JP2009079203A - Pressure-sensitive adhesive composition, pressure-sensitive adhesive product and display using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive composition superior in applicability, transparency, an adhesive property (especially, the adhesive property at a low temperature), anti-foaming property, anti-peeling property, further superior in corrosion-resistance. <P>SOLUTION: The pressure sensitive-adhesive composition comprises an acrylic polymer having a weight-average molecular weight of 400,000 to 1,600,000 and a cross-linking agent and comprising an alkoxyalkyl acrylate (component A) and an acrylic monomer (component B) having a cross-linkable functional group as monomer components, and is characterized in that a content of the component A is 45 to 99.5 pts.wt. per 100 pts.wt. of all of monomer components constituting the acrylic polymer and a content of the component B is 0.5 to 4.5 pts.wt. and the monomer component constituting the acrylic polymer is essentially free of a carboxy group-containing monomer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acrylic pressure-sensitive adhesive composition. Specifically, it is excellent in adhesion to glass and acrylic, polycarbonate, polyethylene terephthalate (PET) and other transparent plastics, and has excellent resistance to foaming / peeling off, transparency, and coatability, and especially does not cause corrosion on metal thin films. Related to things. Moreover, it is related with the adhesive product which apply | coated this adhesive composition, and the display which bonded this adhesive product.

  In recent years, flat panel displays (FPDs) such as liquid crystal displays (LCDs) have been widely used. FPD is manufactured by laminating optical films having various functions via pressure-sensitive adhesives (pressure-sensitive adhesives). In these applications, adhesives are required to have excellent reliability, such as adhesiveness and transparency, as well as properties that do not cause foaming or peeling under high temperature or high humidity environment (foam resistance / peeling resistance). It is done.

  Conventionally, as a technique for improving the anti-foaming / peeling property under high temperature and high humidity environment, the homopolymer contains a monomer exhibiting a high glass transition temperature (Tg) (high Tg monomer) and a functional group such as a carboxyl group. There are known techniques for increasing the Tg of the pressure-sensitive adhesive by copolymerizing monomers or adding oligomers (low molecular weight polymers).

  For example, there is known a pressure-sensitive adhesive composition having excellent adhesion and foaming resistance to plastics at normal and high temperatures, comprising a polymer containing a carboxyl group-containing monomer as a constituent and an oligomer containing an amino group-containing monomer as a constituent. (See Patent Document 1). Also, a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 2.5 million and a (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 5,000 to 500,000 are mixed at a specific weight ratio. Thus, a pressure-sensitive adhesive composition in which either (A) or (B) has a nitrogen-containing functional group is known (see Patent Document 2). Furthermore, 100 parts by weight of an adhesive polymer obtained by copolymerizing an alkoxyalkyl ester of (meth) acrylic acid and a carboxyl group-containing monomer thereto, an alkyl methacrylate, a cycloalkyl methacrylate, a benzyl methacrylate Alternatively, 5 to 40 parts by weight of a low molecular weight polymer obtained by copolymerizing one or more monomers selected from styrene as a main component and an amino group or amide group-containing monomer, and a crosslinking agent 0.001 to 2 A pressure-sensitive adhesive composition containing 0.0 part by weight and a pressure-sensitive adhesive sheet using the same are known (see Patent Document 3).

  However, these pressure-sensitive adhesive compositions have a problem that adhesive properties under low temperature and high-speed conditions are lowered by increasing the Tg of the pressure-sensitive adhesive. Further, the pressure-sensitive adhesive composition containing a carboxyl group-containing monomer has a problem that the corrosion resistance performance when applied to a metal thin film (including a metal oxide thin film) is insufficient. In other words, it has not been possible to obtain an excellent pressure-sensitive adhesive composition that achieves a high level of all properties such as anti-foaming / peeling resistance in a high-temperature and high-humidity environment, adhesive properties in the low-temperature region, and corrosion resistance. It is.

Japanese Patent No. 3516035 JP 2001-89731 A JP 2002-327160 A

  An object of the present invention is to provide a pressure-sensitive adhesive composition which is excellent in coating property, adhesiveness, transparency, foam resistance / peeling resistance and excellent in corrosion resistance. Furthermore, it is providing the adhesive product and display with high reliability using the same.

  Also, depending on the application, there may be strict requirements for suppressing yellowing of the pressure sensitive adhesive. For example, when an aromatic isocyanate compound is used as a crosslinking agent, yellowing becomes a problem and countermeasures are required. There is a case. As a method for suppressing such yellowing, it is effective to use an aliphatic isocyanate cross-linking agent, but in such a case, the cross-linking speed becomes very slow, which may cause a problem in productivity. all right. In general pressure-sensitive adhesive sheets, it is possible to promote the crosslinking reaction by heating, but since there are strict appearance requirements for display applications, the method of promoting crosslinking by heating that is easy to generate dents and promote It may be difficult to use.

  Accordingly, another object of the present invention is to provide a pressure-sensitive adhesive composition excellent in yellowing resistance and productivity, and a pressure-sensitive adhesive product and display using the same.

  As a result of intensive studies to achieve the above object, the present inventors have made it possible to take a crosslinked structure of an acrylic polymer having a specific molecular weight mainly composed of an alkoxyalkyl acrylate, thereby containing a carboxyl group such as acrylic acid. The present inventors have found that a pressure-sensitive adhesive composition satisfying anti-foaming / peeling properties at high temperatures can be obtained without containing a monomer component, and the present invention has been completed.

  In addition, by using a specific amount of an aliphatic isocyanate cross-linking agent and an amine-based compound containing a plurality of hydroxyl groups, it is possible to suppress yellowing and to increase the productivity even when crosslinking is not accelerated by heating. It was found that an excellent pressure-sensitive adhesive composition was obtained.

  That is, the present invention is an acrylic type having a weight average molecular weight of 400,000 to 1.6 million comprising an alkoxyalkyl acrylate (component A) and an acrylic monomer having a crosslinkable functional group (component B) as essential monomer components. A pressure-sensitive adhesive composition containing a polymer and a crosslinking agent, wherein the content of component A is 45 to 99.5 parts by weight and the content of component B is 0.5 with respect to 100 parts by weight of all monomer components constituting the acrylic polymer. The pressure-sensitive adhesive composition is characterized by being substantially 4.5 parts by weight and substantially free of a carboxyl group-containing monomer in the monomer component constituting the acrylic polymer.

  Furthermore, the present invention provides an acrylic system having a weight average molecular weight of 400,000 to 1.6 million, comprising an alkoxyalkyl acrylate (component A) and an acrylic monomer having a crosslinkable functional group (component B) as essential monomer components. A pressure-sensitive adhesive composition comprising 0.01 to 3.0 parts by weight of an aliphatic isocyanate crosslinking agent and 0.01 to 5.0 parts by weight of an amine compound containing a plurality of hydroxyl groups with respect to 100 parts by weight of the polymer. The content of component A is 45 to 99.5 parts by weight and the content of component B is 0.5 to 4.5 parts by weight with respect to 100 parts by weight of all monomer components constituting the acrylic polymer. The above-mentioned pressure-sensitive adhesive composition is characterized in that the monomer component constituting the polymer is substantially free of a carboxyl group-containing monomer.

  Furthermore, this invention provides the said adhesive composition whose component B is an acryl-type monomer which has a hydroxyl group.

  Furthermore, the present invention provides the pressure-sensitive adhesive composition as described above, wherein the gel fraction after the cross-linking structure is 40 to 80%.

  Moreover, this invention provides the adhesive product which apply | coated the said adhesive composition.

  Moreover, this invention provides the display using the said adhesive product.

According to the pressure-sensitive adhesive composition of the present invention, since it has the above-described configuration, it has excellent coating properties, adhesiveness (particularly low-temperature adhesive properties), transparency, and resistance to foaming / peeling. When used for adhesion of optical members used in the above, optical properties such as visibility of these products can be improved. In addition, since it does not cause corrosion on metal thin films (including metal oxide thin films), it can be used in a portion where a film formed with a metal thin film such as an ITO (indium tin oxide) film is laminated. .
Furthermore, by using a specific amount of an aliphatic isocyanate cross-linking agent and an amine compound containing a plurality of hydroxyl groups, productivity is improved even when yellowing resistance and heating are not performed. Can be suitably used for severe applications.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention comprises an acrylic polymer and a crosslinking agent as essential components.

  The acrylic polymer used in the pressure-sensitive adhesive composition of the present invention is a polymer composed mainly of an acrylic acid alkoxyalkyl ester (alkoxyalkyl acrylate) (hereinafter sometimes referred to as “component A”). . In addition to the monomer main component, an acrylic monomer having a crosslinkable functional group (excluding a carboxyl group) (hereinafter sometimes referred to as “component B”) is included as an essential copolymerization monomer component. Other monomer components may be used as necessary. In addition, the monomer containing a carboxyl group is not substantially contained as a monomer component.

  The alkoxyalkyl acrylate (component A) is not particularly limited. For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methoxytriethylene glycol acrylate, 3-methoxypropyl acrylate, 3-acrylate acrylate Examples include ethoxypropyl, 4-methoxybutyl acrylate, 4-ethoxybutyl acrylate, and the like. The said component A can be used individually or in combination of 2 or more types.

  In the acrylic polymer, the monomer ratio of Component A, which is the main monomer component, is 45 to 99.5 parts by weight, preferably 50 to 80 parts by weight, based on 100 parts by weight of all monomer components. When the content of component A is less than 45 parts by weight in all the monomer components, the foam resistance / peeling resistance becomes insufficient. On the other hand, when it exceeds 99.5 parts by weight, the content of component B is lowered, the cross-linking structure in the polymer is insufficient, and the foaming resistance and peeling resistance are insufficient. In addition, the said monomer ratio says the ratio (blending ratio) of the preparation amount of each monomer component at the time of manufacturing an acrylic polymer. The same applies to other monomer ratios and monomer contents.

  The crosslinkable functional group in the acrylic monomer having the crosslinkable functional group (component B) is not particularly limited as long as it is a functional group other than a carboxyl group and can be crosslinkable with a crosslinking agent described later. Although not mentioned, for example, glycidyl group, amino group, N-methylolamide group, hydroxyl group and the like can be mentioned. As the component B, specifically, glycidyl (meth) acrylate, glycidylmethyl (meth) acrylate as monomers having a glycidyl group; N, N-dimethylaminoethyl (meth) acrylate, N as monomers having an amino group, N , N-diethylaminoethyl (meth) acrylate; N-methylolacrylamide as a monomer having an N-methylolamide group; 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4 as monomers having a hydroxyl group, -Hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, etc. are mentioned. Among them, a monomer having an N-methylolamide group and an acrylic monomer having a hydroxyl group are preferable, and an acrylic monomer having a hydroxyl group is more preferable, and 2-hydroxyethyl acrylate (2HEA) and 4-hydroxybutyl acrylate are particularly preferable. (4HBA), 3-hydroxypropyl acrylate (3HPA), 6-hydroxyhexyl acrylate (6HHA). “(Meth) acryl” means “acryl” and / or “methacryl”. The same applies to the following.

  In the acrylic polymer, the monomer ratio of Component B is 0.5 to 4.5 parts by weight, preferably 0.5 to 3.0 parts by weight, more preferably 0 to 100 parts by weight of all monomer components. 0.5 to 2.0 parts by weight. When the content of component B is less than 0.5 parts by weight in all monomer components, the cross-linking structure into the polymer becomes insufficient and foaming tends to occur. On the other hand, if it exceeds 4.5 parts by weight, the cross-linked structure becomes too dense and easily peels off.

  The acrylic polymer does not substantially contain a monomer containing a carboxyl group as a monomer component. Incidentally, “substantially free” means that it is not actively blended unless it is inevitably mixed. Specifically, 0.05 wt. Less than 0.01 part by weight, preferably less than 0.01 part by weight, more preferably less than 0.001 part by weight. When a carboxyl group-containing monomer is included, the corrosion resistance against the metal thin film is reduced (for example, the conductive performance of the ITO film is reduced). Examples of the carboxyl group-containing monomer include acrylic acid (AA), methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. In addition, acid anhydrides of these carboxyl group-containing monomers (for example, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride) are also included as carboxyl group-containing monomers.

  In the acrylic polymer, the other monomer component used in addition to the component A and the component B includes (meth) acrylic acid alkyl esters having an alkyl group having 1 to 12 carbon atoms, such as methyl (meth) acrylate, (Meth) ethyl acrylate, (meth) acrylic acid n-butyl, (meth) acrylic acid isobutyl, (meth) acrylic acid sec-butyl, (meth) acrylic acid t-butyl, (meth) acrylic acid pentyl, (meta ) Isopentyl acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( (Meth) nonyl acrylate, isononyl (meth) acrylate, decyl (meth) acrylate (Meth) acrylate, isodecyl (meth) acrylate, undecyl and the like (meth) dodecyl acrylate. In addition, methacrylic acid alkoxyalkyl esters such as methoxyethyl methacrylate and ethoxyethyl methacrylate; polyfunctional monomers such as triethylene glycol diacrylate, ethylene glycol dimethacrylate and trimethylolpropane tri (meth) acrylate; vinyl acetate and styrene And cyclohexyl (meth) acrylate.

  Among the above-mentioned other monomer components, from the viewpoint of keeping the glass transition temperature (Tg) of the acrylic polymer low, monomers having a Tg of 0 ° C. or less when homopolymers are preferable, and more preferably, the Tg is − It is a monomer of 40 ° C. or lower. For example, 2-ethylhexyl acrylate (2EHA), butyl acrylate (BA), and the like are preferable.

  The acrylic polymer can be prepared by a known or conventional polymerization method. Examples of the polymerization method of the acrylic polymer include a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a polymerization method by ultraviolet irradiation, and the like. In terms of transparency, water resistance, cost, etc., the solution polymerization method, UV A polymerization method is preferred, and a solution polymerization method is particularly preferred.

  The polymerization initiator used in the solution polymerization of the acrylic polymer is not particularly limited and can be appropriately selected from known or commonly used ones. For example, 2,2′-azobisisobutyronitrile is used. 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile) ), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2,4,4-trimethylpentane), dimethyl-2,2′-azobis (2-methylpropionate) Azo polymerization initiators such as: benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, di Peroxide-based polymerization initiators such as mill peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, etc. An oil-soluble polymerization initiator is preferably exemplified. A polymerization initiator can be used individually or in combination of 2 or more types. The usage-amount of a polymerization initiator should just be a normal usage-amount, for example, can be selected from the range of about 0.01-1 weight part with respect to 100 weight part of all the monomer components.

  In solution polymerization, various common solvents can be used. Examples of such solvents include 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 and methylcyclohexane Organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. A solvent can be used individually or in combination of 2 or more types.

  The weight average molecular weight (hereinafter sometimes simply referred to as molecular weight) of the acrylic polymer is 400,000 or more and 1.6 million or less (400,000 to 1.6 million), preferably 600,000 to 1,200,000, more preferably 600,000 to One million. When the weight average molecular weight of the acrylic polymer is less than 400,000, the adhesive force and cohesive force required as an adhesive cannot be obtained, and the foaming resistance and peeling resistance are insufficient. On the other hand, when it exceeds 1.6 million, Problems such as poor coating properties due to an increase in the viscosity of the adhesive occur.

The weight average molecular weight (Mw) can be measured by a gel permeation chromatograph (GPC) method. More specifically, as a GPC measuring device, the product name “HLC-8120GPC” (manufactured by Tosoh Corporation) can be used to measure and obtain a polystyrene-converted value under the following GPC measurement conditions.
GPC measurement conditions-Sample concentration: 0.2 wt% (tetrahydrofuran solution)
Sample injection volume: 10 μl
・ Eluent: Tetrahydrofuran (THF)
・ Flow rate (flow velocity): 0.6 mL / min
Column temperature (measurement temperature): 40 ° C
Column: Trade name “TSKgelSuperHM-H / H4000 / H3000 / H2000” (manufactured by Tosoh Corporation)
・ Detector: Differential refractometer (RI)

  The weight average molecular weight of the acrylic polymer can be controlled by the type of polymerization initiator, the amount of the polymerization initiator used, the temperature and time during polymerization, the monomer concentration, the monomer dropping rate, and the like.

The glass transition temperature (Tg) of the acrylic polymer is from the viewpoint of improving the adhesion characteristics at low temperatures and the characteristics at high speed (for example, the characteristics that do not cause peeling when the bonded structure is dropped (drop impact)). -40 to -70 ° C is preferable, and -50 to -70 ° C is more preferable. In addition, Tg of the said acrylic polymer is a glass transition temperature (theoretical value) represented by a following formula.
1 / Tg = W ₁ / Tg ₁ + W ₂ / Tg ₂ +... + W _n / Tg _n
In the above formula, Tg is the glass transition temperature of the acrylic polymer (unit: K), Tg _n is the glass transition temperature of the homopolymer of the monomer n (unit: K), the W _n represents the weight fraction of monomer n.

  The storage elastic modulus at 80 ° C. of the acrylic polymer is preferably 0.01 MPa or more, more preferably 0.03 MPa or more. The storage elastic modulus was measured under the condition of a frequency of 1 Hz using an “Advanced Rheometric Expansion System (ARES)” manufactured by Rheometric Scientific in which an adhesive layer was laminated to a thickness of about 1.5 mm. The measurement was performed in the range of −70 to 200 ° C. at a temperature rising rate of 5 ° C./min.

  As the crosslinking agent used in the pressure-sensitive adhesive composition of the present invention, conventionally known crosslinking agents can be widely used. Depending on the functional group of Component B, a multifunctional melamine compound, a multifunctional epoxy compound, a multifunctional isocyanate compound can be used. It can select suitably from etc. and can be used. A crosslinking agent can be used individually or in mixture of 2 or more types. In the present invention, by using a cross-linking agent, a cross-linking structure is formed, and a balance between foam resistance and peeling resistance is achieved.

  Examples of the polyfunctional melamine compound include methylated trimethylol melamine and butylated hexamethylol melamine. Moreover, as a polyfunctional epoxy compound, diglycidyl aniline, glycerol diglycidyl ether, etc. are mentioned, for example. Furthermore, examples of the polyfunctional isocyanate compound include tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), polymethylene polyphenyl isocyanate, diphenylmethane diisocyanate, a reaction product of trimethylolpropane and tolylene diisocyanate, Examples include ether polyisocyanate and polyester polyisocyanate. Among these, it is preferable to use a monomer containing a hydroxyl group as Component B and to use a polyfunctional isocyanate compound (isocyanate crosslinking agent) as a crosslinking agent.

  Among these, it is preferable to use an aliphatic isocyanate crosslinking agent as a crosslinking agent, particularly from the viewpoint of improving yellowing resistance (yellowing deterrence). As the aliphatic isocyanate crosslinking agent, conventionally known ones can be widely used. For example, 1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, Preferable examples include 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Among them, it is preferable to use a monomer containing a hydroxyl group as Component B and to use hexamethylene diisocyanate (1,6-hexamethylene diisocyanate) (including a reaction product using HDI) as a crosslinking agent.

  The amount of the crosslinking agent used is not particularly limited. For example, it is preferably 0.01 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, more preferably 100 parts by weight of the acrylic polymer. Preferably it is 0.1-3 weight part, Most preferably, it is 0.1-1.0 weight part.

  In the pressure-sensitive adhesive composition of the present invention, an amine compound containing a plurality of hydroxyl groups can be used in order to accelerate the crosslinking reaction. When an aliphatic isocyanate cross-linking agent is used as the cross-linking agent, it is particularly preferably used in combination from the viewpoint of maintaining productivity (particularly, the cross-linking reaction proceeds quickly without promoting cross-linking by heating). The amine compound containing a plurality of hydroxyl groups is not particularly limited as long as it is an amine compound having at least two hydroxyl groups (alcoholic hydroxyl groups) in the molecule. In the amine compound, the number of nitrogen atoms contained in the molecule is not particularly limited. The amine compound containing a plurality of hydroxyl groups may be used alone or in combination of two or more.

  Specific examples of the amine compound containing a plurality of hydroxyl groups include, for example, diethanolamine, dipropanolamine, diisopropanolamine, N-methyl as amine compounds having one nitrogen atom in the molecule. Dialcohol amines such as diethanolamine, N-methyldiisopropanolamine, N-ethyldiethanolamine, N-ethyldiisopropanolamine, N-butyldiethanolamine, N-butyldiisopropanolamine; triethanolamine, tripropanolamine, triisopropanolamine Trialcoholamines such as

  Moreover, as an amine compound which has two nitrogen atoms in a molecule | numerator, an amine compound as shown by following formula (I) is mentioned.

In the above formula (I), R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or [— (R ⁵ O) _m (R ⁶ O) _n —H]. . Here, R ⁵ and R ⁶ are different and each represents an alkylene group. m and n are integers of 0 or more, and do not become 0 at the same time. Further, at least two of R ¹ , R ² , R ³ and R ⁴ are [— (R ⁵ O) _m (R ⁶ O) _n —H]. Further, X represents a divalent hydrocarbon group, and p is an integer of 1 or more.

In the above formula (I), the alkylene group of R ⁵ and R ⁶ is, for example, about 1 to 6 carbon atoms such as methylene, ethylene, propylene, trimethylene, tetramethylene, ethylethylene, pentamethylene, hexamethylene group, etc. Examples thereof include an alkylene group (preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms). The alkylene group may have a linear or branched form. Among these, as the alkylene group for R ⁵ and R ⁶ , an ethylene group or a propylene group can be preferably used.

Further, m and n are not particularly limited as long as they are integers of 0 or more. For example, at least one of m and n can be selected from a range of about 0 to 20, preferably about 1 to 10. As m and n, either one is 0 and the other is an integer of 1 or more (particularly 1) in many cases. M and n are not 0 at the same time (when m and n are 0 at the same time, [— (R ⁵ O) _m (R ⁶ O) _n —H] represents a hydrogen atom). .

  Further, X represents a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include an alkylene group, a cycloalkylene group, and an arylene group. The alkylene group for X may be linear or branched. Moreover, either saturated or unsaturated may be sufficient. Examples of the alkylene group of X include an alkylene group having about 1 to 6 carbon atoms such as methylene, ethylene, propylene, trimethylene and tetramethylene groups (preferably an alkylene group having 1 to 4 carbon atoms, more preferably 2 or 2 carbon atoms). 3 alkylene groups). Examples of the cycloalkylene group include cycloalkylene groups having about 5 to 12 members such as 1,2-cyclohexylene group, 1,3-cyclohexylene group, and 1,4-cyclohexylene group. Can be mentioned. As the arylene group, for example, 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group and the like can be used.

  Moreover, if p is an integer greater than or equal to 1, it will not be restrict | limited especially, For example, it can select from the range of about 1-10, Preferably it is an integer of 1-6, More preferably, it is an integer of 1-4.

  More specifically, examples of the amine compound represented by the formula (I) include N, N, N ′, N′-tetrakis (2-hydroxyethyl) ethylenediamine, N, N, N ′, N. '-Tetrakis (2-hydroxypropyl) ethylenediamine, N, N, N', N'-tetrakis (2-hydroxyethyl) trimethylenediamine, N, N, N ', N'-tetrakis (2-hydroxypropyl) trimethyl In addition to methylenediamine, polyoxyethylene condensates of ethylenediamine, polyoxypropylene condensates of ethylenediamine, polyoxyalkylene condensates of alkylenediamine such as polyoxyethylene-polyoxypropylene condensate of ethylenediamine, and the like. As such an amine compound, for example, commercially available products such as trade names “EDP-300”, “EDP-450”, “EDP-1100”, “Pluronic” (manufactured by ADEKA Corporation) are used. You can also

  From the viewpoint of promoting the crosslinking reaction and improving the productivity, the amount of the amine compound containing a plurality of hydroxyl groups is, for example, 0.01 to 5.0 with respect to 100 parts by weight of the acrylic polymer. Part by weight is preferred, more preferably 0.05 to 1.0 part by weight.

  In the pressure-sensitive adhesive composition of the present invention, a crosslinking accelerator other than those described above can be used in order to accelerate the crosslinking reaction. Examples of such crosslinking accelerators include N, N, N ′, N′-tetramethylhexanediamine, amino compounds such as imidazole, amine compounds having a plurality of other reactive functional groups other than hydroxyl groups, and naphthenic acid. Examples include organometallic compounds such as cobalt, dibutyltin diacetate, dibutyltin hydroxide, dibutyltin laurate and the like. These can be used alone or in combination of two or more. The amount of the crosslinking accelerator used is usually preferably 0.001 to 0.5 parts by weight, more preferably 0.001 to 0.3 parts by weight, for example, with respect to 100 parts by weight of the acrylic polymer. .

  In addition to the above, the pressure-sensitive adhesive composition of the present invention may contain other general additives, that is, an ultraviolet absorber, a light stabilizer, an anti-aging agent, a release regulator, a tackifier, and a plasticizer, as necessary. , Softeners, fillers, colorants (such as pigments and dyes), surfactants, and the like may be included.

  The pressure-sensitive adhesive composition of the present invention comprises an acrylic polymer and a crosslinking agent, and if necessary, a nitrogen atom-containing hydroxy compound (particularly, an amine compound containing a plurality of hydroxyl groups), other crosslinking accelerators and other It can be prepared by mixing with additives.

  The gel fraction of the cross-linked structured pressure-sensitive adhesive of the present invention (pressure-sensitive adhesive after cross-linking) is preferably 40 to 80%, more preferably 50 to 70%, from the viewpoint of balancing foam resistance and peeling properties. . The gel fraction can be determined as an ethyl acetate insoluble matter, specifically, as a weight fraction (% by weight) with respect to a sample before immersion of the insoluble matter after being immersed in ethyl acetate at 23 ° C. for 7 days. Desired. The gel fraction can be controlled by the amount of crosslinking agent added, the content of component B, and the molecular weight of the polymer component. If the gel fraction is less than 40%, foaming tends to occur, and if it exceeds 80%, “floating” and “peeling” from the adherend may occur easily.

Specifically, the gel fraction (ratio of solvent-insoluble matter) is a value calculated by, for example, the following “method for measuring gel fraction”.
(Measurement method of gel fraction)
Cross-linked structured pressure-sensitive adhesive (cross-linked pressure-sensitive adhesive): About 0.1 g was collected and wrapped in a porous tetrafluoroethylene sheet (trade name “NTF1122”, manufactured by Nitto Denko Corporation) having an average pore diameter of 0.2 μm. Then, it is tied with a kite string, the weight at that time is measured, and this weight is defined as the weight before immersion. The weight before immersion is the total weight of the pressure-sensitive adhesive, the tetrafluoroethylene sheet, and the kite string. In addition, the total weight of the tetrafluoroethylene sheet and the kite string is also measured, and this weight is defined as the wrapping weight.
Next, the above-mentioned pressure-sensitive adhesive wrapped with a tetrafluoroethylene sheet and tied with a kite string (hereinafter referred to as “sample”) is placed in a 50 ml container filled with ethyl acetate and left at 23 ° C. for 7 days. . Then, the sample (after ethyl acetate treatment) is taken out from the container, transferred to an aluminum cup, dried in a dryer at 130 ° C. for 2 hours to remove ethyl acetate, the weight is measured, and the weight is immersed. After weight.
Then, the gel fraction is calculated from the following formula.
Gel fraction (% by weight) = (A−B) / (C−B) × 100 (1)
(In Formula (1), A is the weight after immersion, B is the weight of the bag, and C is the weight before immersion.)
For example, it is preferable that the gel fraction of the pressure-sensitive adhesive satisfies the above range when the pressure-sensitive adhesive composition is crosslinked at 23 ° C. for 168 hours. Further, depending on the application, it is preferable that the gel fraction of the pressure-sensitive adhesive when satisfying the crosslinked structure at 50 ° C. for 72 hours satisfies the above range.

  As described above, in a conventional pressure-sensitive adhesive (pressure-sensitive adhesive composition), generally, an alkyl (meth) acrylate has been used as a main monomer component. However, the acrylic polymer formed from such a pressure-sensitive adhesive composition has a problem that the storage elastic modulus at a high temperature is lowered, and the anti-foaming / peeling property under a high temperature and high humidity environment is not sufficient. It was. Therefore, in order to improve the characteristics, copolymerization of high Tg monomers and functional group-containing monomers (carboxyl group-containing monomers such as acrylic acid) and oligomers (low molecular weight polymers) are added to the entire adhesive system (acrylic). Increasing the glass transition temperature (Tg) of the polymer) or increasing the molecular weight of the polymer has been performed. However, when the Tg of the entire system is increased, the storage elastic modulus in the room temperature region is also increased, which causes problems such as easy to bite bubbles at the time of pasting, and deterioration of low temperature and high speed characteristics. When the molecular weight is increased, the viscosity increases, so that the coating property is lowered and the productivity is deteriorated. Further, for the purpose and improvement of adhesion and cohesiveness, particularly when a carboxyl group-containing monomer such as acrylic acid is used as a monomer component, the resistance when a metal thin film (metal oxide thin film) is used as an adherend is used. There was a problem that the corrosion performance deteriorated. That is, it has been impossible to achieve a high level of compatibility between all properties such as anti-foaming resistance, corrosion resistance, and low-temperature properties (low-temperature adhesion properties).

  In contrast, in the present invention, a carboxyl group-containing monomer is not used as the monomer component of the pressure-sensitive adhesive, but an alkoxyalkyl acrylate having an appropriate polarity is used as the main monomer component, and the monomer composition, molecular weight, and degree of crosslinking of the pressure-sensitive adhesive By adjusting properly, we succeeded in achieving both low temperature and high temperature adhesion performance and corrosion resistance performance while satisfying foaming and peeling resistance. Further, by adopting the above composition, for example, when an alkoxyalkyl acrylate and a carboxyl group-containing monomer are copolymerized, there is no problem such as an increase in the viscosity of the polymer due to excessive hydrogen bonding, and more appropriate. Due to the molecular weight, an acrylic polymer excellent in coatability can be obtained.

  The mechanism of the effect expression by the acrylic polymer constituting the pressure-sensitive adhesive composition of the present invention is not clear, but is estimated as follows. In the present invention, alkoxyalkyl acrylate (component A) is used as the main monomer, so that the Tg of the polymer is relatively low. On the other hand, the effect of the alkoxyl group of the alkoxyalkyl acrylate and the specific molecular weight in the present invention allow an appropriate interaction to work when the pressure-sensitive adhesive composition has a high molecular weight, and the entanglement between polymer chains increases. Furthermore, since the entanglement of the polymer chains is difficult to unravel even at high temperatures, the storage elastic modulus of the polymer does not decrease even at high temperatures. For this reason, even at a relatively low Tg and molecular weight, the storage elastic modulus at a high temperature can be maintained high, and the foaming resistance at a high temperature is satisfied while satisfying the coating property and the adhesion at a low temperature and a high speed. Peelability can also be achieved.

  Further, since the acrylic polymer constituting the pressure-sensitive adhesive composition of the present invention does not contain a carboxyl group-containing monomer as a constituent monomer, the resistance value of a metal thin film (metal oxide thin film) such as ITO caused by an acid component Ascending does not occur and can be suitably used for applications such as laminating ITO films. Although the mechanism for increasing the resistance value is not clear, the carboxyl group-containing monomer remaining as a monomer during polymerization and the low molecular weight polymer that can be dissolved in moisture are formed on the ITO film by moisture under high temperature and high humidity conditions. It is presumed that it penetrates and prevents conduction.

  Furthermore, the acrylic polymer constituting the pressure-sensitive adhesive composition of the present invention contains a specific amount of a monomer (component B) having a crosslinkable functional group such as a hydroxyl group, and is crosslinked with a crosslinking agent. And thereby exhibiting the effect of preventing foaming and peeling at high temperatures.

  Furthermore, a pressure-sensitive adhesive composition that achieves a high level of yellowing resistance, productivity, and appearance by using an aliphatic isocyanate crosslinking agent as a crosslinking agent and adding an amine compound containing a plurality of hydroxyl groups. It can be a thing.

[Adhesive products]
A pressure-sensitive adhesive product is obtained by coating the pressure-sensitive adhesive composition of the present invention on a substrate or a release liner to form a pressure-sensitive adhesive layer. Examples of the pressure-sensitive adhesive product of the present invention include a pressure-sensitive adhesive sheet and a pressure-sensitive adhesive tape. The pressure-sensitive adhesive product of the present invention may be in the form of a sheet or tape that does not have a substrate (substrate-less) and is coated on the release liner, or on one side of the substrate. Alternatively, it may be in the form of a sheet or tape in which an adhesive layer made of the adhesive composition of the present invention is provided on both sides.

  The thickness of the pressure-sensitive adhesive layer (coating of the pressure-sensitive adhesive composition, thickness after drying) is not particularly limited and is, for example, preferably 5 to 1000 μm, more preferably 10 to 100 μm. The pressure-sensitive adhesive layer may have either a single layer or a laminate.

  As described above, the gel fraction of the pressure-sensitive adhesive layer (cross-linked structured pressure-sensitive adhesive) is preferably 40 to 80%, more preferably 50 to 70%, from the viewpoint of balancing foam resistance and peeling properties. .

  When the pressure-sensitive adhesive layer is provided on a substrate, the substrate is not particularly limited, and examples thereof include various optical films such as a plastic film, an antireflection (AR) film, a polarizing plate, and a retardation plate. Examples of the material for the plastic film include polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose, polysulfone, polyarylate, and the trade name “ARTON (cyclic olefin). And other plastic materials such as “Zeonor (cyclic olefin polymer; manufactured by Nippon Zeon Co., Ltd.)”. In addition, a plastic material can be used individually or in combination of 2 or more types. The thickness of the said base material is not specifically limited, For example, 10-1000 micrometers is preferable. In addition, the said base material may have any form of a single layer and a multilayer. Further, the substrate surface may be subjected to appropriate known or conventional surface treatments such as physical treatment such as corona discharge treatment and plasma treatment, and chemical treatment such as undercoating treatment.

  In the production of the pressure-sensitive adhesive product of the present invention, a known coating method can be used for coating the pressure-sensitive adhesive composition, and a conventional coater such as a gravure roll coater, reverse roll coater, kiss can be used. A roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, or the like can be used.

  The pressure-sensitive adhesive layer portion in the pressure-sensitive adhesive product of the present invention preferably has high transparency when used for optical applications such as a display. For example, the total light transmittance in the visible light wavelength region (JIS K). 7361) is preferably 90% or more, and more preferably 91% or more. Further, the haze value (according to JIS K 7136) of the pressure-sensitive adhesive layer portion in the pressure-sensitive adhesive product is preferably less than 1.0%, and more preferably less than 0.8%. The total light transmittance and haze are attached to, for example, a slide glass (for example, a total light transmittance of 91.8% and a haze value of 0.4%), and a haze meter (manufactured by Murakami Color Research Laboratory, product) Name "HM-150").

  The adherend of the pressure-sensitive adhesive product (pressure-sensitive adhesive sheet or pressure-sensitive adhesive tape) is not particularly limited, and examples thereof include an acrylic resin plate, a polycarbonate plate, glass, and polyethylene terephthalate.

  The pressure-sensitive adhesive product of the present invention is suitably used for displays such as a plasma display panel (PDP), a touch panel, and a liquid crystal panel. Among these, from the viewpoint of corrosion resistance, transparency, and adhesive properties, it is particularly preferably used for applications that are directly attached and fixed to a metal thin film such as a touch panel.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Acrylic polymer preparation example 1
(Acrylic polymer A)
As monomer components, 2-methoxyethyl acrylate: 70 parts by weight, 2-ethylhexyl acrylate: 29 parts by weight, 4-hydroxybutyl acrylate: 1 part by weight, 2,2′-azobisisobutyronitrile as a polymerization initiator : 0.2 part by weight and ethyl acetate: 100 parts by weight as a polymerization solvent were put into a separable flask and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature was raised to 63 ° C., the reaction was performed for 10 hours, toluene was added, and an acrylic polymer solution (“acrylic polymer solution A” with a solid content concentration of 25% by weight was added. May be referred to as “.”. The weight average molecular weight of the acrylic polymer (may be referred to as “acrylic polymer A”) in the acrylic polymer solution A was 1.5 million.

(Acrylic polymers B to K)
As shown in Table 1, the type of monomer component, the blending amount, and the blending amount of the solvent (ethyl acetate) are changed to change the acrylic polymer solution (sometimes referred to as “acrylic polymer solutions B to K”, respectively). Got. The weight average molecular weights of the acrylic polymers (may be referred to as “acrylic polymers B to K”, respectively) in the acrylic polymer solutions B to K are as shown in Table 1.

Example 1
Polyfunctional isocyanate compound (Nippon Polyurethane Industry Co., Ltd., trade name “Coronate L”) as a crosslinking agent for 100 parts by weight of acrylic polymer solution A (acrylic polymer A: 100 parts by weight) in terms of solid content. 0.3 parts by weight was added to prepare a pressure-sensitive adhesive composition (solution).
On the surface of the release treatment of a polyethylene terephthalate (PET) film (thickness: 38 μm) (release liner) whose surface has been subjected to a release treatment, the thickness obtained after drying is about 25 μm. It was cast-coated, heat-dried at 130 ° C. for 3 minutes, and further subjected to aging at 50 ° C. for 72 hours to produce a substrate-less pressure-sensitive adhesive sheet.

Examples 2-8, Comparative Examples 1-5
As shown in Table 2, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1 except that the type of acrylic polymer solution and the blending amount of the crosslinking agent were changed.

[Evaluation]
For the pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets obtained in Examples 1 to 8 and Comparative Examples 1 to 5, coating properties, transparency, adhesiveness (low-temperature adhesive properties), anti-foaming resistance, and corrosion resistance are as follows. It evaluated by the measuring method or evaluation method. The evaluation results are shown in Table 2. In addition, the gel fraction of Table 2 is the value of the gel fraction of the adhesive extract | collected from the said adhesive sheet.

(1) Transparency (total light transmittance, haze value)
Each pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples is a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., trade name “S-1111”, total light transmittance 91.8%, haze value 0.4%). After bonding, the PET film was peeled off to prepare a test piece having a layer structure of an adhesive layer / slide glass, and the haze (haze) value (%) of the test piece was measured with a haze meter (Murakami Color Research Laboratory). , Trade name "HM-150"). The haze value (%) was obtained using the formula of “diffuse transmittance / total light transmittance × 100”.
When the haze value is less than 1.0%, transparency is good (◯), and when it is 1.0% or more, it is poor (x).

(2) Coating property In Examples and Comparative Examples, the obtained adhesive solution (adhesive composition) was applied to a release-treated PET film (release liner) at a coating speed of 1 to 10 m / min. When the pressure-sensitive adhesive sheet was produced by casting, the coated surface was smooth and the coated surface was smooth, the coating property was good (◯), the coated stripe was generated, and the coated surface was not smooth. The product was judged to have poor coatability (x). The determination was made visually.

(3) Corrosion resistance A PET film (trade name “Lumirror S-10 # 25”, manufactured by Toray Industries, Inc., thickness: 25 μm) is bonded to the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and 20 mm × A test piece was cut out to a size of 50 mm.
As shown in FIG. 1, a conductive PET film (manufactured by Nitto Denko Corporation, trade name “Electrista P400L-TNMP”) (size: 70 mm × 25 mm) is coated with a silver paste with a width of 15 mm on its conductive surface. The adhesive surface of the above-mentioned test piece 1 from which the release liner was peeled off was bonded to the ITO film forming surface 2 side, which was left for 250 hours in each environment of 60 ° C. and 95% RH and 80 ° C. The resistance change rate (%) was measured using “Digital Milliohm Hitester Part No. 3540” manufactured by Hioki Electric Co., Ltd., with electrodes attached to the silver paste portions 3 at both ends. did.
If the change rate of the resistivity was less than 120%, it was judged that the corrosion resistance was good (◯), and if it was 120% or more, the corrosion resistance was poor (x).
In addition, as a result of performing the same test only with the electroconductive PET film which does not stick an adhesive sheet as a blank, it was 110% on condition of 80 degreeC, and 120% on condition of 60 degreeC95% RH.

(4) Anti-foaming peelability The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were bonded to a PET film (trade name “A4300”, manufactured by Toyobo Co., Ltd., thickness 125 μm), width 100 mm × length 100 mm. A film piece was prepared.
The release liner is peeled off from this film piece, and bonded and fixed to a polycarbonate (PC) board (manufactured by Teijin Chemicals Ltd., trade name “Panlite PC1111”, thickness 1 mm), PET film / adhesive layer / A sample piece having a PC board layer structure was produced.
The sample piece was heat treated (heat resistance test) in an oven at 80 ° C. for 5 hours. After this heat resistance test, the sample piece is visually observed at the bonding interface (the interface between the pressure-sensitive adhesive layer and the PC board). If no "bubbles" or "float" are observed, the foam peeling resistance is good. (O) When “bubbles” and “float” were observed even slightly, it was judged that the foaming resistance was poor (×).

(5) Low-temperature adhesive properties As shown in FIG. 2, an acrylic plate 41 (length 70 mm × width 50 mm × thickness 2.0 mm) (manufactured by Mitsubishi Rayon Co., Ltd., trade name “Acrylite”) and PET film (Toyo Acrylic plate 42 (length: 120 mm × width: 50 mm) having a surface bonded with an adhesive made by Spinning Co., Ltd., trade name “A4300, # 125”) is used as an adhesive sheet 43 ( The sample 4 for measurement was produced by pasting together using a length 10 mm × width 50 mm). The above bonding (crimping) was performed under the condition of one reciprocation using a 5 kg roller, and the bonding area was 10 mm × 50 mm.
The measurement sample was autoclaved for 30 minutes at 50 ° C. and 5 atm, then aged for 24 hours in an atmosphere at 50 ° C. and normal pressure, and further left for 3 hours at the measurement temperature (−30 ° C.) for measurement. Using.
As shown in FIGS. 3 to 5, the measurement sample is set in an impact test apparatus, and an impact test is performed in 10 ° increments from an angle (measurement angle) of 10 ° to 90 ° in an environment of −30 ° C. The angle at which the plate 41 was peeled was measured. Details of the impact test method and the test apparatus are as follows.
[Impact test equipment, test method]
(I) Test apparatus FIG. 3 shows a schematic diagram of the test apparatus. The test device 5 has a rectangular frame (long side: 610 mm, short side: 322 mm) made of a stainless steel plate having a plate thickness of 6 mm and an L-shaped cross section (one side and the other side are 50 mm each). A rectangular frame (long side is 1010 mm, short side is 322 mm) made of a stainless steel plate having a plate thickness of 3 mm and an L-shaped cross section (25 mm each on one side and the other side) is formed on one angle 51. The two angles 52 were erected vertically, and the upper end frame 52A of the second angle 52 was made of a stainless steel plate having a plate thickness of 3 mm and an L-shaped cross-section (one side of the L shape and the other side of 25 mm each). An upper end frame 53A of a third angle 53 (total weight 3.3 kg) made of a rectangular frame (long side: 915 mm, short side: 310 mm) is connected by a hinge, and the third angle 53 is relative to the second angle 52. Is a device which is adapted to moving.
As shown in FIG. 4, the lower end frame 53B of the third angle 53 has a U-shaped cross section to form a sample holding portion, and holds the measurement sample 4 (a length portion of 20 mm from the lower end of the acrylic plate 42). keeping).
(Ii) Test method Under an environment of −30 ° C., as shown in FIG. 5, the third angle 53 is lifted to a position that forms a predetermined angle (α) with respect to the second angle 52, and then the hand is released, Collide with two angles 52 (move as indicated by arrow a). This operation is performed by changing the angle (α).
As shown in FIG. 6, a force (inertial force) is applied to the acrylic plate 41 in the direction of the arrow b in the figure due to the collision, and the angle at which the acrylic plate 41 is peeled off from the acrylic plate 42 by this force is measured. did.
The angle (α) (measurement angle) was increased from 10 ° to 90 ° in 10 ° increments.

As is apparent from the results of Tables 1 and 2, the pressure-sensitive adhesive composition satisfying the provisions of the present invention is excellent in coatability, and the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition are subjected to high temperatures. However, “bubbles” and “float” do not occur, and it has excellent resistance to foaming and peeling. Furthermore, even if it is attached to a conductive film and stored for a long time in a high temperature environment or a high temperature and high humidity environment, there is no problem of corroding the adherend (Example).
In addition, the pressure-sensitive adhesive sheets of Examples 1, 3, and 8 exhibited excellent low-temperature adhesive properties because no peeling of the acrylic plate was observed even at a measurement angle of 90 ° in the low-temperature adhesive property test (impact test). Moreover, in Example 2 and Examples 4-7, peeling of the acrylic board was seen at a measurement angle of 50 °, and good low-temperature adhesive properties were shown. Furthermore, the transparency of the pressure-sensitive adhesive sheets of the examples was all good (◯).
On the other hand, when the compounding amount of the alkoxyalkyl acrylate as component A was small (Comparative Examples 1 and 4) or when the molecular weight of the acrylic polymer was too small (Comparative Example 3), the anti-foaming / peeling properties were lowered. Moreover, when the molecular weight of the acrylic polymer was too large (Comparative Example 5), the coatability was lowered. Further, when acrylic acid (carboxyl group-containing monomer) was used as the monomer component (Comparative Example 2), there was a problem that the adherend was corroded when stored for a long period of time in a high temperature and high humidity environment.

  Next, the effect of improving yellowing resistance and productivity when using an aliphatic isocyanate crosslinking agent and an amine compound containing a plurality of hydroxyl groups will be described based on examples. However, the present invention is not limited to these examples.

Acrylic polymer preparation example 2
(Acrylic polymer L)
As shown in Table 3, ethyl acetate was charged as a predetermined amount of monomer component and polymerization solvent, charged into a separable flask, and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature was raised to 63 ° C., and 0.22 parts by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator was added and reacted for 10 hours. Then, MEK (methyl ethyl ketone) was added to obtain an acrylic polymer solution having a solid content concentration of 25% by weight (sometimes referred to as “acrylic polymer solution L”).

(Acrylic polymer MT)
As shown in Table 3, the acrylic polymer solution (which may be referred to as “acrylic polymer solutions M to T” respectively) is obtained by changing the monomer component type, blending amount, and solvent (ethyl acetate) blending amount. Got.
The weight average molecular weights of the acrylic polymers in the acrylic polymer solutions L to T (sometimes referred to as “acrylic polymers L to T” respectively) are as shown in Table 3.

Example 9
In terms of solid content, an acrylic polymer solution L: 100 parts by weight (acrylic polymer L: 100 parts by weight), an aliphatic polyfunctional isocyanate compound (Japan Polyurethane Industry Co., Ltd., trade name “ Coronate HL ") 0.7 parts by weight, 0.3 parts by weight of a polyol obtained by adding propylene oxide to ethylenediamine as a crosslinking aid (trade name" EDP-300 "manufactured by ADEKA Co., Ltd.) Solution) was prepared.
On the surface of the release treatment of a polyethylene terephthalate (PET) film (thickness: 38 μm) (release liner) whose surface has been subjected to a release treatment, the thickness obtained after drying is about 25 μm. It was cast and applied, dried by heating at 130 ° C. for 3 minutes, and further subjected to aging at 23 ° C. for 7 days to produce a substrate-less pressure-sensitive adhesive sheet.

Examples 10-23, Comparative Examples 6-10
As shown in Tables 4 and 5, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 9, except that the type of acrylic polymer solution, the type of crosslinking agent, the type of crosslinking aid, and the blending amount were changed. .

[Evaluation]
For the pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets obtained in Examples 9 to 23 and Comparative Examples 6 to 10, coating properties, transparency, resistance to foaming peeling, corrosion resistance, and productivity (how to increase the degree of crosslinking) ), Yellowing resistance (b value after long-time heat treatment) was evaluated.
In addition, the measuring method or evaluation method of transparency, coating property, corrosion resistance, and foaming peeling resistance is the same as the above-described evaluation methods (1) to (4). The degree of cross-linking and yellowing resistance were evaluated by the following measurement method or evaluation method. The evaluation results are shown in Tables 4 and 5. The gel fractions in Tables 4 and 5 are values of the gel fraction of the pressure-sensitive adhesive collected from the pressure-sensitive adhesive sheet.

(6) How to increase the degree of crosslinking (productivity)
The pressure-sensitive adhesive compositions obtained in Examples and Comparative Examples were cast and applied on the release-treated surface of a PET film that had been release-treated on the surface so that the thickness after drying was about 25 μm. And dried for 3 minutes to form an adhesive layer. The pressure-sensitive adhesive layer thus obtained was subjected to aging under two different aging conditions of 50 ° C. for 24 hours and 23 ° C. for 168 hours (7 days) to prepare a pressure-sensitive adhesive (cross-linked pressure-sensitive adhesive) sample. .
Adhesive (adhesive after crosslinking) under each of the above aging conditions (50 ° C. for 24 hours, 23 ° C. for 168 hours): About 0.1 g was sampled and gel fraction was obtained according to the above-mentioned “Method for measuring gel fraction”. (% By weight) was calculated.
The gel fraction of the pressure-sensitive adhesive aging at 50 ° C. for 24 hours (referred to as “gel fraction at 50 ° C. for 24 hours”) and the gel fraction of the pressure-sensitive adhesive aging at 23 ° C. for 168 hours (“the gel fraction at 23 ° C. for 168 hours”). "How to increase the degree of crosslinking (%)" was calculated using the following formula.
How to increase the degree of crosslinking (%) = (gel fraction at 168 hours at 23 ° C.) / (Gel fraction at 24 hours at 50 ° C.) × 100
Note that the greater the degree of cross-linking, the easier the cross-linking reaction proceeds at room temperature and the better the productivity.

(7) Yellowing resistance (b value after heat treatment at 80 ° C. for 500 hours, b value after heat treatment at 80 ° C. for 1000 hours)
After heat-treating the samples (each adhesive sheet obtained in Examples and Comparative Examples) under predetermined conditions (80 ° C. for 500 hours, 80 ° C. for 1000 hours), a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., trade name “S- 1111 ", total light transmittance 91.8%, haze value 0.4%), with the pressure-sensitive adhesive layer exposed (PET film peeled off), using a spectrophotometer DOT-3C manufactured by Murakami Color Research Laboratory The b value was evaluated in the L ^* a ^* b ^* color system.

  In addition, all the transparency of an Example was favorable ((circle)).

As is apparent from the results of Tables 3 to 5, the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet using a predetermined amount of an aliphatic isocyanate cross-linking agent and a cross-linking aid of an amine-based compound containing a plurality of hydroxyl groups are coated. In addition to being excellent in heat resistance, foaming / peeling resistance and corrosion resistance, it is excellent in yellowing resistance that does not cause yellowing even when heated for a long time, and relatively quickly even at a temperature of 23 ° C. The degree of crosslinking was increased and the productivity was excellent (Examples 9 to 20).
On the other hand, when an aromatic isocyanate crosslinking agent is used or when a crosslinking aid of an amine compound containing a plurality of hydroxyl groups is not used in an appropriate amount, coating properties, foam resistance / peeling resistance, Although it has excellent characteristics such as corrosiveness, yellowing resistance and warming are performed such that yellowing becomes slightly remarkable, and the degree of crosslinking is slow, and aging at 23 ° C. for 168 hours results in insufficient crosslinking. Productivity under no conditions could not be achieved at a high level (Examples 21 to 23).
Even when an aliphatic isocyanate cross-linking agent and a crosslinking aid of an amine-based compound containing a plurality of hydroxyl groups are used, the case where component A and component B are not used or acrylic acid is used as the monomer component. In the case where the molecular weight of the acrylic polymer was not within an appropriate range, problems of coating property, foam resistance / peeling resistance, and corrosion resistance occurred, and the effects of the present invention could not be obtained (Comparative Example 6). -10).

FIG. 1 is a schematic diagram showing a resistance value measurement sample used for evaluation of corrosion resistance in Examples. FIG. 2 is a schematic cross-sectional view (2a) and a schematic front view (2b) showing a measurement sample used in a test for low-temperature adhesive properties. FIG. 3 is a schematic view showing a test apparatus used for testing low temperature adhesive properties. 4 is a schematic cross-sectional view showing a sample holding portion of the test apparatus of FIG. FIG. 5 is a schematic diagram (schematic side view of a test apparatus) showing a test method for low-temperature adhesive properties. FIG. 6 is a schematic diagram showing a force applied to a measurement sample in a test for low-temperature adhesive properties.

Explanation of symbols

1 Test piece 2 Conductive PET film (exposed portion of ITO film forming surface)
3 Conductive PET film (Silver paste application part)
4 Sample for measurement 41 Acrylic plate 42 Acrylic plate with PET film bonded to the surface with an adhesive 42a PET film 42b Acrylic plate 43 Adhesive sheet 5 Impact test device 51 First angle 52 Second angle 52A Upper edge frame 53 of second angle 53 Third angle 53A Third angle upper end frame 53B Third angle lower end frame α Measurement angle a Direction of movement of third angle in impact test b Direction of force applied to acrylic plate in impact test

Claims (6)

  An acrylic polymer having a weight average molecular weight of 400,000 to 1,600,000 and a cross-linking agent comprising an alkoxyalkyl acrylate (component A) and an acrylic monomer having a crosslinkable functional group (component B) as essential monomer components The pressure-sensitive adhesive composition is 45 to 99.5 parts by weight of component A and 0.5 to 4.5 parts by weight of component B based on 100 parts by weight of all monomer components constituting the acrylic polymer. The pressure-sensitive adhesive composition is characterized in that the monomer component constituting the acrylic polymer does not substantially contain a carboxyl group-containing monomer.   For 100 parts by weight of an acrylic polymer having a weight average molecular weight of 400,000 to 1,600,000 comprising an alkoxyalkyl acrylate (component A) and an acrylic monomer having a crosslinkable functional group (component B) as essential monomer components A pressure-sensitive adhesive composition containing 0.01 to 3.0 parts by weight of an aliphatic isocyanate cross-linking agent and 0.01 to 5.0 parts by weight of an amine compound containing a plurality of hydroxyl groups. A monomer that constitutes an acrylic polymer, wherein the content of component A is 45 to 99.5 parts by weight and the content of component B is 0.5 to 4.5 parts by weight with respect to 100 parts by weight of all monomer components constituting the polymer The pressure-sensitive adhesive composition according to claim 1, wherein the component is substantially free of a carboxyl group-containing monomer.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein Component B is an acrylic monomer having a hydroxyl group.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the gel fraction after the cross-linking structure is 40 to 80%.   The adhesive product which apply | coated the adhesive composition of any one of Claims 1-4.   A display using the adhesive product according to claim 5.

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