one of [11] to [18].

[31] The interlayer sheet according to any one of [24] to [29], wherein the viscoelastic layer V ₁ is a pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet according to any one of [1] to [5].

[32] The interlayer sheet according to any one of [24] to [31] above;

A resin film laminated on the interlayer sheet

Including, the optical laminate.

[33] The interlayer sheet according to any one of [24] to [31],

A release liner covering at least one surface of the interlayer sheet.

An interlayer sheet having a release liner comprising a.

Example

Hereinafter, several examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the specific examples. In addition, in the following description, "part" and "%" which show usage amount or content are based on weight unless otherwise specified.

<Example 1>

(Preparation of acrylic polymer solution)

In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet pipe, and a condenser, m-phenoxybenzyl acrylate (manufactured by Kyoesha Chemical Co., Ltd., trade name "Light Acrylate POB-A" as a monomer component, Refractive index: 1.566, Tg of homopolymer: -35 ° C. (hereinafter abbreviated as "POB-A") 95 parts and 4-hydroxybutyl acrylate (4HBA) 5 parts, 2,2'-azobis as a polymerization initiator 0.2 part of isobutyronitrile (AIBN) and 100 parts of toluene as a polymerization solvent were introduced, nitrogen gas was introduced while gently stirring, the liquid temperature in the flask was maintained at around 60 ° C, and polymerization was carried out for 6 hours, acrylic polymer A1 A solution (50%) of was prepared. The polymerization average molecular weight (Mw) of this acrylic polymer A1 was 500,000. The acrylic polymer A1 has a Tg based on the composition of the monomer component (ie, Tg _T ) of -35°C, and a Tg based on the composition of the aromatic ring-containing monomer (ie, Tg _m1 ) of -35°C.

(Preparation of adhesive composition)

A solution (50%) of the acrylic polymer _A1 was diluted to 30% with ethyl acetate, and 6-acryloyloxymethyldinaphthothiophene ( Dinaphthothiophene-6-methylacrylate, trade name "6MDNTA", refractive index 1.75) manufactured by Sugai Chemical Industry Co., Ltd., 5 parts, as a crosslinking agent, isocyanurate of hexamethylene diisocyanate (trade name, manufactured by Tosoh Corporation) "Coronate HX", a trifunctional isocyanate compound) 10 parts of ethyl acetate solution (0.1 part of non-volatile matter), 2 parts of acetylacetone as a crosslinking retardant, 1% ethyl acetate solution of ferric nasem as a crosslinking catalyst 1 part (0.01 part of non-volatile content) was added and stirred and mixed to prepare an acrylic pressure-sensitive adhesive composition C1.

(Manufacture of adhesive sheet)

The acrylic pressure-sensitive adhesive composition C1 prepared above was applied to the silicone-treated surface of polyethylene terephthalate (PET) film R1 (thickness: 50 μm), which was silicone-treated on one side, and heated at 130° C. for 2 minutes to obtain a pressure-sensitive adhesive having a thickness of 25 μm. layer was formed. Next, the silicone-treated surface of PET film R2 (thickness: 25 μm), which was subjected to silicone treatment on one side, was bonded to the surface of the pressure-sensitive adhesive layer. In this way, an inorganic double-sided pressure-sensitive adhesive sheet S1 composed of the pressure-sensitive adhesive layer was obtained. Both surfaces of PSA sheet S1 are protected by PET films (release liners) R1 and R2.

<Examples 2 to 5>

Except for changing the type of additive (H _RO ) and the amount used (phr; per hundred resin) for 100 parts of the acrylic polymer as shown in Table 1, in the same manner as in the preparation of the acrylic pressure-sensitive adhesive composition C1 in Example 1, Example Acrylic pressure-sensitive adhesive compositions C2 to C5 according to Examples 2 to 5 were prepared. Here, "BPFL" in Table 1 represents 9,9-bis(4-hydroxyphenyl)fluorene (manufactured by Osaka Gas Chemical Co., Ltd., refractive index: 1.68), and "BAFL" represents 9,9-bis(4-hydroxyphenyl)fluorene. -Aminophenyl) fluorene (Osaka Gas Chemical Co., Ltd. make, refractive index 1.73) is shown.

PSA sheets according to Examples 2 to 5 in the same manner as in the production of the PSA sheet in Example 1 except that the acrylic PSA compositions C2 to C5 were used instead of the acrylic PSA composition C1 (inorganic double-sided PSA sheet made of PSA layer) S2 to S5 were produced.

<Example 6>

In a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet pipe, 20 parts of POB-A and 1-naphthylmethyl acrylate (manufactured by Kyoesha Chemical Co., Ltd., trade name "Light Acrylate NMT-A", refractive index: 1.595, homopolymer Tg: 31°C. Hereinafter abbreviated as "NMT-A"), 80 parts, AIBN as a polymerization initiator, 0.2 parts, and α-thioglycerol as a chain transfer agent, 3.5 parts. After throwing in , and 67 parts of methyl ethyl ketone, nitrogen gas was flowed and nitrogen substitution was performed for about 1 hour, stirring. Thereafter, 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.

Except that the type of additive (H _RO ) was changed to the above-mentioned oligomer B and the amount thereof was changed to 30 parts (30 phr) with respect to 100 parts of the acrylic polymer, in the same manner as in the preparation of the acrylic pressure-sensitive adhesive composition C1 in Example 1, this An acrylic pressure-sensitive adhesive composition C6 according to Example was prepared.

Except for using the acrylic PSA composition C6 instead of the acrylic PSA composition C1, in the same manner as in the production of the PSA sheet in Example 1, PSA sheet (inorganic double-sided PSA sheet made of PSA layer) S6 was prepared.

<Example 7>

Acrylic adhesive composition C7 was prepared in the same manner as in the preparation of acrylic adhesive composition C1 in Example 1 except that the additive (H _RO ) was not used.

The PSA sheet according to this example (consisting of the PSA layer Inorganic material double-sided adhesive sheet) S7 was produced.

<Example 8>

A solution of acrylic polymer A2 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 72 parts for POB-A, 23 parts for NMT-A, and 5 parts for 4HBA. . The polymerization average molecular weight (Mw) of this acrylic polymer A2 was 450,000.

Except for using the solution of acrylic polymer A2 instead of the solution of acrylic polymer A1, it carried out similarly to preparation of the adhesive composition in Example 1, and prepared the acrylic adhesive composition C8 concerning this example.

Except for using the acrylic PSA composition C8 instead of the acrylic PSA composition C1, in the same manner as in the production of the PSA sheet in Example 1, PSA sheet (inorganic double-sided PSA sheet made of PSA layer) S8 was prepared.

<Examples 9 to 13>

Acrylic PSA compositions C9 to C13 according to Examples 9 to 13 were prepared in the same manner as in the preparation of Acrylic PSA composition C8 in Example 8, except that the type and amount of the additive (H _RO ) was changed as shown in Table 1. did

PSA sheets according to Examples 9 to 13 in the same manner as in the production of the PSA sheet in Example A1 (inorganic double-sided PSA sheet made of PSA layer) S9 to S13 were produced.

<Example 14>

Acrylic pressure-sensitive adhesive composition C14 according to Example 14 was prepared in the same manner as in the preparation of acrylic pressure-sensitive adhesive composition C8 in Example 8 except that the additive (H _RO ) was not used.

Except for using the acrylic pressure-sensitive adhesive composition C8 instead of the acrylic pressure-sensitive adhesive composition C14, in the same manner as in the production of the pressure-sensitive adhesive sheet in Example 8, the pressure-sensitive adhesive sheet (inorganic double-sided pressure-sensitive adhesive composed of pressure-sensitive adhesive layer) S14 was prepared.

<Example 15>

A solution of acrylic polymer A3 (40%) 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 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of 4HBA. was prepared.

A solution (40%) of the acrylic polymer A3 was diluted to 20% with ethyl acetate, and to 500 parts of this solution (100 parts of non-volatile matter), 10 parts of zirconia particle dispersion based on solid content, as a crosslinking agent, hexamethylene diisocyanate iso 10 parts of 1% ethyl acetate solution of cyanurate (trade name "Coronate HX", trifunctional isocyanate compound manufactured by Tosoh Corporation) (0.1 part of non-volatile content), 2 parts of acetylacetone as a crosslinking retardant, and 2 parts of acetylacetone as a crosslinking catalyst 1 part (0.01 part of non-volatile content) of 1% ferric iron ethyl acetate solution was added and stirred and mixed to prepare acrylic pressure-sensitive adhesive composition C15. As the dispersion of zirconia particles, surface-treated zirconia particles (average particle size: 20 nm, refractive index of solid content: 1.64, surface treatment: carboxylic acid/phosphoric acid-based hydrophobic treatment, manufactured by Kyoesha Chemical Co., Ltd.) were mixed with propylene glycol monomethyl A dispersion of surface-treated zirconia particles dispersed in ether (PGME) was used.

The PSA sheet according to Example 15 (inorganic Double-sided adhesive sheet) S15 was produced.

<Example 16>

A solution of acrylic polymer A4 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 component was changed to POB-A/n-butylacrylate (BA)/4HBA=79/20/1 did The polymerization average molecular weight (Mw) of acrylic polymer A4 was 520,000.

Acrylic PSA composition C16 according to this example was prepared in the same manner as in Example 2 except that the solution of acrylic polymer A4 was used instead of the solution of acrylic polymer A1, and pressure-sensitive adhesive sheet (inorganic double-sided pressure-sensitive adhesive sheet made of pressure-sensitive adhesive layer) S16 was prepared. did

<Example 17>

A solution of acrylic polymer A5 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 component was changed to POB-A/ethylcarbitol acrylate (CBA)/4HBA=79/20/1 did The polymerization average molecular weight (Mw) of acrylic polymer A5 was 460,000.

Acrylic PSA composition C17 according to this example was prepared in the same manner as in Example 2 except that the solution of acrylic polymer A4 was used instead of the solution of acrylic polymer A1, and pressure-sensitive adhesive sheet (inorganic double-sided pressure-sensitive adhesive sheet made of pressure-sensitive adhesive layer) S17 was prepared. did

<Example 18>

A solution of acrylic polymer A6 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 component was changed to POB-A/phenoxydiethylene glycol acrylate/4HBA=79/20/1. As phenoxydiethylene glycol acrylate, Kyoeisha Chemical Co., Ltd. trade name "light acrylate P2H-A" was used. The polymerization average molecular weight (Mw) of acrylic polymer A6 was 480,000.

Acrylic PSA composition C18 according to this example was prepared in the same manner as in Example 2 except that the solution of acrylic polymer A6 was used instead of the solution of acrylic polymer A1, and pressure-sensitive adhesive sheet (inorganic double-sided pressure-sensitive adhesive sheet made of pressure-sensitive adhesive layer) S18 was prepared. did

<Example 19>

In the same manner as in Example 2 except that the additive (H _RO ) was changed to 2,12-diallyloxydinaphthothiophene (manufactured by Sugai Chemical Industry Co., Ltd., abbreviation: 2,12-DAODNT, refractive index 1.729), this The acrylic pressure-sensitive adhesive composition C19 according to Example was prepared, and pressure-sensitive adhesive sheet (inorganic double-sided pressure-sensitive adhesive sheet made of pressure-sensitive adhesive layer) S19 was produced.

<Examples 20 to 22>

Acrylic PSA compositions C20 to 22 were prepared in the same manner as in Examples 16 to 18, except that the additive (H _RO ) was not used, and PSA sheets (inorganic double-sided PSA sheets made of PSA layers) S20 to 22 were prepared did

<Measurement and evaluation>

(refractive index)

Regarding the pressure-sensitive adhesive layer (inorganic double-sided pressure-sensitive adhesive sheet) related to each case, the refractive index was measured using an Abbe refractometer (manufactured by ATAGO, type "DR-M4") under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25 ° C. . The results are shown in Tables 1 and 2.

(Total light transmittance and haze value)

Using a test piece in which the pressure-sensitive adhesive layer according to each example was bonded to non-alkali glass (thickness: 0.8 to 1.0 mm, total light transmittance: 92%, haze: 0.4%), in a measurement environment of 23°C, a haze meter (Murakami Shikisai Gijutsu The total light transmittance and haze of the said test piece were measured using Genkyujo Co., Ltd. product name "HAZEMETER HM-150"). The value obtained by subtracting the total light transmittance and haze of the alkali-free glass from the measured value was used as the total light transmittance and haze value of the pressure-sensitive adhesive layer. The results are shown in Tables 1 and 2.

(Storage modulus G')

A sample for measurement was obtained by laminating the pressure-sensitive adhesive layer according to each case to a thickness of about 1.5 mm. Dynamic viscoelasticity was measured under the following conditions using ARES manufactured by TA Instruments. From the measurement results, the storage elastic modulus G' at 25°C was read. The results are shown in Tables 1 and 2.

[Measuring conditions]

Deformation Mode: Torsion

Measurement frequency: 1Hz

Heating rate: 5°C/min

Shape: Parallel plate 7.9mmφ

(peel strength)

For the PSA sheet according to each example, the peel strength to the glass plate was measured. That is, in a measurement environment of 23°C and 50% RH, the release liner is peeled off from one side of the pressure-sensitive adhesive sheet, and a PET film having a thickness of 50 µm is bonded and backed, and then a size of 25 mm in width and 100 mm in length is obtained. What was cut was made into the test piece. The release liner on the other side was peeled off from the test piece, and the surface of an alkali glass plate (manufactured by Matsunami Glass Industrial Co., Ltd., thickness 1.35 mm, polished blue plate) as an adherend was pressed by pressing a 2 kg roller once. This was left in the same environment for 30 minutes, then put into a pressurized defoaming device (autoclave), and autoclave treatment was performed for 30 minutes under the conditions of a temperature of 50 ° C. and a pressure of 0.5 MPa, and further in an atmosphere of 23 ° C. and 50% RH. After leaving it to stand for 24 hours, the peel strength (adhesive force) [N/25 mm] was measured using a universal tensile compression tester in accordance with JIS Z 0237: 2000 under conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees. . As a universal tension and compression tester, "Tension and compression tester, TG-1kN" manufactured by Minebea Co., Ltd. was used. The results are shown in Tables 1 and 2.

As shown in Table 1, the adhesives of Examples 1 to 6 in which the additive (H _RO ) was added to the adhesive of Example 7 containing no additive (H _RO ) exhibited a higher refractive index than that of Example 7. These pressure-sensitive adhesives had high transparency and good peel strength. The same trend was observed in the comparison between Example 14 and Examples 8 to 13. On the other hand, Example 15, in which the refractive index was improved by blending high refractive index inorganic particles, is clearly inferior to Examples 1 to 14 in transparency (particularly, the haze is remarkably high), and also has adhesive performance suitable for practical use as an adhesive (peel strength). that did not indicate

Also in Examples 16 to 19 shown in Table 2, it was confirmed that the effect of improving the refractive index was exhibited by use of the additive (H _RO ). The adhesives of Examples 16 to 19 had high transparency and good peel strength.

From the above, the pressure-sensitive adhesives of Examples 1 to 6, Examples 8 to 13, and Examples 16 to 19 have a high refractive index while suppressing deterioration in optical properties, and therefore, the optical member (for example, during light guide, condensation, and diffraction). It is suitable for applications such as bonding of optical films having at least one function).

As mentioned above, although the specific example of this invention was demonstrated in detail, these are only examples and do not limit the claim. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

1, 2: adhesive sheet
10: adhesive layer
10A: first surface (adhesive surface)
10B: second surface
20: supporting substrate
20A: first side
20B: second surface (rear surface)
30, 31, 32: release liner
50: adhesive sheet with release liner
70: optical member
100: member provided with adhesive sheet

Claims (12)

An acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit;
Additive (H _RO ) which is an organic material having a higher refractive index than the acrylic polymer (A)
Containing, the pressure-sensitive adhesive composition. According to claim 1,
The refractive index of the additive (H _RO ) is 1.60 or more, the pressure-sensitive adhesive composition. According to claim 1 or 2,
The content of the additive (H _RO ) with respect to 100 parts by weight of the acrylic polymer (A) is more than 0 parts by weight and is 60 parts by weight or less, the pressure-sensitive adhesive composition. According to any one of claims 1 to 3,
The additive (H _RO ) includes at least one compound selected from the group consisting of an aromatic ring-containing compound and a heterocycle-containing compound. According to any one of claims 1 to 4,
The additive (H _RO ) includes a compound having two or more aromatic rings in one molecule. According to claim 5,
The additive (H _RO ) is a compound having two or more aromatic rings in one molecule,
(i) containing a structure in which two non-condensed aromatic rings are directly chemically bonded, and
(ii) containing a structure in which two aromatic rings are condensed
A pressure-sensitive adhesive composition comprising a compound satisfying at least one of the above. According to any one of claims 1 to 6,
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 pressure-sensitive adhesive composition. According to any one of claims 1 to 7,
In the monomer component constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is more than 70% by weight and less than 100% by weight,
The adhesive composition in which 50 weight% or more of the said aromatic ring containing monomer (m1) is a monomer whose glass transition temperature of a homopolymer is 10 degrees C or less. According to any one of claims 1 to 8,
The adhesive composition in which the monomer component which comprises the said acrylic polymer (A) further contains the monomer (m2) which has at least one of a hydroxyl group and a carboxy group. A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 9, and having a refractive index higher than 1.570. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 9. According to claim 11,
The pressure-sensitive adhesive sheet having a haze value of the pressure-sensitive adhesive layer is 1.0% or less.

Images