JP2017095658A - Adhesive composition, optical member and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition that has an excellent durability, folding resistance, humidification reliability and metal corrosion inhibition/prevention.SOLUTION: An adhesive composition has a pentaerythritol compound (B) of more than 0 pt.mass and 0.05 pt.mass or less based on a main agent (A) comprising a curable compound comprising a predetermined acrylic compound, and has a post-curing glass transition temperature of -70°C or more and -60°C or less.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition suitable for use in a flexible device, and an optical member and a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition.

  Currently, a liquid crystal display panel (LCD), a plasma display panel (PDP), or the like is used as a display panel. Usually, a laminated body in which a plurality of films are laminated is bonded to the display panel surface. For example, in an LCD, an optical film such as a polarizing plate, a retardation plate, a viewing angle widening film, and a brightness improving film is usually laminated on the surface of a liquid crystal panel. And each layer which comprises a display panel is bonded together by the adhesive layer normally formed with various adhesives.

  Recently, flexible displays including curved display have been developed from the viewpoints of design and diversity of usage, and display panels have been required to have flexibility. An organic electroluminescence panel (OLED) is mainly used for a flexible display such as a curved display.

  In addition to the optical properties and durability required for conventional flat display panels, the optical film laminate used in this flexible display is subjected to a long-term holding or bending test with the optical film deformed. It is required that no peeling or lifting occurs.

  As an adhesive layer used in a conventional optical film laminate for a flat display panel, Patent Document 1 discloses an alkyl (meth) acrylate monomer and an alkoxy as an adhesive for bonding a touch panel member which is one of optical films. A pressure-sensitive adhesive for attaching a touch panel member, which is a copolymer containing an alkyl (meth) acrylate monomer, has been proposed. Patent Document 2 discloses a photopolymerizable pressure-sensitive adhesive composition containing an acrylic prepolymer containing N-vinyl-2-pyrrolidone and hydroxyalkyl (meth) acrylate, dipentaerythritol hexaacrylate, and a photopolymerization initiator. Proposed.

JP 2013-186808 A JP 2011-099078 A

  Flexible displays such as organic electroluminescence panels (OLEDs) are expected to be used in a variety of environments, so they can be used in a wide range of temperatures, and can be folded at both high and low temperatures ( Bend resistance). However, when the pressure-sensitive adhesive described in Patent Document 1 or Patent Document 2 is used for the pressure-sensitive adhesive layer of a flexible display, it can be satisfied in terms of durability and folding resistance (bending resistance) under both high temperature and low temperature conditions. It was not a thing. In addition, considering the diversification of the usage environment of flexible displays, the adhesive layer used in flexible displays has high humidification reliability (property that haze rise can be suppressed even in high humidity environments) and metal corrosion suppression / Performance such as prevention is also required.

  Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a pressure-sensitive adhesive composition excellent in durability, folding resistance, humidification reliability, and metal corrosion inhibition / prevention.

  As a result of intensive studies to solve the above problems, the present inventors have found that 0 mass of pentaerythritol compound (B) is added to the main agent (A) comprising a curable compound containing a predetermined acrylic compound. It is found that the above-mentioned problems are solved by a pressure-sensitive adhesive composition containing more than 0.05 parts by mass and not more than 0.05 parts by mass and having a glass transition temperature after curing of −70 ° C. or more and −60 ° C. or less. It came to.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive composition excellent in durability, folding tolerance, humidification reliability, and metal corrosion suppression can be provided. The pressure-sensitive adhesive composition according to the present invention is particularly suitable for flexible display applications.

FIG. 1 is a diagram schematically showing a metal corrosion inhibition / prevention test system.

  Embodiments of the present invention will be described below. In addition, this invention is not limited only to the following embodiment.

  In this specification, unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 ° C. or more and 25 ° C. or less) / relative humidity 40% RH or more and 50% RH or less.

[Adhesive composition]
One aspect of the present invention comprises 100 parts by mass of a main agent (A) comprising a curable compound; and more than 0 parts by mass and 0.05 parts by mass or less of a pentaerythritol compound (B); Is a combination of a (meth) acrylic acid ester monomer (a-1) and a hydroxyl group-containing (meth) acrylic monomer (a-2), and a structural unit derived from the (meth) acrylic acid ester monomer (a-1) Including at least one copolymer (a-3) comprising (1) and the structural unit (2) derived from the hydroxyl group-containing (meth) acrylic monomer (a-2); glass transition temperature after curing; Is a pressure-sensitive adhesive composition having a temperature of −70 ° C. or higher and −60 ° C. or lower. ADVANTAGE OF THE INVENTION According to this invention, the adhesive composition excellent in durability, folding tolerance, humidification reliability, and metal corrosion suppression can be provided.

  The details of why the above effect is obtained by the pressure-sensitive adhesive composition of the present invention are not clear, but are considered as follows. That is, if the glass transition temperature after curing of the pressure-sensitive adhesive composition is too high, the cured product becomes too soft at high temperatures (for example, 85 ° C.), and it is considered difficult to obtain folding resistance at high temperatures. In addition, if the glass transition temperature after curing of the pressure-sensitive adhesive composition is too low, sufficient flexibility cannot be obtained in the cured product at a low temperature (for example, −20 ° C.), and it is difficult to obtain folding resistance at a low temperature. It is considered to be. On the other hand, the present inventors have (meth) acrylic acid ester monomer (a-1) (or a copolymer (a-3) containing a structural unit derived therefrom) having a low homopolymer glass transition temperature. Is used as the main agent, the glass transition temperature after curing of the pressure-sensitive adhesive composition is -70 ° C to -60 ° C, high temperature (for example, 85 ° C) and low temperature (for example, -20 ° C) It has been found that the folding resistance in the case is improved.

  Furthermore, although the detailed reason is unknown, the folding resistance is improved by using the pentaerythritol compound (B), unlike the case of using a polyethylene glycol compound or a trimethylolpropane compound having an ethylenically unsaturated group. The present inventors have found out. Since the pressure-sensitive adhesive composition of the present invention contains the pentaerythritol compound (B), folding resistance, particularly folding resistance at a high temperature (for example, 85 ° C.) is further improved due to its flexible molecular structure. Conceivable. In addition, by suppressing the content of the pentaerythritol compound (B) to a certain level, the hardness of the pressure-sensitive adhesive composition obtained by curing the pressure-sensitive adhesive composition is excessively increased, and the adhesive strength and durability are reduced. Can also be prevented.

  Furthermore, in the pressure-sensitive adhesive composition of the present invention, curability containing a highly polar hydroxyl group-containing (meth) acrylic monomer (a-2) (or a copolymer (a-3) containing a structural unit derived therefrom). It is a requirement to use a compound as the main agent. By adopting such a configuration, the adhesiveness and durability of the pentaerythritol compound (B) are suppressed to a certain level, possibly due to the high polarity of the hydroxyl group-containing (meth) acrylic monomer (a-2). It is thought that sex can be secured. Further, if it is a hydroxyl group-containing (meth) acrylic monomer (a-2) (or a copolymer (a-3) containing a structural unit derived therefrom), the reliability of humidification is higher than that of an acid component such as acrylic acid. It is considered that the deterioration of the property or metal corrosion hardly occurs.

  In addition, the said mechanism is based on estimation and this invention is not restrict | limited to the said mechanism at all.

  In the pressure-sensitive adhesive composition of the present invention, the gel fraction measured by the method described in Examples is preferably 70% or more and 90% or less, and more preferably 75% or more and 84% or less. If it is such a range, a punching process and a slit process can be rapidly performed as an optical member provided with the adhesive layer. In order to set the gel fraction as described above, the conditions may be appropriately selected, for example, by adjusting the amount of each component added to the above range.

The adhesive composition of the present invention has a storage elastic modulus G ′ (85) at 85 ° C. after curing of more than 1 × 10 ⁴ Pa and less than 4 × 10 ⁴ Pa from the viewpoint of bending resistance at high temperatures. Is preferable, and 2.2 × 10 ^{4 to} 3.5 × 10 ⁴ Pa is more preferable.

The pressure-sensitive adhesive composition of the present invention has a storage elastic modulus G ′ (−20) at −20 ° C. after curing of 1 × 10 ⁴ Pa or more and less than 5 × 10 ⁴ Pa from the viewpoint of bending resistance at low temperatures. Is preferably 1.5 × 10 ⁴ Pa or more and 3.2 × 10 ⁴ Pa or less.

  In addition, the value measured by the method as described in an Example is employ | adopted for storage elastic modulus G '(85) and G' (-20). The storage elastic moduli G ′ (85) and G ′ (−20) can be controlled by the composition of the main agent (A).

  The glass transition temperature after curing of the pressure-sensitive adhesive composition of the present invention may be −70 ° C. or more and −60 ° C. or less, but from the viewpoint of folding resistance at low temperatures, it may be −66 ° C. or more and −60 ° C. or less. preferable. In addition, the glass transition temperature after hardening of an adhesive composition can be calculated | required by the method as described in an Example. In order to bring the glass transition temperature after curing of the pressure-sensitive adhesive composition into the above range, the monomer used for the preparation of the main agent (A) may be appropriately selected in consideration of the glass transition temperature of the homopolymer. Alternatively, a (meth) acrylic acid ester monomer (a-1) having a low glass transition temperature of the homopolymer and a monomer having a relatively high glass transition temperature of the homopolymer (for example, a hydroxyl group-containing (meth) acrylic monomer (a-2) ) Or the monomer (a ′)) copolymerizable with the component (a-1) and the component (a-2) may be appropriately adjusted.

  Hereinafter, each component of the pressure-sensitive adhesive composition of the present invention will be described in detail.

  In this specification, “(meth) acrylic acid ester monomer” is a general term for acrylic acid ester monomers and methacrylic acid ester monomers. Similarly, a compound containing (meth) such as (meth) acrylic acid is a general term for a compound having “meta” in the name and a compound not having “meta”. For this reason, "(meth) acryl" includes both acrylic and methacrylic. “(Meth) acrylate monomer” includes both acrylate monomers and methacrylate monomers. “(Meth) acrylic acid” includes both acrylic acid and methacrylic acid.

  In the present specification, the “pressure-sensitive adhesive composition” is also simply referred to as “pressure-sensitive adhesive”. In this specification, “(co) polymer” is a general term for “polymer (homopolymer)” and “copolymer”.

[Main agent (A)]
The main agent (A) used in the present invention comprises a curable compound (excluding the pentaerythritol compound (B)). In the present invention, (meth) acrylic acid ester monomer (a-1) (hereinafter, also simply referred to as “(a-1) component”) and hydroxyl group-containing (meth) acrylic monomer as constituents of main agent (A) (A-2) (hereinafter also simply referred to as “component (a-2)”) and / or the structural unit (1) derived from the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group The copolymer (a-3) containing the structural unit (2) derived from a (meth) acryl monomer (a-2) is included. The main agent (A) contains the copolymer (a-3) containing the structural unit (1) derived from the component (a-1) and / or the component (a-1) having a low glass transition temperature of the homopolymer. The glass transition temperature after curing of the pressure-sensitive adhesive composition can be lowered to −70 ° C. or higher and −60 ° C. or lower. Moreover, when the main component (A) contains the copolymer (a-3) containing the structural unit (2) derived from the highly polar component (a-2) and / or component (a-2), pentaerythritol The adhesiveness with respect to optical films, such as a highly polar polarizing plate, can be ensured, suppressing content of a compound (B) to a fixed level. As the curable compound contained in the main agent (A), in addition to the above, active energy ray-curable monomers such as (meth) acrylic compounds and the (co) polymers thereof, (meth) acryloyl groups, vinyl groups, allyl groups And polyester resins containing a polymerizable functional group such as a propenyl group, a dithiocarbamate group, a diazo group, a cinnamylidene group and / or a cinnamoyl group, a polyether resin, a polyurethane resin or an epoxy resin, and combinations thereof.

  The viscosity of the main agent (A) is preferably 500 mPa · s or more and less than 5000 mPa · s, and more preferably 1000 mPa · s or more and 4500 mPa · s or less, from the viewpoint of applicability and adhesiveness of the pressure-sensitive adhesive composition. In addition, said viscosity is a value measured by the method as described in an Example.

As a preferable form of the main agent (A) comprising the curable compound according to the present invention,
(1) Form containing component (a-1) and component (a-2) (2) Component derived from component (a-1), component (a-2), and component (a-1) (1 ) And (a-2) a form containing a copolymer (a-3) containing the structural unit (2) derived from the component (hereinafter also simply referred to as copolymer (a-3)) (the curable compound is a monomer and It is a form made of polymer, so-called polymer syrup form)
(3) Form consisting of copolymer (a-3) (form where the curable compound consists only of polymer)
Is mentioned.

  By including such a main agent (A) in the pressure-sensitive adhesive composition of the present invention, it is considered that the pressure-sensitive adhesive layer obtained after curing has the significance of ensuring the tackiness and basic characteristics.

  Among these, from the viewpoint of ease of forming the pressure-sensitive adhesive layer according to the present invention, and the effect of the present invention can be more efficiently exhibited, the curable compound is a copolymer (a-3). It is preferable to include (form (2) or (3) above), and the form (2) (so-called polymer syrup form) is more preferable.

<(A-1) (Meth) acrylic acid ester monomer>
The (meth) acrylic acid ester monomer (a-1) may be in a form in which an alkyl group or a group represented by — (A—O) _p -Q is introduced into the ester site of the (meth) acrylic acid ester. There is no particular limitation. However, in the above “— (A—O) _p -Q”, A is an alkylene group, Q is an alkyl group, and p is an integer of 1-20.

  A copolymer (a-3) in which the main agent (A) contains the structural unit (1) derived from the (meth) acrylic acid ester monomer (a-1) and / or the (meth) acrylic acid ester monomer (a-1). By including, the glass transition temperature after hardening can be made low. Thereby, the bending tolerance at low temperature can be improved without lowering the adhesiveness.

The carbon number of the alkyl group or the group represented by — (A—O) _p —Q is not particularly limited. From the viewpoint of compatibility and keeping the glass transition temperature low, the number of carbon atoms is preferably 1 or more and 20 or less, more preferably 2 or more and 18 or less, and even more preferably 3 or more and 16 or less. It is particularly preferably 12 or more and 12 or less. The ester moiety of the (meth) acrylic acid ester may be linear, branched, or cyclic, but from the viewpoint of lowering the glass transition temperature, it must be linear or branched. Is preferred. In the case of an annular shape, the number of carbon atoms is 3 or more.

In the group represented by-(A-O) _p -Q, A represents a carbon number of 1 or more and 4 or less (from the viewpoint of improving adhesiveness and durability, and efficiently exhibiting the desired effect of the present invention ( That is, it is preferably a methylene group, an ethylene group, a propylene group, or a butylene group, and more preferably a carbon number of 2 or more and 3 or less (that is, an ethylene group or a propylene group). At this time, p is preferably an integer of 1 or more and 6 or less, more preferably an integer of 1 or more and 4 or less, and further preferably 2 or 3. Q is an alkyl group. Such an alkyl group may be linear or branched, and the number of carbon atoms is preferably 1 or more and 12 or less, more preferably from the viewpoint of efficiently exhibiting the intended effect of the present invention. It is 2 or more and 10 or less, more preferably 2 or more and 8 or less. Specific examples of such alkyl groups include those listed above.

  The (meth) acrylic acid ester monomer (a-1) is typically represented by the following formula (1):

Here, in the above formula (1),
R ₁ is a hydrogen atom or a methyl group, and R ₂ is a group represented by the above alkyl group, alkoxyalkyl group, or — (A—O) _p —Q.

The alkyl group in _{R 2} of formula (1) is not particularly limited, for example, a methyl group, an ethyl group, n- propyl group, an isopropyl group, n- butyl group, sec- butyl group, tert- butyl group, isobutyl Group, n-hexyl group, 2-hexyl group, 3-hexyl group, cyclohexyl group, 1-methylcyclohexyl group, n-heptyl group, 2-heptyl group, 3-heptyl group, isoheptyl group, tert-heptyl group, n -Octyl, isooctyl, tert-octyl, 2-ethylhexyl, nonyl, isononyl, decyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, or octadecyl Can be mentioned. In particular, a methyl group, a butyl group, a 2-ethylhexyl group, an n-hexyl group, a nonyl group, and an isononyl group are preferable from the viewpoint of ensuring adhesiveness and ensuring basic characteristics.

Therefore, specific examples of the (meth) acrylic acid ester monomer (a-1) in which R ₂ in the formula (1) is an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Examples include hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and lauryl (meth) acrylate.

The group represented by — (A—O) _p —Q in R ₂ of Formula (1) may be an alkoxyalkyl group. Examples of such an alkoxyalkyl group include a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, a propoxyethyl group, a butoxyethyl group, a methoxypropyl group, a methoxybutyl group, and a 2-ethylhexyloxyalkyl group (the carbon number of the alkyl group is 1). 4 or less) is preferable.

Specific examples of the (meth) acrylic acid ester monomer (a-1) in which R _{2 in the} formula (1) is represented by-(AO) _p -Q include methoxyethyl (meth) acrylate, ethoxymethyl (Meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, ethoxy-tri Ethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, propoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate Relate, 2-ethylhexyl - Jigurukoru (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, methoxy dipropylene glycol (meth) acrylate.

  Among the specific examples of the (meth) acrylic acid ester monomer (a-1), in particular, from the viewpoint of lowering the glass transition temperature and polarity after curing and ensuring excellent flexibility and adhesiveness. The (meth) acrylic acid ester monomer (a-1) contained in (A) is preferably a homopolymer having a glass transition temperature of less than −60 ° C., more specifically, 2-ethylhexyl (meth). Particularly preferred is one or more selected from the group consisting of acrylate, 2-ethylhexyl-diglycol (meth) acrylate and ethoxy-diethylene glycol (meth) acrylate.

  These components (a-1) can be used alone or in admixture of two or more. As the component (a-1), a commercially available product or a synthetic product may be used.

  As a commercial item of (a-1) component, AEH, AME (above, Nippon Shokubai Co., Ltd.), light acrylate (registered trademark) EC-A, light acrylate (registered trademark) MTG-A, light acrylate (registered trademark) ) EHDG-AT, Light Acrylate (registered trademark) 130A, Light Acrylate (registered trademark) DPM-A, Light Ester L (above, manufactured by Kyoeisha Chemical Co., Ltd.), Biscote # 190, 2-MTA, MPE400A, MPE550A (above, Osaka Organic Chemical Industry Co., Ltd.), AM-90G, AM-130G, (manufactured by Shin-Nakamura Chemical Co., Ltd.) are suitable.

<(A-2) Hydroxyl group-containing (meth) acrylic monomer>
Copolymer (a-3) comprising a structural unit (2) derived from a highly polar hydroxyl group-containing (meth) acrylic monomer (a-2) and / or a hydroxyl group-containing (meth) acrylic monomer (a-2) Is contained in the main agent (A), it is possible to ensure excellent adhesion to an optical film such as a highly polar polarizing plate while suppressing the content of the pentaerythritol compound (B) to a certain level.

  The hydroxyl group-containing (meth) acrylic monomer is typically represented by the following formula (2-1):

Here, in the above formula (2-1),
R ₅ is a hydrogen atom or a methyl group,
R ₆ is a divalent organic group.

  Here, the divalent organic group is not particularly limited, but an alkylene group having 1 to 10 carbon atoms is preferable. The above-mentioned thing is mentioned similarly as a C1-C10 alkylene group. The alkylene group has at least one alkyl group having 1 to 8 carbon atoms, a phenoxyalkyl group (carbon number of the alkyl group: 1 to 8 carbon atoms), a phenyl group, or a cyclohexyl group as a substituent. It may be. The alkyl group having 1 to 8 carbon atoms can be appropriately selected from the above.

  The hydroxyl group-containing (meth) acrylic monomer may have a structure represented by the following formula (2-2).

Here, in the above formula (2-2),
R ₈ is a hydrogen atom or a methyl group,
R ₉ is a single bond or a divalent organic group,
R ₁₀ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

  The divalent organic group is not particularly limited, but an alkylene group having 1 to 10 carbon atoms is preferable. The alkylene group may have at least one alkyl group having 1 to 8 carbon atoms, a phenyl group, or a cyclohexyl group as a substituent. The alkylene group having 1 to 10 carbon atoms is a divalent substituent obtained by removing one hydrogen atom from the following alkyl group having 1 to 10 carbon atoms.

  Examples of the alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group, isobutyl group, n-hexyl group, 2-hexyl group, 3-hexyl group, cyclohexyl group, 1-methylcyclohexyl group, n-heptyl group, 2-heptyl group, 3-heptyl group, isoheptyl group, tert-heptyl group, n-octyl group, isooctyl group, tert-octyl group, A 2-ethylhexyl group, a nonyl group, an isononyl group, a decyl group, and the like are preferable.

  From the above, as component (a-2), 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxymethyl (meth) acrylate, 3- Hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N- (1-methyl-2-hydroxyethyl) (Meth) acrylamide, N-isopropyl-hydroxy (meth) acrylamide and the like are preferable. Among these, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and the like are preferable from the viewpoint that the glass transition temperature of the homopolymer is relatively low.

  (A-2) As a commercial item of a component, BHEA, HPA, HEMA, HPMA (above, made by Nippon Shokubai Co., Ltd.), 4HBA, CHDMMA (above, made by Nippon Kasei Co., Ltd.), HEA, HPA, 4-HBA ( As described above, Osaka Organic Chemical Industry Co., Ltd., Light Ester HOA (N), Light Ester HOP-A (N), Light Acrylate (registered trademark) HOB-A (above, Kyoeisha Chemical Co., Ltd.), HEAA (registered trademark) ) (Manufactured by KJ Chemicals Co., Ltd.), N-MAN (manufactured by Miki Riken Kogyo Co., Ltd.) and the like.

  These components (a-2) can be used alone or in combination of two or more. In addition, as the component (a-2), a commercially available product or a synthetic product may be used.

<Monomer copolymerizable with component (a ′) (a-1) and component (a-2)>
The main agent (A) may contain a monomer (a ′) component copolymerizable with the component (a-1) and the component (a-2) as long as the objective effect of the present invention is achieved. As the component (a ′), a (meth) acrylic monomer (a′-1) having an amide group (hereinafter also referred to as “(a′-1) component”), a macromonomer having a polymerizable functional group (a ′ -2) (hereinafter also referred to as “(a′-2) component”) and other polymerizable monomers (a′-3) (hereinafter also referred to as “(a′-3) component”).

<<(a'-1) (Meth) acrylic monomer having amide group >>
The (a′-1) component is not particularly limited as long as it has an amide group in the (meth) acrylic monomer. The component (a′-1) is typically represented by the following formula (3):

Here, in the above formula (3),
R ₈ ′ is a hydrogen atom or a methyl group,
R ₉ ′ is a single bond or a divalent organic group,
R ₁₀ ′ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms,
R ₁₁ ′ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, an epoxy group, an alkoxy group having 1 to 6 carbon atoms, or a dimethylamino group.

  The divalent organic group is not particularly limited, but an alkylene group having 1 to 10 carbon atoms is preferable. Further, the alkylene group or the acyl group may have at least one alkyl group having 1 to 8 carbon atoms, a phenyl group, or a cyclohexyl group as a substituent.

  The alkyl group having 1 to 10 carbon atoms is as described above for the formula (2-2).

  The number of carbon atoms of the acyl group is not particularly limited, but is preferably 1 to 18 carbon atoms, more preferably 1 to 6 carbon atoms. The acyl group includes an acetoacetoxy group.

  Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, sec-butoxy group, tert-butoxy group, isobutoxy group, n-hexyloxy group, 2- A hexyloxy group, a 3-hexyloxy group, a cyclohexyloxy group, and the like are preferable.

R ₁₀ ′ and R ₁₁ ′ may form a ring with each other, and the ring has an oxygen atom (that is, an oxygen-containing heterocyclic group) or a sulfur atom (that is, a sulfur-containing heterocyclic group). You may do it.

  From the above, (meth) acryloylmorpholine, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide, N, N-dimethylaminopropyl (meth) ) Acrylamide, N-isopropyl (meth) acrylamide, Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-methoxymethylacrylamide, Nt-butylacrylamide, N, N′-methylenebisacrylamide, etc. are suitable Among them, from the viewpoint of improving adhesiveness, (meth) acryloylmorpholine, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylic Such as soil preferred.

  As commercial products of the component (a′-1), ACMO (registered trademark), DMAPAA (registered trademark), DMAA (registered trademark), NIPAM (registered trademark), DEAA (registered trademark) (above, manufactured by KJ Chemicals Corporation) ), DAAm (Nippon Kasei Co., Ltd.), NBMA, IBMA, NMMA, TBAA, MBAA (MRC Unitech Co., Ltd.) and the like are suitable.

<<(a'-2) polymerizable functional group-containing macromonomer >>
The main agent (A) according to the present invention may contain a macromonomer (a′-2) having a polymerizable functional group. The component (a′-2) is a high molecular weight monomer having a polymerizable functional group (unsaturated group), and includes a polymer chain portion and a polymerizable functional group portion.

  Bending resistance (bending resistance) is improved by including in the pressure-sensitive adhesive layer a polymer polymerized (cured) using such a monomer. The mechanism is considered to vary depending on the glass transition temperature of the polymer chain portion of the macromonomer. Specifically, when the glass transition temperature of the polymer chain portion is high, the polymer chain portion forms a hard segment in the pressure-sensitive adhesive layer, thereby causing a cohesive force in the pressure-sensitive adhesive layer. Thereby, the adhesive force to a base material increases and it is thought that bending tolerance improves. On the other hand, when the glass transition temperature of the polymer chain portion of the macromonomer is low, the pressure-sensitive adhesive layer becomes flexible and the followability to the base material is improved, so that the bending resistance is considered to be improved. In addition, the said mechanism is based on estimation and this invention is not restrict | limited to the said mechanism at all.

  The polymerizable functional group of the component (a′-2) is preferably a group having an ethylenically unsaturated double bond (ethylenically unsaturated group). Specifically, at least one selected from the group consisting of a vinyl group, an allyl group, a (meth) acryloyl group, and a propenyl group is preferable. The polymerizable group is preferably present at the end of the macromonomer, and more preferably present only at one end of the macromonomer from the viewpoint of stability during polymerization. However, the polymerizable group may exist as a side chain of the macromonomer, or may exist at both ends of the macromonomer chain.

  The polymer chain portion of the component (a′-2) is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, stearyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) It is preferably a (co) polymer having a repeating unit derived from acrylate, styrene, acrylonitrile, hydroxy (meth) acrylate, ethylhexyl (meth) acrylate, dimethylsiloxane or the like as a main structural unit. These polymer chain portions may be composed of a single repeating unit, or may be composed of a plurality of repeating units. Further, when the polymer chain is a copolymer composed of a plurality of repeating units, the repeating form is not limited, and any of an alternating copolymer, a random copolymer, and a block copolymer may be used.

  The component (a′-2) is typically represented by the following formula (4):

Here, in the above formula (4), R ₁₂ represents a hydrogen atom or a methyl group, and X ₁ represents a single bond or a divalent linking group.

  Examples of the divalent linking group include a linear, branched or cyclic alkylene group, an aralkylene group, and an arylene group. These may further have a substituent such as a hydroxyl group or a cyano group. The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, an octylene group, and a decylene group. Among these, a methylene group, an ethylene group, a propylene group, and the like are preferable. The carbon number of the aralkylene group is preferably 7 or more and 13 or less. Examples of the aralkylene group include a benzylidene group and a cinnamylidene group. The arylene group preferably has 6 to 12 carbon atoms. Examples of the arylene group include a phenylene group, a cumenylene group, a mesitylene group, a tolylene group, and a xylylene group. Among these, a phenylene group is preferable.

In the divalent linking group, —NR ₂ —, —COO—, —OCO—, —O—, —S—, —SO ₂ NH—, —NHSO ₂ —, —NHCOO—, —OCONH— Alternatively, a group derived from a heterocyclic ring, or the like may be interposed as a linking group. R ₂ is a hydrogen atom or an alkyl group such as a methyl group, an ethyl group, or a propyl group.

In the above formula (4), X ₂ represents methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, stearyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) ) A polymer obtained by homopolymerization or copolymerization of one or two or more monomers selected from acrylate, styrene, and acrylonitrile, or a polysiloxane (polyorganosiloxane) in which an organic group is bonded to a silicon atom. Among them, X ₂ is methyl (meth) acrylate, styrene, n- butyl (meth) acrylate, isobutyl (meth) acrylate homopolymer is not formed by polymers, acrylonitrile and made by copolymerizing styrene polymers or polyorganosiloxanes Preferably there is. Furthermore, from the viewpoint of durability at high temperatures, X ₂ is particularly preferably a polymer obtained by homopolymerizing methyl (meth) acrylate, styrene or isobutyl (meth) acrylate, or a polymer obtained by copolymerizing acrylonitrile and styrene. . Alternatively, from the viewpoint of bending resistance at low temperatures, X ₂ is preferably polyorganosiloxane, and particularly preferably polydimethylsiloxane. In addition, as long as it does not affect the performance of an adhesive, a part of methyl group of polydimethylsiloxane may be substituted by organic groups (ethyl group, phenyl group, etc.) other than a hydrogen atom or a methyl group.

  The polydimethylsiloxane can be obtained by hydrolyzing and condensing dimethyldialkoxysilane such as dimethyldimethoxysilane and dimethyldiethoxysilane. In this case, an organic group other than a methyl group can be introduced into polydimethylsiloxane by using together an alkoxysilane having an organic group other than a methyl group (for example, diethyldiethoxysilane). In addition to the dialkoxy silane compound, a small amount of trialkoxy silane compound may be added.

  The number average molecular weight (Mn) of the component (a′-2) is preferably in the range of 2,000 to 20,000, more preferably in the range of 2,000 to 10,000, and in the range of 4,000 to 8,000. More preferably. When the number average molecular weight (Mn) is 2000 or more, the performance of the pressure-sensitive adhesive is improved even if the amount of the component (a′-2) added when synthesizing the copolymer (a-3) is small. be able to. On the other hand, if it is 20000 or less, the viscosity of the pressure-sensitive adhesive is low and the workability is good. The value of the number average molecular weight (Mn) can be controlled by appropriately selecting the amounts of a chain transfer agent and a polymerization initiator added to the polymerization system. In addition, in this invention, the value of polystyrene conversion measured by GPC (gel permeation chromatography) method shall be employ | adopted for the number average molecular weight (Mn) of a macromonomer.

  As the component (a′-2), a commercially available product or a synthetic product may be used. When the component (a′-2) is synthesized, there is no particular limitation on the synthesis method. For example, (1) a polymer chain (living polymer anion) constituting a macromonomer is produced by living anion polymerization, and methacrylic acid chloride is produced in this. (2) In the presence of a chain transfer agent such as mercaptoacetic acid, a radical polymerizable monomer such as methyl methacrylate is polymerized to obtain an oligomer having a carboxyl group at the end, and then this is reacted with methacrylic acid. (3) In the presence of an azo polymerization initiator containing a carboxyl group, a radical polymerizable monomer such as methyl methacrylate is polymerized to obtain an oligomer having a carboxyl group at the end, and then methacrylic acid. Any method such as a method of forming a macromonomer with glycidyl can be used.

By producing a macromonomer using the method as described above, for example, the following groups are introduced as the divalent linking group represented by X ₁ in the above formula (4).

  As a commercially available product of the component (a′-2), for example, a macromonomer (product name: 45% AA-6 (AA-6S) whose terminal is a methacryl group and whose polymer chain portion is polymethyl methacrylate (PMMA). ), AA-6; manufactured by Toagosei Co., Ltd.), a macromonomer whose polymer chain part is polystyrene (product name: AS-6S, AS-6; manufactured by Toagosei Co., Ltd.), and the polymer chain part is styrene / acrylonitrile. Macromonomer (product name: AN-6S; manufactured by Toagosei Co., Ltd.) as a copolymer, macromonomer whose polymer chain part is polybutyl acrylate (product name: AB-6; manufactured by Toagosei Co., Ltd.), polymer chain part Is a macromonomer (product name: AW-6S; manufactured by Toagosei Co., Ltd.), and the polymer chain portion is polydimethylsilane. Hexane at a macromonomer (product name: AK-5; manufactured by Toagosei Co., Ltd.) and the like can be used. In addition, these macromonomers may be used independently and may be used together 2 or more types.

<<(a'-3) Other polymerizable monomers >>
Specific examples of the polymerizable monomer copolymerizable with the component (a-1) and the component (a-2) include epoxy groups such as glycidyl (meth) acrylate and methylglycidyl (meth) acrylate. Acrylic monomer having amino groups such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, N-tert-butylaminoethyl (meth) acrylate, 2-((meth) acryloxy) ethyltrimethylammonium chloride (Meth) acrylic monomer; (meth) acrylic monomer having urethane group such as urethane (meth) acrylate; (meth) having phenyl group such as p-tert-butylphenyl (meth) acrylate and o-biphenyl (meth) acrylate Acrylic vinyl A vinyl monomer having a silane group such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethyl) silane, vinyltriacetylsilane, methacryloyloxypropyltrimethoxysilane; styrene, chlorostyrene, α-methylstyrene, Examples include vinyl toluene, vinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, vinyl pyridine and the like. These other monomers may be used alone or in combination of two or more.

<< Content of each component in the form (1) >>
It is preferable that content of (a-1) component is 70 mass% or more with respect to the whole quantity of a main ingredient (A) from a viewpoint of making the glass transition temperature after hardening low. The upper limit of the content of the component (a-1) is preferably 99.9% by mass or less because various durability is excellent, bending resistance at high temperature is excellent, and adhesive strength at high temperature is improved. In addition, the content of the component (a-1) is more preferably 75% by mass or more and 95% by mass or less from the viewpoint of securing excellent adhesive force while lowering the glass transition temperature after curing of the pressure-sensitive adhesive composition. 75 mass% or more and 90 mass% or less is more preferable.

  The content of the component (a-2) is preferably 0.1% by mass or more and 30% by mass or less, based on the total amount of the main agent (A), from the viewpoint of improving adhesiveness and ensuring durability. % To 25% by mass is more preferable.

  The content of the component (a ′) is preferably 0% by mass or more and 10% by mass or less with respect to the total amount of the main agent (A). From the viewpoint of sufficiently securing the amount of the component (a-1) or the component (a-2), the content of the component (a ′) is more preferably 0% by mass or more and 5% by mass or less.

<< Form (2) >>
As one form according to the present invention, the main component (A) is derived from the component (a-1), the component (a-2), and the structural unit (1) derived from the component (a-1) and the component (a-2). The form (form which a curable compound consists of a monomer and a polymer) containing the copolymer (a-3) (henceforth a copolymer (a-3)) containing a unit (2) is mentioned. In this embodiment, among the raw material monomers of the copolymer (a-3), the (a-1) component, the (a-2) component which are unreacted raw material monomers, and the (a ′) component which is added as necessary It is a so-called polymer syrup form that is a solvent for dissolving the copolymer (a-3).

  The preferred content of the component (a-1), the component (a-2), and the component (a ′) in the form (2) is the << content of each component in the form (1) >>. Since it is the same as the preferable content demonstrated, description is abbreviate | omitted here.

  Moreover, suitable content of each structural unit of the copolymer (a-3) contained in the form of (2) is each component demonstrated in the section of << content of each component in the form of said (1) >>. Suitable contents of (component (a-1), component (a-2), component (a ′)) are applied as they are.

  That is, the copolymer (a-3) contained in the form of (2) is a structural unit derived from the (meth) acrylic acid ester monomer (a-1) 70% by mass or more and 99.9% by mass or less, and contains a hydroxyl group. Structural unit derived from (meth) acrylic monomer (a-2) 0.1% by mass or more and 30% by mass or less, and derived from monomer (a ′) copolymerizable with component (a-1) and component (a-2) 0 mass% or more and 10 mass% or less (however, the total amount of the structural units derived from the component (a-1), the component (a-2), and the component (a ′) is 100 mass%). Is preferred. The copolymer (a-3) contained in the form of (2) is more preferably a structural unit derived from the (meth) acrylic acid ester monomer (a-1) of 75% by mass or more and 95% by mass or less, containing a hydroxyl group. Constitutional unit derived from (meth) acrylic monomer (a-2) 5% by mass or more and 25% by mass or less, and (a-1) component derived from monomer (a ′) copolymerizable with component (a-2) and component (a-2) Unit 0 mass% or more and 5 mass% or less (however, the total amount of the structural unit derived from said (a-1) component, (a-2) component, and (a ') component is 100 mass%).

  In the form of (2), the content of the copolymer (a-3) with respect to the total amount (total mass) of the main agent (A) is good in the applicability of the pressure-sensitive adhesive composition to the adherend, and is durable. From the viewpoint of excellent folding resistance, it is 5% by mass or more and 25% by mass or less, and more preferably 7% by mass or more and 20% by mass or less. The content of the copolymer (a-3) can be controlled, for example, by controlling the polymerization rate in a bulk polymerization method using a photopolymerization initiator described later.

<< Form (3) >>
As one form which concerns on this invention, the form (form which a sclerosing | hardenable compound consists only of a polymer) whose main ingredient (A) consists of a copolymer (a-3) is mentioned.

  The preferred content of each constituent unit of the copolymer (a-3) contained in the form of (3) has been described in the section << Content of each component in the form of (1) and (2) >>. Suitable content of each component ((a-1) component, (a-2) component, and (a ') component) is applied as it is.

[Production of copolymer (a-3)]
In the form of (2) or (3) above, the method for producing the copolymer (a-3) that can be contained in the main agent (A) is not particularly limited, and is a solution polymerization method using a polymerization initiator, a block shape. Conventionally known methods such as a polymerization method, an emulsion polymerization method, a suspension polymerization method, a reverse phase suspension polymerization method, a thin film polymerization method, and a spray polymerization method can be used. Examples of the polymerization control method include adiabatic polymerization, temperature controlled polymerization, and isothermal polymerization. As the polymerization initiator, either a thermal polymerization initiator or a photopolymerization initiator may be used. Further, in addition to or in addition to the method of initiating polymerization with a polymerization initiator, a method of initiating polymerization by irradiating active energy rays such as radiation, electron beams, and ultraviolet rays may be employed. Among these, a solution polymerization method using a thermal polymerization initiator or a bulk polymerization method using a photopolymerization initiator is more preferable because the molecular weight can be easily adjusted and impurities can be reduced.

  In one embodiment of the pressure-sensitive adhesive composition of the present invention, the copolymer (a-3) comprises the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group-containing (meth) acrylic monomer (a-2). And polymerized by solution polymerization of a reaction solution containing. As a solution polymerization method using a thermal polymerization initiator, for example, using ethyl acetate, toluene, methyl ethyl ketone or the like as a solvent, thermal polymerization is performed with respect to 100 parts by mass of the total amount of raw material monomers of the copolymer (a-3). Preferably, 0.01 parts by weight or more and 1 part by weight or less of an initiator is added, and the reaction temperature is 40 ° C. or higher and 90 ° C. or lower (or 60 ° C. or higher and 90 ° C. or lower), for example, for 3 hours or longer and 10 hours or shorter. The method of making it react is mentioned.

  Examples of the thermal polymerization initiator include 2,2-azobisisobutyronitrile (AIBN), 2,2′-azobis (2-methylbutyronitrile), azobiscyanovaleric acid, 2,2′-azobis ( 4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2.4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 2,2'- Azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2 '-Azobis (N-butyl-2-methylpropionamide), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'- Zobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl)- 2-Methylpropionamidine] hydrate, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) Azo compounds such as dihydrochloride, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide]; tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butyl peroxy 2-ethylhexanoate, di-tert-butyl peroxide, Organic peroxides such as menhydroperoxide, benzoyl peroxide, and tert-butyl hydroperoxide; inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate. These thermal polymerization initiators can be used alone or in combination of two or more. According to this method, the main agent (A) comprising the copolymer (a-3) can be obtained (form (3) above). Moreover, by adding the obtained copolymer (a-3) to the component (a-1) and the component (a-2), the component (a-1), the component (a-2) and the copolymer The main agent (A) (polymer syrup) comprising the union (a-3) can also be obtained (form (2) above).

  The bulk polymerization method using the photopolymerization initiator is not particularly limited. For example, the raw material monomer of the copolymer (a-3) and the photopolymerization initiator are added, and the reaction start temperature is adjusted in a nitrogen atmosphere. Irradiation with active energy rays is performed at 20 ° C. or higher and 35 ° C. or lower. A method of obtaining a copolymer (a-3) by stopping the reaction by introducing air into the reaction system at a stage where the temperature in the reaction system has risen by 5 ° C. or more and 15 ° C. or less from the reaction start temperature. Can be mentioned. At this time, it is not necessary to react all the raw material monomers to be used, and the reaction may be stopped when the desired weight average molecular weight is reached. Since the (a-1) component, the (a-2) component, and the (a ′) component added as necessary are unreacted raw material monomers, the solvent is dissolved in the copolymer (a-3). According to the method, the main component (A) (polymer syrup) containing the component (a-1), the component (a-2) and the copolymer (a-3) can be obtained (form (2) above). .

Examples of active energy rays used in the bulk polymerization method include, for example, ultraviolet rays, laser rays, α rays, β rays, γ rays, X rays, electron rays, etc., but good controllability and handling properties, cost From this point, ultraviolet rays are preferably used. That is, in a preferred embodiment of the pressure-sensitive adhesive composition of the present invention, the copolymer (a-3) contains the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group-containing (meth) acrylic monomer ( a-2) is polymerized by ultraviolet irradiation of the reaction solution. More preferably, ultraviolet rays having a wavelength of 200 nm to 400 nm are used. Ultraviolet rays can be irradiated using a light source such as a high-pressure mercury lamp, a microwave excitation lamp, a chemical lamp, or a black light. The illuminance is preferably 3.2 mW / cm ² or more and 5.6 mW / cm ² or less.

  Examples of photopolymerization initiators include acetophenone, 3-methylacetophenone, benzyldimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1- (4-isopropylphenyl) -2-hydroxy- 2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, etc. Benzophenones such as benzophenone, 4-chlorobenzophenone and 4,4′-diaminobenzophenone; benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; 1-hydroxy Cyclohexylphenylke Down, a xanthone, fluorenone, camphor quinone, benzaldehyde, anthraquinone, and the like. These photopolymerization initiators can be used alone or in admixture of two or more.

  Commercially available photopolymerization initiators may be used. Examples of commercially available products include Irgacure (registered trademark) 184, 819, 907, 651, 1700, 1800, 819, 369, 261, Darocur (registered trademark) TPO. , Darocur (registered trademark) 1173 (above, manufactured by BASF Japan Ltd.), Ezacure (registered trademark) KIP150, TZT (above, manufactured by DKSH Japan Ltd.), Kayacure (registered trademark) BMS, DMBI (above, Nippon Kayaku Co. Company-made).

  The amount of the photopolymerization initiator used is preferably 0.0005 parts by mass or more and 1 part by mass or less, more preferably 0.002 parts by mass with respect to 100 parts by mass of the total amount of raw material monomers of the copolymer (a-3). Part to 0.5 parts by weight.

  Moreover, a chain transfer agent can also be used in order to adjust molecular weight in the synthesis | combination of a copolymer (a-3). For example, methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, lauryl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid and its ester, 2-ethylhexylthioglycol, thioglycol Mercaptans such as octyl acid; alcohols such as methanol, ethanol, propanol, n-butanol, isopropanol, t-butanol, hexanol, benzyl alcohol, and allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane, and trichloroethylene; acetone , Methyl ethyl ketone, cyclohexanone, acetophenone, acetaldehyde, propionaldehyde n- butyraldehyde, furfural, carbonyls, such as benzaldehyde; methyl-4-cyclohexene-1,2-dicarboxylic acid anhydride, such as α- methyl styrene. These may be used alone or in combination of two or more.

  In the present invention, the weight average molecular weight (Mw) of the copolymer (a-3) is preferably from 1 million to 2.5 million, and more preferably from 1.2 million to 1.9 million. When the weight average molecular weight is 1,000,000 or more, it is excellent in suppressing the occurrence of durability and peeling / lifting, and the adhesiveness is improved. Moreover, if it is 2.5 million or less, the viscosity of a copolymer solution will become moderate and workability | operativity, such as coating property, will improve.

[Pentaerythritol Compound (B)]
The adhesive composition concerning this invention contains a pentaerythritol compound (B) in the ratio of more than 0 mass part and 0.05 mass part or less with respect to 100 mass parts base agent (A). Thereby, folding resistance can be improved, preventing that adhesive force and durability fall.

  The “pentaerythritol compound (B)” (hereinafter also simply referred to as “component (B)”) in the present invention has a pentaerythritol skeleton and a group having an ethylenically unsaturated double bond in the molecule (ethylene A compound having at least one ionic unsaturated group). Specific examples of such an ethylenically unsaturated group include a vinyl group, an allyl group, a (meth) acryloyl group, and a propenyl group.

  The component (B) is typically represented by the following formula (5):

Here, in the above formula (5), R ₂₁ , R ₂₂ , R ₂₃ and R ₂₄ each independently represent a hydrogen atom or an ethylenically unsaturated group; at least one of R ₂₁ , R ₂₂ , R ₂₃ and R ₂₄ One is an ethylenically unsaturated group; Y ₁ , Y ₂ , Y ₃ and Y ₄ are each independently a single bond or an alkylene oxide group having 1 to 20 carbon atoms and having 1 to 20 repeating units. N represents an integer of 1 or more and 6 or less.

  In the formula (5), the ethylenically unsaturated group is preferably a (meth) acryloyl group.

From the viewpoint of durability and resistance to folding, in the formula (5), it is preferable that 2 or more and 3 or less groups of R ₂₁ , R ₂₂ , R ₂₃ and R ₂₄ are ethylenically unsaturated groups.

More specifically, the alkylene oxide group having 1 to 6 carbon atoms is a methylene oxide group, an ethylene oxide group, a propylene oxide group, a butylene oxide group, a pentylene oxaside group, or a hexylene oxide group. Preferably, Y ₁ , Y ₂ , Y ₃ and Y ₄ are each independently a single bond or an alkylene oxide group having 1 to 3 carbon atoms and having 1 to 3 carbon atoms (that is, — (CH ₂ O ) _M -,-(CH ₂ OCH ₂ O) _m- , or-(CH ₂ OCH ₂ OCH ₂ O) _m- , where m is an integer of 1 to 12, and more preferably a single bond. .

  From the viewpoint of availability, in formula (5), n is preferably an integer of 1 or more and 3 or less, more preferably 1 or 2.

  The component (B) can be used alone or in combination of two or more. In addition, as the component (B), a commercially available product or a synthetic product may be used.

  Specific examples of the component (B) include pentaerythritol mono (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipentaerythritol penta (meth) acrylate. Dipentaerythritol hexa (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, and the like are preferable. Among these, from the viewpoint of folding resistance, the component (B) is preferably pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, or dipentaerythritol hexa (meth) acrylate.

  Moreover, as a commercial item of (B) component, A-TMM-3, A-TMM-3L, A-TMM-3LM-N, ATM-35E, A-TMMT, A-9550, A-DPH (above, Shin-Nakamura Chemical Co., Ltd.), PETIA, PETRA, EBECRYL (registered trademark) 40, EBECRYL (registered trademark) 180, DPHA (above, Daicel Ornex Co., Ltd.), Light Acrylate (registered trademark) PE-3A, Light Acrylate ( Examples include registered trademark PE-4A, light acrylate (registered trademark) DPE-6A (above, Kyoeisha Chemical Co., Ltd.), Miramer M340, Miramer M4004, Miramer M600 (above, Toyo Chemicals Co., Ltd.), and the like.

  Content in the adhesive composition of the said pentaerythritol compound (B) is a ratio of more than 0 mass part and 0.05 mass part or less with respect to 100 mass parts main ingredient (A). In the pressure-sensitive adhesive composition not containing the pentaerythritol compound (B), it becomes difficult to achieve sufficient durability and folding resistance. On the other hand, when the content of the pentaerythritol compound (B) in the composition exceeds 0.05 parts by mass, even if the glass transition temperature after curing of the pressure-sensitive adhesive composition is −70 ° C. or higher and −60 ° C. or lower, Satisfaction is not obtained in durability and folding resistance at a low temperature (for example, -20 ° C). The content of the pentaerythritol compound (B) in the pressure-sensitive adhesive composition is preferably 0.0005 parts by mass or more and 0.05 parts by mass or less, more preferably 100 parts by mass of the main agent (A). Is 0.005 parts by mass or more and 0.04 parts by mass or less. In addition, when using 2 or more types of compounds as a pentaerythritol compound (B), content in said adhesive composition of said pentaerythritol compound (B) is a total amount of 2 or more types of compounds.

[Photoinitiator (C)]
In another preferred embodiment of the present invention, the pressure-sensitive adhesive composition further contains 0.1 to 5 parts by mass of the photopolymerization initiator (C) with respect to 100 parts by mass of the main agent (A). Thereby, when the main agent (A) is in the form of a polymer syrup, the final copolymerization reaction is performed to facilitate the formation of the pressure-sensitive adhesive layer. As such a photoinitiator (C), what was mentioned above in manufacture of a copolymer (a-3) is employable. The addition amount when adding these polymerization initiators is more preferably 0.2 parts by mass or more and 2 parts by mass or less.

[Silane coupling agent (D)]
The pressure-sensitive adhesive composition of the present invention can further contain a silane coupling agent from the viewpoint of improving the adhesion to the silicon film.

  A silane coupling agent refers to one having no siloxane bond and having two or more different reactive groups in the molecule.

  The silane coupling agent (D) used in the pressure-sensitive adhesive composition of the present invention is not particularly limited. For example, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n -Propyltrimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane , Vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3- Glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacrylic Roxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β- (aminoethyl) -Γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyl bird Toxisilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis- (3- [triethoxysilyl] propyl) tetrasulfide, γ-isocyanatopropyltriethoxysilane, etc. Can be mentioned. Furthermore, a silane cup containing a silane coupling agent having a functional group such as an epoxy group (glycidoxy group), amino group, mercapto group, (meth) acryloyl group, and a functional group reactive with these functional groups. A compound having a hydrolyzable silyl group obtained by reacting a ring agent, another coupling agent, polyisocyanate, or the like at an arbitrary ratio with respect to each functional group can also be used.

  As the silane coupling agent (D), a commercially available product or a synthetic product may be used. Examples of commercially available silane coupling agents include KBM-303, KBM-403, KBE-402, KBE-403, KBE-502, KBE-503, KBM-5103, KBM-573, KBM-802, and KBM-. 803, KBE-846, KBE-9007 (manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

  The silane coupling agent (D) may be used alone or in combination of two or more.

  When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent (D), the content is preferably 0.0001 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the main agent (A). 0.001 to 5 parts by mass is more preferable, and 0.01 to 3 parts by mass is particularly preferable. If it is such a range, durability can be improved.

[solvent]
The pressure-sensitive adhesive composition of the present invention may contain a solvent. The solvent is not particularly limited, but esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane, Examples thereof include organic solvents such as alicyclic hydrocarbons such as methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone. These solvents can be used alone or in combination of two or more.

  Moreover, as mentioned above, when the copolymer (a-3) is synthesized by a bulk polymerization method using a photopolymerization initiator, the obtained copolymer (a-3) is unreacted (a -1) A form containing at least one of component (a-2) and component (a ′) as a solvent, that is, a so-called polymer syrup. Examples of the solvent used in this polymer syrup include the components (a-1), (a-2) and (a ′) exemplified above. Therefore, the pressure-sensitive adhesive composition of the present invention may contain at least one of the component (a-1), the component (a-2) and the component (a ′) as a solvent in the composition.

[Other additive components]
The above-mentioned pressure-sensitive adhesive composition includes a crosslinking accelerator, an anti-aging agent, a filler, a colorant (such as a pigment or a dye), an ultraviolet absorber, an antioxidant, a chain transfer agent, a plasticizer, a softener, You may contain well-known additive components (other additive components), such as surfactant and antistatic agent, in the range which does not impair the effect of this invention.

[Method for producing pressure-sensitive adhesive composition]
It does not specifically limit as a manufacturing method of the said adhesive composition. For example, when the curable compound in the main agent (A) is in the form of the above (1) consisting only of monomers, the (a-1) component, the (a-2) component, the (B) component, and, if necessary, added (A ') component, a photoinitiator (C), a silane coupling agent (D), a solvent, the other additive component, etc. are mixed and manufactured.

  Polymer syrup containing (a-1) component, (a-2) component and copolymer (a-3) when the curable compound in the main agent (A) is in the form of the above (2) comprising a monomer and a polymer , (B) component, and (a ') component added as needed, a photoinitiator (C), a silane coupling agent (D), a solvent, the other additive component, etc. Can be mentioned.

  When the curable compound in the main agent (A) is in the form of the above (3) consisting only of a polymer, the copolymer (a-3) or a solution thereof, the component (B), and photopolymerization start that is added as necessary The method of mixing and manufacturing an agent (C), a silane coupling agent (D), a solvent, another additive component, etc. is mentioned.

  The method for adding the component (B) according to the present invention is not particularly limited. For example, the component (B) is a curing that constitutes the main component (A) from the component solution (B) prepared by dissolving the component (B) in at least one of the components (a-1) and (a-2). You may adjust and add so that it may become a desired content with respect to the whole quantity of an ionic compound.

[Adhesive layer]
One form of the present invention provides a pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive layer of the present invention is a cured layer of the pressure-sensitive adhesive composition of the present invention, and after applying (for example, applying) the pressure-sensitive adhesive composition (solution) of the present invention to an appropriate substrate (support), It can be formed by appropriately applying a curing treatment. When performing 2 or more types of hardening processes (drying, bridge | crosslinking, superposition | polymerization, etc.), these can be performed simultaneously or in multiple steps. In the pressure-sensitive adhesive composition in which the main agent (A) includes a monomer of the component (a-1) or the component (a-2), typically, a final copolymerization reaction is performed as the curing treatment. ((A-1) component, (a-2) component, and / or copolymer (a-3, and (a ′) component added if necessary)) are subjected to a copolymerization reaction to be a completely polymerized product Form). For example, if an active energy ray-curable pressure-sensitive adhesive composition is used, active energy ray irradiation is performed. If necessary, curing treatment such as cross-linking and drying may be performed. When it is necessary to dry with an active energy ray-curable pressure-sensitive adhesive composition, active energy ray curing may be performed after drying. In the pressure-sensitive adhesive composition in which the main agent (A) is composed only of the copolymer (a-3), typically, as the curing treatment, treatments such as drying (heat drying) and crosslinking are performed as necessary. To be implemented.

  In applying the pressure-sensitive adhesive composition, one or more kinds of solvents may be added as appropriate.

  As a base material for the pressure-sensitive adhesive layer, a separator described later can be used.

  The application method is not particularly limited, and various known methods are used. For example, roll coat, baker type applicator, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples thereof include an extrusion coating method.

  When the pressure-sensitive adhesive composition of the present invention contains a solvent, it is preferable to dry the solvent. As a method for drying the solvent, an appropriate method can be adopted depending on the purpose. Preferably, a method of heating and drying the coating film is used. The heat drying temperature is preferably 40 ° C. or higher and 200 ° C. or lower, more preferably 50 ° C. or higher and 180 ° C. or lower, and particularly preferably 70 ° C. or higher and 170 ° C. or lower. By setting the heating temperature in the above range, an adhesive layer having excellent adhesive properties can be obtained. When the main agent (A) is in the form of (3) above comprising the copolymer (a-3) (the form in which the curable compound is composed solely of a polymer), the pressure-sensitive adhesive composition is cured by the drying treatment as described above. be able to.

  The drying time can be set as appropriate. It is preferably between 5 seconds and 30 minutes, more preferably between 5 seconds and 20 minutes, and particularly preferably between 10 seconds and 15 minutes. Heat drying can be performed twice or more under different conditions. For example, after drying at 40 ° C. or more and less than 100 ° C. for 0.1 minute or more and 10 minutes or less, additional drying treatment may be performed at 100 ° C. or more and 200 ° C. or less for 1 minute or more and 20 minutes or less. As a result, it is possible to prevent peeling, floating, and cracking due to rapid volatilization of the solvent.

When the pressure-sensitive adhesive composition of the present invention contains a photopolymerization initiator, the pressure-sensitive adhesive composition of the present invention is applied directly on the adherend or on a predetermined substrate such as a substrate or a separator. After coating, or after coating on one side of the support (base material), an adhesive layer can be obtained by irradiating active energy rays. Typically, the adhesive by illuminance in the following 400nm or more wavelength 200nm is an ultraviolet is 200 mW / cm ² or less 1 mW / cm ² or more, by irradiating the extent 200 mJ / cm ² or more 10000 mJ / cm ² or less integrated light quantity photopolymerizing An agent layer is obtained.

  The thickness (dry film thickness) of the pressure-sensitive adhesive layer of the present invention is not particularly limited and can be appropriately set depending on the intended use. For example, from the viewpoint of adhesiveness and bending resistance, it is preferably 1 μm or more and 200 μm or less, more preferably 5 μm or more and 150 μm or less, and further preferably 10 μm or more and 120 μm or less.

  When the pressure-sensitive adhesive layer according to the present invention is exposed, the pressure-sensitive adhesive layer can be protected with a release-treated sheet (separator) or the like until practical use.

  Examples of the separator include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, Examples thereof include plastic films such as polyurethane films and ethylene-vinyl acetate copolymer films. Other examples include porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and suitable thin leaves such as laminates thereof. However, a plastic film is preferably used because of its excellent surface smoothness.

  The thickness of the separator is usually 5 μm or more and 200 μm or less, preferably about 5 μm or more and 100 μm or less.

  For separators, silicone, fluorine, long-chain alkyl or fatty acid amide release agents, release treatment with silica powder and antifouling treatment, coating type, kneading type, vapor deposition, as required An antistatic treatment such as a mold can be performed. In particular, the release property from the pressure-sensitive adhesive layer can be further improved by appropriately performing a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator.

[Adhesive sheet]
In one form of this invention, an adhesive sheet provided with the adhesive layer formed by hardening | curing the adhesive composition of this invention is also provided. The pressure-sensitive adhesive sheet is a so-called pressure-sensitive adhesive sheet with a substrate (single-sided) provided with the pressure-sensitive adhesive layer fixed on one or both sides of the sheet-like base material (support), that is, without intention to separate the pressure-sensitive adhesive layer from the base material. Or a double-sided pressure-sensitive adhesive sheet), or the pressure-sensitive adhesive layer is provided on a substrate having releasability such as a release film (release liner) (release paper, a resin sheet having a surface subjected to release treatment). A so-called base material-less (double-sided) pressure-sensitive adhesive sheet in which the base material supporting the pressure-sensitive adhesive layer is removed at the time of pasting may be used.

  The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. In addition, the said adhesive layer is not limited to what was formed continuously, For example, the adhesive layer formed in regular or random patterns, such as dot shape and stripe shape, may be sufficient.

  Examples of the substrate (support) include plastic substrates such as polyethylene terephthalate (PET) and polyester film, porous materials such as paper and nonwoven fabric, and metal foil.

  The constituent material of the plastic substrate is not particularly limited as long as it can be formed into a sheet shape or a film shape. For example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1- Polyolefins such as pentene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer; polyethylene terephthalate (PET) And polyesters such as polyethylene naphthalate and polybutylene terephthalate; polyamides such as polyacrylate, polystyrene, nylon 6, nylon 6,6, and partially aromatic polyamide; polyvinyl chloride, polyvinylidene chloride, and polycarbonate.

  Although the thickness in particular of a base material is not restrict | limited, Preferably they are 4 micrometers or more and 100 micrometers or less, More preferably, they are 4 micrometers or more and 50 micrometers or less.

  If necessary, the plastic substrate may be released from a silicone, fluorine, long chain alkyl or fatty acid amide release agent, silica powder, etc., and antifouling treatment, acid treatment, alkali treatment, primer treatment. Further, anti-adhesion treatment such as corona treatment, plasma treatment and ultraviolet treatment, coating type, kneading type, vapor deposition type and the like can be carried out.

  Moreover, the separator illustrated above is mentioned as said release film (release liner).

[Usage]
The above-mentioned pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and pressure-sensitive adhesive sheet of the present invention are applied to various uses, and are used for optical members such as optical films, for example. Such an optical film is not particularly limited, and examples thereof include those used for forming an image display device such as a liquid crystal display device. For example, a film that includes at least a polarizing plate or a retardation plate and further includes at least one of a conductive layer and a protective layer, a cover film, a transparent conductive film, a window film, and a viewing angle widening film for improving the viewing angle of a liquid crystal display Such as an optical compensation film, a brightness enhancement film for increasing the contrast of the display, and a laminate of these films. That is, in one Embodiment of this invention, an optical member provided with the adhesive layer formed by hardening | curing the adhesive composition concerning this invention is provided.

  The pressure-sensitive adhesive composition of the present invention may be used by directly applying to one side or both sides of an optical member to form a pressure-sensitive adhesive layer, or by previously forming a pressure-sensitive adhesive layer on a release film. It may be used by transferring to one side or both sides. Since the pressure-sensitive adhesive composition of the present invention has excellent durability, it is possible to prevent the pressure-sensitive adhesive layer from floating or peeling off due to heat treatment or high-humidity treatment.

  The pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and pressure-sensitive adhesive sheet of the present invention are suitably used for image display devices. Examples of the image display device include a liquid crystal display device, an organic EL display device, a plasma display (PDP), a curved display, a flexible display, and the like.

  As described above, the present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet, and an image display device, and peels off and floats even when bent under high temperature and low temperature conditions. Thus, it is possible to provide a pressure-sensitive adhesive composition having an excellent balance between bending resistance and little bending. The pressure-sensitive adhesive composition of the present invention is suitably used for the production of various films or sheets used for liquid crystal display elements such as flexible displays and electroluminescence elements, and is commercially available in these technical fields. To get.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. In addition, both parts and% in each example are based on mass. The room temperature standing conditions not specifically defined below are all 23 ° C. and 55% RH.

<Viscosity>
The main agent (A) placed in a glass bottle was temperature-controlled at 25 ° C. and measured with a B-type viscometer.

<Measurement of weight average molecular weight of copolymer (a-3)>
The weight average molecular weight of the copolymer (a-3) was measured by GPC (gel permeation chromatography).
・ Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
Column: manufactured by Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
・ Column size: 7.8mmφ × 30cm each 90cm in total
-Column temperature: 40 ° C
・ Flow rate: 0.8ml / min
・ Injection volume: 100 μl
・ Eluent: Tetrahydrofuran ・ Detector: Differential refractometer (RI)
Standard sample: polystyrene.

[Production Example 1]
<Preparation of main agent (A-1)>
The main agent (A-1) was prepared as shown below.

  The reaction was carried out in a reaction box installed on four sides of a flask (FL20SBL, Sankyo Electric Co., Ltd., FL20SBL, emission wavelength 315 nm or more and 400 nm or less) as UV lamps in an environment where external ultraviolet rays were cut.

In a four-necked flask with a capacity of 2 liters equipped with a stirrer, thermometer, nitrogen gas inlet tube and cooling tube in the box, 64 parts by mass of 2-ethylhexyl acrylate (2EHA), 2-ethylhexyl-diglycol acrylate (EDHG- AT) 20 parts by mass, 2-hydroxyethyl acrylate (HEA) 15 parts by mass, polymethyl methacrylate macromonomer (AA-6) 1 part by mass, 2,2-dimethoxy-1,2-diphenylethane as a polymerization initiator -1-one (Irgacure (registered trademark) 651 manufactured by BASF Japan Ltd.) 0.005 part by mass was blended. Then, it heated to 30 degreeC, replacing the air in a flask with nitrogen. Here, in order to start polymerization, light of 4 mW / cm ² was irradiated by a black light. After the start of the reaction, the temperature of the reaction system increased, but when the increase in reaction temperature from the start reached 10 ° C, the reaction was stopped by stopping the irradiation of black light and introducing air into the flask with an air pump. Was forcibly stopped. This obtained the main ingredient (A-1) containing the copolymer (a-3-1) (polymerization rate 8%) in which a part of the monomer component was polymerized. The viscosity of the main agent (A-1) was 1000 mPa · s, and the weight average molecular weight (Mw) of the copolymer (a-3-1) was 1,800,000. The above “polymerization rate” is a value of the reaction rate calculated with 100% being the case where all of the charged monomers are polymers.

[Production Example 2]
<Preparation of main agent (A-2)>
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a condenser, 81.5 parts by mass of 2-ethylhexyl acrylate (2EHA), 15 parts by mass of methoxyethyl acrylate (MEA), 2-hydroxyethyl acrylate (HEA) 0.5 parts by mass, acryloylmorpholine (ACMO) 3 parts by mass, 2,2′-azobisisobutyronitrile 0.1 part by mass as a polymerization initiator together with 100 parts by mass of ethyl acetate, and gently stirred While introducing nitrogen gas, the nitrogen was replaced. Thereafter, a polymerization reaction was carried out for 5 hours while keeping the liquid temperature in the flask at around 55 ° C. After completion of the polymerization reaction, 300 parts by mass of ethyl acetate was added for dilution to obtain a main agent (A-2) containing a copolymer (a-3-2) (polymerization rate 90%, solid content 18% by mass). The viscosity of the main agent (A-2) was 3500 mPa · s, and the weight average molecular weight (Mw) of the copolymer (a-3-2) was 1.4 million.

[Production Example 3]
<Preparation of main agent (A-4)>
In the same manner as in Production Example 2, a 4-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with 80 parts by mass of 2-ethylhexyl acrylate (2EHA), 19 parts by mass of methoxyethyl acrylate (MEA), 4 parts -1 part by weight of hydroxybutyl acrylate (4HBA), 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged with 100 parts by weight of ethyl acetate, and nitrogen gas was introduced while gently stirring. And replaced with nitrogen. Thereafter, a polymerization reaction was carried out for 5 hours while keeping the liquid temperature in the flask at around 55 ° C. Subsequently, while maintaining this temperature, as an additional monomer, 320 parts by mass of 2-ethylhexyl acrylate (2EHA), 76 parts by mass of methoxyethyl acrylate (MEA), 4 parts by mass of 4-hydroxybutyl acrylate (4HBA) were added, and acetic acid was added. By distilling off ethyl, the main agent (A-4) containing the copolymer (a-3-3) (polymerization rate 90%, solid content 18% by mass) was obtained. The viscosity of the main agent (A-4) was 4000 mPa · s, and the weight average molecular weight (Mw) of the copolymer (a-3-3) was 1,500,000.

[Production Examples 4 to 10]
In Production Examples 4 to 10, main agents (A-5) to (A-11) were produced in the same manner as in Production Example 1 except that the type of monomer used for preparing the main agent (A) or the ratio thereof was changed as shown in Table 1. ) Was prepared. Mw (weight average molecular weight) of the copolymers (a-3-4) to (a-3-10) contained in the main agents (A-5) to (A-11) is as shown in Table 1.

  The homopolymer Tg (excluding EHDG-AT and NVP) is a catalog value of each manufacturer. The homopolymer Tg of EHDG-AT and NVP is a value determined by the DSC method according to JIS K7121 (1987).

  In addition, the glass transition temperature of a copolymer (a-3) is a value calculated by the following FOX formula from the monomer unit which comprises each main ingredient, and its ratio.

  The theoretical glass transition temperature obtained from the FOX equation is in good agreement with the measured glass transition temperature obtained by differential scanning calorimetry (DSC), dynamic viscoelasticity, and the like.

[Example 1]
(Preparation of adhesive composition)
Dipentaerythritol hexaacrylate (NK ester (registered trademark) A-DPH manufactured by Shin-Nakamura Chemical Co., Ltd., hereinafter referred to as “A-DPH”) with respect to 100 parts by mass of the main agent (A-1) obtained in Production Example 1. , B-1) 0.04 parts by mass, 2,2-dimethoxy-1,2-diphenylethane-1-one (Irgacure (registered trademark) 651 manufactured by BASF Japan Ltd.) 0.3 parts by mass was added and mixed. -A depolymerization treatment was performed to obtain a photopolymerizable pressure-sensitive adhesive composition.

(Formation of adhesive layer)
Next, this photopolymerizable pressure-sensitive adhesive composition was applied to one side of a release film (silicone-treated polyethylene terephthalate (PET) film having a thickness of 50 μm, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF50) to a coating thickness of 50 μm. It applied so that it might become. By attaching another release film on the coating film, the release film was placed above and below the coating film of the pressure-sensitive adhesive composition and sealed in a sandwich shape. Thereafter, the pressure-sensitive adhesive composition is cured by irradiating with an illuminance of 5 mW / cm ² and an integrated light amount of 1500 mJ / cm ² with a black light (FL20SBL manufactured by Sankyo Electric Co., Ltd., emission wavelength 315 nm to 400 nm or less), and a colorless and transparent pressure-sensitive adhesive layer And an adhesive sheet was obtained.

[Example 2]
(Preparation of adhesive composition)
To 100 parts by mass of the main agent (A-2) obtained in Production Example 2, 0.03 part by mass of A-DPH was added, mixed and defoamed to obtain an adhesive composition.

(Formation of adhesive layer)
Next, this pressure-sensitive adhesive composition was applied to one side of a release film (silicone-treated 50 μm thick polyethylene terephthalate (PET) film, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF50) so that the thickness after drying would be 50 μm. It was applied and dried at 80 ° C. for 3 minutes. Then, it dried at 120 degreeC for 10 minute (s), and the adhesive layer was formed. Thereafter, another release film was attached to the pressure-sensitive adhesive layer in the same manner as in Example 1 to obtain a pressure-sensitive adhesive sheet.

[Example 3]
(Preparation of adhesive composition)
A main component (A-3) comprising 65 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of 2-ethylhexyl-diglycol acrylate and 15 parts by mass of 2-hydroxyethyl acrylate, 0.04 parts by mass of A-DPH and 2,2 -Dimethoxy-1,2-diphenylethane-1-one (Irgacure (registered trademark) 651 manufactured by BASF Japan Ltd.) 0.3 parts by mass, mixed and defoamed, and photopolymerizable pressure-sensitive adhesive composition Got.

(Formation of adhesive layer)
Next, this photopolymerizable pressure-sensitive adhesive composition is applied to a release film (silicone-treated polyethylene terephthalate (PET) film having a thickness of 50 μm, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF50) with a coating thickness of 50 μm. It was applied as follows. By sticking another release film on the coated surface, the release film was placed above and below the coating film of the pressure-sensitive adhesive composition and sealed in a sandwich shape. Thereafter, the pressure-sensitive adhesive composition was cured by irradiating with an illuminance of ² mW / cm ² and an integrated light amount of 7200 mJ / cm ² with a black light (FL20SBL manufactured by Sankyo Electric Co., Ltd., emission wavelength 315 nm to 400 nm or less), and a colorless and transparent pressure-sensitive adhesive layer And an adhesive sheet was obtained.

[Examples 4-7 and Comparative Examples 1-8]
Table of types of main agent (A), types and amounts of pentaerythritol compound (B), types and amounts of photopolymerization initiator (C), types and amounts of silane coupling agent (D) and other additives (E) A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were produced in the same manner as in Example 1 except that it was used as shown in 2.

<Gel fraction>
The gel fraction of the adhesive composition produced in Examples 1-7 and Comparative Examples 1-9 was measured. The gel fraction was measured by the following method. That is, about 0.1 g of the pressure-sensitive adhesive composition was weighed, and the weight W1 (g) was measured. This was collected in a sample bottle, and about 30 g of ethyl acetate was added and left for 24 hours. The contents of the sample bottle after a lapse of a predetermined time are filtered off with a 200 mesh stainless steel wire mesh (the weight of the membrane is W2 (g)), and the wire mesh and the residue are dried at 90 ° C. for 1 hour to obtain an overall weight W3 ( g) was measured. The gel fraction was calculated from these measured values according to the following mathematical formula 2.

<Glass transition temperature after curing pressure-sensitive adhesive composition>
Using the pressure-sensitive adhesive compositions prepared in Examples 1 to 7 and Comparative Examples 1 to 9, the glass transition temperature after curing was measured. That is, the measurement was performed by the DSC method according to JIS K7121 (1987).

<Measurement of storage modulus>
About the adhesive layer produced by each Example and the comparative example, the storage elastic modulus of a measurement range of -30 degreeC or more and 150 degrees C or less is measured using a viscoelasticity measuring apparatus (Anton Paar Japan Co., Ltd. product: model: MCR300). did. More specifically, the produced pressure-sensitive adhesive layer was laminated to a thickness of 400 μm and cut into a size of 8 mm in diameter to obtain a measurement sample. Thereafter, the measurement sample was set on a parallel plate jig and measured in the temperature range of −30 ° C. to 150 ° C. under the conditions of an angular frequency of 1 rad / s, normal force of 3 N, and a temperature increase rate of 5 ° C./min.

<Production of thin polarizing plate>
A polyvinyl alcohol film having a thickness of 20 μm was stretched up to 3 times while being dyed in a 0.3% by mass iodine solution at 30 ° C. between rolls having different speed ratios. Then, the total draw ratio was drawn up to 6 times while being immersed in an aqueous solution containing 60% at 4% by mass boric acid and 10% by mass potassium iodide for 0.5 minutes. Next, after washing by immersing in an aqueous solution containing 1.5% by mass of potassium iodide at 30 ° C. for 10 seconds, drying was performed at 50 ° C. for 4 minutes to obtain a polarizer. On one side of the polarizer, a polycarbonate film with a thickness of 20 μm and a retardation film with a film thickness of 50 μm (¼ wavelength plate, “WRS” manufactured by Teijin Chemicals Ltd.) are bonded with a polyvinyl alcohol adhesive to give a total thickness. A 77 μm thin polarizing plate was produced.

(Preparation of conductive layer and protective layer)
70 parts by mass of ultrapure water (manufactured by Wako Pure Chemical Industries, Ltd., Ultrapure Water Ultrapure Water) per 30 parts by mass of a silver nanowire dispersion solution (manufactured by Cambrios, ClearOhm Ink-A AQ), and a rust inhibitor (Cambrios, US) 0.12 parts by mass of ClearOhm SFT-D (manufactured by Kogyo Co., Ltd.) was added to prepare a conductive layer forming coating material. A conductive layer-forming coating material was applied on the retardation film surface of the thin polarizing plate by a die coating method so that the solid content was 1 g / m ² and dried at 80 ° C. to laminate a conductive layer.

A protective layer-forming coating material was prepared by adding 95 parts by mass of ethyl acetate per 5 parts by mass of acrylic resin-based paint (manufactured by China Paint Co., Ltd., Forseed (registered trademark) No. 420C resin concentration: 50% by weight). On the above conductive layer, a protective layer-forming coating material is applied by a die coating method so that the thickness of the protective layer (thickness after curing) is 210 nm, dried at 80 ° C., and ultraviolet rays (manufactured by Fusion UV Systems Japan) , LH10-70UV lamp) was applied (200 mJ / cm ² ) to cure, and a protective layer was formed.

<Preparation of polarizing plate with adhesive layer>
On the side of the retardation film forming the pressure-sensitive adhesive layer of the polarizing plate, corona treatment was performed with a corona discharge amount of 80 [W · min / m ² ]. Next, the release film was peeled from one side of the pressure-sensitive adhesive sheet to expose the pressure-sensitive adhesive layer, and transferred so that the pressure-sensitive adhesive layer and WRS were in contact with each other. The release film on the side opposite to the polarizing plate was peeled off from the pressure-sensitive adhesive layer to produce a polarizing plate with a pressure-sensitive adhesive layer.

<Durability test>
A polyimide film (thickness 0.7 mm) having a silicon nitride (SiN _x ) film (film thickness 50 nm) on the outermost surface was used as an alternative to the flexible panel.

The polarizing plate sample with an adhesive layer was made into a 5-inch size, and was stuck to the polyimide film using the laminator. Subsequently, the sample was autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to completely adhere the sample to the polyimide film. Thereafter, the sample was sandwiched and fixed with a glass plate so that the inner diameter (diameter) could be maintained at 6 mm. The sample subjected to such treatment was subjected to (1) treatment at 85 ° C. for 500 hours (heating test). (2) Moreover, it processed for 500 hours in 60 degreeC95% RH atmosphere (humidification test). (3) Moreover, after performing 300 cycles in 85 degreeC and -40 degreeC environment in 1 cycle 1 hour (heat shock test). About each test, the external appearance of the polarizing plate and the polyimide film was visually evaluated on the following reference | standard.
○: No change in appearance such as foaming, peeling, floating, or cracking.
Δ: Peeled, foamed, or cracked at the end, but there is no practical problem unless it is a special use.
X: Remarkably peeled off at the end, causing practical problems.

  In the tests (1), (2) and (3), samples were prepared and the tests were performed independently.

<Adhesive strength>
The same samples as those used in the durability test were newly prepared and cut into a width of 25 mm and a length of 100 mm, respectively. The sample was then adhered to the polyimide film by autoclaving at 50 ° C. and 5 atm for 15 minutes. Then, after leaving still at 23 degreeC55% RH atmosphere for 1 hour, the adhesive force was measured.

  The adhesive strength was measured using a tensile tester (Tensilon Universal Material Tester STA-1150 manufactured by Orientec Co., Ltd.) under the conditions of 23 ° C. and relative humidity 55% RH, with a peel angle of 180 ° and a peel rate of 300 mm / It was determined by measuring the adhesive strength (N / 25 mm) when peeling the film in accordance with the method of the adhesive tape and adhesive sheet test of JIS Z0237: 2009 in min.

<Autoclave suitability>
The polarizing plate with an adhesive layer obtained in the above Examples and Comparative Examples was bonded to a glass plate to prepare an evaluation sample. Next, the sample for evaluation was put in an autoclave, and autoclaved for 15 minutes at 50 ° C. and 0.5 MPa. Thereafter, the sample for evaluation taken out from the autoclave was visually observed to check for the presence of bubbles. The evaluation was performed with ◯ when no bubbles were found in the evaluation sample after the autoclave treatment and x when bubbles were found in the evaluation sample after the autoclave treatment.

<Humidification reliability test>
The release film was peeled from one side of the pressure-sensitive adhesive sheet prepared in each Example and Comparative Example, and transferred to a PET film (A4100 manufactured by Toyobo Co., Ltd., 100 μm thick, haze 0.6%). Subsequently, the PET film to which the pressure-sensitive adhesive sheet was transferred was cut into a size of 50 mm wide × 50 mm long, the other release film was peeled off, and the pressure-sensitive adhesive layer surface was attached to a glass plate. This produced the test piece which has a structure of "glass / adhesive layer / PET film".

Using a haze meter (NDH5000W manufactured by Nippon Denshoku Industries Co., Ltd.), the haze of the test piece at 23 ° C. and 55% RH was measured (H ₀ ). Further, the above test specimen was stored for 3 days in an environment of 60 ° C. and 95% RH, and immediately after being taken out in an environment of 23 ° C. and 55% RH, haze (H) after 2 hours after taking out was measured. When the value calculated by {(H−H ₀ ) / H ₀ } × 100 (%) is less than 2%, the evaluation was made as “◯”, and when it was 2% or more, it was evaluated as “×”.

<Metal corrosion inhibition / prevention>
Exfoliation film was exfoliated from one side of the pressure sensitive adhesive sheet produced in Examples and Comparative Examples, transferred to a PET film (A4100 manufactured by Toyobo Co., Ltd., 100 μm thick), and cut into a size of 20 mm wide × 50 mm long test piece (Test piece 11).

  As shown in FIG. 1, both ends of a conductive PET film 12 (manufactured by Nitto Denko Corporation, ELECRYSTA V-150FLC5) (size: length 70 mm × width 25 mm) are fixed with a conductive tape 122, and the conductive surface ( The pressure-sensitive adhesive layer surface of the test piece 11 from which the separator was peeled was bonded to the ITO film forming surface 121 side). This was allowed to stand for 24 hours in an environment of 23 ° C., then left for 7 days in an environment of 60 ° C. and 95% RH, and the “resistance value after standing for 7 days at 60 ° C. and 95% RH” relative to the “resistance value immediately after application” The ratio (%) [(resistance value after leaving at 60 ° C. and 95% RH for 7 days) / (resistance value immediately after pasting) × 100 (%)] was measured. In addition, said resistance value was measured by attaching electrodes to the conductive tape 122 at both ends, using “Multi Tester SR-18D” manufactured by Sanwa Electric Meter Co., Ltd. Moreover, if the ratio of “resistance value after leaving at 60 ° C. and 95% RH for 7 days” to “resistance value immediately after application” is less than 120%, the corrosion resistance is “good (◯)”, and if it is 120% or more, the resistance is It was judged as corrosive "bad (x)". In addition, as a result of performing the same test only with the conductive PET film without sticking the adhesive sheet as a blank, the ratio of “resistance value after being left at 60 ° C. and 95% RH for 7 days” with respect to “resistance value immediately after pasting” is 120%. Was less than.

<Folding resistance>
Conditions were set so that the inner diameter (diameter) of the same sample used in the above durability test was 6 mm when bent with a bending tester (manufactured by Tester Sangyo Co., Ltd.). As a cycle, 100,000 cycles were repeated. The test environment was -20 ° C. and 23 ° C. and 55% RH atmosphere, 85 ° C. and 60 ° C. and 95% RH atmosphere, respectively. The appearance of the polarizing plate and the polyimide film after the test was visually evaluated according to the following criteria.
○: No change in appearance such as foaming, peeling, floating, or cracking.
Δ: Peeled, foamed, or cracked at the end, but there is no practical problem unless it is a special use.
X: Remarkably peeled off at the end, causing practical problems.

11 test pieces,
111 PET film,
112 adhesive sheet,
12 conductive PET film,
121 conductive PET film (ITO film forming surface),
122 Conductive tape.

Claims (11)

100 parts by mass of the main agent (A) comprising a curable compound; and
Containing the pentaerythritol compound (B) in an amount of more than 0 parts by mass and 0.05 parts by mass or less,
The main agent (A) is a combination of a (meth) acrylic acid ester monomer (a-1) and a hydroxyl group-containing (meth) acrylic monomer (a-2), and the (meth) acrylic acid ester monomer (a-1). Comprising at least one of the copolymer (a-3) comprising the structural unit (1) derived from the above and the structural unit (2) derived from the hydroxyl group-containing (meth) acrylic monomer (a-2),
The adhesive composition whose glass transition temperature after hardening is -70 degreeC or more and -60 degrees C or less.   The pressure-sensitive adhesive composition according to claim 1, wherein the content of the hydroxyl group-containing (meth) acrylic monomer (a-2) is 0.1% by mass or more and 30% by mass or less based on the total amount of the main agent (A). object.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the content of the (meth) acrylic acid ester monomer (a-1) is 70% by mass or more based on the total amount of the main agent (A).   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the content of the copolymer (a-3) is 5% by mass or more and 25% by mass or less based on the total amount of the main agent (A). object.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the copolymer (a-3) has a weight average molecular weight of 1 million to 2.5 million.   The copolymer (a-3) is polymerized by ultraviolet irradiation of a reaction solution containing the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group-containing (meth) acrylic monomer (a-2). The pressure-sensitive adhesive composition according to any one of claims 1 to 5.   The copolymer (a-3) is polymerized by solution polymerization of a reaction solution containing the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group-containing (meth) acrylic monomer (a-2). The pressure-sensitive adhesive composition according to any one of claims 1 to 5.   The pressure-sensitive adhesive composition according to any one of claims 1 to 7, further comprising 0.1 to 5 parts by mass of a photopolymerization initiator (C).   The (meth) acrylic acid ester monomer (a-1) is one or more selected from the group consisting of 2-ethylhexyl (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate and ethoxy-diethylene glycol (meth) acrylate The pressure-sensitive adhesive composition according to any one of claims 1 to 8, wherein   An optical member provided with the adhesive layer formed by hardening | curing the adhesive composition of any one of Claims 1-9.   An adhesive sheet provided with the adhesive layer formed by hardening | curing the adhesive composition of any one of Claims 1-9.