Adhesive composition, adhesive, and adhesive sheet

Abstract

Provided is an adhesive composition including: an acrylic polymer (A) containing a monomer (m1) containing an aromatic ring as a monomer unit; and an additive (H RO ) which is an organic material having a higher refractive index than the above-described acrylic polymer (A). Further, provided is an adhesive sheet having an adhesive formed from the above-described adhesive composition.

Description

TECHNICAL FIELD

[0001] The present application relates to an adhesive composition, an adhesive, and an adhesive sheet.

[0002] This application is based on Japanese Patent Application No. 2020-052408 filed on March 24, 2020, Japanese Patent Application No. 2020-166426 filed on September 30, 2020, and Japanese Patent Application No. 2021-049059 filed on March 23, 2021, the contents of which are incorporated herein by reference in its entirety. BACKGROUND

[0003] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter.) has a property of being simply adhered to an adherend by pressure, in a state of a soft solid (viscoelastic body) in a temperature region around room temperature. With this property, the adhesive is widely used in various industrial fields from home electric appliances to automobiles, various machines, electrical devices, electronic devices, and the like, for the purpose of joining, fixing, protection, and the like. As an example of the use of the adhesive, there can be cited a use of joining a polarizing film, a phase difference film, a cover window member, other various light-transmissive members, and other members in a display device such as a liquid crystal display device, an organic EL display device, and the like. As a technical document relating to an adhesive for optical members, there can be cited Patent Documents 1 and 2.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-169382

[0007] Patent Document 2: Japanese Patent Application Publication No. 2017-128732 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Patent documents 1 and 2 disclose adhesive compositions with (meth)acrylate polymers as the main component, and adhesives formed by crosslinking such adhesive compositions, wherein the (meth)acrylate polymer contains monomers having multiple aromatic rings as monomer units. However, in the technologies described in Patent Documents 1 and 2, it is difficult to obtain adhesives with a refractive index higher than that of the aforementioned (meth)acrylate polymers. On the other hand, it is also known to increase the refractive index by incorporating particles formed from high-refractive-index inorganic materials (such as zirconium oxide particles, titanium oxide particles, etc.) into a resin, but the refractive index of adhesives incorporating inorganic particles is in a trade-off with adhesive properties (such as peel strength, flexibility, etc.), making them difficult to apply in the field of adhesives. For adhesives intended for optical applications, there are also concerns about the reduction in optical properties caused by the incorporation of inorganic particles.

[0010] Therefore, an object of the present invention is to provide an adhesive that increases the refractive index through a method also suitable for optical applications. Another related object is to provide an adhesive composition capable of forming such an adhesive and an adhesive sheet comprising the adhesive.

[0011] Solution for solving the problem

[0012] The adhesive composition provided in this specification comprises: an acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit; and an additive (H). RO This is an organic material with a higher refractive index compared to the aforementioned acrylic polymer (A). The acrylic polymer (A), containing a monomer (m1) with an aromatic ring as a monomer unit, can be a material with a high refractive index. The adhesive composition disclosed herein further includes, in addition to the acrylic polymer (A), an organic material with a higher refractive index than the acrylic polymer (A), namely, an additive (H). RO This allows for a well-balanced combination of the aforementioned additive (H) RO The adhesive improves the refractive index and suppresses the decrease in adhesive properties. Furthermore, according to the above-mentioned additives (H... RO It can suppress the reduction of optical properties (such as transmittance, haze, etc.) and effectively improve the refractive index of the adhesive.

[0013] In some preferred embodiments of the technologies disclosed herein (including adhesive compositions, adhesives, adhesive sheets, and technologies implemented in other forms. The same applies hereinafter), the aforementioned additives (H...) RO The refractive index of (A) can be, for example, about 1.60 or higher. Based on organic materials with a refractive index higher than that of acrylic polymers (A) and a refractive index of about 1.60 or higher, namely additives (H)... RO This can effectively increase the refractive index of the adhesive.

[0014] In some methods, relative to 100 parts by weight of the acrylic polymer (A), the above-mentioned additive (H) RO The content of ( ) can be, for example, higher than 0 parts by weight and lower than 60 parts by weight. This content includes additives (H) RO The adhesive composition readily forms a well-balanced combination of the additive (H) RO The adhesive is preferred because it increases the refractive index and suppresses the reduction of adhesive properties and / or optical properties.

[0015] In some methods, the above-mentioned additives (H) RO The present invention comprises at least one compound selected from the group consisting of compounds containing aromatic rings and compounds containing heterocycles. The techniques disclosed herein are preferably used with the compound as an additive (H). RO Implemented in the manner of ).

[0016] In some methods, the above-mentioned additives (H) RO This refers to compounds containing two or more aromatic rings within a single molecule. The techniques disclosed herein are preferably used with this compound as an additive (H). RO The above-mentioned compounds having two or more aromatic rings within one molecule can be, for example, compounds that satisfy at least one of the following:

[0017] (i) A structure comprising two non-fused aromatic rings directly chemically bonded together; and

[0018] (ii) A structure consisting of two fused aromatic rings.

[0019] The technology disclosed herein is preferably used with this compound as an additive (H) RO Implemented in the manner of ).

[0020] In some embodiments, the content of the aromatic ring-containing monomer (m1) in the monomer component constituting the above-described acrylic polymer (A) is 50% by weight or more. The acrylic polymer (A) composed of this monomer component can be a material with a high refractive index, and is therefore suitable as the acrylic polymer (A) disclosed herein.

[0021] In some embodiments, the content of the aromatic ring-containing monomer (m1) in the monomer component constituting the above-mentioned acrylic polymer (A) is higher than 70% by weight and lower than 100% by weight. Such an acrylic polymer (A) is preferred because it readily increases the refractive index and readily forms adhesives with good bonding properties.

[0022] In some embodiments, at least 50% by weight of the aromatic ring-containing monomer (m1) in the monomer composition constituting the aforementioned acrylic polymer (A) may be a monomer with a glass transition temperature of 10°C or lower than that of the homopolymer. Therefore, even with an increased content of the aromatic ring-containing monomer (m1) in the monomer composition, it is easy to form an adhesive that achieves a good balance between high refractive index and adhesive properties. It should be noted that the Tg of the homopolymer of the monomer is sometimes referred to as the Tg of the monomer itself.

[0023] In some preferred embodiments, the aromatic ring-containing monomer (m1) described above comprises aromatic ring-containing monomers having two or more aromatic rings within one molecule (hereinafter also referred to as "monomers containing multiple aromatic rings"). By using monomers containing multiple aromatic rings, the refractive index of the adhesive can be effectively increased. The aromatic ring-containing monomer (m1) may contain only one type of monomer containing multiple aromatic rings (e.g., a monomer containing multiple aromatic rings with a Tg below 10°C for homopolymers), or it may combine two or more types of monomers containing multiple aromatic rings.

[0024] In some preferred embodiments, the monomers having two or more aromatic rings within one molecule include monomers having a structural portion consisting of two aromatic rings bonded together by a linking group. Monomers containing multiple aromatic rings with such a structural portion tend to have a lower Tg in homopolymers compared to monomers containing multiple aromatic rings with a structural portion consisting of, for example, two aromatic rings directly chemically bonded together (e.g., a biphenyl structure). According to the aromatic ring monomer (m1) containing this structure, a better balance can be struck between flexibility suitable for use as an adhesive and a high refractive index.

[0025] In some embodiments, the monomer components constituting the aforementioned acrylic polymer (A) may further contain monomers (m2) having at least one of hydroxyl and carboxyl groups, in addition to the aromatic ring-containing monomer (m1). The acrylic polymer (A) composed of these monomer components readily forms an adhesive with good bonding properties.

[0026] It should be noted that, in the following text, monomers containing aromatic rings (m1) are sometimes referred to as "monomers (m1)", and monomers having at least one of hydroxyl and carboxyl groups (m2) are sometimes referred to as "monomers (m2)".

[0027] The adhesive compositions disclosed herein may further include a crosslinking agent. By using a crosslinking agent to impart appropriate cohesiveness to the adhesive, the processability of the adhesive sheet during manufacturing, processing, storage, and adhesion to substrates can be improved.

[0028] According to this specification, an adhesive is provided that is formed from any of the adhesive compositions disclosed herein. This adhesive is formed by further comprising the aforementioned additive (H) based on the aforementioned acrylic polymer (A). RO This allows for the suppression of degradation of adhesive properties and / or optical properties and the improvement of refractive index. In a preferred embodiment, the refractive index of the adhesive may be, for example, higher than 1.570 (preferably 1.575 or higher, more preferably 1.580 or higher).

[0029] According to this specification, an adhesive sheet is provided comprising an adhesive layer made of an adhesive (e.g., an adhesive with a refractive index higher than 1.570, preferably 1.575 or higher, more preferably 1.580 or higher), said adhesive being formed from any of the adhesive compositions disclosed herein. This adhesive sheet can preferably be used in a manner that adheres to a component (e.g., an optical component).

[0030] In some embodiments of the adhesive sheet disclosed herein, the haze value of the adhesive layer is 1.0% or less. Such adhesive sheets with highly transparent adhesive layers are, for example, preferably used in the optical field.

[0031] It should be noted that a technical solution formed by appropriately combining the various elements described in this specification may also be included within the scope of protection claimed in this patent application. Attached Figure Description

[0032] Figure 1 A cross-sectional view illustrating the structure of an adhesive sheet according to one embodiment is shown for illustrative purposes.

[0033] Figure 2 A cross-sectional view illustrating the structure of an adhesive sheet according to another embodiment is shown for illustrative purposes.

[0034] Figure 3 A cross-sectional view of an optical component with an adhesive sheet of one embodiment is shown schematically. Detailed Implementation

[0035] The following describes suitable embodiments of the present invention. For matters necessary for carrying out the present invention, other than those specifically mentioned in this specification, those skilled in the art can understand them based on the teachings on carrying out the invention described in this specification and common general knowledge at the time of application. The present invention can be implemented based on the disclosures in this specification and common general knowledge in the art.

[0036] It should be noted that in the following figures, components / parts that perform the same function are sometimes given the same reference numerals for description, and repeated descriptions are sometimes omitted or simplified. Furthermore, the embodiments described in the figures are schematic for the purpose of clearly illustrating the invention and do not necessarily accurately represent the dimensions or scale of the actual product provided.

[0037] In this specification, a self-emissive element refers to a light-emitting element whose brightness can be controlled by the value of the current flowing through it. A self-emissive element can be a single unit or an assembly. Specific examples of self-emissive elements include, but are not limited to, light-emitting diodes (LEDs) and organic ELs. When a light-emitting device is mentioned in this specification, the light-emitting device may include such a self-emissive element as a constituent element. Examples of the aforementioned light-emitting devices include light source module devices (e.g., planar light-emitting modules) used for illumination, and display devices that form pixels, but are not limited to them.

[0038] In this specification, the term "base polymer" in the adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not interpreted in any other limiting way. The aforementioned rubbery polymer refers to a polymer that exhibits rubber-like elasticity in a temperature range near room temperature. Furthermore, in this specification, "main component" refers to a component contained in greater than 50% by weight unless otherwise specified.

[0039] In this specification, "acrylic polymer" refers to a polymer comprising monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as an "acrylic monomer". Therefore, in this specification, an acrylic polymer is defined as a polymer comprising monomer units derived from acrylic monomers. Typical examples of acrylic polymers include polymers in which the proportion of acrylic monomers in all monomers used in the synthesis of the polymer is greater than 50% by weight (preferably greater than 70% by weight, for example greater than 90% by weight).

[0040] Furthermore, in this specification, "(meth)acryloyl" is a general term for both acryloyl and methacryloyl groups. Similarly, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acrylic acid" is a general term for both acrylic acid and methacrylic acid. Therefore, the concept of acrylic monomers as used herein can include both monomers having an acryloyl group (acrylic monomers) and monomers having a methacryloyl group (methacrylic monomers).

[0041] <Adhesive Composition>

[0042] The adhesive composition disclosed herein is any composition capable of forming an adhesive containing an acrylic polymer (A) (preferably an adhesive containing an acrylic polymer (A) as a base polymer), and its form is not particularly limited. The aforementioned adhesive composition may, for example, take various forms such as: a solvent-based adhesive composition containing an adhesive-forming component in an organic solvent; an active energy ray-cured adhesive composition prepared by curing with active energy rays such as ultraviolet light or radiation to form an adhesive; a water-dispersible adhesive composition in which an adhesive-forming component is dispersed in water; and a hot-melt adhesive composition, etc., formed by coating in a molten state upon heating and cooling to near room temperature.

[0043] (Acrylic polymer (A))

[0044] The adhesive composition disclosed herein contains an acrylic polymer (A), which contains 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 monomeric component constituting the acrylic polymer. Here, in this specification, "monomeric component constituting the acrylic polymer" refers to the monomer that constitutes the repeating unit of the acrylic polymer in the adhesive formed from the adhesive composition, whether contained in the adhesive composition in the form of a pre-formed polymer (which may be an oligomer) or in the form of an unpolymerized monomer. That is, the monomeric component constituting the acrylic polymer can be contained in the adhesive composition in any of the following forms: polymer, unpolymerized, or partially polymerized. From the viewpoint of ease of preparation of the adhesive composition, in some embodiments, it is preferable to have an adhesive composition containing substantially all (e.g., 95% by weight or more, preferably 99% by weight or more) of the monomeric component in polymer form. An adhesive composition containing substantially all of the monomeric component in polymer form is also preferred from the viewpoint of easily forming adhesive sheets with less deformation and warping.

[0045] (Single(m1))

[0046] As a monomer (m1), a compound containing at least one aromatic ring and at least one olefinic unsaturated group is used in one molecule. As a monomer (m1), one of the compounds may be used alone or in combination of two or more.

[0047] Examples of the aforementioned olefin unsaturated groups include (meth)acryloyl, vinyl, and (meth)allyl. From the viewpoint of polymerization reactivity, (meth)acryloyl is preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl is more preferred. From the viewpoint of suppressing the reduction of the adhesive's flexibility, as a monomer (m1), it is preferable to use a compound that contains one olefin unsaturated group per molecule (i.e., a monofunctional monomer).

[0048] The number of aromatic rings contained in one molecule of the compound used as a monomer (m1) can be one or more. There is no particular upper limit to the number of aromatic rings contained in the monomer (m1), for example, it can be 16 or less. In some embodiments, from the viewpoint of ease of preparation of acrylic polymer (A) and transparency of adhesive, the number of aromatic rings can be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less.

[0049] The aromatic ring of the compound used as a monomer (m1) can be, for example, a benzene ring (which can be a benzene ring that forms part of a biphenyl or fluorene structure); a fused ring of a naphthalene ring, indene ring, azulene ring, anthracene ring, or phenanthrene ring; a carbocyclic ring, which can be, for example, a pyridine ring, pyrimidine ring, pyridazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, or thiophene ring; or a heterocyclic ring. The heteroatoms included as cyclizing atoms in the above-mentioned heterocyclic rings can be, for example, one or more types selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatoms constituting the above-mentioned heterocyclic rings can be one or both of nitrogen and sulfur. The monomer (m1) can also have, for example, a structure such as a dinaphthothiophene structure, formed by the fusion of one or more carbocyclic rings with one or more heterocyclic rings.

[0050] The aromatic ring (preferably a carbocyclic ring) may have one or more substituents on the cyclic atom, or it may not have any substituents. When substituents are present, examples of such substituents include alkyl, alkoxy, aryloxy, hydroxy, halogen atoms (fluorine, chlorine, bromine, etc.), hydroxyalkyl, hydroxyalkyloxy, epoxypropoxy, etc., but it is not limited to these. Among the substituents containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. In some embodiments, the aromatic ring may be an aromatic ring that does not have substituents on the cyclic atom, or has one or more substituents selected from the group consisting of alkyl, alkoxy, and halogen atoms (e.g., bromine atoms). It should be noted that the aromatic ring of the monomer (m1) having substituents on its cyclic atom means that the aromatic ring has substituents other than those containing olefinic unsaturated groups.

[0051] The aromatic ring and the olefinic unsaturated group can be directly bonded or bonded via a linking group. The linking group can be, for example, a group containing one or more structures selected from alkylene, oxoalkylene, poly(oxoalkylene), phenyl, alkylphenyl, alkoxyphenyl, or groups in which one or more hydrogen atoms are replaced by hydroxyl groups (e.g., hydroxyalkylene), oxy (-O-), thiooxy (-S-), etc. In some embodiments, it is preferable to use a monomer containing an aromatic ring, either directly bonded to the olefinic unsaturated group or bonded via a linking group selected from the group consisting of alkylene, oxoalkylene, and poly(oxoalkylene). The number of carbon atoms in the alkylene and oxoalkylene groups is preferably 1 to 4, more preferably 1 to 3, for example, 1 or 2. The number of repetitions of the oxoalkylene unit in the poly(oxoalkylene) group can be, for example, 2 to 3.

[0052] Examples of compounds that can be preferably used as monomers (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. One aromatic ring-containing (meth)acrylate and one aromatic ring-containing vinyl compound can be used alone or in combination of two or more. Alternatively, one or more aromatic ring-containing (meth)acrylates can be used in combination with one or more aromatic ring-containing vinyl compounds.

[0053] The content of monomer (m1) in the monomer component constituting the acrylic polymer (A) is not particularly limited and can be set in a way that achieves an adhesive layer that balances desired refractive index and adhesive properties (e.g., peel strength, flexibility) and / or optical properties (e.g., total light transmittance, haze value, etc.). In some embodiments, the content of monomer (m1) in the aforementioned monomer component can be, for example, 30% by weight or more, preferably 50% by weight or more, 60% by weight or more, or 70% by weight or more. From the viewpoint of easily obtaining a higher refractive index, in some preferred embodiments, the content of monomer (m1) is, for example, higher than 70% by weight, such as 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The upper limit for the content of monomer (m1) in the aforementioned monomer component is 100% by weight. From the viewpoint of achieving a good balance between high refractive index and adhesive and / or optical properties, it is advantageous to set the content of the aforementioned monomer (m1) to be less than 100% by weight, for example preferably about 99% by weight or less, more preferably 98% by weight or less, and can be 97% by weight or less, or 96% by weight or less. In some embodiments, the content of the aforementioned monomer (m1) can 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 where adhesive and / or optical properties are given greater emphasis, the content of the aforementioned monomer (m1) in the aforementioned monomer composition can be 70% by weight or less, 60% by weight or less, or 45% by weight or less.

[0054] In some embodiments of the technology disclosed herein, monomers (m1) that readily achieve high refractive index are preferably selected from the perspective of easily obtaining high refractive index effects. Examples of monomers having two or more aromatic rings per molecule (hereinafter also referred to as "monomers containing multiple aromatic rings") include: monomers having a structure in which two or more non-fused aromatic rings are bonded together by a linking group; monomers having a structure in which two or more non-fused aromatic rings are directly (i.e., without the aid of other atoms) chemically bonded together; monomers having a fused aromatic ring structure; monomers having a fluorene structure; monomers having a dinaphthothiophene structure; and monomers having a dibenzothiophene structure. Monomers containing multiple aromatic rings can be used alone or in combination of two or more.

[0055] The linking group mentioned above can be, for example, an oxygen group (-O-), a thiooxy group (-S-), or an oxoalkylene group (e.g., -O-(CH2)). n - group, where n is 1 to 3, preferably 1), thiooxyalkylene (e.g., -S-(CH2) n - group, where n is 1 to 3, preferably 1), straight-chain alkylene (i.e., -(CH2)).n - group (where n is 1 to 6, preferably 1 to 3), or groups formed by partially or completely halogenating the alkylene oxides, thioalkylene oxides, and straight-chain alkylene oxides mentioned above. From the viewpoint of adhesive flexibility, suitable examples of the above-mentioned linking groups include oxy groups, thiooxy groups, alkylene oxides, and straight-chain alkylene oxides. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded together by a linking group include (meth)acrylate phenoxybenzyl ester (e.g., (meth)acrylate m-phenoxybenzyl ester), (meth)acrylate thiophenoxybenzyl ester, (meth)acrylate benzyl benzyl ester, etc.

[0056] The monomers described above, which have structures formed by the direct chemical bonding of two or more non-fused aromatic rings, can be, for example, (meth)acrylates containing a biphenyl structure, (meth)acrylates containing a triphenyl structure, or vinyl-containing biphenyls. Specific examples include o-phenylphenol (meth)acrylate and biphenyl methyl methacrylate.

[0057] Examples of monomers with fused aromatic ring structures include (meth)acrylates containing a naphthyl ring, (meth)acrylates containing anthracene ring, vinyl-containing naphthalene, and vinyl-containing anthracene. Specific examples include 1-naphthyl methyl (meth)acrylate (also known as 1-naphthyl methyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthyl ethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0058] Specific examples of monomers with the aforementioned fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene(meth)acrylate. It should be noted that monomers with the fluorene structure comprise a structural portion formed by the direct chemical bonding of two benzene rings, and are therefore included in the concept of monomers with structures formed by the direct chemical bonding of two or more non-fused aromatic rings.

[0059] Examples of monomers having the dinaphthothiophene structure include dinaphthothiophenes containing (meth)acryloyl groups, dinaphthothiophenes containing vinyl groups, and dinaphthothiophenes containing (meth)allyl groups. Specific examples include (meth)acryloyloxymethyl dinaphthothiophene (e.g., with CH2CH(R) bonded at the 5 or 6 position of the dinaphthothiophene ring). 1 Compounds with the structure )C(O)OCH2-. Here, R 1 It consists of a hydrogen atom or a methyl group. ), (meth)acryloyloxyethyl dinaphthothiophene (for example, CH2CH(R) bonded at the 5 or 6 position of the dinaphthothiophene ring). 1)C(O)OCH(CH3)- or CH2CH(R 1 Compounds with the structure )C(O)OCH2CH2-. Here, R 1 These include monomers with hydrogen atoms or methyl groups, vinyl dinaphthothiophene (e.g., compounds with a vinyl group bonded to the 5th or 6th position of the dinaphthothiophene ring), (methyl)allyloxy dinaphthothiophene, etc. It should be noted that monomers with a dinaphthothiophene structure are included in the concept of monomers with fused aromatic ring structures because they contain a naphthalene structure and also because they have a structure formed by the fusion of a thiophene ring and two naphthalene structures.

[0060] Examples of monomers having the above-mentioned dibenzothiophene structure include dibenzothiophene containing (meth)acryloyl groups and dibenzothiophene containing vinyl groups. It should be noted that monomers having the dibenzothiophene structure are included in the concept of monomers having fused aromatic ring structures because they have a structure formed by the fusion of a thiophene ring and two benzene rings.

[0061] It should be noted that neither dinaphthothiophene nor dibenzothiophene structures belong to structures formed by the direct chemical bonding of two or more non-fused aromatic rings.

[0062] As the monomer (m1) disclosed herein, a monomer having one aromatic ring (preferably a carbocyclic ring) per molecule can also be used. A monomer having one aromatic ring per molecule can, for example, contribute to improving the flexibility of the adhesive, adjusting its adhesive properties, and improving its transparency. In some embodiments, from the viewpoint of increasing the refractive index of the adhesive, a monomer having one aromatic ring per molecule is preferably used in combination with a monomer containing multiple aromatic rings.

[0063] Examples of monomers having one aromatic ring in one molecule include benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and benzyl chloro (meth)acrylate, all containing a carbon-containing aromatic ring; 2-(4,6-dibromo-2-sec-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, and so on. (Meth)acrylates containing bromine-substituted aromatic rings, such as 6-(4,6-dibromo-2-sec-butylphenoxy)hexyl acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl acrylate, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; vinyl compounds containing carbon aromatic rings, such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; compounds with vinyl substituents on heteroaromatic rings, such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazolium, and N-vinyloxazole; etc.

[0064] As monomer (m1), monomers with an oxyethylidene chain sandwiched between the olefinic unsaturated group and the aromatic ring in the various aromatic ring-containing monomers described above can also be used. Such monomers with an oxyethylidene chain sandwiched between the olefinic unsaturated group and the aromatic ring can be considered as ethoxylated derivatives of the original monomer. The repeating number of the oxyethylidene unit (-CH2CH2O-) in the aforementioned oxyethylidene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, and for example, 1. Specific examples of ethoxylated aromatic ring-containing monomers include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol di(meth)acrylate.

[0065] The content of monomers containing multiple aromatic rings in monomer (m1) is not particularly limited, and can be, for example, 5% or more by weight, 25% or more by weight, or 40% or more by weight. In some embodiments, from the viewpoint of easily achieving an adhesive with a higher refractive index, the content of monomers containing multiple aromatic rings in monomer (m1) can be, for example, 50% or more by weight, preferably 70% or more by weight, 85% or more by weight, 90% or more by weight, or 95% or more by weight. It is also possible for monomer (m1) to be substantially 100% by weight of monomers containing multiple aromatic rings. That is, as monomer (m1), only one or two or more monomers containing multiple aromatic rings can be used. In addition, in some embodiments, for example, considering the balance between high refractive index and adhesive properties and / or optical properties, the content of monomers containing multiple aromatic rings in monomer (m1) can be less than 100% by weight, and can be 98% or less by weight, 90% or less by weight, 80% or less by weight, or 65% or less by weight. In some embodiments, considering adhesive and / or optical properties, the content of monomers containing multiple aromatic rings in the monomer (m1) may be less than 70% by weight, less than 50% by weight, less than 25% by weight, or less than 10% by weight. The techniques disclosed herein can also be implemented with the content of monomers containing multiple aromatic rings in the monomer (m1) being less than 5% by weight. Alternatively, monomers containing multiple aromatic rings may not be used.

[0066] The content of monomers containing multiple aromatic rings in the monomer component constituting the acrylic polymer (A) is not particularly limited, and can be set in a way that can achieve an adhesive layer that balances desired refractive index and adhesive properties (e.g., peel strength, flexibility) and / or optical properties (e.g., total light transmittance, haze value, etc.). The content of monomers containing multiple aromatic rings in the aforementioned monomer component can, for example, be 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of easily achieving an adhesive with a higher refractive index, the content of monomers containing multiple aromatic rings in the aforementioned monomer component can, for example, be higher than 35% by weight, preferably higher than 50% by weight, higher 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 monomers containing multiple aromatic rings in the above-mentioned monomer components can be 100% by weight, but from the viewpoint of achieving a good balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, and can be 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, or 75% by weight or less. In some embodiments, considering adhesive properties and / or optical properties, the content of monomers containing multiple aromatic rings in the above-mentioned monomer components can 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 or less. The technology disclosed herein can also be implemented with the content of monomers containing multiple aromatic rings in the above-mentioned monomer components being less than 3% by weight.

[0067] In some embodiments of the technology disclosed herein, a high-refractive-index monomer may preferably be used as at least a portion of the monomer (m1). Here, "high-refractive-index monomer" refers to a monomer with a refractive index of, for example, about 1.510 or more, preferably about 1.530 or more, and more preferably about 1.550 or more. There is no particular upper limit to the refractive index of the high-refractive-index monomer; from the viewpoint of balancing ease of preparation of the adhesive composition with ease of achieving suitable flexibility as an adhesive, it may be, for example, 3.000 or less, 2.500 or less, 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less. One high-refractive-index monomer may be used alone or in combination of two or more.

[0068] It should be noted that the refractive index of the monomer was measured using an Abbe refractometer at a measurement wavelength of 589 nm and a measurement temperature of 25°C. The Abbe refractometer can be the ATAGO "DR-M4" model or its equivalent. If the manufacturer provides a nominal value for the refractive index at 25°C, that value can be used.

[0069] As the aforementioned high refractive index monomer, a substance with a suitable refractive index can be appropriately selected from the compounds included in the concept of aromatic ring-containing monomers (m1) disclosed herein (e.g., the compounds and groups of compounds exemplified above). Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthyl methyl acrylate (refractive index: 1.595, Tg of homopolymer: 31°C), ethoxylated o-phenylphenol acrylate (repetition number of oxyethylidene unit: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6°C), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2°C), and phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35°C). g: -35℃), 6-acryloyloxymethyl dinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacryloyloxymethyl dinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyl dinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyl dinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyl dinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyl dinaphthothiophene (abbreviated as: 5VDNT, refractive index: 1.793), etc., but not limited to these.

[0070] The content of high-refractive-index monomers (i.e., aromatic ring-containing monomers with a refractive index of about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more) in monomer (m1) is not particularly limited, and can be, for example, 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some embodiments, from the viewpoint of easily obtaining higher refractive indices, the content of high-refractive-index monomers in monomer (m1) can be, for example, 50% by weight or more, preferably 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. It is also possible for monomer (m1) to be substantially 100% by weight of high-refractive-index monomers. In addition, in some embodiments, for example, from the viewpoint of achieving a good balance between high refractive index and adhesive properties and / or optical properties, the content of high-refractive-index monomers in monomer (m1) can be less than 100% by weight, and can be 98% by weight or less, 90% by weight or less, 80% by weight or less, or 65% by weight or less. In some embodiments, considering adhesive and / or optical properties, the content of the high-refractive-index monomer in the monomer (m1) may be less than 70% by weight, less than 50% by weight, less than 25% by weight, less than 15% by weight, or less than 10% by weight. The techniques disclosed herein can also be implemented with the content of the high-refractive-index monomer in the monomer component (m1) being less than 5% by weight. Alternatively, the high-refractive-index monomer may not be used.

[0071] The content of high-refractive-index monomers in the monomer components constituting the acrylic polymer (A) is not particularly limited, and can be set in a way that achieves an adhesive layer that balances desired refractive index with adhesive properties (e.g., peel strength, flexibility) and / or optical properties (e.g., total light transmittance, haze value, etc.). The content of high-refractive-index monomers in the aforementioned monomer components can, for example, be 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of easily achieving an adhesive with a higher refractive index, the content of high-refractive-index monomers in the aforementioned monomer components can, for example, be higher than 35% by weight, preferably higher than 50% by weight, higher than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The content of the high-refractive-index monomer in the above-mentioned monomer composition can be 100% by weight, but from the viewpoint of achieving a good balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, preferably 99% by weight or less, more preferably 98% by weight or less, and can be 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, or 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 above-mentioned monomer composition can 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 or less. The technology disclosed herein can also be implemented with the content of the high-refractive-index monomer in the above-mentioned monomer composition being less than 3% by weight.

[0072] In some preferred embodiments of the technology disclosed herein, a monomer containing aromatic rings (hereinafter sometimes referred to as "monomer L") with a Tg of less than 10°C (preferably less than 5°C or less than 0°C, more preferably less than -10°C, further preferably less than -20°C, for example less than -25°C) is used as at least a portion of monomer (m1). If the content of the aromatic ring-containing monomer (m1) in the monomer composition is increased (particularly the aromatic ring-containing monomer (m1) equivalent to one or both of the aforementioned monomers containing multiple aromatic rings and high refractive index monomers), the storage modulus G' of the adhesive generally tends to increase. By using monomer L as part or all of the monomer (m1), the increase in storage modulus G' can be suppressed. Thus, the flexibility suitable for use as an adhesive can be maintained better, and the refractive index can be increased. There is no particular limitation on the lower limit of the Tg of monomer L. Considering the balance with the effect of increasing the refractive index, in some embodiments, the Tg of monomer L can be, for example, greater than -70°C, greater than -55°C, or greater than -45°C. Monomer L can be used alone or in combination of two or more types.

[0073] As monomer L, a substance having a suitable Tg can be appropriately selected from the compounds included in the concept of aromatic ring-containing monomers (m1) disclosed herein (e.g., the compounds and groups of compounds exemplified above). As a suitable example of an aromatic ring-containing monomer that can be used as monomer L, m-phenoxybenzyl acrylate (Tg of homopolymer: -35°C) is listed. As another suitable example, phenoxydiethylene glycol acrylate (Tg of homopolymer: -35°C) is listed.

[0074] The content of monomer L in monomer (m1) is not particularly limited; for example, it can be 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, from the viewpoint of easily obtaining an adhesive that balances high refractive index and flexibility at a higher level, the content of monomer L in monomer (m1) can be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. It is also possible for monomer (A1) to be substantially 100% by weight of monomer L. Furthermore, in some embodiments, for example, from the viewpoint of achieving a good balance between flexibility and high refractive index suitable as an adhesive, the content of monomer L in monomer (m1) can be less than 100% by weight, less than 98% by weight, less than 90% by weight, less than 80% by weight, less than 70% by weight, less than 50% by weight, less than 25% by weight, or less than 10% by weight. The techniques disclosed herein can also be implemented with the monomer L content in the monomer (m1) being less than 5% by weight. Alternatively, monomer L can be omitted.

[0075] The content of monomer L in the monomer component constituting the acrylic polymer (A) can 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 easily obtaining an adhesive that balances high refractive index and flexibility at a higher level, the content of monomer L in the monomer component can be, for example, higher than 35% by weight, preferably higher than 50% by weight, higher 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 monomer L in the above-mentioned monomer component can be 100% by weight, but considering the balance between high refractive index and adhesive properties and / or optical properties, it is advantageous to set it to less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, 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% by weight or less, or 75% by weight or less. In some embodiments, the content of monomer L in the aforementioned monomeric components may be less than 70% by weight, less than 50% by weight, less than 25% by weight, less than 15% by weight, or less than 5% by weight. The techniques disclosed herein may also be implemented with the content of monomer L in the aforementioned monomeric components being less than 3% by weight.

[0076] In some approaches, from the viewpoint of adhesive flexibility, the glass transition temperature Tg of the monomer (m1) composition is considered. m1 It is advantageous to have a temperature below approximately 20°C, preferably below 10°C (e.g., below 5°C), more preferably below 0°C, and even more preferably below -10°C. It can be below -20°C or below -25°C. Glass transition temperature Tg m1 There is no particular lower limit. Considering the balance with the effect of increasing the refractive index, in some approaches, the glass transition temperature Tg... m1 For example, it can be above -70°C, above -55°C, or above -45°C. The technology disclosed herein can also be based on the glass transition temperature Tg. m1 It shall be implemented in a manner suitable for temperatures above -40°C, -35°C, -33°C, -30°C, or -25°C.

[0077] Here, the glass transition temperature Tg is based on the composition of the monomer (m1). m1 This refers to the glass transition temperature (Tg) calculated using the Fox equation (described later), based solely on the composition of the monomers (m1) constituting the acrylic polymer (A). m1The glass transition temperature (Tg) of the homopolymer of the acrylic polymer (A) can be calculated using only the monomer (m1) as the monomer component, and by applying the Fox formula (described later), based on the glass transition temperature of the homopolymer of each aromatic ring-containing monomer used as monomer (m1) and the weight fraction of each aromatic ring-containing monomer in the total amount of monomer (m1). In the case where only one monomer is used as monomer (m1), the glass transition temperature (Tg) of the homopolymer of that monomer is related to its glass transition temperature (Tg). m1 Consistent.

[0078] In some methods, monomer L (i.e., a monomer containing an aromatic ring with a Tg of 10°C or less, preferably 5°C or less or 0°C, more preferably -10°C or less, further preferably -20°C or less, for example -25°C or less) and monomer H with a Tg higher than 10°C can be used as the aromatic ring-containing monomer (m1). The Tg of monomer H can be, for example, higher than 10°C, higher than 15°C, or higher than 20°C. By using monomer L and monomer H in combination, for example in a composition where the content of the aromatic ring-containing monomer (m1) in the monomer composition is relatively high, it is possible to achieve a higher level of balance between the high refractive index and flexibility of the adhesive. The ratio of monomer L to monomer H can be set in a way that suitably manifests this effect and is not particularly limited. For example, it is preferable to satisfy any of the above-mentioned glass transition temperatures Tg. m1 The ratio of monomer L to monomer H is set in a certain way.

[0079] In some embodiments, the aromatic ring-containing monomer (m1) is preferably selected from compounds that do not contain a structure formed by direct chemical bonding of two or more non-fused aromatic rings (e.g., a biphenyl structure). For example, acrylic polymers composed of monomer components having a content of less than 5% by weight (more preferably less than 3% by weight, or even 0% by weight) of compounds containing a structure formed by direct chemical bonding of two or more non-fused aromatic rings are preferred. From the viewpoint of achieving a good balance between flexibility, adhesion, and high refractive index in adhesives, thus limiting the amount of compounds containing a structure formed by direct chemical bonding of two or more non-fused aromatic rings can be advantageous.

[0080] (Single (m2))

[0081] In some embodiments of the technology disclosed herein, the monomer component constituting the acrylic polymer (A) may further contain monomer (m2) in addition to the aforementioned monomer (m1). The monomer (m2) is a monomer belonging to at least one of a hydroxyl-containing monomer (hydroxyl-containing monomer) and a carboxyl-containing monomer (carboxyl-containing monomer). The hydroxyl-containing monomer is a compound having at least one hydroxyl group and at least one olefinically unsaturated group per molecule. The carboxyl-containing monomer is a compound containing at least one carboxyl group and at least one olefinically unsaturated group per molecule. Monomer (m2) can facilitate the introduction of crosslinking points into the acrylic polymer (A) or impart appropriate cohesiveness to the adhesive. Monomer (m2) can be used alone or in combination of two or more. Monomer (m2) is typically a monomer that does not contain an aromatic ring.

[0082] Examples of olefinic unsaturated groups present in monomer (m2) include (meth)acryloyl, vinyl, and (meth)allyl groups. From the viewpoint of polymerization reactivity, (meth)acryloyl is preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl is more preferred. From the viewpoint of suppressing the reduction of the adhesive's flexibility, it is preferable to use a compound (i.e., a monofunctional monomer) containing one olefinic unsaturated group per molecule as monomer (m2).

[0083] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, and methyl methacrylate (4-hydroxymethylcyclohexyl)methacrylate, but are not limited to these. Examples of preferred hydroxyl-containing monomers include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl methacrylate (Tg: -15°C). From the viewpoint of improved softness in the room temperature range, 4-hydroxybutyl acrylate with a lower Tg is more preferred. In a preferred embodiment, 4-hydroxybutyl acrylate may be present in a monomer concentration of 50% by weight or more (e.g., more than 50% by weight, more than 70% by weight, or more than 85% by weight). One hydroxyl-containing monomer may be used alone or in combination of two or more.

[0084] In some methods of using hydroxyl-containing monomers as monomers (m2), the hydroxyl-containing monomers may be one or more selected from compounds without a methacryloyl group. Suitable examples of hydroxyl-containing monomers without a methacryloyl group include the various hydroxyalkyl acrylates mentioned above. For example, it is preferable that more than 50%, more than 70%, or more than 85% by weight of the hydroxyl-containing monomers used as monomers (m2) are hydroxyalkyl acrylates. By using hydroxyalkyl acrylates, hydroxyl groups that help provide crosslinking points and impart moderate cohesiveness can be introduced into the acrylic polymer (A), and adhesives with good flexibility and adhesion in the room temperature range are readily obtained compared to the case where only the corresponding hydroxyalkyl methacrylate is used.

[0085] Examples of carboxyl-containing monomers include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylic acid, and carboxypentyl (meth)acrylic acid, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid, but are not limited to these. Examples of preferred carboxyl-containing monomers include acrylic acid and methacrylic acid. One type of carboxyl-containing monomer can be used alone, or two or more can be used in combination. Hydroxyl-containing monomers and carboxyl-containing monomers can also be used in combination.

[0086] The content of 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) can 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 performance effect, in some embodiments, the content of the monomer (A2) is preferably set to 1% by weight or more, can be set to 2% by weight or more, or can be set to 4% by weight or more. The upper limit of the content of monomer (m2) in the monomer component is set such that the total content with the content of monomer (m1) does not exceed 100% by weight. In some embodiments, it is appropriate to set the content of the monomer (m2) to 30% by weight or less or 25% by weight or less, for example. From the viewpoint of making it easier to increase the refractive index by relatively increasing the content of monomer (m1), it is preferably set to 20% by weight or less, more preferably to 15% by weight or less, and can be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

[0087] In methods using hydroxyl-containing monomers as monomers (m2), the content of hydroxyl-containing monomers in the monomer composition is not particularly limited, and can be, 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 methods, the content of the hydroxyl-containing monomers is preferably set to 1% by weight or more of the monomer composition, and can be set to 2% by weight or more, or 4% by weight or more. The upper limit of the content of hydroxyl-containing monomers in the monomer composition is set such that the total content with the monomer (m1) 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. From the viewpoint of making it easier to increase the refractive index by relatively increasing the content of monomer (m1), it is preferably set to 20% by weight or less, more preferably 15% by weight or less, and can be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

[0088] In methods using carboxyl-containing monomers as monomers (m2), the content of carboxyl-containing monomers in the monomer composition is not particularly limited, and can be, for example, 0.01% by weight or more (preferably 0.1% by weight or more, more preferably 0.3% by weight or more). In some methods, the content of the carboxyl-containing monomers can be set to 1% by weight or more, 2% by weight or more, or 4% by weight or more. The upper limit of the content of carboxyl-containing monomers in the monomer composition is set such that the total amount used with the monomer (m1) does not exceed 100% by weight. For example, it is appropriate to set it to 30% by weight or less or 25% by weight or less. From the viewpoint of making it easier to increase the refractive index by relatively increasing the content of monomer (m1), it is preferable to set it to 20% by weight or less, more preferably 15% by weight or less, and can be less than 12% by weight or less than 10% by weight. In some methods, from the viewpoint of improving the flexibility of the adhesive, it is advantageous to set the content of the carboxyl-containing monomers to less than 7% by weight, preferably less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. The techniques disclosed herein can be preferably implemented, for example, by using only hydroxyl-containing monomers as monomers (m2), i.e., without using carboxyl-containing monomers.

[0089] The total content of monomers (m1) and (m2) in the monomer component constituting the acrylic polymer (A) can be, for example, 31% by weight or more, preferably 51% by weight or more, 61% by weight or more, or 71% by weight or more. In some embodiments, from the viewpoint of easily and appropriately exerting the effects of these monomers, the total content of monomers (m1) and (m2) in the monomer component constituting the acrylic polymer (A) can be, for example, 76% by weight or more, preferably 81% by weight or more, 86% by weight or more, 91% by weight or more, 96% by weight or more, 99% by weight or more, or substantially 100% by weight.

[0090] (Single m3)

[0091] The monomer components constituting the acrylic polymer (A) may, as needed, include monomers other than those described above (m1) and (m2). As an example of such an arbitrary component, alkyl (meth)acrylate (hereinafter also referred to as "monomer (m3)") can be listed. Monomer (m3) can help adjust the softness of the adhesive and improve its compatibility.

[0092] As a monomer (m3), it is preferable to use one having 1 to 20 carbon atoms at the ester terminus (i.e., C3). 1-20 Alkyl (meth)acrylates with straight or branched alkyl groups. As (meth)acrylate C 1-20 Specific examples of alkyl esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, and nonyl methacrylate. Isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, stearyl methacrylate, isostearyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc., but not limited to these.

[0093] In some methods, it is preferable to use alkyl (meth)acrylates with a Tg of -20°C or lower (more preferably -40°C or lower, for example -50°C or lower) as at least a portion of the monomer (m3). Such low-Tg alkyl (meth)acrylates can help improve the flexibility of the adhesive. There is no particular limitation on the lower limit of the Tg of the aforementioned alkyl (meth)acrylates; for example, it can be above -85°C, above -75°C, above -65°C, or above -60°C. Specific examples of the aforementioned low-Tg alkyl (meth)acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and isononyl acrylate (iNA).

[0094] In some methods of using monomer (m3), from the viewpoint of flexibility, adhesion, etc., it is preferable that at least a portion of the monomer (m3) is an alkyl acrylate. For example, it is preferable that 50% by weight or more (more preferably 75% by weight or more, and even more preferably 90% by weight or more) of the monomer (m3) is an alkyl acrylate. It is also possible to use only one or two or more alkyl acrylates as monomer (m3) without using alkyl methacrylates.

[0095] In monomer components comprising alkyl (meth)acrylates, the content of alkyl (meth)acrylates in the monomer component can be set in a manner that appropriately exerts its effect. In some methods, the content of the aforementioned alkyl (meth)acrylate can 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 methods, the content of the aforementioned alkyl (meth)acrylate can be 15% by weight or more, 30% by weight or more, or 45% by weight or more. The upper limit of the content of monomer (m3) in the monomer component is set such that the total content with the content of other monomers does not exceed 100% by weight, for example, it can be less than 50% by weight. In some methods, the content of the aforementioned monomer (m3) can be, for example, less than 35% by weight. Generally, alkyl (meth)acrylates have a low refractive index; therefore, in order to achieve a high refractive index, it is advantageous to limit the content of monomer (m3) in the monomer component and relatively increase the content of monomer (m1). From this perspective, it is advantageous for the monomer (m3) content to be less than 24% by weight of the monomer component, preferably less than 23% by weight, more preferably less than 20% by weight, possibly less than 17% by weight, possibly less than 12% by weight, possibly less than 7% by weight, possibly less than 3% by weight, or possibly less than 1% by weight. Alternatively, monomer (m3) may be used substantially without any monomer content.

[0096] (Other monomers)

[0097] The monomer components constituting the acrylic polymer (A) may, as needed, include monomers other than those mentioned above (m1), (m2), and (m3) (hereinafter referred to as "other monomers"). These other monomers may be used for purposes such as adjusting the Tg of the acrylic polymer (A), adjusting its adhesive properties, and improving compatibility within the adhesive layer. One of these other monomers may be used alone, or two or more may be used in combination.

[0098] Examples of other monomers mentioned above include monomers having functional groups other than hydroxyl and carboxyl groups (monomers containing functional groups). For example, monomers containing sulfonic acid groups, phosphate groups, and cyano groups can be listed as other monomers that can improve the cohesiveness and heat resistance of adhesives. In addition, monomers that can introduce functional groups that can serve as crosslinking sites into acrylic polymers (A), or that can help improve peel strength and compatibility within the adhesive layer, can be listed as amide-containing monomers (e.g., (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, etc.), amino-containing monomers (e.g., (meth)acrylate aminoethyl ester, (meth)acrylate N,N-dimethylaminoethyl ester, etc.), monomers having a ring containing a nitrogen atom (e.g., N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide-containing monomers, epoxy-containing monomers, ketone-containing monomers, isocyanate-containing monomers, alkoxysilyl-containing monomers, etc. It should be noted that monomers with nitrogen-containing rings, such as N-vinyl-2-pyrrolidone, also belong to the category of amide-containing monomers. The same applies to the relationship between the aforementioned monomers with nitrogen-containing rings and amino-containing monomers.

[0099] Other monomers that can be used besides the functionalized monomers mentioned above include vinyl acetate and other vinyl ester monomers; (meth)acrylates containing non-aromatic rings, such as cyclohexyl methacrylate and isobornyl methacrylate; olefin monomers such as ethylene, butadiene, and isobutene; chlorinated monomers such as vinyl chloride; alkoxy-containing monomers such as methoxyethyl methacrylate, ethoxyethyl methacrylate, and ethoxyethoxyethyl methacrylate; vinyl ether monomers such as methyl vinyl ether; etc. As a suitable example of other monomers that can be used for purposes such as improving the flexibility of adhesives, ethoxyethoxyethyl acrylate (also known as ethyl carbitol acrylate, Tg of homopolymer: -67°C) can be listed.

[0100] When using the other monomers mentioned above, there are no particular restrictions on their usage, and they can be appropriately set within a range where the total amount of monomer components does not exceed 100% by weight. In some embodiments, from the viewpoint of easily maximizing the refractive index increase effect brought about by the use of monomer (m1), the content of the other monomers mentioned above in the monomer component can be set to, for example, about 35% by weight or less, about 25% by weight or less (e.g., 0 to 25% by weight), about 20% by weight or less (e.g., 0 to 20% by weight), about 10% by weight or less, about 5% by weight or less, or about 1% by weight or less. The technology disclosed herein can preferably be implemented in a manner in which the monomer component substantially does not contain the other monomers mentioned above.

[0101] In some embodiments, the monomeric components constituting the acrylic polymer (A) may be compositions in which the amount of methacrylamide monomer used is suppressed to a specified level. For example, the amount of methacrylamide monomer used in the monomeric components may be less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. From the viewpoint of achieving a good balance between flexibility, adhesion, and high refractive index in the adhesive, limiting the amount of methacrylamide monomer used in this way can be advantageous. The monomeric components constituting the acrylic polymer (A) may also be compositions that do not contain methacrylamide monomers (e.g., compositions that contain only acryloyl monomers).

[0102] In some embodiments, for the monomer components constituting the acrylic polymer (A), from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the adhesive, it is preferable to limit the amount of carboxyl-containing monomers used. The amount of carboxyl-containing monomers used in the monomer components may, for example, be 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. Limiting the amount of carboxyl-containing monomers in this way is also advantageous from the viewpoint of suppressing corrosion of metallic materials (e.g., metal wiring, metal films, etc., that may be present on the adhered objects) that may come into contact with or approach the adhesives disclosed herein. The techniques disclosed herein can preferably be implemented in a manner where the aforementioned monomer components do not contain carboxyl-containing monomers.

[0103] For the same reason, in some embodiments, the amount of monomers constituting the acrylic polymer (A) preferably limited to those having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc., in addition to carboxyl groups). The amount of acidic functional group-containing monomers used in the monomer components of this embodiment can be determined by the preferred amount of carboxyl-containing monomers described above. The technology disclosed herein can preferably be implemented in a manner where the monomer components do not contain acidic groups (i.e., the acrylic polymer (A) is acid-free).

[0104] (glass transition temperature Tg) T )

[0105] In some methods, the glass transition temperature Tg of the monomer components constituting the acrylic polymer (A) is based on the composition of those monomer components. T A temperature below approximately 20°C is suitable, preferably below approximately 10°C, more preferably below 0°C, and can be below -10°C, below -20°C, below -25°C, below -28°C, or below -30°C. Glass transition temperature Tg T A lower glass transition temperature (Tg) can be advantageous from the perspective of improved adhesive flexibility. Additionally, the glass transition temperature (Tg) is also important. T For example, the temperature can be -60°C or higher. From the viewpoint of making it easier to increase the refractive index of the adhesive, it is preferably -50°C or higher, more preferably higher than -45°C, higher than -40°C, higher than -35°C, higher than -25°C, higher than -15°C, or higher than -5°C.

[0106] Here, the glass transition temperature Tg T Unless otherwise specified, this refers to the glass transition temperature calculated using the Fox formula based on the composition of the aforementioned monomer components. The Fox formula, as shown below, is the relationship between the glass transition temperature (Tg) of the copolymer and the glass transition temperature (Tgi) of the homopolymer formed by the homopolymerization of each of the monomers constituting the copolymer.

[0107] 1 / Tg=Σ(Wi / Tgi)

[0108] In the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0109] The glass transition temperature (Tg) of homopolymers used for calculating Tg is the value recorded in known sources such as the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). For monomers for which multiple values ​​are recorded in the aforementioned Polymer Handbook, the highest value is used. Where the Tg of homopolymers is not recorded in known sources, the value obtained by the determination method described in Japanese Patent Application Publication No. 2007-51271 is used.

[0110] (Preparation method of acrylic polymer (A))

[0111] In the technology disclosed herein, there is no particular limitation on the method for obtaining the acrylic polymer (A) composed of this monomer component. Various polymerization methods known as synthetic methods for acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, solution polymerization is preferred. The polymerization temperature during solution polymerization can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc., and can be set to approximately 20°C to 170°C (typically approximately 40°C to 140°C).

[0112] The solvent used in solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents. For example, one or a mixture of two or more solvents can be used, selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (e.g., monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc.

[0113] The initiator used in the polymerization can be appropriately selected from conventionally known polymerization initiators, depending on the type of polymerization method. For example, one or more azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) are preferred. Other examples of polymerization initiators 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. Further examples of polymerization initiators include redox initiators based on combinations of peroxides and reducing agents. One polymerization initiator can be used alone or in combination of two or more. The amount of polymerization initiator used is the usual amount, for example, it can be selected from a range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) relative to 100 parts by weight of monomer content.

[0114] In the above polymerization, various conventionally known chain transfer agents can be used as needed. For example, thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoacetic acid, and α-thioglycerol can be used. Alternatively, chain transfer agents without sulfur atoms (non-sulfur chain transfer agents) can also be used. Examples of non-sulfur chain transfer agents include: anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenes such as α-pinene and terpinene; styrene such as α-methylstyrene and α-methylstyrene dimer; etc. One chain transfer agent can be used alone or in combination of two or more. The amount of chain transfer agent used relative to 100 parts by weight of the monomer raw material can be set to, for example, approximately 0.01 to 1 part by weight.

[0115] The weight-average molecular weight (Mw) of the aforementioned acrylic polymer (A) is not particularly limited, and can be, for example, about 10 × 10⁻⁶. 4 ~500×10 4 From the viewpoint of adhesive properties, the Mw of the acrylic polymer (A) is preferably in the range of about 20 × 10⁻⁶. 4 ~400×10 4 (More preferably about 30×10) 4 ~150×10 4 For example, approximately 50 × 10 4 ~130×10 4 ) range.

[0116] Here, the Mw of the acrylic polymer (A) can be obtained by gel permeation chromatography (GPC) to convert it to polystyrene. Specifically, the Mw can be obtained by using the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation) as the GPC measuring device, and the determination can be performed under the following conditions.

[0117] [GPC Measurement Conditions]

[0118] Sample concentration: 0.2% by weight (tetrahydrofuran solution)

[0119] Sample injection volume: 10 μL

[0120] Eluent: Tetrahydrofuran (THF)

[0121] Flow rate: 0.6 mL / min

[0122] Column temperature (measurement temperature): 40℃

[0123] column:

[0124] Sample column: 1 brand name "TSKguardcolumn SuperHZ-H" + 2 pieces "TSKgel SuperHZM-H" brand name (manufactured by Tosoh Corporation)

[0125] Reference column: 1 brand name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation)

[0126] Detector: Differential refractometer (RI)

[0127] Standard sample: polystyrene

[0128] (additives (H) RO ))

[0129] As an additive (H) in the technology disclosed herein ROIn contrast to the aforementioned acrylic polymer (A), an organic material with a higher refractive index is used. Here, the aforementioned "H" RO "High refractive index" indicates an organic material. This is achieved through the combined use of additives (H...) RO (A) and acrylic polymers (A) can achieve adhesives that appropriately balance refractive index and adhesive properties (peel strength, flexibility, etc.) and / or optical properties (total transmittance, haze value, etc.). Used as an additive (H) RO The organic material can be a polymer or a non-polymer. Furthermore, it may or may not have polymerizable functional groups. Additives (H) RO One type can be used alone or two or more types can be used in combination.

[0130] Additives (H) RO The refractive index of (A) can be set to an appropriate range based on its relative relationship with the refractive index of the acrylic polymer (A), and is therefore not limited to a specific range. Additive (H) RO The refractive index of the adhesive can be selected, for example, from a range higher than 1.55, higher than 1.56, or higher than 1.57, and higher than the refractive index of the acrylic polymer (A). From the viewpoint of increasing the refractive index of the adhesive, in some ways, the additive (H) RO It is advantageous for the refractive index of the additive to be 1.58 or higher, preferably 1.60 or higher, more preferably 1.63 or higher, and can be 1.65 or higher, 1.70 or higher, or 1.75 or higher. Using an additive with a higher refractive index (H...) RO Even when using a smaller amount of additive (H) RO This can also achieve the target refractive index. This is preferable from the viewpoint of suppressing the reduction of adhesive properties and optical properties. Additive (H) RO There is no particular upper limit to the refractive index of the adhesive. From the perspective of compatibility within the adhesive, ease of achieving high refractive index and flexibility suitable for use as an adhesive, it can be, for example, below 3.000, below 2.500, below 2.000, below 1.950, below 1.900, or below 1.850.

[0131] It should be noted that the additive (H) RO The refractive index of the sample was measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25 °C, in the same manner as the refractive index of the monomer. If the manufacturer provides a nominal value for the refractive index at 25 °C, that value can be used.

[0132] Additives (H) RO The refractive index nb The refractive index n of acrylic polymer (A) a The difference, i.e., n b -n a (hereinafter also referred to as "Δn") A The value is set to greater than 0. In some methods, Δn A For example, it can be 0.02 or higher, 0.05 or higher, 0.07 or higher, 0.10 or higher, 0.15 or higher, or 0.20 or higher, or 0.25 or higher. This is achieved by selecting acrylic polymers (A) and additives (H). RO And thus Δn A It becomes larger, with additives (H) RO The use of [a specific ingredient] tends to increase the refractive index effect. Additionally, additives (H [a specific ingredient]) within the adhesive layer [can also contribute to this effect]. RO From the perspective of compatibility, in some ways, Δn A For example, it can be below 0.70, below 0.60, below 0.50, below 0.40, or below 0.35.

[0133] In some methods, additives (H) RO The refractive index n b With the addition of this additive (H) RO The refractive index n of the adhesive layer T The difference, i.e., n b -n T (hereinafter also referred to as "Δn") B ") can be set to greater than 0. In some methods, Δn B For example, it can be 0.02 or higher, 0.05 or higher, 0.07 or higher, 0.10 or higher, 0.15 or higher, or 0.20 or higher, or 0.25 or higher. This can be achieved by selecting the composition of the adhesive layer and the additives (H... RO And thus Δn B It becomes larger, with additives (H) RO The use of ) tends to increase the refractive index effect. Furthermore, from the perspectives of compatibility within the adhesive layer and the transparency of the adhesive layer, in some methods, Δn B For example, it can be below 0.70, below 0.60, below 0.50, below 0.40, or below 0.35.

[0134] As an additive (H) ROThe molecular weight of the organic materials used is not particularly limited and can be selected according to the purpose. From the viewpoint of achieving a good balance between the effect of high refractive index and other properties (such as suitability for adhesive flexibility, haze, and other optical properties), in some methods, additives (H... RO The molecular weight of the additive (H) is preferably below about 10,000, more preferably below 5,000, and even more preferably below 3,000 (e.g., below 1,000). It can be below 800, below 600, below 500, or below 400. RO When the molecular weight of the additive (H) is not too large, it can be advantageous from the perspective of improving compatibility within the adhesive layer. Additionally, the additive (H) RO The molecular weight of the additive (H) can be, for example, 130 or more, or 150 or more. In some methods, the molecular weight of the additive (H) is... RO From the perspective of increasing the refractive index of ), additives (H) RO The molecular weight of the additive is preferably 170 or higher, more preferably 200 or higher, and can be 230 or higher, 250 or higher, 270 or higher, 500 or higher, 1000 or higher, or 2000 or higher. In some embodiments, polymers with a molecular weight of around 1000 to 10000 (e.g., 1000 or higher but lower than 5000) can be used as additives (H). RO ).

[0135] As an additive (H) RO The molecular weight of the additive (H) can be calculated based on its chemical structure for non-polymers or polymers with low polymerization degree (e.g., around 2-5 polymers), or determined using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF-MS). RO When the polymer is a polymer with a higher degree of polymerization, the weight-average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. If a nominal value of the molecular weight is provided by the manufacturer, etc., that nominal value can be used.

[0136] It can be used as an additive (H) RO Examples of organic materials for the option include, but are not limited to, organic compounds having aromatic rings, organic compounds having heterocycles (which may be aromatic or non-aromatic heterocycles).

[0137] As an additive (H) RO The aromatic ring of the above-mentioned organic compound with an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") used may be selected from the same aromatic ring as that of the compound used as a monomer (m1).

[0138] The aromatic ring described above may have one or more substituents on the cyclizing atom, or it may not have any substituents. When substituents are present, examples of such substituents include alkyl, alkoxy, aryloxy, hydroxy, halogen atoms (fluorine, chlorine, bromine, etc.), hydroxyalkyl, hydroxyalkyloxy, epoxypropoxy, etc., but are not limited to these. Among the substituents 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 3, for example, 1 or 2. In some embodiments, the aromatic ring described above may be an aromatic ring that does not have substituents on the cyclizing atom, or has one or more substituents selected from the group consisting of alkyl, alkoxy, and halogen atoms (e.g., bromine atoms).

[0139] As an additive (H) RO Examples of aromatic ring-containing compounds include, for example, compounds that can be used as monomers (m1); oligomers containing compounds that can be used as monomers (m1) as monomer units; compounds formed by removing and replacing a group having an olefinically unsaturated group (which may be a substituent bonded to a cyclic atom) or a portion of that group constituting the olefinically unsaturated group with a hydrogen atom or a group not having an olefinically unsaturated group (e.g., hydroxyl, amino, halogen atom, alkyl, alkoxy, hydroxyalkyl, hydroxyalkyloxy, epoxypropoxy, etc.) from a compound that can be used as a monomer (m1); etc., but not limited to these. RO Non-limiting examples of aromatic ring-containing compounds may include: benzyl acrylate, m-phenoxybenzyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxy polyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, monomers having a fluorene structure, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure, etc., aromatic ring-containing monomers; 3-phenoxybenzyl alcohol, dinaphthothiophene and its derivatives (e.g., compounds with a structure in which one or more substituents selected from hydroxyl, methanol, diethanol, glycidyl, etc., are bonded to the dinaphthothiophene ring), etc., aromatic ring-containing compounds without olefinic unsaturated groups; etc. Furthermore, aromatic ring-containing compounds may be oligomers containing such aromatic ring-containing monomers as monomer units (preferably oligomers with a molecular weight of about 5000 or less, more preferably about 1000 or less; for example, oligomers of about 2 to 5 polymers). The aforementioned oligomers may be, for example, homopolymers of monomers containing aromatic rings; copolymers of one or more monomers containing aromatic rings; copolymers of one or more monomers containing aromatic rings with other monomers; etc. As the aforementioned other monomers, one or more monomers without aromatic rings may be used.

[0140] In some methods, as an additive (H)RO From the perspective of easily obtaining a high refractive index effect, organic compounds having two or more aromatic rings per molecule (hereinafter also referred to as "compounds containing multiple aromatic rings") are preferred. Compounds containing multiple aromatic rings may or may not have polymerizable functional groups such as olefinic unsaturated groups. Furthermore, compounds containing multiple aromatic rings can be polymers or non-polymers. Additionally, the aforementioned polymers can be oligomers containing monomers containing multiple aromatic rings as monomer units (preferably oligomers with a molecular weight of about 5000 or less, more preferably about 1000 or less; for example, oligomers of about 2 to 5 polymers). The aforementioned oligomers can be, for example, homopolymers of monomers containing multiple aromatic rings; copolymers of one or more monomers containing multiple aromatic rings; copolymers of one or more monomers containing multiple aromatic rings with other monomers; etc. The aforementioned other monomers can be monomers containing aromatic rings that are not monomers containing multiple aromatic rings, monomers without aromatic rings, or combinations thereof.

[0141] Non-limiting examples of compounds containing multiple aromatic rings include: compounds having a structure in which two or more non-fused aromatic rings are bonded together by a linking group; compounds having a structure in which two or more non-fused aromatic rings are directly (i.e., without the aid of other atoms) chemically bonded together; compounds having a fused aromatic ring structure; compounds having a fluorene structure; compounds having a dinaphthothiophene structure; and compounds having a dibenzothiophene structure. Compounds containing multiple aromatic rings may be used alone or in combination of two or more.

[0142] As specific examples of the compounds having the fluorene structure, in addition to the monomers having the fluorene structure and the oligomers of the homopolymers or copolymers thereof, examples include 9,9-bis(4-hydroxyphenyl)fluorene (refractive index: 1.68), 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[4-(2-hydroxyethoxy)phenyl]fluorene (refractive index: 1.65), and other 9,9-bisphenylfluorene and their derivatives.

[0143] As specific examples of compounds having the dinaphthothiophene structure, in addition to the monomers having the dinaphthothiophene structure and oligomers of homopolymers or copolymers thereof, examples include dinaphthothiophene (refractive index: 1.808); 6-hydroxymethyl dinaphthothiophene (refractive index: 1.766) and other hydroxyalkyl dinaphthothiophenes; 2,12-dihydroxydinaphthothiophene (refractive index: 1.750) and other dihydroxydinaphthothiophenes; 2,12-di... Dihydroxyalkyloxydinaphthothiophene (refractive index: 1.677) and other dihydroxyalkyloxydinaphthothiophenes; 2,12-diglycidyloxydinaphthothiophene (refractive index: 1.723) and other diglycidyloxydinaphthothiophenes; 2,12-diallyloxydinaphthothiophene (abbreviation: 2,12-DAODNT, refractive index: 1.729) and other dinaphthothiophenes having two or more olefinic unsaturated groups; and other dinaphthothiophenes and their derivatives.

[0144] As specific examples of compounds having the dibenzothiophene structure, in addition to the monomers having the dibenzothiophene structure and the oligomers that are homopolymers or copolymers of the monomers, examples include dibenzothiophene (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), and 4,6-dimethyldibenzothiophene (refractive index: 1.617).

[0145] As a potential additive (H) RO Examples of heterocyclic organic compounds (hereinafter also referred to as heterocyclic organic compounds) that are options for the following can be listed: thioepoxides, compounds having triazine rings, etc. As an example of a thioepoxide, the bis(2,3-cyclothiopropyl) disulfide and its polymer (refractive index 1.74) disclosed in Japanese Patent No. 3712653 can be listed. As an example of a compound having a triazine ring, compounds having at least one triazine ring (e.g., 3 to 40, preferably 5 to 20) per molecule can be listed. It should be noted that triazine rings are aromatic; therefore, compounds having triazine rings are also included in the above concept of compounds containing aromatic rings. Furthermore, compounds having multiple triazine rings are also included in the above concept of compounds containing multiple aromatic rings.

[0146] In some methods, as an additive (H) RO The preferred choice is a compound without olefinic unsaturated groups. This suppresses the deterioration of the adhesive composition caused by heat and light (due to gelation and increased viscosity leading to decreased leveling properties) and improves storage stability. From the presence of this additive (H... ROFrom the viewpoint of suppressing dimensional changes, deformations (warping, undulations, etc.), and optical distortions caused by the reaction of olefinic unsaturated groups in adhesive sheets containing adhesive layers and laminates containing such adhesive sheets, it is also preferable to use additives (H) that do not have olefinic unsaturated groups. RO ).

[0147] Using oligomers as additives (H) RO In this process, the oligomer can be obtained by polymerizing the corresponding monomer components using known methods. When manufacturing the above-mentioned oligomer via free radical polymerization, polymerization initiators, chain transfer agents, emulsifiers, etc., used for free radical polymerization can be appropriately added to the monomer components to carry out polymerization. There are no particular limitations on the polymerization initiators, chain transfer agents, emulsifiers, etc., used for free radical polymerization, and they can be selected and used appropriately. It should be noted that the weight-average molecular weight of the oligomer can be controlled by the amount of polymerization initiator and chain transfer agent used, and the reaction conditions; their amounts should be adjusted appropriately according to their types.

[0148] Examples of chain transfer agents include lauryl thiol, glycidyl thiol, thioethanol, 2-mercaptoethanol, α-thioglycerol, mercaptoacetic acid, 2-ethylhexyl mercaptoacetic acid, and 2,3-dimercapto-1-propanol. One chain transfer agent can be used alone, or two or more can be used in combination. The amount of chain transfer agent used can be set according to the composition of the monomer components used in the synthesis of the oligomer, the type of chain transfer agent, etc., to obtain an oligomer with the desired weight-average molecular weight. In some cases, it is appropriate to set the amount of chain transfer agent to about 15 parts by weight or less relative to 100 parts by weight of the total amount of monomers used in the synthesis of the oligomer; it can be 10 parts by weight or less, or about 5 parts by weight or less. There is no particular limitation on the lower limit of the amount of chain transfer agent used relative to 100 parts by weight of the total amount of monomers used in the synthesis of the oligomer; for example, it can be 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more.

[0149] Additives (H) RO The amount of additive (H) used relative to 100 parts by weight of acrylic polymer (A) (or the total amount of multiple compounds when using them) is not particularly limited as long as it is greater than 0 parts by weight, and can be set according to the purpose. In some methods, additive (H) RO The amount of additive (H) relative to 100 parts by weight of acrylic polymer (A) can be set to, for example, 80 parts by weight or less. From the viewpoint of achieving a good balance between increasing the refractive index of the adhesive and suppressing the reduction of adhesive and optical properties, setting it to 60 parts by weight or less is advantageous, and preferably 45 parts by weight or less. In some approaches where adhesive and optical properties are given greater emphasis, additive (H) ROThe amount of additive (H) used relative to 100 parts by weight of acrylic polymer (A) can be, for example, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, or 10 parts by weight or less. Furthermore, from the viewpoint of increasing the refractive index of the adhesive, the additive (H) RO The amount of acrylic polymer (A) used relative to 100 parts by weight can be, for example, 1 part by weight or more, 3 parts by weight or more, 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.

[0150] (Cross-linking agent)

[0151] For purposes such as adjusting the cohesive strength of the adhesive, a crosslinking agent may be included as needed. As a crosslinking agent, crosslinking agents known in the field of adhesives can be used, such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based resins, and metal chelate-based crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred. Other examples of crosslinking agents include monomers having two or more olefinic unsaturated groups per molecule, i.e., polyfunctional monomers. One type of crosslinking agent may be used alone, or two or more may be used in combination.

[0152] As isocyanate-based crosslinking agents, isocyanate compounds with two or more functionalities can be used, such as aliphatic polyisocyanates like trimethylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate (HDI), and dimer diisocyanate; alicyclic isocyanates like cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), and 1,3-bis(isocyanate-methyl)cyclohexane; aromatic isocyanates like 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenylenediamine diisocyanate (XDI); and polyisocyanate modifiers that have been modified using urea-formate bonds, biuret bonds, isocyanurate bonds, urea-dione bonds, urea bonds, carbodiimide bonds, urea-ketimide bonds, and oxadiazine-trione bonds; etc. Examples of commercially available products include Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N (and above, manufactured by Takeda Pharmaceutical Company Limited), Sumidur T80, Sumidur L, Desmodur N3400 (and above, manufactured by Sumika Bayer Urethane Co., Ltd.), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX (and above, manufactured by Tosoh Corporation), etc. Isocyanate compounds can be used alone or in combination of two or more. They can also be used in combination of difunctional isocyanate compounds and trifunctional or higher isocyanate compounds.

[0153] Examples of epoxy-based crosslinking agents include bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. These can be used alone or in combination of two or more.

[0154] Examples of multifunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl methacrylate, vinyl methacrylate, divinylbenzene, bisphenoxyethanol fluorene di(meth)acrylate, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyl glycol (meth)acrylate, and hexyl glycol di(meth)acrylate. Multifunctional monomers can be used alone or in combination of two or more.

[0155] When using a crosslinking agent (which can be a multifunctional monomer), the amount used is not particularly limited; for example, it can be set to a range of about 0.001 parts by weight to 5.0 parts by weight relative to 100 parts by weight of the monomer component. From the viewpoint of improving the flexibility of the adhesive, in some embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the monomer component is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and can be 1.0 parts by weight or less, 0.5 parts by weight or less, or 0.2 parts by weight or less. In addition, from the viewpoint of appropriately maximizing the effect of the crosslinking agent, in some embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the monomer component can be, for example, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.08 parts by weight or more.

[0156] To facilitate a more efficient crosslinking reaction, a crosslinking catalyst can be used. Examples of crosslinking catalysts include metal-based crosslinking catalysts such as tetrabutyl titanate, tetraisopropyl titanate, iron acetylacetone, butyl tin oxide, and dioctyltin dilaurate. Among these, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. There is no particular limitation on the amount of crosslinking catalyst used. Considering the balance between the rate of the crosslinking reaction and the pot life of the adhesive composition, the amount of crosslinking catalyst used relative to 100 parts by weight of the monomer component can be set, for example, in the range of about 0.0001 parts by weight and less than 1 part by weight, preferably in the range of 0.001 parts by weight and less than 0.5 parts by weight.

[0157] The adhesive composition may contain a keto-enol tautomer as a crosslinking delay agent. This extends the pot life of the adhesive composition. For example, in adhesive compositions containing isocyanate-based crosslinking agents, a keto-enol tautomer is preferably used. Various β-dicarbonyl compounds can be used as keto-enol tautomers. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetates (methyl acetoacetate, ethyl acetoacetate, etc.) are preferred. One keto-enol tautomer can be used alone or in combination of two or more. The amount of the keto-enol tautomer relative to 100 parts by weight of the monomer component can be, for example, 0.1 parts by weight or more and 20 parts by weight or less, 0.5 parts by weight or more and 10 parts by weight or less, or 1 part by weight or more and 5 parts by weight or less.

[0158] (Thickening agent)

[0159] The adhesive compositions disclosed herein may contain tackifiers. Known tackifiers such as rosin-based, terpene-based, phenolic, hydrocarbon-based, ketone-based, polyamide-based, epoxy-based, and elastic-system tackifiers can be used as tackifiers. One or more of these can be used alone or in combination. The amount of tackifier used is not particularly limited and can be set according to the purpose and application to achieve appropriate adhesive properties. In some embodiments, from the viewpoint of refractive index and transparency, it is appropriate to use 30 parts by weight or less of the tackifier relative to 100 parts by weight of the monomer component, preferably 10 parts by weight or less, and more preferably 5 parts by weight or less. The technology disclosed herein can preferably be implemented without the use of tackifiers.

[0160] (Plasticized materials)

[0161] In some embodiments of the adhesive composition disclosed herein, the adhesive composition may further comprise a plasticizing material with a molecular weight lower than that of the acrylic polymer (A) as an additive used as desired. The use of the plasticizing material improves the flexibility of the adhesive layer, enhances adhesion to the adhered objects, improves the overall flexibility of the adhesive sheet, and increases its adaptability to deformation. From the viewpoint of compatibility and transparency within the adhesive layer, organic materials are preferred as the plasticizing material. The plasticizing material may also be any material that can be used as the aforementioned additive (H). RO (materials).

[0162] The molecular weight of the plasticizing material is not particularly limited as long as it is lower than that of the acrylic polymer (A). In some embodiments, from the viewpoint of easily exhibiting a plasticizing effect, the molecular weight of the plasticizing material can be less than 30,000, less than 25,000, less than 10,000, preferably less than 5,000, more preferably less than 3,000 (e.g., less than 1,000), less than 800, less than 600, less than 500, or less than 400. A lower molecular weight of the plasticizing material is advantageous from the viewpoint of improved compatibility within the adhesive layer. Furthermore, in some embodiments, from the viewpoint of easily achieving a sufficient plasticizing effect, a molecular weight of 130 or more is appropriate, preferably 150 or more, and can be 170 or more, 200 or more, 250 or more, or 300 or more. In some embodiments, the molecular weight of the plasticizing material can be 500 or more, 1,000 or more, or 2,000 or more. When the molecular weight of the plasticizing material is not too low, it is also preferred from the perspective of the heat resistance of the adhesive sheet and the inhibition of contamination of the adhered material.

[0163] Non-limiting examples of compounds that can be used as plasticizing materials include: compounds that can be used as monomers (m1) (e.g., (meth)acrylates having aromatic rings such as benzyl, phenoxy, and naphthyl; monomers having a fluorene structure; monomers having a dinaphthothiophene structure; monomers having a dibenzothiophene structure, etc.); oligomers containing compounds that can be used as monomers (m1) as monomer units; compounds with structures formed by removing and replacing the portion having an olefinically unsaturated group from compounds that can be used as monomers (m1) with a hydrogen atom or a group that does not have an olefinically unsaturated group (e.g., 3-phenoxybenzyl alcohol); etc. For oligomers containing compounds that can be used as monomers (m1) as monomer units, from the viewpoint of improving flexibility, low Tg monomers such as n-butyl acrylate and 2-ethylhexyl acrylate can also be copolymerized, for example. As a plasticizing material, one or more of the known plasticizers (such as phthalate esters, terephthalate esters, adipate esters, adipate polyesters, dibenzoic acid esters, etc.) can be used.

[0164] In some methods, organic materials with a refractive index of about 1.50 or higher (more preferably 1.53 or higher) are preferably used as plasticizers. Specific examples of compounds that can be used as plasticizers include: diethylene glycol dibenzoate (refractive index 1.55), dipropylene glycol dibenzoate (refractive index 1.54), 3-phenoxytoluene (refractive index 1.57), 3-ethylbiphenyl (refractive index 1.59), 3-methoxybiphenyl (refractive index 1.61), 4-methoxybiphenyl (refractive index 1.57), polyethylene glycol dibenzoate, 3-phenoxybenzyl alcohol (refractive index 1.59), triphenyl phosphate (refractive index 1.56), benzyl benzoate (refractive index 1.57), 4-(tert-butyl) Phenyl diphenyl phosphate (refractive index 1.56), trimethylphenyl phosphate (refractive index 1.55), butyl benzyl phthalate (refractive index 1.54), rosin methyl ester (refractive index 1.53), alkyl benzyl phthalate (refractive index 1.53), butyl(benzenesulfonyl)amine (refractive index 1.53), trimethyl trimellitate (refractive index 1.52), benzyl phthalate (refractive index 1.52), 2-ethylhexyl diphenyl phosphate (refractive index 1.51), tris(2,4-di-tert-butylphenyl) phosphite, etc., but not limited to these. From the viewpoint of refractive index and compatibility, diethylene glycol dibenzoate, for example, may be preferred. There is no particular upper limit to the refractive index of the plasticizing material, for example, it can be below 3.00. In some approaches, from the viewpoints of ease of preparation of the adhesive composition and compatibility within the adhesive, it is appropriate for the refractive index of the plasticizing material to be below 2.50, advantageous to be below 2.00, below 1.90, below 1.80, or below 1.70.

[0165] It should be noted that the refractive index of the plasticized material is measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25°C, just like the refractive index of the monomer. If the manufacturer provides a nominal value for the refractive index at 25°C, that value can be used.

[0166] In using plasticizing materials, the amount of plasticizing material relative to 100 parts by weight of acrylic polymer (A) is not particularly limited and can be set according to the purpose. From the viewpoint of improving the plasticizing effect, the amount of plasticizing material relative to 100 parts by weight of acrylic polymer (A) can 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, it is preferable to set it to 1 part by weight or more, more preferably 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more. In addition, from the viewpoint of achieving a good balance between the high refractive index and transparency of the adhesive and the plasticizing effect, it is appropriate to set the amount of plasticizing material relative to 100 parts by weight of acrylic polymer (A) to about 100 parts by weight or less, preferably 80 parts by weight or less, more preferably 60 parts by weight or less, 45 parts by weight or less, 35 parts by weight or less, or 25 parts by weight or less. In some approaches that place greater emphasis on adhesive and optical properties, the amount of plasticizer used relative to 100 parts by weight of acrylic polymer (A) may be less than 15 parts by weight, less than 10 parts by weight, or less than 5 parts by weight.

[0167] (Leveling agent)

[0168] The adhesive compositions disclosed herein may contain leveling agents as needed to improve the appearance of the adhesive layer formed from the composition (e.g., to improve the uniformity of thickness) and to improve the coatability of the adhesive composition. Non-limiting examples of leveling agents include acrylic leveling agents, fluorinated leveling agents, and silicone leveling agents. For example, suitable substances can be selected from commercially available leveling agents and used by conventional methods.

[0169] In some embodiments, as the leveling agent described above, a polymer (hereinafter referred to as "polymer (B)") comprising a monomer raw material (hereinafter referred to as "monomer S1") having a polyorganosiloxane backbone and an acrylic monomer (hereinafter referred to as "monomer raw material B") may preferably be used. Polymer (B) may refer to a copolymer of monomer S1 and an acrylic monomer. Polymer (B) may be used alone or in combination of two or more.

[0170] As monomer S1, there are no particular limitations, and any monomer containing a polyorganosiloxane backbone can be used. As monomer S1, monomers with a structure having a polymerizable reactive group at one end are preferred. Among these, monomer S1 with a polymerizable reactive group at one end and no functional group at the other end that would crosslink with the acrylic polymer (A) is preferred. Commercially available examples include single-terminal reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd. (e.g., trade names X-22-174ASX, X-22-2426, X-22-2475, KF-2012, etc.). Monomer S1 can be used alone or in combination of two or more.

[0171] The functional group equivalent of monomer S1 can be, for example, around 100 g / mol to 30,000 g / mol. In some preferred embodiments, the functional group equivalent is, for example, 500 g / mol or more, 800 g / mol or more, 1500 g / mol or more, or 2000 g / mol or more. Alternatively, the functional group equivalent can be, for example, below 20,000 g / mol, below 10,000 g / mol, below 7,000 g / mol, or below 5,500 g / mol. When the functional group equivalent of monomer S1 is within the above range, it is easy to achieve good leveling effect.

[0172] It should be noted that when using two or more monomers with different functional group equivalents as monomer S1, the functional group equivalent of monomer S1 can be the sum of the products of the functional group equivalents of each monomer and the weight fraction of that monomer.

[0173] Here, "functional group equivalent" refers to the weight of the backbone (e.g., polydimethylsiloxane) bonded by each functional group. The unit g / mol is used to convert to 1 mol of functional groups. The functional group equivalent of monomer S1 can be determined, for example, based on nuclear magnetic resonance (NMR)... 1 It is calculated from the spectral intensity of H-NMR (proton NMR). 1 The calculation of the functional group equivalent (g / mol) of monomer S1 from the spectral intensity of H-NMR can be based on 1 The usual structural analysis methods in H-NMR spectroscopy should be followed as described in Japanese Patent No. 5951153, as needed. In the functional group equivalent of monomer S1, the aforementioned functional groups refer to polymerizable functional groups (e.g., olefinic unsaturated groups such as (meth)acryloyl, vinyl, allyl, etc.).

[0174] The content of monomer S1 in monomer raw material B can be an appropriate value within the range that allows the desired effect to be achieved using monomer S1, and is not limited to a specific range. In some embodiments, the content of monomer S1 in monomer raw material B can be, for example, 5-60% by weight, 10-50% by weight, or 15-40% by weight.

[0175] In addition to monomer S1, monomer raw material B also contains acrylic monomers capable of copolymerizing with monomer S1. This improves the compatibility of the polymer (B) within the adhesive layer. Examples of acrylic monomers that can be used in monomer raw material B include alkyl acrylates. Here, "alkyl" refers to chain-like (including linear and branched) alkyl groups, excluding alicyclic hydrocarbon groups described later. In some embodiments, monomer raw material B may contain (meth)acrylic acid C. 4-12 Alkyl ester (preferably (meth)acrylic acid C) 4-10 Alkyl esters, such as (meth)acrylic acid C 6-10 At least one of alkyl esters. In some other embodiments, monomer raw material B may contain methacrylic acid C. 1-18 Alkyl ester (preferably C methacrylate) 1-14 Alkyl esters, such as C methacrylate 1-10 At least one of alkyl esters. Monomer raw material B may, for example, contain one or more of methyl methacrylate (MMA), n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (2EHMA) as acrylic monomers.

[0176] Other examples of the aforementioned acrylic monomers include (meth)acrylates having alicyclic hydrocarbon groups. Examples include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, and 1-adamantyl (meth)acrylate. Alternatively, (meth)acrylates without alicyclic hydrocarbon groups may also be used.

[0177] The content of the above-mentioned alkyl methacrylate and the above-mentioned methacrylate having alicyclic hydrocarbon group in monomer raw material B can be, for example, 10% or more and 95% or less by weight, 20% or more and 95% or less by weight, 30% or more and 90% or less by weight, 40% or more and 90% or less by weight, or 50% or more and 85% or less by weight.

[0178] Other examples of monomers that can be included together with monomer S1 in monomer raw material B include: carboxyl-containing monomers, anhydride-containing monomers, hydroxyl-containing monomers, epoxy-containing monomers, cyano-containing monomers, isocyanate-containing monomers, amide-containing monomers, monomers having a ring containing a nitrogen atom, aminoalkyl esters of (meth)acrylate, vinyl esters, vinyl ethers, olefins, (meth)acrylates having an aromatic hydrocarbon group, (meth)acrylates containing a halogen atom, etc.

[0179] The Mw of polymer (B) can be, for example, 5000 or more, preferably 10000 or more, or 15000 or more. Alternatively, the Mw of polymer (B) can be, for example, 200000 or less, preferably 100000 or less, 50000 or less, or 30000 or less. By setting the Mw of polymer (B) within an appropriate range, suitable compatibility and leveling properties can be achieved.

[0180] Polymer (B) can be produced, for example, by polymerizing the aforementioned monomers using known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization.

[0181] To adjust the molecular weight of polymer (B), chain transfer agents can be used as needed. Examples of chain transfer agents include: compounds containing thiol groups such as n-dodecyl mercaptan, mercaptoethanol, and α-thioglycerol; thioglycolic acid esters such as thioglycolic acid and methyl thioglycolate; α-methylstyrene dimers; etc. There are no particular limitations on the amount of chain transfer agent used; it can be appropriately set to obtain polymer (B) with the desired molecular weight. In some methods, the amount of chain transfer agent used relative to 100 parts by weight of the monomer can 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.

[0182] The amount of polymer (B) used relative to 100 parts by weight of acrylic polymer (A) can be set to, for example, 0.001 parts by weight or more. From the viewpoint of obtaining a better performance, it can be set to 0.01 parts by weight or more, or 0.03 parts by weight or more. In addition, the amount of polymer (B) used can be, for example, 3 parts by weight or less. From the viewpoint of reducing the influence on the refractive index, it is appropriate to set it to 1 part by weight or less, or 0.5 parts by weight or less, or 0.1 parts by weight or less.

[0183] (Inorganic particles)

[0184] The techniques disclosed herein can preferably be implemented without substantially using inorganic particles for increasing the refractive index, but to a limit that will not significantly impair the application effect of the techniques disclosed herein, with the addition of additives (HRO It is also acceptable to use high-refractive-index inorganic particles as an adjunct to the above-mentioned inorganic particles. Examples of such inorganic particles include those composed of inorganic oxides (specifically, metal oxides) such as titanium oxide (titanium oxide, TiO2), zirconium oxide (zirconia, ZrO2), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide (Nb2O5, etc.). The average particle size of these inorganic particles (referring to the 50% volume average particle size based on laser scattering / diffraction) can, for example, be selected from the range of approximately 10 nm to 100 nm. The amount of the above-mentioned inorganic particles used is preferably less than 5 parts by weight relative to 100 parts by weight of the acrylic polymer (A), more preferably less than 1 part by weight. When using additives (H... RO In the method described above, the amount of the inorganic particles used, on a weight basis, is preferably set to the amount of the additive (H) RO The dosage is less than twice that of the original dosage, preferably less than once or less than 0.5 times.

[0185] (Other additives)

[0186] The adhesive compositions disclosed herein may, as needed, include plasticizers, softeners, colorants, antistatic agents, anti-aging agents, UV absorbers, antioxidants, light stabilizers, preservatives, and other known additives that can be used in adhesive compositions, without significantly impairing the effects of the invention. Regarding these various additives, conventionally known substances can be used by conventional methods, and since they do not particularly characterize the invention, detailed descriptions are omitted.

[0187] <Adhesive>

[0188] The adhesives disclosed herein can be formed using any of the adhesive compositions described above. This adhesive can be a cured product of the aforementioned adhesive compositions, obtained by curing solvent-based, active energy ray-cured, water-dispersible, or hot-melt adhesive compositions through drying, crosslinking, polymerization, cooling, etc. The curing method of the adhesive composition (e.g., drying, crosslinking, polymerization, cooling, etc.) can be applied in only one manner, or in two or more manner simultaneously or in multiple stages. For solvent-based adhesive compositions, typically the composition can be dried (preferably further crosslinked) to form an adhesive. For active energy ray-cured adhesive compositions, typically, polymerization and / or crosslinking reactions are carried out by irradiation with active energy rays to form the adhesive. When drying is required for active energy ray-cured adhesive compositions, irradiation with active energy rays after drying is preferable.

[0189] (Refractive index)

[0190] The adhesives disclosed herein may be adhesives exhibiting a refractive index of a specified value or higher. According to the technology disclosed herein, adhesives with a refractive index of, for example, 1.560 or higher (preferably 1.570 or higher, more preferably higher than 1.570), adhesive compositions capable of forming the adhesives, and adhesive sheets comprising the aforementioned adhesives can be provided.

[0191] It should be noted that, in this specification, the refractive index of the adhesive refers to the refractive index of the adhesive surface (adhesive surface). The refractive index of the adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) at a measurement wavelength of 589 nm and a measurement temperature of 25°C. For example, the Abbe refractometer can be the ATAGO "DR-M4" or an equivalent. As the test sample, an adhesive layer formed from the adhesive of the object being evaluated can be used. Specifically, the refractive index of the adhesive can be measured using the method described in the examples below. The refractive index of the adhesive can be adjusted, for example, by the composition of the adhesive.

[0192] In some embodiments, the refractive index of the adhesive is preferably 1.575 or higher (e.g., above 1.575), more preferably 1.580 or higher, even more preferably 1.585 or higher, and particularly preferably 1.590 or higher (e.g., above 1.595). With an adhesive having this refractive index, the behavior of light can be effectively controlled by utilizing the refractive index difference between the adhesive and the adherend. In some embodiments of the adhesive disclosed herein, the refractive index of the adhesive may, for example, be 1.600 or higher, 1.605 or higher, or 1.610 or higher. The preferred upper limit of the refractive index of the adhesive may vary depending on the refractive index of the adherend, and is therefore not limited to a specific range. In some embodiments, considering a balance with adhesive properties and transparency, the refractive index of the adhesive may, for example, be 1.700 or lower, 1.670 or lower, or 1.650 or lower.

[0193] <Adhesive sheet>

[0194] According to this specification, an adhesive sheet is provided having an adhesive layer. The adhesive constituting the adhesive layer may be an adhesive formed from any of the adhesive compositions disclosed herein (e.g., a cured product of the adhesive composition).

[0195] The aforementioned adhesive sheet can be a substrate-supported adhesive sheet having an adhesive layer on one or both sides of a non-peelable substrate (supporting substrate), or a substrate-free adhesive sheet (i.e., an adhesive sheet without a non-peelable substrate; typically, an adhesive sheet formed of an adhesive layer). The concept of adhesive sheet as used herein can include objects referred to as adhesive tape, adhesive labels, adhesive films, etc. The adhesive sheets disclosed herein can be in roll form or in single sheet form. Alternatively, they can be adhesive sheets further processed into various shapes.

[0196] An example of the composition of the adhesive sheet disclosed herein is shown in Figure 1 The adhesive sheet 1 is constructed in the form of a single-sided adhesive sheet (single-sided adhesive sheet), comprising: an adhesive layer 10 with a first surface 10A serving as the bonding surface (adhesive surface) to the adhered object, and a support substrate 20 laminated on a second surface 10B of the adhesive layer 10. The second surface 10B of the adhesive layer 10 is bonded to the first surface (non-peelable surface) 20A of the support substrate 20. The support substrate 20 can be, for example, a plastic film such as polyester film. The support substrate 20 can also be, for example, an optical film such as a polarizing plate. Before use (before bonding to the adhered object), the adhesive sheet 1 can be, for example, as shown in the image. Figure 1 As shown, the adhesive sheet 50 is in the form of a release liner 30, where the adhesive surface 10A is protected by a release liner 30 that serves as a peelable surface (peel surface) at least on the adhesive layer side. Alternatively, it can be in the form of a second surface 20B of the supporting substrate 20 (the surface opposite to the first surface 20A, also referred to as the back side) serving as the peel surface, and the adhesive surface 10A is protected by being wound or laminated with the adhesive surface 10A abutting against the second surface 20B. The adhesive layer 10 can be a single-layer structure or a laminated structure consisting of two or more different sub-adhesive layers in direct contact (i.e., not separated by a layer made of non-adhesive material) and laminated together.

[0197] There are no particular limitations on the release liner; for example, release liners with a surface release treatment applied to the resin film, paper, or other liner substrate can be used, as well as release liners made of low-adhesion materials such as fluoropolymers (polytetrafluoroethylene, etc.) or polyolefin resins (polyethylene, polypropylene, etc.). The release treatment can, for example, use silicone-based or long-chain alkyl-based release agents. In some embodiments, a resin film with a release treatment is preferred as the release liner.

[0198] The adhesive sheet disclosed herein can also be a substrate-free double-sided adhesive sheet formed by an adhesive layer. For example... Figure 2As shown, the substrate-free double-sided adhesive sheet 2 can be in the following form: before use, the first surface (first adhesive surface) 10A and the second surface (second adhesive surface) 10B of the adhesive layer 10 are protected by release liner 31, 32, which at least have the adhesive layer side as a peelable surface (peel surface). Alternatively, the back side of the release liner 31 (the surface opposite to the adhesive side) can be the peel surface, and the adhesive surfaces 10A, 10B can be protected by winding or laminating the adhesive surface 10B against the back side of the release liner 31. This substrate-free double-sided adhesive sheet can be used, for example, to bond a substrate (which can be an optical component such as an optical film) to at least one of the first adhesive surface and the second adhesive surface. The adhesive layer constituting the substrate-free double-sided adhesive sheet and Figure 1 Similarly, the adhesive layer 10 in the adhesive sheet 1 shown can be a single-layer structure or a laminated structure consisting of two or more sub-adhesive layers that are in direct contact and stacked.

[0199] The adhesive sheet disclosed herein may be a component of an optical component with an adhesive sheet to which an optical element is bonded at least one surface of an adhesive layer. For example, Figure 1 The adhesive sheet 1 shown can be as follows: Figure 3 The optical component 100 with an adhesive sheet to which the optical component 70 is bonded on one surface 10A of the adhesive layer 10 is shown. The optical component can be, for example, a glass plate, a resin film, a metal plate, etc. Furthermore, in Figure 1 When the support substrate 20 in the adhesive sheet 1 shown is an optical component such as an optical film, the adhesive sheet 1 can be used as an optical component with an adhesive sheet attached to the second surface 10B of the adhesive layer 10.

[0200] Furthermore, although not specifically illustrated, the adhesive sheet disclosed herein can also be in the form of a double-sided adhesive sheet with a substrate (a double-sided adhesive sheet with a substrate). This double-sided adhesive sheet with a substrate includes a supporting substrate with a first and a second surface having non-peelability. A first adhesive layer is fixedly laminated to the first surface, and a second adhesive layer is fixedly laminated to the second surface. Examples of such a double-sided adhesive sheet with a substrate include the following forms: Figure 1In the single-sided adhesive sheet 1 shown, the second surface 20B of the support substrate 20 is a non-peeling surface and a second adhesive layer is provided on the second surface 20B. The second surface of the second adhesive layer is joined to the second surface 20B of the support substrate 20, and the first surface (the surface opposite to the second surface) of the second adhesive layer becomes the second adhesive surface of the double-sided adhesive sheet with a carrier substrate. The composition of the adhesive constituting the second adhesive layer may be the same as or different from the composition of the adhesive constituting the first adhesive layer. Regarding the double-sided adhesive sheet with a carrier substrate before use, similarly to the above-mentioned substrate-free double-sided adhesive sheet, it may be in a form in which the first adhesive surface and the second adhesive surface are protected by a release liner.

[0201] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet (including both a substrate-free double-sided adhesive sheet and a double-sided adhesive sheet with a carrier substrate. The same shall apply hereinafter unless otherwise specified), there is no particular limitation on the refractive indices of the first adhesive surface and the second adhesive surface. In some embodiments, it is preferable that at least the first adhesive surface satisfies any one of the above refractive indices, and it may also be a double-sided adhesive sheet in which both the first adhesive surface and the second adhesive surface satisfy any one of the above refractive indices.

[0202] In some embodiments, the refractive index n2 of the second adhesive surface may be substantially the same as the refractive index n1 of the first adhesive surface. More specifically, the absolute value of the difference in refractive indices between the two adhesive surfaces, that is, |n1 - n2|, may be, for example, less than 0.05, or less than 0.03, or less than 0.01. The lower limit of |n1 - n2| may be 0.00 or greater than 0.00. The relative relationship between the refractive indices of the two adhesive surfaces may be n1 > n2, n1 < n2, or n1 = n2.

[0203] In other embodiments, the difference between the refractive index n1 of the first adhesive surface and the refractive index n2 of the second adhesive surface of the adhesive sheet, that is, nI-n2, may be, for example, greater than 0.00, may be 0.01 or more, may be 0.03 or more, may be 0.05 or more, may be O.10 or more, may be 0.15 or more, may be 0.20 or more, or may be 0.25 or more. The magnitude relationship between n1 and n2 may also be reversed. A double-sided adhesive sheet having different refractive indices between the first adhesive surface and the second adhesive surface can be realized, for example, in the following manner: in a double-sided adhesive sheet with a carrier substrate, first and second adhesive layers having different refractive indices are laminated on a non-peeling support substrate; the adhesive layer constituting the substrate-free double-sided adhesive sheet has a laminated structure of two or more sub-adhesive layers having different refractive indices from each other.

[0204] The adhesive layer of the adhesive sheet disclosed herein can be formed by applying (e.g., coating) an adhesive composition to a suitable surface and then curing the composition. The application of the adhesive composition can be carried out using conventional coating machines such as gravure roller coaters, reverse roller coaters, licking roller coaters, dip roller coaters, bar coaters, doctor blade coaters, and spray coaters.

[0205] The adhesive layer of the adhesive sheet disclosed herein can be either a post-curing adhesive layer or a non-post-curing adhesive layer. Here, a post-curing adhesive layer refers to an adhesive layer that can be further cured by irradiation with heat or active energy rays (e.g., ultraviolet light). Examples of post-curing adhesive layers include adhesive layers with unreacted olefinic unsaturated groups on the side chains of a base polymer (e.g., an acrylic polymer (A)) and adhesive layers containing unreacted polyfunctional monomers. In some embodiments, the adhesive layer preferably does not have post-curing properties. An adhesive layer without post-curing properties does not produce dimensional changes associated with post-curing reactions (i.e., good dimensional stability), thus easily suppressing warping of the adhesive sheet or the substrate to which it is adhered. It is also advantageous from the viewpoint of suppressing optical distortion of the adhesive layer when no dimensional changes (e.g., curing shrinkage) occur due to post-curing.

[0206] The thickness of the adhesive layer is not particularly limited, and can be, for example, 3 μm or more. In some embodiments, the thickness of the adhesive layer can be, for example, 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 85 μm or more. Furthermore, in some embodiments, the thickness of the adhesive layer can be, for example, less than 300 μm, less than 250 μm, less than 200 μm, less than 150 μm, or less than 120 μm. When the thickness of the adhesive layer is not too large, it can be advantageous from the viewpoint of thinning the adhesive sheet. The technology disclosed herein can preferably be implemented with the thickness of the adhesive layer in the range of 3 μm to 200 μm (more preferably 5 μm to 100 μm). It should be noted that in the case of an adhesive sheet having a first adhesive layer and a second adhesive layer on the first and second surfaces of a substrate, the aforementioned thickness of the adhesive layer can be at least the thickness of the first adhesive layer. The thickness of the second adhesive layer can also be selected from the same range. In addition, in a substrate-free double-sided adhesive sheet formed by an adhesive layer, the thickness of the adhesive layer is the thickness of the adhesive sheet.

[0207] (Total light transmittance)

[0208] In the technology disclosed herein, a total light transmittance of the adhesive layer is suitable, for example, greater than 50%, preferably greater than 70%. In some preferred embodiments, the total light transmittance of the adhered material is 85% or more, preferably 86% or more, more preferably 88% or more, even more preferably 90% or more (e.g., greater than 90.0%), and may also be 90.5% or more. Such adhesive sheets with highly transparent adhesive layers, whether in a substrate-containing or substrate-free configuration, are preferably used in applications requiring high light transmittance (e.g., optical applications) and applications requiring good visual identification of the adhered material's properties through the adhesive sheet. In some embodiments, the total light transmittance of the adhesive layer may be 93% or more, or may be 95% or more. The upper limit of the total light transmittance is theoretically the value obtained by subtracting the light loss (Fresnel loss) caused by reflection at the air interface from 100%, and practically may be about 98% or less, about 96% or less, or about 95% or less. In some methods, considering refractive index and adhesive properties, the total light transmittance of the adhesive layer can be about 94%, about 93%, or about 92% or less. The total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. As a transmittance meter, the trade name "HAZEMETER HM-150" manufactured by Murakami Color Technology Research Institute or its equivalent can be used. More specifically, for example, the total light transmittance of the adhesive layer can be measured according to the embodiments described later. The total light transmittance of the adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc., of the adhesive layer.

[0209] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet with a substrate on which a first adhesive layer and a second adhesive layer are fixedly laminated, it is preferable that at least the first adhesive layer satisfies any of the aforementioned total light transmittance. In the case of use where light passes through the thickness direction of the adhesive sheet, it is preferable that both the first adhesive layer and the second adhesive layer satisfy any of the aforementioned total light transmittance. The relative relationship of the total light transmittance of the two adhesive layers can be: first adhesive layer > second adhesive layer, first adhesive layer < second adhesive layer, or first adhesive layer = second adhesive layer.

[0210] (Haze value)

[0211] In some embodiments, the haze value of the adhesive layer constituting the adhesive sheet can be, for example, 5.0% or less, preferably 3.0% or less (e.g., 2.0% or less), more preferably 1.0% or less, and even more preferably 0.9% or less. Adhesive sheets with such highly transparent adhesive layers, whether in a substrate-containing or substrate-free configuration, are preferably used for applications requiring high light transmittance (e.g., optical applications) and applications requiring good visual identification of the adhered objects through the adhesive sheet. In some embodiments, the haze value of the adhesive layer can be 0.8% or less, 0.5% or less, or 0.3% or less. There is no particular limitation on the lower limit of the haze value of the adhesive layer; from the viewpoint of improving transparency, a lower haze value is more preferred. On the other hand, in some embodiments, considering refractive index and adhesive properties, the haze value can be, for example, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more. These haze values ​​related to the adhesive layer can also preferably be applied to the haze value of the adhesive sheet when the technology disclosed herein is implemented in the form of a substrate-free adhesive sheet (typically an adhesive sheet formed of an adhesive layer).

[0212] Here, "haze value" refers to the ratio of diffuse transmitted light to total transmitted light when visible light is irradiated onto the object being measured. It is also called turbidity. The haze value can be expressed by the following formula.

[0213] Th(%)=Td / Tt×100

[0214] In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total transmittance. The haze value can be measured according to the method described in the examples below. The haze value of the adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc. of the adhesive layer.

[0215] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet with a substrate on which a first adhesive layer and a second adhesive layer are fixedly laminated, at least the first adhesive layer needs to satisfy any of the aforementioned haze values, while the haze value of the second adhesive layer is not particularly limited. In the application method where light passes through the thickness direction of the adhesive sheet, it is preferable that the haze value of the second adhesive layer satisfies any of the aforementioned haze values ​​of the first adhesive layer. The relative relationship between the haze values ​​of the two adhesive layers can be that the first adhesive layer > the second adhesive layer, the first adhesive layer < the second adhesive layer, or the first adhesive layer = the second adhesive layer.

[0216] (Surface smoothness of the adhesive surface)

[0217] In some of the adhesive sheets disclosed herein, the adhesive surface of the adhesive sheet preferably has high surface smoothness.

[0218] For example, the arithmetic mean roughness Ra of the aforementioned adhesive surface is preferably limited to a predetermined value or less. A configuration with an adhesive surface designed to have a low arithmetic mean roughness Ra is preferred from the viewpoint of optical homogeneity. By limiting the arithmetic mean roughness Ra, for example in applications where light is extracted through the aforementioned adhesive surface (such as an adhesive sheet arranged on the viewpoint side of a light-emitting device, closer to the self-emitting element), it is possible to suppress uneven brightness caused by the surface condition of the adhesive layer. A low arithmetic mean roughness Ra of the adhesive surface is also advantageous for suppressing optical distortion, and the suppression of optical distortion also contributes to improving optical homogeneity. When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that at least the arithmetic mean roughness Ra of the first adhesive surface is limited to a predetermined value or less, and more preferably that the arithmetic mean roughness Ra of both adhesive surfaces is limited to a predetermined value or less. By making each adhesive surface of the double-sided adhesive sheet have high surface smoothness, it is preferable to achieve adhesion with excellent optical homogeneity.

[0219] In some embodiments, the arithmetic mean roughness Ra of the adhesive surface is preferably about 70 nm or less, more preferably about 65 nm or less, even more preferably about 55 nm or less, and may be less than 50 nm, less than 45 nm, or less than 40 nm. From the viewpoint of production efficiency, in some embodiments, the arithmetic mean roughness Ra of the adhesive surface of the adhesive sheet may be, for example, about 10 nm or more, about 20 nm or more, or about 30 nm or more (e.g., about 40 nm or more). In embodiments where the adhesive sheet has a first adhesive surface and a second adhesive surface, the arithmetic mean roughness Ra of the first adhesive surface and the arithmetic mean roughness Ra of the second adhesive surface may be the same or different.

[0220] Furthermore, for example, the maximum height Rz of the aforementioned adhesive surface is preferably limited to a predetermined value or less. A configuration with an adhesive surface designed to have a low maximum height Rz is preferred from the viewpoint of optical homogeneity. By limiting the maximum height Rz, for example in the method of extracting light through the aforementioned adhesive surface as described above, it is possible to suppress the generation of brightness unevenness caused by the surface state of the adhesive layer. A low maximum height Rz of the adhesive surface is also advantageous for suppressing optical distortion. When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that at least the maximum height Rz of the first adhesive surface is limited to a predetermined value or less, and more preferably that the maximum height Rz of both adhesive surfaces is limited to a predetermined value or less. By making each adhesive surface of the double-sided adhesive sheet have high surface smoothness, it is preferable to achieve adhesion with excellent optical homogeneity.

[0221] 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, particularly preferably about 400 nm or less, and may be less than 350 nm, less than 300 nm, or less than 250 nm. From the viewpoint of production efficiency, in some embodiments, the maximum height Rz of the adhesive surface of the adhesive sheet may be, for example, about 10 nm or more, about 50 nm or more, about 100 nm or more, or about 200 nm or more. In embodiments where the adhesive sheet has a first adhesive surface and a second adhesive surface, the maximum height Rz of the first adhesive surface and the maximum height Rz of the second adhesive surface may be the same or different.

[0222] The arithmetic mean roughness Ra and maximum height Rz of the bonding surface are measured using a non-contact surface roughness measuring device. As a non-contact surface roughness measuring device, an optical interferometry surface roughness measuring device can be used, for example, a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO) or its equivalent. Specifically, the arithmetic mean roughness Ra and maximum height Rz can be measured, for example, by setting the measurement operation and measurement conditions in a manner that yields equivalent or corresponding results to those obtained using the following measurement method.

[0223] That is, the surface shape of the sample was measured under the following conditions using a three-dimensional optical profilometer (trade name "NewView7300", manufactured by ZYGO) at 23°C and 50% RH. Based on the measured data, the arithmetic surface roughness Ra was calculated according to JIS B0601-2001. Regarding the maximum height Rz, it was calculated as the sum of the height Rp of the highest peak above the average line of the roughness curve and the depth Rv of the deepest valley below the average line, based on the data obtained from the above measurements (roughness curve). Ra and Rz were measured five times (i.e., N=5), and their average values ​​were used.

[0224] The sample used for the above-mentioned test can be prepared by cutting the adhesive layer of the test object or the adhesive sheet containing the adhesive layer into a size of approximately 150 mm in length and 50 mm in width. With the adhesive surface protected by a release liner, the release liner is gently peeled off (for example, at a stretching speed of 300 mm / min and a peeling angle of 180°) to expose the adhesive surface. Ideally, the test should be performed after allowing the sample to stand for approximately 30 minutes after the adhesive surface has been exposed.

[0225] [Measurement Conditions]

[0226] Measurement area: 5.62mm × 4.22mm

[0227] (Objective lens: 2.5x, internal lens: 0.5x)

[0228] Parsing mode:

[0229] Remove: Cylinder

[0230] Data Fill: ON (Max: 25)

[0231] Remove Spikes: ON (xRMS: 1)

[0232] Filter: OFF

[0233] The arithmetic mean roughness Ra and maximum height Rz of the adhesive surface can be adjusted by the composition and properties (viscosity, leveling properties, etc.) of the adhesive composition used in the formation of the adhesive layer, and the properties of the surface of the release liner protecting the adhesive surface (release surface).

[0234] (Storage modulus G')

[0235] In the adhesive sheet disclosed herein, the storage modulus G' (hereinafter also referred to as "storage modulus G'(25)") of the adhesive constituting the adhesive layer at 25°C can be appropriately set according to the purpose of use, method of use, etc., and is not limited to a specific range. The storage modulus G'(25) of the adhesive can be, for example, about 700 kPa or less. In some embodiments, from the viewpoint of ease of adhesion to the adhered object, it is advantageous for the storage modulus G'(25) of the adhesive to be about 600 kPa or less, preferably 500 kPa or less, and more preferably 400 kPa or less (e.g., 350 kPa or less). In some embodiments, from the viewpoint of improving the softness of the adhesive in the room temperature range (e.g., 25°C) and making it easier to adhere to the adhered object, it is advantageous for the storage modulus G'(25) of the adhesive to be about 330 kPa or less, preferably 300 kPa or less. In some approaches that prioritize adhesion and flexibility in the room temperature range, the storage modulus G'(25) of the adhesive can be, for example, below 270 kPa or below 250 kPa, below 200 kPa is advantageous, preferably below 180 kPa, and more preferably below 160 kPa (e.g., below 140 kPa). In some approaches, the storage modulus G'(25) of the adhesive can be below 100 kPa or below 90 kPa. There is no particular limitation on the lower limit of the storage modulus G'(25) of the adhesive; from the viewpoint of processability and handling, it can be, for example, above 30 kPa, above 50 kPa, or above 70 kPa. In some approaches, considering the high refractive index, the storage modulus G'(25) can be above 100 kPa, above 150 kPa, above 200 kPa, above 250 kPa, or above 300 kPa.

[0236] In the adhesive sheet disclosed herein, the storage modulus G' (hereinafter also referred to as "storage modulus G'(50)") of the adhesive constituting the adhesive layer at 50°C is not particularly limited, and may be, for example, less than 100 kPa.

[0237] In some methods, a storage modulus G'(50) below 60 kPa is appropriate, preferably below 40 kPa, and more preferably below 38 kPa (e.g., below 36 kPa). Adhesives with such a limited storage modulus G'(50) can readily improve their adhesion to the substrate by appropriate heating as needed, thereby enhancing the bonding strength of the substrate. There is no particular limitation on the lower limit of the storage modulus G'(50) of the adhesive.

[0238] In some ways, from the viewpoint of the heat resistance properties of the adhesive, the storage modulus G'(50) can be, for example, 10 kPa or more, 15 kPa or more, 20 kPa or more, or 23 kPa or more.

[0239] In some of the adhesives disclosed herein, the adhesive preferably satisfies at least one of the following conditions:

[0240] (a) The energy storage modulus G'(25) at 25°C is 350 kPa or less (preferably less than 200 kPa, for example, less than 180 kPa); and

[0241] (b) The energy storage modulus G'(50) at 50°C is less than 60 kPa (preferably less than 50 kPa, more preferably less than 40 kPa, for example less than 38 kPa).

[0242] From the viewpoint of adhesion to the adherend at room temperature (e.g., 25°C), an adhesive that at least satisfies condition (a) above is preferred. An adhesive that at least satisfies condition (b) above is preferred because its adhesion to the adherend can be easily improved by heating it to a temperature slightly higher than room temperature. For an adhesive that does not satisfy condition (a) but satisfies condition (b) above, it exhibits good reworkability (re-adhesion) in the initial application stage at room temperature and can be used as a heat-activated adhesive that can effectively improve its peel strength from the adherend by heating it to a temperature slightly higher than room temperature. This heat activation can be achieved by heating the adhesive to a temperature slightly higher than room temperature during adhesion to the adherend. This temperature slightly higher than room temperature is, for example, around 60°C or less, preferably around 55°C or less (e.g., around 50°C or less).

[0243] In some embodiments of the adhesive sheet disclosed herein, the ratio of the storage modulus G'(50) [kPa] of the adhesive constituting the adhesive layer to the storage modulus G'(25) [kPa], i.e., the storage modulus ratio G'(50) / G'(25), is, for example, 70% or less, or 40% or less, or 30% or less, or 20% or less. Adhesives with a small G'(50) / G'(25) ratio are suitable for use as the aforementioned heat-activated adhesives. There is no particular limitation on the lower limit of G'(50) / G'(25). For example, G'(50) / G'(25) is 5% or more, and from the viewpoint of the heat resistance properties of the adhesive, it is preferably 10% or more, or 12% or more, or 15% or more.

[0244] Storage moduli G'(25) and G'(50) can be determined by dynamic viscoelasticity measurement, and G'(50) / G'(25) can be calculated from the results. Dynamic viscoelasticity measurement can be performed using a commercially available dynamic viscoelasticity measuring device by conventional methods, such as the "Advanced Rheometric Expansion System (ARES)" or its equivalent manufactured by TA Instruments, under the following measurement conditions. As the sample for measurement, a sample with a thickness of approximately 1.5 mm is prepared by laminating the adhesive layer of the object being evaluated as needed.

[0245] [Measurement Conditions]

[0246] Deformation mode: Torsion

[0247] Measurement frequency: 1Hz

[0248] Heating rate: 5℃ / minute

[0249] Shape: Parallel plate

[0250] The storage modulus G'(25), G'(50) and storage modulus ratio of the adhesive layer can be determined by selecting the composition of the monomer components constituting the acrylic polymer (A) (e.g., the type and content of monomer (m1), whether or not to use the crosslinking agent, the type and amount used, and the aforementioned additives (H). RO The selection of whether to use plasticizing materials, the type and amount of plasticizing materials used, etc. can be adjusted. For example, as a monomer (m1), based on the use of the first monomer as the main component of the first monomer (m1), by using a second monomer with a different chemical structure from the first monomer in combination with the first monomer in a smaller amount, it is possible to reduce G' (50) and reduce G' (50) / G' (25) based on the case where the first monomer is used alone as a monomer (m1).

[0251] When the adhesive sheet disclosed herein is a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface (e.g., a double-sided adhesive sheet with a substrate having a first adhesive layer and a second adhesive layer, or a substrate-free double-sided adhesive sheet formed by laminating a sub-adhesive layer constituting the first adhesive surface and a sub-adhesive layer constituting the second adhesive surface without sandwiching a non-adhesive substrate, etc., and other similar descriptions are also applicable), the aforementioned storage modulus G'(25), G'(50), and storage modulus ratio can be applied at least to the adhesive layer constituting the first adhesive surface, and preferably to both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface. The storage modulus G' of the adhesive layer constituting the first adhesive surface and the storage modulus G' of the adhesive layer constituting the second adhesive surface can be the same or different.

[0252] In some embodiments of the technology disclosed herein, the peak temperature of the adhesive constituting the adhesive layer's tanδ is preferably above approximately -50°C, and more preferably below approximately 50°C. Here, the adhesive's tanδ (loss tangent) refers to the ratio of the adhesive's loss modulus G” to its storage modulus G'. That is, tanδ = G” / G'. The adhesive's tanδ can be determined as follows: A disc-shaped adhesive sample with a thickness of approximately 2 mm and a diameter of 7.9 mm is held between parallel plates. Using a viscoelastic testing apparatus, a temperature dispersion test of the adhesive is conducted in shear mode under conditions of a measurement temperature range of -60°C to 60°C and a heating rate of 5°C / min, while applying a shear strain at a frequency of 1 Hz. Based on the storage modulus G' (Pa) and loss modulus G” (Pa) at this time, the tanδ is determined using the following formula: tanδ = G” / G'. The peak temperature of the adhesive's tanδ (hereinafter sometimes referred to as Tpeak) can be determined from the shift of tanδ within the aforementioned temperature range. As a viscoelasticity testing apparatus, ARES or its equivalent manufactured by TA Instruments can be used.

[0253] In some methods, it is advantageous for the adhesive's Tpeak to be below 45°C or 35°C, preferably below 30°C (e.g., below 25°C), and it can be below 20°C or even below 15°C. Adhesives with lower Tpeaks tend to readily achieve good initial adhesion and bonding at room temperature. On the other hand, from the viewpoint of imparting appropriate cohesion to the adhesive, it is preferable that the adhesive's Tpeak is not too low, and it also tends to be suitable for achieving a high refractive index. From this viewpoint, in some methods, the adhesive's Tpeak is, for example, above -40°C, above -30°C, above -20°C, above -5°C, above 5°C, above 15°C, and further above 25°C. Adhesives with higher Tpeaks are preferred when the adhesive and the adherends are heated to a temperature slightly above room temperature as needed during bonding. The Tpeak of the adhesive can be determined by the selection of the adhesive's composition (e.g., the composition of the monomer components constituting the acrylic polymer (A), the additives (H... RO Adjustments are made based on factors such as whether plasticizing materials are used, the type of plasticizer, and the amount used.

[0254] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, the Tpeak of the aforementioned adhesive is preferably applied at least to the adhesive layer constituting the first adhesive surface, and more preferably to both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface. The Tpeak of the adhesive layer constituting the first adhesive surface and the Tpeak of the adhesive layer constituting the second adhesive surface may be the same or different.

[0255] (Water absorption rate)

[0256] In some embodiments of the adhesive sheet disclosed herein, the water absorption rate of the adhesive layer constituting the adhesive sheet is preferably limited to a specified value or below. By limiting the water absorption rate of the adhesive layer, dimensional changes in the adhesive layer caused by variations in the amount of moisture in the adhesive layer (e.g., absorption and release of moisture from the environment) tend to be suppressed. This suppresses warping of the adhesive sheet or the adhered object to which the adhesive sheet is bonded, caused by inconsistencies in the dimensional changes of the adhesive layer and adjacent layers (which may be a support substrate, release liner, adhered object, etc.). From the viewpoint of maintaining the flatness, transparency, refractive index, etc., of the adhesive layer to a certain level, it is also preferable to suppress variations in the amount of moisture in the adhesive layer. Furthermore, adhesive layers with low water absorption rates are suitable for use as adhesive sheets in components or articles containing moisture-sensitive elements, such as organic EL elements, because they do not easily absorb or retain moisture.

[0257] In some embodiments, a water absorption rate of the adhesive layer of about 1.0% or less is suitable, preferably 0.7% or less, more preferably 0.5% or less (e.g., less than 0.5%), and can be 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less. There is no particular limitation on the lower limit of the water absorption rate of the adhesive layer; from a practical point of view, considering both adhesive properties, it can be, for example, 0.01% or more, 0.05% or more, 0.1% or more, or 0.15% or more. When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that the water absorption rate of at least the adhesive layer constituting the first adhesive surface is limited to a specified value or less. From the viewpoint of obtaining a higher effect, it is more preferable that the water absorption rates of both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface are limited to a specified value or less.

[0258] It should be noted that the water absorption rate (also known as moisture content) of the adhesive layer is determined by the following method.

[0259] [Moisture content determination]

[0260] Cut a 4cm x 5cm (area: 20cm²) section from the adhesive layer of the object being evaluated, along with two release liner sheets placed on one and the other sides. 2 The release liner on one side of the adhesive layer was removed and adhered to a pre-weighed aluminum foil. Next, the release liner on the other side of the adhesive layer was placed in a constant temperature and humidity bath at 60°C and 90% relative humidity for 72 hours. The resulting test piece, consisting of the adhesive layer and aluminum foil, was weighed and then the moisture content was determined using a moisture meter (Mitsubishi Chemical Analytech CA-200) equipped with a heating vaporization device (Mitsubishi Chemical Analytech VA-200) under the following conditions via Karl Fischer electrostatic titration.

[0261] Anode solution: AQUAMICRON AKX (manufactured by Mitsubishi Chemical)

[0262] Cathodic solution: AQUAMICRON CXU (manufactured by Mitsubishi Chemical)

[0263] Heating and vaporization temperature: 150℃

[0264] (Gel ratio)

[0265] The gelation rate of the adhesive layer is appropriately set according to the intended use and method of application, and is not limited to a specific range. For example, a gelation rate of about 99% or less, or about 97% or less, is suitable. From the viewpoint of easily and appropriately balancing high refractive index and adhesive properties, in some preferred embodiments, the gelation rate is about 95% or less, and more preferably about 92% or less (e.g., about 90% or less). From the viewpoint of appropriately accommodating the unevenness that may exist on the surface of the adhered object (e.g., uneven structures provided in a light-emitting device for the purpose of improving light extraction efficiency) and achieving good adhesion, a gelation rate that is not too high is also preferred. In some embodiments, the gelation rate may be about 88% or less, about 75% or less, or about 65% or less. Furthermore, from the viewpoint of imparting appropriate cohesion to the adhesive and appropriately exhibiting adhesive properties, a gelation rate of the adhesive layer of, for example, about 10% or more, about 20% or more, or about 30% or more, is suitable. From the viewpoint of the adhesive layer's resistance to deformation (preventing overflow due to pressure, air bubbles due to the incorporation of foreign matter, etc.), the gelation rate is preferably about 30% or more, more preferably about 40% or more, and can be about 45% or more, about 50% or more, about 65% or more, or about 75% or more. The gelation rate of the adhesive sheet (typically a substrate-free adhesive sheet) is also preferably set within the ranges exemplified above. The gelation rate can be adjusted by the molecular weight, molecular structure, concentration, degree of crosslinking, etc., of the acrylic polymer (A). The gelation rate is measured by the following method.

[0266] [Determination of gelation rate]

[0267] A specified amount of adhesive sample (weight Wg1) was wrapped in a purse-shaped pouch using a porous polytetrafluoroethylene membrane (weight Wg2) with an average pore size of 0.2 μm, and the opening was secured with kite string (weight Wg3). The porous polytetrafluoroethylene (PTFE) membrane used was the product "NITOFLON (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or an equivalent product available from Nitto Denko Corporation.

[0268] The package was immersed in a sufficient amount of ethyl acetate and kept at room temperature (typically 23°C) for 7 days to allow only the sol component of the adhesive to dissolve to the outside of the membrane. The package was then removed, and the ethyl acetate adhering to its outer surface was wiped off. The package was then dried at 130°C for 2 hours, and its weight (Wg4) was measured. The gelation rate of the adhesive layer was calculated by substituting the values ​​into the following formula.

[0269] Gelation rate (%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0270] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, the aforementioned gelation rate applies at least to the adhesive layer constituting the first adhesive surface, and preferably to both the adhesive layer constituting the first adhesive surface and the adhesive layer constituting the second adhesive surface. The gelation rate of the adhesive layer constituting the first adhesive surface and the gelation rate of the adhesive layer constituting the second adhesive surface may be the same or different.

[0271] (Peel strength)

[0272] In some embodiments of the adhesive sheet disclosed herein, it is suitable for the adhesive sheet to have a peel strength to the glass plate of about 1.0 N / 25 mm or more (e.g., 1.5 N / 25 mm or more), preferably 2 N / 25 mm or more, more preferably 3 N / 25 mm or more, and can be 4 N / 25 mm or more, 6 N / 25 mm or more, 8 N / 25 mm or more, 10 N / 25 mm or more, or 12 N / 25 mm or more. There is no particular limitation on the upper limit of the peel strength; for example, it can be 30 N / 25 mm or less, 25 N / 25 mm or less, or 20 N / 25 mm or less.

[0273] Here, the peel strength can be determined as follows: The adhesive is pressed onto an alkaline glass plate (the substrate), placed at 23°C and 50% RH for 30 minutes, then immersed in a pressure degassing apparatus (autoclave) for 30 minutes at 50°C and 0.5 MPa. After being placed at 23°C and 50% RH for 24 hours, the 180° peel adhesion is measured at a peel angle of 180 degrees and a tensile speed of 300 mm / min. During the measurement, if necessary, a suitable lining material (e.g., a polyethylene terephthalate (PET) film with a thickness of approximately 25 μm to 50 μm) can be applied to the adhesive sheet to reinforce it. More specifically, the peel strength can be measured according to the method described in the examples below.

[0274] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, in some embodiments, the aforementioned peel strength preferably applies at least to the first adhesive surface, and more preferably to both the first and second adhesive surfaces. 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.

[0275] (Support substrate)

[0276] Some adhesive sheets can be in the form of a substrate-supported adhesive sheet with an adhesive layer on one or both sides of the supporting substrate. The material of the supporting substrate is not particularly limited and can be appropriately selected according to the purpose and method of use of the adhesive sheet. Non-limiting examples of usable substrates include polyolefin films with polyolefins as the main component, such as polypropylene (PP) and ethylene-propylene copolymer; polyester films with polyesters as the main component, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); and polyvinyl chloride films with polyvinyl chloride as the main component; foamed sheets formed from foams such as polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; woven and nonwoven fabrics based on various fibrous materials (such as natural fibers like hemp and cotton, synthetic fibers like polyester and vinylon, and semi-synthetic fibers like cellulose acetate); paper types such as Japanese paper, premium paper, kraft paper, and crepe paper; and metal foils such as aluminum foil and copper foil; etc. It can be a substrate composed of these composite materials. Examples of such composite substrates include substrates with structures formed by laminating metal foil and the aforementioned plastic film, and plastic substrates reinforced with inorganic fibers such as glass cloth.

[0277] In some embodiments, various film substrates can be preferably used. These film substrates can be porous substrates such as foamed films or nonwoven sheets, or non-porous substrates, or substrates with a structure consisting of laminated porous and non-porous layers. In some embodiments, a substrate comprising a self-supporting or independent resin film capable of independently maintaining its shape can be preferably used as the base film. Here, "resin film" refers to a non-porous structure, typically a substantially bubble-free (non-porous) resin film. Therefore, the resin film is a concept distinct from foamed films and nonwoven fabrics. As the resin film, a self-supporting or independent film capable of independently maintaining its shape can be preferably used. The resin film can be a single-layer structure or a multi-layer structure with two or more layers (e.g., a three-layer structure).

[0278] Materials constituting resin films include, for example, polyester resins with polyesters as the main component, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyolefin resins with polyolefins as the main component, such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as triacetyl cellulose; acetate resins; polysulfone resins; polyethersulfone resins; polycarbonate resins; nylon 6; nylon 66; some aromatic polyamides and other polyamide (PA) resins; and polyimide (…). Cyclic polyolefin resins such as PI (polyimide) resins, transparent polyimide resins, polyamide-imide (PAI), polyether ether ketone (PEEK), polyether sulfone (PES), and norbornene resins; (meth)acrylic resins; polyvinyl chloride resins; polyvinylidene chloride resins; polystyrene resins; polyvinyl alcohol resins; ethylene-vinyl acetate copolymer resins; ethylene-vinyl alcohol copolymer resins; polyarylate resins; polyphenylene sulfide (PPS) resins; polyurethane (PU); ethylene-vinyl acetate copolymer (EVA); polytetrafluoroethylene (PTFE); and fluorinated polyimide resins.

[0279] The aforementioned resin film can be a film formed using a resin material containing only one such resin, or a film formed using a blend of two or more resin materials. The resin film can be unstretched or stretched (e.g., uniaxially or biaxially stretched). 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 / PE blend film, etc., are preferred. Examples of resin films preferred from the viewpoint of strength and dimensional stability include PET film, PEN film, PPS film, and PEEK film. From the viewpoint of ease of acquisition, PET film and PPS film are particularly preferred, with PET film being the most preferred.

[0280] In the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, lubricants, and antiblocking agents may be added as needed, without significantly impairing the effects of the present invention. The amount of additives added is not particularly limited and can be appropriately set according to the intended use of the adhesive sheet.

[0281] There are no particular limitations on the manufacturing method of resin films. For example, commonly known resin film forming methods such as extrusion molding, blow molding, T-die casting, and calendering can be appropriately used.

[0282] The aforementioned substrate may be substantially composed of such a base film. Alternatively, the aforementioned substrate may also include auxiliary layers in addition to the aforementioned base film. Examples of such auxiliary layers include optical property adjustment layers (e.g., coloring layers, anti-reflective layers), printing layers for imparting a desired appearance to the substrate, laminated layers, antistatic layers, primer layers, release layers, and other surface treatment layers.

[0283] In some embodiments, a light-transmitting substrate (hereinafter also referred to as a light-transmitting substrate) is preferably used as the supporting substrate. This allows for the formation of a light-transmitting adhesive sheet with a substrate. The total light transmittance of the light-transmitting substrate can be, for example, higher than 50%, or higher than 70%. In some preferred embodiments, the total light transmittance of the supporting substrate is 80% or higher, more preferably 90% or higher, and may also be 95% or higher (e.g., 95-100%). The aforementioned total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. The transmittance meter used is the Murakami Color Technology Research Institute's trade name "HAZEMETER HM-150" or its equivalent. A suitable example of the aforementioned light-transmitting substrate is a light-transmitting resin film. The aforementioned light-transmitting substrate can be an optical film.

[0284] The thickness of the substrate is not particularly limited and can be selected according to the intended use and application method of the adhesive sheet. For example, the substrate thickness can be 500 μm or less, but from the viewpoint of the adhesive sheet's processability and workability, it is preferably 300 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, or even 10 μm or less. A smaller substrate thickness tends to improve the ability to follow the surface shape of the adhered object. Furthermore, from the viewpoint of processability and workability, the substrate thickness can be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

[0285] For one side of the laminated adhesive layer in the substrate, conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and the formation of a primer-based coating can be performed as needed. Such surface treatments can be used to improve the anchoring of the adhesive layer to the substrate. The composition of the primer used in the formation of the primer coating is not particularly limited and can be appropriately selected from known compositions. The thickness of the primer coating is not particularly limited, but is typically suitable at around 0.01 μm to 1 μm, preferably around 0.1 μm to 1 μm. Other treatments that can be performed on the substrate as needed include antistatic layer formation treatment, coloring layer formation treatment, and printing treatment. These treatments can be applied individually or in combination.

[0286] When the adhesive sheet disclosed herein is in the form of an adhesive sheet with a substrate, the thickness of the adhesive sheet can be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, 120 μm or less, 75 μm or less, or 50 μm or less. Furthermore, from the viewpoint of processability, the thickness of the adhesive sheet can be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.

[0287] It should be noted that the thickness of the adhesive sheet refers to the thickness of the portion that is adhered to the object being bonded. For example, for Figure 1 The adhesive sheet 1 shown refers to the thickness from the first surface (adhesive surface) 10A of the adhesive layer to the second surface 20B of the support substrate, excluding the thickness of the release liner 30.

[0288] <Adhesive sheet with release liner>

[0289] The adhesive sheet disclosed herein can take the form of an adhesive article obtained by abutting the surface (adhesive surface) of an adhesive layer against the release surface of a release liner. Therefore, according to this specification, an adhesive sheet (adhesive article) with a release liner is provided, comprising: any of the adhesive sheets disclosed herein, and a release liner having a release surface abutting against the adhesive surface of the adhesive sheet.

[0290] There are no particular limitations on the release liner. For example, release liners with a release layer on the surface of the liner substrate, such as resin film or paper (which may be paper laminated with resins such as polyethylene), or release liners containing resin films made of low-adhesion materials such as fluoropolymers (polytetrafluoroethylene, etc.) or polyolefin resins (polyethylene, polypropylene, etc.) can be used. From the perspective of excellent surface smoothness, release liners with a release layer on the surface of the resin film used as the liner substrate, or release liners containing resin films made of low-adhesion materials, are preferred. As for the resin film, there are no particular limitations as long as it is a film that can protect the adhesive layer. Examples include polyethylene (PE) film, polypropylene (PP) film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, and ethylene-vinyl acetate copolymer film. In forming the aforementioned release layer, known release agents such as organosilicon-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.

[0291] <Application>

[0292] The adhesive sheet disclosed herein can be used to adhere to various substrates. The constituent materials of the substrates (substrate materials) are not particularly limited, but can include: for example, metallic materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, or alloys containing two or more of these; and resins such as polyimide resins, acrylic resins, polyether nitrile resins, polyethersulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (such as aramid resins), polyarylate resins, and fluorine resins. This includes various resin materials (typically plastic materials), such as resins, polycarbonate resins, cellulose polymers like diacetyl cellulose and triacetyl cellulose, vinyl butyral polymers, liquid crystal polymers, and carbon materials like graphene; metal oxides and mixtures thereof, such as alumina, zirconium oxide, titanium oxide, SiO2, ITO (indium tin oxide), and ATO (antimony-doped tin oxide); nitrides and their complexes, such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride, and indium nitride; and inorganic materials such as alkaline glass, alkali-free glass, quartz glass, borosilicate glass, and sapphire glass. The adhesive sheet disclosed herein can be used to adhere to components (e.g., optical components) whose surfaces are at least composed of the aforementioned materials.

[0293] The adhesive sheet disclosed herein can be used in a bonding method that does not require heating to a temperature range higher than room temperature (e.g., 20°C to 35°C) after being applied to the substrate. Furthermore, depending on the constituent materials of the adhesive sheet (e.g., the material of the substrate) and the type of substrate, heat treatment may be performed at least at any time after application to the substrate, at the moment of application, and before application, where permissible. Heat treatment may be performed for purposes such as improving the adhesion of the adhesive to the substrate and promoting bonding. Regarding the heat treatment temperature, it can be appropriately set within permissible limits, taking into account the surface condition of the substrate, etc., to obtain the desired effect, depending on the constituent materials of the adhesive sheet and the type of substrate; for example, it may be around 100°C or below, below 80°C, below 60°C, or below 50°C.

[0294] The component or material to which the adhesive sheet is bonded (for double-sided adhesive sheets, at least one of the adhered materials) can be translucent. In such adhered materials, the techniques disclosed herein readily provide the advantage of suppressing the reduction of optical properties (transparency, etc.) and increasing the refractive index. The total light transmittance of the aforementioned adhered material can, for example, be higher than 50%, or higher than 70%. In some preferred embodiments, the total light transmittance of the aforementioned adhered material is 80% or higher, more preferably 90% or higher, and even more preferably 95% or higher (e.g., 95-100%). The adhesive sheet disclosed herein can preferably be used to bond to an adhered material (e.g., an optical component) with a total light transmittance of a specified value or higher. The aforementioned total light transmittance is measured using a commercially available transmittance meter according to JIS K 7136:2000. The transmittance meter used is the Murakami Color Technology Research Institute's trade name "HAZEMETERHM-150" or an equivalent thereof.

[0295] The refractive index of the adhesive layer and the refractive index of the adherend can be the same or different. For example, by relatively increasing the refractive index of the adhesive layer compared to the refractive index of the adherend, light incident on the adhesive layer at an angle below the critical angle from the adherend side can be refracted on the front side, increasing the front brightness. In this case, the refractive index of the adherend can be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, or even less than 1.45; and, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. Alternatively, by using an adherend with a relatively high refractive index compared to the adhesive layer, light incident on the adherend from the adhesive layer side can be refracted on the front side, increasing the front brightness. In this case, the refractive index of the adherend can be, for example, 1.60 or more, 1.65 or more, or 1.70 or more; and, for example, 3.00 or less, or 2.50 or less, or 2.00 or less. On the other hand, by reducing the refractive index difference between the adhesive layer and the adherend, light reflection at the interface can be suppressed. At this point, the refractive index of the adhered material can be approximately 1.55–1.80, 1.55–1.75, or 1.60–1.70. The refractive index of the adhered material can be determined using the same method as that used for the refractive index of the adhesive.

[0296] In some preferred embodiments, the adherend may have any of the aforementioned refractive indices and any of the aforementioned total light transmittance. The effects of the techniques disclosed herein can be particularly preferably achieved in the manner of adhesion to such an adherend.

[0297] As an example of preferred applications, optical applications can be cited. More specifically, for example, the adhesive sheet disclosed herein can be preferably used for optical applications such as bonding optical components (for bonding optical components) and manufacturing articles using the aforementioned optical components (optical articles).

[0298] The aforementioned optical components refer to components possessing optical properties (such as polarization, refraction, scattering, reflection, transmission, absorption, diffraction, rotation, and visual recognition). There is no particular limitation on the term "optical component" as long as it possesses optical properties. Examples include components constituting display devices (image display devices), input devices, and other equipment (optical devices), or components used in these devices. Examples include polarizing plates, wavelength plates, phase retardation plates, optical compensation films, brightness-enhancing films, light guide plates, reflective films, anti-reflective films, hard-coated (HC) films, impact-absorbing films, anti-fouling films, photochromic films, dimming films, transparent conductive films (ITO films), exterior films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and components further laminated with these (sometimes collectively referred to as "functional films"). It should be noted that the terms "plate" and "film" mentioned above each include plate-like, film-like, and sheet-like forms. For example, "polarizing film" includes "polarizing plate" and "polarizing sheet," and "light guide plate" includes "light guide film" and "light guide sheet." In addition, the term "polarizing plate" mentioned above includes circular polarizing plate.

[0299] Examples of display devices include liquid crystal displays, organic EL (electroluminescent) displays, micro LEDs (μLEDs), mini LEDs, PDPs (plasma display panels), and electronic paper. Additionally, examples of input devices include touch panels.

[0300] The term "optical component" is not particularly limited, and examples include components formed from glass, acrylic resins, polycarbonate, polyethylene terephthalate, metal films, etc. (e.g., sheet-like, film-like, plate-like components). It should be noted that "optical component" in this specification also includes components that maintain the visual legibility of the display device and input device and serve decorative and protective functions (such as outer films, decorative films, surface protective films, etc.).

[0301] The techniques disclosed herein are preferably used, for example, to bond optical thin films, such as thin films and fluorescent thin films, which have one or more functions of light transmission, reflection, diffusion, waveguide, light collection, and diffraction to other optical components (which may be other optical thin films). In the bonding of optical thin films with at least one function of light waveguide, light collection, and diffraction, it is ideal for the bonding layer to have an overall high refractive index, which is a preferred application of the techniques disclosed herein.

[0302] The adhesives disclosed herein are preferably used for bonding optical films such as light guide films, diffusion films, fluorescent films, color-matching films, prism sheets, lens-shaped films, and microlens array films. In these applications, from the perspective of miniaturization and high performance of optical components, there is a demand for thinner designs and improved light extraction efficiency. The adhesives disclosed herein are preferred as adhesives capable of meeting these requirements. More specifically, for example, in the bonding of light guide films and diffusion films, adjusting the refractive index of the adhesive layer as the bonding layer (e.g., increasing the refractive index) can contribute to thinning. In the bonding of fluorescent films, appropriately adjusting the refractive index difference between the phosphor and the adhesive can improve light extraction efficiency (which can also be considered as luminous efficiency). In the bonding of color-matching films, appropriately adjusting the refractive index of the adhesive to have a small refractive index difference with the color-matching pigment can reduce scattering components and contribute to improved light transmittance. In the bonding of prism sheets, lens-shaped films, and microlens array films, appropriately adjusting the refractive index of the adhesive can control light diffraction and contribute to improved brightness and / or viewing angle.

[0303] The adhesive sheet disclosed herein is preferably used by adhering it to a high-refractive-index substrate (which may be a high-refractive-index layer, component, etc.) to suppress interfacial reflection with the substrate. As described above, the adhesive sheet used in this manner preferably has a small refractive index difference with the substrate and high adhesion at the interface with the substrate. Furthermore, from the viewpoint of improving the uniformity of appearance, it is preferable that the thickness uniformity of the adhesive layer is high, for example, it is preferable that the surface smoothness of the adhesive surface is high. When the thickness of the high-refractive-index substrate is small (e.g., 5 μm or less, 4 μm or less, or 2 μm or less), suppressing reflection at the interface is particularly meaningful from the viewpoint of suppressing coloring and color unevenness caused by interference of reflected light. As an example of this usage, a method for bonding the polarizing element to the first retardation layer and / or the first retardation layer to the second retardation layer can be cited in a polarizing plate with a retardation layer comprising a polarizing element, a first retardation layer, and a second retardation layer in sequence.

[0304] Furthermore, the adhesive sheet disclosed herein is suitable for high refractive index applications, and therefore can preferably be used by bonding it to a light-emitting layer (e.g., a high-refractive-index light-emitting layer mainly composed of inorganic materials) of a photonic semiconductor. By reducing the refractive index difference between the light-emitting layer and the adhesive layer, reflection at their interface can be suppressed, and light extraction efficiency can be improved. The adhesive sheet used in this manner preferably has an adhesive layer with a high refractive index. Additionally, from the viewpoint of preventing deterioration of the self-emissive element due to moisture, a low water absorption rate of the adhesive layer is preferred. From the viewpoint of improving brightness, a low-coloring adhesive sheet is preferred. This is also advantageous from the viewpoint of suppressing unintentional coloring caused by the adhesive sheet.

[0305] The adhesive disclosed herein can be used preferably as a coating layer covering the lens surface, a bonding layer to a component (e.g., a microlens constituting a microlens array film, a camera microlens, etc.) in microlenses and other lens components used as constituent parts of cameras, light-emitting devices, etc., as well as a filler layer filling the space between the lens surface and the component. The adhesive disclosed herein is suitable for high refractive index applications, thus reducing the refractive index difference even with high refractive index lenses (e.g., lenses made of high refractive index resin, lenses with a surface layer made of high refractive index resin). This is advantageous from the viewpoint of thinning the lens and the article containing the lens, and also contributes to the suppression of aberrations and the improvement of the Abbe number. The adhesive disclosed herein can also be used itself as a lens resin, for example, by filling recesses or gaps in suitable transparent components.

[0306] There are no particular limitations on the method of bonding optical components using the adhesive sheet disclosed herein. For example, it can be (1) bonding optical components to each other using the adhesive sheet disclosed herein, (2) bonding optical components to components other than optical components using the adhesive sheet disclosed herein, or (3) bonding the adhesive sheet disclosed herein to an optical component or a component other than an optical component. It should be noted that in the above-mentioned (3) method, the adhesive sheet in the form of containing an optical component can be, for example, an adhesive sheet in the form of an optical component (e.g., an optical film) as a support. Such an adhesive sheet in the form of containing an optical component as a support can also be regarded as an adhesive optical component (e.g., an adhesive optical film). In addition, when the adhesive sheet disclosed herein is an adhesive sheet of the type having a support and the above-mentioned functional film is used as the support, the adhesive sheet disclosed herein can also be regarded as an "adhesive functional film" having an adhesive layer disclosed herein on at least one side of the functional film.

[0307] As described above, according to the technology disclosed herein, a laminate is provided, comprising the adhesive sheet disclosed herein and a component to which the adhesive sheet is adhered. The component to which the adhesive sheet is adhered may have the refractive index of the aforementioned adhered material. Furthermore, the difference between the refractive index of the adhesive sheet and the refractive index of the component (refractive index difference) may be the difference between the refractive index of the adhered material and the adhesive sheet. Regarding the components constituting the laminate, as described above as components, materials, and adhered materials, further description is not required.

[0308] As can be understood from the above description and the following embodiments, the matters disclosed in this specification include the following.

[0309] [1] An adhesive sheet comprising an adhesive layer,

[0310] It has an adhesive surface composed of the aforementioned adhesive layer.

[0311] The refractive index of the adhesive layer is higher than 1.570, the total light transmittance is above 86%, and the haze value is below 3.0%.

[0312] [2] The adhesive sheet according to [1] above, wherein the thickness of the adhesive layer is 5 μm or more.

[0313] [3] The adhesive sheet described in [1] or [2] above has a peel strength (adhesive force) of 3 N / 25 mm or more on the glass plate.

[0314] [4] The adhesive sheet according to any one of [1] to [3] above, wherein the arithmetic mean roughness Ra of the adhesive surface is 100 nm or less.

[0315] [5] The adhesive sheet according to any one of [1] to [4] above, wherein the water absorption rate of the adhesive layer is 1.0% or less.

[0316] [6] The adhesive sheet according to any one of [1] to [5] above is formed in the form of a laminate comprising the adhesive layer and the light-transmitting substrate.

[0317] [7] The adhesive sheet according to [6] above, wherein the light-transmitting substrate is a resin film.

[0318] [8] The adhesive sheet according to any one of [1] to [5] above is a double-sided adhesive sheet formed by the adhesive layer described above.

[0319] [9] An adhesive sheet with a release liner, comprising:

[0320] The adhesive sheet described in any one of [1] to [8] above, and

[0321] A release liner disposed on the adhesive surface of the aforementioned adhesive sheet.

[0322]

[10] An adhesive composition for forming an adhesive layer of the adhesive sheet described in any one of [1] to [8] above.

[0323]

[11] An adhesive composition comprising:

[0324] An acrylic polymer (A) containing an aromatic ring-containing monomer (m1) as a monomer unit; and

[0325] Additives (H) RO ), which is an organic material with a higher refractive index compared to the aforementioned acrylic polymer (A).

[0326]

[12] The adhesive composition according to

[11] above, wherein the above-mentioned additive (H) RO The refractive index is above 1.60.

[0327]

[13] According to the adhesive composition described in

[11] or

[12] above, wherein, relative to 100 parts by weight of the acrylic polymer (A) described above, the additive (H) RO The content of ) is higher than 0 parts by weight and lower than 60 parts by weight.

[0328]

[14] The adhesive composition according to any one of

[11] to

[13] above, wherein the above-mentioned additive (H) RO It includes at least one compound selected from the group consisting of compounds containing aromatic rings and compounds containing heterocycles.

[0329]

[15] The adhesive composition according to any one of

[11] to

[14] above, wherein the above-mentioned additive (H) RO (A) Compounds containing two or more aromatic rings within one molecule.

[0330]

[16] The adhesive composition according to

[15] above, wherein the above-mentioned additive (H) RO A compound comprising at least one of the following is a compound having two or more aromatic rings within one molecule:

[0331] (i) A structure comprising two non-fused aromatic rings directly chemically bonded together; and

[0332] (ii) A structure consisting of two fused aromatic rings.

[0333]

[17] The adhesive composition according to any one of

[11] to

[16] above, wherein the content of the aromatic ring-containing monomer (m1) in the monomer component constituting the acrylic polymer (A) is 50% by weight or more.

[0334]

[18] The adhesive composition according to any one of

[11] to

[17] above, wherein, in the monomer component constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is higher than 70% by weight and lower than 100% by weight.

[0335] More than 50% by weight of the aromatic ring-containing monomers (m1) mentioned above are homopolymers with a glass transition temperature of less than 10°C.

[0336]

[19] The adhesive composition according to any one of

[11] to

[18] above, wherein the monomer component constituting the acrylic polymer (A) further contains a monomer (m2) having at least one of hydroxyl and carboxyl groups.

[0337]

[20] The adhesive composition according to any one of

[11] to

[18] above is used to form the adhesive layer of the adhesive sheet according to any one of [1] to [8] above.

[0338]

[21] An adhesive formed from any one of the adhesive compositions described in

[11] to

[20] above, having a refractive index higher than 1.570.

[0339]

[22] An adhesive sheet comprising an adhesive layer made of an adhesive, said adhesive being formed from any one of the adhesive compositions described in

[11] to

[20] above.

[0340]

[23] The adhesive sheet according to

[22] above, wherein the haze value of the adhesive layer is 1.0% or less.

[0341]

[24] An interlayer sheet, which is used as an interlayer sheet disposed between the layers of a laminate for optical applications.

[0342] It comprises a viscoelastic layer V1 with a refractive index n1 of 1.570 or higher, and the interlayer sheet satisfies:

[0343] The total light transmittance is over 86%;

[0344] The haze value is below 1.0%; and,

[0345] The energy storage modulus G' at 25℃ is 30kPa~700kPa.

[0346]

[25] The interlayer sheet described in

[24] above has a thickness of 5 μm or more.

[0347]

[26] According to the interlayer sheet described in

[24] or

[25] above, wherein the viscoelastic layer V1 comprises a main polymer and a plasticizing material with a molecular weight lower than that of the main polymer.

[0348]

[27] According to the interlayer sheet described in

[26] above, the weight-average molecular weight of the plasticizing material is 30,000 or less.

[0349]

[28] The interlayer sheet according to any one of

[24] to

[27] above further comprises a viscoelastic layer V2 laminated on the viscoelastic layer V1.

[0350] The storage modulus G' of the viscoelastic layer V2 at 25°C V2The energy storage modulus G' of the viscoelastic layer V1 at 25°C is lower than that of the above viscoelastic layer V1. V1 .

[0351]

[29] According to the interlayer sheet described in

[28] above, wherein the refractive index n2 of the viscoelastic layer V2 is lower than the refractive index n1 of the viscoelastic layer V1.

[0352]

[30] The interlayer sheet according to any one of

[24] to

[29] above, wherein the viscoelastic layer V1 is a layer formed by the adhesive composition according to any one of

[11] to

[18] above.

[0353]

[31] The interlayer sheet according to any one of

[24] to

[29] above, wherein the viscoelastic layer V1 is the adhesive layer in the adhesive sheet according to any one of [1] to [5] above.

[0354]

[32] An optical laminate comprising:

[0355] Interlayer sheet as described in any one of

[24] to

[31] above, and

[0356] A resin film laminated on the above interlayer sheet.

[0357]

[33] An interlayer sheet with a release liner, comprising:

[0358] Interlayer sheet as described in any one of

[24] to

[31] above, and

[0359] A release liner covering at least one surface of the aforementioned interlayer sheet.

[0360] Example

[0361] The following describes some embodiments related to the present invention, but it is not intended to limit the invention to the scope shown in these specific examples. It should be noted that in the following description, "parts" and "%" indicating the amount used or the content are based on weight unless otherwise specified.

[0362] <Example 1>

[0363] (Preparation of acrylic polymer solutions)

[0364] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser, 95 parts of m-phenoxybenzyl acrylate (manufactured by Kyoei Chemical Co., Ltd., trade name "LIGHT ACRYLATE POB-A", refractive index: 1.566, Tg of homopolymer: -35℃, hereinafter referred to as "POB-A"), 5 parts of 4-hydroxybutyl acrylate (4HBA), 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as polymerization initiator, and 100 parts of toluene as polymerization solvent were added. Nitrogen gas was introduced while stirring slowly, and the liquid temperature in the flask was maintained at approximately 60℃ for 6 hours to prepare a 50% solution of acrylic polymer A1. The weight-average molecular weight (Mw) of this acrylic polymer A1 is 500,000. The Tg of the above acrylic polymer A1 based on the above monomer composition (i.e., Tg) is... T The temperature is -35℃, based on the Tg (i.e., Tg) of the monomer containing the aromatic ring. m1 The temperature is -35℃.

[0365] (Preparation of the adhesive composition)

[0366] The above-mentioned acrylic polymer A1 solution (50%) was diluted to 30% with ethyl acetate, and additive (H) was added to 334 parts of this solution (100 parts of non-volatile components). RO An acrylic adhesive composition C1 was prepared by mixing 5 parts of 6-acryloyloxymethyl dinaphthothiophene (6-methacrylate body manufactured by Sugai Chemical IND.CO.,LTD., trade name "6MDNTA", refractive index 1.75), 10 parts of a 1% ethyl acetate solution of hexamethylene diisocyanate isocyanurate body (manufactured by Tosoh Corporation, trade name "Coronate HX", 3-functional isocyanate compound) as a crosslinking agent (0.1 parts of non-volatile component), 2 parts of acetylacetone as a crosslinking delay agent, and 1 part of a 1% ethyl acetate solution of iron acetylacetone as a crosslinking catalyst (0.01 parts of non-volatile component).

[0367] (Making the adhesive sheet)

[0368] The acrylic adhesive composition C1 prepared above was coated onto the silicone-treated surface of a polyethylene terephthalate (PET) film R1 (50 μm thick) with one side treated with silicone. The film was then heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 25 μm. Next, a silicone-treated PET film R2 (25 μm thick) with one side treated with silicone was laminated onto the surface of the adhesive layer. This process yields a substrate-free double-sided adhesive sheet S1 formed from the adhesive layer. Both sides of the adhesive sheet S1 are protected by PET films (release liner) R1 and R2.

[0369] <Examples 2~5>

[0370] Additive (H) RO The types of acrylic polymers and the amount used per hundred parts of acrylic polymer are changed as shown in Table 1. Otherwise, acrylic adhesive compositions C2 to C5 of Examples 2 to 5 are prepared in the same manner as the preparation of acrylic adhesive composition C1 in Example 1. Here, in Table 1, “BPFL” represents 9,9-bis(4-hydroxyphenyl)fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., refractive index 1.68) and “BAFL” represents 9,9-bis(4-aminophenyl)fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., refractive index 1.73).

[0371] Acrylic adhesive compositions C2 to C5 were used instead of acrylic adhesive composition C1. Otherwise, adhesive sheets (substrate-free double-sided adhesive sheets formed of adhesive layers) S2 to S5 of Examples 2 to 5 were made in the same manner as the adhesive sheet in Example 1.

[0372] <Example 6>

[0373] In a detachable flask equipped with a thermometer, stirrer, reflux condenser, and nitrogen inlet, 20 parts of POB-A, 80 parts of 1-naphthyl methyl acrylate (manufactured by Kyoei Chemical Co., Ltd., trade name "LIGHT ACRYLATE NMT-A", refractive index: 1.595, Tg of homopolymer: 31℃, hereinafter referred to as "NMT-A"), 0.2 parts of AIBN as polymerization initiator, 3.5 parts of α-thioglycerol as chain transfer agent, and 67 parts of methyl ethyl ketone were added. Nitrogen gas was then introduced, and nitrogen replacement was carried out for about 1 hour with stirring. The flask was then heated to 70℃ and reacted for 12 hours to obtain an acrylic oligomer with a weight-average molecular weight (Mw) of 4000 and a refractive index of 1.63 (hereinafter referred to as oligomer B).

[0374] Additive (H) RO The type of the acrylic adhesive composition C6 was changed to the oligomer B mentioned above, and its usage was set to 30 parts (30 phr) relative to 100 parts of the acrylic polymer. Otherwise, the acrylic adhesive composition C6 of this example was prepared in the same manner as the acrylic adhesive composition C1 in Example 1.

[0375] Acrylic adhesive composition C6 is used instead of acrylic adhesive composition C1. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed of adhesive layer) S6 of this example is made in the same way as the adhesive sheet in Example 1.

[0376] <Example 7>

[0377] No additives used (H) RO In addition, the acrylic adhesive composition C7 of this example is prepared in the same manner as the acrylic adhesive composition C1 in Example 1.

[0378] Instead of acrylic adhesive composition C1, acrylic adhesive composition C7 is used, and the thickness of the adhesive layer is set to 20 μm. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed by the adhesive layer) S7 of this example is made in the same way as the adhesive sheet in Example 1.

[0379] <Example 8>

[0380] The monomer composition was changed to 72 parts POB-A, 23 parts NMT-A, and 5 parts 4HBA. Otherwise, a solution of acrylic polymer A2 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1. The weight-average molecular weight (Mw) of this acrylic polymer A2 was 450,000.

[0381] The acrylic adhesive composition C8 of this example was prepared in the same manner as the preparation of the adhesive composition in Example 1, except that a solution of acrylic polymer A2 was used instead of a solution of acrylic polymer A1.

[0382] The acrylic adhesive composition C8 is used instead of the acrylic adhesive composition C1. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed of adhesive layer) S8 of this example is made in the same way as the adhesive sheet in Example 1.

[0383] <Examples 9~13>

[0384] Additive (H) RO The types and amounts of acrylic adhesive compositions C9 to C13 of Examples 9 to 13 were changed as shown in Table 1. Except for the preparation of acrylic adhesive composition C8 in Example 8, acrylic adhesive compositions C9 to C13 of Examples 9 to 13 were prepared in the same manner.

[0385] Acrylic adhesive compositions C9 to C13 were used instead of acrylic adhesive composition C1. Otherwise, adhesive sheets (substrate-free double-sided adhesive sheets formed of adhesive layers) S9 to S13 of Examples 9 to 13 were made in the same manner as the adhesive sheet in Example A1.

[0386] <Example 14>

[0387] No additives used (H) RO In addition, the acrylic adhesive composition C14 of Example 14 was prepared in the same manner as the acrylic adhesive composition C8 in Example 8.

[0388] Acrylic adhesive composition C14 is used instead of acrylic adhesive composition C8. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed of adhesive layer) S14 of this example is made in the same way as the adhesive sheet in Example 8.

[0389] <Example 15>

[0390] The composition of the monomer components was changed to 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of 4HBA. Otherwise, a solution of acrylic polymer A3 (40%) was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1.

[0391] The above-mentioned acrylic polymer A3 solution (40%) was diluted to 20% with ethyl acetate. To 500 parts of this solution (100 parts of non-volatile components), 10 parts of a 1% ethyl acetate solution of hexamethylene diisocyanate isocyanurate (manufactured by Tosoh Corporation, trade name "Coronate HX", a 3-functional isocyanate compound) based on solids (0.1 parts of non-volatile components), 2 parts of acetylacetone as a crosslinking delay agent, and 1 part of a 1% ethyl acetate solution of iron acetylacetone as a crosslinking catalyst (0.01 parts of non-volatile components) were added and stirred to prepare acrylic adhesive composition C15. As the above-mentioned zirconia particle dispersion, a surface-treated zirconia particle dispersion (average particle size 20 nm, solid component refractive index: 1.64, surface treatment: carboxylic acid-based / phosphoric acid-based hydrophobic treatment, manufactured by Kyoei Chemical Co., Ltd.) was obtained by dispersing surface-treated zirconia particles in propylene glycol monomethyl ether (PGME).

[0392] Instead of acrylic adhesive composition C1, acrylic adhesive composition C15 was used, and the thickness of the adhesive layer was set to 20 μm. Otherwise, the adhesive sheet (substrate-free double-sided adhesive sheet formed by the adhesive layer) S15 of Example 15 was made in the same manner as the adhesive sheet in Example 1.

[0393] <Example 16>

[0394] The monomer composition was changed to POB-A / n-butyl acrylate (BA) / 4HBA = 79 / 20 / 1. Otherwise, a solution of acrylic polymer A4 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1. The weight-average molecular weight (Mw) of acrylic polymer A4 was 520,000.

[0395] The acrylic polymer A4 solution was used instead of the acrylic polymer A1 solution. Otherwise, the acrylic adhesive composition C16 of this example was prepared in the same manner as in Example 2 to produce an adhesive sheet (a substrate-free double-sided adhesive sheet formed by an adhesive layer) S16.

[0396] <Example 17>

[0397] The monomer composition was changed to POB-A / ethyl carbitol acrylate (CBA) / 4HBA = 79 / 20 / 1. Otherwise, a solution of acrylic polymer A5 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1. The weight-average molecular weight (Mw) of acrylic polymer A5 was 460,000.

[0398] The acrylic polymer A4 solution was used instead of the acrylic polymer A1 solution. Otherwise, the acrylic adhesive composition C17 of this example was prepared in the same manner as in Example 2 to produce an adhesive sheet (a substrate-free double-sided adhesive sheet formed by an adhesive layer) S17.

[0399] <Example 18>

[0400] The monomer composition was changed to POB-A / phenoxydiethylene glycol acrylate / 4HBA = 79 / 20 / 1. Otherwise, a solution of acrylic polymer A6 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1. The phenoxydiethylene glycol acrylate was the trade name "LIGHT ACRYLATE P2H-A" manufactured by Kyoei Chemicals Co., Ltd. The weight-average molecular weight (Mw) of acrylic polymer A6 was 480,000.

[0401] The acrylic polymer A6 solution was used instead of the acrylic polymer A1 solution. Otherwise, the acrylic adhesive composition C18 of this example was prepared in the same manner as in Example 2 to produce an adhesive sheet (a substrate-free double-sided adhesive sheet formed by an adhesive layer) S18.

[0402] <Example 19>

[0403] Additive (H) RO The acrylic adhesive composition C19 of this example was prepared in the same manner as in Example 2, except that it was changed to 2,12-diallyloxydinathothiophene (manufactured by Sugai Chemical IND.CO.,LTD., abbreviation: 2,12-DAODNT, refractive index: 1.729). The adhesive sheet (a substrate-free double-sided adhesive sheet formed by the adhesive layer) S19 was made.

[0404] <Examples 20~22>

[0405] No additives used (H) RO In addition, acrylic adhesive compositions C20-22 were prepared in the same manner as in Examples 16-18 to produce adhesive sheets (substrate-free double-sided adhesive sheets formed of adhesive layers) S20-22.

[0406] <Measurement and Evaluation>

[0407] (Refractive index)

[0408] For each example of adhesive layer (substrate-free double-sided adhesive sheet), the refractive index was measured using an Abbe refractometer (ATAGO, model "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.

[0409] (Total transmittance and haze value)

[0410] Test pieces were prepared by bonding the adhesive layer of each example to alkali-free glass (thickness 0.8–1.0 mm, total transmittance 92%, haze 0.4%). The total transmittance and haze of these test pieces were measured using a haze meter (manufactured by Murakami Color Technology Research Institute, trade name "HAZEMETER HM-150") at 23°C. The total transmittance and haze values ​​of the adhesive layer were obtained by subtracting the total transmittance and haze of the alkali-free glass from the measured values. The results are shown in Tables 1 and 2.

[0411] (Storage modulus G')

[0412] Each example adhesive layer was laminated to a thickness of approximately 1.5 mm and used as the test sample. Dynamic viscoelasticity was measured using an ARES instrument manufactured by TA Instruments under the following conditions. The storage modulus G' at 25°C was read from the measurement results. The results are shown in Tables 1 and 2.

[0413] [Measurement Conditions]

[0414] Deformation mode: Torsion

[0415] Measurement frequency: 1Hz

[0416] Heating rate: 5℃ / minute

[0417] Shape: Parallel plate

[0418] (Peel strength)

[0419] For each example of adhesive sheet, the peel strength to the glass plate was measured. Specifically, under the test environment of 23°C and 50% RH, the release liner was peeled off from one side of the adhesive sheet, a 50μm thick PET film was laminated, and then cut into pieces 25mm wide and 100mm long to serve as test pieces. The release liner on the other side of the test piece was peeled off, and a 2kg roller was used to press the sheet against the surface of an alkaline glass plate (Matsunami Glass Industry Co., Ltd., 1.35mm thick, with ground edges) once. The sample was placed in this environment for 30 minutes, then placed in a pressure degassing device (autoclave) and subjected to autoclaving at 50°C and 0.5 MPa for 30 minutes. Afterward, it was placed at 23°C and 50% RH for 24 hours. The peel strength (adhesive force) [N / 25 mm] was then determined using a universal tensile and compression testing machine according to JIS Z 0237:2000, at a tensile speed of 300 mm / min and a peel angle of 180 degrees. A Minebea TG-1kN universal tensile and compression testing machine was used. The results are shown in Tables 1 and 2.

[0420] [Table 1]

[0421] Table 1

[0422]

[0423] Acrylic polymer A1: POB-A / 4HBA = 95 / 5

[0424] Acrylic polymer A2: POB-A / NMT-A / 4HBA = 72 / 23 / 5

[0425] Acrylic polymer A3: 2EHA / 4HBA = 90 / 10

[0426] [Table 2]

[0427] Table 2

[0428]

[0429] Acrylic polymer A1: POB-A / 4HBA = 95 / 5

[0430] Acrylic polymer A4: POB-A / BA / 4HBA = 79 / 20 / 1

[0431] Acrylic polymer A5: POB-A / CBA / 4HBA = 79 / 20 / 1

[0432] Acrylic polymer A6: POB-A / P2H-A / 4HBA=79 / 20 / 1

[0433] As shown in Table 1, without additives (H RO In Example 7, the adhesive contained additive (H). RO Compared to Example 7, the adhesives in Examples 1-6 exhibited a high refractive index. These adhesives also showed high transparency and good peel strength. The same tendency was observed in the comparison between Examples 14 and Examples 8-13. On the other hand, Example 15, whose refractive index was increased by mixing in high-refractive-index inorganic particles, showed significantly poorer transparency (especially significantly higher haze) and did not exhibit adhesive properties (peel strength) suitable for practical use as an adhesive compared to Examples 1-14.

[0434] The same finding was also confirmed in Examples 16-19 shown in Table 2: through additive (H) RO The use of [a specific adhesive] can increase the refractive index. Examples 16-19 show adhesives with high transparency and good peel strength.

[0435] Based on the above, the adhesives of Examples 1-6, 8-13, and 16-19 can suppress the reduction of optical properties and increase the refractive index, and are therefore suitable for applications such as bonding of optical components (e.g., optical thin films having at least one function such as waveguide, light collector, and diffractor).

[0436] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The scope of the claims includes various modifications and alterations to the specific examples described above.

[0437] Explanation of reference numerals in the attached figures

[0438] 1, 2 adhesive sheets

[0439] 10 Adhesive Layer

[0440] 10A First Surface (Adhesive Surface)

[0441] 10B Second Surface

[0442] 20 Support substrate

[0443] 20A Side 1

[0444] 20B, Side 2 (Back)

[0445] 30, 31, 32 Peeling gaskets

[0446] 50 Adhesive sheets with release liner

[0447] 70 Optical components

[0448] 100 Components with adhesive sheets

Claims

1. An adhesive composition comprising: An acrylic polymer (A) containing an aromatic ring-containing monomer (m1) and a hydroxyl-containing monomer as monomer units; and Additives (H) RO This is an organic material with a higher refractive index compared to the acrylic polymer (A). The aromatic ring-containing monomer (m1) is selected from compounds that do not contain a structure consisting of two or more non-fused aromatic rings directly chemically bonded together. The aromatic ring-containing monomer (m1) comprises a monomer having a structural portion consisting of two aromatic rings bonded together by a linking group. In the monomer components constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is 50% by weight or more, and the content of the hydroxyl-containing monomer is 0.01% by weight or more and less than 12% by weight.

2. The adhesive composition according to claim 1, wherein, The additive (H) RO The refractive index is above 1.

60.

3. The adhesive composition according to claim 1 or 2, wherein, Relative to 100 parts by weight of the acrylic polymer (A), the additive (H) RO The content of ) is higher than 0 parts by weight and lower than 60 parts by weight.

4. The adhesive composition according to claim 1 or 2, wherein, The additive (H) RO It includes at least one compound selected from the group consisting of compounds containing aromatic rings and compounds containing heterocycles.

5. The adhesive composition according to claim 1 or 2, wherein, The additive (H) RO (A) Compounds containing two or more aromatic rings within one molecule.

6. The adhesive composition according to claim 5, wherein, The additive (H) RO A compound comprising at least one of the following is described as a compound having two or more aromatic rings within one molecule. (i) A structure comprising two non-fused aromatic rings directly chemically bonded together; and (ii) A structure consisting of two fused aromatic rings.

7. The adhesive composition according to claim 1 or 2, wherein, In the monomer components constituting the acrylic polymer (A), the content of the aromatic ring-containing monomer (m1) is higher than 70% by weight and lower than 100% by weight. More than 50% by weight of the aromatic ring-containing monomer (m1) is a homopolymer monomer with a glass transition temperature of less than 10°C.

8. The adhesive composition according to claim 1 or 2, wherein, The monomer components constituting the acrylic polymer (A) also contain monomers having carboxyl groups.

9. An adhesive formed from the adhesive composition of any one of claims 1 to 8, having a refractive index higher than 1.

570.

10. An adhesive sheet comprising an adhesive layer made of an adhesive, said adhesive being formed from the adhesive composition of any one of claims 1 to 8.

11. The adhesive sheet according to claim 10, wherein, The haze value of the adhesive layer is below 1.0%.

Images