KR20240041975A - Adhesives and adhesive sheets - Google Patents

Abstract

The goal is to provide an adhesive that can achieve both high refractive index and flexibility. An adhesive having a refractive index of 1.55 or more and a storage modulus of elasticity G' (0°C) at 0°C within the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa is provided.

Description

Adhesives and adhesive sheets

The present invention relates to adhesives and adhesive sheets.

This application claims priority based on Japanese Patent Application No. 2021-127818 filed on August 3, 2021 and Japanese Patent Application No. 2022-061161 filed on March 31, 2022, and those applications The entire contents of are incorporated herein by reference.

In general, adhesives (also called pressure-sensitive adhesives; the same applies hereinafter) are in a flexible solid (viscoelastic) state in the temperature range around room temperature and have the property of easily adhering to an adherend by applying pressure. Taking advantage of these properties, adhesives are widely used for purposes such as bonding, fixation, and protection in various industrial fields such as home appliances, automobiles, various machines, electrical devices, and electronic devices. An example of the use of the adhesive is to bond polarizing films, retardation films, cover window members, and various other light-transmitting members to other members in display devices such as liquid crystal displays and organic EL displays. . Technical literature on adhesives for optical members includes Patent Documents 1 and 2.

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

Patent Documents 1 and 2 disclose an adhesive composition containing as a main component a (meth)acrylic acid ester polymer containing a monomer having a plurality of aromatic rings as a monomer unit, and an adhesive obtained by crosslinking the adhesive composition, and having a plurality of aromatic rings. It is proposed that the refractive index of the adhesive is set to 1.50 or higher, particularly preferably 1.51 or higher, by using a monomer. For example, among the materials to which the adhesive is attached, such as optical members, there are materials with a high refractive index. If a general acrylic adhesive is used to bond such high refractive index materials, reflection may occur at the interface due to the difference in refractive index between the two. It is known. As an adhesive used for bonding the high refractive index materials, etc., the interface reflection can be prevented or suppressed by using an adhesive with a high refractive index. Additionally, the refractive index of acrylic adhesive is usually around 1.47.

However, an adhesive having good flexibility can be preferably used depending on the application location or usage mode. For example, in recent years, foldable displays and rollable displays have been put into practical use as displays such as organic EL displays used in electronic devices such as smartphones. There is a need to have the flexibility to follow. Adhesives with excellent flexibility are easy to follow and adhere to curved surfaces such as three-dimensional shapes, and are also suitable for use in curved electronic devices. Even for adhesives with a high refractive index, if the flexibility can be increased, it is useful because it can be applied to the applications requiring the above-mentioned flexibility. However, high refractive index materials used as monomer components of adhesive polymers or additives for adhesives tend to have a high glass transition temperature, such as having an aromatic ring, and adhesives formed using high refractive index materials tend to have reduced flexibility. In the design of adhesives, high refractive index and flexibility have a trade-off relationship.

The present invention was created in consideration of the above circumstances, and its purpose is to provide an adhesive capable of achieving both high refractive index and flexibility. Another object of the present invention is to provide an adhesive sheet containing the above adhesive.

According to this specification, an adhesive having a refractive index of 1.55 or more and a storage modulus of elasticity at 0°C G' (0°C) within the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa is provided. According to the adhesive, although it has a high refractive index, the range of storage elastic modulus G' (0°C) is suppressed to a low range, so it can achieve both high refractive index and flexibility. These adhesives preferably have a high refractive index, such as for foldable displays, and are suitable for bonding, fixing, and protecting applications that require flexibility to withstand repeated bending operations.

In some embodiments, an adhesive having a glass transition temperature (Tg) within the range of -50°C to 0°C is used. With an adhesive having a Tg in the range of -50 to 0°C, good flexibility tends to be easily obtained.

In some embodiments, the ratio of the storage modulus G'(0°C) to the storage modulus G'(80°C) at 80°C (G'(0°C)/G'(80°C)) is 1. An adhesive within the range of 1000 to 1000 is used. According to an adhesive that satisfies the above characteristics, the change in elastic modulus is suppressed over a wide temperature range from 0° C. to a high temperature range, so it is easy to exhibit stable characteristics (flexibility, etc.) with respect to temperature changes.

In some preferred embodiments, the ratio of the storage modulus G'(-10°C) at -10°C to the storage modulus G'(80°C) at 80°C (G'(-10°C)/G'( An adhesive having a temperature of 80°C) in the range of 1 to 1000 is used. An adhesive that satisfies the above characteristics is preferable because the change in elastic modulus is suppressed over a wide temperature range from a low temperature range to a high temperature range, and thus exhibits stable characteristics (flexibility, etc.) with respect to temperature changes.

Additionally, according to this specification, a pressure-sensitive adhesive sheet is provided including a pressure-sensitive adhesive layer made of any of the pressure-sensitive adhesives disclosed herein (which may be an pressure-sensitive adhesive formed from any of the pressure-sensitive adhesive compositions disclosed herein). The adhesive disclosed herein is preferably used by being molded in the form of an adhesive sheet and affixed to various members, such as members constituting a foldable display.

In some embodiments, the thickness of the adhesive layer is in the range of 5 to 75 μm. The technology disclosed herein can be preferably implemented in an aspect provided with an adhesive layer having a thickness of 5 to 75 μm.

In some embodiments, the product (G'(0°C)×T) of the storage modulus G'(0°C)[Pa] and the thickness T[μm] of the adhesive layer is 5.0×10 ⁴ to 5.0×10 It is within the range of ⁷ . The parameter (G'(0°C)×T) of 5.0×10 ⁴ or more means that, in a thin adhesive layer, the storage elastic modulus G’(0°C) is in the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. This means that you can employ . On the other hand, the fact that the above parameter is 5.0×10 ⁷ or less means that the upper limit of the thickness of the adhesive layer and the storage elastic modulus G’ (0°C) is limited. According to the adhesive sheet that satisfies the above parameters, based on the thinness of the adhesive layer (thickness below a predetermined value) and the limited storage modulus G' (0°C) in the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. , it can demonstrate excellent flexibility.

In some preferred embodiments, the total light transmittance of the adhesive sheet is 85% or more. Such highly transparent adhesive sheets can be preferably used in applications that require high light transparency (for example, optical applications) or applications that require good visibility of the adherend through the adhesive sheet. there is.

In some preferred embodiments, the haze value of the adhesive sheet is 3% or less. Such highly transparent adhesive sheets can be preferably used in applications that require high light transparency (for example, optical applications) or applications that require good visibility of the adherend through the adhesive sheet. there is.

The adhesive sheets according to some embodiments have a peel strength (adhesive force) to a glass plate of 0.1 N/25 mm or more. The pressure-sensitive adhesive sheet having the above-mentioned adhesive force can be preferably used in the form of sticking it to an adherend.

In addition, appropriate combinations of the elements described in this specification may also be included in the scope of inventions requiring patent protection through this patent application.

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

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

In addition, in the drawings below, members and parts that exert the same function may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are modeled to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the actually provided product.

In this specification, the “base polymer” of an adhesive refers to the main component of the rubber-like polymer contained in the adhesive. The rubber-like polymer refers to a polymer that exhibits rubbery elasticity in a temperature range around room temperature. In addition, in this specification, the “main component” refers to a component contained in excess of 50% by weight, unless otherwise specified.

In this specification, “acrylic polymer” refers to a polymer containing a monomer unit that constitutes the polymer and is derived from a monomer having at least one (meth)acryloyl group in one molecule. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an “acrylic monomer.” Therefore, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. A typical example of an acrylic polymer includes an acrylic polymer in which more than 50% by weight (preferably more than 70% by weight, for example, more than 90% by weight) of the monomer components constituting the polymer is an acrylic monomer.

In addition, in this specification, “acrylic monomer” refers to a monomer having at least one (meth)acryloyl group in one molecule. Here, “(meth)acryloyl group” refers comprehensively to acryloyl group and methacryloyl group. Therefore, the concept of acrylic monomer as used herein may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, “(meth)acrylic acid” refers comprehensively to acrylic acid and methacrylic acid, and “(meth)acrylate” refers to acrylate and methacrylate, respectively. The same goes for other similar terms.

<Characteristics of adhesive>

(refractive index)

The adhesive disclosed herein is characterized by having a refractive index of 1.55 or more. The refractive index of the adhesive is suitably greater than 1.560, and preferably greater than 1.570. In some embodiments, the refractive index of the adhesive may be 1.575 or more, 1.580 or more, or 1.585 or more. According to the adhesive having such a refractive index, light reflection at the interface with the adherend can be appropriately suppressed in a usage mode where the adhesive is attached to a material with a high refractive index. The preferable upper limit of the refractive index of the adhesive may vary depending on the refractive index of the adherend, so it is not limited to a specific range. For example, it may be 1.700 or less, 1.670 or less, 1.650 or less, 1.620 or less, or 1.600 or less. It's okay.

The refractive index of the adhesive can be adjusted, for example, by the composition of the adhesive (for example, the composition of the monomer component constituting the acrylic polymer). For example, by including an acrylic polymer with a high content of monomer (A1) in the monomer component or an additive ( _HRO ), an adhesive showing a refractive index of a predetermined or higher level can be prepared.

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

(Storage modulus G')

In addition, the adhesive disclosed herein has another feature in that the storage modulus G' (0°C) at 0°C is within the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. According to the adhesive, although it has a high refractive index, the range of storage elastic modulus G' (0°C) is suppressed to a low range, so it can achieve both high refractive index and flexibility. An adhesive having a storage modulus G' (0°C) in the above range can achieve both high refractive index and flexibility, and has flexibility that can withstand repeated bending operations. The storage modulus G' (0°C) is preferably 5.0×10 ⁵ Pa or less, may be 2.0×10 ⁵ Pa or less, may be 1.0×10 ⁵ Pa or less, may be 7.0×10 ⁴ Pa or less, and may be 5.0×10 5 Pa or less. It may be 10 ⁴ Pa or less, and may be 3.0×10 ⁴ Pa or less. In addition, the storage modulus G' (0°C) is preferably 2.0×10 ⁴ Pa or more, more preferably 4.0×10 ⁴ Pa or more, and may be 6.0×10 ⁴ Pa or more, and may be 1.0×10 ⁵ Pa or more. do.

The storage modulus G' (80°C) at 80°C of the adhesive disclosed herein is not particularly limited, and is suitably, for example, less than 1.0×10 ⁵ Pa, preferably less than 5.0×10 ⁴ Pa, and more. Preferably it is less than 3.0×10 ⁴ Pa, may be less than 1.0×10 ⁴ Pa, and may be less than 5.0×10 ³ Pa. The adhesive with a limited storage modulus G' (80°C) as described above has good flexibility in the high temperature range. The lower limit of the storage modulus G' (80°C) is not particularly limited, for example, 1.0×10 ² Pa or more, suitably 5.0×10 ² Pa or more, preferably 1.0×10 ³ Pa or more. Preferably it is 3.0×10 ³ Pa or more, and may be 5.0×10 ³ Pa or more. The adhesive having the storage elastic modulus G' (80°C) is preferable because it tends to have appropriate cohesion even in a high temperature range and has excellent heat resistance.

The storage modulus G' (-10°C) of the adhesive disclosed herein at -10°C is not particularly limited, and may be, for example, less than 1.0×10 ⁹ Pa, less than 1.0×10 ⁸ Pa, or 1.0 It is suitable to be less than ×10 ⁷ Pa, preferably 5.0 × 10 ⁶ Pa or less, may be 1.0 × 10 ⁶ Pa or less, may be 5.0 × 10 ⁵ Pa or less, and may be 1.0 × 10 ⁵ Pa or less. An adhesive with a limited storage modulus G' (-10°C) as described above can have better flexibility. For example, it can have good flexibility in a low temperature range and have flexibility that can withstand repeated bending operations in a wide temperature range including the low temperature range. The lower limit of the storage modulus G' (-10°C) is not particularly limited, and is, for example, 1.0×10 ² Pa or more, suitably 1.0×10 ³ Pa or more, preferably 5.0×10 ³ Pa or more, More preferably, it is 1.0×10 ⁴ Pa or more, may be 5.0×10 ⁴ Pa or more, may be 1.0×10 ⁵ Pa or more, and may be 5.0×10 ⁵ Pa or more. The adhesive having the storage modulus G' (-10°C) can be flexible and have appropriate cohesive force. Moreover, according to the adhesive having the storage elastic modulus G' (-10°C), it tends to be easy to achieve both high refractive index and flexibility even in a low temperature range.

The storage modulus G' (-20°C) of the adhesive disclosed herein at -20°C is not particularly limited, and may be, for example, less than 1.0×10 ¹⁰ Pa, less than 1.0×10 ⁹ Pa, or 5.0. It is suitable to be less than ×10 ⁸ Pa, may be less than 1.0×10 ⁸ Pa, may be less than 5.0×10 ⁷ Pa, may be less than 1.0×10 ⁷ Pa, may be less than 5.0×10 ⁶ Pa, or may be less than 1.0×10 ⁶ Pa It may be less than or equal to 5.0×10 ⁵ Pa or less. The adhesive with a limited storage modulus G' (-20°C) as described above can have particularly excellent flexibility. For example, it can have good flexibility in a lower temperature range and have flexibility to withstand repeated bending operations in a wide temperature range including the low temperature range. The lower limit of the storage modulus G' (-20°C) is not particularly limited, and is, for example, 1.0×10 ² Pa or more, suitably 1.0×10 ³ Pa or more, preferably 1.0×10 ⁴ Pa or more, More preferably, it is 1.0×10 ⁵ Pa or more, and may be 5.0×10 ⁵ Pa or more, or may be 1.0×10 ⁶ Pa or more. The adhesive having the storage modulus G' (-20°C) can be flexible and have appropriate cohesive force. Additionally, the adhesive having the storage modulus G' (-20°C) has a tendency to easily achieve both high refractive index and flexibility even in low temperature ranges.

(Storage modulus ratio)

In some embodiments, as an adhesive, the ratio of the storage modulus G'(0°C) at 0°C to the storage modulus G'(80°C) at 80°C (G'(0°C)/G'(80°C) An adhesive having a ℃)) within the range of 1 to 1000 is used. According to an adhesive that satisfies the above characteristics, the change in elastic modulus is suppressed over a wide temperature range from 0°C to a high temperature range, so it is easy to exhibit stable characteristics (flexibility, etc.) with respect to temperature changes. The ratio (G'(0°C)/G'(80°C)) is suitably 300 or less, preferably 100 or less, more preferably 50 or less, may be 25 or less, may be 10 or less, and may be 5 or less. It's okay. The lower limit of the ratio (G'(0°C)/G'(80°C)) may be, for example, 2 or more, or 3 or more.

In some embodiments, as an adhesive, the ratio of the storage modulus G'(-10°C) at -10°C to the storage modulus G'(80°C) at 80°C (G'(-10°C)/G An adhesive having '(80°C)) in the range of 1 to 1000 is used. An adhesive that satisfies the above characteristics is preferable because the change in elastic modulus is suppressed over a wide temperature range from low to high temperature ranges, so it is easy to exhibit stable characteristics (flexibility, etc.) with respect to temperature changes. The ratio (G'(-10°C)/G'(80°C)) is suitably 300 or less, preferably 150 or less, more preferably 100 or less, and may be 50 or less, 30 or less, or 20 or less. It may be less than or equal to 10. The lower limit of the ratio (G'(-10°C)/G'(80°C)) may be, for example, 2 or more, or 3 or more.

In some embodiments, as an adhesive, the ratio of the storage modulus G'(-20°C) at -20°C to the storage modulus G'(80°C) at 80°C (G'(-20°C)/G An adhesive having '(80°C)) in the range of 1 to 1000 is used. According to an adhesive that satisfies the above characteristics, the change in elastic modulus is suppressed in a wide temperature range from a lower temperature range to a higher temperature range, and thus stable characteristics (flexibility, etc.) can be exhibited with respect to temperature changes. The ratio (G'(-20°C)/G'(80°C)) may be 500 or less, 300 or less, 150 or less, 100 or less, 50 or less, or 30 or less. The lower limit of the ratio (G'(-20°C)/G'(80°C)) may be, for example, 5 or more, 10 or more, 50 or more, or 100 or more.

The glass transition temperature (Tg) of the adhesive is not particularly limited and can be set considering flexibility in a low temperature range and cohesion (heat resistance, etc.) in a high temperature range. In some embodiments, the Tg of the adhesive may be, for example, 30°C or lower, 15°C or lower, or 5°C or lower. In some preferred embodiments, the Tg of the adhesive is 0°C or lower, more preferably -5°C or lower, further preferably -10°C or lower, and -15°C or lower (e.g. -20°C or lower) from the viewpoint of flexibility. ℃ or lower) may also be used. The lower the Tg of the adhesive, the better the adhesive properties, such as adhesion to the adherend, tend to be excellent. Additionally, by setting the Tg of the adhesive low, the change in elastic modulus in a temperature range higher than Tg can be suppressed. The lower limit of the Tg of the adhesive is, for example, -50°C or higher, preferably -40°C or higher, and may be -30°C or higher. According to the adhesive having the above Tg, appropriate cohesion tends to be easily obtained. Additionally, there is a tendency to easily form an adhesive that has both a high refractive index and a low elastic modulus.

The storage modulus G' of the adhesive at each of the above temperatures and the glass transition temperature Tg of the adhesive can be measured by the method described in the Examples described later, and each storage modulus ratio can be calculated from the results. Each storage elastic modulus G', each storage elastic modulus ratio, and glass transition temperature Tg of the adhesive are, for example, selected by the composition of the monomer component constituting the base polymer (e.g., selected type and content of monomer (A1)), plasticizer It can be adjusted by selection of paper or amount used, selection of cross-linking agent, type and amount used, use of additives, type and amount used, etc.

<Composition of adhesive>

(base polymer)

In the technology disclosed herein, the type of adhesive is not particularly limited. The adhesive includes acrylic polymers, rubber polymers (e.g. natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, and polyester that can be used in the field of adhesives. It may contain one or two or more types of various rubber-like polymers such as amide-based polymers and fluorine-based polymers as adhesive polymers (meaning structural polymers that form adhesives, hereinafter also referred to as “base polymers”). From the viewpoint of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably used. Among them, an adhesive containing an acrylic polymer as a base polymer (acrylic adhesive) is preferable. The technology disclosed herein is preferably implemented using an acrylic adhesive.

Hereinafter, acrylic adhesives will be mainly described, but it is not intended to limit the adhesives disclosed herein to acrylic adhesives.

(Acrylic polymer)

The technology disclosed herein can be preferably implemented using an acrylic adhesive. The acrylic polymer, which is the base polymer of the acrylic adhesive, preferably contains an aromatic ring-containing monomer (A1) as a monomer component constituting the acrylic polymer. That is, an acrylic polymer containing an aromatic ring-containing monomer (A1) as a monomer unit is preferable. Here, in this specification, the “monomer component constituting the acrylic polymer” refers to whether it is included 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. , refers to a monomer that constitutes a repeating unit of an acrylic polymer in an adhesive formed from the adhesive composition. That is, the monomer component constituting the acrylic polymer may be contained in the pressure-sensitive adhesive composition in any of the forms of a polymerized product, unpolymerized product, or partially polymerized product. From the viewpoint of ease of preparation of the adhesive composition, etc., in some embodiments, the adhesive composition contains substantially all of the monomer components (for example, 95% by weight or more, preferably 99% by weight or more) in the form of a polymer. desirable.

(Monomer (A1))

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

Examples of the ethylenically unsaturated group include (meth)acryloyl group, vinyl group, and (meth)allyl group. A (meth)acryloyl group is preferable from the viewpoint of polymerization reactivity, and an acryloyl group is more preferable from the viewpoint of flexibility and adhesiveness. From the viewpoint of suppressing a decrease in the flexibility of the adhesive, a compound (i.e., a monofunctional monomer) in which the number of ethylenically unsaturated groups contained in one molecule is 1 is preferably used as the monomer (A1).

The number of aromatic rings contained in one molecule of the compound used as the monomer (A1) may be 1 or 2 or more. The upper limit of the number of aromatic rings is not particularly limited, and may be, for example, 16 or less. In some embodiments, from the viewpoint of ease of preparation of the acrylic polymer, transparency of the adhesive, etc., the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, and 5 or less. It may be 2 or less, it may be 4 or less, it may be 3 or less, and it may be 2 or less.

The aromatic ring possessed by the compound used as the monomer (A1) includes a benzene ring (may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); Condensed rings of naphthalene ring, indene ring, azulene ring, anthracene ring, and phenanthrene ring; It may be a carbon ring such as pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, thiophene ring. ; It may be a heterocycle (heterocycle) such as: In the above heterocycle, the heteroatoms included as ring constituent atoms may be, for example, one or two or more selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatom constituting the heterocycle may be one or both of nitrogen and sulfur. The monomer (A1) may have a structure in which 1 or 2 or more carbocyclic rings and 1 or 2 or more heterocycles are condensed, such as a dinaphthothiophene structure.

The aromatic ring (preferably a carbocyclic ring) may have one or two or more substituents on the ring constituent atoms, and does not need to have any substituent. When having a substituent, the substituent includes an alkyl group, alkoxy group, aryloxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc. Illustrative, but not limited to these. In a substituent containing a carbon atom, the number of carbon atoms included in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the aromatic ring may have no substituents on ring constituent atoms, or may be an aromatic ring having one or two or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (for example, a bromine atom). there is. In addition, that the aromatic ring of the monomer (A1) has a substituent on its ring constituent atoms means that the aromatic ring has a substituent other than the substituent having an ethylenically unsaturated group.

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

Examples of compounds that can be preferably employed as the monomer (A1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylate and aromatic ring-containing vinyl compound can be used individually or in combination of two or more types. You may use a combination of 1 type or 2 or more types of aromatic ring-containing (meth)acrylates and 1 type or 2 or more types of aromatic ring-containing vinyl compounds.

In some embodiments, as the monomer (A1), a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be used because it is easy to obtain a high refractive index effect. Examples of monomers having two or more aromatic rings in one molecule (monomers containing multiple aromatic rings) include monomers with a structure in which two or more non-fused aromatic rings are bonded through a linking group, and two or more non-fused aromatic rings are formed directly (i.e., not through other atoms). monomers having a chemically bonded structure, monomers having a condensed aromatic ring structure, monomers having a fluorene structure, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure, etc. The monomer containing multiple aromatic rings can be used individually or in combination of two or more types.

The linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (for example -O-(CH ₂ ) _n -group, where n is 1 to 3, preferably Preferably 1, a thiooxyalkylene group (e.g. -S-(CH ₂ ) _n -group, where n is 1 to 3, preferably 1, a straight chain alkylene group (e.g. -(CH ₂ ) _n -group, where n is 1 to 6, preferably 1 to 3), and the alkylene group in the oxyalkylene group, thiooxyalkylene group, and linear alkylene group may be a partially halogenated or fully halogenated group, etc. Flexibility of the adhesive, etc. From the viewpoint of, suitable examples of the above-mentioned linking group include oxy group, thioxy group, oxyalkylene group and straight-chain alkylene group.Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded through linking group are: Phenoxybenzyl (meth)acrylate (for example, m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl (meth)acrylate, benzylbenzyl (meth)acrylate, etc. are mentioned.

The monomer having a structure in which two or more non-fused aromatic rings are directly chemically bonded may be, for example, (meth)acrylate containing a biphenyl structure, (meth)acrylate containing a triphenyl structure, or biphenyl containing a vinyl group. Specific examples include o-phenylphenol (meth)acrylate and biphenylmethyl (meth)acrylate.

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

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

Examples of monomers having the dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. As a specific example, (meth)acryloyloxymethyldinaphthothiophene (for example, a structure in which CH ₂ CH(R ¹ )C(O)OCH ₂ - is bonded to the 5th or 6th position of the dinaphthothiophene ring. Compound, where R ¹ is a hydrogen atom or a methyl group), (meth)acryloyloxyethyldinaphthothiophene (for example, at the 5th or 6th position of the dinaphthothiophene ring, CH ₂ CH (R ¹ ) A compound with a structure in which C(O)OCH(CH ₃ )- or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ - is bonded. Here, R ¹ is a hydrogen atom or a methyl group), vinyldinaphthoti ophene (for example, a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), (meth)allyloxydinaphthothiophene, etc. In addition, the monomer having a dinaphthothiophene structure is included in the concept of the monomer having the condensed aromatic ring structure by including a naphthalene structure and having a structure in which a thiophene ring and two naphthalene structures are condensed.

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

In addition, neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-fused aromatic rings are directly chemically bonded.

In some preferred embodiments, a monomer having one aromatic ring (preferably a carbocyclic ring) per molecule is used as the monomer (A1). A monomer having one aromatic ring per molecule (monomer containing a single aromatic ring) can be helpful, for example, in improving the flexibility of the adhesive, adjusting the adhesive properties, and improving transparency. Single aromatic ring-containing monomers can be used individually or in combination of two or more types. In some embodiments, a monomer having one aromatic ring per molecule may be used in combination with a monomer containing multiple aromatic rings from the viewpoint of improving the refractive index of the adhesive.

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

As the monomer (A1), a monomer having a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the aromatic ring in the various aromatic ring-containing monomers described above may be used. In this way, the monomer in which the oxyethylene chain is sandwiched between the ethylenically unsaturated group and the aromatic ring can be understood as an ethoxylated product of the original monomer. The repeating number of the oxyethylene unit (-CH ₂ CH ₂ O-) in the oxyethylene chain is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, for example It is 1. Specific examples of ethoxylated aromatic ring-containing monomers include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, and phenoxyethyl (meth)acrylate. , phenoxydiethylene glycol di(meth)acrylate, etc.

The content of the monomer containing multiple aromatic rings in the monomer (A1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, and 40% by weight or more. In some embodiments, the content of the monomer containing multiple aromatic rings in the monomer (A1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more from the viewpoint of making it easier to obtain a higher refractive index, It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be a monomer containing multiple aromatic rings. That is, as the monomer (A1), only one or two or more types of aromatic ring-containing monomers may be used. In addition, in some embodiments, for example, taking into account the balance between high refractive index and low elastic modulus and, if necessary, adhesive force, the content of the aromatic ring-containing monomer in the monomer (A1) may be less than 100% by weight. It may be 98% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 65% by weight or less, 50% by weight or less, and 25% by weight or less. , may be 10% by weight or less. The technology disclosed here can also be implemented in an embodiment in which the content of the monomer containing multiple aromatic rings in the monomer (A1) is less than 5% by weight. It is not necessary to use a monomer containing multiple aromatic rings.

The content of the monomer containing multiple aromatic rings in the monomer component constituting the acrylic polymer is not particularly limited, and can be set so as to realize an adhesive that achieves both the desired refractive index and storage elastic modulus G' (0°C). The content of the monomer containing multiple aromatic rings in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of making it easier to realize an adhesive having a higher refractive index, the content of the aromatic ring-containing monomer in the monomer component may be, for example, more than 35% by weight, or more than 50% by weight. It is advantageous, it is preferable that it is more than 70% by weight, it may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, 91% by weight or more, 92% by weight or more, 93% by weight or more, It may be 94% by weight or more, 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more. The content of the aromatic ring-containing monomer in the monomer component is advantageously set to approximately 99% by weight or less, and is preferably set to 98% by weight or less, taking into account the balance between high refractive index and low elastic modulus and, if necessary, adhesive strength. It is preferable, and it is more preferable to set it to 96 weight% or less, and may be 93 weight% or less, may be 90 weight% or less, may be 85 weight% or less, may be 80 weight% or less, and may be 75 weight% or less. In some embodiments, from the viewpoint of making it easier to realize higher adhesive properties and/or optical properties (e.g. transparency), the content of the aromatic ring-containing monomer in the monomer component may be 70% by weight or less. , may be 60% by weight or less, may be 50% by weight or less, may be 40% by weight or less, may be 25% by weight or less, may be 15% by weight or less, and may be 5% by weight or less. The technology disclosed here can also be implemented in an embodiment in which the content of the monomer containing multiple aromatic rings in the monomer component is less than 3% by weight.

The content of the monomer containing a single aromatic ring in the monomer (A1) is not particularly limited and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the monomer containing a single aromatic ring in the monomer (A1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more from the viewpoint of making it easier to obtain a higher refractive index, It may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (A1) may be a monomer containing a single aromatic ring. That is, as the monomer (A1), only one or two or more types of monomers containing single aromatic rings may be used. In addition, in some embodiments, for example, taking into account the balance between high refractive index and low elastic modulus and, if necessary, adhesive force, the content of the aromatic ring single-containing monomer in the monomer (A1) may be less than 100% by weight. It may be 98% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 65% by weight or less, 50% by weight or less, and 25% by weight or less. , may be 10% by weight or less. The technology disclosed here can also be carried out in an embodiment in which the content of the monomer containing a single aromatic ring in the monomer (A1) is less than 5% by weight. It is not necessary to use a monomer containing a single aromatic ring.

The content of the monomer containing a single aromatic ring in the monomer component constituting the acrylic polymer is not particularly limited, and can be set so as to realize an adhesive that achieves both the desired refractive index and storage elastic modulus G' (0°C). The content of the aromatic ring single-containing monomer in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of making it easier to realize an adhesive having a higher refractive index, the content of the monomer containing a single aromatic ring in the monomer component may be, for example, more than 35% by weight, or more than 50% by weight. It is advantageous, preferably 60% by weight or more, more preferably more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. , may be 98% by weight or more. The content of the aromatic ring single-containing monomer in the monomer component may be approximately 99% by weight or less, and is preferably 98% by weight or less, taking into account the balance between high refractive index and low elastic modulus and, if necessary, adhesive strength. It is more preferable to set it as 96 weight% or less, and may be 93 weight% or less, may be 90 weight% or less, may be 85 weight% or less, may be 80 weight% or less, and may be 75 weight% or less. In some embodiments, from the viewpoint of making it easier to realize higher adhesive properties and/or optical properties (e.g. transparency), the content of the monomer containing a single aromatic ring in the monomer component may be 70% by weight or less. , may be 60% by weight or less, may be 50% by weight or less, may be 40% by weight or less, may be 25% by weight or less, may be 15% by weight or less, and may be 5% by weight or less. The technique disclosed herein can also be carried out in an embodiment in which the content of the monomer containing a single aromatic ring in the monomer component is less than 3% by weight.

In some aspects of the technology disclosed herein, a high refractive index monomer can be preferably employed as at least part of the monomer (A1). Here, “high refractive index monomer” refers to a monomer whose refractive index is, for example, approximately 1.510 or higher, preferably approximately 1.530 or higher, and more preferably approximately 1.550 or higher. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, but from the viewpoint of ease of preparation of acrylic polymer and compatibility with flexibility suitable as an adhesive, it may be, for example, 3.000 or less, 2.500 or less, or 2.000 or less. It may be less than 1.900, less than 1.800, or less than 1.700. High refractive index monomers can be used individually or in combination of two or more types.

In addition, the refractive index of the monomer is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As an Abbe refractometer, model “DR-M4” manufactured by ATAGO or its equivalent can be used. If the nominal value of the refractive index at 25°C is provided by the manufacturer, etc., the nominal value can be adopted.

As the high refractive index monomer, those having the corresponding refractive index can be appropriately adopted from among the compounds included in the concept of the aromatic ring-containing monomer (A1) disclosed herein (for example, the compounds and compound groups exemplified above). there is. Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, Tg of homopolymer: 31°C), ethoxylated o- Phenylphenol acrylate (number of repetitions of oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6°C), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2℃), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35℃), 6-acryloyloxymethyldinaphthothiophene (6MDNTA, refractive index: 1.75) , 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyldinaphthothiophene Examples include, but are not limited to, ophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), and 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793). does not

The content of the high refractive index monomer (i.e., an aromatic ring-containing monomer with a refractive index of approximately 1.510 or more, preferably approximately 1.530 or more, more preferably approximately 1.550 or more) in the monomer (A1) is not particularly limited, and is, for example, For example, it may be 5% by weight or more, 25% by weight or more, 35% by weight or more, and 40% by weight or more. In some embodiments, from the viewpoint of making it easier to obtain a higher refractive index, the content of the high refractive index monomer in the monomer (A1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more, 85 It may be % by weight or more, may be 90 % by weight or more, and may be 95 % by weight or more. Substantially 100% by weight of the monomer (A1) may be a high refractive index monomer. In addition, in some embodiments, for example, from the viewpoint of achieving a well-balanced coexistence of high refractive index, low elastic modulus, and, if necessary, adhesive force, the content of the high refractive index monomer in the monomer (A1) may be less than 100% by weight. , may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, and may be 65% by weight or less. In some embodiments, taking adhesion properties and/or optical properties into consideration, the content of the high refractive index monomer in monomer (A1) may be 50% by weight or less, 25% by weight or less, or 15% by weight or less. It may be 10% by weight or less. The technology disclosed here can also be carried out in an embodiment where the content of the high refractive index monomer in the monomer (A1) is less than 5% by weight. There is no need to use a high refractive index monomer.

The content of the high refractive index monomer in the monomer component constituting the acrylic polymer is not particularly limited and can be set to achieve an adhesive that achieves both the desired refractive index and elastic modulus. Additionally, if necessary, it can be set taking into account compatibility with adhesive properties (e.g., adhesive force, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). The content of the high refractive index monomer in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, the content of the high refractive index monomer in the monomer component constituting the acrylic polymer may be, for example, more than 35% by weight, and from the viewpoint of making it easier to obtain a higher refractive index, it is advantageous to be more than 50% by weight. It is preferably more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The content of the high refractive index monomer in the monomer component is advantageously set to 99% by weight or less, and is preferably set to 98% by weight or less, from the viewpoint of well-balanced high refractive index, low elastic modulus, and, if necessary, adhesive strength. , it is more preferable to set it to 96 weight% or less, and may be 93 weight% or less, may be 90 weight% or less, may be 85 weight% or less, may be 80 weight% or less, and may be 75 weight% or less. In some embodiments, taking into account adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer component may be 70% by weight or less, 50% by weight or less, or 25% by weight or less. , may be 15% by weight or less, and may be 5% by weight or less. The technique disclosed herein can also be carried out in an embodiment in which the content of the high refractive index monomer in the monomer component is less than 3% by weight.

In some preferred embodiments, at least part of the monomer (A1) is an aromatic ring-containing monomer (hereinafter sometimes referred to as “monomer L”) having a homopolymer Tg of 10°C or lower. Increase the content of the aromatic ring-containing monomer (A1) (in particular, the aromatic ring-containing monomer (A1) corresponding to at least one of the above-mentioned multiple aromatic ring-containing monomers, single aromatic ring-containing monomers, and high refractive index monomers) in the monomer component. Since the storage elastic modulus G' of the bottom adhesive generally tends to increase, the increase in the storage elastic modulus G' can be suppressed by employing monomer L as part or all of the monomer (A1). Thereby, the refractive index can be improved while better maintaining the low elastic modulus. The Tg of monomer L may be, for example, 5°C or lower, 0°C or lower, -10°C or lower, -20°C or lower, and -25°C or lower. The lower limit of Tg of monomer L is not particularly limited. Considering the balance with the refractive index improvement effect, in some embodiments, the Tg of monomer L may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. In several other embodiments, the Tg of monomer L may be, for example, -30°C or higher, -10°C or higher, 0°C or higher, or 3°C or higher. Monomer L can be used individually or in combination of two or more types.

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

The content of monomer L in the monomer (A1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, from the viewpoint of making it easier to obtain an adhesive that achieves both high refractive index and low elastic modulus at a higher level, the content of monomer L in the monomer (A1) may be, for example, 50% by weight or more. From the viewpoint of elasticity modulus, it is preferable to be 60% by weight or more, may be 70% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. Substantially 100% by weight of monomer (A1) may be monomer L. In addition, in some embodiments, for example, from the viewpoint of achieving a well-balanced coexistence of high refractive index, low elastic modulus, and, if necessary, adhesive force, the content of monomer L in the monomer (A1) may be less than 100% by weight, It may be 98 weight% or less, 90 weight% or less, 80 weight% or less, and 65 weight% or less.

The content of monomer L in the monomer component constituting the acrylic polymer may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, from the viewpoint of making it easier to obtain an adhesive that achieves both high refractive index and low elastic modulus at a higher level, the content of monomer L in the monomer component may be, for example, more than 35% by weight, and the content of monomer L may be more than 35% by weight, for example, to improve the refractive index. From the viewpoint, it is advantageous to exceed 50% by weight, preferably more than 70% by weight, 75% by weight or more, 85% by weight or more, 90% by weight or more, and 95% by weight or more. The content of monomer L in the monomer component is advantageously set to approximately 99% by weight or less, and is preferably set to 98% by weight or less, from the viewpoint of achieving a well-balanced high refractive index, low elastic modulus, and, if necessary, adhesive strength. , it is more preferable to set it to 96 weight% or less, and may be 93 weight% or less, may be 90 weight% or less, may be 85 weight% or less, may be 80 weight% or less, and may be 75 weight% or less.

In some embodiments, the glass transition temperature Tg _A1 based on the composition of the monomer (A1) is not particularly limited. From the viewpoint of lowering the elastic modulus, it is advantageous for the glass transition temperature Tg _A1 to be approximately 20°C or lower, preferably 10°C or lower, for example, may be 5°C or lower, 0°C or lower, or -10°C or lower. , It may be -20℃ or lower, and it may be -25℃ or lower. The lower limit of the glass transition temperature Tg _A1 is not particularly limited. Considering the balance with the refractive index improvement effect, in some embodiments, the glass transition temperature Tg _A1 may be, for example, -70°C or higher, -55°C or higher, or -45°C or higher. The technology disclosed herein can also be suitably implemented in an embodiment where the glass transition temperature Tg _A1 is, for example, -40°C or higher, -35°C or higher, -33°C or higher, -30°C or higher, or -25°C or higher. In several other embodiments, the glass transition temperature Tg _A1 may be, for example, -10°C or higher, 0°C or higher, or 3°C or higher.

Here, the glass transition temperature Tg _A1 based on the composition of the monomer (A1) refers to Tg determined by Fox's equation described later based on the composition of only the monomer (A1) among the monomer components constituting the acrylic polymer. The glass transition temperature Tg _A1 is calculated by applying Fox's equation to only the monomer (A1) among the monomer components constituting the acrylic polymer, and determining the homopolymer glass transition temperature of each aromatic ring-containing monomer used as the monomer (A1), It can be calculated from the weight fraction of each aromatic ring-containing monomer in the total amount of monomer (A1). In an embodiment in which only one type of monomer is used as the monomer (A1), the homopolymer Tg of the monomer and the glass transition temperature Tg _A1 are identical.

In some embodiments, as the aromatic ring-containing monomer (A1), monomer L (i.e., aromatic ring-containing monomer with a homopolymer Tg of 10°C or lower) and monomer H with a Tg higher than 10°C can be used in combination. . The Tg of monomer H may be, for example, greater than 10°C, greater than 15°C, or greater than 20°C. By using monomer L and monomer H in combination, in an adhesive with a high content of aromatic ring-containing monomer (A1) in the monomer component, the adhesive has a high refractive index and flexibility suitable for adhesion to the adherend is improved. It can be compatible at a high level. The usage ratio of monomer L and monomer H can be set to appropriately produce these effects, and is not particularly limited. For example, it is desirable to set the usage ratio of monomer L and monomer H to satisfy the glass transition temperature Tg _A1 of any of the above.

In some embodiments, the aromatic ring-containing monomer (A1) may be preferably selected from a compound that does not contain a structure in which two or more non-fused aromatic rings are directly chemically bonded (for example, a biphenyl structure). For example, the content of a compound containing a structure in which two or more non-fused aromatic rings are directly chemically bonded is less than 5% by weight (more preferably less than 3% by weight, and may be 0% by weight). Acrylic polymers composed of acrylic polymers are preferred. In this way, limiting the amount of use of a compound containing a structure in which two or more non-fused aromatic rings are directly chemically bonded can be advantageous from the viewpoint of realizing an adhesive that has a better balance of high refractive index, low elastic modulus, and, if necessary, adhesive strength. there is.

The content of monomer (A1) in the monomer component constituting the acrylic polymer is not particularly limited, and includes the desired refractive index and elastic modulus, as well as adhesive properties (e.g., adhesive force, etc.) and/or optical properties (e.g., total light transmittance). , haze value, etc.) can be set so that an adhesive can be realized. In some embodiments, the content of monomer (A1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. , may be 70% by weight or more. In some preferred embodiments, the content of monomer (A1) in the monomer component constituting the acrylic polymer may be, for example, more than 70% by weight, and is preferably 75% by weight or more, so that a higher refractive index can be easily obtained. From this point of view, it is preferable that it is 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, 91% by weight or more, 92% by weight or more, 93% by weight or more, 94% by weight or more, 95% by weight or more, It may be 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more. The content of monomer (A1) in the monomer component is typically less than 100% by weight, and is advantageously approximately 99% by weight or less from the viewpoint of achieving a well-balanced high refractive index, low elastic modulus, and, if necessary, adhesive strength. , it is preferable that it is 98 weight% or less, more preferably 96 weight% or less, 93 weight% or less may be sufficient, and 90 weight% or less may be sufficient. In some embodiments, from the viewpoint of making it easier to realize higher adhesive properties and/or optical properties (e.g. transparency), the content of monomer (A1) in the monomer component may be less than 90% by weight. , may be less than 85% by weight, or may be less than 80% by weight.

(Monomer (A2))

In some preferred embodiments, the monomer component constituting the acrylic polymer may further contain a monomer (A2) in addition to the monomer (A1). The monomer (A2) is a monomer corresponding to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxyl group (carboxylic group-containing monomer). The hydroxyl group-containing monomer is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The carboxyl group-containing monomer is a compound containing at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer (A2) can be helpful in introducing crosslinking points into the acrylic polymer or providing appropriate cohesiveness to the adhesive. Monomer (A2) can be used individually or in combination of two or more types. The monomer (A2) is typically a monomer that does not contain an aromatic ring.

Examples of the ethylenically unsaturated group contained in the monomer (A2) include (meth)acryloyl group, vinyl group, and (meth)allyl group. A (meth)acryloyl group is preferable from the viewpoint of polymerization reactivity, and an acryloyl group is more preferable from the viewpoint of low elasticity and adhesiveness. From the viewpoint of lowering the elastic modulus of the adhesive, a compound (i.e., a monofunctional monomer) in which the number of ethylenically unsaturated groups contained in one molecule is 1 is preferably used as the monomer (A2).

In some embodiments, as the monomer (A2), a monomer having a relatively long distance between an ethylenically unsaturated group (for example, a (meth)acryloyl group) and a hydroxyl group and/or a carboxyl group can be used. As a result, in the embodiment in which the hydroxyl group and/or carboxyl group is used in the crosslinking reaction, a highly flexible crosslinked structure can be easily obtained. For example, the number of atoms (typically carbon atoms or oxygen atoms) constituting the chain (connected chain) connecting the ethylenically unsaturated group and the hydroxyl group and/or carboxyl group is 3 or more (for example, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, or 19 or more) as monomer (A2). You can use it. The upper limit of the number of atoms in the linking chain is, for example, 45 or less, 20 or less (e.g., 19 or less, 18 or less, 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, It may be 10 or less, 9 or less, or 8 or less). In addition, the number of atoms forming the connecting chain connecting the ethylenically unsaturated group and the hydroxyl group and/or the carboxyl group refers to the minimum number of atoms required to reach the hydroxyl group or the carboxyl group from the ethylenically unsaturated group. For example, when the linking chain consists of a straight chain alkylene group (i.e. -(CH ₂ ) _n -group), the number of n becomes the number of atoms constituting the linking chain. Also, for example, when the linking chain is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of 3 and n, which is the sum of the number of carbon atoms 2 and the number of oxygen atoms 1 constituting the oxyethylene group, is (3n) is the number of atoms constituting the linking chain. Although not particularly limited, such monomer (A2) includes, for example, an alkylene unit represented by -(CH ₂ ) _n - or -( C _m H _2m O) - An oxyalkylene unit (e.g., an oxyethylene unit where m is 2 in the above formula, an oxypropylene unit where m is 3 in the above formula, and oxybutyl where m is 4 in the above formula) Those having at least one ren unit) can be used. The number of the alkylene units or oxyalkylene units is not particularly limited and may be 1 or more (for example, 1 to 15, 1 to 10, 2 to 6, or 2 to 4). In addition, n in the formula representing the alkylene unit is, for example, an integer of 1 to 10, and may be 2 or more, 3 or more, 4 or more, 6 or less, or 5 or less. In the formula representing the oxyalkylene unit, m is an integer of 2 or more, for example, an integer of 2 to 4. In addition to the ethylenically unsaturated group, hydroxyl group and/or carboxyl group, alkylene unit and/or oxyalkylene unit, the monomer (A2) contains an ester bond, an ether bond, a thioether bond, an aromatic ring, an aliphatic ring, and a hetero ring ( For example, it may contain a ring containing a nitrogen atom (N), an oxygen atom (O), or a sulfur atom (S). Additionally, the alkylene unit or oxyalkylene unit may have a substituent.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylic acid, 2-hydroxypropyl (meth)acrylic acid, 4-hydroxybutyl (meth)acrylic acid, 6-hydroxyhexyl (meth)acrylic acid, and (meth)acrylic acid. Hydroxy (meth)acrylate such as 8-hydroxyoctyl, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Alkyl may be mentioned, but is not limited to these. Examples of hydroxyl group-containing monomers that can be preferably used include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl acrylate (Tg: -15°C). From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutyl acrylate with a lower Tg is more preferable. In addition, in an embodiment in which hydroxyalkyl (meth)acrylate is used as a hydroxyl group-containing monomer and the hydroxyl group is used in a crosslinking reaction, from the viewpoint of obtaining a highly flexible crosslinked structure, the hydroxyalkyl (meth)acrylate in the hydroxyalkyl (meth)acrylate is used. Monomers with a large number of carbon atoms in the alkyl group, for example, hydroxyalkyl (meth)acrylate (for example, 4-hydroxy acrylic acid) whose carbon number in the hydroxyalkyl group is 3 or more (for example, 3 to 12, preferably 4 to 10) Roxybutyl) is preferred. In a preferred embodiment, more than 50% by weight (e.g., more than 50%, more than 70%, or more than 85% by weight) of monomer (A2) may be 4-hydroxybutyl acrylate. Hydroxyl group-containing monomers can be used individually or in combination of two or more types.

In some embodiments of using a hydroxyl group-containing monomer as the monomer (A2), the hydroxyl group-containing monomer may be one or two or more types selected from compounds that do not have a methacryloyl group. Suitable examples of hydroxyl group-containing monomers that do not have a methacryloyl group include the various hydroxyalkyl acrylates described above. For example, it is preferable that more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl group-containing monomer used as the monomer (A2) is hydroxyalkyl acrylate. By using hydroxyalkyl acrylate, a hydroxy group that is helpful in providing crosslinking points and providing appropriate cohesion can be introduced into the acrylic polymer, and also in the room temperature range compared to the case of using only the corresponding hydroxyalkyl methacrylate. It is easy to obtain an adhesive with good flexibility and adhesion.

Examples of carboxylic acid-containing monomers include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. It is not limited to these. Examples of carboxyl group-containing monomers that can be preferably used include acrylic acid and methacrylic acid. Additionally, in some embodiments, from the viewpoint of reducing the elastic modulus of the adhesive, it is preferable to use, for example, a compound represented by the following formula (1) as the carboxyl group-containing monomer.

Here, R ¹ in the formula (1) is hydrogen or a methyl group. R ² and R ³ are divalent linking groups (specifically, organic groups having 1 to 20 carbon atoms (for example, 2 to 10, preferably 2 to 5)), and may be the same or different from each other. R ² and R ³ in the above formula (1) may be, for example, a divalent aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group. For example, R ² and R ³ may be alkylene having 2 to 5 carbon atoms. Specific examples of the carboxyl group-containing monomer represented by the formula (1) include, for example, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl-phthalic acid, and 2-(meth) Acryloyloxyethyl-2-hydroxyethyl-phthalic acid, 2-(meth)acryloyloxyethyl-succinic acid, 2-(meth)acryloyloxypropylhexahydrohydrogenphthalate, 2-(meth)acrylo 1oxypropylhydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrogen phthalate, etc. are mentioned. Carboxyl group-containing monomers can be used individually or in combination of two or more types. A hydroxyl group-containing monomer and a carboxyl group-containing monomer may be used together.

The content of monomer (A2) in the monomer component constituting the acrylic polymer is not particularly limited and can be set depending on the purpose. In some embodiments, the content of the monomer (A2) may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. From the viewpoint of obtaining higher usage effects, in some embodiments, the content of the monomer (A2) is preferably 1% by weight or more, may be 2% by weight or more, and may be 4% by weight or more. The upper limit of the content of the monomer (A2) in the monomer component is set so that the total of the content of the monomer (A1) does not exceed 100% by weight. In some embodiments, it is appropriate that the content of the monomer (A2) is, for example, 30% by weight or less or 25% by weight or less, and by increasing the content of the monomer (A1) relatively, it is easy to achieve a high refractive index. From the viewpoint of doing so, it is preferable to set it to 20% by weight or less, more preferably to 15% by weight or less, and may be less than 12% by weight, less than 10% by weight, or less than 7% by weight. In some preferred embodiments, from the viewpoint of reducing the elastic modulus of the adhesive, the content of the monomer (A2) is less than 5% by weight, more preferably less than 3% by weight, and may be 1.5% by weight or less.

The total content of monomer (A1) and monomer (A2) in the monomer component constituting the acrylic polymer may be, for example, 31% by weight or more, preferably 51% by weight or more, and may be 61% by weight or more, It may be 71% by weight or more. In some embodiments, the total content of monomer (A1) and monomer (A2) in the monomer component constituting the acrylic polymer is, for example, 76 weight from the viewpoint of facilitating the effect of these monomers to be appropriately exhibited. It may be % 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.

(Monomer (A3))

In some preferred embodiments, the monomer component constituting the acrylic polymer may further contain an alkyl (meth)acrylate (hereinafter also referred to as “monomer (A3)”) in addition to the monomer (A1). Monomer (A3) can help reduce the elastic modulus of the adhesive. In addition, it can be helpful in improving adhesive properties such as compatibility of additives in the adhesive and adhesive strength. Monomer (A3) can be used individually or in combination of two or more types.

As the monomer (A3), an alkyl (meth)acrylate having a straight-chain or branched alkyl group of 1 to 20 carbon atoms (i.e., C _1-20 ) at the ester terminal can be preferably used. Specific examples of C _1-20 alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. Isobutyl acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate , 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate , dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, Examples include isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate, but are not limited to these.

In some embodiments, at least a portion of the monomer (A3) is an alkyl (meth)acrylate whose Tg of the homopolymer is -20°C or lower (more preferably -40°C or lower, for example -50°C or lower). can be preferably employed. Such low Tg alkyl (meth)acrylate can be helpful in lowering the elastic modulus of the adhesive. In addition, it can be helpful in improving adhesive properties such as adhesion. The lower limit of Tg of the alkyl (meth)acrylate is not particularly limited, and may be, for example, -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the low Tg alkyl (meth)acrylate include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), heptyl acrylate, octyl acrylate, and isononyl acrylate (iNA). . In several other embodiments, an alkyl (meth)acrylate whose homopolymer Tg is more than -20°C (for example, -10°C or more) can be employed as at least a part of the monomer (A3). The upper limit of Tg of the alkyl (meth)acrylate is, for example, 10°C or less, may be 5°C or less, or may be 0°C or less. Alkyl (meth)acrylate having a Tg in this range can be helpful in adjusting the elastic modulus of the adhesive. Although it is not particularly limited, it is preferable to use the alkyl (meth)acrylate having the above Tg in combination with the above low Tg alkyl (meth)acrylate. Specific examples of the alkyl (meth)acrylate having the above Tg include lauryl acrylate (LA).

In some embodiments of using monomer (A3), it is preferable to use C _4-8 alkyl (meth)acrylate as monomer (A3). Among them, use of C _4-8 alkyl acrylate is more preferable. C _4-8 alkyl (meth)acrylate can be used individually or in combination of two or more types. By using C _4-8 alkyl (meth)acrylate, it is easy to reduce the elastic modulus of the adhesive and tend to obtain good adhesive properties (adhesive strength, etc.). In the embodiment of using C _4-8 alkyl (meth)acrylate as the monomer (A3), the ratio of C _4-8 alkyl (meth)acrylate in the alkyl (meth)acrylate contained in the monomer component is 30 weight. It is appropriate that it is % or more, preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more, and may be substantially 100% by weight.

In some embodiments of using monomer (A3), C _1-6 alkyl (meth)acrylate can be preferably used as monomer (A3). By using C _1-6 alkyl (meth)acrylate, the storage modulus of each temperature range can be adjusted. For example, the storage elastic modulus in the high temperature range can be set to be relatively high, or the difference in storage elastic modulus between the low temperature range and the high temperature range can be suppressed from increasing. Additionally, C _1-6 alkyl (meth)acrylate tends to have excellent copolymerization with monomer (A1). C _1-6 alkyl (meth)acrylate can be used individually or in combination of two or more types. As C _1-6 alkyl (meth)acrylate, C _1-6 alkyl acrylate is preferable, C _2-6 alkyl acrylate is more preferable, and C _4-6 alkyl acrylate is still more preferable. In several other embodiments, the C _1-6 alkyl (meth)acrylate is preferably C _1-4 alkyl (meth)acrylate, more preferably C _2-4 alkyl (meth)acrylate, More preferably, it is C _2-4 alkyl acrylate. A suitable example of C _1-6 alkyl (meth)acrylate includes BA.

The content of C _1-6 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight. It may be % or more. In some embodiments, the content of the C _1-6 alkyl (meth)acrylate may be 10% by weight or more, 15% by weight or more, or 20% by weight or more from the viewpoint of low elasticity, adhesive strength, etc. It may be 25% by weight or more (for example, 30% by weight or more). The upper limit of the content of C _1-6 alkyl (meth)acrylate in the monomer component is, for example, less than 50% by weight, and may be less than 35% by weight. In some embodiments, from the viewpoint of maintaining a high refractive index, the content of the C _1-6 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, and less than 17% by weight. It is more preferable, and may be less than 12% by weight, less than 7% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be practiced without substantially using C _1-6 alkyl (meth)acrylate.

In several other embodiments of using monomer (A3), C _7-12 alkyl (meth)acrylate can be preferably used as monomer (A3). The storage modulus can be preferably reduced by using C _7-12 alkyl (meth)acrylate. C _7-12 alkyl (meth)acrylate can be used individually or in combination of two or more types. As C _7-12 alkyl (meth)acrylate, C _7-10 alkyl acrylate is preferable, C _7-9 alkyl acrylate is more preferable, and C ₈ alkyl acrylate is still more preferable. Examples of C _7-12 alkyl (meth)acrylate include 2EHA, iNA, and LA, and a suitable example includes 2EHA.

The content of C _7-12 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight. It may be % or more. In some embodiments, the content of the C _7-12 alkyl (meth)acrylate may be 10% by weight or more, 15% by weight or more, or 20% by weight or more from the viewpoint of low elasticity, adhesive strength, etc. It may be 25% by weight or more (for example, 30% by weight or more). The upper limit of the content of C _7-12 alkyl (meth)acrylate in the monomer component is, for example, less than 50% by weight, and may be less than 35% by weight. In some embodiments, from the viewpoint of maintaining a high refractive index, the content of the C _7-12 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, and less than 17% by weight. It is more preferable, and may be less than 12% by weight, less than 7% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be practiced without substantially using C _7-12 alkyl (meth)acrylate.

In some embodiments of using the monomer (A3), it is preferable that at least a part of the monomer (A3) is an alkyl acrylate from the viewpoint of lowering the elastic modulus. The use of alkyl acrylate is also advantageous in terms of adhesive properties such as adhesive strength. For example, it is preferable that 50% by weight or more of monomer (A3) is alkyl acrylate, and the proportion of alkyl acrylate in monomer (A3) is more preferably 75% by weight or more, and even more preferably 90% by weight. It is % by weight or more, and substantially 100 % by weight of the monomer (A3) may be an alkyl acrylate. As the monomer (A3), only one or two or more types of alkyl acrylate may be used, and alkyl methacrylate may not be used.

In an embodiment in which the monomer component contains monomer (A3) (alkyl (meth)acrylate), the content of the alkyl (meth)acrylate in the monomer component can be set so that the use effect is appropriately exhibited. In some embodiments, the content of the alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. The upper limit of the content of monomer (A3) in the monomer component is set so that the total of the contents of monomer (A1) and (A2) does not exceed 100% by weight, for example, less than 50% by weight, and 35% by weight. It may be less than %. In some embodiments, the content of the monomer (A3) may be, for example, 24% by weight or less. Generally, the refractive index of alkyl (meth)acrylate is relatively low, so in order to increase the refractive index, it is advantageous to limit the content of monomer (A3) in the monomer component and increase the content of monomer (A1) relatively. . From this viewpoint, the content of monomer (A3) is suitably less than 23% by weight of the monomer component, preferably less than 20% by weight, more preferably less than 17% by weight, less than 12% by weight, and may be 7% by weight. It may be less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be preferably implemented in an embodiment in which monomer (A3) is not substantially used.

(Other monomers)

The monomer component constituting the acrylic polymer may, if necessary, contain monomers other than the above monomers (A1), (A2), and (A3) (hereinafter referred to as “other monomers”). The other monomers mentioned above can be used for purposes such as adjusting the Tg of the acrylic polymer, adjusting adhesive performance, and improving compatibility in the adhesive layer. The other monomers mentioned above can be used individually or in combination of two or more types.

Examples of the other monomers include monomers (functional group-containing monomers) having functional groups other than hydroxyl groups and carboxyl groups. For example, other monomers that can improve the cohesion and heat resistance of the adhesive include a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and a cyano group-containing monomer. In addition, an amide group-containing monomer (e.g., an amide group-containing monomer) can be used as a monomer that can introduce a functional group that can serve as a crosslinking point into an acrylic polymer, or can contribute to improving adhesion to an adherend or improving compatibility in an adhesive. (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amino group-containing monomers (e.g., aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), nitrogen Monomers having atom-containing rings (e.g., N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide group-containing monomers, epoxy group-containing monomers, keto group-containing monomers, isocyanate groups Containing monomers, alkoxysilyl group-containing monomers, etc. can be mentioned. In addition, among the monomers having a nitrogen atom-containing ring, there are also cases where they also correspond to monomers containing an amide group, such as N-vinyl-2-pyrrolidone. The same applies to the relationship between the monomer having the nitrogen atom-containing ring and the monomer containing an amino group.

Other monomers that can be used in addition to the functional group-containing monomers include vinyl ester monomers such as vinyl acetate; Non-aromatic ring-containing (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; Olefin-based monomers such as ethylene, butadiene, and isobutylene; Chlorine-containing monomers such as vinyl chloride; Alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and ethoxyethoxyethyl (meth)acrylate; Vinyl ether-based monomers such as methyl vinyl ether; etc. can be mentioned. A suitable example of another monomer that can be used for purposes such as improving the flexibility of the adhesive includes ethoxyethoxyethyl acrylate (alias: ethylcarbitol acrylate, homopolymer Tg: -67°C).

When using the other monomers mentioned above, the amount used is not particularly limited and can be appropriately set within the range where the total amount of monomer components does not exceed 100% by weight. From the viewpoint of facilitating the effect of improving the refractive index by using the monomer (A1), the content of the other monomers in the monomer component can be, for example, approximately 35% by weight or less, and approximately 25% by weight or less. It is appropriate to set it to (for example, 0 to 25% by weight), approximately 20% by weight or less (for example, 0 to 20% by weight) may be sufficient, and approximately 10% by weight or less (for example, 0 to 10% by weight). It is advantageous, and preferably approximately 5% by weight or less, for example approximately 1% by weight or less. The technology disclosed herein can be preferably implemented in a manner in which the monomer component does not substantially contain the other monomers described above.

In some embodiments, the monomer component constituting the acrylic polymer may have a composition in which the amount of methacryloyl group-containing monomer used is suppressed to a predetermined level or less. The usage amount of the methacryloyl group-containing monomer in the monomer component may be, for example, less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. Limiting the amount of methacryloyl group-containing monomer used in this way can be advantageous from the viewpoint of realizing an adhesive that has both flexibility and adhesiveness and a high refractive index in a good balance. The monomer component constituting the acrylic polymer may be a composition that does not contain a methacryloyl group-containing monomer (for example, a composition consisting only of an acryloyl group-containing monomer).

In some embodiments, the monomer component constituting the base polymer (e.g., acrylic polymer) of the adhesive is limited in the amount of carboxyl group-containing monomer used from the viewpoint of suppressing coloring or discoloration (e.g., yellowing) of the adhesive. there is. The amount of the carboxyl group-containing monomer used in the monomer component may be, for example, less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, or less than 0.05% by weight. This limitation in the amount of carboxyl group-containing monomer is due to corrosion of metal materials (for example, metal wiring or metal films that may be present on the adherend) that may be placed in contact with or close to the adhesive disclosed herein. It is also advantageous from the perspective of suppressing . The technology disclosed herein can be practiced in an embodiment in which the monomer component does not contain a carboxyl group-containing monomer.

For the same reason, in some embodiments, it is preferable that the monomer component constituting the base polymer of the adhesive is limited in the amount of monomers having acidic functional groups (including sulfonic acid groups, phosphoric acid groups, etc. in addition to carboxyl groups). . As the usage amount of the acidic functional group-containing monomer in the monomer component of this aspect, the above-mentioned preferable usage amount of the carboxyl group-containing monomer can be applied. The technology disclosed herein can be preferably implemented in an embodiment in which the monomer component does not contain an acidic group-containing monomer (that is, the base polymer of the adhesive is acid-free).

(Glass transition temperature Tg _T )

The monomer component constituting the base polymer (for example, an acrylic polymer) of the adhesive preferably has a composition such that the glass transition temperature Tg _T based on the composition of the monomer component is approximately 15°C or lower. In some embodiments, the glass transition temperature Tg _T is preferably 10°C or lower, more preferably 5°C or lower, further preferably 1°C or lower, and may be 0°C or lower. In several other embodiments, the glass transition temperature Tg _T may be -10°C or lower, -20°C or lower, -25°C or lower, -30°C or lower, and -35°C or lower. A low glass transition temperature Tg _T can be advantageous from the viewpoint of lowering the elastic modulus of the adhesive. In addition, the glass transition temperature Tg _T may be, for example, -60°C or higher, and from the viewpoint of facilitating high refractive index of the pressure-sensitive adhesive, it is preferably -50°C or higher, more preferably -45°C or higher, - It may be over 40℃. In some preferred embodiments, the glass transition temperature Tg _T may be greater than -30°C, may be greater than -20°C, may be greater than -10°C, or may be greater than -5°C. An adhesive having both a high refractive index and a low elastic modulus can be suitably formed by using a base polymer having a composition having a glass transition temperature Tg _T in the above range.

Here, the glass transition temperature Tg _T refers to the glass transition temperature determined by Fox's equation based on the composition of the monomer component, unless otherwise specified. As shown below, Fox's equation is a relationship between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by independently polymerizing each of the monomers constituting the copolymer.

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

As the glass transition temperature of the homopolymer used to calculate Tg, the value described in known materials such as “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) is used. For monomers for which multiple types of values are described in the Polymer Handbook, the highest value is adopted. If the Tg of the homopolymer is not described in the known data, the value obtained by the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 is used.

(Method for preparing base polymer)

In the technology disclosed herein, the method of obtaining a base polymer (for example, an acrylic polymer) composed of such a monomer component is not particularly limited, and includes solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, Known polymerization methods such as photopolymerization can be appropriately employed. For example, a solution polymerization method can be preferably employed. The polymerization temperature when performing solution polymerization can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., for example, about 20°C to 170°C (typically about 40°C to 140°C). can do.

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

The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, one or two or more types of azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. 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. can be mentioned. Another example of the polymerization initiator is a redox initiator using a combination of a peroxide and a reducing agent. The polymerization initiator can be used individually or in combination of two or more types. The amount of the polymerization initiator used may be a normal amount, and can be selected within the range of approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) per 100 parts by weight of the monomer component.

In the above polymerization, various conventionally known chain transfer agents can be used as needed. For example, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol can be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur-based chain transfer agent) may be used. Examples of non-sulfur-based chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; Terpenoids such as α-pinene and terpinolene; Styrenes such as α-methylstyrene and α-methylstyrene dimer; etc. can be mentioned. Chain transfer agents can be used individually or in combination of two or more types. When using a chain transfer agent, the usage amount can be, for example, approximately 0.01 to 1 part by weight based on 100 parts by weight of the monomer component.

The weight average molecular weight (Mw) of the base polymer (for example, an acrylic polymer) is not particularly limited, and is suitably, for example, approximately 30×10 ⁴ or more, approximately 50×10 ⁴ or more, and approximately 70×10 ⁴ It may be more than or approximately 80×10 ⁴ or more. By using a base polymer whose Mw is a predetermined value or more, it is easy to obtain an appropriate cohesive force that can exhibit the desired adhesive properties. In addition, it is possible to contain more additives such as plasticizers, so it tends to be easier to achieve the desired elastic modulus. In addition, the upper limit of the Mw of the base polymer is, for example, approximately 500 × 10 ⁴ or less, and from the viewpoint of adhesion performance, approximately 400 × 10 ⁴ or less (more preferably approximately 150 × 10 ⁴ or less, for example, approximately 130 It is preferable that it is in the range of (×10 ⁴ or less).

Here, the Mw of the polymer can be calculated by converting it to polystyrene using gel permeation chromatography (GPC). Specifically, it can be obtained by measuring under the following conditions using the product name "HLC-8220GPC" (manufactured by Tosoh Corporation) as a GPC measuring device.

[GPC measurement conditions]

Sample concentration: 0.2% by weight (tetrahydrofuran solution)

Sample injection volume: 10μL

Eluent: Tetrahydrofuran (THF)

Flow rate (flow rate): 0.6mL/min

Column temperature (measurement temperature): 40℃

column:

Sample column: 1 unit of product name “TSKguardcolumn SuperHZ-H” + 2 units of product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)

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

Detector: Differential refractometer (RI)

Standard sample: polystyrene

(plasticizer)

In some embodiments, the above-mentioned adhesives (for example, acrylic adhesives) contain a plasticizer in addition to the base polymer. By using a plasticizer, the elastic modulus of the adhesive can be effectively reduced. Additionally, in the form molded into an adhesive sheet, flexibility and conformability to deformation can be improved. Plasticizers can be used individually or in combination of two or more types.

Suitable examples of the plasticizer disclosed herein include cyclic unsaturated organic compounds having two or more double bond-containing rings. In other words, the plasticizer as a suitable example is a compound having two or more double bond-containing rings in one molecule. Accordingly, the plasticizer has at least a first double bond-containing ring and a second double bond-containing ring. By having two or more double bond-containing rings, it is possible to contribute to lowering the elasticity of the adhesive without damaging the refractive index of the adhesive or maintaining the refractive index. From the viewpoint of exerting a plasticizing effect, the number of double bond-containing rings in the plasticizer is preferably 6 or less, may be 4 or less, and may be 3 or less.

In addition, the plasticizer used in the technology disclosed herein is preferably a liquid compound at 30°C. In addition, in this specification, “liquid phase” means showing fluidity, and refers to a liquid state as a state of a substance. These compounds include compounds with a melting point of 30°C or lower. By being in a liquid state at 30°C, the plasticizer exhibits an appropriate plasticizing effect and can effectively reduce the elastic modulus of the adhesive. The plasticizer is preferably a liquid compound at 25°C, and more preferably a liquid compound at 20°C. For example, by using a liquid compound at 30°C that has two or more double bond-containing rings as a plasticizer, an adhesive that has both a high refractive index and a low elastic modulus can be preferably formed.

In an aspect in which a plasticizer having a double bond-containing ring is used, the double bond-containing ring of the plasticizer may be either a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. The plasticizer may have at least one ring selected from aromatic rings and heterocycles (heterocycles) as a double bond-containing ring. In addition, the heterocycle may have a structure contained in an aromatic ring, or may have a double bond-containing heterocycle structure different from the aromatic ring. Examples of the double bond-containing ring (typically an aromatic ring) that the plasticizer may have include a benzene ring (which may be a benzene ring forming part of a biphenyl structure or a fluorene structure); Condensed rings of naphthalene ring, indene ring, azulene ring, anthracene ring, and phenanthrene ring; It may be a carbon ring such as pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, thiophene ring. ; It may be a complex ring such as In the above heterocycle, the heteroatoms included as ring constituent atoms may be, for example, one or two or more selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatom constituting the heterocycle may be one or both of nitrogen and sulfur. The plasticizer may have a structure in which 1 or 2 or more carbon rings and 1 or 2 or more heterocycles are condensed, such as a dinaphthothiophene structure.

The double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have one or two or more substituents on the ring constituent atoms, and may not have any substituents. When having a substituent, the substituent includes an alkyl group, alkoxy group, aryloxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc. Illustrative, but not limited to these. In a substituent containing a carbon atom, the number of carbon atoms included in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, the double bond-containing ring has no substituents on ring constituent atoms, or consists of an alkyl group, an alkoxy group, an ethylenically unsaturated group (e.g., a (meth)acryloxy group), a hydroxy group, and a hydroxyalkyl group. It may be an aromatic ring having one or two or more substituents selected from the group. As the substituent, an alkyl group, an alkoxy group, or a hydroxyalkyl group is preferably used.

In some embodiments, a compound without an ethylenically unsaturated group can be preferably used as the plasticizer. As a result, deterioration of the adhesive composition due to heat or light (deterioration of leveling properties due to progression of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. Adoption of a plasticizer that does not have an ethylenically unsaturated group means that, in an adhesive sheet having an adhesive layer containing the plasticizer, the change in elastic modulus, dimensional change, or deformation (bending, wavy shape, etc.) due to the reaction of the ethylenically unsaturated group occurs. , it is also desirable from the viewpoint of suppressing the occurrence of optical distortion, etc.

As the plasticizer, a high refractive index plasticizer with a refractive index of approximately 1.50 or more can be preferably used. By using a high refractive index plasticizer, both high refractive index and low elastic modulus can be achieved at a higher level. The refractive index of the plasticizer is preferably approximately 1.51 or higher, more preferably approximately 1.53 or higher, further preferably approximately 1.55 or higher, and may be approximately 1.56 or higher, from the viewpoint of maintaining and improving the refractive index of the adhesive while lowering the elastic index. It may be approximately 1.58 or greater, approximately 1.60 or greater may be sufficient, and approximately 1.62 or greater may be sufficient. In some embodiments, from the viewpoint of ease of preparation of the adhesive composition, compatibility in the adhesive, etc., the refractive index of the plasticizer is suitably 2.50 or less, advantageously 2.00 or less, may be 1.90 or less, and may be 1.80 or less. , may be 1.70 or less.

In addition, the refractive index of the plasticizer, like the refractive index of the monomer, is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. If the nominal value of the refractive index at 25°C is provided by the manufacturer, etc., the nominal value can be adopted.

The molecular weight of the plasticizer is not particularly limited, but one having a molecular weight smaller than that of the base polymer (for example, an acrylic polymer) is usually used. From the viewpoint of facilitating the plasticizing effect, the molecular weight of the plasticizer is suitably 30,000 or less, advantageously 25,000 or less, may be less than 10,000 (for example, less than 5,000), or less than 3,000. In some embodiments, the molecular weight of the plasticizer is preferably 2000 or less, more preferably 1200 or less, even more preferably 900 or less, may be 600 or less, may be 500 or less, may be 400 or less, and may be 300 or less. It may be 250 or less (for example, 220 or less). The fact that the molecular weight of the plasticizer is not too large can be advantageous from the viewpoint of improving compatibility within the adhesive layer. In addition, from the viewpoint of making it easy to achieve sufficient plasticizing effect, the molecular weight of the plasticizer is suitably 100 or more, preferably 130 or more, more preferably 150 or more, may be 170 or more, may be 200 or more, and may be 220 or more. It can be 250 or more. It is preferable that the molecular weight of the plasticizer is not too low from the viewpoint of heat resistance performance of the adhesive sheet and suppression of contamination of the adherend. In some embodiments, the molecular weight of the plasticizer is, for example, 300 or more, suitably 315 or more, and may be 350 or more. Since plasticizers with large molecular weight are difficult to vaporize, it is easy to obtain an adhesive that can exhibit stable properties by using a plasticizer with a large molecular weight in an adhesive. Additionally, plasticizers with large molecular weight have difficulty moving within the adhesive. Therefore, for example, it is difficult for the plasticizer to migrate to the surface of the adhesive, causing events that affect the adhesive properties. The molecular weight of the plasticizer is more preferably 400 or more, further preferably 450 or more, particularly preferably 500 or more, and may be 530 or more.

Additionally, as the molecular weight of the plasticizer, the molecular weight calculated based on the chemical structure is used. If a nominal value of molecular weight is provided by the manufacturer, etc., the nominal value can be adopted.

In some embodiments, the plasticizer is a compound having a structure in which two or more non-fused double bond-containing rings (typically aromatic rings) are bonded through a linking group, or a compound having a structure in which two or more non-fused double bond-containing rings (typically aromatic rings) are bonded together through a linking group. ) Compounds having a structure in which these are chemically bonded directly (i.e., without going through other atoms), compounds having a condensed double bond-containing ring (typically aromatic ring) structure, compounds having a fluorene structure, and dinaphthothiophene structures. compounds having a dibenzothiophene structure, etc., and one or two or more types selected from compounds that are liquid at 30°C (for example, 25°C or 20°C) may be used.

As a plasticizer, in an aspect of using a compound having a structure in which two or more non-fused double bond-containing rings are bonded through a linking group, the linking group is, for example, an oxy group (-O-), a thioxy group (-S-) , oxyalkylene group (for example -O-(CH ₂ ) _n -group, where n is 1 to 3, preferably 1), thiooxyalkylene group (for example-S-(CH ₂ ) _n -group , where n is 1 to 3, preferably 1), a straight chain alkylene group (i.e. -(CH ₂ ) _n -group, where n is 1 to 6, preferably 1 to 3), the oxyalkylene group, the thio The alkylene group in the oxyalkylene group and the linear alkylene group may be a partially halogenated or fully halogenated group. The linking group may have a siloxane bond (-SiOR-) or an ester bond. In the plasticizer, the linking group connecting the first double bond-containing ring (non-condensed ring) and the second double bond-containing ring (non-condensed ring) may be selected from the same group as above. From the viewpoint of lowering the elastic modulus of the adhesive, suitable examples of the linking group include an oxy group, a thioxy group, an oxyalkylene group, and a straight chain alkylene group. The number of atoms of the linking group is not particularly limited, and is, for example, 1 to 30, may be 1 to 25, may be 1 to 20, is suitably 1 to 18, preferably 1 to 12, More preferably it is 1 to 10, further preferably 1 to 8, especially preferably 1 to 5, 1 to 3 may be sufficient, and 1 or 2 may be sufficient. In addition, the number of atoms of the linking group refers to the minimum number of atoms required to reach from one non-fused double bond-containing ring to the other non-fused double bond-containing ring. For example, when the linking group consists of a straight chain alkylene group (i.e. -(CH ₂ ) _n -group), the number of n becomes the number of atoms of the linking group. Also, for example, if the linking group is an oxyethylene group (i.e. -(C ₂ H ₄ O) _n -group), the product of 3 and n, which is the sum of the number of carbon atoms 2 and the number of oxygen atoms 1 constituting the oxyethylene group (3n ) is the number of atoms of the linking group. Suitable examples of the above compounds include compounds having a phenoxybenzyl group. Examples of the compounds include phenoxybenzyl (meth)acrylate (e.g., m-phenoxybenzyl (meth)acrylate), phenoxybenzyl alcohol, oxybis[(alkoxyalkyl)benzene] (e.g., 4 , 4'-oxybis[(methoxymethyl)benzene]), and the like. Other examples of the compounds include silicone-based plasticizers (specifically, siloxane compounds) described later.

The compound having a structure in which two or more double bond-containing rings (non-condensed rings) are directly chemically bonded may be, for example, a biphenyl structure-containing compound, a triphenyl structure-containing compound, etc. Additionally, examples of compounds having a condensed double bond-containing ring structure include naphthalene ring-containing compounds and anthracene ring-containing compounds. Specific examples include 1-acetonaphthone. In addition, since the compound having the fluorene structure includes a structural portion in which two benzene rings are directly chemically bonded, it is included in the concept of a compound having a structure in which two or more double bond-containing rings (non-condensed rings) are directly chemically bonded. do. The compound having the dinaphthothiophene structure includes a naphthalene structure and has a structure in which a thiophene ring and two naphthalene structures are condensed, and thus is included in the concept of the compound having the condensed double bond-containing ring structure. The compound having the dibenzothiophene structure is included in the concept of the compound having the condensed double bond-containing ring structure in that it has a structure in which a thiophene ring and two benzene rings are condensed.

In some embodiments, a silicone-based plasticizer is used as the plasticizer. By using a silicone-based plasticizer, it is easy to obtain a stable plasticization effect and also easy to obtain high adhesive strength, so the refractive index, flexibility, and adhesive strength of the adhesive can be improved in a good balance. The silicone-based plasticizer is not particularly limited, and for example, a compound having one or two or more double bond-containing rings can be used. Additionally, the silicone-based plasticizer is preferably a liquid compound at 30°C. The silicone-based plasticizer is specifically a siloxane compound, and the number of Si atoms the compound has is 1 or more (typically 2 or more), and the upper limit is not particularly limited, and may be about 10 or less, for example. In one molecule of the silicone plasticizer, the Si atom and the double bond-containing ring may or may not be directly bonded. It is preferable that at least one of the Si atoms is directly bonded to at least one double bond-containing ring. Silicone-based plasticizers can be used individually or in combination of two or more types.

In some embodiments, as a silicone-based plasticizer, a siloxane compound containing 2 to 5 Si atoms, and at least one of the Si atoms having two or more double bond-containing rings bonded to the Si atom, may be used. there is. A silicone-based plasticizer made of a siloxane compound having such a structure can exhibit a plasticizing effect based on the flexibility of the siloxane structure, has a Si atom number of 2 to 5, and has two or more double bond-containing rings bonded to each other. By having at least one atom, the ease of mixing and compatibility with the material to be plasticized and the stability of the plasticizing effect (for example, a low rate of increase in elastic modulus when stored under moist heat) can be achieved in a good balance. From the viewpoint of chemical stability, the siloxane compound preferably does not have a hydrogen atom bonded to a Si atom. That is, siloxane compounds that do not have Si-H bonds are preferred.

When the number of Si atoms of the siloxane compound is 3 or more, the siloxane compound may be linear or cyclic, but is preferably a linear siloxane compound from the viewpoint of suppressing volatilization. The linear siloxane compound having 3 or more Si atoms may be linear or branched, but is preferably linear from the viewpoint of obtaining a higher plasticization effect. Hereinafter, unless otherwise specified, a siloxane compound having 3 or more Si atoms means a chain-shaped (typically linear) siloxane compound having 3 or more Si atoms.

In some embodiments, the double bond-containing ring of the silicone-based plasticizer may be a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. The plasticizer is a double bond-containing ring and may have at least one ring selected from aromatic rings and heterocycles (heterocycles). In addition, the heterocycle may have a structure contained in an aromatic ring, or may have a double bond-containing heterocycle structure different from the aromatic ring. The double bond-containing ring (typically an aromatic ring) that the plasticizer may have may be a carbon ring such as a benzene ring or a naphthalene ring, a pyridine ring, an imidazole ring, a triazole ring, an oxazole ring, a thiazole ring, a thiophene ring, etc. It may be a complex form of . In the above heterocycle, the heteroatoms included as ring constituent atoms may be, for example, one or two or more selected from the group consisting of nitrogen, sulfur, and oxygen. In some embodiments, the heteroatom constituting the heterocycle may be one or both of nitrogen and sulfur.

The double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have one or two or more substituents on the ring constituent atoms, and may not have any substituents. When having a substituent, examples of the substituent include an alkyl group, an alkoxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, and a glycidyloxy group. It is not limited to. In a substituent containing a carbon atom, the number of carbon atoms included in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some embodiments, each double bond-containing ring of the silicone-based plasticizer is each independently a group consisting of an aromatic ring having no substituent on the ring constituent atom, and an alkyl group, an alkoxy group, a hydroxy group, and a hydroxyalkyl group (preferably , an alkyl group, and an alkoxy group). For example, the double bond-containing ring of the silicone-based plasticizer is selected from aromatic rings (preferably carbocyclic rings) that do not have substituents on ring constituent atoms. In some preferred embodiments, all double bond-containing rings of the silicone-based plasticizer are benzene rings.

The number of Si atoms in the siloxane compound is preferably 3 or more from the viewpoint of ease of exerting the plasticizing effect and its stability (for example, suppression of an increase in elastic modulus due to volatilization of the plasticizer from the material mixed with the plasticizer). do. In addition, the number of Si atoms in the siloxane compound is preferably 4 or less, and more preferably 3 or less from the viewpoint of compatibility in the adhesive. Among them, a silicone-based plasticizer in which the Si atom number of the siloxane compound is 3, that is, a silicone-based plasticizer made of a trisiloxane compound, is preferable.

In some embodiments, the number of double bond-containing rings (e.g., benzene rings with or without substituents) of the siloxane compound is at least 2, and the heat resistance of the plasticizing effect (e.g., wet heat From the viewpoint of a low rate of increase in elastic modulus with respect to storage under conditions, the value is preferably 3 or more, more preferably 4 or more, and may be 5 or more. In addition, the number of double bond-containing rings in the siloxane compound is typically 2n+2 or less, with n being the number of Si atoms in the siloxane compound, and from the viewpoint of enhancing the plasticization effect, it is suitably 2n+1 or less, It is preferably 2n or less, may be 2n-1 or less, and may be 2n-2 or less. For example, in an embodiment where the siloxane compound is a trisiloxane compound, the number of double bond-containing rings that the trisiloxane compound has is typically 8 or less, for example, may be 2 or more and 7 or less, or 3 or more and 7 or less. It may be 4 or more and 7 or less. Among them, trisiloxane compounds in which the number of double bond-containing rings (for example, unsubstituted benzene rings) are 4 or more and 6 or less (for example, 4 or 5) are preferable.

In some embodiments, at least one of the Si atoms contained in the siloxane compound (typically, the Si atom constituting the siloxane chain) is a Si atom to which two or more double bond-containing rings are bonded. From the viewpoint of improving the stability of the plasticizing effect, the number of Si atoms to which two or more double bond-containing rings are bonded in the siloxane compound may be two or more. In the siloxane compound having 3 or more Si atoms, the number of Si atoms to which two or more double bond-containing rings are bonded may be 2 or more, or 3 or more. In addition, with the number of Si atoms in the siloxane compound being n, the number of Si atoms to which two or more double bond-containing rings are bonded may be n or less. It may be , it may be n-1 or less, and it may be n-2 or less. In some embodiments, from the viewpoint of enhancing the plasticizing effect, at least one of the Si atoms contained in the siloxane compound (preferably a siloxane compound having 3 or more Si atoms) contains a double bond bonded to the Si atom. The number of rings is 1 or 0. For example, it is a linear siloxane compound having 3 or more and 5 or less Si atoms, and the Si atoms at both terminals each independently have two or three (preferably two) double bond-containing rings, and A siloxane compound having a structure in which each Si atom independently has one double bond-containing ring or does not have a double bond-containing ring is preferred.

In some embodiments, the siloxane compound may contain a Si atom to which a group other than the double bond-containing ring is bonded. Groups other than the double bond-containing ring include an alkyl group, aralkyl group, alkoxy group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), fluoroalkyl group, hydroxyl group, hydroxyalkyl group, hydroxyalkyloxy group, epoxy group, Examples include, but are not limited to, glycidyloxy group, amino group, monoalkylamino group, dialkylamino group, carboxyl group, carboxyalkyl group, and mercapto group. In the substituent containing a carbon atom, the number of carbon atoms included in the substituent is, for example, 1 to 8, preferably 1 to 4, more preferably 1 to 3, for example 1 or It could be 2. Groups other than the double bond-containing ring bonded to each Si atom included in the siloxane compound may each independently be selected from the group consisting of the groups exemplified above.

In some embodiments, it is preferable that the siloxane compound does not have an ethylenically unsaturated group (including those where the double bond in the double bond-containing ring is an ethylenic double bond). A silicone-based plasticizer consisting of a siloxane compound without an ethylenically unsaturated group is advantageous from the viewpoint of stability of the plasticizing effect caused by the plasticizer, and also from the viewpoint of storage stability of an adhesive sheet having an adhesive layer containing the silicone-based plasticizer. It is also desirable from the viewpoint of suppressing changes in elastic modulus, dimensional changes and deformations (bending, waviness, etc.), and optical distortions caused by the reaction of sexually unsaturated groups.

In some embodiments of the silicone-based plasticizer disclosed herein, at least one of the Si atoms contained in the siloxane compound (at least two in the case of a siloxane compound having a Si atom number of 3 or more) is a Si atom from the viewpoint of enhancing the plasticizing effect. It is preferred to have at least one methyl group on it. For example, it is preferable that the Si atoms located at both ends of the siloxane chain each independently have one or two (more preferably one) methyl groups. In some preferred embodiments, each of the Si atoms contained in the siloxane compound independently has one or two methyl groups. According to a silicone-based plasticizer made of a siloxane compound with such a structure, the plasticizing effect is achieved by the flexibility of the siloxane structure, and the stability of the plasticizing effect is achieved by having a structure in which two or more double bond-containing rings are bonded to at least one Si atom. can be achieved in a good balance.

In some embodiments, the number of Si atoms contained in the siloxane compound is set to n, and the sum of the number of substituents bonded to these Si atoms (hereinafter also referred to as the total number of substituents) is typically 2n. +2, at least two of which are double bond-containing rings. In some embodiments, the ratio SR of the number of double bond-containing rings (preferably aromatic carbocyclic rings, such as benzene rings) among the total number of substituents in the silicone plasticizer is at least 16%, and may be 20% or more. It may be 25% or more. As the ratio SR increases, the heat resistance of the silicone-based plasticizer and the stability of the plasticizing effect by the silicone-based plasticizer tend to generally improve. In some embodiments, the ratio SR is advantageously 33% or more, preferably 40% or more, more preferably 50% or more (for example, 60% or more), may be 65% or more, and may be 75% or more. It can be more than that. The above ratio SR may be 100%, but from the viewpoint of ease of mixing and compatibility, it is advantageous to be 85% or less, preferably 80% or less, may be 75% or less, may be 65% or less, and may be 60% or less (e.g. 50% or less) may be sufficient.

In some embodiments, the molecular weight of the silicone plasticizer (specifically, the siloxane compound) is suitably 400 or more, advantageously 430 or more, preferably 460 or more, and may be 490 or more from the viewpoint of stability of the plasticizing effect. It can be 520 or higher. In addition, from the viewpoint of plasticization effect, ease of mixing, compatibility, etc., the molecular weight of the siloxane compound is suitably 900 or less, advantageously 850 or less, preferably 700 or less, more preferably 650 or less, and even 600 or less. It may be 560 or less, 540 or less, or 500 or less.

As the molecular weight of the siloxane compound, a molecular weight calculated based on the chemical structure or a value measured using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) can be used. If a nominal value of molecular weight is provided by the manufacturer, etc., the nominal value can be adopted.

The refractive index of the silicone-based plasticizer disclosed herein is not particularly limited and may be, for example, in the range of 1.30 to 1.80. From the viewpoint of suppressing a decrease in the refractive index of the material to which the plasticizer is mixed (for example, an adhesive) while achieving low elasticity, the silicone-based plasticizer in some embodiments preferably has a refractive index of 1.45 or more, and is preferably 1.50 or more. , it is more preferable that it is 1.52 or more (for example, 1.53 or more or 1.54 or more), and it is even more preferable that it is 1.55 or more (for example, 1.56 or more or 1.57 or more). In addition, the refractive index of the silicone-based plasticizer may be, for example, 1.70 or less, 1.65 or less, or 1.60 or less from the viewpoint of ease of mixing and compatibility.

In some embodiments, an ethylene glycol-based compound having two or more double bond-containing rings in one molecule can be used as a plasticizer. The number of oxyethylene units (that is, -(C ₂ H ₄ O)- units) that the ethylene glycol-based compound has is, for example, 1 to 10, may be 1 to 6, or may be 2 to 4. The ethylene glycol-based compound is a ring in which two or more non-fused double bond-containing rings are bonded through an oxyethylene unit as a linking group (for example, 1 to 10, suitably 1 to 6, and further 2 to 4 oxyethylene units). It may be a compound with a structure. These compounds may have one or two or more ester groups. Examples of the ethylene glycol-based compound include compounds having a structure in which two or more benzoic acids are linked to ethylene glycol, diethylene glycol, triethylene glycol, or polyethylene glycol by an ester bond.

Additionally, the technology disclosed herein can be implemented without using the ethylene glycol-based compound as a plasticizer or with limiting the amount of its use. For example, the content ratio of the ethylene glycol-based compound in the plasticizer contained in the adhesive may be less than 90% by weight. The content ratio of the ethylene glycol-based compound in the plasticizer may be less than 50% by weight, less than 10% by weight, less than 3% by weight, or less than 1% by weight, and the adhesive is a plasticizer containing the ethylene glycol-based compound. It does not have to contain substantially. Similarly, in the adhesive, the amount of the ethylene glycol-based compound used may be less than 0.5 parts by weight, and may be less than 0.1 parts by weight, per 100 parts by weight of the base polymer (e.g., acrylic polymer).

In several other embodiments, liquid rosins such as liquid rosin ester and liquid camphenenphenol can be used as the plasticizer. The liquid rosins (for example, liquid rosin esters) may correspond to compounds having the condensed double bond-containing ring structure.

In addition, as a plasticizer, one or two or more types of known plasticizers (for example, phthalic acid ester series, terephthalic acid ester series, adipic acid ester series, adipic acid polyester, benzoic acid glycol ester, etc.) may be used.

The amount of plasticizer used is not particularly limited and can be set depending on the purpose. From the viewpoint of reducing the elastic modulus of the adhesive, the amount of plasticizer used per 100 parts by weight of the base polymer (e.g., acrylic polymer) may be, for example, 1 part by weight or more, or 10 parts by weight or more. In some preferred embodiments, the amount of plasticizer used per 100 parts by weight of the base polymer may be greater than 15 parts by weight, may be 20 parts by weight or more, may be 30 parts by weight or more (for example, more than 30 parts by weight), or more. It is preferably 40 parts by weight or more, more preferably 50 parts by weight or more, especially preferably 60 parts by weight or more, and may be 75 parts by weight or more, and may be 90 parts by weight or more. For example, when using the above-mentioned ethylene glycol-based compound as a plasticizer, it is preferable to use it in an amount exceeding 30 parts by weight (for example, 40 parts by weight or more, and even 50 parts by weight or more) with respect to 100 parts by weight of the base polymer. . In addition, from the viewpoint of achieving both high refractive index and low elasticity of the adhesive in a good balance, it is appropriate that the amount of plasticizer used per 100 parts by weight of the base polymer is approximately 200 parts by weight or less, and is preferably 150 parts by weight or less. It is more preferable to set it to 120 parts by weight or less, and may be 100 parts by weight or less, 80 parts by weight or less, and 70 parts by weight or less. In some embodiments that place greater emphasis on adhesive properties, the amount of plasticizer used may be 45 parts by weight or less, or 35 parts by weight or less, per 100 parts by weight of the base polymer.

(Additive (H _RO ))

The adhesive disclosed herein may, if desired, contain an organic material with a higher refractive index than the base polymer (for example, an acrylic polymer) as an additive. Hereinafter, such organic materials may be referred to as “additive (H _RO ).” Here, “H _RO ” indicates that it is an organic material with a high refractive index. By using an additive (H _RO ), an adhesive that more appropriately achieves both refractive index and adhesive properties (peel strength, flexibility, etc.) can be realized. The organic material used as the additive (H _RO ) may be a polymer or a non-polymer. Additionally, it may or may not have a polymerizable functional group. Additionally, in this specification, the additive (H _RO ) is defined as being different from the compound used as the above-mentioned plasticizer. Therefore, specifically, the additive (H _RO ) is not liquid at 30°C (for example, 25°C or 20°C). Additives (H _RO ) can be used individually or in combination of two or more types.

The refractive index of the additive (H _RO ) can be set in an appropriate range in relation to the refractive index of the base polymer (for example, an acrylic polymer), and is therefore not limited to a specific range. The refractive index of the additive (H _RO ) is, for example, greater than 1.55, greater than 1.56, or greater than 1.57, and can be selected from a range higher than the refractive index of the base polymer. From the viewpoint of increasing the refractive index of the adhesive, in some embodiments, the refractive index of the additive ( _HRO ) is advantageously 1.58 or more, preferably 1.60 or more, more preferably 1.63 or more, may be 1.65 or more, and may be 1.70 or more. It may be 1.75 or more. By using an additive (H _RO ) with a higher refractive index, the target refractive index can be achieved even by using a smaller amount of the additive (H _RO ). This is desirable from the viewpoint of suppressing deterioration of adhesive properties and optical properties. The upper limit of the refractive index of the additive ( _HRO ) is not particularly limited, but is, for example, 3.000 or less, and may be 2.500 or less, from the viewpoint of compatibility in the adhesive and ease of coexistence of high refractive index and flexibility suitable as an adhesive. It may be 2.000 or less, 1.950 or less, 1.900 or less, and 1.850 or less.

In addition, the refractive index of the additive (H _RO ), like the refractive index of the monomer, is measured using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. If the nominal value of the refractive index at 25°C is provided by the manufacturer, etc., the nominal value can be adopted.

The difference between the refractive index n _b of the additive (H _RO ) and the refractive index n _a of the base polymer (for example, an acrylic polymer), that is, n _b -n _a (hereinafter also referred to as “Δn _A ”), is set to be greater than 0. In some embodiments, Δn _A may be, for example, 0.02 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more. By selecting the base polymer and additive (H _RO ) so that Δn _A becomes larger, the refractive index improvement effect by use of the additive (H _RO ) tends to increase. In addition, from the viewpoint of compatibility of the additive ( _HRO ) in the adhesive, in some embodiments, Δn _A may be, for example, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.35. The following may be acceptable.

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

The molecular weight of the organic material used as the additive ( _HRO ) is not particularly limited and can be selected depending on the purpose. From the viewpoint of achieving a good balance between the effect of increasing the refractive index and other properties (e.g., optical properties such as flexibility and haze suitable for an adhesive), in some embodiments, the molecular weight of the additive ( _HRO ) is approximately 10000. It is suitable to be less than 5000, more preferably less than 3000 (for example, less than 1000), less than 800, less than 600, less than 500, and less than 400. The fact that the molecular weight of the additive ( _HRO ) is not too large can be advantageous from the viewpoint of improving compatibility in the adhesive. In addition, the molecular weight of the additive ( _HRO ) may be, for example, 130 or more, or 150 or more. In some embodiments, the molecular weight of the additive ( _HRO ) is preferably 170 or more, more preferably 200 or more, may be 230 or more, or 250 or more from the viewpoint of increasing the refractive index of the additive ( _HRO ). It may be 270 or more, 500 or more, 1000 or more, or 2000 or more. In some embodiments, a polymer having a molecular weight of about 1,000 to 10,000 (for example, 1,000 to 5,000) can be used as the additive (H _RO ).

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

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

The aromatic ring possessed by the organic compound having the aromatic ring (hereinafter also referred to as “aromatic ring-containing compound”) used as the additive (H _RO ) may be selected from the same group as the aromatic ring possessed by the compound used as the monomer (A1). there is.

The aromatic ring may have one or two or more substituents on the ring constituent atoms, and does not need to have a substituent. When having a substituent, the substituent includes an alkyl group, alkoxy group, aryloxy group, hydroxyl group, halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc. Illustrative, but not limited to these. In the substituent containing a carbon atom, the number of carbon atoms included in the substituent is, for example, 1 to 10, advantageously 1 to 6, preferably 1 to 4, more preferably 1 to 10. 3, for example 1 or 2. In some embodiments, the aromatic ring may have no substituents on ring constituent atoms, or may be an aromatic ring with one or two or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (for example, a bromine atom). there is.

Examples of aromatic ring-containing compounds that can be used as additives (H _RO ) include: compounds that can be used as monomers (A1); An oligomer containing a compound that can be used as a monomer (A1) as a monomer unit; From the compounds that can be used as monomers (A1), a group having an ethylenically unsaturated group (which may be a substituent bonded to a ring-membered atom) or a hydrogen atom or an ethylenically unsaturated group, excluding the portion of that group constituting the ethylenically unsaturated group, Compounds with a structure substituted with a group that does not have a group (for example, a hydroxyl group, an amino group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkyloxy group, a glycidyloxy group, etc.); etc., and those that do not correspond to the plasticizers disclosed herein may be mentioned, but are not limited to these.

In some embodiments, the additive ( _HRO ) is an organic compound having two or more aromatic rings in one molecule (hereinafter also referred to as a “compound containing multiple aromatic rings”) because a high refractive index effect can easily be obtained. ) can be preferably employed. The compound containing multiple aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. In addition, the compound containing multiple aromatic rings may be a polymer or a non-polymer. In addition, the polymer is an oligomer containing a plurality of aromatic ring-containing monomers as monomer units (preferably an oligomer with a molecular weight of approximately 5000 or less, more preferably approximately 1000 or less. For example, a low polymer of about 2 to 5 polymers) It can be. The oligomers include, for example: homopolymers of monomers containing multiple aromatic rings; A copolymer of two or more types of aromatic ring-containing monomers; A copolymer of one or more types of aromatic ring-containing monomers and other monomers; It may be, etc. The other monomer may be an aromatic ring-containing monomer that does not correspond to a monomer containing multiple aromatic rings, may be a monomer that does not have an aromatic ring, or may be a combination thereof.

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 through a linking group, and compounds having a structure in which two or more non-fused aromatic rings are chemically bonded directly (i.e., without passing through other atoms). , compounds having a condensed aromatic ring structure, compounds having a fluorene structure, compounds having a dinaphthothiophene structure, compounds having a dibenzothiophene structure, etc. A compound containing multiple aromatic rings can be used individually or in combination of two or more types.

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

In some embodiments, a compound that does not have an ethylenically unsaturated group can be preferably used as the additive (H _RO ). As a result, deterioration of the adhesive composition due to heat or light (deterioration of leveling properties due to progression of gelation or increase in viscosity) can be suppressed, and storage stability can be improved. Adopting an additive (H _RO ) that does not have an ethylenically unsaturated group means that, in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the additive (H _RO ), dimensional changes or deformations (bending, It is also desirable from the viewpoint of suppressing the occurrence of optical distortion (wave shape, etc.), etc.

In the aspect of using an oligomer as an additive ( _HRO ), the oligomer can be obtained by polymerizing the corresponding monomer component by a known method. When the oligomer is produced by radical polymerization, polymerization can be performed by appropriately adding a polymerization initiator, chain transfer agent, emulsifier, etc. used in radical polymerization to the monomer component. The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be appropriately selected and used. Additionally, the weight average molecular weight of the oligomer can be controlled by the usage amounts of the polymerization initiator and chain transfer agent, and the reaction conditions, and the usage amounts are appropriately adjusted depending on their types.

Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, α-thioglycerol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, and 2,3-dimer. Capto-1-propanol, etc. can be mentioned. Chain transfer agents may be used individually, or two or more types may be mixed. The amount of the chain transfer agent used can be set so that an oligomer with a desired weight average molecular weight can be obtained depending on the composition of the monomer component used in the synthesis of the oligomer, the type of the chain transfer agent, etc. In some embodiments, the amount of chain transfer agent used for oligomer synthesis is preferably approximately 15 parts by weight or less, and may be 10 parts by weight or less, or approximately 5 parts by weight or less. It's okay. The lower limit of the amount of chain transfer agent used for oligomer synthesis is not particularly limited, but may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more. , may be 1 part by weight or more.

The amount of additive ( _HRO ) used (if multiple types of compounds are used, their total amount) per 100 parts by weight of the base polymer (e.g. acrylic polymer) is not particularly limited as long as it exceeds 0 parts by weight, depending on the purpose. You can set it. In some embodiments, the amount of additive ( _HRO ) used per 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less to increase the refractive index of the adhesive and suppress deterioration of the adhesive properties and optical properties. From the viewpoint of achieving good balance, it is advantageous to set it to 60 parts by weight or less, and preferably to set it to 45 parts by weight or less. In some embodiments that place more emphasis on adhesive properties or optical properties, the amount of additive ( _HRO ) used per 100 parts by weight of the base polymer may be, for example, 30 parts by weight or less, 20 parts by weight or less, and 15 parts by weight or less. It may be less than or equal to 10 parts by weight. In addition, from the viewpoint of increasing the refractive index of the adhesive, the amount of additive (H _RO ) used per 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, and it is advantageous to set it to 3 parts by weight or more, and 5 It is preferably more than 7 parts by weight, 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, and 20 parts by weight or more.

(Cross-linking agent)

In the technology disclosed herein, the adhesive composition used to form the adhesive may contain a crosslinking agent as needed for purposes such as adjusting the cohesive force of the adhesive. As the crosslinking agent, crosslinking agents known in the adhesive field 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 them, isocyanate-based crosslinking agents and epoxy-based crosslinking agents can be preferably employed. Other examples of crosslinking agents include monomers having two or more ethylenically unsaturated groups in one molecule, that is, polyfunctional monomers. The crosslinking agent can be used individually or in combination of two or more types.

As the isocyanate-based crosslinking agent, bifunctional or higher isocyanate compounds can be used, for example, aliphatic polys such as trimethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), and dimer acid diisocyanate. isocyanates; Alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), and 1,3-bis(isocyanatomethyl)cyclohexane; Aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate (XDI); Polyisocyanate modified product ( For example, isocyanurate form of HDI, allophanate form of HDI, etc.); etc. can be mentioned. Examples of commercial products include Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N, Takenate D178NL (above, manufactured by Mitsui Chemicals), Sumidur T80, Sumidur L, Desmodur N3400 ( (above, manufactured by Sumika Bayer Urethane Corporation), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX, Coronate 2770 (above, manufactured by Tosoh Corporation), brand name Duranate A201H (above, Asahi Kasei Corporation) j), etc. Isocyanate compounds can be used individually or in combination of two or more types. You may use a bifunctional isocyanate compound and a trifunctional or more isocyanate compound together.

As an epoxy-based crosslinking agent, for example, bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1, 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamineglycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. These can be used individually or in combination of two or more types.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and neopentyl glycol di( Meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexane Dioldi(meth)acrylate, 1,12-dodecanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl (meth)acrylate, divinylbenzene, bisphenol A di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, hexyldiol di(meth)acrylate, etc. I can hear it. Polyfunctional monomers can be used individually or in combination of two or more types.

In some embodiments, at least part of the crosslinking agent is a bifunctional crosslinking agent having two crosslinking reactive groups (for example, isocyanate groups) per molecule. By using a bifunctional crosslinking agent, it is easy to form a flexible crosslinked structure. The bifunctional crosslinking agent can be used individually or in combination of two or more types. In addition, the bifunctional crosslinking agent may be used in combination with a trifunctional or higher crosslinking agent.

In some embodiments, an acyclic crosslinking agent (also referred to as a chain crosslinking agent) that does not have a ring structure such as an aromatic ring or an aliphatic ring is preferably used as the crosslinking agent. For example, among the above-mentioned isocyanate-based crosslinking agents, it is preferable to use isocyanate-based compounds that do not have ring structures such as aromatic rings and isocyanurate rings. By using an acyclic isocyanate-based compound as a crosslinking agent, it is easy to form a crosslinking agent with high flexibility. Specific examples of the acyclic isocyanate include aliphatic isocyanate compounds (e.g., PDI and HDI) and modified forms of aliphatic isocyanate compounds (e.g., allophanate linkage, biuret linkage, urea linkage, and carbodiyl compound of PDI and HDI). and polyisocyanate modified products modified by mead bonds. The acyclic crosslinking agent can be used individually or in combination of two or more types. In some preferred embodiments, an acyclic bifunctional crosslinking agent may be used as the crosslinking agent.

In some embodiments, a crosslinking agent in which the distance between one crosslinking reactive group (for example, an isocyanate group) and the other crosslinking reactive group in one molecule is relatively long can be used. As a result, a flexible crosslinked structure having a length of a predetermined length or more is formed. For example, in one molecule of the crosslinking agent, a compound in which the number of atoms constituting the linking chain connecting one crosslinking reactive group to another crosslinking reactive group is 10 or more (for example, 12 or more or 14 or more) can be used as the crosslinking agent. The upper limit of the number of atoms forming the linking chain is not particularly limited because it can be prepared by polymerization or the like depending on the purpose, and is, for example, 2000 or less, may be 1000 or less, may be 500 or less, may be 100 or less, and may be 50 or less. It may be 20 or less, or it may be 30 or less, or it may be 20 or less. In addition, the number of atoms in the linking chain connecting the crosslinking reactive groups refers to the number of atoms from one crosslinking reactive group to another crosslinking reactive group in one molecule of the crosslinking agent (when having 3 or more crosslinking reactive groups, the crosslinking reactive group closest to the one crosslinking reactive group refers to the minimum number of atoms required to reach a reactive group. The crosslinking agent having the above linking chain can be used individually or in combination of two or more types. In some preferred embodiments, an acyclic bifunctional crosslinking agent may be used as the crosslinking agent. Examples of commercial products of the crosslinking agent include Coronate 2770 (manufactured by Tosoh Corporation), Takenate D178NL (manufactured by Mitsui Chemicals), Duranate A201H (Asahi Kasei Corporation), and the like.

When using a crosslinking agent (which may be a multifunctional monomer), the amount used is not particularly limited, and can be, for example, in the range of 0.001 parts by weight to 5.0 parts by weight based on 100 parts by weight of the base polymer. From the viewpoint of improving adhesion to the adherend, in some embodiments, the amount of crosslinking agent used per 100 parts by weight of the base polymer is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and 1.0 parts by weight. It may be less than 0.5 part by weight, or less than 0.2 part by weight. In addition, from the viewpoint of appropriately demonstrating the effect of using the crosslinking agent, in some embodiments, the amount of the crosslinking agent used per 100 parts by weight of the base polymer may be, for example, 0.005 parts by weight or more, or 0.01 parts by weight or more, It may be 0.05 parts by weight or more, 0.08 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, and 0.4 parts by weight or more.

In order to advance the crosslinking reaction more effectively, a crosslinking catalyst may be used. Examples of crosslinking catalysts include metal crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, zirconium tetraacetylacetonato, ferric nasem, butyltin oxide, and dioctyltin dilaurate. . Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferable. The amount of crosslinking catalyst used is not particularly limited. The amount of crosslinking catalyst used per 100 parts by weight of the base polymer can be, for example, in the range of approximately 0.0001 part by weight to 1 part by weight, taking into account the balance between the speed of the crosslinking reaction rate and the length of the pot life of the adhesive composition. , it is desirable to set it in the range of 0.001 parts by weight or more and 0.5 parts by weight or less.

The adhesive composition may contain a compound that generates keto-enol tautomerism as a crosslinking retardant. Thereby, the effect of extending the pot life of the adhesive composition can be realized. For example, in an adhesive composition containing an isocyanate-based crosslinking agent, a compound that generates keto-enol tautomerism can be preferably used. As a compound that generates keto-enol tautomerism, various β-dicarbonyl compounds can be used. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) or acetoacetate esters (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably used. Compounds that generate keto-enol tautomerism can be used individually or in combination of two or more types. The amount of the compound that generates keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight, 0.5 to 10 parts by weight, or 100 parts by weight of the base polymer. It may be more than 5 parts by weight and less than 5 parts by weight.

(Tackifier)

The adhesive disclosed herein may contain a tackifier. As a tackifier, rosin-based tackifying resin, terpene-based tackifying resin, phenol-based tackifying resin, hydrocarbon-based tackifying resin, ketone-based tackifying resin, polyamide-based tackifying resin, epoxy-based tackifying resin, and elastomer-based tackifier. Known tackifying resins such as tackifying resin can be used. These can be used individually or in combination of two or more types. The amount of tackifying resin used is not particularly limited and can be set to achieve appropriate adhesive performance depending on the purpose or use. In some embodiments, from the viewpoint of refractive index and transparency, the amount of tackifier used per 100 parts by weight of the base polymer is appropriately 30 parts by weight or less, preferably 10 parts by weight or less, and 5 parts by weight or less. It is more preferable to set it to 10 or less. The technology disclosed herein can be preferably implemented without using a tackifier.

(Leveling system)

In some embodiments, the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer is provided for the purpose of improving the appearance of the pressure-sensitive adhesive layer formed from the composition (for example, improving uniformity of thickness) or improving the coatability of the pressure-sensitive adhesive composition. , a leveling agent may be contained as needed. Non-limiting examples of the leveling agent include an acrylic leveling agent, a fluorine-based leveling agent, and a silicone-based leveling agent. The leveling agent can be used by a commercial method, for example by selecting an appropriate leveling agent from commercially available leveling agents.

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

The monomer S1 is not particularly limited, and any monomer containing a polyorganosiloxane skeleton can be used. As monomer S1, one having a structure having a polymerizable reactive group at one end can be preferably used. Among them, monomer S1, which has a structure that has a polymerizable reactive group at one end and no functional group that causes a crosslinking reaction with the acrylic polymer at the other end, can be preferably employed. Commercially available products include, for example, single-end reactive silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. (e.g., product numbers X-22-174ASX, X-22-2426, X-22-2475, KF-2012, etc.). there is. Monomer S1 can be used individually or in combination of two or more types.

The functional group equivalent of monomer S1 may be, for example, about 100 g/mol to 30000 g/mol. In some preferred embodiments, the functional group equivalent weight is, for example, 500 g/mol or more, may be 800 g/mol or more, may be 1,500 g/mol or more, or may be 2,000 g/mol or more. In addition, the functional group equivalent may be, for example, 20000 g/mol or less, 10000 g/mol or less, 7000 g/mol or less, or 5500 g/mol or less. If the functional group equivalent of monomer S1 is within the above range, a good leveling effect is likely to be exhibited.

In addition, when using two or more types of 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 type of monomer and the weight fraction of the monomer.

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

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

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

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

The content of the (meth)acrylic acid alkyl ester and the (meth)acrylic acid ester having an alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10% by weight or more and 95% by weight or less, or 20% by weight or more and 95% by weight. It may be less than or equal to 30% by weight and less than 90% by weight, or more than 40% by weight and less than 90% by weight, or more than 50% by weight and less than 85% by weight.

As other examples of monomers that can be included in monomer raw material B together with monomer S1, monomers that can be used in acrylic polymers include the carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, and cyano group-containing monomers that can be used in acrylic polymers. Monomers, isocyanate group-containing monomers, amide group-containing monomers, monomers having nitrogen atom-containing rings, (meth)acrylic acid aminoalkyls, vinyl esters, vinyl ethers, olefins, (meth)acrylic acid esters having an aromatic hydrocarbon group, halogens. Atom-containing (meth)acrylate, etc. can be mentioned.

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

The polymer (B) can be produced, for example, by polymerizing the above-mentioned monomers by known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization.

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

The amount of polymer (B) used per 100 parts by weight of the base polymer (e.g., acrylic polymer) can be, for example, 0.001 part by weight or more. From the viewpoint of obtaining a higher use effect, it may be 0.01 part by weight or more. It may be 0.03 parts by weight or more. In addition, the amount of the polymer (B) used may be, for example, 3 parts by weight or less, and from the viewpoint of reducing the influence on the refractive index, it is appropriate to set it to 1 part by weight or less, and may be 0.5 parts by weight or less, or 0.1 part by weight. The following may be acceptable. The technology disclosed herein can be practiced in an aspect in which the pressure-sensitive adhesive composition does not substantially contain polymer (B).

(High refractive index particles)

The adhesive disclosed herein may contain high refractive index particles as an optional component. Here, high refractive index particles mean particles that can increase the refractive index of the adhesive by including them in the adhesive. Hereinafter, high refractive index particles may be expressed as “particle P _HRI ”. HRI stands for high refractive index.

As the particle P _HRI , for example, one or two or more types of particles made of a material having a refractive index of 1.60 or more, preferably 1.70 or more (may be 1.80 or more, may be 1.90 or more, and may be 2.00 or more) may be used. You can. The upper limit of the refractive index of the material constituting the particle P _HRI is not particularly limited, and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, 2.20 or less, and 2.00 or less. The refractive index of the material constituting the particle P _HRI is determined using a commercially available spectroscopic ellipsometer for a monolayer film of the material (a film thickness that allows refractive index measurement) at a measurement wavelength of 589 nm and a measurement temperature of 25°C. It is a refractive index measured under certain conditions. As a spectroscopic ellipsometer, for example, product name "EC-400" (manufactured by JA.Woolam) or its equivalent is used.

The type of particle P _HRI is not particularly limited, and one or two or more types of materials that can improve the refractive index of the adhesive can be selected and used among metal particles, metal compound particles, organic particles, and organic-inorganic composite particles. You can. As the particles P _HRI , among inorganic oxides (for example, metal oxides), those that can improve the refractive index of the adhesive sheet can be preferably used. Suitable examples of materials constituting particle P _HRI include titania (titanium oxide, TiO ₂ ), zirconia (zirconium oxide, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide (Nb _{2 )} . O ₅ , etc.) and inorganic oxides (specifically, metal oxides) can be mentioned. Particles made of these inorganic oxides (for example, metal oxides) can be used individually or in combination of two or more types. Among these, particles made of titania or zirconia are preferable, and particles made of zirconia are particularly preferable. Additionally, as metal particles, for example, iron-based, zinc-based, tungsten-based, or platinum-based materials may have a high refractive index. As organic particles, the refractive index of particles made of resin such as styrene resin, phenol resin, polyester resin, and polycarbonate resin is relatively high. Examples of organic-inorganic composite particles include composites of the above-mentioned inorganic materials and organic materials, and inorganic particles coated with organic materials such as resin. As the particles P _HRI , from the viewpoint of compatibility with the adhesive component, the organic or inorganic particles described above may be surface-treated with a surface treatment agent.

The average particle diameter of the particles P _HRI is not particularly limited, and particles of an appropriate size that can realize the desired refractive index improvement by including them in the adhesive can be used. The average particle diameter of the particles P _HRI can be, for example, approximately 1 nm or more, and approximately 5 nm or more is appropriate. From the viewpoint of improving the refractive index, handling, etc., the average particle diameter of the particles P _HRI is preferably approximately 10 nm or more, and may be approximately 20 nm or more, or approximately 30 nm or more. In addition, from the viewpoint of maintaining adhesive properties, etc., the upper limit of the average particle diameter is suitably, for example, approximately 300 nm or less, and from the viewpoint of improving the refractive index, preferably approximately 100 nm or less, more preferably approximately 70 nm or less. , more preferably approximately 50 nm or less, and may be approximately 35 nm or less (for example, approximately 25 nm or less).

In addition, the average particle diameter of the particles P _HRI refers to the volume average particle diameter, and specifically, the integration in the particle size distribution measured for the particle P _HRI dispersion using a particle size distribution measuring device based on the laser scattering/diffraction method. It refers to the particle diameter at 50% of the value (50% volume average particle diameter; hereinafter, sometimes abbreviated as D ₅₀ ). As a measuring device, for example, the product name "Microtrack MT3000II" manufactured by Microtrack Bell or its equivalent product can be used.

The content of particles P _HRI in the adhesive is not particularly limited. The content of the particles P _HRI may vary depending on the target refractive index. For example, the content of the particles P _HRI can be appropriately set to have a refractive index of a predetermined or higher level, taking into account required adhesive properties, etc. In some embodiments, the content of particles P _HRI in the adhesive may be, for example, approximately 75% by weight or less, and may be approximately 50% by weight or less from the viewpoint of adhesive properties and transparency. It may be approximately 30% by weight or less. The lower limit of the content of particle P _HRI is not particularly limited, and may be, for example, more than 0% by weight, 1% by weight or more, or 5% by weight or more. In several other embodiments, the content of particles P _HRI in the adhesive may be, for example, less than 10% by weight, less than 1% by weight, or less than 0.1% by weight. The technology disclosed herein can be practiced in an embodiment in which the adhesive does not substantially contain particles P _HRI .

The content of particles P _HRI in the adhesive can also be specified by the relative relationship with the amount of base polymer (for example, acrylic polymer) contained in the adhesive. The content of particle P _HRI can be, for example, approximately 100 parts by weight or less per 100 parts by weight of the base polymer, and may be approximately 60 parts by weight or less from the viewpoint of adhesive properties and transparency, or approximately 40 parts by weight or less. do. The lower limit of the content of particle P _HRI is not particularly limited, and may be, for example, more than 0 parts by weight, more than 1 part by weight, or more than 5 parts by weight, based on 100 parts by weight of the base polymer. In some embodiments, the content of particle P _HRI may be, for example, less than 30 parts by weight, less than 10 parts by weight, less than 1 part by weight, or less than 0.1 part by weight, based on 100 parts by weight of the base polymer. .

(Other additives)

In the technology disclosed herein, the adhesive composition used to form the adhesive includes softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, anti-aging agents, and ultraviolet rays, to the extent that the effect of the present invention is not significantly impaired. Known additives that can be used in the adhesive composition, such as absorbents, antioxidants, light stabilizers, and preservatives, may be included as needed. Regarding these various additives, conventionally known ones can be used by conventional methods, and since they do not particularly characterize the present invention, detailed descriptions are omitted.

(Formation of adhesive (layer))

The adhesive disclosed herein can be formed using an adhesive composition. The form of the adhesive composition used is not particularly limited, and for example, a solvent-based adhesive composition containing an adhesive-forming component in an organic solvent, prepared to form an adhesive by curing by active energy rays such as ultraviolet rays or radiation. It can be in various forms, such as an active energy ray-curable adhesive composition, a water-dispersible adhesive composition in which the adhesive-forming component is dispersed in water, and a hot melt-type adhesive composition that is applied in a heated and molten state and forms an adhesive when cooled to around room temperature. . The adhesive is an adhesive obtained by curing an adhesive composition in the form of a solvent type, active energy ray curable type, water dispersion type, or hot melt type by drying, crosslinking, polymerization, cooling, etc., that is, it may be a cured product of the adhesive composition. Only one type of curing method (for example, drying, crosslinking, polymerization, cooling, etc.) of the adhesive composition may be applied, or two or more types may be applied simultaneously or in multiple steps. In a solvent-based adhesive composition, the adhesive can typically be formed by drying (preferably, further crosslinking) the composition. In an active energy ray-curable adhesive composition, the adhesive is typically formed by irradiating an active energy ray to advance a polymerization reaction and/or a crosslinking reaction. When it is necessary to dry with an active energy ray-curable adhesive composition, an active energy ray may be irradiated after drying. Although not particularly limited, the adhesive disclosed herein may be preferably formed using a solvent-based adhesive composition. In an aspect provided with a solvent-based adhesive layer formed of a solvent-based adhesive composition, coexistence of a high refractive index and a low elastic modulus can be preferably achieved.

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

<Adhesive sheet>

By this specification, an adhesive sheet having an adhesive layer is provided. The adhesive constituting the adhesive layer is as described above, and may be an adhesive formed from the adhesive composition described above (for example, a cured product of the adhesive composition).

The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet provided with a base material having the pressure-sensitive adhesive layer on one or both sides of a non-peelable base material (support base material), and the pressure-sensitive adhesive layer may be an adhesive sheet of an inorganic material, such as a form in which the pressure-sensitive adhesive layer is held by a release liner. A sheet (i.e., an adhesive sheet without a non-removable base material, typically consisting of an adhesive layer) may be used. The concept of adhesive sheet referred to herein may include what is referred to as adhesive tape, adhesive label, adhesive film, etc. The adhesive sheet disclosed here may be in roll shape or in sheet form. Alternatively, it may be an adhesive sheet processed into more diverse shapes.

A structural example of a double-sided adhesive type inorganic adhesive sheet (baseless double-sided adhesive sheet) is shown in Figs. 1 and 2. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 has a structure in which both surfaces 21A and 21B of an inorganic pressure-sensitive adhesive layer 21 are protected by release liners 31 and 32, respectively, with at least the pressure-sensitive adhesive layer side being a release surface. has The adhesive sheet 2 shown in FIG. 2 has a configuration in which one surface (adhesive surface) 21A of the inorganic adhesive layer 21 is protected by a release liner 31 on both sides of which are release surfaces. When this is wound, the other surface (adhesive surface) 21B of the adhesive layer 21 comes into contact with the back surface of the release liner 31, so that the other surface 21B is also protected by the release liner 31. It can be configured. The technology disclosed herein is preferably implemented in the form of an inorganic adhesive sheet made of an adhesive layer from the viewpoint of flexibility to follow an adherend that is repeatedly bent. The above-mentioned inorganic adhesive sheet is preferable, for example, from the viewpoint of reducing the thickness of the adhesive sheet and from the viewpoint of increasing the transparency of the adhesive sheet.

The adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIG. 3. The adhesive sheet 3 shown in FIG. 3 includes a support substrate 10, a first adhesive layer 21 supported on the first surface 10A and the second surface 10B of the support substrate 10, respectively, and A second adhesive layer (22) is provided. The first surface 10A and the second surface 10B are both non-peelable surfaces (non-peel surfaces). The adhesive sheet 3 attaches the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 to the adherend, respectively. It is used. That is, the adhesive sheet 3 is composed of a double-sided adhesive sheet (double-sided adhesive adhesive sheet). The adhesive sheet 3 before use has release liners 31 and 32 in which the first adhesive surface 21A and the second adhesive surface 22A are peelable surfaces (release surfaces) at least on the adhesive surface side. Each has a protected configuration. Alternatively, the release liner 32 may be omitted, and a release liner 31 having both sides as release surfaces may be used, and the adhesive sheet 3 may be wound to form a second adhesive surface 22A of the release liner 31. By contacting the back surface, the second adhesive surface 22A may also be protected by the release liner 31.

The technology disclosed herein is preferably implemented in the form of a double-sided adhesive sheet provided with the above-described inorganic material or base material for fixing or joining members (for example, optical members). Alternatively, although not specifically shown, the adhesive sheet disclosed herein may be in the form of a single-sided adhesive sheet provided with a base material having an adhesive layer on only one side of a non-removable base material (support base material). As an example of the form of the single-sided pressure-sensitive adhesive sheet, a form without either the first pressure-sensitive adhesive layer 21 or the second pressure-sensitive adhesive layer 22 in the structure shown in FIG. 3 can be given.

(Adhesive layer)

The thickness of the adhesive layer constituting the adhesive sheet is not particularly limited and can be, for example, 3 μm or more. In some embodiments, the thickness of the adhesive layer is suitably, for example, 5 μm or more, may be 10 μm or more, may be 15 μm or more, may be 20 μm or more, may be 30 μm or more, or may be 50 μm or more. It may be 70 μm or more or 85 μm or more. As the thickness of the adhesive layer increases, the adhesive strength tends to increase. In addition, in some embodiments, the thickness of the adhesive layer may be, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. In some preferred embodiments, the thickness of the adhesive layer is 100 μm or less, more preferably 75 μm or less, further preferably 70 μm or less, may be 50 μm or less, and may be 30 μm or less. The fact that the thickness of the adhesive layer is not too large can be advantageous from the viewpoint of reducing the thickness of the adhesive sheet, etc. Additionally, a thin adhesive layer tends to have excellent followability to the adherend. The technology disclosed herein is preferably carried out in such a way that the thickness of the adhesive layer ranges from 3 ㎛ to 200 ㎛ (more preferably 5 ㎛ to 100 ㎛, more preferably 5 ㎛ to 75 ㎛). It can be. Additionally, in the case of a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on the first and second sides of the substrate, the thickness of the pressure-sensitive adhesive layer described above can be applied to at least the thickness of the first pressure-sensitive adhesive layer. The thickness of the second adhesive layer may also be selected within the same range. Additionally, in the case of an inorganic adhesive sheet, the thickness of the adhesive sheet matches the thickness of the adhesive layer.

In some embodiments, the product of the storage modulus G'(0°C)[Pa] of the adhesive at 0°C and the thickness T of the adhesive layer [μm] (G'(0°C)×T) is, for example, It is appropriate to be within the range of 5.0×10 ⁴ to 7.5×10 ⁷ , and preferably within the range of 5.0×10 ⁴ to 5.0×10 ⁷ . In a thin adhesive layer, even if the elastic modulus is relatively high, it is likely to have good flexibility by having the product (G'(0°C)×T) in the above range. In addition, by limiting the product (G' (0°C) It's easy to lose. In some preferred embodiments, the product (G'(0°C)×T) may be 1.0×10 ⁵ or more, 2.0×10 ⁵ or more, or 8.0×10 ⁵ or more. Additionally, the product (G'(0°C)×T) may be 2.0×10 ⁷ or less, 1.0×10 ⁷ or less, or 6.0×10 ⁶ or less.

(Haze value)

In some embodiments, the haze value of the adhesive layer constituting the adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, and still more preferably 1.0% or less. , may be 0.9% or less, may be 0.8% or less, may be 0.5% or less, and may be 0.3% or less. The pressure-sensitive adhesive sheet having such a highly transparent pressure-sensitive adhesive layer can be used for applications requiring high light transparency (for example, optical applications), with or without a base material, and for good adhesion to adherends through the pressure-sensitive adhesive sheet. It can be preferably applied to applications requiring recognizable performance. The lower limit of the haze value of the adhesive layer is not particularly limited, and from the viewpoint of improving transparency, a smaller haze value is more preferable. On the other hand, in some embodiments, taking the refractive index and adhesive properties into consideration, the haze value may be, for example, 0.05% or more, or 0.10% or more. These haze values for the adhesive layer are preferably applied to the haze value of the adhesive sheet when the technology disclosed herein is implemented in the form of an inorganic adhesive sheet (typically, an adhesive sheet made of an adhesive layer). You can.

Here, “haze value” refers to the ratio of diffuse transmitted light to the total transmitted light when visible light is irradiated to the measurement object. Also called cloudiness. The haze value can be expressed by the following equation.

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

In some embodiments, the haze value of the adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, and even 0.9% or less. , may be 0.8% or less, may be 0.5% or less, and may be 0.3% or less. Such highly transparent adhesive sheets can be suitably applied to applications that require high light transparency (for example, optical applications) or to applications that require the performance of good visibility of the adherend through the adhesive sheet. . The lower limit of the haze value of the adhesive sheet is not particularly limited, and from the viewpoint of improving transparency, a smaller haze value is more preferable. On the other hand, in some embodiments, taking the refractive index and adhesive properties into consideration, the haze value may be, for example, 0.05% or more, or 0.10% or more. The haze value of the adhesive sheet can be measured by a method similar to the measurement of the haze value of the adhesive layer. The above-mentioned haze value of the adhesive sheet can be obtained by the composition of the adhesive layer described above, etc., or, in the case of a structure having a substrate, by selection of the substrate species and substrate thickness.

In some embodiments, the total light transmittance of the adhesive layer is preferably 85.0% or more (for example, 88.0% or more, 90.0% or more, or more than 90.0%). The pressure-sensitive adhesive sheet having such a highly transparent pressure-sensitive adhesive layer can be used for applications requiring high light transparency (for example, optical applications), with or without a base material, and for good adhesion to adherends through the pressure-sensitive adhesive sheet. It can be preferably applied to applications requiring recognizable performance. For practical purposes, the upper limit of the total light transmittance may be approximately 98% or less, approximately 96% or less, or approximately 95% or less. In some embodiments, considering the refractive index and adhesive properties, the total light transmittance of the adhesive layer may be approximately 94% or less, approximately 93% or less, or approximately 92% or less. The total light transmittance is measured using a commercially available transmittance meter based on JIS K7136:2000. As a transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Kenkyujo or its equivalent is used. The total light transmittance can be measured according to the method described in the Examples described later. The total light transmittance of the adhesive layer can be adjusted, for example, by selecting the composition or thickness of the adhesive layer.

In some embodiments, the total light transmittance of the adhesive sheet is preferably 85.0% or more (for example, 88.0% or more, 90.0% or more, or more than 90.0%). Such highly transparent adhesive sheets can be suitably applied to applications that require high light transparency (for example, optical applications) or to applications that require the performance of good visibility of the adherend through the adhesive sheet. . For practical purposes, the upper limit of the total light transmittance may be approximately 98% or less, approximately 96% or less, or approximately 95% or less. In some embodiments, taking into account the refractive index and adhesive properties, the total light transmittance of the adhesive sheet may be approximately 94% or less, approximately 93% or less, or approximately 92% or less. The total light transmittance of the adhesive sheet can be measured by a method similar to the measurement of the total light transmittance of the adhesive layer. The total light transmittance of the adhesive sheet can be obtained by the composition of the adhesive layer described above, etc., or, in the case of a structure having a substrate, by selecting the substrate species or substrate thickness.

(Peel Strength)

The peeling strength of the adhesive sheet from the glass plate is not particularly limited. In some embodiments, the adhesive sheet may have a peeling strength from a glass plate of, for example, 0.1 N/25 mm or more, and may be 0.5 N/25 mm or more. In some preferred embodiments, the peel strength for the glass plate is 1.0 N/25 mm or more, more preferably 1.5 N/25 mm or more, even more preferably 2.0 N/25 mm or more, and 3.0 N/25 mm or more. It may be more than mm, may be more than 5.0N/25mm, and may be more than 10N/25mm. In this way, an adhesive sheet having a peeling strength from a glass plate of a predetermined value or more is suitable for, for example, joining or fixing glass members. The upper limit of the peel strength is not particularly limited, and may be, for example, 30 N/25 mm or less, 25 N/25 mm or less, or 20 N/25 mm or less.

Here, the peel strength is determined by pressing an alkali glass plate as an adherend, leaving it in an environment of 23° C. and 50% RH for 30 minutes, and then measuring the peel strength under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm/min. do. In the measurement, if necessary, the adhesive sheet to be measured can be reinforced by attaching an appropriate backing material (for example, a polyethylene terephthalate (PET) film with a thickness of about 25 μm to about 50 μm). More specifically, peel strength can be measured according to the method described in the Examples described later.

(Thickness of adhesive sheet)

The thickness of the adhesive sheet disclosed herein (baseless adhesive sheet or adhesive sheet with a base material) may be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, or 120 μm or less. It may be 75㎛ or less, and may be 50㎛ or less. Additionally, from the viewpoint of handling, etc., the thickness of the adhesive sheet may be, for example, 5 μm or more, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.

In addition, the thickness of the adhesive sheet refers to the thickness of the portion attached to the adherend. For example, in the adhesive sheet 3 of the configuration shown in FIG. 3, the thickness refers to the thickness from the first adhesive surface 21A to the second adhesive surface 22A, and does not include the thickness of the release liners 31 and 32. No.

<Supporting description>

The pressure-sensitive adhesive sheet according to some embodiments may be in the form of a pressure-sensitive adhesive sheet provided with a base material including an adhesive layer on one or both sides of the support base material. The material of the support base material is not particularly limited and can be appropriately selected depending on the purpose of use or usage mode of the adhesive sheet. Non-limiting examples of substrates that can be used include polyolefin films mainly containing polyolefins such as polypropylene (PP) and ethylene-propylene copolymer, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene film. Plastic films such as polyester films containing polyester such as phthalate (PEN) as a main ingredient, and polyvinyl chloride films containing polyvinyl chloride as a main ingredient; Foam sheets made of foam such as polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; Woven fabrics and non-woven fabrics made by spinning alone or in a blend of various fibrous materials (which may be natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate); Papers such as washi paper, fine paper, kraft paper, and crepe paper; Metal foil such as aluminum foil and copper foil; etc. can be mentioned. The base material may be a combination of these. Examples of such composite substrates include, for example, a substrate having a structure in which metal foil and the above plastic film are laminated, a plastic substrate reinforced with inorganic fibers such as glass cloth, etc.

In some embodiments, various film substrates can be preferably used. The film substrate may be a porous substrate such as a foam film or a non-woven fabric sheet, may be a non-porous substrate, or may be a substrate having a structure in which a porous layer and a non-porous layer are laminated. In some embodiments, the film substrate may preferably include a resin film capable of independently maintaining its shape (self-supporting or non-dependent) as a base film. Here, “resin film” means a resin film that has a non-porous structure and typically contains substantially no air bubbles (voidless). Therefore, the resin film is a concept that is distinct from foam films or nonwoven fabrics. As the resin film, one that can independently maintain its shape (self-supporting or non-dependent) can be preferably used. The resin film may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

Examples of the resin material constituting the resin film include polyester; polyolefin; Polycycloolefins derived from monomers having an aliphatic ring structure such as a norbornene structure; Polyamides (PA) such as nylon 6, nylon 66, and partially aromatic polyamide; Polyimide (PI) such as transparent polyimide (CPI); polyamideimide (PAI); polyetheretherketone (PEEK); polyethersulfone (PES); polyphenylene sulfide (PPS); polycarbonate (PC); polyurethane (PU); ethylene-vinyl acetate copolymer (EVA); Fluororesins such as polytetrafluoroethylene (PTFE); Acrylic resin; Cellulose-based polymers such as triacetylcellulose (TAC); polyarylate; polystyrene; polyvinyl chloride; Resins such as polyvinylidene chloride can be used.

The resin film may be formed using a resin material that contains one type of such resin alone, or may be formed using a resin material that is a blend of two or more types. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched). For example, PET film, PBT film, PEN film, non-oriented polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, PP/ PE blend film, cycloolefin polymer (COP) film, CPI film, TAC film, etc. can be preferably used. Examples of preferable resin films from the viewpoint of strength and dimensional stability include PET film, PEN film, PPS film, and PEEK film. PET film and PPS film are particularly preferable from the viewpoint of ease of availability, etc., and among these, PET film is preferable.

The resin film needs to contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and anti-blocking agents, to the extent that the effects of the present invention are not significantly impaired. It can be mixed accordingly. The amount of additives is not particularly limited and can be set appropriately depending on the purpose of the adhesive sheet.

The manufacturing method of the resin film is not particularly limited. For example, conventionally known general resin film molding methods such as extrusion molding, inflation molding, T die cast molding, and calendar roll molding can be appropriately employed.

The substrate may be substantially composed of such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an optical property adjustment layer (e.g., a colored layer, an anti-reflection layer), a surface treatment layer such as a printing layer, a laminate layer, an antistatic layer, an undercoating layer, and a peeling layer for giving the substrate a desired appearance. I can hear it.

In some embodiments, a substrate having light transparency (hereinafter also referred to as a light transmission substrate) can be preferably used as the support substrate. This makes it possible to construct a pressure-sensitive adhesive sheet provided with a light-transmitting substrate. The total light transmittance of the light-transmitting substrate may be, for example, more than 50% or 70% or more. In some preferred embodiments, the total light transmittance of the support substrate is 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). The total light transmittance is measured using a commercially available transmittance meter based on JIS K 7136:2000. As a transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Kenkyujo or its equivalent is used. A suitable example of the light-transmitting substrate includes a resin film having light transparency. The light-transmitting substrate may be an optical film.

The thickness of the base material is not particularly limited and can be selected depending on the purpose of use or usage mode of the adhesive sheet. The thickness of the substrate may be, for example, 500 μm or less, preferably 300 μm or less from the viewpoint of handling and processability of the adhesive sheet, 150 μm or less, 100 μm or less, 50 μm or less, and 25 μm or less. It may be ㎛ or less, and may be 10 ㎛ or less. As the thickness of the substrate decreases, followability to the surface shape of the adherend tends to improve. Additionally, from the viewpoint of handling, processability, etc., the thickness of the substrate may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

The surface of the substrate on which the adhesive layer is laminated is subjected to conventional treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and formation of an undercoat layer by applying an undercoat (primer), as needed. Known surface treatment may be performed. Such surface treatment may be a treatment to improve the anchoring properties of the adhesive layer to the substrate. The composition of the primer used to form the undercoat layer is not particularly limited and can be appropriately selected from known ones. The thickness of the undercoating layer is not particularly limited, but is usually about 0.01 μm to 1 μm, and is preferably about 0.1 μm to 1 μm. Other treatments that can be performed on the substrate as needed include antistatic layer formation treatment, colored layer formation treatment, and printing treatment. These treatments can be applied singly or in combination.

<Adhesive sheet with release liner>

The adhesive sheet disclosed herein may take the form of an adhesive product in which the surface (adhesive surface) of the adhesive layer is brought into contact with the release surface of the release liner. Accordingly, this specification provides an adhesive sheet (adhesive product) comprising any of the adhesive sheets disclosed herein and a release liner including a release liner having a release surface that abuts the adhesive surface of the adhesive sheet.

The release liner is not particularly limited, and includes, for example, a release liner having a release layer on the surface of a liner base material such as a resin film or paper (possibly paper laminated with a resin such as polyethylene), or a fluorine-based polymer (polytetra). A release liner made of a resin film formed of a low-adhesion material such as fluoroethylene or polyolefin resin (polyethylene, polypropylene, etc.) can be used. Since the surface smoothness is excellent, a release liner having a release layer on the surface of a resin film as the liner base material or a release liner made of a resin film formed of a low-adhesive material can be preferably employed. The resin film is not particularly limited as long as it is a film that can protect the adhesive layer, and examples include polyethylene (PE) film, polypropylene (PP) film, polybutene film, polybutadiene film, polymethylpentene film, and polychloride film. Examples include vinyl films, vinyl chloride copolymer films, polyester films (PET films, PBT films, etc.), polyurethane films, and ethylene-vinyl acetate copolymer films. For forming the peeling layer, known peeling agents such as silicone-based peeling agents, long-chain alkyl-based peeling agents, olefin-based peeling agents, fluorine-based peeling agents, fatty acid amide-based peeling agents, molybdenum sulfide, and silica powder can be used. there is.

<Use>

The uses of the adhesive sheet disclosed here are not limited and can be used for various purposes. Since the adhesive sheet disclosed herein is provided with an adhesive that combines high refractive index and flexibility, it can be used for various applications requiring high refractive index and flexibility by taking advantage of its characteristics. For example, in electronic devices such as portable electronic devices, display devices (image display devices) such as liquid crystal display devices, organic EL (electroluminescence) display devices, PDP (plasma display panels), electronic paper, and touch display devices. It is suitable as an adhesive sheet for devices (optical devices) such as input devices such as panels, especially foldable displays and rollable displays. For example, in foldable displays or rollable displays, it is preferably used as a means of bonding, fixing, or protecting members with a high refractive index. The adhesive sheet disclosed herein has a high refractive index and can have flexibility to withstand repeated bending operations, so that when attached to a foldable display or rollable display, it can be used as an adherend that is repeatedly bent (foldable display) etc.) can be followed well. Examples of objects to be attached in this form of use include glass members such as window glass and cover glass used in foldable displays and rollable displays. In addition, the adhesive sheet disclosed herein easily follows and adheres to a curved surface, such as a three-dimensional shape of a portable electronic device, and is therefore suitable for use in electronic devices having such a curved shape. Additionally, in some preferred embodiments, the adhesive may have excellent heat resistance in addition to having a high refractive index and flexibility. Since the above-mentioned portable electronic devices are sometimes used in high-temperature environments, and their internal space may become heated due to heat generation from electronic components, the advantage of using the above-mentioned heat-resistant adhesive sheet is great.

Examples of the above-mentioned portable electronic devices include, for example, mobile phones, smartphones, tablet-type personal computers, notebook-type personal computers, and various wearable devices (e.g., wrist wear types that are worn on the wrist, such as a wrist watch, with a clip or strap, etc.) Modular type that is mounted on part of the body, eyewear type including glasses type (monocular or binocular type, including head-mounted type), clothing type that is installed in the form of an accessory, for example, on a shirt, socks, or hat, etc., earphones and ear wear type that is installed on the ear, etc.), digital camera, digital video camera, audio equipment (portable music player, IC recorder, etc.), calculator (electronic calculator, etc.), portable game device, electronic dictionary, electronic notebook, electronic book, vehicle Includes onboard information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. In addition, in this specification, “carrying” means that it is not enough to simply be able to carry, but to have a level of portability that allows an individual (a standard adult) to carry with relative ease.

The material (adherent material) to which the adhesive sheet disclosed herein is attached is not particularly limited, but includes, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc., or Metal materials such as alloys containing two or more of these, for example, polyimide resin, acrylic resin, polyethernitrile resin, polyether sulfone resin, polyester resin (PET resin, polyethylene naphthalate type resin, etc.), polyvinyl chloride type resin, polyphenylene sulfide type resin, polyether ether ketone type resin, polyamide type resin (so-called aramid resin, etc.), polyarylate type resin, polycarbonate type resin, diacetyl Cellulose-based polymers such as cellulose and triacetylcellulose, various resin materials (typically plastic materials) such as vinyl butyral polymers and liquid crystal polymers, and inorganic materials such as alumina, zirconia, alkali glass, alkali-free glass, quartz glass, and carbon. etc. can be mentioned. The adhesive sheet disclosed herein can be used by attaching it to a member (for example, an optical member) made of the above material.

The member or material to which the adhesive sheet disclosed herein is attached (in the case of a double-sided adhesive sheet, at least one adherend) may be made of a material with a higher refractive index than a general adhesive (for example, an acrylic adhesive). The refractive index of the adherend material is, for example, 1.50 or more. Among them, there are adherend materials with a refractive index of 1.55 or more or 1.58 or more, and there are also those with a refractive index of 1.62 or more (for example, about 1.66). Such a high refractive index adherend material is typically a resin material. More specifically, it may be polyester-based resin such as PET, polyimide-based resin, aramid resin, polyphenylene sulfide-based resin, polycarbonate-based resin, etc. For such materials, the effect of using the pressure-sensitive adhesive sheet disclosed herein (suppression of reflection of light due to a difference in refractive index) can be advantageously exhibited. The upper limit of the refractive index of the adherend material is, for example, 1.80 or less, and may be 1.70 or less. The pressure-sensitive adhesive sheet disclosed herein can be preferably used in the form of sticking it to an adherend (for example, member) of high refractive index as described above. A suitable example of such an adherend includes a resin film with a refractive index of 1.50 to 1.80 (preferably 1.55 to 1.75, for example, 1.60 to 1.70). The refractive index can be measured in the same way as the refractive index of the adhesive.

The member or material to which the adhesive sheet is attached (in the case of a double-sided adhesive sheet, at least one adherend) may have light transparency. With such an adherend, it is easy to obtain the advantage of the effect (suppression of light reflection at the interface between the adherend and the adhesive sheet) by the technology disclosed herein. The total light transmittance of the adherend may be, for example, greater than 50%, and preferably greater than 70%. In some preferred embodiments, the total light transmittance of the adherend is 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). The adhesive sheet disclosed herein can be suitably used in the form of sticking it to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The total light transmittance is measured using a commercially available transmittance meter based on JIS K 7136:2000. As a transmittance meter, the product name "HAZEMETER HM-150" manufactured by Murakami Shikisai Kijutsu Kenkyujo or its equivalent is used.

In some preferred embodiments, the adherend (for example, member) to which the adhesive sheet is attached may have the above-mentioned refractive index and may have the above-mentioned total light transmittance. Specifically, the refractive index is 1.50 or more (e.g., 1.55 or more, 1.58 or more, 1.62 or more, about 1.66, etc.), and the total light transmittance is greater than 50% (e.g., 70% or more, preferably 80% or more, More preferably, it may be 90% or more, and further 95% or more). The adhesive sheet disclosed herein can be preferably used in the form of sticking to an adherend, for example, a member. In the aspect where it is attached to such a member, the effect achieved by the technique disclosed herein is particularly preferably exhibited.

An example of a preferable use is optical use. More specifically, the adhesive sheet disclosed herein is an optical adhesive sheet used, for example, for bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the optical members. can be preferably used.

The optical member refers to a member having optical properties (e.g., polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, light rotation, visibility, etc.). The optical member is not particularly limited as long as it has optical properties, but examples include members constituting devices (optical devices) such as display devices (image display devices) and input devices, or members used in these devices. For example, polarizer, wave plate, retardation plate, optical compensation film, brightness enhancement film, light guide plate, reflective film, anti-reflection film, hard coat (HC) film, shock absorption film, antifouling film, photochromic film, Illuminated films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and even members on which they are laminated (sometimes these are collectively referred to as “functional films”) ), etc. In addition, the above-mentioned “plate” and “film” include forms such as plate, film, and sheet, respectively. For example, “polarizing film” includes “polarizing plate” and “polarizing sheet,” etc. , “Light guide plate” shall include “light guide film”, “light guide sheet”, etc. Additionally, the “polarizing plate” shall include a circularly polarizing plate.

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

The optical member is not particularly limited, but includes, for example, members made of glass, acrylic resin, polycarbonate, PET, metal thin film, etc. (e.g., sheet-shaped, film-shaped, plate-shaped members). there is. In addition, the “optical member” in this specification shall also include members (design film, decorative film, surface protection film, etc.) that play a role in decoration or protection while maintaining visibility of the display device or input device.

The technology disclosed herein, for example, uses optical films such as films or fluorescent films having one or two or more functions such as light transmission, reflection, diffusion, wave guidance, light collection, and diffraction to other optical members (which may be other optical films). It can be preferably used to join). Among them, in the case of bonding optical films that have at least one function of light guiding, condensing, and diffraction, it is preferable that the entire bulk of the bonding layer has a high refractive index, and the technology disclosed herein can be preferably applied.

The adhesive disclosed herein can be preferably used for bonding optical films such as light guide films, diffusion films, fluorescent films, color toning films, prism sheets, lenticular films, and micro lens array films. In these applications, from the viewpoint of the trend towards miniaturization and improved performance of optical members, reduction in thickness and improvement in light extraction efficiency are required. As an adhesive that can meet these requests, the adhesive disclosed herein can be preferably used. More specifically, for example, in bonding a light guide film or a diffusion film, adjusting the refractive index of the adhesive layer as a bonding layer (for example, increasing the refractive index) can contribute to thinning. In the bonding of fluorescent films, light extraction efficiency (which can also be understood as luminous efficiency) can be improved by appropriately adjusting the refractive index difference between the fluorescent emitter and the adhesive. In the bonding of a coloring film, the scattering component can be reduced by appropriately adjusting the refractive index of the adhesive so that the difference in refractive index with the coloring pigment is small, thereby contributing to the improvement of light transmittance. In bonding prism sheets, lenticular films, micro lens array films, etc., diffraction of light can be controlled by appropriately adjusting the refractive index of the adhesive, contributing to improvement of luminance and/or viewing angle.

The adhesive sheet disclosed herein is preferably used in the form of being affixed to a high refractive index adherend (which may be a high refractive index layer or member, etc.), and can suppress reflection at the interface with the adherend. As described above, the adhesive sheet used in this manner preferably has a small difference in refractive index with the adherend and has high adhesion at the interface with the adherend. Additionally, from the viewpoint of enhancing the uniformity of appearance, it is desirable for the adhesive layer to have high thickness uniformity, for example, it is desirable for the adhesive surface to have high surface smoothness. When the thickness of the high refractive index adherend is relatively small (for example, 5 ㎛ or less, 4 ㎛ or less, or 2 ㎛ or less), from the viewpoint of suppressing coloring or color unevenness due to interference of reflected light, reflection at the interface Suppression is particularly meaningful. As an example of such a usage mode, in a polarizer with a retardation layer comprising a polarizer, a first retardation layer, and a second retardation layer in this order, the polarizer and the first retardation layer are joined and/or the first retardation layer is An aspect used for bonding the second phase difference layer may be mentioned.

In addition, since the adhesive sheet disclosed herein is suitable for increasing the refractive index, it can be preferably used in the form of being attached to a light-emitting layer such as an optical semiconductor (for example, a high-refractive light-emitting layer mainly composed of an inorganic material). By reducing the difference in refractive index between the light-emitting layer and the adhesive layer, reflection at their interface can be suppressed and light extraction efficiency can be improved. The pressure-sensitive adhesive sheet used in this aspect is preferably provided with a pressure-sensitive adhesive layer with a high refractive index. Additionally, from the viewpoint of improving brightness, it is preferable that the pressure-sensitive adhesive sheet is low-colored. This can also be advantageous from the viewpoint of suppressing unintentional coloring caused by the adhesive sheet.

In addition, in this specification, a self-luminous device refers to a light-emitting device whose luminance can be controlled by the value of the flowing current. The self-luminous element may be composed of a single entity or an aggregate. Specific examples of self-luminous devices include, but are not limited to, light emitting diodes (LEDs) and organic ELs. In addition, in this specification, a light-emitting device refers to a device that includes such a self-luminous element as a component. Examples of the light-emitting device include, but are not limited to, a light source module device (for example, a planar light-emitting body module) used as lighting and a display device in which pixels are formed.

The adhesive disclosed herein is used as a micro lens or other lens member used as a structural member of a camera or light emitting device (for example, a micro lens constituting a micro lens array film or a lens member such as a micro lens for a camera). Preferred as a coating layer covering the lens surface, a bonding layer with a member opposing the lens surface (for example, a member having a surface shape corresponding to the lens surface), a filling layer filled between the lens surface and the member, etc. It can be used effectively. Since the adhesive disclosed herein is suitable for increasing the refractive index, even if it is a high refractive index lens (for example, a lens made of a high refractive index resin or a lens having a surface layer made of a high refractive index resin), the adhesive has a high refractive index compared to the lens. The car can be reduced. This is advantageous from the viewpoint of reducing the thickness of the lens and products equipped with the lens, and can also contribute to suppressing aberrations and improving the Abbe number. The adhesive disclosed herein can also be used as a lens resin by itself, for example, in the form of filling the recesses or voids of a suitable transparent member.

The mode of bonding optical members using the adhesive sheet disclosed herein is not particularly limited, but includes (1) the mode of bonding optical members to each other via the adhesive sheet disclosed herein, and (2) the mode of bonding optical members together using the adhesive sheet disclosed herein. The optical member may be bonded to a member other than the optical member through the adhesive sheet disclosed in, (3) the adhesive sheet disclosed herein may be in a form including an optical member, and the adhesive sheet may be bonded to the optical member or a member other than the optical member. It may be joined to a member. Additionally, in the aspect (3) above, the pressure-sensitive adhesive sheet including an optical member may be, for example, a pressure-sensitive adhesive sheet whose support is an optical member (eg, an optical film). In this way, a pressure-sensitive adhesive sheet including an optical member as a support can also be considered as a pressure-sensitive adhesive optical member (for example, a pressure-sensitive adhesive optical film). In addition, when the adhesive sheet disclosed herein is a type of adhesive sheet having a support and the functional film is used as the support, the adhesive sheet disclosed herein has an adhesive layer disclosed herein on at least one side of the functional film. It can also be understood as an “adhesive functional film” having.

From the above, according to the technology disclosed herein, a laminate including the adhesive sheet disclosed herein and a member to which the adhesive sheet is attached is provided. The member to which the adhesive sheet is attached may have the refractive index of the adherend material described above. Additionally, the difference between the refractive index of the adhesive sheet and the refractive index of the member (refractive index difference) may be the difference in refractive index between the adherend and the adhesive sheet described above. Since the members constituting the laminate are the same as those described as the members, materials, and adherends described above, overlapping explanations will not be repeated.

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

[1] An adhesive having a refractive index of 1.55 or more and a storage modulus of elasticity G' at 0°C (0°C) within the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa.

[2] The adhesive according to [1] above, wherein the glass transition temperature is within the range of -50°C to 0°C.

[3] The ratio of the storage elastic modulus G'(0°C) to the storage elastic modulus G'(80°C) at 80°C (G'(0°C)/G'(80°C)) is in the range of 1 to 1000. The adhesive according to [1] or [2] above.

[4] The ratio of the storage modulus G'(-10℃) at -10℃ to the storage modulus G'(80℃) at 80℃ (G'(-10℃)/G'(80℃)) , the adhesive according to any one of [1] to [3] above, within the range of 1 to 1000.

[5] Contains an acrylic polymer,

The adhesive according to any one of [1] to [4] above, wherein the monomer component constituting the acrylic polymer contains an aromatic ring-containing monomer (A1).

[6] The adhesive according to any one of [1] to [5] above, comprising a plasticizer, wherein the plasticizer is a liquid compound at 30°C having two or more double bond-containing rings.

[7] The adhesive according to [6], wherein the compound is a liquid compound at 20°C.

[8] The adhesive according to [6] or [7], wherein the plasticizer is contained in an amount exceeding 15 parts by weight (further 30 parts by weight) based on 100 parts by weight of the base polymer.

[9] The adhesive according to any one of [6] to [8], wherein the plasticizer has at least one ring selected from aromatic rings and hetero rings as the double bond-containing ring.

[10] The plasticizer has a first double bond-containing ring and a second double bond-containing ring, and the first double bond-containing ring and the second double bond-containing ring are connected through a linking group having 1 to 5 atoms. , the adhesive according to any one of [6] to [9] above.

[11] The adhesive according to any of [6] to [10], wherein the molecular weight of the plasticizer is in the range of 100 to 2000.

[12] The adhesive according to [5], wherein the monomer component constituting the acrylic polymer contains, in addition to the aromatic ring-containing monomer (A1), a monomer (A2) having at least one of a hydroxyl group and a carboxyl group.

[13] The adhesive according to [5] or [12], wherein in the monomer component, the content of the aromatic ring-containing monomer (A1) is 60% by weight or more.

[14] The adhesive according to any one of [5], [12], and [13] above, wherein 50% by weight or more of the aromatic ring-containing monomer (A1) is a monomer with a homopolymer glass transition temperature of 10°C or lower.

[15] The adhesive according to any one of [5], [12] to [14] above, further comprising a crosslinking agent.

[16] An adhesive sheet comprising an adhesive layer made of the adhesive according to any one of [1] to [15] above.

[17] The adhesive sheet according to [16], wherein the adhesive layer has a thickness in the range of 5 to 75 μm.

[18] The product of the storage modulus G'(0℃)[Pa] of the adhesive at 0℃ and the thickness T[㎛] of the adhesive layer (G'(0℃)×T) is 5.0×10 ⁴ to 5.0×10 The adhesive sheet according to [16] or [17] above, within the range of ⁷ .

[19] The adhesive sheet according to any one of [16] to [18] above, wherein the adhesive sheet has a total light transmittance of 85% or more.

[20] The adhesive sheet according to any one of [16] to [19] above, wherein the adhesive sheet has a haze value of 3% or less.

[21] The adhesive sheet according to any one of [16] to [20] above, wherein the adhesive sheet has a peeling strength from a glass plate of 0.1 N/25 mm or more.

Example

Hereinafter, several examples of the present invention will be described, but it is not intended to limit the present invention to these specific examples. In addition, in the following description, “part” and “%” indicating the usage amount or content are based on weight unless otherwise specified.

<Example 1>

(Preparation of acrylic polymer solution)

In a four-neck flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser, m-phenoxybenzyl acrylate (manufactured by Kyoesha Chemical Co., Ltd., brand name “Light Acrylate POB-A”) as a monomer component, refractive index: 1.566. , Tg of homopolymer: -35°C. Hereinafter referred to as "POB-A") 95 parts and 4-hydroxybutylacrylate (4HBA) 5 parts, 2,2'-azobisisobutyro as polymerization initiator. 0.2 parts of nitrile and 150 parts of ethyl acetate were added as a polymerization solvent, nitrogen gas was introduced with gentle stirring, and the polymerization reaction was performed for 6 hours while maintaining the liquid temperature in the flask at around 60°C to form a solution of acrylic polymer P1 (40%). ) was prepared. The Mw of acrylic polymer P1 was 500,000.

(Preparation of adhesive composition)

The solution (40%) of the acrylic polymer P1 was diluted to 20% with ethyl acetate, and 500 parts of this solution (100 parts of non-volatile matter) was added with the isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, brand name) as a crosslinking agent. Coronate HX", a trifunctional isocyanate compound) of 1% ethyl acetate solution (0.1 part non-volatile matter), 2 parts acetylacetone as a crosslinking retardant, and 1% ethyl acetate solution of ferric ferric ferric acid as a crosslinking catalyst. 1 part (0.01 part of non-volatile matter) was added and mixed with stirring to prepare the acrylic adhesive composition according to this example.

(Production of adhesive sheet)

The acrylic adhesive composition prepared above was applied to the silicone-treated side of polyethylene terephthalate (PET) film R1 (50㎛ thick), one side of which was silicone-treated, and heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 20㎛. was formed. Next, the silicone-treated side of PET film R2 (thickness 25 μm), on which one side was silicone-treated, was bonded to the surface of the adhesive layer. In this way, an inorganic double-sided adhesive sheet consisting of the adhesive layer was obtained. Both sides of this adhesive sheet are protected by PET films (release liners) R1 and R2.

<Example 2>

(Preparation of acrylic polymer solution)

In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, benzyl acrylate (Osaka Yuki Chemical Co., Ltd., brand name "Viscott #160") as a monomer component, refractive index: 1.519, Tg of homopolymer: 6°C. Hereinafter referred to as “BZA”) 99 parts and 1 part of 4HBA, 0.2 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 100 parts of ethyl acetate as a polymerization solvent were added, and gently stirred. While nitrogen gas was introduced and the liquid temperature in the flask was maintained at around 60°C, a polymerization reaction was performed for 6 hours to prepare a solution of acrylic polymer P2 (polymer concentration 50%). The Mw of acrylic polymer P2 was 1 million.

(Preparation of adhesive composition)

The solution of the acrylic polymer P2 (polymer concentration 50%) was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of this solution (100 parts non-volatile matter) was added with the isocyanurate form of hexamethylene diisocyanate (Toso) as a crosslinking agent. 10 parts of 1% ethyl acetate solution (0.1 part non-volatile matter) of (manufactured by, brand name “Coronate HX”, trifunctional isocyanate compound), 2 parts of acetylacetone as a crosslinking retardant, and 1% of ferric nasem as a crosslinking catalyst. 1 part of ethyl acetate solution (0.01 part of non-volatile matter) was added and mixed with stirring to prepare the acrylic adhesive composition according to this example.

(Production of adhesive sheet)

Using the obtained acrylic adhesive composition, the adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as in Example 1.

<Examples 3 to 5>

In the preparation of the acrylic adhesive composition in Example 2, POB-A (manufactured by Kyoesha Chemical Co., Ltd., brand name "Light Acrylate POB-A") was used as plasticizer A1 with respect to 100 parts of non-volatile matter contained in the solution of acrylic polymer P2. 」, m-phenoxybenzyl acrylate, refractive index: 1.566, liquid at 20°C) in Example 2, except that 30 parts (Example 3), 45 parts (Example 4), or 60 parts (Example 5) were further added. In the same manner as the preparation of the acrylic adhesive composition in the above, the acrylic adhesive composition for each example was prepared. In the same manner as the production of the adhesive sheet in Example 1, except that each of the obtained acrylic adhesive compositions was used, adhesive sheets (inorganic double-sided adhesive sheets consisting of an adhesive layer) for each example were produced.

<Example 6>

The composition of the monomer component is 99 parts of phenoxyethyl acrylate (manufactured by Osaka Yuki Chemical Co., Ltd., brand name “Viscott #192”, refractive index: 1.517, Tg of homopolymer: 2°C. Hereinafter referred to as “PEA”) and 4HBA. A solution of acrylic polymer P3 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2 except that it was changed to 1 part. The Mw of acrylic polymer P3 was 1 million.

The acrylic adhesive composition according to this example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 2, except that the solution of acrylic polymer P3 was used instead of the solution of acrylic polymer P2, and the obtained acrylic adhesive composition was used. In the same manner as 1, the adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced.

<Example 7>

In preparing the acrylic adhesive composition in Example 3, a solution of acrylic polymer P3 was used instead of a solution of acrylic polymer P2. Otherwise, the acrylic adhesive composition according to this example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 3, and using the obtained acrylic adhesive composition, in the same manner as in Example 1, an adhesive sheet (adhesive layer) according to this example was prepared. An inorganic double-sided adhesive sheet consisting of) was produced.

<Example 8>

A solution of acrylic polymer P4 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 99 parts of BZA and 1 part of acrylic acid (AA). The Mw of acrylic polymer P4 was 1 million.

The solution of the acrylic polymer P4 (polymer concentration: 50%) was diluted with ethyl acetate to a polymer concentration of 30%, and an epoxy-based crosslinking agent (Mitsubishi Gas Chemical Co., Ltd.) was added to this solution (334 parts) (non-volatile matter (100 parts)) as a crosslinking agent. 0.1 part of 1,3-bis(N,N-diglycidyl aminomethyl)cyclohexane) under the brand name "Tetrad C" was added and mixed with stirring to prepare an acrylic adhesive composition according to this example.

An adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used.

<Examples 9 to 12>

In the preparation of the acrylic adhesive composition in Example 8, 60 parts of POB-A as plasticizer A1 (Example 9) and 4,4'- as plasticizer A2 per 100 parts of non-volatile matter contained in the solution of acrylic polymer P4. 60 parts (Example 10) of oxybis[(methoxymethyl)benzene] (manufactured by Tokyo Kasei Industries, refractive index: 1.56, liquid at 20°C) and 3-phenoxybenzyl alcohol (manufactured by Tokyo Kasei Industries, Ltd., refractive index: 1.591, liquid at 20°C. Hereinafter sometimes referred to as “POB-AL”), 60 parts (Example 11), or 1-acetonaphtone (manufactured by Tokyo Kasei Kogyo Co., Ltd., refractive index: 1.63, 20°C) as plasticizer A4. The acrylic adhesive composition for each example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 8, except that 60 parts (Example 12) of liquid) was further added. In the same manner as the production of the adhesive sheet in Example 1, except that each of the obtained acrylic adhesive compositions was used, adhesive sheets (inorganic double-sided adhesive sheets consisting of an adhesive layer) for each example were produced.

<Example 13>

A solution of acrylic polymer P5 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 90 parts of BZA, 9 parts of n-butylacrylate (BA), and 1 part of AA. The Mw of acrylic polymer P5 was 1 million.

A solution of the acrylic polymer P5 (50% polymer concentration) was diluted with ethyl acetate to a polymer concentration of 30%, and 334 parts of this solution (100 parts non-volatile matter) was mixed with 60 parts of the plasticizer A3 (POB-AL) and the epoxy. 0.1 part of the system crosslinking agent was added and mixed with stirring to prepare the acrylic adhesive composition according to this example.

An adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used.

<Example 14>

In the preparation of the acrylic adhesive composition in Example 13, bisresol fluorene (manufactured by Osaka Gas Chemical Co., Ltd., 9,9-bis(4-hydride) Preparation of the acrylic adhesive composition in Example 13 was carried out similarly to the preparation of the acrylic adhesive composition in Example 13, except that 15 parts of oxy-3-methylphenyl) fluorene, refractive index: 1.68 (hereinafter sometimes referred to as “BCF”) was added as a solid content. Acrylic adhesive compositions for each example were prepared. The additive was added as a 10% ethyl acetate solution.

An adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used.

<Examples 15 to 16>

A solution of acrylic polymer P6 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 90 parts of BZA, 9 parts of 2-ethylhexyl acrylate (2EHA), and 1 part of AA. The Mw of acrylic polymer P6 was 1 million.

In preparing the acrylic adhesive composition in Examples 13 and 14, a solution of acrylic polymer P6 was used instead of a solution of acrylic polymer P5. Otherwise, in the same manner as the preparation of the acrylic adhesive composition in Examples 13 and 14, the acrylic adhesive compositions in Examples 15 and 16 were prepared, and each of the obtained acrylic adhesive compositions was used in the same manner as in Example 1. The adhesive sheets (inorganic double-sided adhesive sheets consisting of an adhesive layer) for each example were produced.

<Examples 17 to 18>

A solution of acrylic polymer P7 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 80 parts of BZA, 19 parts of BA, and 1 part of AA. Additionally, a solution of acrylic polymer P8 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 66 parts of BZA, 33 parts of BA, and 1 part of AA. The Mw of acrylic polymers P7 and P8 was 1 million.

In preparing the acrylic adhesive composition in Example 13, a solution of acrylic polymer P7 (Example 17) or P8 (Example 18) was used instead of the solution of acrylic polymer P5. Otherwise, in the same manner as the preparation of the acrylic adhesive composition in Example 13, the acrylic adhesive compositions related to Examples 17 to 18 were prepared, and each obtained acrylic adhesive composition was used to prepare the acrylic adhesive composition in the same manner as in Example 1. Each adhesive sheet (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced.

<Example 19>

A solution of acrylic polymer P9 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 85 parts of POB-A, 14 parts of BA, and 1 part of AA. The Mw of acrylic polymer P9 was 1 million.

In preparing the acrylic adhesive composition in Example 13, a solution of acrylic polymer P9 was used instead of a solution of acrylic polymer P5. Otherwise, the acrylic adhesive composition according to this example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 13, and using the obtained acrylic adhesive composition, in the same manner as in Example 1, an adhesive sheet (adhesive layer) according to this example was prepared. An inorganic double-sided adhesive sheet consisting of) was produced.

<Example 20>

In the preparation of the acrylic adhesive composition in Example 19, 6-acryloyloxymethyldinaphthothiophene (trade name of Sugai Chemical Industries, Ltd.) was added as an additive to 100 parts of non-volatile matter contained in the solution of acrylic polymer P9. 23 parts of “6MDNTA” (naphthothiophene-6-methyl acrylate, refractive index 1.75 or less, sometimes referred to as “6MDNTA”) was added. Otherwise, the acrylic adhesive composition according to this example was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 19, and using the obtained acrylic adhesive composition, in the same manner as in Example 1, an adhesive sheet (adhesive layer) according to this example was prepared. An inorganic double-sided adhesive sheet consisting of) was produced. The additive was added as a 10% ethyl acetate solution.

<Examples 21 to 22>

A solution of acrylic polymer P10 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 2, except that the composition of the monomer component was changed to 80 parts of POB-A, 19 parts of BA, and 1 part of AA. The Mw of acrylic polymer P10 was 1 million.

In preparing the acrylic adhesive composition in Example 13, a solution of acrylic polymer P10 was used instead of a solution of acrylic polymer P5. Otherwise, the acrylic adhesive composition according to Example 21 was prepared in the same manner as the preparation of the acrylic adhesive composition in Example 13. In addition, in the preparation of the acrylic adhesive composition according to Example 21, the amount of the epoxy-based crosslinking agent used was changed to 0.5 parts per 100 parts of non-volatile matter contained in the solution of acrylic polymer P10, and the acrylic adhesive composition according to Example 22 was prepared respectively. did.

Using each of the obtained acrylic pressure-sensitive adhesive compositions, in the same manner as Example 1, pressure-sensitive adhesive sheets (inorganic double-sided pressure-sensitive adhesive sheets consisting of an adhesive layer) for each example were produced, respectively.

<Example 23>

The composition of the monomer component is 99 parts POB-A and 1 part 2-acryloyloxyethyl-succinic acid (manufactured by Kyoesha Chemical Company, brand name “HOA-MS(N)”, hereinafter referred to as “HOA-MS”). A solution of acrylic polymer P11 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 1 except for the changes. The Mw of acrylic polymer P11 was 500,000.

The solution of the acrylic polymer P11 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile matter), 40 parts of the plasticizer A3 (POB-AL) and trimethylpentaphenyltrisiloxane (as the plasticizer A5) were added. 20 parts of Shinetsu Chemical Co., Ltd., brand name "HIVAC F-5", refractive index: 1.575, liquid at 20°C, and 0.3 parts of the epoxy-based crosslinking agent (hereinafter also referred to as crosslinking agent C1) were added, stirred and mixed, and in this example An acrylic adhesive composition was prepared.

An adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used.

<Example 24>

A solution of acrylic polymer P12 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 23, except that the composition of the monomer component was changed to 95 parts of POB-A, 2 parts of lauryl acrylate (LA), 2 parts of 2EHA, and 1 part of 4HBA. was prepared. The Mw of acrylic polymer P12 was 500,000.

The solution of the acrylic polymer P12 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile matter), 40 parts of the plasticizer A3 (POB-AL) and the plasticizer A5 (HIVAC F-5) were added. 20 parts, 0.3 parts of acyclic bifunctional isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, brand name “Coronate 2770”, hexamethylene diisocyanate (HDI) allophanate form) as crosslinking agent C2, 2 parts of acetylacetone as crosslinking retardant, crosslinking As a catalyst, 1 part of a 1% ethyl acetate solution of ferric ferric acid (0.01 part of non-volatile matter) was added and mixed with stirring to prepare an acrylic adhesive composition according to this example.

An adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used.

<Example 25>

A solution of acrylic polymer P13 was prepared in the same manner as the preparation of the acrylic polymer solution in Example 23, except that the composition of the monomer component was changed to 90 parts of POB-A, 9 parts of 2EHA, and 1 part of 4HBA. The Mw of acrylic polymer P13 was 500,000.

The solution of the acrylic polymer P13 was diluted with ethyl acetate to a polymer concentration of 30%, and to 334 parts of this solution (100 parts of non-volatile matter), 80 parts of the plasticizer A5 (HIVAC F-5) and the crosslinker C2 (Coronate 2770) were added. 0.5 parts of acetylacetone as a crosslinking retarder, 2 parts of acetylacetone as a crosslinking retardant, and 1 part of a 1% ethyl acetate solution of ferric ferric acid (0.01 part of non-volatile matter) as a crosslinking catalyst were added and mixed with stirring to prepare the acrylic adhesive composition according to this example. .

An adhesive sheet according to this example (an inorganic double-sided adhesive sheet consisting of an adhesive layer) was produced in the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used.

<Examples 26 to 28>

Solutions of acrylic polymers P14 and P15 were prepared in the same manner as the preparation of the acrylic polymer solution in Example 23, except that the composition of the monomer component was changed as shown in Table 3. The Mw of acrylic polymers P14 and P15 was 500,000 each.

The solution of the acrylic polymer P11, P14 or P15 was diluted with ethyl acetate to a polymer concentration of 30%, and for 334 parts of this solution (100 parts of non-volatile matter), the plasticizer A3 and the crosslinker C1 or C2 were added as shown in Table 3. Added together, for Examples 26 and 28, 2 parts of acetylacetone as a crosslinking retardant and 1 part of 1% ethyl acetate solution of ferric ferric iron (0.01 part of non-volatile matter) as a crosslinking catalyst were added, stirred and mixed, An acrylic adhesive composition for each example was prepared.

In the same manner as the production of the adhesive sheet in Example 1 except that the obtained acrylic adhesive composition was used, adhesive sheets (inorganic double-sided adhesive sheets consisting of an adhesive layer) for each example were produced.

<Evaluation method>

(refractive index)

For the adhesive layer (baseless double-sided adhesive sheet) for each example, the refractive index was measured using an Abbe refractometer (manufactured by ATAGO, model "DR-M4") under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. .

(Storage modulus G' and glass transition temperature)

The adhesive layers for each example were laminated to a thickness of about 1.5 mm and were used as samples for measurement. Dynamic viscoelasticity measurements were performed using the “Advanced Rheometric Expansion System (ARES)” manufactured by Rheometric Scientific under the following conditions. From the measurement results, the storage modulus G'[Pa] of the adhesive at each temperature (-20°C, -10°C, 0°C, and 80°C) was determined. In addition, the temperature corresponding to the peak top temperature of the loss tangent tan δ (loss modulus G"/storage modulus G') in the dynamic viscoelasticity measurement was determined as the glass transition temperature (Tg) [°C] of the adhesive.

[Measuring conditions]

Deformation Mode: Torsion

Measurement frequency: 1Hz

Temperature range: -50℃ to 150℃

Temperature increase rate: 5℃/min

Shape: Parallel plate 7.9mmϕ

(Total light transmittance and haze)

A test piece was used in which the adhesive layer for each example was bonded to alkali-free glass (thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.4%), and a haze meter (Murakami Shikisai Kijutsu Kenkyu) was used in a measurement environment of 23°C. Using the preparation "HM-150"), the total light transmittance and haze of the test piece were measured. The values obtained by subtracting the total light transmittance and haze of the alkali-free glass from the measured values were used as the total light transmittance [%] and haze [%] of the adhesive (layer). For the inorganic adhesive sheet composed of the adhesive layer, the total light transmittance [%] and haze [%] of the adhesive layer are the total light transmittance [%] and haze [%] of the adhesive sheet.

(Peel strength vs. glass plate)

Under a measurement environment of 23°C and 50%RH, the release liner was peeled from one side of the adhesive sheet, a PET film with a thickness of 50 μm was bonded and backed, and the test piece was cut to a size of 25 mm in width and 100 mm in length. It was done as follows. The other surface release liner was peeled from the test piece, and was pressed to the surface of an alkali glass plate (manufactured by Matsunami Glass Kogyo Co., Ltd., thickness 1.35 mm, blue plate dyeing product) as an adherend by making one reciprocation of a 2 kg roller. After leaving it for 30 minutes in the same environment, peel strength (adhesive force) [N/25 mm] was measured under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees according to JIS Z 0237:2000 using a universal tensile compression tester. ] was measured. As a universal tensile compression tester, a “tensile compression tester, TG-1kN” manufactured by Minebea Corporation was used. In addition, in the case of a single-sided adhesive sheet provided with a base material, backing of PET film is not essential.

(Bending test)

The adhesive sheet provided with the release liner for each example was cut into a rectangle of 2 cm x 10 cm, and a test piece for measurement was obtained. A cylindrical bar measuring ϕ4 mm was fixed horizontally at a height sufficient for measurement, and the test piece obtained above was hung on the bar and bent. Specifically, the test piece was hung at its longitudinal center on a bar to form an inverted U shape. Then, both ends located below the test piece were fixed with clips (13g), and a weight of 60g was hung and fixed to the clip through a 1 cm long thread, thereby applying a load to the bent portion of the test piece. In this state, the test piece was held for 1 minute in a predetermined temperature environment (-20°C, -10°C, or 0°C), and after 1 minute, the test piece was separated from the rod. Then, under the same temperature environment, the test piece was left on a horizontal surface so that the peak side of the bend was facing downward, and left for 10 minutes. The time until the end of the test piece (short side end) contacts the horizontal surface after standing for 10 minutes was measured. This test was conducted under conditions of -20°C, -10°C, and 0°C, and flexibility was evaluated based on the following criteria.

E (Excellent): In the bending test under all temperature conditions (-20℃, -10℃, and 0℃), the end of the test piece was in contact with the horizontal surface within 10 minutes.

G (Good): In a bending test under temperature conditions of -10°C and 0°C, the end of the test piece was in contact with the horizontal surface within 10 minutes.

A (Acceptable): In a bending test at a temperature of 0°C, the end of the test piece came into contact with a horizontal surface within 10 minutes.

P (Poor): In the bending test under all temperature conditions, the end of the test piece did not contact the horizontal surface or the adhesive layer peeled from the release liner within 10 minutes.

Tables 1 to 3 show the overview and evaluation results of the adhesive for each example.

As shown in Tables 1 to 3, the adhesives of Examples 3 to 5, Example 7, and Examples 9 to 28 have a refractive index of 1.55 or more, and a storage modulus at 0°C G' (0°C) of 1.0 Within the range of 10 ⁴ Pa to 1.0×10 ⁶ Pa, all results of the bending test were passing (A or higher). The adhesives in these examples were those that achieved both high refractive index and flexibility. On the other hand, the adhesives of Examples 1 to 2, Example 6 and Example 8 had a storage modulus G' ( ⁰ °C) exceeding 1.0 It was not compatible.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above.

1, 2, 3: Adhesive sheet
10: Supporting substrate
10A: side 1
10B: Side 2
21: Adhesive layer, first adhesive layer
21A: Adhesive side, first adhesive side
21B: Adhesive side
22: Second adhesive layer
22A: Second adhesive side
31, 32: release liner

Claims (10)

An adhesive having a refractive index of 1.55 or more and a storage modulus of elasticity G' at 0°C (0°C) within the range of 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa. According to paragraph 1,
An adhesive having a glass transition temperature in the range of -50°C to 0°C. According to claim 1 or 2,
The ratio of the storage elastic modulus G'(0°C) to the storage elastic modulus G'(80°C) at 80°C (G'(0°C)/G'(80°C)) is in the range of 1 to 1000, adhesive. According to any one of claims 1 to 3,
The ratio of the storage modulus G'(-10°C) at -10°C to the storage modulus G'(80°C) at 80°C (G'(-10°C)/G'(80°C)) is 1 to 1. Adhesive within the range of 1000. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to any one of claims 1 to 4. According to clause 5,
An adhesive sheet, wherein the thickness of the adhesive layer is in the range of 5 to 75 μm. According to clause 6,
Adhesion where the product (G'(0°C)×T) of the storage modulus G'(0°C)[Pa] and the thickness T[μm] of the adhesive layer is within the range of 5.0×10 ⁴ to 5.0×10 ⁷ Sheet. According to any one of claims 5 to 7,
An adhesive sheet with a total light transmittance of 85% or more. According to any one of claims 5 to 8,
An adhesive sheet having a haze value of 3% or less. According to any one of claims 5 to 9,
An adhesive sheet having a peel strength to a glass plate of 0.1 N/25 mm or more.

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