JP4794691B2 - Adhesive and adhesive film - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive that can be used in various applications including the production of optical products such as liquid crystal displays and touch panels.

  In recent years, technological advances in the display field such as electronic paper and organic EL (Organic LED) have been remarkable, and products capable of satisfying required performance such as a higher level of visibility and durability have been developed one after another.

  Such a display is generally transparent by using an adhesive on the surface of the display element from the viewpoint of preventing damage to the display element such as an organic EL element from an external impact and ensuring good visibility. In many cases, an excellent resin sheet is attached.

  On the other hand, in recent years, in addition to the conventional flat display, development of a bendable display that can correspond to the shape of the installation place has been advanced.

  As a pressure-sensitive adhesive used for sticking a resin sheet on the surface of a display element, conventionally, a pressure-sensitive adhesive layer capable of forming a relatively high-hardness pressure-sensitive adhesive layer capable of preventing damage due to an external impact has been used. However, as described above, along with the development of a display that can be bent, the resin sheet and the adhesive for sealing them are not only excellent in transparency but also flexible enough to follow bending. Sex is required.

  On the other hand, in recent home appliances, a so-called touch panel is often installed as an operation panel. This touch panel is obtained by laminating a surface film on the surface of what is called a transparent conductive film (ITO electrode), and an adhesive may be used for fixing the surface film. Since the touch panel is usually operated by bringing a finger or a dedicated pen into contact with the surface of the touch panel, the surface film or adhesive layer constituting the touch panel is subjected to extreme pressure when touching it. It is necessary to have a level of flexibility that can follow the deformation of the surface film.

  Examples of the pressure-sensitive adhesive include a urethane prepolymer having a main chain skeleton of a polycarbonate diol having two or more (meth) acryloyloxy groups in one molecule, a monofunctional (meth) acrylate, and a polyfunctional (meth) acrylate. A photocurable adhesive composition containing a specific amount of a photopolymerization initiator is known (for example, see Patent Document 1).

  However, the adhesive layer formed by curing the photo-curable adhesive composition cannot sufficiently follow the bending as described above, and has a level of flexibility that can sufficiently absorb external impacts. It was hard to say that they were equipped.

  Moreover, what was previously processed into the sheet form is often used for the above-mentioned adhesive. Specifically, a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive is applied on a release-treated film such as polyethylene, and a base material made of polyethylene terephthalate or the like is placed on the coated surface, for example.

  However, when using the pressure-sensitive adhesive sheet as described above, when the release film is peeled off, a slight deformation or distortion or surface roughness of the pressure-sensitive adhesive layer is caused by an external force, and as a result, the transparency, etc. In some cases, the optical characteristics deteriorate.

JP 2000-38546 A

  The problem to be solved by the present invention is to have a level of flexibility that can sufficiently follow the bending of the base material and sufficiently absorb external impacts without losing excellent transparency, A pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having self-healing properties that can be recovered to a level close to the original excellent transparency even when the transparency is reduced due to deformation of the agent layer. Is to provide.

  The inventors of the present invention use a predetermined amount of a specific polymerizable unsaturated double bond-containing monomer in combination with a urethane resin having a conventionally known (meth) acryloyl group and a structure derived from a polycarbonate polyol. The inventors have found an adhesive having excellent flexibility without impairing excellent transparency, and have completed the present invention.

That is, the present invention provides a urethane resin (A) having a (meth) acryloyl group and a polycarbonate polyol-derived structure having 2 to 25 carbonate bonds per molecule, and
A pressure-sensitive adhesive comprising a polymerizable unsaturated double bond-containing monomer (B) capable of forming a homopolymer having a glass transition temperature of -20 ° C or lower,
The polymerizable unsaturated double bond-containing monomer (B) is one or more selected from the group consisting of alkoxy monoalkylene glycol (meth) acrylate and alkoxy polyalkylene glycol (meth) acrylate, and
Adhesive mass ratio [(A) / (B)] of the urethane resin (A) and the polymerizable unsaturated double bond-containing monomer (B) is in the range of 80/20 to 50/50. Provide the agent.

  The pressure-sensitive adhesive of the present invention can be used for manufacturing optical products such as bonding of a liquid crystal panel and a transparent cover of a liquid crystal display, bonding of a transparent conductive film (ITO electrode) and a surface film constituting a touch panel, and fixing of automobile interior members. It can be used in a wide range of applications such as the production of building materials such as soundproof walls and the bonding of acrylic glass for the purpose of shock absorption.

The best mode of the pressure-sensitive adhesive of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

  The pressure-sensitive adhesive of the present invention is a polymerizable unsaturated dimer capable of forming a urethane resin (A) having a (meth) acryloyl group and a structure derived from a polycarbonate polyol, and a homopolymer having a glass transition temperature of −20 ° C. or lower. A pressure-sensitive adhesive containing a heavy bond-containing monomer (B), wherein the polymerizable unsaturated double bond-containing monomer (B) is an alkoxy monoalkylene glycol (meth) acrylate and an alkoxy polyalkylene glycol ( 1 or 2 or more types selected from the group consisting of (meth) acrylates, and the blending mass ratio of the urethane resin (A) and the polymerizable unsaturated double bond-containing monomer (B) [(A ) / (B)] is in the range of 80/20 to 30/70.

  First, the urethane resin (A) used in the pressure-sensitive adhesive of the present invention will be described.

  The urethane resin (A) has a structure derived from a polycarbonate polyol together with a (meth) acryloyl group in the molecule.

  From the viewpoint of imparting the curability of the pressure-sensitive adhesive, it is essential that at least one (meth) acryloyl group is present in the molecule, but two or more are preferably present, and 2 to 5 are present. Particularly preferred.

  In addition, the structure derived from polycarbonate polyol has a characteristic (self-repairing property) that can recover a decrease in transparency due to distortion of the adhesive to a level close to the original excellent transparency by heating or the like. It is essential for imparting excellent tackiness. Specifically, the number of carbonate bonds of the polycarbonate polyol (a) is preferably 2 to 45, more preferably 2 to 25 per molecule.

As the urethane resin (A), it is preferable to use a resin having a number average molecular weight in the range of 800 to 6000. From the viewpoint of forming a pressure-sensitive adhesive layer having good substrate followability, the number average molecular weight is 1000 to 4000. It is more preferable to use those within the range.
Moreover, as said urethane resin (A), it is preferable to use what has a glass transition temperature of -60 degreeC-20 degreeC, when obtaining the adhesive which can form the adhesion layer provided with the favorable softness | flexibility. . In particular, when the pressure-sensitive adhesive of the present invention is used for the production of optical products, it is preferable to use a urethane resin having a glass transition temperature of preferably −10 to 20 ° C., more preferably 0 to 20 ° C. It is preferable for obtaining a pressure-sensitive adhesive capable of forming an excellent pressure-sensitive adhesive layer.

  The urethane resin (A) used in the pressure-sensitive adhesive of the present invention produces, for example, a urethane resin (c) having an isocyanate group at the molecular end by reacting a polyol containing a polycarbonate polyol (a) with a polyisocyanate, Next, it is produced by reacting this urethane resin (c) with a (meth) acrylic compound (d) having one hydroxyl group and one or more (meth) acryloyl groups in the molecule. Can do.

  Here, as the polycarbonate polyol (a), for example, 1,6-hexane carbonate diol, 1,4-cyclohexane carbonate diol, 1,6-hexane-1,5-heptane carbonate and the like are used.

  Polycarbonate polyol (a) is, for example, (i) a method of transesterifying a carbonate ester with an aliphatic or aliphatic cyclic structure-containing polyol, or (ii) a method of ring-opening a cyclic carbonate ester having an alkylene group. Etc. can be generated. Among these methods, it is preferable to use the polycarbonate polyol obtained by the method (i). Further, it is preferable to use a polycarbonate polyol having a number average molecular weight in the range of 400 to 4000, and a pressure-sensitive adhesive layer having a level of flexibility that can sufficiently follow the deformation of the substrate can be formed. More preferably, a polycarbonate diol in the range of 3000 is used.

  As the carbonic acid ester that can be used for the production of the polycarbonate polyol (a), for example, dimethyl carbonate, phosgene or the like is preferably used.

  As the aliphatic or aliphatic cyclic structure-containing polyol, it is preferable to use a diol. Examples of the diol include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, neo Pentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, cyclohexanedimethylol, 1,4-cyclohexanediol, etc. Used.

  Moreover, as cyclic carbonate which has an alkylene group, it is preferable to use a butylene carbonate etc., for example.

  As the polycarbonate polyol (a), it is preferable to use one having a hydroxyl value in the range of 25 to 300 KOHmg / g from the viewpoint of forming a flexible pressure-sensitive adhesive layer that can sufficiently follow deformation of the substrate. .

  Moreover, as a polyol used when producing | generating a urethane resin (A), other polyol can be used together as needed other than a polycarbonate polyol (a).

  Examples of other polyols include polyether polyols such as polyoxypropylene diol, polytetramethylene glycol, and polyoxymethylene diol, and polyester polyols that are condensates of polyhydric alcohols and polybasic carboxylic acids.

  When other polyols are used, the polycarbonate polyol (a) should be used in an amount of 90% by mass or more based on the total amount of polyol used in the production of the pressure-sensitive adhesive of the present invention. It is preferable in terms of imparting flexibility and self-healing that can recover a reduction in transparency due to distortion of the adhesive to a level close to the original excellent transparency by heating or the like.

  Further, as the polyisocyanate (b) capable of reacting with the polycarbonate polyol (a) or the like, diisocyanate is preferably used. For example, 2,4-tolylene diisocyanate, its isomer or a mixture of these isomers, hexamethylene diisocyanate , Isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, or tolidine diisocyanate is used. Among these, from the viewpoint of suppressing yellowing of the pressure-sensitive adhesive due to heat, it is more preferable to use an aliphatic or aliphatic cyclic structure-containing diisocyanate, and the polymerizable unsaturated monomer of the resulting urethane resin (A). It is particularly preferable to use isophorone diisocyanate, which is an isocyanate containing an aliphatic cyclic structure, in order to improve compatibility with (B), and as a result, to impart even more excellent transparency to the pressure-sensitive adhesive layer. .

  Examples of the (meth) acrylic compound (d) containing one hydroxyl group and one or more (meth) acryloyl groups in the molecule used for the production of the urethane resin (A) include 2- Methacrylates having one hydroxyl group such as hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate; polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate Mono (meth) acrylates of alcohols having two hydroxyl groups such as; having three or more hydroxyl groups such as di (meth) acrylate of tris (hydroxyethyl) isocyanuric acid, pentaerythritol tri (meth) acrylate, etc. Alcohol (meta Such as acrylates are used.

  As a method for producing the urethane resin (A), for example, a polyol containing a polycarbonate polyol (a) and a polyisocyanate (b) are contained in an isocyanate group (NCO) and a polyol (a) contained in the polyisocyanate (b). Reaction step (I) for producing a urethane resin (c) having an isocyanate group at the molecular terminal by reacting under the condition that the equivalent ratio with the hydroxyl group (OH) is in the range of [NCO / OH] = 1.25-2. ); And a urethane resin (c) having an isocyanate group and a (meth) acrylic compound (d), the hydroxyl group of the (meth) acrylic compound (d) is almost equal to the isocyanate group of the urethane resin (c). And a reaction step (II) in which the reaction is carried out under equivalent conditions.

It is preferable to perform reaction process (I), for example in the range of room temperature to about 100 degreeC by nitrogen atmosphere.
Moreover, although this reaction process (I) can also be performed under a non-solvent, the polymerizable unsaturated double bond containing monomer (B) mentioned later can also be used as a solvent as needed.
In the reaction step (I), a catalyst may be used as necessary.

Examples of the catalyst include organic titanium compounds such as tetrabutyl titanate, tetrapropyl titanate, and tetraethyl titanate; organotin compounds such as tin octylate, dibutyltin oxide, and dibutyltin dilaurate; Known catalysts such as acids and alkalis such as tin and stannous iodide can be used.
It is preferable that the addition amount of these catalysts is 10-10,000 ppm with respect to the total preparation amount of the polyol containing polyisocyanate (b) and polycarbonate polyol (a).

Moreover, it is preferable to perform reaction process (II) in the range of about room temperature-90 degreeC.
Moreover, although reaction process (II) can also be performed under a non-solvent, the polymerizable unsaturated double bond containing monomer (B) mentioned later can also be used as a solvent as needed.

  In the reaction step (II), those exemplified as the catalyst used in the reaction step (I) may be used as necessary.

  Moreover, in order to suppress the radical polymerization of the polymerizable unsaturated double bond of the (meth) acrylic compound (d), a radical polymerization inhibitor can be used as necessary.

As the radical polymerization inhibitor, for example, hydroquinone monomethyl ether, dt-butyl hydroquinone, pt-butyl catechol, phenothiazine and the like can be used.
The amount of the radical polymerization inhibitor used is preferably 10 to 10,000 ppm with respect to the total amount of the (meth) acrylic compound (d).

  Next, the polymerizable unsaturated double bond-containing monomer (B) used for the pressure-sensitive adhesive of the present invention will be described.

As the polymerizable unsaturated double bond-containing monomer (B), among the polymerizable unsaturated double bond-containing monomers that can be used for the production of a homopolymer whose glass transition temperature can be −20 ° C. or lower, alkoxy One type or two or more types selected from the group consisting of monoalkylene glycol (meth) acrylate and alkoxypolyalkylene glycol (meth) acrylate are used.
Here, the glass transition temperature of the homopolymer was determined by subjecting the homopolymer obtained by polymerizing the polymerizable unsaturated double bond-containing monomer (B) to DSC (differential scanning calorimeter, Seiko Inn, under a nitrogen atmosphere). Measured at −100 ° C. under a temperature rising rate of 5 ° C./min.

  The glass transition temperature is preferably as low as possible from the viewpoint of obtaining a flexible pressure-sensitive adhesive, but is preferably approximately −80 ° C. or higher.

As the polymerizable unsaturated double bond-containing monomer (B), it is essential to use a polymerizable unsaturated double bond-containing monomer capable of forming a homopolymer having the specific glass transition temperature. .
Here, instead of the polymerizable unsaturated double bond-containing monomer (B), the pressure-sensitive adhesive obtained by using isobornyl acrylate whose glass transition temperature of the homopolymer can be 90 ° C. It is not possible to provide a level of flexibility that can sufficiently absorb external shocks.
In addition, the pressure-sensitive adhesive obtained using benzyl acrylate which can have a glass transition temperature of 6 ° C. instead of the polymerizable unsaturated double bond-containing monomer (B) has good transparency to some extent. Although the pressure-sensitive adhesive layer can be formed, when the pressure-sensitive adhesive layer is bent to approximately 180 °, the transparency at the bent portion may be significantly reduced.
As the polymerizable unsaturated double bond-containing monomer (B), it is preferable to use a homopolymer having a glass transition temperature of −70 to −20 ° C. It is preferable to achieve both.

Moreover, as a polymerizable unsaturated double bond containing monomer (B), 1 type, or 2 or more types chosen from the group which consists of alkoxymonoalkylene glycol (meth) acrylate and alkoxy polyalkylene glycol (meth) acrylate is used. It is essential.
Here, instead of the polymerizable unsaturated double bond-containing monomer (B), the homopolymer has a glass transition temperature of −20 ° C. or lower, but has a carbon number of 12 such as lauryl (meth) acrylate. When group (meth) acrylate is used, the urethane resin (A) may not be dissolved in lauryl (meth) acrylate, and the transparency of the pressure-sensitive adhesive layer may be impaired.

Examples of the alkoxymonoalkylene glycol (meth) acrylate include a hydroxyl group having a hydroxyl group-containing (meth) acrylate such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, or hydroxybutyl (meth) acrylate as a methyl group or ethyl. It is preferable to use a monomer sealed with an alkyl group such as a group.
The alkoxypolyalkylene glycol (meth) acrylate is obtained by adding an alkylene oxide to a hydroxyl group-containing (meth) acrylate such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, or hydroxybutyl (meth) acrylate, for example. It is preferable to use a monomer in which the hydroxyl group of the resulting adduct is sealed with an alkyl group such as a methyl group or an ethyl group. The addition amount of the alkylene oxide is preferably in the range of 1 to 10 mol, more preferably in the range of 1 to 5 mol, with respect to 1 mol of the hydroxyl group of the hydroxyl group-containing (meth) acrylate.
In addition, “sealing the hydroxyl group with an alkyl group such as a methyl group or an ethyl group” means “substituting the hydrogen atom of the hydroxyl group with an alkyl group such as a methyl group or an ethyl group”.

For example, ethylene oxide, propylene oxide, butylene oxide, or tetrahydrofuran is preferably used as the alkylene oxide.
Specific examples of the polymerizable unsaturated double bond-containing monomer (B) include methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, and ethoxypropyl (meth) acrylate. , Methoxybutyl (meth) acrylate, ethoxybutyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, ethoxydipropylene glycol (meth) acrylate, methoxydibutylene Glycol (meth) acrylate, ethoxydibutylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethyleneglycol (Meth) acrylate, methoxy polypropylene glycol (meth) acrylate, ethoxy polypropylene glycol (meth) acrylate, methoxy polybutylene glycol (meth) acrylate, or the like can be used ethoxy polybutylene glycol (meth) acrylate. Among these, use of ethoxydiethylene glycol acrylate or methoxyethyl acrylate is particularly preferable because an adhesive having excellent flexibility, transparency, and accidental repairability of the transparency can be obtained.
As the alkoxy monoalkylene glycol (meth) acrylate and alkoxy polyalkylene glycol (meth) acrylate, using methoxyethyl acrylate or ethoxydiethylene glycol acrylate, even when the adhesive layer follows the bending of the substrate, This is very preferable because it is difficult to cause a decrease in transparency due to following.

  In addition, as the polymerizable unsaturated double bond-containing monomer (B), the use of a monomer having one polymerizable unsaturated double bond in the molecule exerts the effects of the present invention. Highly preferred.

  The pressure-sensitive adhesive of the present invention can be produced by mixing the urethane resin (A) and the polymerizable unsaturated double bond-containing monomer (B). Specifically, the urethane resin (A) It can manufacture by melt | dissolving in a polymerizable unsaturated double bond containing monomer (B).

The pressure-sensitive adhesive of the present invention has a blending mass ratio [(A) / (B)] of the urethane resin (A) and the polymerizable unsaturated double bond-containing monomer (B) of 80/20 to 30/70. It exists in the range, Preferably it exists in the range of 70 / 30-50 / 50.
If the adhesive mass ratio of the urethane resin (A) and the polymerizable unsaturated double bond-containing monomer (B) is adjusted to the above range, the transparency caused by the deformation of the adhesive layer, etc. Even when the reduction occurs, it is possible to exhibit self-repairing ability capable of recovering to a level close to the original excellent transparency.

  In the pressure-sensitive adhesive of the present invention, other components can be used as necessary in addition to those described above.

As said other component, other polymerizable unsaturated double bond containing monomers other than a polymerizable unsaturated double bond containing monomer (B) can be used together, for example.
Examples of the other polymerizable unsaturated double bond-containing monomer include phenoxyethyl acrylate, phenoxypropyl acrylate, phenoxydiethylene glycol acrylate, isodecyl (meth) acrylate, tridecyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2 -Ethylhexyl carbitol acrylate, isoamyl acrylate, acrylonitrile benzyl acrylate, dicyclooxyethyl acrylate, dicyclopentenyl acrylate, dicyclopentanyl acrylate, isobornyl acrylate and the like can be used.

  Moreover, as said other component, a hydroxyl-containing allyl ether compound can also be used together in order to prevent the hardening inhibition by the air of an adhesive.

  Examples of the hydroxyl group-containing allyl ether compound include ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, triethylene glycol monoallyl ether, polyethylene glycol monoallyl ether, propylene glycol monoallyl ether, dipropylene glycol monoallyl ether, and tripropylene. Glycol monoallyl ether, polypropylene glycol monoallyl ether, 1,2-butylene glycol monoallyl ether, 1,3-butylene glycol monoallyl ether, hexylene glycol monoallyl ether, octylene glycol monoallyl ether, trimethylolpropane diallyl ether Glyceryl diallyl ether, pentaerythritol triallyl ether, etc. It is used and polyhydric allyl ether compound of alcohol, it is preferable to use allyl ether compound having one hydroxyl group in the molecule.

As the other components, it is preferable to add a polymerization inhibitor. Examples of the polymerization inhibitor include trihydroquinone, hydroquinone, 1,4-naphthoquinone, parabenzoquinone, toluhydronone, p-tert- Butylcatechol, 2,6-tert-butyl-4-methylphenol and the like are used.
It is preferable that the compounding quantity of a polymerization inhibitor exists in the range of 10-1000 ppm in the adhesive of this invention.

  In addition, the pressure-sensitive adhesive of the present invention includes generally known polymerizable unsaturated monomers, unsaturated polyester resins, epoxy acrylate resins, polyurethane resins, acrylic resins, within a range not impairing the effects of the present invention. Alkyd resins, urea resins, melamine resins, polyvinyl acetate, vinyl acetate copolymers, polydiene elastomers, saturated polyester resins, saturated polyethers, celluloses and their derivatives, fats and oils, and other conventional natural products Also, ionic compounds such as synthetic polymer compounds, inorganic fillers of alkoxysilane condensates and antistatic agents can be added.

  The pressure-sensitive adhesive of the present invention can be cured by any curing method such as curing with active energy rays, heat curing using a peroxide, or room temperature curing using a peroxide and a reducing agent. Considering the case where it is used as an adhesive film, the adhesive of the present invention is preferably cured by ultraviolet irradiation in a nitrogen or air atmosphere from the viewpoint of productivity and thinning.

  When the pressure-sensitive adhesive of the present invention is cured by active energy rays, it is preferable to use a photopolymerization initiator as a curing agent.

  Examples of the photopolymerization initiator include benzophenones such as benzophenone, 4,4-bis (diethylamino) benzophenone, 2,4,6-trimethylbenzophenone, methyl orthobenzoylbenzoate, and 4-phenylbenzophenone; t-butylanthraquinone, 2 Anthraquinones such as ethyl anthraquinone; thioxanthones such as 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone; diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, Benzyldimethyl ketal, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino Acetophenones such as 1- (4-morpholinophenyl) -butanone; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis ( 2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, acylphosphine oxides such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, methylbenzoylformate; Bisacridinyl heptane; 9-phenylacridine and the like are used.

  When a photopolymerization initiator is used, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, 4-dimethylaminobenzoic acid as necessary A known photosensitizer such as amyl or 4-dimethylaminoacetophenone may be used.

  Further, when the pressure-sensitive adhesive of the present invention is heat-cured by using a peroxide, examples of the curing agent include diacyl peroxide-based, peroxyester-based, hydroperoxide-based, dialkyl peroxide-based, and ketone peroxide. Peroxides, peroxyketal, alkyl perester, and percarbonate are used.

  Further, when the pressure-sensitive adhesive of the present invention is cured at room temperature by using a peroxide and a reducing agent, an organic metal salt such as peroxide and cobalt naphthenate or cobalt octenoate, dimethylaniline, which is a curing accelerator, It is used in combination with an aromatic amine compound such as diethylaniline or paratoluidine.

The blending amount of a curing agent such as a photopolymerization initiator or a peroxide is preferably in the range of 0.1 to 10 parts by mass, more preferably 100 parts by mass with respect to the total amount of the pressure-sensitive adhesive of the present invention. 1 to 6 parts by mass.
Since the pressure-sensitive adhesive of the present invention can form a pressure-sensitive adhesive layer having a level of flexibility that can sufficiently follow the deformation of the substrate, the liquid crystal panel of the liquid crystal display and the transparent cover are bonded together, and the transparent conductive material constituting the touch panel Widely used in the manufacture of optical products such as bonding of film (ITO electrode) and surface film, fixing of automobile interior parts, manufacturing of building materials such as soundproof walls, and bonding of acrylic glass for the purpose of shock absorption It can be used. In particular, the pressure-sensitive adhesive of the present invention is suitable for use in the production of optical products such as liquid crystal displays and touch panels because it can form a pressure-sensitive adhesive layer that has both excellent flexibility and excellent transparency.

Next, the adhesive film of the present invention will be described.
The pressure-sensitive adhesive film of the present invention is usually one in which a pressure-sensitive adhesive layer is provided in advance on all or part of the surface of a substrate such as polyethylene terephthalate or glass, and a release film is provided on the surface of the pressure-sensitive adhesive layer. It is.

When using this pressure-sensitive adhesive film, the release film is usually peeled off, the pressure-sensitive adhesive layer is brought into contact with the adherend, and pressure-bonded.
When the release film is peeled off, the pressure-sensitive adhesive layer may be slightly deformed or distorted as described above, and the transparency of the pressure-sensitive adhesive layer may be reduced due to the deformation or the like.

  However, if the pressure-sensitive adhesive film of the present invention is left in a temperature environment of about 35 to 100 ° C. for about 1 to 3 hours, the deformation and the like are repaired, and a level close to the original excellent transparency. It is possible to recover to

  The pressure-sensitive adhesive film of the present invention is, for example, a polyethylene terephthalate obtained by applying a pressure-sensitive adhesive to a surface of a substrate such as glass or polyethylene terephthalate by a conventionally known method such as a roll coater and then performing a release treatment on the surface of the pressure-sensitive adhesive. It can manufacture by laminating the release film which consists of etc.

  The pressure-sensitive adhesive film obtained by such a method is exclusively bonded to a liquid crystal panel constituting a liquid crystal display and a transparent cover (protective film) on the surface, or a transparent conductive film (ITO electrode) constituting a touch panel is brought into contact with a finger or the like. It can be suitably used as an optical pressure-sensitive adhesive film for use in the production of optical products such as mobile phones and digital cameras, such as bonding with a surface film to be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

“Synthesis Example 1”
Preparation of polycarbonate skeleton-containing urethane resin (I) having acryloyl group Polycarbonate diol (trade name: UH) was added to a 2-liter four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser. -CARB50, manufactured by Ube Industries, Ltd., number average molecular weight: 500, number of carbonate bonds: 2-3, hydroxyl value: 224.4 KOHmg / g) was charged in 500 parts by mass, and isophorone diisocyanate (hereinafter abbreviated as “IPDI”). 444 mass parts was added, and it was made to react at 80 degreeC for 4 hours, suppressing heat_generation | fever.
The equivalent of the isocyanate group was 472, which was almost the same as the theoretical value when all the hydroxyl groups of the polycarbonate diol reacted with the isocyanate group of IPDI, and then stabilized, cooled to 40 ° C., 244 parts by mass of 2-hydroxyethyl acrylate was added, 0.037 parts by mass of a tin catalyst was added as a reaction promoting catalyst and reacted at 90 ° C. for 7 hours in an air atmosphere.
And after unreacted isocyanate group became 0.3 mass% or less, the hydroquinone 0.05 mass part was added and polycarbonate frame | skeleton containing urethane resin (I) which has an acryloyl group was obtained.

“Synthesis Example 2”
Preparation of polycarbonate skeleton-containing urethane resin (II) having acryloyl group Polycarbonate diol (trade name: UH-CARB100, manufactured by Ube Industries, number average molecular weight: 1000, number of carbonate bonds) in the same reactor as in Synthesis Example 1 : 6-7, hydroxyl value: 112.2 KOH mg / g) was added in an amount of 500 parts by mass, and then 222 parts by mass of IPDI was added, and the mixture was reacted at 80 ° C. for 4 hours while suppressing heat generation.
The equivalent of the isocyanate group is 732, which is almost the same as the theoretical value when all the hydroxyl groups of the polycarbonate diol have reacted with the isocyanate group of IPDI and stabilized, and then cooled to 40 ° C., and 122 parts by mass of 2-hydroxyethyl acrylate was added. 0.02 parts by mass of a tin catalyst was added as a reaction promoting catalyst and reacted at 90 ° C. for 5 hours in an air atmosphere.
And after the unreacted isocyanate group became 0.3 mass% or less, 0.049 mass part of hydroquinone was added, and polycarbonate skeleton containing urethane resin (II) which has an acryloyl group was obtained.

“Synthesis Example 3”
Preparation of polycarbonate skeleton-containing urethane resin (III) having acryloyl group Polycarbonate diol (trade name: T5652, manufactured by Asahi Kasei Co., Ltd., number average molecular weight: 2000, number of carbonate bonds: 13 to 13) 14, hydroxyl value: 56.1 KOHmg / g) was charged in an amount of 1000 parts by mass, and then 222 parts by mass of IPDI was added, and the mixture was reacted at 80 ° C. for 4 hours while suppressing heat generation.
The equivalent of the isocyanate group is 1222 which is almost the same as the theoretical value when all the hydroxyl groups of the polycarbonate diol have reacted with the isocyanate group of IPDI and stabilized, then cooled to 40 ° C., 122 parts by mass of 2-hydroxyethyl acrylate was added, 0.037 parts by mass of a tin catalyst was added as a reaction promoting catalyst, and the mixture was reacted at 90 ° C. for 5 hours in an air atmosphere.
And after the unreacted isocyanate group became 0.3 mass% or less, 0.049 mass part of hydroquinone was added, and the polycarbonate frame containing urethane resin (III) which has an acryloyl group was obtained.

“Synthesis Example 4”
Preparation of urethane resin (IV) having acryloyl group but not containing polycarbonate skeleton Polypropylene glycol (trade name: Actol Diol-700, manufactured by Mitsui Chemicals Polyurethanes, number average molecular weight: 700, number of carbonate bonds: 0, hydroxyl value : 160.3 KOHmg / g) and 444 parts by mass of IPDI were charged and reacted in a nitrogen atmosphere at 80 ° C. for 5 hours while suppressing heat generation.
After confirming that the equivalent of the isocyanate group was 572, which was almost the same as the theoretical value when all the hydroxyl groups of polypropylene glycol reacted with the isocyanate group of IPDI, the mixture was cooled to 30 ° C. and 2-hydroxyethyl acrylate was converted to 244 Mass parts were added and reacted at 80 ° C. for 4 hours under a nitrogen atmosphere.
And after the unreacted isocyanate group became 0.3 mass% or less, 0.08 mass part of hydroquinone was added, and urethane resin (IV) which has an acryloyl group but does not contain a polycarbonate skeleton was obtained.

"Example 1"
50 parts by mass of the polycarbonate skeleton-containing urethane resin (I) having an acryloyl group obtained in Synthesis Example 1 and 50 parts by mass of ethoxydiethylene glycol acrylate (homopolymer has a glass transition temperature of −70 ° C.) The mixture was dissolved by stirring and mixing to obtain a uniform solution, thereby obtaining a pressure-sensitive adhesive.

"Examples 2-8 and Comparative Examples 1-6"
Urethane resins (I) to (IV) obtained in Synthesis Examples 1 to 4, and ethoxydiethylene glycol acrylate (a homopolymer glass transition temperature of −70 ° C.) as a polymerizable unsaturated double bond-containing monomer, methoxyethyl Acrylate (homopolymer has a glass transition temperature of −50 ° C.), benzyl acrylate (homopolymer has a glass transition temperature of 6 ° C.), methoxypolyethylene glycol monoacrylate (the number of ethylene oxide structure repeats is 9, and the homopolymer has a glass transition temperature of −71 ° C.), phenoxyethyl acrylate (homopolymer has a glass transition temperature of −22 ° C.), or styrene (homopolymer has a glass transition temperature of 100 ° C.) according to the composition described in Tables 1-4. Except for the above, an adhesive was obtained in the same manner as in Example 1.

[Measurement of glass transition temperature and elongation of cured adhesives]
In each of the pressure-sensitive adhesives obtained in Examples 1 to 8 and Comparative Examples 1 to 6, 3% by mass of Irgacure 184 (manufactured by Ciba Japan) was dissolved, and release cellophane (trade name: PHT ( (Thickness 350 μm), manufactured by Futamura Chemical Co., Ltd.) to a thickness of about 0.1 mm, and using a UV lamp 120W metal halide lamp (UV irradiation amount 500 mJ / cm ^{2 1} pass) on the coated surface in a nitrogen atmosphere. The pressure-sensitive adhesive layer was obtained by irradiating with ultraviolet rays and curing, and removing the release film.

The glass transition temperature of the obtained adhesive layer was measured using DMS-6100 of Seiko Instruments Inc. using a tensile unit. The frequency was 1 Hz, and measurement was performed at a rate of temperature increase from -100 ° C to 5 ° C / min. Moreover, the glass transition temperature was calculated | required by the onset temperature of E '(dynamic storage elastic modulus). As a result of the measurement, a glass transition temperature of 20 ° C. or lower was evaluated as having flexibility.
The elongation was measured using an autograph AG-I manufactured by Shimadzu Corporation (test piece size: width 10 mm, length 50 mm, chuck interval: 20 mm, test speed: 4 mm / min).

[Transparency evaluation method]
In each of the pressure-sensitive adhesives obtained in Examples 1 to 5 and Comparative Examples 1 and 2, 3% by mass of Irgacure 184 (manufactured by Ciba Japan Co., Ltd.) was dissolved, and the resulting solution had a thickness based on JIS R3202. It was applied to the surface of a 2 mm glass plate (haze: 0.58) to a thickness of about 0.05 mm, and under a nitrogen atmosphere, one UV lamp 120W metal halide lamp (UV irradiation amount 500 mJ / cm ^{2 1} pass) was applied to the coated surface. A pressure-sensitive adhesive layer was obtained by irradiating with UV rays and curing.

The haze of the obtained pressure-sensitive adhesive layer was measured using a haze meter (trade name: NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).
If the haze is approximately 0.7 or less, it can be said that the haze is practically sufficient.

[Method for evaluating transparency self-healing]
After measuring the haze of the pressure-sensitive adhesive layer by the above-described method, the surface of the pressure-sensitive adhesive layer after the measurement is rubbed 20 times with a load of 500 g using JK Y PARISH 150-S (manufactured by Nippon Paper Crecia Co., Ltd.) and after the rubbing. The haze of the pressure-sensitive adhesive layer was measured by the same method as described above. Those in which the pressure-sensitive adhesive layer was removed from the glass plate by rubbing were regarded as “impossible to measure”.

Next, the pressure-sensitive adhesive layer after the measurement of the haze was heated by being left in a thermostat at 50 ° C. for about 1 hour.
Thereafter, the haze of the pressure-sensitive adhesive layer cooled to room temperature was measured by the same method as described above.

  The evaluation of transparency self-healing is performed based on the value calculated by the following formula (1), and the value of 10% or less is a pressure-sensitive adhesive layer having transparency self-healing. evaluated.

[{(Haze of the pressure-sensitive adhesive layer after the heating treatment) − (Haze of the pressure-sensitive adhesive layer before the rubbing)} / {(Haze of the pressure-sensitive adhesive layer after the rubbing) − (Before the rubbing Haze of adhesive layer)}] × 100 (1)

[Method for evaluating transparency of bent part]
In each of the pressure-sensitive adhesives obtained in Examples 1 to 8 and Comparative Examples 1 to 6, 3% by mass of Irgacure 184 (manufactured by Ciba Japan Co., Ltd.) was dissolved. : Applied to the surface of PHT (thickness 350 μm, manufactured by Futamura Chemical Co., Ltd.) to a thickness of about 0.1 mm, and under a nitrogen atmosphere, one UV lamp 120W metal halide lamp (UV irradiation amount 500 mJ / cm ^{2 1} pass) on the coated surface ) Was irradiated with ultraviolet rays to be cured, and the pressure-sensitive adhesive layer was obtained by removing the release film.

  The haze of the obtained pressure-sensitive adhesive layer was measured using a haze meter (trade name: NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

The pressure-sensitive adhesive layer after measuring the haze is sandwiched between unadhesive untreated surfaces of a PET film (trade name: A4100 (thickness: 100 μm), manufactured by Toyobo Co., Ltd.) made of polyethylene terephthalate, and PET is used to crease the pressure-sensitive adhesive layer. The film was folded in half, and the press pressure was 0.5 MPa. s for 15 seconds.
After pressing, the haze of the crease portion of the pressure-sensitive adhesive layer was measured. In addition, since the curing of the pressure-sensitive adhesive layer does not proceed sufficiently and is in a paste form, the pressure-sensitive adhesive layer was brought into close contact by the pressure bonding by the hand press, and a crease could not be formed was `` not measurable '' did.

When the difference between the haze of the pressure-sensitive adhesive layer at the crease portion and the haze of the pressure-sensitive adhesive layer before crease was 2 or less, it was evaluated that the bent portion had good transparency.
[Method for evaluating adhesive strength]
A PET film (trade name) made of polyethylene terephthalate prepared by dissolving 3% by mass of Irgacure 184 (manufactured by Ciba Japan) in each of the pressure-sensitive adhesives obtained in Examples 1 to 8 and Comparative Examples 1 to 6. : A4100 (thickness 100 μm), applied to an easy-adhesion treated surface of Toyobo Co., Ltd. so as to have a thickness of about 0.1 mm, and under a nitrogen atmosphere, one UV lamp 120W metal halide (UV irradiation amount 500 mJ / cm) on the coated surface ^The adhesive film was obtained by irradiating with ultraviolet rays using ^{2 1} pass) and curing.
The pressure-sensitive adhesive film is cut to a width of 25 mm, the pressure-sensitive adhesive film is placed on the surface of a mirror-finished SUS304 steel plate, and a 2 kg rubber roller is reciprocated once on the pressure-sensitive adhesive film to laminate them. Got.
After 20 minutes from the press-bonding, the adhesive strength was measured by a 180 degree peeling method (test speed: 300 mm / min) of the laminate using an autograph AG-I manufactured by Shimadzu Corporation. When the adhesive strength was 5 N / 25 mm or more, it was judged that there was adhesive strength.

Claims (12)

A urethane resin (A) having a (meth) acryloyl group and a structure derived from a polycarbonate polyol having 2 to 25 carbonate bonds per molecule, and
A pressure-sensitive adhesive comprising a polymerizable unsaturated double bond-containing monomer (B) capable of forming a homopolymer having a glass transition temperature of -20 ° C or lower,
The polymerizable unsaturated double bond-containing monomer (B) is one or more selected from the group consisting of alkoxy monoalkylene glycol (meth) acrylate and alkoxy polyalkylene glycol (meth) acrylate, and
The blending mass ratio [(A) / (B)] of the urethane resin (A) and the polymerizable unsaturated double bond-containing monomer (B) is in the range of 80/20 to 50/50. Adhesive characterized by.   The pressure-sensitive adhesive according to claim 1, wherein the structure derived from the polycarbonate polyol is a structure derived from 1,6-hexane carbonate diol.   The pressure-sensitive adhesive according to claim 1 or 2, wherein the structure derived from the polycarbonate polyol is a structure derived from a polycarbonate polyol having a hydroxyl value of 25 to 300 KOHmg / g.   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the ratio of the polycarbonate polyol used is 90% by mass or more based on the total amount of the polyol used for the production of the pressure-sensitive adhesive of the present invention.   The pressure-sensitive adhesive according to claim 1, wherein the urethane resin (A) has a glass transition temperature of -60 to 20 ° C. The urethane resin (A) is
A polycarbonate polyol (a) is produced by reacting a carbonate with an aliphatic or aliphatic cyclic structure-containing polyol,
The polycarbonate polyol (a) and the polyisocyanate (b) are reacted to produce a urethane resin (c) having an isocyanate group at the molecular end,
The urethane resin (c) having an isocyanate group at the molecular terminal is reacted with a (meth) acrylic compound (d) containing one hydroxyl group and one or more (meth) acryloyl groups in the molecule. The pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive is produced.   The polymerizable unsaturated double bond-containing monomer (B) is a monomer in which the hydroxyl group of hydroxyethyl (meth) acrylate is sealed with a methyl group or an ethyl group, or 1 in hydroxyethyl (meth) acrylate. The pressure-sensitive adhesive according to claim 1, which is a monomer in which a hydroxyl group of an adduct obtained by adding 10 mol of ethylene oxide or propylene oxide is sealed with a methyl group or an ethyl group.   The pressure-sensitive adhesive according to claim 1, wherein the polymerizable unsaturated double bond-containing monomer (B) is at least one selected from the group consisting of ethoxydiethylene glycol (meth) acrylate and methoxyethyl acrylate.   The pressure-sensitive adhesive according to claim 6, wherein the polycarbonate polyol (a) is a polycarbonate diol having a number average molecular weight of 400 to 4000.   The adhesive film in which the adhesive layer which consists of an adhesive of any one of Claims 1-9 was provided on the base material.   The pressure-sensitive adhesive film according to claim 10, which is used for bonding a liquid crystal panel surface or a transparent conductive film surface and a protective film.   The laminated body which has the adhesive layer formed using the adhesive in any one of Claims 1-9 on the liquid crystal panel surface or the transparent conductive film surface, and the protective film laminated | stacked on the surface of this adhesive layer .