TW201544565A - Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet - Google Patents

Abstract

A pressure-sensitive adhesive composition includes a (meth)acrylic copolymer having a structural unit derived from a monomer having a hydroxyl group, an alkylene oxide-modified multifunctional (meth)acrylate at from more than 5 parts by mass to less than 40 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer, and a crosslinking agent, in which the content of a monofunctional (meth)acrylate is less than 10 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer.

Description

Adhesive composition and adhesive sheet

This invention relates to adhesive compositions and adhesive sheets.

The touch panel is configured by laminating a plurality of members such as a glass substrate, a transparent conductive film, and a pattern film with an adhesive. In order to avoid corrosion of the electrode printed on the transparent conductive film, the adhesive is required to be free of acidic components. Further, an acrylic adhesive is used as an adhesive for bonding these members.

Further, in these members, there may be a difference in height due to decoration of the electrode or the pattern film printed on the transparent conductive film, and if the height difference is not filled, the air bubbles may be mixed. The members which are deteriorated in appearance or deteriorated in adhesion are peeled off from each other. Therefore, the adhesive composition for the bonding of the members is required to have a property of filling the height difference at the time of lamination, that is, the height difference dependency.

Further, members constituting the touch panel sometimes use a material such as polycarbonate or polymethyl methacrylate which generates a fugitive gas in a high temperature environment. If a fugitive gas is generated between the members constituting the touch panel, the member may float, which may lower the visibility of the appearance or display. Therefore, it is required for the adhesive composition to suppress the occurrence of fugitive gas and to avoid the floating property of the member, that is, the gas floating resistance.

In addition, when the portable electronic device is equipped with a touch panel, the touch panel may be exposed to a high temperature and humidity environment during use. At this time, in order to maintain the visibility of the display, the adhesive layer composed of the adhesive composition needs to have no whitening property even in a high-temperature and high-humidity environment, that is, resistance to moist heat whitening.

International Publication No. 2013/061938 discloses an adhesive composition comprising a thermosetting acrylic copolymer and an ultraviolet curable multifunctional acrylate as a binder having high height difference attachment and high heat and whitening resistance. Composition.

[Problems to be solved by the invention]

However, the adhesive composition disclosed in the above-mentioned International Publication No. 2013/061938 has a problem that the gas floating resistance is poor, and there is a problem that air bubbles enter between the members and the members float and the visibility of the display is lowered.

An object of the present invention is to provide an adhesive composition capable of forming an adhesive layer which is excellent in height difference and wet heat resistance, and which is excellent in gas floating resistance, and has adhesion of the adhesive layer sheet. [Means for solving the problem]

The above problems are solved by the following methods. <1> A binder composition comprising: a (meth)acrylic copolymer containing a constituent unit derived from a monomer having a hydroxyl group, and more than 100 parts by mass of the (meth)acrylic copolymer 5 parts by mass and less than 40 parts by mass of the alkylene oxide-modified polyfunctional (meth) acrylate, and a crosslinking agent; the content of the monofunctional (meth) acrylate relative to 100 parts by mass of the (meth) group The acrylic copolymer is less than 10 parts by mass.

<2> The adhesive composition according to <1>, wherein the alkylene oxide-modified polyfunctional (meth) acrylate has an alkylene oxide addition molar number of from 1 mol to 8 mol. <3> The adhesive composition according to <1> or <2>, wherein the alkylene oxide-modified polyfunctional (meth) acrylate is an alkylene oxide-modified bifunctional (meth) acrylate. The adhesive composition according to any one of <1> to <3> wherein the alkylene oxide-modified polyfunctional (meth) acrylate is a compound represented by the following formula (I); [Chemical 1] In the formula (I), R ₁ and R ₂ each independently represent a methyl group or a hydrogen atom, and R ₃ represents a linear or branched alkyl group having a carbon number of 2 to 6, and n is 1 Above 8 or less. <5> The adhesive composition of <4>, wherein n in the formula (I) is 3 or more and 8 or less.

<6> The adhesive composition according to any one of <1> to <5> wherein the crosslinking agent is a polyisocyanate compound. <7> The adhesive composition according to any one of <1> to <6>, further comprising a photopolymerization initiator. The adhesive composition of any one of the above-mentioned (meth)acrylic copolymers, the content of the structural unit derived from the monomer having a hydroxyl group, relative to The total mass of the (meth)acrylic copolymer is 5% by mass or more and 40% by mass or less. <9> The adhesive composition of any one of <1> to <8> is used for a touch panel.

<10> An adhesive sheet comprising an adhesive layer obtained by thermally hardening an adhesive composition according to any one of <1> to <9>. [Effects of the Invention]

According to the present invention, it is possible to provide an adhesive composition capable of forming an adhesive layer which is excellent in height difference and wet heat whitening resistance and excellent in gas floating resistance, and an adhesive sheet having the adhesive layer .

Hereinafter, an embodiment of an embodiment of the present invention will be described. In addition, the numerical range represented by "~" in this specification is a range which contains the numerical value of the before and after "~" as a minimum and maximum. Moreover, the amount of each component in the composition of the present specification means a total amount of a plurality of substances related to the component, unless it is used in combination with a plurality of substances related to each component in the composition. Further, the (meth) acrylate means at least one of an acrylate and a methacrylate, and the same meaning as the statement of a (meth)acrylic copolymer such as a (meth) acrylate.

[Adhesive Composition] The adhesive composition of the present invention comprises: a (meth)acrylic copolymer containing a constituent unit derived from a monomer having a hydroxyl group, and 100 parts by mass of (meth)acrylic acid The copolymer is more than 5 parts by mass and less than 40 parts by mass of the alkylene oxide-modified polyfunctional (meth) acrylate, and a crosslinking agent; the content of the monofunctional (meth) acrylate relative to 100 parts by mass The (meth)acrylic copolymer is less than 10 parts by mass.

The use of the adhesive composition of the present invention is, for example, a touch panel used for bonding a plurality of members such as a glass substrate, a transparent conductive film, and a pattern film to form a touch panel.

The adhesive composition of the present invention contains a thermosetting acrylic copolymer and a predetermined amount of a specific monomer which is cured by ultraviolet rays. Therefore, only the specific monomer which is ultraviolet-cured when the adhesive composition on the release sheet is thermally cured is not cured, and a soft adhesive layer can be formed. Because the adhesive layer is soft, the adhesive layer can be attached to the height difference component, which can be attached to the height difference, so that the height difference can be ensured. After the transfer, the ultraviolet rays are irradiated onto the adhesive layer to be hardened, and the hardened adhesive layer exhibits high elasticity, so that an adhesive layer excellent in gas floating resistance can be formed.

Further, in the adhesive composition of the present invention, an alkylene oxide-modified highly hydrophilic modified polyfunctional (meth) acrylate is used. Therefore, when the adhesive layer is exposed to a high-temperature and high-humidity environment, since the water is compatible with the highly hydrophilic resin, the adhesive layer is not whitened, and the wet heat-resistant whitening property is excellent. Further, the modified polyfunctional (meth) acrylate is cured by irradiation with ultraviolet rays to exhibit high elasticity and excellent cohesive force. Therefore, the adhesive layer after the ultraviolet irradiation suppresses the generation of the fugitive gas and is excellent in the gas floating resistance. Further, since the monofunctional (meth) acrylate is less than 10 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer, the adhesive layer exhibits high elasticity and resistance to gas floating.

((Meth)Acrylic Copolymer) The adhesive composition of the present invention contains a (meth)acrylic copolymer containing a constituent unit derived from a monomer having a hydroxyl group. Here, the (meth)acrylic copolymer is a copolymer of a (meth)acrylic monomer which is 50% by mass or more of the total monomer component of the copolymer, and preferably 90% by mass or more.

Examples of the monomer having a hydroxyl group include a monomer having a hydroxyl group and an ethylenically unsaturated bonding group. Specific examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (methyl). 4-hydroxybutyl acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2 (meth)acrylic acid ,4-trimethyl-3-hydroxypentyl ester, 2-ethyl-3-hydroxyhexyl (meth)acrylate, glycerol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethyl b (meth) acrylate compound such as diol mono(meth) acrylate or poly(ethylene glycol-propylene glycol) mono (meth) acrylate; N-methylol (meth) acrylamide, N-hydroxyl (meth) acrylamide compound having a hydroxyl group such as ethyl (meth) acrylamide; an unsaturated alcohol such as allyl alcohol or methyl allyl alcohol;

In view of the fact that the compatibility with other monomers is good and the copolymerization property is good, and the crosslinking reaction with the crosslinking agent is good, the monomer having a hydroxyl group is preferably a hydroxyalkane having a carbon number of 1 to 5. Hydroxyalkyl (meth) acrylate, alkyl (meth) acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms, 2-hydroxyethyl (meth)acrylate or (meth)acrylic acid 4-hydroxybutyl ester is particularly preferred.

The (meth)acrylic copolymer may also contain a constituent unit derived from a monomer other than the monomer having a hydroxyl group. Examples of the monomer other than the monomer having a hydroxyl group include an alkyl (meth)acrylate. Specific examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. N-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, (A) a group of n-decyl acrylate, n-dodecyl (meth) acrylate (lauryl (meth) acrylate), stearyl (meth) acrylate, etc. having a linear or branched carbon number of 1 to 18 The alkyl (meth) acrylate of the alkyl group and the derivatives but not having a hydroxyl group. In view of the fact that it is preferable to contain a hydrophobic monomer to prevent moisture from flowing into the resin and to have excellent wet heat whitening property, it is preferable to contain an alkyl (meth)acrylate derived from a linear alkyl group having 8 to 18 carbon atoms. The constituent unit preferably contains a constituent unit derived from n-dodecyl (meth)acrylate (lauryl (meth)acrylate).

Further, examples of the monomer other than the monomer having a hydroxyl group include the monomers described below in addition to the alkyl (meth)acrylate. Examples thereof include (meth) acrylate having a cyclic group such as cyclohexyl (meth) acrylate or benzyl (meth) acrylate; and saturated fatty acid vinyl esters such as vinyl formate, vinyl acetate, and C. An aliphatic vinyl monomer such as vinyl acetate, "vinyl versatate" (trade name, vinyl neodecanoate); an aromatic vinyl monomer such as styrene, α-methylstyrene or vinyl toluene; acrylonitrile a cyanoethylene monomer such as methacrylonitrile; dimethyl maleate, di-n-butyl maleate, di-2-ethylhexyl maleate, di-n-octyl maleate, fumaric acid a maleic acid such as dimethyl ester, di-n-butyl fumarate, di-2-ethylhexyl fumarate or di-n-octyl fumarate or a diester monomer of fumaric acid;

The content of the constituent unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is preferably 5% by mass or more and 40% by mass or less based on the total mass of the (meth)acrylic copolymer, and 15% by mass. The above 35 mass% or less is more preferable, and the 20 mass% is the best. The moisture-resistant whitening resistance can be improved by increasing the content of the constituent unit derived from the monomer having a hydroxyl group. Moreover, when the content rate of the structural unit derived from the monomer having a hydroxyl group is 40% by mass or less, the hydrophilicity of the formed adhesive layer does not become too high, and the adhesive in a high-humidity environment is suppressed. The moisture absorption of the layer. Thereby, the corrosion of the electrode printed on the transparent conductive film or other metal members is suppressed, so that the adhesive composition of the present invention can be applied to a touch panel.

Further, the (meth)acrylic copolymer of the present invention preferably contains no acidic component or substantially no acidic component. The adhesive composition of the present invention can be applied to a touch panel by suppressing corrosion of an electrode printed on the transparent conductive film or other metal member by not containing an acidic component or substantially containing no acidic component. . Further, the fact that the acidic component is not substantially contained means that the acidic component which is inevitably mixed is allowed to exist.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer contained in the adhesive composition of the present invention is not particularly limited, but is preferably 200,000 or more and 1,000,000 or less, and more preferably 300,000 to 800,000. The best is 400,000 or more and 600,000 or less. When the weight average molecular weight of the (meth)acrylic copolymer is contained in the range of values, it is preferable from the viewpoint of resistance to gas floating property and height difference.

Further, the ratio (Mw/Mn) of the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth)acrylic copolymer is preferably 20 or less, and more preferably in the range of 3 or more and 15 or less. It is the best for 5 or more and 8 or less. If the value of the distribution index (Mw/Mn) is included in the range of values, it is preferable from the viewpoint of resistance to gas floating and height difference.

Further, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the (meth)acrylic copolymer are values measured by the following methods (1) to (3).

(1) A solution of a (meth)acrylic copolymer was applied onto a release paper, and dried at 100 ° C for 2 minutes to obtain a film-form (meth)acrylic copolymer. (2) A film-form (meth)acrylic copolymer obtained in the above (1) and tetrahydrofuran were used to obtain a sample solution having a solid concentration of 0.2% by mass. (3) The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the (meth)acrylic copolymer were measured in the form of standard polystyrene using a gel permeation chromatography (GPC) under the following conditions. ).

(Condition) GPC: HLC-8220 GPC [Tosoh Co., Ltd.] Column: TSK-GEL GMHXL 4 mobile phase solvent: tetrahydrofuran Flow rate: 0.6 mL/min Column temperature: 40 °C

The glass transition temperature (Tg) of the (meth)acrylic copolymer is preferably in the range of -60 ° C to -20 ° C, more preferably in the range of -50 ° C to 25 ° C. Tg can be adjusted to an optimum elastic modulus at -60 ° C or higher, and the durability is excellent. Further, when the Tg is -20 ° C or less, the viscosity is not extremely impaired, and it is excellent in adhesion and correct adhesion. Further, since Tg is excellent in gas floating resistance in the range of -45 ° C or more to -25 ° C or less, it is particularly preferable.

[Calculation of Glass Transition Temperature (Tg)] In the present specification, the glass transition temperature (Tg) of the (meth)acrylic copolymer is a molar average glass transition temperature (molTg) obtained by the following calculation. The glass transition temperature of Tg ₁ , Tg ₂ , ‧ ‧ ‧ and Tg _n monomer 1, monomer 2, ‧ ‧ ‧ and monomer n in the following formula The absolute temperature (K) is calculated and calculated. The molar fraction of each of the m ₁ , m ₂ , ‧ ‧ ‧ and m _n monomers

[Number 1]

In addition, the "glass transition temperature (Tg) of a homopolymer" is referred to herein as a homopolymer of a monomer, using a differential scanning calorimeter (DSC) (EXSTAR 6000, manufactured by Seiko Instruments Inc.) in a nitrogen stream. In the measurement, 10 mg of the sample was measured, and the measurement was carried out under the conditions of a temperature increase rate of 10 ° C /min, and the turning point of the obtained DSC curve was defined as Tg.

The typical glass transition temperature (Tg) of a homopolymer is: methyl acrylate 5 ° C, ethyl acrylate -27 ° C, n-butyl acrylate -57 ° C, 2-ethylhexyl acrylate It was -76 ° C, 2-hydroxyethyl acrylate was -15 ° C, tributyl acrylate was 31 ° C, and lauryl acrylate was 15 ° C.

The content ratio of the (meth)acrylic copolymer of the adhesive composition can be appropriately selected depending on the purpose and the like. The content of the (meth)acrylic copolymer is preferably 60% by mass or more and 90% by mass or less based on the total mass of the solid content of the adhesive composition, and is preferably 70% by mass or more and 90% by mass or less. More than 85% by mass or less is more preferable. In addition, the total mass of solid content means the total mass of the residue after removing a volatile component, such as a solvent, from an adhesive composition.

The (meth)acrylic copolymer can be produced by polymerizing a monomer capable of forming a constituent unit of a (meth)acrylic copolymer. The polymerization method of the above copolymer is not particularly limited, and may be appropriately selected by a known method such as a solution polymerization method, an emulsion polymerization method or a suspension polymerization method. When the adhesive composition of the present invention is produced by using a copolymer obtained by polymerization, it is preferable to carry out polymerization by a solution polymerization method in view of simpler production.

The solution polymerization method can generally be carried out by using a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed, in a polymerization tank, in a nitrogen stream, at a reflux temperature of an organic solvent, by A known method such as carrying out a heating reaction for several hours while stirring is carried out.

Further, the weight average molecular weight and the distribution index of the (meth)acrylic copolymer can be easily adjusted depending on the polymerization temperature, time, amount of solvent, and type and amount of the polymerization initiator.

Examples of the organic solvent for polymerization used for the polymerization of the (meth)acrylic copolymer include benzene, toluene, ethylbenzene, n-propylbenzene, tertiary butylbenzene, o-xylene, m-xylene, p-xylene, and tetra. An aromatic hydrocarbon compound such as hydrogen naphthalene, decahydronaphthalene or aromatic petroleum brain; fat system such as n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, petroleum brain, turpentine or Alicyclic hydrocarbon compounds; ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate, etc. Ester compound; ketone compound such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl cyclohexanone; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether , glycol ether compounds such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, two An alcohol compound such as butanol or tertiary butanol; and the like. These organic solvents may be used alone or in combination of two or more.

As the polymerization initiator, an organic peroxide, an azo compound or the like which can be used in a usual solution polymerization method can be used. Examples of the organic peroxide include tertiary butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzammonium peroxide, ruthenium peroxide, hexanyl peroxide, and peroxidation. Diisopropyl dicarbonate, di-2-ethylhexyl peroxydicarbonate, tertiary butyl peroxy-3-acetate, 2,2-bis(4,4-di-tributyl peroxide) Hexyl)propane, 2,2-bis(4,4-di-tripentylpentylperoxycyclohexyl)propane, 2,2-bis(4,4-di-trioctyloctylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-isopropylphenylcyclohexyl)propane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)butane, 2 , 2-bis(4,4-di-trioctyloctyloxycyclohexyl)butane, and the like. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, and 2,2'-azobis-4. -Methoxy-2,4-dimethylvaleronitrile and the like.

Moreover, in the case of producing a (meth)acrylic copolymer, a chain transfer agent may be used as needed within a range that does not impair the object and effect of the present invention. Examples of the chain transfer agent include cyanoacetic acid; an alkyl ester compound having 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid; an alkyl ester compound having 1 to 8 carbon atoms of bromoacetic acid; ruthenium, phenanthrene, anthracene, and 9 An aromatic compound such as phenylhydrazine; an aromatic nitro compound such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol or p-nitrotoluene; benzoquinone, 2, a benzoquinone derivative such as 3,5,6-tetramethyl-p-benzoquinone; a borane derivative such as tributylborane; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromo Halogenated hydrocarbon compounds such as ethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, 3-chloro-1-propene; aldehyde compounds such as chloral and furfural: alkyl mercaptan having 1 to 18 carbon atoms a compound; an aromatic thiol compound such as thiophenol or toluene thiol; an alkyl ester compound having 1 to 10 carbon atoms of thioglycolic acid or thioglycolic acid; a hydroxyalkyl thiol compound having 1 to 12 carbon atoms; a terpene compound such as oleene;

The polymerization temperature is usually in the range of from 30 ° C to 180 ° C. In the production of the (meth)acrylic copolymer, a purification step of purifying the polymer obtained by the polymerization reaction may also be provided. Thereby, when the polymer obtained by the solution polymerization method or the like contains an unreacted monomer, the monomer can be removed. As the purification step, it can be appropriately selected from usual purification methods. For example, purification can be carried out by a reprecipitation method using methanol or the like.

(Alkylene oxide modified polyfunctional (meth) acrylate) The adhesive composition of the present invention contains an alkylene oxide-modified polyfunctional (meth) acrylate. The adhesive composition of the present invention contains more than 5 parts by mass and less than 40 parts by mass of the alkylene oxide-modified polyfunctional (meth) acrylate with respect to 100 parts by mass of the (meth)acrylic copolymer. Further, since the adhesive composition of the present invention contains a predetermined amount of an alkylene oxide-modified polyfunctional (meth) acrylate, the height difference is excellent in adhesion and gas floating resistance. Further, the adhesive composition of the present invention contains, as compared with 100 parts by mass of the (meth)acrylic copolymer, less than 40 parts by mass of the alkylene oxide-modified polyfunctional (meth)acrylate. By maintaining or enhancing the adhesion after the ultraviolet irradiation, the members of the touch panel can be firmly adhered without being peeled off from each other.

The alkylene oxide-modified polyfunctional (meth) acrylate may be one having two or more polymerizable unsaturated groups in one molecule, and examples thereof include an alkylene oxide-modified bifunctional (meth)acrylic acid. Ester, alkylene oxide-modified trifunctional (meth) acrylate, and the like. In particular, it is preferred to modify the difunctional (meth) acrylate with an alkylene oxide. By modifying the bifunctional (meth) acrylate with an alkylene oxide, the adhesive composition of the present invention can be formed in an adhesive layer which is more excellent in gas floating resistance.

The alkylene oxide-modified polyfunctional (meth) acrylate is preferably contained in an amount of 7 parts by mass or more and 35 parts by mass or less based on 100 parts by mass of the (meth)acrylic copolymer, and more preferably 10 parts by mass or more and 30 parts by mass or less. Preferably, it is more preferably 15 parts by mass or more and 25 parts by mass or less, and more preferably 20 parts by mass.

The alkylene oxide addition molybdenum of the alkylene oxide-modified polyfunctional (meth) acrylate is preferably 1 mol or more and 8 mol or less, more preferably 3 mol or more and 8 mol or less, and more preferably 4 mol or more. 5 moles are better. When the addition molar amount is 3 mol or more, the hydrophilicity is further enhanced, and the whitening resistance to moisture and heat is excellent. When the addition molar number is 8 mol or less, the compatibility with the (meth)acrylic copolymer is good, and the wet heat whitening property is excellent.

The alkylene oxide-modified polyfunctional (meth) acrylate is preferably a compound represented by the following formula (I).

[Chemical 3] General formula (I)

In the above formula (I), R ₁ and R ₂ each independently represent a methyl group or a hydrogen atom, and R ₃ represents a linear or branched alkyl group having 2 to 6 carbon atoms, and n is 1 or more and 8 or less.

When the alkylene oxide-modified polyfunctional (meth) acrylate is a compound represented by the above formula (I), it has high hydrophilicity and is excellent in wet heat and whitening resistance. Moreover, when the alkylene oxide-modified polyfunctional (meth)acrylate is a compound represented by the above formula (I), since the adhesion after ultraviolet curing can be enhanced, the members of the touch panel can be prevented from peeling off each other. Firmly fit.

In the above formula (I), R ₁ and R ₂ each independently represent a methyl group or a hydrogen atom. Among them, R ₁ and R ₂ are preferably each a hydrogen atom. R ₃ represents a linear or branched alkyl group having 2 to 6 carbon atoms, and examples thereof include a vinyl group, a methyl vinyl group, a propenyl group, a methacryl group, a butenyl group, a pentenyl group, and a hexenyl group. Wait. Among them, as R ₃ , a vinyl group or a methyl vinyl group is preferable.

The alkylene oxide-modified polyfunctional (meth)acrylate represented by the above formula (I) preferably has 3 or more and 8 or less, more preferably 4 or more and 5 or less. Since n is 3 or more, the hydrophilicity is high, and since n is 8 or less, the compatibility with the (meth)acrylic copolymer is high, and as a result, the wet heat whitening resistance is further improved.

Further, the alkylene oxide-modified polyfunctional (meth) acrylate is more preferably a compound represented by the following formula (II).

[Chemical 4] General formula (II)

In the above formula (II), R ₁ and R ₂ each independently represent a methyl group or a hydrogen atom, R ₄ represents a linear or branched alkyl group having 1 to 3 carbon atoms, or a hydrogen atom, and n is 1 or more and 8 or less. .

When the alkylene oxide-modified polyfunctional (meth) acrylate is a compound represented by the above formula (II), it has higher hydrophilicity and is more excellent in moist heat whitening resistance. Moreover, in particular, the compound represented by the above formula (II) can further enhance the adhesion after ultraviolet curing, and the members of the touch panel can be more firmly bonded without being peeled off from each other.

In the formula (II), R ₁ and R ₂ each independently represent a methyl group or a hydrogen atom. Among them, R ₁ and R ₂ are preferably each a hydrogen atom. Further, R ₄ represents a linear or branched alkyl group or a hydrogen atom having a carbon number of 1 to 3. Among them, as R ₄ , a methyl group or a hydrogen atom is more preferable, and a hydrogen atom is more preferable.

The alkylene oxide-modified polyfunctional (meth)acrylate represented by the above formula (II) preferably has 3 or more and 8 or less, more preferably 4 or more and 5 or less. Since n is 3 or more, the hydrophilicity is higher, and since n is 8 or less, the compatibility with the (meth)acrylic copolymer is higher, and as a result, the wet heat whitening resistance is further improved.

When the alkylene oxide-modified polyfunctional (meth) acrylate is at least one of an ethylene oxide-modified polyfunctional (meth) acrylate and a propylene oxide-modified polyfunctional (meth) acrylate, From the viewpoint of the cohesive force of the adhesive layer and the viewpoint of resistance to gas floating, it is preferable.

Examples of the ethylene oxide-modified polyfunctional (meth) acrylate include an ethylene oxide-modified bifunctional (meth) acrylate, an ethylene oxide-modified trifunctional (meth) acrylate, and the like; Examples of the propylene oxide-modified polyfunctional (meth) acrylate include a propylene oxide-modified bifunctional (meth) acrylate and a propylene oxide-modified trifunctional (meth) acrylate. Particularly preferred is an ethylene oxide-modified bifunctional (meth) acrylate or propylene oxide-modified bifunctional (meth) acrylate. By using these modified bifunctional (meth) acrylates, the adhesive composition of the present invention can be formed in an adhesive layer which is more excellent in gas floating resistance.

The ethylene oxide-modified bifunctional (meth) acrylate is preferably ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, or triethylene glycol di(methyl). Acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, hexanediol EO modified diacrylate, bisphenol A EO modified di(tri)acrylate, Isocyanuric acid EO modified diacrylate or the like.

The ethylene oxide-modified trifunctional (meth) acrylate is preferably: trimethylolpropane EO addition tris(meth)acrylate, isomeric cyanuric acid EO-modified tri(meth)acrylate, or the like. .

The propylene oxide-modified bifunctional (meth) acrylate is preferably dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl Alcohol PO modified diacrylate or the like.

The propylene oxide-modified trifunctional (meth) acrylate is preferably trimethylolpropane PO addition tris(meth)acrylate or the like.

The tetrafunctional or higher modified polyfunctional (meth) acrylate is not particularly limited, and examples thereof include neopentyl alcohol EO-modified tetra(meth) acrylate and neopentyl alcohol PO-modified tetra(methyl). Acrylate and the like.

(Monofunctional (meth) acrylate) The content of the monofunctional (meth) acrylate in the adhesive composition of the present invention is less than 10% by mass based on 100 parts by mass of the (meth)acrylic copolymer. Share.

The monofunctional (meth) acrylate is not limited as long as it has one polymerizable unsaturated group in one molecule, and a known monofunctional (meth) acrylate can be used.

The monofunctional (meth) acrylate is preferably a vapor pressure at 25 ° C of 300 Pa or less, more preferably 200 Pa or less, and even more preferably 100 Pa or less. Further, the vapor pressure of the monofunctional (meth) acrylate can be measured by JIS K2258-1 "Calculation of Crude Oil and Petroleum Products - Vapor Pressure".

Further, the melting point of the monofunctional (meth) acrylate is preferably 25 ° C or lower. Thereby, the transparency of the adhesive layer formed using the adhesive composition of the present invention is enhanced.

Examples of the monofunctional (meth) acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and (methyl). Amyl acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (methyl) Isodecyl acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, lauryl (meth) acrylate, stearic acid (meth) acrylate a linear or branched alkyl group having a carbon number of 1 to 18, such as an ester, isostearyl (meth)acrylate, isodecyl (meth)acrylate or 2-ethylhexyl (meth)acrylate The alkyl acrylate and the derivatives thereof, particularly isodecyl (meth) acrylate, are preferred from the viewpoint of the cohesive force of the adhesive layer and the gas floating resistance.

The monofunctional (meth) acrylate is preferably contained in an amount of 8 parts by mass or less, more preferably 6 parts by mass or less, and more preferably 5 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer. The following is even better. Further, the monofunctional (meth) acrylate is not contained in the binder composition (the content is 0 parts by mass).

(Crosslinking Agent) The adhesive composition of the present invention contains a crosslinking agent. The crosslinking agent is not particularly limited, and examples thereof include a polyisocyanate compound, a polyepoxy compound, a polyaziridine compound, a melamine formaldehyde condensate, a metal salt, and a metal chelate compound. These crosslinking agents may be used alone or in combination of two or more.

Among these crosslinking agents, a polyisocyanate compound is preferred from the viewpoint of the reactivity of the crosslinking reaction and the stability to environmental changes after crosslinking.

Examples of the polyisocyanate compound include aromatic polyisocyanate compounds such as phenyl diisocyanate, diphenyl methyl diisocyanate, triphenyl methyl triisocyanate, and toluene diisocyanate. For example: an aliphatic or alicyclic polyisocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogen addition of an aromatic polyisocyanate compound; dimer or tris of such polyisocyanate compounds; a polymer; an adduct between the polyisocyanate compound and a polyol compound such as trimethylolpropane or the like. Among them, at least one selected from the group consisting of dimers, trimers and adducts of hexamethylene diisocyanate and hexamethylene diisocyanate, diisocyanate The trimer of the acid hexamethylene ester is particularly preferred. These polyisocyanate compounds may be used alone or in combination of two or more.

For the polyisocyanate compound, for example, "CORONATE HX", "CORONATE HL-S", "CORONATE 2234", "AQUANATE 200", "AQUANATE 210" (above, manufactured by Japan Polyurethane Co., Ltd.), "DESMODUR" can be used. N3300", "DESMODUR N3400" (above is Sumitomo Bayer Polyurethane Co., Ltd.), "DURANATE E-405-80T", "DURANATE 24A-100", "DURANATE TSE-100" (above is manufactured by Asahi Kasei Industrial Co., Ltd.) ), "TAKENATE D-110N", "TAKENATE D-120N", "TAKENATE M-631N", "MT-OLESTER NP1200" (above is Mitsui Takeda Chemical Co., Ltd.) and other trade names are commercially available.

When the amount of the crosslinking agent is 0.05 parts by mass or more and 1.0 part by mass or less based on 100 parts by mass of the (meth)acrylic copolymer, it is preferable from the viewpoint of resistance to gas floating property and height difference, and is contained in an amount of 0.1 part by mass or more. It is more preferably 0.5 parts by mass or less, more preferably 0.15 parts by mass or more and 0.3 parts by mass or less.

In addition to the crosslinking agent, the adhesive composition of the present invention preferably further contains a crosslinking catalyst from the viewpoint of accelerating the initial curing rate. Examples of the crosslinking catalyst include an organic tin compound such as dibutyltin laurate or dioctyltin laurate; and an organic zirconium compound such as dibutoxy bis(ethylacetonitrile zirconium acetate).

When the adhesive composition of the present invention contains a crosslinking catalyst, it is preferred to further contain a chelating agent. Examples of the chelating agent include β-diketones and β-ketoesters. Examples of the β-diketone or the β-ketoester include acetamidineacetone, ethyl acetonitrile acetate, ethyl acetate, n-propyl acetate, and isopropyl acetate. Among these chelating agents, a good balance between the pot life and the reaction rate of the adhesive composition is considered, and acetamidine is preferred.

(Photopolymerization initiator) The binder composition of the present invention may further contain a photopolymerization initiator. The photopolymerization initiator is not particularly limited as long as it is a polymerization reaction of the modified polyfunctional (meth) acrylate by irradiation with ultraviolet rays.

Examples of the photopolymerization initiator include an acetophenone-based initiator, a benzoin ether-based initiator, a benzophenone-based initiator, a hydroxyalkylphenone-based initiator, and a thioxantate. A ketone-based initiator, an amine-based initiator, and the like. Examples of the acetophenone-based initiator include diethoxyacetophenone and benzyldimethylketal. Examples of the benzoin ether-based initiator include benzoin and benzoin methyl ether. Examples of the benzophenone-based initiator include benzophenone and methyl o-besylbenzoate. The hydroxyalkyl phenyl ketone-based initiator may, for example, be 1-hydroxy-cyclohexyl-phenyl-ketone or the like. Examples of the thioxanthone-based initiator include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone. Examples of the amine-based initiator include triethanolamine and ethyl 4-dimethylbenzoate. One type of the photopolymerization initiator may be used alone or two or more types may be used in combination.

The content of the photopolymerization initiator is preferably 0.1 parts by mass or more and 20 parts by mass or less, and more preferably 0.2 parts by mass or more and 10 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer. More preferably, it is more preferably 0.3 parts by mass or more and 5 parts by mass or less.

Further, the adhesive composition of the present invention may be added with a solvent in order to improve the coating property to a glass substrate, a transparent conductive film, a pattern film or the like.

Examples of the solvent include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; dichloromethane, trichloroethane, and trichloroethylene. Halogenated hydrocarbons such as tetrachloroethylene and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and diacetone; diethyl ether, diisopropyl ether, and Ethers such as alkane and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, etc. Esters; polyhydric alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, and the like.

(Other components) The adhesive composition of the present invention includes, in addition to a (meth)acrylic copolymer, a modified polyfunctional (meth)acrylate, a monofunctional (meth)acrylate, a photopolymerization initiator, and In addition to the crosslinking agent, if necessary, it may suitably contain a weathering stabilizer, a tackifier, a plasticizer, a softener, a release aid, a dye, a pigment, an inorganic filler, a surfactant, an antioxidant, and an anti-corrosion agent. A metal etchant, a decane coupling agent, a UV absorber, a light stabilizer such as a hindered amine compound, and the like.

[Adhesive Sheet] The adhesive sheet of the present invention has an adhesive layer which is thermally cured by the above-described adhesive composition. Examples of the adhesive sheet include those in which a pressure-sensitive adhesive layer is formed on a protective sheet (release sheet) which is peeled off during use, and both sides of the adhesive layer are held by a protective sheet.

The protective sheet is not particularly limited as long as it is a structure that supports the adhesive layer and can be peeled off from the adhesive layer. Examples of the protective sheet include plastic films such as polyester, polystyrene, styrene-acrylic copolymer, acrylic resin, polycarbonate, polyetheretherketone, and triacetylcellulose. Among them, a polyester film is preferable, and a polyethylene terephthalate film is more preferable. Further, in order to facilitate the peeling between the protective sheet and the adhesive layer, the release treatment may be carried out by using a release agent such as a fluorine resin, a paraffin wax or a silicone resin.

The adhesive sheet is obtained by applying the adhesive composition of the present invention to a protective sheet, drying it, and then crosslinking the adhesive layer composed of the adhesive composition. Examples of the method of applying the adhesive composition to the protective sheet include a dipping method using a liquid adhesive composition, a coating method, an inkjet method, and the like. Among them, the coating method is preferably used. As described above, the protective sheet may be attached to one side of the protective sheet on which the adhesive layer is not provided, and the adhesive sheet may be sandwiched between the protective sheets on both sides of the adhesive layer.

The adhesive composition applied to the protective sheet (release sheet) is dried to remove the liquid component, and then cooked in a predetermined temperature and humidity environment. Thereby, the adhesive sheet composed of the adhesive composition is hardened (thermally hardened) to obtain the adhesive sheet of the present invention. As a condition for ripening, for example, when a polyisocyanate compound is used as a crosslinking agent, the temperature is 20 to 45 ° C / the relative humidity is 40 to 60%, and the mixture is aged for 3 to 5 days.

The adhesive composition of the present invention contains a modified polyfunctional (meth) acrylate, and may further contain a photopolymerization initiator. At this time, after the adhesive composition is applied to the protective sheet, even if the adhesive composition is thermally cured to form an adhesive layer, the modified polyfunctional (meth) acrylate using a photopolymerization initiator is used. The polymerization has not yet proceeded, or only slightly. Therefore, the photopolymerization initiator and the modified polyfunctional (meth)acrylate remain in the cured adhesive layer, and the adhesive layer can be hardened (ultraviolet-cured) by irradiation of ultraviolet rays.

Before the curing by ultraviolet irradiation, the adhesive layer after the heat curing contains a predetermined amount of the modified polyfunctional (meth) acrylate, so that a soft adhesive layer can be formed on the protective sheet. Moreover, since the adhesive layer is soft, even if the adhesive layer is transferred onto a film or member having a height difference, the height difference can be attached. Further, after the transfer of the adhesive layer, when the ultraviolet ray is irradiated onto the adhesive layer to be hardened, since the adhesive layer exhibits high elasticity, excellent gas floating resistance can be obtained.

Further, although the adhesive layer after thermosetting contains a monofunctional (meth) acrylate, its content is small. Therefore, even if the adhesive layer is hardened by ultraviolet irradiation, the adhesive layer exhibits higher elasticity than the adhesive layer containing more monofunctional (meth) acrylate, and is excellent in gas floating resistance.

Further, since the adhesive composition of the present invention contains a modified polyfunctional (meth) acrylate, the adhesive layer which is cured by irradiation with ultraviolet rays after heating maintains the adhesion of the adhesive layer which is heated and hardened. Or it becomes higher than its adhesion. That is, the adhesive layer containing the modified polyfunctional (meth) acrylate can be maintained or improved in adhesion by curing by irradiation with ultraviolet rays. That is, the members of the touch panel can be firmly adhered to each other without being peeled off from each other.

The thickness of the adhesive layer is not particularly limited, and can be selected, for example, in the range of 20 μm to 300 μm depending on the application.

(Gel fraction) The gel fraction (crosslinking degree) of the adhesive layer after heat hardening and ultraviolet curing is considered to be 50% by mass or more and 99 mass in view of the dependency of the height difference and the gas floating resistance. % or less is more preferably 60% by mass or more and 80% by mass or less. Since the gel fraction is within this range, the cohesive force of the adhesive layer becomes high, and the gas floating resistance is excellent. In the present specification, the gel fraction refers to the mass of the portion of the gel which cannot be dissolved and is dissolved when the sample (adhesive layer) after the thermosetting and ultraviolet curing is dissolved in a specific solvent, and before the dissolution by the solvent. The ratio of mass (percentage).

(Method for Measuring Gel Fraction Ratio) The gel fraction was measured by the method shown in the following (1) to (5). (1) A solution of the adhesive composition was applied onto a release paper, air-dried at room temperature for 30 minutes, and then subjected to main drying at 100 ° C for 5 minutes to form a film-like adhesive layer. (2) The above adhesive layer is cooked under a predetermined temperature and humidity environment (in the case where the crosslinking agent is a polyisocyanate compound, the adhesive layer is aged for 4 days in an environment of 23 ° C and a relative humidity of 50%) After the heat hardening was sufficiently performed, ultraviolet rays of 500 mJ/cm ² were irradiated to the adhesive layer. In addition, whether or not the thermal hardening has sufficiently proceeded can be judged by whether or not the gel fraction has not changed with time. For example, the gel fraction of the fourth day of ripening is the same as the gel fraction of the fifth day. (For example, 60%), it can be judged that the heat curing has been sufficiently performed on the fourth day of the ripening. (3) The film-like adhesive layer cut to 75 mm × 75 mm after weighing by a precision balance was attached to a metal mesh of 250 mesh and 100 mm × 100 mm, and dried in a drier for 1 hour. Thereafter, the quality is weighed using a precision balance. (4) The weighed sample was wrapped with a metal mesh in such a manner that the adhesive layer did not leak out during solvent immersion, and was left to stand in a solvent (ethyl acetate) for 72 hours. (5) After the solvent is immersed, the metal mesh is dried, and the mass is weighed using a precision balance. The gel fraction was calculated from the mass change before and after the immersion by the following formula. Gel fraction [% by mass] = 100-[(AB)/(CB)] × 100 where A represents the total mass (g) of the metal mesh and the adhesive layer after solvent impregnation, and B represents the mass of the gold mesh (g), C represents the total mass (g) of the metal mesh and the adhesive layer before solvent impregnation.

The adhesive layer after heat hardening is irradiated with ultraviolet rays to make the adhesive layer harder. When the adhesive layer is further hardened, for example, ultraviolet rays of 500 mJ/cm ² may be applied to the adhesive layer. [Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by the examples. In addition, "parts" and "%" are quality benchmarks unless otherwise specified.

[Production Example 1] - Preparation of Acrylic Copolymer - 350 parts of ethyl acetate (organic solvent for polymerization) was fed to a reaction apparatus equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer. Then, in another container, 225 parts by mass of lauryl acrylate (LA) (15 mass% based on the total mass of the acrylic copolymer) and 570 parts by mass of n-butyl acrylate (BA) were prepared (also in relation to The total mass of the acrylic copolymer was 38% by mass), 405 parts by mass of methyl acrylate (MA) (also 27% by mass based on the total mass of the acrylic copolymer), and 300 parts by mass of 2-hydroxyethyl acrylate (2HEA) 1500 parts by mass of the monomer mixture (also 20% by mass based on the total mass of the acrylic copolymer), 300 parts by mass of which (20% by mass of the monomer mixture) is fed to the reaction apparatus, heated, and The reflux was carried out for 10 minutes at the reflux temperature. Then, the remaining 1200 parts of the above monomer mixture (80% by mass of the monomer mixture), 32 parts of ethyl acetate and 0.12 parts of 2,2'-azobis (2,4) were refluxed. -Dimethylvaleronitrile), which was successively added dropwise over 120 minutes, and then subjected to polymerization for 30 minutes. Thereafter, a mixture of 15 parts of ethyl acetate and 0.13 parts of tributyl butyl peroxypivalate was successively added dropwise over 40 minutes, and further polymerization was carried out for 150 minutes. After completion of the reaction, the solid content was diluted with ethyl acetate to 42% to obtain a solution of an acrylic copolymer (Production Example 1).

The obtained acrylic copolymer had a weight average molecular weight of 500,000 and a molar average glass transition temperature (molTg) of -30 °C. Further, the weight average molecular weight and the molar average glass transition temperature were measured by the above method.

[Example 1] - Preparation of the adhesive composition - a solution of the acrylic copolymer (Mw = 500,000, Tg = -30 ° C) of Production Example 1 with respect to 238.1 parts by mass (solid content: 100 parts by mass) 10 parts by mass of VISCOAT #335HP (tetraethylene glycol diacrylate (4EGDA), manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a modified polyfunctional (meth) acrylate, and a solid content meter 0.2 parts by mass of D-110N (manufactured by Mitsui Takeda Chemical Co., Ltd.) as a crosslinking agent, and 0.3 parts by mass of IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl group) as a photopolymerization initiator - Ketone, manufactured by BASF Corporation), and mixed to prepare an adhesive composition.

- Preparation of adhesive sheet - The prepared adhesive composition was applied to a PET film, dried under 100 ° C × 2 minutes of drying conditions, and aged at a temperature of 23 ° C / a relative humidity of 50%. Made into a bonding piece in the sky. The thickness of the adhesive layer after the heat treatment was 50 μm.

- Evaluation Results - The following is an evaluation of the gel fraction of the adhesive layer formed on the adhesive sheet, the resistance to moist heat whitening, the attachment of the height difference, the resistance to gas floating, and the adhesion. The results are shown in Table 2.

(Gel fraction) The gel fraction was measured by the methods shown in the following (1) to (5). (1) A solution of the adhesive composition was applied onto a release paper, air-dried at room temperature for 30 minutes, and then main dried at 100 ° C for 5 minutes to form a film-like adhesive layer. (2) The above adhesive layer was aged for 4 days in an environment of 23 ° C and a relative humidity of 50%. Thereafter, ultraviolet rays of 500 mJ/cm ² were irradiated to the adhesive layer. (3) The above-mentioned film-like adhesive layer cut into 75 mm × 75 mm by a weighing balance weighing quality was attached to a 250 mesh, 100 mm × 100 mm metal mesh, and dried in a drier for 1 hour. Thereafter, the quality is weighed using a precision balance. (4) The weighed sample was wrapped with a metal mesh in such a manner that the adhesive layer did not leak out during solvent immersion, and was left to stand in a solvent (ethyl acetate) for 72 hours. (5) After the solvent is immersed, the metal mesh is dried, and the mass is weighed using a precision balance. The gel fraction was calculated from the mass change before and after the immersion by the following formula. Gel fraction [% by mass] = 100-[(AB)/(CB)] × 100 where A represents the total mass (g) of the metal mesh and the adhesive layer after solvent impregnation, and B represents the metal mesh Mass (g), C represents the total mass (g) of the metal mesh and the adhesive layer before solvent impregnation.

(Damp heat and whitening resistance) A size of 80 mm in width × 60 mm in length was cut from the produced bonding sheet as a test bonding sheet. Then, after the ultraviolet ray was irradiated under conditions of 500 mJ/cm ² to cure the adhesive layer, the adhesive layer was superposed on a glass plate having a thickness of 1.8 mm (optical soda glass manufactured by Songlang Glass Industry Co., Ltd.), and a desktop stack was used. The test sample was prepared by crimping and the haze (HAZE) was measured before the test was put into operation. Thereafter, it was allowed to stand in an environment of 85 ° C - 90% RH for 250 hours, and after cooling at 23 ° C - 50% RH for 10 minutes, the haze (haze after the test was put) was measured. In addition, the haze was measured using an NDH 5000SP manufactured by Nippon Denshoku Co., Ltd. The haze after the input test was subtracted from the value (ΔH) of the haze before the input test, and the wet heat whitening resistance was evaluated by the following evaluation criteria. <Evaluation Criteria> A: ΔH = less than 1.0 B: ΔH = 1.0 or more and less than 2.0 C: ΔH = 2.0 or more

(Following height difference) A member having a height difference of 30 μm (printing a screen on a PET film and forming a height difference of 30 μm) is bonded to an adhesive layer having a film thickness of 50 μm. sheet. Then, the member to which the adhesive sheet was bonded was subjected to autoclave treatment (5 atm, 50 ° C / 20 minutes), and then the ultraviolet ray was irradiated under conditions of 500 mJ/cm ² to cure the adhesive layer. Then, the member was placed in a hot air dryer at 85 ° C for 1 hour, and the distance at which the bubbles were joined was measured, and the value of the height difference was determined. The evaluation criteria are as follows. <Evaluation Criteria> A: Less than 10mm B: Less than 10mm above 10mm C: 15mm or more

(Gas-resistant floating property) The adhesive layer of the formed adhesive sheet was attached to a PC (polycarbonate substrate) and subjected to autoclave treatment (5 atm, 40 ° C / 20 min). The adhesive layer is cured by irradiating ultraviolet rays under the same conditions as the height difference. Then, the PC to which the adhesive layer was attached was placed in a hot air dryer at 85 ° C for 24 hours. Thereafter, the adhesive layer was visually observed from the PET film side, and the number of identifiable bubbles in the adhesive layer was counted, and the gas floating resistance was evaluated by the following evaluation criteria. <Evaluation criteria> A: Bubbles are 0 B: Bubbles are 1 to 3 C: Bubbles are 4 or more

(Adhesion) The adhesion of the adhesive layer before UV curing (after heat treatment) and the adhesion of the adhesive layer after UV curing were evaluated. First, the adhesive layer of the formed adhesive sheet was bonded to a 100 μm PET film which was subjected to an easy adhesion treatment. The adhesive sheet was cut into 25 mm × 150 mm, and the cut adhesive sheet was crimped to the surface of the glass plate as a test sample according to the method of JIS Z-0237. After the test sample was allowed to stand under conditions of 23 ° C and 50% RH for 24 hours, the adhesion of the 180 ゚ peeling force was measured, and the peel strength (N/inch) of the adhesive layer before UV hardening was measured by a peeling speed of 300 mm/min. .

Further, the adhesive layer of the produced adhesive sheet was irradiated with ultraviolet rays under conditions of 500 mJ/cm ² to cure the adhesive layer. Thereafter, it was bonded to a 100 μm PET film which was subjected to an easy adhesion treatment. The adhesive sheet was cut into 25 mm × 150 mm, and the cut adhesive sheet was crimped to the surface of the glass plate as a test sample according to the method of JIS Z-0237. After the sample was allowed to stand under conditions of 23° C. and 50% RH for 24 hours, the peeling strength (N/inch) of the adhesive layer after ultraviolet curing was measured by using a peeling speed of 300 mm/min. The adhesion after UV hardening was evaluated by the following evaluation criteria. <Evaluation Criteria> A: Adhesive force is 20 N/inch or more B: Adhesive force is 15 N/inch or more and less than 20 N/inch C: Adhesive force is less than 15 N/inch

[Examples 2 to 6] The preparation of the adhesive composition and the production of the adhesive sheet were carried out in the same manner as in Example 1 except that the components of the adhesive composition were changed as shown in Table 2, and the evaluation was carried out. The gel fraction of the adhesive layer on the adhesive sheet, the resistance to moisture and heat whitening, the attachment of the height difference, the resistance to gas floating and the adhesion. The results are shown in Table 2.

[Example 7] The modified polyfunctional (meth) acrylate contained in the adhesive composition was changed to propylene oxide-modified polyfunctional (meth) acrylate (3PGDA) as shown in Table 2, and The preparation of the adhesive composition and the production of the adhesive sheet were carried out in the same manner as in Example 2, and various evaluations were carried out. The results are shown in Table 2.

[Examples 8 to 10] In Examples 8 to 10, the preparation of the adhesive composition and the bonding were carried out in the same manner as in Example 2 except that the (meth)acrylic copolymer contained in the adhesive composition was changed. The production of the film. The composition of the (meth)acrylic copolymer of each example is shown in Table 1. Moreover, the results of the various assessments are shown in Table 2.

【Table 1】

[Comparative Examples 1 to 7] Preparation of the adhesive composition, production of the adhesive sheet, and evaluation of formation were carried out in the same manner as in Example 1 except that the components of the adhesive composition were changed as shown in Table 2. The gel fraction of the adhesive layer on the adhesive sheet, moisture and heat whitening resistance, height difference attachment, gas floating resistance and adhesion. The results are shown in Table 2.

Further, the polyfunctional acrylates shown in Table 2 are as follows. IBXA is an isodecyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., EO mole number 0, functional group number 1). 4EGDA is a tetraethylene glycol diacrylate (Osaka Organic Chemical Industry Co., Ltd., EO Moore) Number 4, functional group number 2) 3EGDA system represents triethylene glycol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., EO mole number 3, functional group number 2) TMP6EOA system represents trimethylolpropane EO (6) plus Into trisacrylate (manufactured by Kyoeisha Chemical Co., Ltd., EO mole number 6, functional group number 3) 1,6HDDA system shows 1,6-hexanediol diacrylate (Kyoeisha Chemical Co., Ltd., EO Molar number 0, functional group number 2) TMPTA system represents trimethylolpropane triacrylate (manufactured by Kyoeisha Chemical Co., Ltd., EO mole number 0, functional group number 3) PETIA series shows neopentyl alcohol triacrylate (manufactured by Kyoeisha Chemical Co., Ltd., EO mole number 0, functional group number 3) 3PGDA is a polypropylene glycol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., PO mole number 3, functional group number 2)

In the case of the (meth)acrylic copolymer of 100 parts by mass, the monofunctional (meth) acrylate is less than 10 parts by mass, and is resistant to gas floating, as compared with the example 2, the example 6 and the comparative example 2. excellent. In addition, in the case of the (meth)acrylic copolymer, the modified polyfunctional (meth)acrylate was more than 5 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer, as described in Examples 1 to 10, Comparative Example 1, and Comparative Example 6. Then the height difference is excellent. Moreover, it is understood from Examples 1 to 10 and Comparative Example 7 that the modified polyfunctional (meth)acrylate is not more than 40 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer. Excellent floatability and adhesion. Further, from Examples 1 to 10 and Comparative Examples 3 to 5, it was found that when the modified polyfunctional (meth)acrylate was used, the wet heat whitening resistance was obtained when the unmodified polyfunctional (meth)acrylate was used. excellent.

From the results of Examples 1 to 10, it was found that the adhesion of the adhesive layer between the UV curing and the UV curing was compared, and the adhesion was maintained or improved by performing UV curing. Further, from the results of Example 1 and Examples 8 to 10, it was found that the ratio of the monomer having a hydroxyl group in the (meth)acrylic copolymer can be increased to improve the moist heat whitening resistance.

no

Claims (10)

An adhesive composition comprising: a (meth)acrylic copolymer containing a constituent unit derived from a monomer having a hydroxyl group, and more than 5 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer And less than 40 parts by mass of the alkylene oxide-modified polyfunctional (meth) acrylate, and a crosslinking agent; and the content of the monofunctional (meth) acrylate thereof is relative to 100 parts by mass of the (meth)acrylic acid The copolymer is less than 10 parts by mass. The adhesive composition according to claim 1, wherein the alkylene oxide-modified polyfunctional (meth) acrylate has an alkylene oxide addition molar number of from 1 mol to 8 mol. The adhesive composition according to claim 1 or 2, wherein the alkylene oxide-modified polyfunctional (meth) acrylate is an alkylene oxide-modified bifunctional (meth) acrylate. The adhesive composition according to claim 1 or 2, wherein the alkylene oxide-modified polyfunctional (meth) acrylate is a compound represented by the following formula (I); In the formula (I), R ₁ and R ₂ each independently represent a methyl group or a hydrogen atom, and R ₃ represents a linear or branched alkyl group having a carbon number of 2 to 6, and n is 1 Above 8 or less. The adhesive composition of claim 4, wherein n in the formula (I) is 3 or more and 8 or less. The adhesive composition of claim 1 or 2, wherein the crosslinking agent is a polyisocyanate compound. The adhesive composition of claim 1 or 2 further contains a photopolymerization initiator. The adhesive composition according to claim 1 or 2, wherein a content of the constituent unit derived from the monomer having a hydroxyl group of the (meth)acrylic copolymer is relative to the (meth) The total mass of the acrylic copolymer is 5% by mass or more and 40% by mass or less. The adhesive composition of claim 1 or 2 is used for a touch panel. An adhesive sheet having an adhesive layer obtained by thermally hardening an adhesive composition according to any one of claims 1 to 9.