JP6767112B2 - Adhesive composition and adhesive sheet - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition suitable for use in a flexible device, and a pressure-sensitive adhesive sheet for a display provided with a pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition. More specifically, the present invention relates to an adhesive composition for an optical film, an adhesive layer for an optical film obtained by curing the adhesive composition, and an adhesive sheet for a display (adhesive optical film) provided with the adhesive layer. The present invention relates to an adhesive composition which does not cause peeling or floating even when a bending operation is performed to deform an optical film obtained by laminating the obtained laminate under each durability test condition. The pressure-sensitive adhesive composition of the present invention is suitably used for laminating thin-layer adherends including optical films or sheets, and various films or sheets used for liquid crystal display elements such as flexible displays, electroluminescence elements, and the like. It is suitably used for the production of, and can be commercialized in these technical fields.

Currently, as display panels, flat display panels such as liquid crystal display panels (LCD) and plasma display panels (PDP) are mainly used. A laminated body in which a plurality of films are laminated is usually bonded to the surface of a flat display panel. For example, in an LCD, an optical film such as a polarizing plate, a retardation plate, a viewing angle expanding film, and a brightness improving film is usually laminated on the surface of a liquid crystal panel. Each layer constituting the flat display panel is usually bonded by an adhesive layer formed of various adhesives.

On the other hand, recently, in addition to flat displays, flexible displays including curved displays have been developed from the viewpoints of design and versatility of usage, and display panels are required to have flexibility. Organic electroluminescence panels (OLEDs) are mainly used in flexible displays such as curved displays.

The optical film used for flexible displays such as curved displays and the optical film laminate laminated by the adhesive layer or the adhesive layer have, in addition to the optical properties and durability required for a conventional flat display panel, Therefore, it is required that peeling and floating do not occur even if the optical film is bent to be deformed.

As a pressure-sensitive adhesive layer used in a conventional optical film laminate for a flat display panel, Patent Document 1 describes a pressure-sensitive adhesive composition containing an acrylic acid ester-based polymer, an acrylic-based cross-linking monomer, and a cross-linking initiator. Adhesive sheets made by cross-linking the above have been proposed. Patent Document 2 proposes a photopolymerizable pressure-sensitive adhesive composition containing an acrylic syrup containing an alkoxyalkyl (meth) acrylate monomer, a monomer having two or more polymerizable unsaturated groups, a cross-linking agent, and a photopolymerization initiator. ing. Patent Document 3 proposes a pressure-sensitive adhesive composition for an optical member containing a base polymer and a lactone-modified tris [(meth) acryloxyalkyl] isocyanurate. Patent Document 4 proposes an optical resin composition containing an acrylic acid-based derivative, an acrylic acid-based derivative polymer, and a cross-linking agent.

Japanese Unexamined Patent Publication No. 2014-025073 JP-A-2007-161909 Japanese Unexamined Patent Publication No. 2011-225704 Japanese Unexamined Patent Publication No. 2010-1449

Flexible displays such as organic electroluminescence panels (OLEDs) are expected to be used in a variety of environments, so they are durable for use in a wide range of temperatures and can withstand folding under both high and low temperature conditions. Bending resistance) is required. However, in the pressure-sensitive adhesive described in Patent Document 1, due to the cross-linked structure of the acrylic cross-linked monomer, when the pressure-sensitive adhesive is used for the pressure-sensitive adhesive layer of a flexible display, it is durable and under both high temperature and low temperature conditions. Peeling occurs in the bending operation at high temperature in the folding test. Even the adhesive described in Patent Document 2 cannot satisfy the folding test under both high temperature and low temperature conditions, and peels off and floats. Further, when the polymerization initiators described in Patent Documents 1 and 2 are used, problems of outgas generation and odor occur. Even with the adhesives described in Patent Documents 3 and 4, there arises a problem that the folding test under both high temperature and low temperature conditions cannot be satisfied, peeling and floating occur, and the durability at the time of bending cannot be satisfied.

Therefore, the present invention has been made in view of the above circumstances, and even if the bending operation is performed under both high temperature and low temperature conditions, peeling and floating do not occur, and an adhesive capable of suppressing the generation of offensive odor and outgas. It is an object of the present invention to provide an agent composition.

As a result of diligent research to solve the above problems, the present inventors have included a main agent (A) composed of a curable compound containing a predetermined acrylic compound and a predetermined photopolymerization initiator (B). Moreover, it has been found that the above-mentioned problems can be solved by the pressure-sensitive adhesive composition having a glass transition temperature of −57.5 ° C. or lower after curing, and the present invention has been completed.

According to the present invention, under various durability test conditions, even if the bonded film is bent under both high and low temperature conditions, peeling and floating do not occur, and the film can be folded under both high and low temperature conditions. It is possible to provide a pressure-sensitive adhesive composition having excellent resistance and capable of suppressing the generation of offensive odor and outgas. The pressure-sensitive adhesive composition according to the present invention is particularly suitable for flexible display applications.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

In the present specification, unless otherwise specified, operations and physical properties are measured under the conditions of room temperature (20 ° C. or higher and 25 ° C. or lower) / relative humidity of 40% RH or more and 50% RH or less.

[Adhesive composition]
One aspect of the present invention includes a main agent (A) and a photopolymerization initiator (B) composed of a curable compound, wherein the main agent (A) is (i) (meth) acrylic acid ester monomer (a-1) and A combination of hydroxyl group-containing (meth) acrylic monomers (a-2), or (ii) said (meth) acrylic acid ester monomer (a-1), said hydroxyl group-containing (meth) acrylic monomer (a-2), and A copolymer containing a structural unit (1) derived from the (meth) acrylic acid ester monomer (a-1) and a structural unit (2) derived from the hydroxyl group-containing (meth) acrylic monomer (a-2). The photopolymerization initiator (B) contains the combination of (a-3), and the photopolymerization initiator (B) is oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) and 2-hirodoxy-. It is at least one of 1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane-1-one, and has a glass transition temperature of -57 after curing. A pressure-sensitive adhesive composition having a temperature of 5.5 ° C. or lower. According to the present invention, under various durability test conditions, even if the bonded film is bent under both high and low temperature conditions, peeling and floating do not occur, and the film can be folded under both high and low temperature conditions. It is possible to provide a pressure-sensitive adhesive composition having excellent resistance and capable of suppressing the generation of offensive odor and outgas.

The details of why the above-mentioned effect can be obtained by the pressure-sensitive adhesive composition of the present invention are unknown, but it is considered as follows. That is, if the glass transition temperature of the pressure-sensitive adhesive composition after curing is too high (higher than −57.5 ° C.), the cured product cannot be sufficiently flexible at a low temperature (for example, −20 ° C.), and the temperature is low. It becomes difficult to obtain folding resistance in (see Comparative Example 3). On the other hand, the present inventors have a (meth) acrylic acid ester monomer (a-1) having a low glass transition temperature of a homopolymer (or a copolymer (a-3) containing a structural unit derived from the monomer). By adjusting and controlling the glass transition temperature of the pressure-sensitive adhesive composition after curing to −57.5 ° C. or lower by using a curable compound containing (A) as the main agent (A), high temperature (for example, 80 ° C.) and low temperature (for example, 80 ° C.) , -20 ° C), found to improve folding resistance at both.

Further, although the detailed reason is unknown, the main agent (A) composed of a curable compound containing a predetermined acrylic compound is combined with a predetermined photopolymerization initiator (B), and the glass after curing of the pressure-sensitive adhesive composition. By lowering the transition temperature as in the above range, the weight loss rate of the pressure-sensitive adhesive composition under high temperature can be reduced (the folding resistance can be improved, and the generation of offensive odor and outgas can be effectively suppressed). The present inventors have found. This is because when the molecular composition of the photopolymerization initiator is Irgacure 184 (see Comparative Example 1), which has a lower molecular weight than the photopolymerization initiator (B), the glass transition temperature after curing of the pressure-sensitive adhesive composition. By combining the main agent (A) composed of a curable compound containing a predetermined acrylic compound which can be lowered as in the above range, the folding resistance at high temperature and low temperature can be improved, but the residual photopolymerization initiator is a gas. There was a problem that it became a strange odor and outgas. Further, when Ezacure KIP160 (see Comparative Example 2) having a molecular structure similar to that of the photopolymerization initiator (B) and having a molecular structure similar to that of the photopolymerization initiator (B) is used, the molecular composition of the photopolymerization initiator is such that an offensive odor or outgas is generated. Although the occurrence can be suppressed, there is a problem that the folding resistance at a high temperature (for example, 80 ° C.) cannot be sufficiently obtained due to its molecular structure. In the pressure-sensitive adhesive composition of the present invention, the main agent (A) composed of a curable compound containing a predetermined acrylic compound whose glass transition temperature after curing of the pressure-sensitive adhesive composition can be lowered as in the above range is subjected to a predetermined light. It is considered that when combined with the polymerization initiator (B), the molecular structure of the predetermined photopolymerization initiator (B) can suppress the generation of offensive odors and outgas, and also improve the folding resistance at high and low temperatures. Be done. Further, it is considered that the storage elastic modulus at a high temperature (for example, 80 ° C.) can be improved due to the molecular structure of the photopolymerization initiator.

Further, in the pressure-sensitive adhesive composition of the present invention, a curable property containing a highly polar hydroxyl group-containing (meth) acrylic monomer (a-2) (or a copolymer (a-3) containing a structural unit derived from the same). The requirement is to use the compound as the main agent. By adopting such a configuration, it is considered that the adhesive strength and durability can be ensured probably due to the high polarity of the hydroxyl group-containing (meth) acrylic monomer (a-2). Further, a hydroxyl group-containing (meth) acrylic monomer (a-2) (or a copolymer (a-3) containing a structural unit derived from the monomer) can improve folding resistance and can be used at high temperatures. It is considered that the weight reduction rate of the pressure-sensitive adhesive composition can be reduced and the generation of offensive odor and outgas can be effectively suppressed.

The above mechanism is speculative, and the present invention is not limited to the above mechanism.

The glass transition temperature (Tg) of the pressure-sensitive adhesive composition of the present invention after curing may be −57.5 ° C. or lower, but from the viewpoint of folding resistance at low temperatures, it may be −59.0 ° C. or lower. preferable. The lower limit of the glass transition temperature (Tg) after curing of the pressure-sensitive adhesive composition is not particularly limited, and is included in the technical scope of the present invention when the effects of the present invention can be effectively exhibited. is there. The glass transition temperature of the pressure-sensitive adhesive composition after curing can be determined by the method described in Examples. In order to keep the glass transition temperature after curing of the pressure-sensitive adhesive composition in 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 a homopolymer and a monomer (for example, a hydroxyl group-containing (meth) acrylic monomer (a-2) having a relatively high glass transition temperature of a homopolymer). ), And the composition ratio of the component (a-1) and the component (a-2) and the copolymerizable monomer (a')) may be appropriately adjusted.

From the viewpoint of bending resistance at high temperatures, the pressure-sensitive adhesive composition of the present invention preferably has a storage elastic modulus G'(80) at 80 ° C. of the cured pressure-sensitive adhesive composition of 2.0 × 10 ⁴ Pa or more. The upper limit of the storage elastic modulus G'(80) is not particularly limited, and is included in the technical scope of the present invention when the effect of the present invention can be effectively exhibited.

From the viewpoint of bending resistance at low temperatures, the pressure-sensitive adhesive composition of the present invention preferably has a storage elastic modulus G'(-20) at −20 ° C. of the cured pressure-sensitive adhesive composition of 3.5 × 10 ⁵ Pa or less. , 2.5 × 10 ⁵ Pa or less, more preferably. The lower limit of the storage elastic modulus G'(-20) is not particularly limited, and is included in the technical scope of the present invention when the effect of the present invention can be effectively exhibited.

As the storage elastic modulus G'(80) and G'(-20), the values measured by the method described in the examples are adopted. The storage elastic moduli G'(80) and G'(-20) can be controlled by the composition of the main agent (A) and the like.

In the pressure-sensitive adhesive composition of the present invention, the shear strain under 90 kPa shear stress after curing is 800% or more from the viewpoint of preventing cracks in the display element and peeling of the pressure-sensitive adhesive layer when the display is bent. Is more preferable, 900% or more is more preferable, and 1000% or more is further preferable. Within this range, the bending resistance is excellent. For the shear strain, a value measured by the method described in the examples is adopted. The shear strain is added to the composition of the main agent (A), the composition of the copolymer (a-3) that can be contained in the main agent (A), the amount of the photopolymerization initiator (B) added, and if necessary. It can be controlled by the type and amount of the cross-linking agent and the silane coupling agent to be added. The upper limit of the shear strain is not particularly limited, and is included in the technical scope of the present invention when the effect of the present invention can be effectively exhibited.

The gel fraction of the pressure-sensitive adhesive composition of the present invention is preferably 50% or more and 90% or less, more preferably 50% or more and 85% or less, and further preferably 50% or more and 70% or less. No. Within such a range, punching and slitting can be performed quickly as an optical member provided with an adhesive layer. As the gel fraction of the pressure-sensitive adhesive composition, a value measured by the method described in Examples is adopted. In order to set the gel fraction as described above, conditions may be appropriately selected, such as adjusting the addition amount of each component within the above range.

The weight loss rate of the pressure-sensitive adhesive composition of the present invention is preferably less than 1.0%, more preferably 0.9% or less, further preferably 0.8% or less, and 0. It is particularly preferably 6% or less. Within such a range, it is possible to effectively suppress the generation of offensive odor and outgas when the pressure-sensitive adhesive composition is exposed to a high temperature (heating) environment in the manufacturing process of a display or the like. As the weight loss rate of the pressure-sensitive adhesive composition, a value measured by the method described in Examples is adopted. In order to set the weight reduction rate as described above, conditions may be appropriately selected, such as adjusting the addition amount of each component within the above range. The lower limit of the weight loss rate is not particularly limited, and is included in the technical scope of the present invention when the effects of the present invention can be effectively exhibited.

In the pressure-sensitive adhesive composition of the present invention, the adhesive strength of the pressure-sensitive adhesive composition (adhesive layer) after curing is preferably 350 g / 25 mm or more, more preferably 550 g / 25 mm or more, and 750 g / 25 mm. The above is more preferable, and 800 g / 25 mm or more is particularly preferable. Within such a range, excellent adhesive strength can be exhibited to an optical film or the like. For the adhesive strength of the pressure-sensitive adhesive composition (adhesive layer) after curing, a value measured by the method described in Examples is adopted. In order to set the adhesive strength of the adhesive composition (adhesive layer) after curing as described above, conditions may be appropriately selected such as adjusting the addition amount of each component within the above range. The upper limit of the adhesive force is not particularly limited, and is included in the technical scope of the present invention when the effect of the present invention can be effectively exhibited.

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

In the present specification, "(meth) acrylic acid ester monomer" is a general term for an acrylic acid ester monomer and a methacrylic acid ester monomer. Similarly, compounds containing (meth) such as (meth) acrylic acid are a general term for compounds having "meth" in the name and compounds having no "meth". For this reason, "(meth) acrylic" includes both acrylic and methacrylic. The "(meth) acrylic acid ester monomer" includes both an acrylic acid ester monomer and a methacrylic acid ester monomer. "(Meta) acrylic acid" includes both acrylic acid and methacrylic acid.

In the present specification, the "adhesive composition" is also simply referred to as "adhesive". Further, in the present specification, "(co) polymer" is a general term for "polymer (homopolymer)" and "copolymer".

[Main agent (A)]
The main agent (A) used in the present invention is made of a curable compound. In the present invention, (i) (meth) acrylic acid ester monomer (a-1) (hereinafter, also simply referred to as “(a-1) component”) and a hydroxyl group-containing (meth) are contained as constituent components of the main agent (A). ) Acrylic monomer (a-2) (hereinafter, also simply referred to as "(a-2) component"), or (ii) said (a-1) component, said (a-2) component, and said (a). -1) A combination of a copolymer (a-3) containing a structural unit (1) derived from the component and a structural unit (2) derived from the component (a-2) is included. The main agent (A) contains a copolymer (a-3) containing a constituent unit (1) derived from a component (a-1) and / or a 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 −57.5 ° C. or lower. Further, the main agent (A) contains a copolymer (a-3) containing a highly polar component (a-2) and / or a structural unit (2) derived from the component (a-2), so that the main agent (A) has a high polarity. It is possible to secure excellent adhesiveness to an optical film such as a polarizing plate. In addition to the above, the curable compound contained in the main agent (A) includes an active energy ray-curable monomer such as a (meth) acrylic compound and its (co) polymer, and a (meth) acryloyl group, a vinyl group, and an allyl group. , Propenyl group, dithiocarbamate group, diazo group, cinnamylidene group and / or polyester resin containing polymerizable functional groups such as cinnamoyl group, polyether resin, polyurethane resin, epoxy resin and the like, and combinations thereof can be exemplified. Preferably, the curable compound constituting the main agent (A) contains one polymerizable functional group in the molecule.

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

As a preferable form of the main agent (A) composed of the curable compound according to the present invention,
(1) Form containing (a-1) component and (a-2) component (2) A structural unit (1) derived from the (a-1) component, the (a-2) component, and the (a-1) component. ) And the form containing the copolymer (a-3) containing the structural unit (2) derived from the component (a-2) (hereinafter, also simply referred to as the copolymer (a-3)) (the curable compound is a monomer and It is a form composed of a polymer, and examples thereof include a so-called polymer syrup form).

However, the form (3) composed of the copolymer (a-3) (the form in which the curable compound is composed only of the polymer) is not included.

It is considered that the inclusion of such a main agent (A) in the pressure-sensitive adhesive composition of the present invention has significance in ensuring the adhesiveness and basic properties of the pressure-sensitive adhesive layer obtained after curing.

Among them, the curable compound is a copolymer (a-3) from the viewpoints of ease of forming the pressure-sensitive adhesive layer according to the present invention, more efficient performance of the desired effect of the present invention, and the like. It is preferable to include it. That is, the form (2) above (so-called polymer syrup form) is preferable.

<(A-1) (meth) acrylic acid ester monomer>
The (meth) acrylic acid ester monomer (a-1) may be in the form in which an alkyl group or a group represented by − (A—O) _p− Q is introduced into the ester moiety of the (meth) acrylic acid ester. For example, there are no particular restrictions. 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 or more and 20 or less.

A copolymer (a-3) in which the main agent (A) contains a structural unit (1) derived from a (meth) acrylic acid ester monomer (a-1) and / or a (meth) acrylic acid ester monomer (a-1). By including it, the glass transition temperature after curing can be lowered. As a result, bending resistance at low temperatures can be improved without lowering the adhesiveness.

The number of carbon atoms of the alkyl group or the group represented by − (A—O) _p− Q is also 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 40 or less, more preferably 2 or more and 30 or less, further preferably 3 or more and 30 or less, and 4 carbon atoms. It is particularly preferable that it is 28 or more and 28 or less. Further, 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 should be linear or branched. Is preferable. In the case of a ring, the number of carbon atoms is 3 or more.

− (A—O) In the group represented by _p− Q, A has 1 or more and 4 or less carbon atoms from the viewpoint of improving adhesiveness and durability and efficiently exerting 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 has 2 or more and 3 or less carbon atoms (that is, an ethylene group or a propylene group). At this time, p is preferably an integer of 1 or more and 20 or less, more preferably an integer of 1 or more and 15 or less, and further preferably 2 or more and 10 or less. Further, 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 1 or more, from the viewpoint of efficiently exerting the desired effect of the present invention. It is 1 or more and 10 or less, and more preferably 1 or more and 6 or less. Specific examples of such an alkyl group include those listed above.

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

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

The alkyl group in R ₂ of the formula (1) is not particularly limited, and is, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, and an 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, 2-ethylhexyl group, nonyl group, isononyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc. 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 basic properties.

Therefore, specific examples of the (meth) acrylic acid ester monomer (a-1) in which R ₂ of the formula (1) is an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, and 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 thereof include hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and lauryl (meth) acrylate.

In _{R 2} of formula (1) - group represented by _(A-O) p -Q may be an alkoxyalkyl group. As such an alkoxyalkyl group, 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 are preferable.

Specific examples of the (meth) acrylic acid ester monomer (a-1) of the group in which R _{2 of the} formula (1) is represented by − (A—O) _p− Q are methoxyethyl (meth) acrylate and ethoxymethyl. (Meta) 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, 2-ethylhexyl-diglucol (meth) acrylate, methoxy Polyethylene glycol (meth) acrylate and methoxydipropylene glycol (meth) acrylate are preferable.

Among the specific examples of the (meth) acrylic acid ester monomer (a-1) described above, the main agent is particularly from the viewpoint of lowering the glass transition temperature and polarity after curing and ensuring excellent flexibility and adhesiveness. As the (meth) acrylic acid ester monomer (a-1) contained in (A), it is preferable to use a homopolymer having a glass transition temperature of less than -60 ° C., more specifically, 2-ethylhexyl acrylate, 2 Particularly preferably, it is one or more selected from the group consisting of -ethylhexyl-diglucol acrylate, ethoxy-diethylene glycol acrylate, and methoxypolyethylene glycol acrylate.

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

Commercially available products of the component (a-1) include AEH, AME, 2EHA (all manufactured by Nippon Catalyst Co., Ltd.), light acrylate (registered trademark) EC-A, light acrylate (registered trademark) MTG-A, and light acrylate ( EHDG-AT, Light Acrylate (Registered Trademark) 130A, Light Acrylate (Registered Trademark) DPM-A, Light Ester L (all manufactured by Kyoeisha Chemical Co., Ltd.), Viscort # 190, 2-MTA, MPE400A, MPE550A ( As described above, AM-90G, AM-130G (all manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) and the like are suitable.

<(A-2) Hydroxy group-containing (meth) acrylic monomer>
A copolymer (a-3) containing 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), so that the content of the photopolymerization initiator (B) can be suppressed to a certain level, and excellent adhesion to an optical film such as a highly polar polarizing plate can be ensured.

Hydroxy group-containing (meth) acrylic monomers are typically represented by the following formula (2-1):

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

Here, the divalent organic group is not particularly limited, but an alkylene group having 1 or more and 10 or less carbon atoms is preferable. Examples of the alkylene group having 1 or more and 10 or less carbon atoms include those described above. Further, the alkylene group has at least one alkyl group having 1 or more and 8 or less carbon atoms, a phenoxyalkyl group (the number of carbon atoms of the alkyl group: 1 or more and 8 or less carbon atoms), a phenyl group or a cyclohexyl group as a substituent. May be. An 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 equation (2-2),
R ₈ is a hydrogen atom or a methyl group and
R ₉ is a single bond or divalent organic group
R ₁₀ is a hydrogen atom or an alkyl group having 1 or more and 10 or less carbon atoms.

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

Examples of the alkyl group having 1 or more and 10 or less carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-hexyl group, and a 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, 2-Ethylhexyl group, nonyl group, isononyl group, decyl group and the like are suitable.

From the above, as the 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) (Meta) acrylamide, N-isopropyl-hydroxy (meth) acrylamide and the like are suitable. Of 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.

Commercially available products of the component (a-2) include BHEA, HPA, HEMA, HPMA (above, manufactured by Nihon Kasei Co., Ltd.), 4HBA, CHDMA (above, manufactured by Nihon Kasei Co., Ltd.), HEA, HPA, 4-HBA (above, manufactured by Nihon Kasei Co., Ltd.). 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 (a-2) components can be used alone or in combination of two or more. Further, as the component (a-2), a commercially available product or a synthetic product may be used.

<Monomers copolymerizable with (a') (a-1) and (a-2) components>
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 object 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") and a macromonomer having a polymerizable functional group (a'-1) -2) (hereinafter, also referred to as "(a'-2) component") and other polymerizable monomers (a'-3) (hereinafter, also referred to as "(a'-3) component") can be exemplified.

<< (Meta) acrylic monomer having (a'-1) amide group >>
The component (a'-1) 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 equation (3),
R 8 _'is hydrogen atom or a methyl group,
R 9 _'is a single bond or a divalent organic group,
R _{10 'is} a hydrogen atom or a C 1 to 10 alkyl group carbon,
R _{11 'represents} a hydrogen atom, C 1 to 10 alkyl group carbon atoms, an acyl group, an epoxy group, an alkoxy group or a dimethylamino group having 1 to 6 carbon atoms.

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

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

The number of carbon atoms of the acyl group is also not particularly limited, but is preferably 1 or more and 18 or less, and more preferably 1 or more and 6 or less. The acyl group shall contain an acetoxy group.

Alkoxy groups 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 and 2-. A hexyloxy group, a 3-hexyloxy group, a cyclohexyloxy group and the like are suitable.

Moreover, the _{'R 11 and'} R _10, may form a ring, in the ring, have a oxygen atom (i.e., oxygen-containing heterocyclic group) or sulfur atom (i.e., sulfur-containing heterocyclic group) You may be doing 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 preferable. Among them, from the viewpoint of improving adhesiveness, (meth) acryloylmorpholine, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide, etc. Is preferable.

Commercially available products of the component (a'-1) include ACMO (registered trademark), DMAPAA (registered trademark), DMAA (registered trademark), NIPAM (registered trademark), DEAA (registered trademark) (all manufactured by KJ Chemicals Co., Ltd.). ), DAAm (above, manufactured by Nihon Kasei Corporation), NBMA, IBMA, NMMA, TBAA, MBAA (above, manufactured by 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 is composed of a polymer chain portion and a polymerizable functional group portion.

Bending resistance (bending resistance) is improved by including a polymer polymerized (cured) using such a monomer in the pressure-sensitive adhesive layer. The mechanism is considered to be different 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, so that cohesive force is generated in the pressure-sensitive adhesive layer. It is considered that this increases the adhesive force to the base material and improves the bending resistance. On the other hand, when the glass transition temperature of the polymer chain portion of the macromonomer is low, it is considered that the pressure-sensitive adhesive layer becomes flexible and the followability to the substrate is enhanced, so that the bending resistance is improved. The above mechanism is speculative, and the present invention is not limited to the above mechanism.

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

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). ) A (co) polymer having a repeating unit derived from acrylate, styrene, acrylonitrile, hydroxy (meth) acrylate, ethylhexyl acrylate, dimethylsiloxane or the like as a main constituent unit is preferable. These polymer chain moieties 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 bond group.

Examples of the divalent bonding group include a linear, branched or cyclic alkylene group, an aralkylene group, an arylene group and the like. These may further have a substituent such as a hydroxyl group or a cyano group. The number of carbon atoms of the alkylene group is preferably 1 or more and 10 or less, and more preferably 1 or more and 4 or less. 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 number of carbon atoms of the arylene group is preferably 6 or more and 12 or less. Examples of the arylene group include a phenylene group, a cumenylene group, a mesitylene group, a trilene group, a xylylene group, and the like. Of these, a phenylene group is preferable.

In addition, among the divalent bonding groups, -NR _2- , -COO-, -OCO-, -O-, -S-, -SO ₂ NH-, -NHSO _2- , -NHCOO-, -OCONH- Alternatively, a group derived from a heterocycle or the like may be interposed as a bonding group. The R ₂ is a hydrogen atom or an alkyl group such as a methyl group, an ethyl group or a propyl group.

Further, in the above formula (4), X ₂ is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, stearyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth). ) Represents a polymer obtained by homopolymerizing or copolymerizing one 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 a polymer obtained by homopolymerizing methyl (meth) acrylate, styrene, n-butyl (meth) acrylate, isobutyl (meth) acrylate, a polymer obtained by copolymerizing acrylonitrile and styrene, or a polyorganosiloxane. It is preferable to have. Further, from the viewpoint of durability at high temperature, 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 a polyorganosiloxane is preferred polydimethylsiloxane is particularly preferred. As long as it does not affect the performance of the pressure-sensitive adhesive, a part of the methyl group of the polydimethylsiloxane may be replaced with an organic group (ethyl group, phenyl group, etc.) other than a hydrogen atom or a methyl group.

The polydimethylsiloxane can be obtained by hydrolyzing and condensing dimethyldialkoxysilanes such as dimethyldimethoxysilane and dimethyldiethoxysilane. At this time, an organic group other than the methyl group can be introduced into the polydimethylsiloxane by using an alkoxysilane having an organic group other than the methyl group (for example, diethyldiethoxysilane, etc.) in combination. Further, in addition to the above-mentioned dialkoxy-type silane compound, a small amount of trialkoxy-type silane compound may be added.

The number average molecular weight (Mn) of the component (a'-2) is preferably in the range of 2000 or more and 20000 or less, more preferably in the range of 2000 or more and 10000 or less, and in the range of 4000 or more and 8000 or less. It is more preferable to be in. 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, when 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 the chain transfer agent, the polymerization initiator and the like added to the polymerization system. In the present invention, the polystyrene-equivalent value measured by the GPC (gel permeation chromatography) method is adopted as the number average molecular weight (Mn) of the macromonomer.

As the component (a'-2), a commercially available product or a synthetic product may be used. When synthesizing the component (a'-2), the synthesis method is not particularly limited. For example, (1) a polymer chain (living polymer anion) constituting a macromonomer is produced by living anion polymerization, and chloride methacrylate is used therein. (2) In the presence of a chain transfer agent such as mercaptoacetic acid, a radically polymerizable monomer such as methyl methacrylate is polymerized to obtain an oligomer having a carboxyl group at the terminal, which is then subjected to methacrylic acid. Method of reacting with glycidyl or the like; (3) A radically polymerizable monomer such as methyl methacrylate is polymerized in the presence of an azo polymerization initiator containing a carboxyl group to obtain an oligomer having a carboxyl group at the terminal, and then methacrylic acid. Any method can be used, such as a method of macromonomerizing with glycidyl.

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

Commercially available products of the component (a'-2) include, for example, a macromonomer having a methacryl group at the end and a polymer chain portion of polymethylmethacrylate (PMMA) (product name: 45% AA-6 (AA-6S)). ), AA-6; manufactured by Toa Synthetic Co., Ltd.), macromonomer whose polymer chain portion is polystyrene (product names: AS-6S, AS-6; manufactured by Toa Synthetic Co., Ltd.), polymer chain portion of styrene / acrylic nitrile Macromonomer which is a copolymer (product name: AN-6S; manufactured by Toa Synthetic Co., Ltd.), macromonomer whose polymer chain part is polybutyl acrylate (product name: AB-6; manufactured by Toa Synthetic Co., Ltd.), polymer chain part Is a macromonomer whose polymer chain is polyisobutylmethacrylate (product name: AW-6S; manufactured by Toa Synthetic Co., Ltd.), and a macromonomer whose polymer chain is polydimethylsiloxane (product name: AK-5; manufactured by Toa Synthetic Co., Ltd.). Can be used. These macromonomers may be used alone or in combination of two or more.

≪ (a'-3) Other polymerizable monomers≫
Specific examples of the component (a-1) and other polymerizable monomers copolymerizable with the component (a-2) include epoxy groups such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate. Acrylomonomer having; has an amino group such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, N-tert-butylaminoethyl (meth) acrylate, 2-((meth) acrylicoxy) ethyltrimethylammonium chloride, etc. (Meta) acrylic monomer; having a urethane group such as urethane (meth) acrylate (meth) acrylic monomer; having a phenyl group such as p-tert-butylphenyl (meth) acrylate and o-biphenyl (meth) acrylate (meth) Acrylovinyl monomer; Vinyl monimer having a silane group such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethyl) silane, vinyltriacetylsilane, methacryloyloxypropyltrimethoxysilane; styrene, chlorostyrene, α-methyl Examples thereof include styrene, 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 of (1) above >>
The content of the component (a-1) is preferably 70% by mass or more with respect to the total amount of the main agent (A) from the viewpoint of lowering the glass transition temperature after curing. When the upper limit of the content of the component (a-1) is 99.9% by mass or less, it is preferable because it is excellent in various durability, excellent in bending resistance at high temperature, and improved adhesive strength at high temperature. Further, 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 ensuring excellent adhesive strength while lowering the glass transition temperature after curing of the pressure-sensitive adhesive composition. , 75% by mass or more and 90% by 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 with respect to the total amount of the main agent (A) from the viewpoint of improving adhesiveness and ensuring durability, and is preferably 5% by mass. More preferably, it is% or more and 25% by mass or less.

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 amounts of the component (a-1) and 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 of (2) above≫
As one form according to the present invention, the main agent (A) is a constituent unit (1) derived from the component (a-1), the component (a-2) and the component (a-1), and a configuration derived from the component (a-2). Examples thereof include a form (a form in which the curable compound is composed of a monomer and a polymer) containing a copolymer (a-3) containing the unit (2) (hereinafter, also simply referred to as a copolymer (a-3)). In this embodiment, among the raw material monomers of the copolymer (a-3), the components (a-1) and (a-2) which are unreacted raw material monomers and the component (a') which is added as needed are contained. , A form of so-called polymer syrup, which is a solvent for dissolving the copolymer (a-3).

The preferable contents of the component (a-1), the component (a-2) and the component (a') in the form (2) are described in the section << Content of each component in the form (1) above >>. Since it is the same as the suitable content described above, the description thereof will be omitted here. The preferable contents of the component (a-1), the component (a-2) and the component (a') referred to here refer to the contents before a part thereof is copolymerized. The preferred contents of the unreacted component (a-1), component (a-2) and component (a') after partially copolymerizing are the amounts used for copolymerization ( It can be said that the range excluding the range of the content of the copolymer (a-3) below and the ratio of each structural unit constituting the nuclear copolymer (a-3)) is preferable. ..

Further, the suitable content of each structural unit of the copolymer (a-3) contained in the form (2) is the component described in the section << Content of each component in the form of (1) above >>. The suitable content of (component (a-1), component (a-2), component (a')) is applied as it is.

That is, the copolymer (a-3) contained in the form (2) contains a hydroxyl group of 70% by mass or more and 99.9% by mass or less of the structural unit derived from the (meth) acrylic acid ester monomer (a-1). Constituent 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) (However, the total amount of the constituent units derived from the components (a-1), (a-2), and (a') is 100% by mass). Is preferable. The copolymer (a-3) contained in the form (2) is more preferably a structural unit derived from the (meth) acrylic acid ester monomer (a-1), containing 75% by mass or more and 95% by mass or less of a hydroxyl group. Constituent unit derived from (meth) acrylic monomer (a-2) 5% by mass or more and 25% by mass or less, and a composition derived from a monomer (a') copolymerizable with the components (a-1) and (a-2). The unit includes 0% by mass or more and 5% by mass or less (however, the total amount of the constituent units derived from the components (a-1), (a-2), and (a') is 100% by 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 such that the pressure-sensitive adhesive composition has good applicability to the adherend and is durable. From the viewpoint of excellent folding resistance, it is 4% by mass or more and 20% by mass or less, and more preferably 6% by mass or more and 12% by mass or less. The content of the copolymer (a-3) can be controlled, for example, by controlling the polymerization rate in a massive polymerization method using a photopolymerization initiator described later.

[Production of copolymer (a-3)]
In the form of (2) 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, a bulk polymerization method, or an emulsification method using a polymerization initiator. Conventionally known methods such as a 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 an adiabatic polymerization method, a temperature control polymerization method, and an isothermal polymerization method. As the polymerization initiator, either a thermal polymerization initiator or a photopolymerization initiator may be used. In addition to or in addition to the method of initiating the polymerization with a polymerization initiator, a method of initiating the polymerization by irradiating an active energy ray such as radiation, an electron beam, or an ultraviolet ray can also be adopted. Of these, a solution polymerization method using a thermal polymerization initiator or a massive polymerization method using a photopolymerization initiator is more preferable because the molecular weight can be easily adjusted and impurities can be reduced. That is, at the stage of producing the copolymer (a-3) that can be contained in the main agent (A) as shown in Examples, it is not necessary to use a predetermined photopolymerization initiator (B) as the polymerization initiator. However, it may be used. In the form of (2) above, a predetermined photopolymerization initiator (B) is added to the main agent (A) obtained by the method for producing the copolymer (a-3) that can be contained in the main agent (A). Therefore, the pressure-sensitive adhesive composition can be formed. That is, the photopolymerization initiator (B) is used at the stage of curing the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer, and is a copolymer (a-3) that can be contained in the main agent (A). It is not always necessary to use it at the stage of manufacturing (see Examples). Of course, the predetermined photopolymerization initiator (B) may also be used at the stage of producing the copolymer (a-3) that can be contained in the main agent (A).

In one embodiment of the pressure-sensitive adhesive composition of the present invention, the copolymer (a-3) is the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group-containing (meth) acrylic monomer (a-2). ) And by solution polymerization of the reaction solution. As a solution polymerization method using a thermal polymerization initiator, for example, ethyl acetate, toluene, methyl ethyl ketone or the like is used as a solvent, and thermal polymerization is carried out with respect to 100 parts by mass of the total amount of the raw material monomers of the copolymer (a-3). Preferably, 0.01 part by mass or more and 1 part by mass or less of the 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) in a nitrogen atmosphere for 3 hours or more and 10 hours or less. Examples include a method of reacting.

Examples of the thermal polymerization initiator include 2,2-azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylbutyronitrile), azobiscyanovaleric acid, and 2,2'-azobis ( 4-methoxy-24-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'-azobis [2- (2- (2-) Imidazolin-2-yl) Propane] disulfate dihydrate, 2,2'-azobis (2-methylpropion amidine) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropion amidine] hydrate Late, 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2' Azobisisobuty such as −azobis [2-methyl-N- (2-hydroxyethyl) propionamide]; tert-butylperoxypivalate, tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate , Di-tert-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, tert-butyl hydroperoxide and other organic peroxides; hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate and other inorganic peroxides. Things can be mentioned. These thermal polymerization initiators can be used alone or in combination of two or more. 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 (a-1) It is also possible to obtain the main agent (A) (polymer syrup) composed of a-3) (form of (2) above).

The massive polymerization method using the photopolymerization initiator is not particularly limited, but for example, the raw material monomer of the copolymer (a-3) and the photopolymerization initiator are added, and the reaction initiation temperature is set in a nitrogen atmosphere. Usually, the active energy ray is irradiated at 20 ° C. or higher and 35 ° C. or lower. When the temperature in the reaction system rises from the reaction start temperature to 5 ° C. or higher and 15 ° C. or lower, the reaction is stopped by introducing air into the reaction system to obtain the copolymer (a-3). Can be mentioned. At this time, it is not necessary to react all the raw material monomers used, and the reaction may be stopped when the desired polymerization conversion rate (= appropriate viscosity) is reached. The unreacted raw material monomers (a-1), (a-2), and optionally added (a') serve as a solvent for dissolving the copolymer (a-3). According to the method, the main agent (A) (polymer syrup) containing the component (a-1), the component (a-2) and the copolymer (a-3) can be obtained (the form of (2) above). ..

Examples of active energy rays used in the massive polymerization method include ultraviolet rays (UV), visible light, laser rays, α rays, β rays, γ rays, X-rays, electron beams, etc. Ultraviolet rays are preferably used in terms of ease of handling and cost. That is, in a preferred embodiment of the pressure-sensitive adhesive composition of the present invention, the copolymer (a-3) is the (meth) acrylic acid ester monomer (a-1) and the hydroxyl group-containing (meth) acrylic monomer (meth). It is polymerized by irradiation with ultraviolet rays of a reaction solution containing a-2). More preferably, ultraviolet rays having a wavelength of 200 nm or more and 400 nm or less are used. Ultraviolet rays can be irradiated using a light source such as a high-pressure mercury lamp, a microwave-excited lamp, a chemical lamp, or a black light. Illuminance 0.1 mW / cm ² or more 20.0mW / cm ² or less.

Examples of photopolymerization initiators are acetophenone, 3-methylacetophenone, benzyldimethylketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1- (4-isopropylphenyl) -2-hydroxy-. 2-Methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, 2-hydroxy-2-methyl-1-phenylpropane-1-one, etc. Acetphenones; benzophenones such as benzophenone, 4-chlorobenzophenone, 4,4'-diaminobenzophenone; benzoin ethers such as benzoinpropyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; 1-hydroxy There are cyclohexylphenyl ketone, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone and the like. These photopolymerization initiators can be used alone or in combination of two or more.

Commercially available products may be used as the photopolymerization initiator, and examples of the commercially available products include, for example, Irgacure (registered trademark) 127, 184, 819, 907, 651, 1700, 1800, 819, 369, 261 and DaroCure (registered trademark). ) TPO, DaroCure (registered trademark) 1173 (above, manufactured by BASF Japan Ltd.), EzaCure (registered trademark) KIP150, TZT (above, manufactured by DKSH Japan Co., Ltd.), Kayacure (registered trademark) BMS, DMBI (above, Nippon Kayaku) Yaku Co., Ltd.) and the like.

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, based on 100 parts by mass of the total amount of the raw material monomers of the copolymer (a-3). Parts or more and 0.5 parts by mass or less.

In addition, a chain transfer agent can also be used to adjust the molecular weight in the synthesis of the 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 esters, 2-ethylhexylthioglycol, thioglycol. Mercaptans such as octyl acid; alcohols such as methanol, ethanol, propanol, n-butanol, isopropanol, t-butanol, hexanol, benzyl alcohol, allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane, trichloroethylene; acetone , Methylethylketone, cyclohexanone, acetophenone, acetaldehyde, propionaldehyde, n-butylaldehyde, furfural, benzaldehyde and other carbonyls; methyl-4-cyclohexene-1,2-dicarboxylic acid anhydride, α-methylstyrene and the like. 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 1 million or more and 2.5 million or less, and more preferably 1.2 million or more and 2.1 million or less. When the weight average molecular weight is 1 million or more, the durability and the occurrence of peeling / floating are excellent, and the adhesiveness is improved. Further, when it is 2.5 million or less, the viscosity of the copolymer solution becomes appropriate and workability such as coatability is improved.

[Photopolymerization Initiator (B)]
The pressure-sensitive adhesive composition according to the present invention contains a predetermined photopolymerization initiator (B). Specifically, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanol) and 2-hirodoxy-1- {4- [4- (2-hydroxy-2) -Methyl-propionyl) -benzyl] phenyl} -2-methyl-propane-1-one is at least one of them. Commercially available products may be used as the photopolymerization initiator (B), and examples of the commercially available products include, for example, Irgacure (registered trademark) 127 (manufactured by BASF Japan Ltd.), Ezacure (registered trademark) KIP150, One (above, DKSH). (Made by Japan Co., Ltd.), etc. In the pressure-sensitive adhesive composition according to the present invention, the main agent (A) composed of the above-mentioned curable compound containing an acrylic compound is combined with the above-mentioned specific photopolymerization initiator (B), and the pressure-sensitive adhesive composition is after curing. By adjusting and controlling the glass transition temperature to -57.5 ° C. or lower, the folding resistance can be improved while suppressing the content of the photopolymerization initiator (B) to a certain level, and the pressure-sensitive adhesive composition at a high temperature. It is excellent in that the weight loss rate of an object can be reduced and the generation of offensive odors and outgas can be effectively suppressed.

Further, by suppressing the content of the predetermined photopolymerization initiator (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 lowered. It can also be prevented from doing so. Specifically, the content of the photopolymerization initiator (B) is preferably in the range of 0.05 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the main agent (A). As a result, in addition to the above effects, when the main agent (A) is in the form of a polymer syrup, it is excellent in that the final copolymerization reaction is carried out to facilitate the formation of the pressure-sensitive adhesive layer. The amount of the photopolymerization initiator (B) added when the photopolymerization initiator (B) is added is more preferably 0.1 part by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the main agent (A).

The number average molecular weight (Mn) of the photopolymerization initiator (B) is preferably 300 or more, and more preferably 400 or more. When the number average molecular weight (Mn) is 300 or more, the solubility in the main agent (A) is excellent, the durability and the occurrence of peeling / floating are excellent, the adhesiveness is improved, and the offensive odor and outgas are removed. Occurrence can be suppressed. The upper limit of the number average molecular weight (Mn) of the photopolymerization initiator (B) is not particularly limited, and is included in the technical scope of the present invention when the effects of the present invention can be effectively exhibited. It is a thing. The number average molecular weight (Mn) of the photopolymerization initiator (B) can be measured by mass spectrometry [crosslinking agent].
The pressure-sensitive adhesive composition of the present invention can further contain a cross-linking agent. When the cross-linking agent is added, the optimum value is generated in a wide range depending on the type of the cross-linking agent used. For example, the cross-linking agent used in Examples and Comparative Examples described later is one that exerts its effect in the smallest amount, and is 0.2 parts by mass (in Examples) with respect to 100 parts by mass of the main agent (A). Even with the amount of addition), the effect can be sufficiently exerted. On the other hand, although not mentioned in the examples, in the experiments of the present inventors, for example, there are some cross-linking agents whose effect cannot be obtained unless about 10 parts by mass is added to 100 parts by mass of the main agent (A). It cannot be uniquely specified. As a rough guide, the range is 0.0001 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the main agent (A). Within the above guideline range, it is desirable to confirm and use the optimum range suitable for each cross-linking agent through preliminary experiments and the like. By using it in the optimum range suitable for each cross-linking agent, the gelation rate can be improved, and there is a technical effect of achieving both adhesiveness and bending resistance.

The type of the cross-linking agent that can be used in the pressure-sensitive adhesive composition of the present invention is not particularly limited, and is a vinyl compound (so-called acrylic cross-linking agent), an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, and a polyfunctional acrylic acid ester monomer. , A peroxide, a titanium coupling agent, a zirconium compound, an aluminum chelate compound and a thermoacid generator, preferably at least one selected from the group. In particular, it is more preferable that the cross-linking agent is at least one selected from the group consisting of vinyl compounds (so-called acrylic cross-linking agents), isocyanate compounds, carbodiimide compounds, oxazoline compounds, epoxy compounds, and peroxides. Further, from the viewpoint of adhesiveness and durability, at least one of a vinyl compound (so-called acrylic cross-linking agent), an isocyanate compound and a peroxide is more preferable.

The cross-linking agent according to the present invention includes one that forms a cross-linked structure by itself (curing agent type) and one that does not form a cross-linked structure by itself but promotes a cross-linking reaction (curing catalyst type). Also included. In particular, the latter are peroxides, thermoacid generators and the like.

(Vinyl compound (so-called acrylic cross-linking agent))
Examples of the vinyl compound (so-called acrylic cross-linking agent) preferably used as a cross-linking agent include acrylic acid or methacrylic acid having two or more polymerizable unsaturated bonds in the molecule, derivatives thereof, and the like, and in particular, an acryloyl group. It is preferable that the compound has two or more compounds in the molecule (hereinafter, also referred to as “acrylic acid-based derivative”), and the concentration of the acrylic acid-based derivative is 0.001 to 0 in terms of mass molar concentration of the acryloyl group. The range is preferably 2 mol / kg.

In addition, by molecular weight, examples of acrylic acid-based derivatives include (a) low molecular weight derivatives having a molecular weight of less than 4,000 and (b) high molecular weight derivatives having a molecular weight of 4,000 or more, which are classified below. I will explain.

Those with a low molecular weight (a) having a molecular weight of less than 4,000 are bisphenol A diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and 1,9-nonanediol diacrylate. , 1,3-butylene glycol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, glycerol diacrylate, neopentythritol glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polybutylene glycol diacrylate, trimethyl propantri Acrylate monomas such as acrylate, pentaerythritol triacrylate, tris (acryloxyethyl) isocyanurate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate; epoxy acrylate, polyester acrylate, urethane. Acrylic oligomas such as acrylates and acrylic acrylates; and the like; acrylates such as trimethylolpropantriacrylate, pentaerythritol triacrylate, tris (acryloxyethyl) isocyanurate, pentaerythritol tetraacrylate, and dipentaerythritol tetraacrylate are preferable. .. In addition, among the compounds having two or more polymerizable unsaturated bonds in the molecule, those having two or more acryloyl groups in the molecule can be appropriately selected and used. (A) Commercially available products having a molecular weight of less than 4,000 include A-TMM-3, A-TMM-3L, A-TMM-3LM-N, ATM-35E, A-TMMT, A-9550, A- DPH (above, Shin-Nakamura Chemical Industry 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 (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 can be exemplified.

Those having a high molecular weight (b) of 4,000 or more are high molecular weight compounds having two or more reactive unsaturated bonds (hereinafter referred to as "high molecular weight cross-linking agents") and are by weight. The average molecular weight is preferably 4,000 to 20,000, more preferably 8,000 to 16,000. If the molecular weight of the high molecular weight cross-linking agent exceeds 20,000, the viscosity of the pressure-sensitive adhesive composition becomes too high, making it difficult to prepare a sheet. As the high molecular weight cross-linking agent, the following (a) to (e) using alkylene glycol as a raw material are preferably mentioned from the viewpoint of compatibility of the pressure-sensitive adhesive composition with other pressure-sensitive adhesive composition materials before curing. ..

Examples of the vinyl compound (so-called acrylic cross-linking agent) preferably used as a cross-linking agent using alkylene glycol as a raw material include the following.

(A) Di (meth) acrylate of dialcohol compound; Di (meth) acrylate of dialcohol compound reacts with polyalkylene glycol such as polyethylene glycol, polypropylene glycol, polybutylene glycol and acrylic acid or methacrylic acid. Can be obtained.

(B) Di (meth) acrylate of epoxy resin; Di (meth) acrylate of epoxy resin is an epoxy in a molecule such as diglycidyl ether of polyalkylene glycol such as polyethylene glycol, polybropyrene glycol and polybutylene glycol. It is obtained by reacting an epoxy resin having two groups with acrylic acid or methacrylic acid.

(C) Polyester di (meth) acrylate having hydroxyl groups at both ends; Polyester di (meth) acrylate having hydroxyl groups at both ends is specifically produced by reacting a polyester polyol with a saturated acid and a polyhydric alcohol. To do. Saturated acids include aliphatic dicarboxylic acids such as azelaic acid, adipic acid, and sebatic acid, and polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, and the like. is there. Di (meth) acrylate of polyester can be obtained by reacting such a polyester polyol with acrylic acid or methacrylic acid.

(D) Polyurethane di (meth) acrylate; Polyurethane di (meth) acrylate is obtained by reacting a polyhydric alcohol compound with a polyhydric isocyanate compound. Examples of polyhydric alcohols include propylene glycol, tetramethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, and 2-methyl-. 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, poly1,2-butylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene glycol-propylene glycol block copolymer, Ethylene glycol-tetramethylene glycol copolymer, methylpentanediol-modified polytetramethylene glycol, propylene glycol-modified polytetramethylene glycol, propylene oxide adduct of bisphenol A, propylene oxide adduct of hydrogenated bisphenol A, propylene oxide adduct of bisphenol F , A propylene oxide adduct of hydrogenated bisphenol F and the like. Examples of the polyisocyanate compound include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylylene diisocyanate. There are diisocyanates, hydrogenated diphenylmethane diisocyanates, diisocyanates such as norbornene diisocyanates, and the above-mentioned diisocyanate polymers, urea-modified diisocyanates, and burette-modified products.

These polyhydric alcohols and polyisocyanates can be used alone or in combination of two or more.

Di (meth) acrylate of polyurethane can be obtained by reacting such a polyurethane compound having a hydroxyl group at the terminal obtained by reacting with an excess of polyhydric alcohol with acrylic acid or methacrylic acid.

(E) A compound obtained by reacting a polyurethane with a compound having a hydroxyl group and a reactive double bond (hereinafter, also referred to as “reactive double bond terminal polyurethane”); the reactive double bond terminal polyurethane is multivalent. It can be obtained by reacting a compound having an isocyanate group at the terminal obtained by reacting isocyanate in excess with a compound having a hydroxyl group and a reactive double bond. The compound having an isocyanate group at the terminal obtained by reacting the polyhydric isocyanate in excess can be obtained by using the same polyhydric alcohol compound and polyhydric isocyanate compound as the raw material of polyurethane described in (d) above. Can be done.

Examples of the compound having a reactive double bond with the hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, and ethylene glycol. -Acrylate derivatives such as -propylene glycol block copolymer monoacrylate, ethylene glycol-tetramethylene glycol copolymer monoacrylate, caprolactone-modified monoacrylate (trade name: Praxel FA series, manufactured by Daicel Chemical Co., Ltd.), pentaerythritol triacrylate, 2-hydroxy Ethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, ethylene glycol-propylene glycol block copolymer monomethacrylate, ethylene glycol-tetramethylene glycol copolymer mono. There are methacrylic acid derivatives such as methacrylate, caprolactone-modified monomethacrylate (trade name: Praxel FM series, manufactured by Daicel Chemical Co., Ltd.), pentaerythritol trimethacrylate and the like. These compounds are used alone or in combination of two or more.

(B) The high molecular weight cross-linking agent as a cross-linking agent having a molecular weight of 4,000 or more is (d) a polyurethane di (meth) acrylate from the viewpoint of the toughness of the cured product among the above (a) to (d). , (E) Reactive double bond end polyurethanes (particularly those whose reactive double bond is based on an acryloyl group) are preferred.

Further, among these, those in which the diol component of polyurethane is more preferably polypropylene glycol or polytetramethylene glycol, and those using polyurethane in which the diol component is polypropylene glycol or polytetramethylene glycol and the diisocyanate component is isophorone diisocyanate are used. Especially preferable.

When the compatibility between the main agent (A) and the high molecular weight cross-linking agent is low, the cured product becomes cloudy when the amount of the high molecular weight cross-linking agent is increased, but by using alkylene glycol as the raw material of the high molecular weight cross-linking agent, the main agent (A) ) Can be improved, and transparency can be maintained regardless of the amount of the high molecular weight cross-linking agent.

Further, by using a high molecular weight cross-linking agent as a vinyl compound (so-called acrylic cross-linking agent) preferably used as a cross-linking agent, the cured product becomes brittle and the adhesive strength becomes low even when used in a relatively large amount. You can prevent it from going too far. As a result, the amount of the cross-linking agent used can be increased, and it is possible to suppress changes in the characteristics of the cured product due to an error during compounding.

As a method for synthesizing the high molecular weight cross-linking agent, known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization can be used.

The above high molecular weight cross-linking agents can be used alone or in combination of two or more.

The vinyl compound (so-called acrylic cross-linking agent) preferably used as a cross-linking agent preferably contains 0.001 to 0.2 mol / kg in mass molar concentration of acryloyl group.

The amount of the vinyl compound (so-called acrylic cross-linking agent) preferably used as the cross-linking agent is more preferably 0.001 to 0.2 mol / kg in terms of the mass molar concentration of the acryloyl group, and 0.005 to 0. It is more preferably 1 mol / kg, and particularly preferably 0.01 to 0.08 mol / kg.

If the concentration of the vinyl compound (so-called acrylic cross-linking agent) preferably used as the cross-linking agent is less than 0.001 mol / kg in terms of the mass molar concentration of the acryloyl group, it is difficult for the cured product of the pressure-sensitive adhesive composition to maintain its shape. On the contrary, if it exceeds 0.2 mol / kg, the adhesive strength may be reduced or a problem may occur in the moisture resistance and heat reliability. In addition, the cured product of the pressure-sensitive adhesive composition may become brittle and problems may easily occur in mechanical properties.

As a vinyl compound (so-called acrylic cross-linking agent) preferably used as a cross-linking agent, in addition to a compound having two or more acryloyl groups in the molecule, a polymerizable unsaturated bond such as acrylonitrile, styrene, vinyl acetate, ethylene, or propylene is formed. A compound having one compound in the molecule can be used.

In the above, in order to obtain the effect of the present invention, two or more acryloyl groups are contained in the molecule among the total amount of the polymerizable compound used as the vinyl compound (so-called acrylic cross-linking agent) preferably used as the cross-linking agent. The amount of the monomer other than the compound (the compound having one polymerizable unsaturated bond in the molecule) is preferably 90% by mass or less, more preferably 50% by mass or less, still more preferably 20% by mass or less.

Further, as a vinyl compound preferably used as a cross-linking agent (so-called acrylic cross-linking agent), a compound having two or more acryloyl groups in the molecule and a compound having two or more polymerizable unsaturated bonds in the molecule are used in combination. can do. If there are too many compounds having two or more polymerizable unsaturated bonds in the molecule, the adhesive strength tends to be too small, and the adhesive sheet tends to be easily torn by impact.

(Isocyanate compound)
The isocyanate compound preferably used as a cross-linking agent is not particularly limited, and is, for example, trimethylolpropane tolylene diisocyanate, triaryl isocyanate, dimerate diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2, 6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene Diisocyanis, xylylene diisocyanate (XDI), tetramethylxylidene diisocyanate (TMXDI), trizine diisocyanis (TODI), 1,5-naphthalenediis diisocyanate (NDI), hexamethylene diisocyanis (HDI), trimethylhexamethylene diisocyanis (TMHDI), lysine Diisocyanate, norbornan diisocyanate methyl (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6-XDI (hydrousated XDI), H12-MDI (hydrousated MDI), carbodiimide-modified diisocyanate of the above diisocyanates. , Or these isocyanurate-modified diisocyanates, etc., and one or more of these can be used. In addition, it may be used in combination with a peroxide described later. Adducts of the above isocyanate compounds and polyol compounds such as trimethylolpropane, and biuret and isocyanurates of these isocyanate compounds can also be preferably used.

Further, as the isocyanate compound, a commercially available product or a synthetic product may be used. Examples of commercially available products include Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Coronate (registered trademark) 2030, Coronate (registered trademark) 2031 (all manufactured by Nippon Polyurethane Industry Co., Ltd.). ), Takenate (registered trademark) D-102, Takenate (registered trademark) D-110N, Takenate (registered trademark) D-200, Takenate (registered trademark) D-202 (all manufactured by Mitsui Chemicals, Inc.), Duranate (registered) Trademarks) 24A-100, Duranate® TPA-100, Duranate® TKA-100, Duranate® P301-75E, Duranate® E402-90T, Duranate® E405-80T , Duranate (registered trademark) TSE-100, Duranate (registered trademark) D-101, Duranate (registered trademark) D-201 (all manufactured by Asahi Kasei Chemicals Co., Ltd.), Sumijour (registered trademark) N-75, N-3200 , N-3300 (above, Sumika Bayer Urethane Co., Ltd.) and the like. Among these, Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Takenate (registered trademark) D-110N, Duranate (registered trademark) 24A-100, Duranate (registered trademark) TPA -100 is preferable, and Coronate (registered trademark) L, Coronate (registered trademark) HX, and Duranate (registered trademark) 24A-100 are more preferable.

(Carbodiimide compound)
The carbodiimide compound preferably used as a cross-linking agent is not particularly limited, and examples thereof include those described in paragraphs "0039" to "0046" of JP2012-246444 and those appropriately modified.

(Oxazoline compound)
The oxazoline compound preferably used as a cross-linking agent is not particularly limited, and examples thereof include those described in paragraph "0037" of Japanese Patent Application Laid-Open No. 2015-087539 or those obtained by appropriately modifying them.

(Epoxy compound)
As the epoxy-based cross-linking agent (epoxy compound) preferably used as the cross-linking agent, any suitable epoxy-based cross-linking agent can be adopted. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, tetraglycidyl. Xylenediamine, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether and the like can be used.

Examples of commercially available products include Tetrad (registered trademark) C and Tetrad (registered trademark) X manufactured by Mitsubishi Gas Chemical Company, Ltd., ADEKA (registered trademark) EPU series and ADEKA RESIN (registered trademark) EPR series manufactured by ADEKA Corporation, and stocks. Examples include Celokiside (registered trademark) manufactured by the company Daicel. In particular, liquid epoxy resins such as these are preferable because they facilitate the pressure-sensitive adhesive mixing operation when producing the pressure-sensitive adhesive layer.

(Peroxide)
As a peroxide preferably used as a cross-linking agent, any peroxide that can generate radicals by heating to achieve cross-linking of the pressure-sensitive adhesive can be used, but in consideration of workability and stability, it has a half-life of 1 minute. It is preferable to use a peroxide having a temperature of preferably 80 ° C. or higher and 160 ° C. or lower, and more preferably 90 ° C. or higher and 140 ° C. or lower. The half-life of peroxide is an index showing the decomposition rate of peroxide, which is the time when the decomposition amount of peroxide is halved, and the decomposition temperature for obtaining the half-life at an arbitrary time. The half-life at any temperature is described in the manufacturer's catalog, etc., for example, in the 9th edition of the organic peroxide catalog (May 2003) published by Nippon Oil & Fats Co., Ltd. (Nippon Oil Co., Ltd.). Are listed.

Examples of such peroxides include bis (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature 90.6 ° C.) and bis (4-t-butylcyclohexyl) peroxydicarbonate (92.1 ° C.). ), Bis-sec-butylperoxydicarbonate (92.4 ° C.), t-butylperoxyneodecanoate (103.5 ° C.), t-hexylperoxypivalate, (109.1 ° C.). ), T-Butylperoxypivalate (110.3 ° C), dilauroyl peroxide (116.4 ° C), bis-n-octanoyl peroxide (117.4 ° C), 1,1,3 , 3-Tetramethylbutylperoxy-2-ethylhexanoate (124.3 ° C), bis (4-methylbenzoyl) peroxide (128.2 ° C), dibenzoyl peroxide (130.0 ° C) , T-Butyl peroxybutyrate (136.1 ° C.), and bis (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, and dibenzoyl peroxide having excellent cross-linking reaction efficiency are preferable. Used. In particular, bis (4-t-butylcyclohexyl) peroxydicarbonate is preferable from the viewpoint of decomposition temperature. One kind or two or more kinds of these can be used. Further, it may be used in combination with the above-mentioned isocyanate compound.

(Titanium coupling agent)
The titanium coupling agent preferably used as a cross-linking agent is not particularly limited, and is not particularly limited, for example, those described in paragraph "0072" of JP-A-2014-085616 or those appropriately modified. Can be mentioned.

(Zirconium compound)
The zirconium compound preferably used as a cross-linking agent is not particularly limited, and examples thereof include those described in paragraph "0073" of JP-A-2014-085616 or those appropriately modified.

(Aluminum chelate compound)
The aluminum chelate compound preferably used as a cross-linking agent is not particularly limited, and examples thereof include those described in paragraph "0037" of JP-A-2008-251089 or those appropriately modified thereof.

(Thermal acid generator)
Examples of the thermoacid generator include hexafluoroantimonate-based sulfonium salts, and commercially available products include SI-60, SI-60L, SI-80, SI-80L, SI-100, and SI-100L (above, Sanshin). (Chemical Industry Co., Ltd.), CI-2624 (all manufactured by Nippon Soda Co., Ltd.) and the like. The thermoacid generator may be used alone or in combination of two or more.

[Silane coupling agent]
The pressure-sensitive adhesive composition of the present invention can also further contain a silane coupling agent. This is because when a silicon film is used, the adhesion with the silicon film is improved by containing a silane coupling agent.

A silane coupling agent refers to an agent that does not have a siloxane bond and has two or more different reactive groups in the molecule.

The silane coupling agent used in the pressure-sensitive adhesive composition of the present invention is not particularly limited, and for example, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltri. Methoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, vinyl trichloro Silane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-gly Sidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyl Triethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β -(Aminoethyl) -γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, Examples thereof include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis- (3- [triethoxysilyl] propyl) tetrasulfide, and γ-isocyanuppropyltriethoxysilane. Furthermore, a silane cup containing a silane coupling agent having a functional group such as an epoxy group (glycidoxy group), an amino group, a mercapto group, and a (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, a commercially available product or a synthetic product may be used. Commercially available silane coupling agents include, for example, KBM-303, KBM-403, KBE-402, KBE-403, KBE-502, KBE-503, KBM-5103, KBM-573, KBM-802, KBM- 803, KBE-846, KBE-9007 (all manufactured by Shin-Etsu Chemical Co., Ltd.) and the like can be mentioned.

The silane coupling agent 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, 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). It is more preferably 001 parts by mass or more and 5 parts by mass or less, and particularly preferably 0.01 parts by mass or more and 3 parts by mass or less. Within 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, Alicyclic hydrocarbons such as methylcyclohexane; organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone can be mentioned. These solvents can be used alone or in combination of two or more.

Further, as described above, when the copolymer (a-3) is synthesized by the massive polymerization method using a photopolymerization initiator, the obtained copolymer (a-3) is unreacted (a). It can be a so-called polymer syrup in which at least one of a component (-1), a component (a-2) and a component (a') is contained as a solvent. 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 ingredients]
The above-mentioned pressure-sensitive adhesive composition may be used as a cross-linking accelerator, an antistatic agent, a filler, a colorant (pigment, dye, etc.), an ultraviolet absorber, an antioxidant, a chain transfer agent, a plasticizer, a softener, and the like. Known additive components (other additive components) such as surfactants and antistatic agents may be contained within a range that does not impair the effects of the present invention.

[Manufacturing method of adhesive composition]
The method for producing the pressure-sensitive adhesive composition is not particularly limited. For example, in the case of the above-mentioned form (1) in which the curable compound in the main agent (A) consists only of a monomer, the component (a-1), the component (a-2), the photopolymerization initiator (B), and if necessary Examples thereof include a method of mixing and producing the component (a'), a cross-linking agent, a silane coupling agent, a solvent, and other additive components to be added accordingly.

When the curable compound in the main agent (A) is in the form of the above (2) composed of a monomer and a polymer, a polymer syrup containing a component (a-1), a component (a-2) and a copolymer (a-3). , Photopolymerization initiator (B), and a method of mixing and producing the component (a') added as needed, a cross-linking agent, a silane coupling agent, a solvent, and other additive components.

The method of adding the photopolymerization initiator (B) according to the present invention is not particularly limited. For example, the photopolymerization initiator (B) is prepared by dissolving the photopolymerization initiator (B) in at least one of the components (a-1) and (a-2), and the solution (B) is prepared as the main agent (A). ) May be adjusted and added so as to have a desired content with respect to the total amount of the curable compound constituting the above. Alternatively, as shown in Examples, the photopolymerization initiator (B) may be dissolved in a polymer syrup so as to have a desired content with respect to the total amount of the curable compound constituting the main agent (A). Good.

[Adhesive layer]
In one embodiment of the present invention, there is provided 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, coating) the pressure-sensitive adhesive composition (solution) of the present invention to an appropriate base material (support), It can be formed by appropriately applying a curing treatment. When performing two or more types of curing treatments (drying, cross-linking, polymerization, etc.), these can be performed simultaneously or in multiple stages. In the pressure-sensitive adhesive composition of the present invention, a final copolymerization reaction is typically carried out as the curing treatment (component (a-1), component (a-2), and / or a copolymer ( a-3 and (a') component added as needed) are subjected to a copolymerization reaction to form a complete polymer). For example, when an active energy ray-curable pressure-sensitive adhesive composition is used, activation energy ray irradiation is performed. If necessary, curing treatment such as crosslinking and drying may be carried out. When it is necessary to dry with an active energy ray-curable pressure-sensitive adhesive composition, it is advisable to perform active energy ray-curing after drying.

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

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

The coating method is not particularly limited, and various known methods are used. For example, by 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 include a method such as an extrusion coating method.

Since the pressure-sensitive adhesive composition of the present invention contains a predetermined photopolymerization initiator (B), the pressure-sensitive adhesive composition of the present invention can be directly applied onto an adherend, or a base material or a separator can be applied. The pressure-sensitive adhesive layer can be obtained by irradiating an active energy ray after coating on a predetermined object to be coated such as, or after coating on one side on a support (base material). 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.

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 heating and 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.

In addition, 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. The heat drying can be performed twice or more under different conditions. For example, after drying at 40 ° C. or higher and lower than 100 ° C. for 0.1 minutes or more and 10 minutes or less, additional drying treatment may be performed at 100 ° C. or higher and 200 ° C. or lower for 1 minute or longer and 20 minutes or shorter. This can prevent peeling, floating, and cracking due to the rapid volatilization of the solvent.

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, the pressure-sensitive adhesive layer such as an optical film used for a flexible display such as a curved display is preferably 1 μm or more and 200 μm or less from the viewpoint of adhesiveness and bending resistance. In particular, when the pressure-sensitive adhesive layer is formed by using the pressure-sensitive adhesive composition of the present embodiment, even if the pressure-sensitive adhesive layer is significantly reduced as compared with the conventional case, a thick film of a flexible display such as a curved display currently provided ( The thickness (dry film thickness) of the pressure-sensitive adhesive layer of the present invention is 1 μm or more and 70 μm because it has high adhesiveness at the same level as (usually about 200 μm) and more excellent bending resistance than a thick film. It is more preferably 5 μm or more and 70 μm or less.

Further, when the pressure-sensitive adhesive layer according to the present invention is exposed, the pressure-sensitive adhesive layer can be protected by a peel-treated sheet (separator) or the like until it is put into 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, and the like. Examples thereof include plastic films such as polyurethane films and ethylene-vinyl acetate copolymer films. In addition, porous materials such as paper, cloth, and non-woven fabric, nets, foam sheets, metal foils, and appropriate thin leaves such as laminates thereof can be mentioned. 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 5 μm or more and 100 μm or less.

Further, the separator may be subjected to a mold release treatment and an antifouling treatment with a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, etc., as needed, a coating type, a kneading type, and a vapor deposition. Antistatic treatment such as mold can be performed. In particular, the peelability from the pressure-sensitive adhesive layer can be further enhanced by appropriately performing a peeling 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 embodiment of the present invention, there is provided a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive sheet is a so-called base-attached pressure-sensitive adhesive sheet (single-sided) in which the pressure-sensitive adhesive layer is fixedly provided on one or both sides of a sheet-like base material (support), that is, the pressure-sensitive adhesive layer is provided without the intention of separating the pressure-sensitive adhesive layer from the base material. Alternatively, it may be a double-sided adhesive sheet), or the adhesive layer is provided on a peelable substrate such as a release film (release liner) (release paper, resin sheet whose surface has been peeled, etc.). It may be 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 sticking.

The concept of an adhesive sheet as used herein may include what is called an adhesive tape, an adhesive label, an adhesive film, or the like. The pressure-sensitive adhesive layer is not limited to the one formed continuously, and may be, for example, a pressure-sensitive adhesive layer formed in a regular or random pattern such as a dot shape or a striped shape.

Examples of the base material (support) include plastic base materials such as polyethylene terephthalate (PET) and polyester film, porous materials such as paper and non-woven fabric, and metal foil.

The constituent material of the plastic base material is not particularly limited as long as it can be formed in the form of a sheet or a film, and for example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1- Polyesters such as penten, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer; polyethylene terephthalate (PET) , Polyesters such as polyethylene naphthalate and polybutylene terephthalate; polyamides such as polyacrylates, polystyrenes, nylons 6, nylons 6 and 6, and partially aromatic polyamides; polyvinyl chlorides, vinylidene chlorides, polycarbonates and the like.

The thickness of the base material is not particularly limited, but is preferably 4 μm or more and 100 μm or less, and more preferably 4 μm or more and 50 μm or less.

If necessary, the plastic base material is subjected to mold release with a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, etc., antifouling treatment, acid treatment, alkali treatment, primer treatment, etc. , Corona treatment, plasma treatment, easy adhesion treatment such as ultraviolet treatment, and antistatic treatment such as coating type, kneading type, and vapor deposition type can also be performed.

Moreover, as the release film (release liner), the separator exemplified above can be mentioned.

[Use]
The pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and pressure-sensitive adhesive sheet of the present invention described above are applied to various uses, for example, for optical members such as optical films. 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 containing at least a polarizing plate or a retardation plate and further including at least one of a conductive layer and a protective layer, a cover film, a transparent conductive film, a wind film, and a viewing angle expanding film for improving the viewing angle of a liquid crystal display. Such as an optical compensation film, a brightness improving film for increasing the contrast of a display, and a film in which these are laminated. That is, in one embodiment of the present invention, there is provided an optical member including a pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition according to the present invention.

The pressure-sensitive adhesive composition of the present invention may be used by directly applying it to one side or both sides of an optical member to form a pressure-sensitive adhesive layer, or a pressure-sensitive adhesive layer is previously formed on a release film, and the pressure-sensitive adhesive layer is formed on the release film. It may be used by transferring to one side or both sides of. 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 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 preferably used in an image display device. 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 an adhesive composition, an adhesive layer, an adhesive sheet, and an image display device, and the adhesive force and peeling and floating occur even when bent under high temperature conditions and low temperature conditions. It is possible to provide a pressure-sensitive adhesive composition having an excellent balance between bending resistance, which is almost nonexistent. Further, the pressure-sensitive adhesive composition of the present invention is suitably used for manufacturing 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. What you get.

The effects of the present invention will be described with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In addition, each part and% in each example is based on mass. All the conditions for leaving at room temperature, which are not specified below, are 23 ° C. (normal temperature) and 55% RH.

<Viscosity>
The temperature of the main agent (A) placed in a glass bottle was adjusted to 25 ° C., and the temperature was 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: Made by Tosoh, G7000H _XL + GMH _XL + GMH _XL
-Column size: 7.8 mm φ x 30 cm each 90 cm in total
-Column temperature: 40 ° C
・ Flow rate: 0.8 ml / min
・ Injection amount: 100 μl
-Eluent: Tetrahydrofuran-Detector: Differential Refractometer (RI)
-Standard sample: polystyrene.

(Manufacturing 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 in which four black light lamps (FL20SBL manufactured by Sankyo Electric Co., Ltd., emission wavelength 315 nm or more and 400 nm or less) were placed on all sides of the flask in an environment where external ultraviolet rays were cut off.

2-Ethylhexyl acrylate (2EHA) (manufactured by Nihon Kasei Co., Ltd.) 81 parts by mass, 4-hydroxybutyl acrylate (4HBA) (manufactured by Nihon Kasei Co., Ltd.) in a reaction vessel equipped with a nitrogen gas introduction tube, a thermometer and a stirrer. 15 parts by mass, 3 parts by mass of methoxypolyethylene glycol acrylate (AM-130G, manufactured by Shin-Nakamura Chemical Co., Ltd.), 1 part by mass of N-hydroxyethylacrylamide (HEAA) (manufactured by KJ Chemicals Co., Ltd.) and 2,2 as a polymerization initiator. -Dimethoxy-1,2-diphenylethane-1-one (Irgacure (registered trademark) 651; manufactured by BASF) was added in an amount of 0.005 parts by mass and dissolved (the polymerization initiator was dissolved in a monomer solution), and then a nitrogen atmosphere was obtained. Below, UV irradiation was performed at room temperature. Specifically, in order to initiate polymerization, black light (FL20SBL, manufactured by Sankyo Electric Co., Ltd.) was used to irradiate ultraviolet rays (UV) (wavelength: 365 nm) with an illuminance of 2.5 mW / cm ² . After the start of the reaction (irradiation), the temperature of the reaction system rose, but when the rise in the reaction temperature from the start of the reaction (irradiation) reached 7 ° C, the irradiation of black light was stopped and the air pump was installed in the reaction vessel. The reaction was forcibly stopped by introducing air. That is, UV irradiation is carried out until the temperature rise from the start reaches 7 ° C., whereby the main agent (A), which is a polymer solution, contains a copolymer (a-3-1) in which a part of the above-mentioned monomer components is polymerized. -1) (the form of so-called polymer syrup) was prepared.

The weight average molecular weight of the copolymer (a-3-1) in the main agent (A-1) was 1.92 million (in terms of GPC polystyrene), and the polymerization rate was 10.0%. The viscosity of the main agent (A-1) was 1400 mPa · s. The amount of the copolymer (a-3-1) in the main agent (A-1) was 10.0 parts by mass. The above-mentioned "polymerization rate" is a value of the reaction rate calculated with the case where all the charged monomers are polymers as 100% (hereinafter, the same applies).

(Manufacturing Example 2)
<Preparation of main agent (A-2) for comparison>
The main agent (A-2) was prepared as shown below.

The reaction was carried out in a reaction box in which four black light lamps (FL20SBL manufactured by Sankyo Electric Co., Ltd., emission wavelength 315 nm or more and 400 nm or less) were placed on all sides of the flask in an environment where external ultraviolet rays were cut off.

In a reaction vessel equipped with a nitrogen gas introduction tube, a thermometer and a stirrer in the above box, 70 parts by mass of 2-ethylhexyl acrylate (manufactured by Nihon Kasei Co., Ltd.) and 30 mass by mass of 4-hydroxybutyl acrylate (manufactured by Nihon Kasei Co., Ltd.) Dissolve by blending 0.005 parts by mass of 2,2-dimethoxy-1,2-diphenylethane-1-one (Irgacure (registered trademark) 651; manufactured by BASF) as a part and a polymerization initiator (monomer of the polymerization initiator). After dissolution in the solution), UV irradiation was performed at room temperature in a nitrogen atmosphere. Specifically, in order to initiate polymerization, black light (FL20SBL, manufactured by Sankyo Electric Co., Ltd.) was used to irradiate ultraviolet rays (UV) (wavelength: 365 nm) with an illuminance of 2.5 mW / cm ² . After the start of the reaction (irradiation), the temperature of the reaction system rose, but when the rise in the reaction temperature from the start of the reaction (irradiation) reached 7 ° C, the irradiation of black light was stopped and the air pump was installed in the reaction vessel. The reaction was forcibly stopped by introducing air. That is, UV irradiation is carried out until the temperature rise reaches 7 ° C. from the start, whereby the main agent (A-) which is a polymer solution containing a copolymer (a-3-2) in which a part of the above-mentioned monomer components is polymerized. 2) (the form of so-called polymer syrup) was prepared.

The weight average molecular weight of the copolymer (a-3-2) in the main agent (A-2) was 2.2 million (in terms of GPC polystyrene), and the polymerization rate was 9.5%. The viscosity of the main agent (A-2) was 2500 mPa · s. The amount of the copolymer (a-3-2) in the main agent (A-2) was 9.5 parts by mass.

<Measurement of glass transition temperature of homopolymer>
The Tg of the homopolymer shown in Table 2 below is a value obtained by the DSC method according to JIS K7121 (1987). Further, if the catalog value of each manufacturer is a value obtained by the above measurement method, the catalog value of each manufacturer may be applied.

[Evaluation 1]
<Measurement of glass transition temperature of the main agent (= adhesive composition after curing)>
The glass transition temperature (Tg) of each base material (copolymer) (= pressure-sensitive adhesive composition after curing) is a monomer unit constituting the copolymer (a-3-1, a-3-2) of each base material. And the ratio, it is a value calculated by the following FOX formula. Each homopolymer Tg is -64.5 ° C for 2-ethylhexyl acrylate, -37.2 ° C for 4-hydroxybutyl acrylate, -66.6 ° C for methoxypolyethylene glycol acrylate AM-130G, and 91 for N-hydroxyethyl acrylamide. The temperature was 0.7 ° C., the Tg of the main agent (A-1) was −59.9 ° C, and the Tg of the main agent (A-2) was −57.0 ° C.

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

(Example 1)
(Preparation of adhesive composition)
Oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl)) as the photopolymerization initiator (B) with respect to 100 parts by mass of the main agent (A-1) obtained in Production Example 1. Propanon) (EzaCure (registered trademark) One, manufactured by DKSH Japan Co., Ltd .; number average molecular weight 424.57) was blended in an amount of 0.3 parts by mass, and mixed and defoamed to obtain a photopolymerizable pressure-sensitive adhesive composition. ..

(Formation of adhesive layer)
Next, this photopolymerizable pressure-sensitive adhesive composition (coating liquid) was subjected to a mold release treatment with a silicone-based mold release agent as a release film (trade name: MRF50, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., thick). S: 50 μm) was applied using a baker type applicator to a coating thickness of 50 μm to form a coating film. By laminating and adhering another PET film (release film) that has been subjected to a mold release treatment with a silicone-based mold release agent similar to the above on this coating film, the pressure-sensitive adhesive composition is placed above and below the coating film. A release film was placed and laminated (sealed) in a sandwich shape. Then, at room temperature, a black light (FL20SBL, manufactured by Sankyo Electric Co., Ltd.) is used to irradiate ultraviolet rays (wavelength: 365 nm) with an illuminance of 2.5 mW / cm ² for 10 minutes (integrated light intensity: 1500 mJ / cm ² ). , The coating film of the pressure-sensitive adhesive composition was cured. As a result, a pressure-sensitive adhesive sheet having a colorless and transparent pressure-sensitive adhesive layer having a thickness of 50 μm sandwiched between two PET films was obtained.

(Example 2)
In Example 1, the photopolymerization initiator (B) oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) (Ezacure® One, DKSH Japan Co., Ltd. Manufactured; instead of oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) (Ezacure (registered trademark) KIP150; DKSH Japan Co., Ltd.) The pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1 except that 2-hydroxy-2-methyl [4- (1-methylvinyl) phenyl] propanol oligomer was used).

(Example 3)
In Example 1, the photopolymerization initiator (B) oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) (Ezacure (registered trademark) One, DKSH Japan Co., Ltd. Manufactured; instead of 2-hirodoxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane-1- An pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1 except that benzene (Irgacure (registered trademark) 127) and BASF Japan Co., Ltd. were used.

(Example 4)
In the same manner as in Example 1, the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet were used in the same manner as in Example 1 except that 0.1 part by mass of the photopolymerization initiator (B) was used instead of 0.3 parts by mass. Was produced.

(Example 5)
In the same manner as in Example 1, the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet were used in the same manner as in Example 1 except that 1.0 part by mass of the photopolymerization initiator (B) was used instead of 0.3 parts by mass. Was produced.

(Example 6)
In Production Example 1, 0.2 parts by mass of dipentaerythritol hexaacrylate (A-DPH, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) was further used as the cross-linking agent (C) with respect to 100 parts by mass of the main agent (A-1). A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1 except for the above.

(Example 7)
In Example 6, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 6 except that 0.2 parts by mass of the cross-linking agent (C) was used instead of 0.3 parts by mass. did.

(Comparative Example 1)
In Example 1, the photopolymerization initiator (B) oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) (Ezacure® One, DKSH Japan Co., Ltd. Co., Ltd .; Adhesive composition in the same manner as in Example 1 except that 1-hydroxycyclohexylphenyl ketone (Irgacure (registered trademark) 184, manufactured by BASF Japan Co., Ltd.) was used instead of the number average molecular weight 424.57). A product and an adhesive sheet were prepared.

(Comparative Example 2)
In Example 1, the photopolymerization initiator (B) oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) (Ezacure® One, DKSH Japan Co., Ltd. Manufactured; instead of 2-hirodoxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) phenoxy] phenyl} -2-methylpropanone (Ezacure (registered)) A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were produced in the same manner as in Example 1 except that KIP160 (trademark); manufactured by DKSH Japan Co., Ltd .; number average molecular weight 342.39) was used.

(Comparative Example 3)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that the main agent (A-2) was used instead of the main agent (A-1) in Example 3.

<Measurement of storage elastic modulus>
The adhesive sheets obtained in each Example and Comparative Example were cut into a size of 1.0 mm × 1.0 mm, the two PET films were peeled off, the adhesive layer was taken out, and the thickness was 3 mm. Laminated. The laminated pressure-sensitive adhesive layer (cured pressure-sensitive adhesive composition) was attached to a dynamic viscoelasticity measuring device (Exstar DMS7100, manufactured by Hitachi High-Tech Science Corporation). Measurements were made in the temperature range of -30 to 100 ° C in shear shear mode, frequency 1 Hz, heating rate 5 ° C / min, and storage elastic modulus G'(-20) at -20 ° C and storage elasticity at 80 ° C. The rate G'(80) was measured. The results obtained are shown in Table 3 below.

<Measurement of glass transition temperature after curing of adhesive composition>
The glass transition temperature after curing was measured using the pressure-sensitive adhesive compositions prepared in each Example and Comparative Example. That is, the measurements were carried out by the DSC method according to JIS K7121 (1987), and these results are the same as the values obtained by measuring the glass transition temperature (Tg) of the main agent (copolymer). The description here will be omitted. The obtained results are shown in Table 2 above.

[Evaluation]
<Measurement of gel fraction>
The gel fraction of the pressure-sensitive adhesive composition prepared in each Example and Comparative Example was measured. The gel fraction was determined by the following method. That is, about 0.1 g of the pressure-sensitive adhesive composition was weighed and the weight W ₁ (g) was measured. This was collected in a sample bottle, about 30 g of ethyl acetate was added, and the mixture was left for 24 hours. After the lapse of a predetermined time, the contents of the sample bottle were filtered by a 200 mesh stainless steel wire mesh (the weight of the membrane was W ₂ (g)), and the wire mesh and the residue were dried at 90 ° C. for 1 hour. ₃ (g) was measured. The gel fraction was calculated from these measured values by the following formula 2. The results obtained are shown in Table 3 below.

<Measurement of adhesive strength>
Two PET films were peeled off from the pressure-sensitive adhesive sheets obtained in each Example and Comparative Example, and the pressure-sensitive adhesive layer was taken out.

Two PET films having a thickness of 50 μm (trade name: MRF50, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) were prepared, and the surface of the PET film that had not been peeled was subjected to corona treatment. The above pressure-sensitive adhesive layer was adhered to the corona-treated surface using a laminator, cut into a width of 25 mm and a length of 100 mm, and then autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to completely adhere to the surface. Then, after allowing to stand at 23 ° C. and 55% RH atmosphere for 1 hour, the adhesive strength was measured. The corona treatment was performed by using a 3DT corona treating system (manufactured by Poly DYNE) and passing a PET film twice through a corona irradiation unit set at a speed of 1.6 m / min and a voltage of 9.5 kV.

Adhesive strength is 23 ° C, 55% RH atmosphere, sample is peeled using a tensile tester (Tencilon universal material tester STA-1150, manufactured by Orientec Co., Ltd.) with a peeling angle of 180 ° and a peeling speed of 0.3 m / min. It was determined by measuring the adhesive force (g / 25 mm) when the PET film was peeled off in accordance with the test method of the adhesive tape and the adhesive sheet of JIS Z0237 (2009). The results obtained are shown in Table 3 below.

<Measurement of shear strain>
The pressure-sensitive adhesive composition obtained in each Example and Comparative Example was applied onto a PET film having a thickness of 50 μm (trade name: MRF50, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) using a baker-type applicator, and a coating film was applied. Got The obtained coating film was irradiated with ultraviolet rays (wavelength: 360 nm) having an illuminance of 2.5 mW / cm ² for 10 minutes (integrated light intensity: 1500 mJ / cm ² ) using a black light to cure the coating film. As a result, a pressure-sensitive adhesive layer having a thickness of 100 μm was obtained.

The obtained PET film with an adhesive layer was prepared into a joint-shaped test piece so that the adhesive area between the PET film and the adhesive layer was 4 cm ² . This test piece was attached to a tensile test device (trade name: Tensilon universal material tester STA-1150, manufactured by Orientec Co., Ltd.) and sheared and deformed at a chuck moving speed of 30 mm / min at 23 ° C. and a 55% RH atmosphere. The load and elongation at the time were measured. The value obtained by dividing the load obtained by the measurement by the adhesive area was defined as the shear strength, and the strain was obtained by measuring the strain when this value reached 90 kPa. The results obtained are shown in Table 3 below.

<Measurement of folding resistance (bending test)>
Two PET films were peeled off from the adhesive sheets obtained in each Example and Comparative Example, and an adhesive layer having a thickness of 50 μm was taken out and placed on a PET film having a thickness of 150 μm (trade name: A4300, manufactured by Toyobo Co., Ltd.). After attaching an adhesive layer having a thickness of 50 μm using a handler minator, a PET film having a thickness of 100 μm (trade name: A4100, manufactured by Toyobo Co., Ltd.) is further layered under the conditions of 50 ° C. and 0.5 MPa. It was autoclaved for 15 minutes and allowed to adhere completely. As a result, a pressure-sensitive adhesive sheet was obtained in which two PET films were bonded by an pressure-sensitive adhesive layer having a thickness of 50 μm.

The obtained adhesive sheet is used in a bending tester (trade name: folding tester, manufactured by Tester Sangyo Co., Ltd.) under the conditions of a low temperature environment of -20 ° C and a high temperature environment of 60 ° C. , Apply a repeated bending load with a curvature of 3 mm (1 hour 300 cycles = 300 cycles / hr, number of repetitions: 30,000 times), and visually check whether the adhesive layer and the PET film are peeled off, floated, wrinkled, etc. did. The evaluation results are shown in Table 3 below. If the evaluation result is "○", it is practical.

(Evaluation criteria)
◯: Indicates that there was no peeling, floating, wrinkles, etc. ×; Indicates that there was peeling or floating.

<Weight reduction rate>
0.3 g of the adhesive sheet obtained in each Example and Comparative Example was dried in a warm air oven at 150 ° C. for 1 hour, taken out, allowed to stand at room temperature for 1 minute, weighed, and the difference was calculated by the following formula. The weight loss rate (%) was calculated. The results obtained are shown in Table 3 below.

Details of the photopolymerization initiator (B) and the cross-linking agent (C) in Table 3 are shown in Table 4 below.

Claims (6)

Contains a main agent (A) and a photopolymerization initiator (B) composed of a curable compound.
The main agent (A)
(I) A combination of a (meth) acrylic acid ester monomer (a-1) and a hydroxyl group-containing (meth) acrylic monomer (a-2), or (ii) the (meth) acrylic acid ester monomer (a-1). The hydroxyl group-containing (meth) acrylic monomer (a-2), the structural unit (1) derived from the (meth) acrylic acid ester monomer (a-1), and the hydroxyl group-containing (meth) acrylic monomer (a-). 2) Containing a combination of the copolymer (a-3) containing the structural unit (2) derived from 2).
The photopolymerization initiator (B) is oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) and 2-hirodoxy-1- {4- [4- ( 2-Hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane-1-one, which is at least one of them.
Glass transition temperature after curing Ri der -57.5 ° C. or less,
A pressure-sensitive adhesive composition having a shear strain of 800% or more under 90 kPa shear stress after curing . The pressure-sensitive adhesive composition according to claim 1, wherein the content of the photopolymerization initiator (B) is in the range of 0.05 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the main agent (A). object. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the storage elastic modulus at 80 ° C. after curing is 2.0 × 10 ⁴ Pa or more. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the storage elastic modulus at −20 ° C. after curing is 3.5 × 10 ⁵ Pa or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 4 , wherein the gel fraction is 50% or more and 90% or less. A pressure-sensitive adhesive sheet for a display, comprising a pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition according to any one of claims 1 to 5 .