KR20130094724A - Acrylic resin solution, acrylic adhesive compositon, acrylic adhesive, adhesive sheet, acrylic adhesive for optical member, and optical member with adhesive layer - Google Patents

Abstract

Provided is a cross-linking agent curing type acrylic pressure-sensitive adhesive capable of thick coating and capable of obtaining a pressure-sensitive adhesive layer of a thick film. This invention contains the weight average molecular weights 50,000-300,000 acrylic resin (A), and the organic solvent (B) whose chain transfer constant to the organic solvent of vinyl acetate at 60 degreeC becomes 250 or more, and solid content concentration is It relates to an acrylic resin solution, characterized in that more than 60%.

Description

Acrylic resin solution, acrylic adhesive composition, acrylic adhesive, pressure-sensitive adhesive sheet, acrylic adhesive for optical members, optical member with adhesive layer {acrylic resin solution, acrylic adhesive compositon, acrylic adhesive, adhesive sheet, acrylic adhesive for optical member, and optical member with adhesive layer}

The present invention relates to an acrylic resin solution, an acrylic pressure-sensitive adhesive composition, an acrylic pressure-sensitive adhesive, an adhesive sheet, an acrylic pressure-sensitive adhesive for an optical member, and an optical member with an adhesive layer, and specifically, an inert energy ray-curable solvent-based acrylic pressure-sensitive adhesive suitable for thick coating. It relates to an acrylic resin solution used for the preparation of the resin.

Conventionally, acrylic adhesives have various types of pressure-sensitive adhesives such as strongly adhesives for the purpose of firmly sticking adherends for a long time, and peeling-type adhesives on the premise of peeling off adherends after pasting. Adhesives with optimized adhesive properties have been designed and used in various fields.

In recent years, the performance required for the pressure-sensitive adhesive is required not only for adhesive physical properties such as adhesive strength but also for adhesion of glass substrates in liquid crystal displays, etc., when the adhesive layer itself is used for transparency and impact absorption resistance. In order to improve the shock absorption performance, it is proposed to thicken the thickness of an adhesive layer.

Moreover, the method of hardening | curing an adhesive and obtaining an adhesive layer of a thick film is known by irradiating active energy rays, such as an ultraviolet-ray, as a method of making an adhesive layer thick (thick film coating) using acrylic resin. (See, for example, patent documents 1 and 2.)

Since the said active energy ray hardening-type adhesive is a non-solvent type adhesive which generally does not contain the solvent used for viscosity adjustment with a normal acrylic adhesive, and uses a photopolymerizable unsaturated monomer as a diluent monomer instead of a solvent, There is no need for a drying step for blowing off the solvent after coating, and an adhesive layer can be obtained efficiently in a short time even when thick coating is applied.

(Patent Document 1) JP 2007-94191 A (Patent Document 2) JP 2007-314618 A

However, in general, when the adhesive tape is applied to a curved surface, an uneven surface, or the like, since followability to the adherend is required, a thin and soft material is used for the support film in which the adhesive layer is formed on the adhesive tape. When such an active thin film is irradiated using the active energy ray-curable pressure-sensitive adhesive to such a thin and soft support film, there is a possibility that the support film is damaged by the influence of heat or the like.

Therefore, in the application which requires sticking to such curved surfaces and uneven surfaces, even when trying to obtain a pressure-sensitive adhesive layer of a thick film, an active energy ray-curable pressure-sensitive adhesive cannot be used, but a solvent type in which the pressure-sensitive adhesive layer is formed by crosslinking with a crosslinking agent. It is necessary to obtain the adhesive layer of a thick film | membrane using acrylic adhesive.

Therefore, in the present invention, under such a background, it is possible to obtain a thick coating and obtain a pressure-sensitive adhesive layer of a thick film, and also an acrylic resin solution used for the production of a crosslinking agent-curable type acrylic pressure-sensitive adhesive having excellent adhesive properties and transparency, It aims at providing the used acrylic adhesive composition, an acrylic adhesive, an adhesive sheet, the adhesive for optical members, and the optical member with an adhesive layer.

Therefore, as a result of intensive studies in view of such circumstances, the present inventors have found that acrylic resins having a relatively low molecular weight and low viscosity and an organic solvent exhibiting a specific chain transfer constant among acrylic resins used for ordinary pressure-sensitive adhesive applications. By using an acrylic resin solution (acrylic pressure-sensitive adhesive composition) having a high solid content concentration, it is possible to coat the coating thickly to obtain a pressure-sensitive adhesive, so that no drop of liquid occurs during coating and the drying of the solvent can be facilitated. In addition, the obtained pressure-sensitive adhesive layer was found to be excellent in adhesive force, retention force, and transparency, and thus, the present invention was completed.

That is, the summary of this invention contains the weight average molecular weight 50,000-300,000 acrylic resin (A), and the organic solvent (B) whose chain transfer constant to the organic solvent of vinyl acetate at 60 degreeC becomes 250 or more, And a solid content concentration of 60% or more.

Moreover, it is related with the acrylic adhesive composition containing such an acrylic resin solution, the acrylic adhesive and adhesive sheet obtained using the said acrylic adhesive composition, the acrylic adhesive for optical members, and the optical member with an adhesive layer.

The present invention includes the following aspects.

[1] A weight average molecular weight of 50,000 to 300,000 acrylic resin (A) and an organic solvent (B) in which the chain transfer constant of the vinyl acetate to the organic solvent of vinyl acetate at 60 ° C is 250 or more, and the solid content concentration is Acrylic resin solution, characterized in that more than 60%.

[2] The acrylic resin solution according to [1], wherein the acrylic resin solution has a viscosity of 20,000 mPa · s / 25 ° C or less.

[3] The acrylic resin solution according to [1] or [2], wherein the acrylic resin (A) does not contain an acidic group.

[4] The acrylic resin solution according to any one of [1] to [3], wherein 50% by weight or more of the organic solvent (B) is methyl ethyl ketone.

[5] The acrylic resin solution according to any one of [1] to [4], wherein 60% by weight or more of the total solid in the acrylic resin solution is acrylic resin (A).

[6] An acrylic pressure-sensitive adhesive composition containing the acrylic resin solution according to any one of [1] to [5].

[7] The acrylic pressure-sensitive adhesive composition according to [6], which contains a crosslinking agent (C).

[8] An acrylic pressure sensitive adhesive, wherein the acrylic pressure sensitive adhesive composition according to [6] or [7] is crosslinked.

[9] An adhesive sheet containing an adhesive layer containing an acrylic adhesive according to [8].

[10] An adhesive sheet having a pressure-sensitive adhesive layer obtained by coating and drying the acrylic pressure-sensitive adhesive composition according to [6] or [7] with a film thickness of 80 μm or more on a substrate, wherein the film thickness of the pressure-sensitive adhesive layer after drying is 50 μm or more. The adhesive sheet characterized by the above-mentioned.

[11] An acrylic pressure sensitive adhesive for optical members, comprising the acrylic pressure sensitive adhesive according to [8].

[12] An optical member with an adhesive layer, including an adhesive layer containing an acrylic adhesive according to [8], and an optical member.

In order that the acrylic resin solution of this invention contains specific acrylic resin and an organic solvent, it becomes possible to have high solid content concentration which was difficult to be compatible in the acrylic resin solution for manufacturing the acrylic adhesive of a normal solvent system, Even when the coating is made thick using such an acrylic resin solution to obtain an acrylic pressure-sensitive adhesive, liquid drops and coating roots do not occur during coating, and drying of the solvent can be facilitated. Excellent adhesion, retention, transparency, corrosion resistance.

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is demonstrated in detail, these show an example of preferable embodiment.

In the present invention, (meth) acryl refers to acryl or methacryl, to (meth) acrylic to acryloyl or methacryloyl, and (meth) acrylate to acrylate or methacrylate, respectively.

Acrylic resin (A) used for this invention has a (meth) acrylic-acid alkylester type monomer (a1) as a main component, and if necessary, copolymerizes the functional group containing monomer (a2) as a copolymerization component, and it is another A copolymerizable monomer (a3) can also be used as a copolymerization component. It is preferable that acrylic resin (A) in this invention using functional group monomer (a2) as a copolymerization component becomes a crosslinking point of acrylic resin (A), and improves adhesiveness with a base material and a to-be-adhered body further.

In addition, the copolymer which has a (meth) acrylic-acid alkylester type monomer (a1) as a main component is a copolymer containing the most (meth) acrylic-acid alkylester type monomer (a1), and (meth) acrylic acid with respect to all the copolymerization components. It is preferable to further contain 50 weight% or more, especially 55 weight% or more and 60 weight% or more of an alkyl ester monomer (a1).

As such a (meth) acrylic-acid alkylester type monomer (a1), it is more preferable that carbon number of an alkyl group is 1-20 normally, especially 1-12, 1-8, More specifically, methyl (meth) acrylate, Ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylic Late, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylic Aliphatic acrylic acid alkyl esters, such as a rate, cyclohexyl (meth) acrylate, and isobonyl (meth) acrylate, are mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Among such (meth) acrylic acid alkyl ester monomers (a1), n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are used for copolymerization properties, adhesive properties, ease of handling, and availability of raw materials. It is preferably used, and more preferably n-butyl (meth) acrylate is used in terms of excellent durability.

The content rate of the (meth) acrylic-acid alkylester type monomer (a1) in a copolymerization component becomes like this. Preferably it is 50-99.9 weight%, Especially preferably, 55-99.8 weight%, More preferably, it is 60-99.7 weight%. When there are too few (meth) acrylic-acid alkylester monomers (a1), for example, when used as an adhesive, there exists a tendency for adhesive force to run short.

Examples of the functional group-containing monomer (a2) include a hydroxyl group-containing monomer, an amino group-containing monomer, an acetacetyl group-containing monomer, an isocyanate group-containing monomer, a carboxyl group-containing monomer, a glycidyl group-containing monomer, and the like. In view of the crosslinking reaction, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferably used.

As a hydroxyl-containing monomer, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth), for example Caprolactone-modified monomers such as acrylate alkyl esters such as acrylate and 8-hydroxyoctyl (meth) acrylate, caprolactone-modified 2-hydroxyethyl (meth) acrylate, diethylene glycol (meth) acrylate, Oxyalkylene-modified monomers such as polyethylene glycol (meth) acrylate, other primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl 2-hydroxyethyl phthalic acid and N-methylol (meth) acrylamide; -Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy 3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate , 2-hydroxy3-phenoxypro Secondary hydroxyl group-containing monomers such as fill (meth) acrylate; tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth) acrylate.

As the hydroxyl group-containing monomer used in the present invention, the content of di (meth) acrylate as an impurity is preferably 0.5% or less, more preferably 0.2% or less, particularly 0.1% or less. Do. Specifically, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferable.

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutamic acid, itaconic acid, acrylamide-N-glycolic acid, cinnamic acid, and the like. Among these, (meth) acrylic acid is used preferably.

Examples of the amino group-containing monomers include t-butylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like. Among them, dimethylamino ethyl (meth) acrylate and diethylaminoethyl (meth) acrylate are preferably used.

As an acetacetyl group containing monomer, 2- (acetoxy) ethyl (meth) acrylate, an arylacetate acetate, etc. are mentioned, for example.

As an isocyanate group containing monomer, 2-acryloyl oxyethyl isocyanate, 2-methacryloyl oxyethyl isocyanate, these alkylene oxide addition products, etc. are mentioned, for example.

As a glycidyl group containing monomer, (meth) acrylic-acid glycidyl, (meth) acrylate allyl glycidyl, etc. are mentioned, for example. These functional group-containing monomers (a2) may be used alone or in combination of two or more, and in particular, a combination of a carboxyl group-containing monomer and an amino group-containing monomer, and a combination of a hydroxyl group-containing monomer and an amino group-containing monomer will cause a crosslinking reaction to accelerate. It is preferable at the point which is excellent in sheet formability.

The content ratio of the functional group-containing monomer (a2) in the copolymerization component of the acrylic resin (A) is preferably 0.1 to 30% by weight, particularly preferably 0.2 to 25% by weight, more preferably 0.3 to 20% by weight. When there are too few functional group containing monomers (a2), since the crosslinking point at the time of bridge | crosslinking becomes too small, there exists a tendency for the cohesion force after crosslinking to run short, and when too many, there exists a tendency for adhesive force to fall too much.

However, when using a hydroxyl group containing monomer as a functional group containing monomer (a2), it is preferable that it is 20 weight% or more as a content rate in the copolymerization component of acrylic resin (A) from the point which is excellent in moisture heat resistance and transparency. Preferably it is 20-50 weight%.

As another copolymerizable monomer (a3), for example, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, ethoxylated o-phenylphenyl (meth) acrylate, phenoxy Aromatic ring-containing monomers, such as a cd ethylene glycol (meth) acrylate, 2-hydroxy-3- phenoxy propyl (meth) acrylate, styrene, (alpha) -methylstyrene, (meth) acryloyl morpholine, and dimethyl (meth) Amide monomers such as acrylamide, diethyl (meth) acrylamide, and (meth) acrylamide, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and 3-methoxybutyl (Meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, Ethoxydiethylene glycol (meth) acrylate, Methoxydipropylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, octoxy polyethylene glycol polypropylene mono (meth) acrylate, lauxy polyethylene glycol mono (meth) acrylate, stearoxy polyethylene glycol Monomers containing alkoxy groups such as mono (meth) acrylates and oxy alkylene groups, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene Vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, aryl alcohol, acryl chloride, methyl vinyl ketone, N-acrylamide methyl trimethyl ammonium chloride, aryl trimethyl ammonium chloride, dimethyl aryl vinyl ketone, and the like. Can be mentioned.

The content ratio of the other copolymerizable monomer (a3) in the copolymerization component is preferably 0 to 40% by weight, particularly preferably 0 to 30% by weight, more preferably 0 to 25% by weight. When there are too many monomers (a3), there exists a tendency for adhesive characteristics to fall easily.

In this way, acrylic resin (A) is manufactured by superposing | polymerizing to the said (meth) acrylic-acid alkylester type monomer component (a1), Preferably a functional group containing monomer (a2) and a copolymerizable monomer (a3) as a copolymerization component as needed. Although it does so, it can carry out by conventionally well-known methods, such as solution radical polymerization, suspension polymerization, block polymerization, emulsion polymerization, in such polymerization. For example, in an organic solvent, monomer components, such as a (meth) acrylic-acid alkylester type monomer (a1), a functional group containing monomer (a2), and other copolymerizable monomer (a3), and a polymerization initiator are mixed or dripped, in a reflux state, or It polymerizes at 50-98 degreeC for 2 to 20 hours.

As an organic solvent used for such polymerization, aromatic hydrocarbons, such as toluene and xylene, esters, such as ethyl acetate and butyl acetate, aliphatic alcohols, such as n-propyl alcohol and isopropyl alcohol, acetone, methyl ethyl ketone, Ketones, such as methyl isobutyl ketone and cyclohexanone, etc. are mentioned.

As a polymerization initiator used for such a superposition | polymerization, azo type polymerization initiators, such as azobis isobutyronitrile and azobisdimethylvaleronitrile which are normal radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, di-t-butyl Peroxide type polymerization initiators, such as a peroxide and cumene hydroperoxide, etc. are mentioned as a specific example.

In this invention, it is necessary that the weight average molecular weights of acrylic resin (A) obtained above are 50,000-300,000 from the point that the viscosity of an acrylic resin solution becomes low and it performs easily the high solidification required in order to obtain the adhesive layer of a thick film | membrane. Preferably, it is 60,000-250,000, Especially preferably, it is 70,000-200,000, Especially preferably, it is 80,000-180,000. If the weight average molecular weight is too small, the cohesion force tends to be insufficient. If the weight average molecular weight is too large, the viscosity of the acrylic resin solution increases, so that it is difficult to obtain a clean coated surface.

About the number average molecular weight of acrylic resin (A), it is 3,000-150,000 normally, Preferably it is 5,000-130,000, Especially preferably, it is 8,000-100,000, Especially preferably, it is 10,000-80,000. If the number average molecular weight is too small, the cohesion force tends to be insufficient. If the number average molecular weight is too large, the viscosity of the acrylic resin solution increases, so that a clean coated surface becomes difficult to obtain.

Moreover, it is preferable that dispersion degree (weight average molecular weight / number average molecular weight) of acrylic resin (A) is 20 or less, Especially 10 or less are preferable, 7 or less are more preferable, and 4 or less are further more preferable. When such dispersion degree is too high, the durability of an adhesive layer will fall, and it exists in the tendency for foaming etc. to arise easily when an durability test is performed. In addition, the minimum of dispersion degree is 2 normally from the limit of manufacture.

Moreover, the glass transition temperature of acrylic resin (A) is -75--10 degreeC normally, Preferably it is -70--15 degreeC, More preferably, it is -60--20 degreeC, and when glass transition temperature is too high, it adheres There exists a tendency for a characteristic to be hard to be acquired, and when too low, there exists a tendency for adhesive force to fall.

In addition, said weight average molecular weight is a weight average molecular weight by conversion of a standard polystyrene molecular weight, and it is a column: Shodex to high performance liquid chromatography ("Waters 2695 (body)" and "Waters 2414 (detector)" by the Japan Waters company). GPC KF-806L (exclusion limit molecular weight: 2 × 10 ^7, separation range: 100 to 2 × 10 ⁷ , theoretical number of stages: 10,000 stages / piece, filler material: styrene-divinyl benzene copolymer, filler particle diameter: 10 μm) It is measured by using three series of and a number average molecular weight can also be measured by the same method. Moreover, dispersion degree can be calculated | required by a weight average molecular weight and a number average molecular weight. In addition, glass transition temperature (Tg) is computed by the following Fox formula.

Tg: glass transition temperature (K) of the copolymer

Tga: glass transition temperature (K) of homopolymer of monomer (A)

Wa: weight fraction of monomer (A)

Tgb: glass transition temperature (K) of homopolymer of monomer (B)

Wb: weight fraction of monomer (B)

Tgn: glass transition temperature (K) of homopolymer of monomer (N)

Wn: weight fraction of monomer (N)

(Wa + Wb +… + Wn = 1)

In addition, when the acrylic pressure-sensitive adhesive of the present invention is used for use in information labels used against electronic members, particularly precision electronic members, or for fixing electronic members, the acrylic resin (A) does not contain an acidic group because corrosion resistance is required. It is preferable that it is not.

As for the organic solvent (B) used by this invention, it is necessary for the chain transfer constant of the vinyl acetate to the organic solvent at 60 degreeC to be 250 or more.

In the present invention, the chain transfer constant C in the present invention is when the vinyl acetate monomer is polymerized at 60 ° C., where the reaction rate constants of the vinyl acetate growth terminal radicals to vinyl acetate and the organic solvent are kp and ktr, respectively. , Is calculated by the following formula.

As said chain transfer constant, Preferably it is 300 or more, Especially preferably, it is 400 or more, More preferably, it is 500 or more, and an upper limit is 10000 normally. When such a chain transfer constant is too small, the molecular weight of an acrylic resin will increase and it will become difficult to coat a thick film | membrane.

As the organic solvent (B), as long as the chain transfer constant of the organic solvent (B) is 250 or more, the organic solvent may be used alone, or two or more kinds of organic solvents may be used in combination. Here, in the case where the organic solvent (B) contains two or more kinds of organic solvents, the chain transfer constant of the organic solvent (B) is expressed by the average chain transfer constant.

The average chain transfer constant when using two or more organic solvents is

When using n kinds of organic solvents (X1, X2 ... Xn),

The chain transfer constant of each organic solvent is A1, A2... An,

The content ratio (weight%) of each organic solvent was determined by B1, B2... Bn

If it is, it is calculated by the following formula.

Usually, as a chain transfer constant of the main organic solvent generally mix | blended with an acrylic adhesive, they are methyl ethyl ketone 738, toluene (208.9), acetone (117), and ethyl acetate (33), for example.

In addition, the numerical value in () is a value based on J. brandrup, E.H.Immergut edition "PolymerHandbook", p.II-91, Interscience (1965).

In this invention, since the molecular weight of acrylic resin (A) is easily adjusted, it is preferable that 50 weight% or more of the organic solvent (B) is methyl ethyl ketone, Especially preferably, it is 60 weight% or more, More preferably, At least 70% by weight is methyl ethyl ketone.

As a solvent combined with such methyl ethyl ketone, Preferably, toluene, acetone, ethyl acetate, etc. are mentioned, Especially since it is easy to obtain a favorable coating surface, Toluene is especially preferable.

Although the said organic solvent (B) may be mix | blended with the acrylic resin (A) previously prepared, and may be used as a polymerization solvent at the time of superposing | polymerizing the copolymerization component which comprises acrylic resin (A), solid content concentration suitable especially for thick coating coatings. It is preferable to use it as a superposition | polymerization solvent at the time of superposition | polymerization from the point of acquiring easily acrylic resin solution of the point, or industrial productivity.

As content of the organic solvent (B), it is preferable that it is 70 weight part or less with respect to 100 weight part of acrylic resin (A), Especially preferably, it is 40 weight part or less, More preferably, it is 30 weight part or less. As a lower limit of such content, it is 10 weight part normally. When there is too much content of an organic solvent (B), there exists a tendency for thick coating coating to become difficult.

In this way, although the acrylic resin solution containing the acrylic resin (A) and the organic solvent (B) of this invention is obtained, in this invention, it is mentioned later that such an acrylic resin solution has solid content concentration of a specific range. When coating to a base material as an acrylic adhesive composition which mix | blended the crosslinking agent (C), it becomes an essential requirement at the time of enabling coating by a thick coating.

The acrylic resin solution of the present invention needs to have a solid content of at least 60% by weight, preferably at least 65% by weight, particularly preferably at least 70% by weight, more preferably at least 75% by weight, and such a solid content concentration. As an upper limit of, it is 90 weight% normally. When such solid content concentration is too low, it becomes difficult to obtain a thick coating and it is difficult to obtain an adhesive layer of a thick film.

Here, the solid content concentration (% by weight) of the acrylic resin solution can be calculated by, for example, quantitatively weighing 1 g of the sample in an aluminum foil, and remaining the resultant after heating for 45 minutes with a ket (infrared dryer, 185 W, height 5 cm). have.

In this invention, in acrylic resin solution, it is preferable that 60 weight% or more is acrylic resin (A) with respect to total solid content from the point which can ensure cohesion force, Especially preferably, it is 70 weight% or more, More preferably, 80 The wt% or more is acrylic resin (A). Usually, as an upper limit of the content rate of acrylic resin (A) with respect to all solid content, it is 100 weight%.

Moreover, it is preferable from the point of coatability that the acrylic resin solution of this invention is 20,000 mPa * s / 25 degrees C or less, Especially preferably, it is 18,000 mPa * s / 25 degrees C or less, More preferably, it is 15,000 mPa * s / It is 25 degrees C or less. Usually, as a lower limit of such a viscosity, it is 100 mPa * s / 25 degreeC.

If such viscosity is too high, coating tends to be difficult due to the tendency of the coating roots to come out.

In this invention, it is preferable to mix | blend a crosslinking agent (C) again with the said acrylic resin solution, and to make it an acrylic adhesive composition. After making it an acrylic adhesive composition, such an acrylic adhesive composition is bridge | crosslinked by a crosslinking agent (C). It becomes an acrylic adhesive.

Such a crosslinking agent (C) reacts mainly with the functional group derived from the functional group containing monomer (a2) which is a structural monomer of acrylic resin (A), and exhibits the outstanding adhesive force, For example, an isocyanate type crosslinking agent and an epoxy type crosslinking agent , An adidine crosslinking agent, a melamine crosslinking agent, an aldehyde crosslinking agent, an amine crosslinking agent, and a metal chelate crosslinking agent. Among these, an isocyanate type crosslinking agent is used suitably from the point of improving adhesiveness with a base material, or the point of reactivity with acrylic resin (A).

As said isocyanate type crosslinking agent, 2, 4- tolylene diisocyanate, 2, 6- tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1, 3- xylene diisocyanate, 1, 4- xylene diisocyanate, hexamethylene di, for example Isocyanate, diphenyl methane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanathmethyl) cyclohexane, tetramethylxylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane tri The adduct of an isocyanate, these polyisocyanate compounds, and polyol compounds, such as a trimetholpropane, the biuret, the isocyanurate, etc. of these polyisocyanate compounds are mentioned, Among these, tolylene diisocyanate and hexamethylene diisocyanate Adduct, biuret, isocyanurate body with polyol compound of It is preferably used, trimethylolpropane of 2,4-tolylene diisocyanate is added 2,6-tolylene diisocyanate adduct, or mixtures of water and trimethylolpropane are especially preferably used.

As said epoxy-type crosslinking agent, N, N, N ', N'- tetraglycidyl-m-xylenediamine, diglycidyl aniline, 1, 3-bis (N, N-glycidyl) Aminomethyl) cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether , Polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylpropane Polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl tris (2-hydroxyethyl) isocyanurate, resorcin glycidyl ether, bisphenol-S- In addition to diglycidyl ether, intramolecular And the like can be mentioned epoxy resins having two or more epoxy groups.

Examples of the adidine-based crosslinking agent include tetramethylolmethane-tri-β-adiridinylpropionate, trimetholpropane-tri-β-adiridinylpropionate, N, and N'-diphenyl. Methane-4,4'-bis (1-adilidinecarboxyamide), N, N'-hexamethylene-1,6-bis (1-adilidinecarboxyamide), and the like.

As said melamine type crosslinking agent, hexamethoxy methyl melamine, hexaethoxy methyl melamine, hexapropoxy methyl melamine, hexabutoxy methyl melamine, hexapentyloxy methyl melamine, hexahexyloxy methyl melamine, a melamine resin etc. are mentioned, for example. Can be mentioned.

Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succinic aldehyde, maleindialdehyde, glutaldialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

Examples of the amine crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, polyamide, and the like. .

Examples of the metal chelate crosslinking agent include acetylacetone and acetacetyl ester coordination compounds of polymetals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium. Can be.

In addition, these crosslinking agents (C) may be used independently or may use 2 or more types together.

It is preferable that content of the said crosslinking agent (C) is 0.01-20 weight part normally with respect to 100 weight part of acrylic resin (A), Preferably it is 0.05-15 weight part, More preferably, it is 0.1-10 weight part to be. When there is too little crosslinking agent (C), there exists a tendency for cohesion force lacking and sufficient durability cannot be obtained, and when too much, there exists a tendency for flexibility and adhesive force to fall easily.

Moreover, it is also preferable to use a crosslinking promoter (crosslinking catalyst) with a crosslinking agent (C) from the point which is excellent in the sheet formability at the time of thick coating. As such a crosslinking promoter (crosslinking catalyst), tertiary amines, such as benzylmethylamine and triethylenediamine, imidazole compounds, such as 2-methylimidazole and 2-ethyl-4-methylimidazole, paratoluenesulfonic acid And acid catalysts such as phosphoric acid, tin and zinc metal oxides, and the like.

Moreover, a silane coupling agent, an antistatic agent, another acrylic adhesive, another adhesive, a urethane resin, rosin, rosin ester, hydrogenated rosin ester, a phenol resin, in an acrylic adhesive composition in the range which does not impair the effect of this invention again, Conventionally known additives such as tackifiers such as aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, colorants, fillers, anti-aging agents, ultraviolet absorbers, functional dyes, ultraviolet rays or Although the compound which causes coloring or discoloration by irradiation can be mix | blended, It is preferable that the compounding quantity of these additives is 30 weight% or less of the whole composition, Especially preferably, it is 20 weight% or less, The molecular weight is 10,000 steps as a compounding agent. It is preferable to include no low molecular weight components at all in terms of durability.

In addition to the above additives, a small amount of impurities or the like contained in the raw material for manufacturing the constituent components of the pressure-sensitive adhesive composition may be contained.

The said acrylic adhesive composition can harden | cure (crosslink) with a crosslinking agent (C), and an acrylic adhesive can be obtained.

It is preferable to use the acrylic adhesive of this invention for the adhesive sheet containing the adhesive layer which consists of acrylic adhesives, and a base material.

Such an adhesive sheet can be manufactured according to the manufacturing method of a well-known general adhesive sheet, For example, after providing an acrylic adhesive composition on a base material, it can obtain by drying and curing.

There is no restriction | limiting in particular as a base material which provides the said acrylic adhesive composition, For example, Polyester-based resins, such as a polyethylene naphate, a polyethylene terephthalate, a polybutylene terephthalate, a polyethylene terephthalate / isophthalate copolymer; polyethylene, Polyolefin-based resins such as polypropylene and polymethylpentene; polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride and polyfluoride; polyamides such as nylon 6 and nylon 6,6; polyvinyl chloride, Vinyl aggregates such as polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, vinylon, etc .; cellulose resins such as 3 cellulose acetate and vertical plates; polymethacrylic acid Acrylic water, such as methyl, polymethacrylate, ethyl polyacrylate, and butyl polyacrylate G; Polystyrene; Polycarbonate; Polyarylate; Synthetic resin sheet such as polyimide, Paper made of aluminum, copper, iron metal foil, good quality paper, glassine paper, glass fiber, natural fiber, synthetic fiber, etc. And nonwoven fabrics. These base materials can be used as a monolayer or as a multilayer in which two or more kinds are laminated.

Moreover, in this invention, it is preferable to use the said acrylic adhesive as an adhesive for optical members, and the optical member with an adhesive layer can be obtained by laminating and forming the adhesive layer which consists of such acrylic adhesives on an optical member.

As such an optical member, transparent electrode films, such as an ITO electrode film, a polarizing plate, a retardation plate, an elliptical polarizing plate, an optical compensation film, a brightness improving film, an electromagnetic shield film, a near-infrared absorption film, an AR film, etc. are mentioned. Among these, when it is a transparent electrode film, it is preferable at the point which can exhibit the effect of this invention remarkably, and can obtain a high adhesive force, Especially preferably, it is an ITO (indium tin oxide) electrode film.

Here, especially when acrylic resin (A) does not contain an acidic group, since corrosion hardly arises, it is preferable.

In the said optical member with an adhesive layer, it is preferable to provide a release sheet again on the surface opposite to the optical member surface of an adhesive layer, and in practical use, after peeling the said release sheet together, an adhesive layer and an adherend are bonded together. do. As such a release sheet, it is preferable to use a silicone type release sheet.

When manufacturing the optical member with an adhesive layer in which the said release sheet was bonded, about the method of crosslinking an acrylic adhesive composition, [1] apply | coat an acrylic adhesive composition on an optical member, and after drying, the adhesive sheet is bonded and aged. It can be performed by the method of performing a process, [2] after apply | coating an acrylic adhesive composition on a mold release sheet, and drying, and then bonding an optical member together and performing an aging process. Among these, the method [2] is preferable from the point of not damaging an optical member, or of workability and stable manufacture.

Moreover, when using a crosslinking agent (C) for an acrylic adhesive composition, it is preferable to apply an aging process after manufacturing the optical member with an adhesive layer using the said method. Such aging treatment is carried out in order to balance the adhesion properties, and as conditions for aging, the temperature is usually from room temperature to 70 ° C, and the time is usually from 1 day to 30 days, specifically, at 23 ° C, for example. 1 day to 20 days, Preferably, it is good to carry out on conditions, such as 3 to 10 days at 23 degreeC, and 1 to 7 days at 40 degreeC.

At the time of application | coating (coating) of the said acrylic adhesive composition, it is performed by conventional methods, such as roll coating, die coating, gravure coating, comma coating, and screen printing.

Heretofore, the method of using the pressure-sensitive adhesive for bonding the pressure-sensitive adhesive layer and the adherend (other optical members) after the release of the above-mentioned release sheet after manufacturing the optical member with pressure-sensitive adhesive layer bonded to the release sheet was described. In this invention, it is also preferable to produce a double-sided adhesive sheet using the said acrylic adhesive, You may use the method of bonding optical members together using such a double-sided adhesive sheet.

As such a double-sided adhesive sheet, although it is good to apply the double-sided adhesive sheet of a well-known general structure using the said acrylic adhesive, it is especially made into the double-sided adhesive sheet without description from the point which is excellent in transparency and high adhesive force with respect to the thickness which comprises. desirable. Such a double-sided adhesive sheet without a base material is obtained by bonding another mold release sheet again to the side which does not have a release sheet of the said adhesive layer, after forming the adhesive layer which consists of the said acrylic adhesive on a release sheet. What is necessary is just to peel one release sheet, and to stick to a to-be-adhered body, after peeling off another release sheet.

The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer of the optical member with pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet is preferably 30 to 98%, particularly 40 to 95 in terms of durability and adhesive strength. % Is preferred, and even more preferably 50 to 90%. If the gel fraction is too low, the durability due to lack of cohesion tends to be insufficient. Moreover, when a gel fraction is too high, there exists a tendency for adhesive force to fall by raise of cohesion force.

In addition, when adjusting the gel fraction of the adhesive layer of an adhesive sheet, the adhesive for optical members, and the adhesive layer of a double-sided adhesive sheet to the said range, it is achieved by adjusting the kind and quantity of a crosslinking agent, etc., for example.

The said gel fraction becomes a standard of a degree of crosslinking (hardening degree), and is computed by the following method, for example. That is, an adhesive sheet (without separators) formed by forming a pressure-sensitive adhesive layer on a polymer sheet (for example, polyethylene terephthalate film, etc.) serving as a base material is wrapped with a 200 mesh SUS wire mesh, and then subjected to 23 ° C. in toluene. The weight percentage of the insoluble pressure-sensitive adhesive component remaining in the wire mesh for 24 hours to the pressure-sensitive adhesive layer before toluene dipping is taken as the gel fraction. However, the weight of the base material is omitted.

It is preferable that the thickness (film thickness after drying) of the adhesive layer in the said adhesive sheet, the optical member with an adhesive layer, and a double-sided adhesive sheet is 3-200 micrometers normally, It is especially preferable that it is 5-150 micrometers, 10 It is even more preferable that it is -100 micrometers. When the thickness of such an adhesive layer is too thin, there exists a tendency for adhesive physical property to become difficult to stabilize, and when too thick, the thickness of the whole optical member will tend to increase too much.

In the acrylic pressure-sensitive adhesive composition of the present invention, as described above, since the solid content concentration of the acrylic resin solution contained in the composition is high and low in viscosity, it is usually diluted with a solvent for low viscosity, which is generally used. In the acrylic adhesive composition with low solid content concentration, it becomes possible to obtain the adhesive layer of the thick film which could not be obtained by coating and drying.

When obtaining the adhesive layer of the said thick film | membrane, it is preferable to coat with a film thickness of 80 micrometers or more, Especially preferably, it is 110 micrometers or more, More preferably, it is 140 micrometers or more, In the film thickness of the adhesive layer obtained after drying, it is 50 It is preferable that it is micrometer or more, Especially preferably, it is 80 micrometers or more, More preferably, it is 100 micrometers or more. As an upper limit of such a film thickness, it is 3000 micrometers normally in the film thickness at the time of coating, and 2000 micrometers normally in the film thickness after drying. Moreover, especially when using it for the purpose of apply | coating a space | gap, such as shock absorption and an air layer, it is preferable that the film thickness of the adhesive layer after drying is 100 micrometers or more, Especially preferably, it is 120 micrometers or more, and an upper limit is 2000 micrometers normally.

Although the adhesive force of the adhesive layer of this invention is suitably determined according to the material of a to-be-adhered body, For example, when sticking to a PET sheet which deposited the glass substrate, the polycarbonate plate, the polymethyl methacrylate plate, and an ITO layer, It is preferable to have adhesive force of 5N / 25mm-500N / 25mm, and 10N / 25mm-100N / 25mm are more preferable.

In addition, the said adhesive force (N / 25mm) is computed as follows. On the 100-micrometer-thick polyethylene terephthalate (PET) sheet | seat, the adhesive layer PET sheet in which the adhesive layer was formed so that the thickness after drying might be 25 micrometers is cut | disconnected in width 25mm width. Subsequently, the release sheet was peeled off, and the pressure-sensitive adhesive layer side of the PET sheet with pressure-sensitive adhesive layer having a thickness of 25 mm × 100 mm was press-bonded with 2 kg rubber roller 2 reciprocating in a soda glass or the like at 23 ° C. and a relative humidity of 50% under the same atmosphere. It is left for 30 minutes under. Then, the value obtained by measuring 180 degree peeling strength (N / 25mm) by peeling rate 300mm / min at normal temperature is made into adhesive force (N / 25mm).

It is preferable that the total light transmittance of the adhesive layer of this invention is 90% or more, Especially preferably, it is 92% or more. When such total light transmittance is too low, it exists in the tendency which it is difficult to use for a display use because of the low permeability. In addition, the upper limit of total light transmittance is 95% normally.

It is preferable that the haze value of the adhesive layer of this invention is 10% or less, Especially preferably, it is 2% or less. If the haze value is too high, the image tends to be unclear when used for display. In addition, the minimum of haze value is 0.00% normally.

Here, the said total light transmittance and haze value are the values measured using the haze mater based on JISK7361-1. For example, the total light transmittance of an adhesive layer can be measured using HAZE MATER NDH2000 (made by Nihon Denshoku Industries Co., Ltd.) based on JISK7361-1. Moreover, the diffusion transmittance of an adhesive layer can also be measured using HAZE MATER NDH2000 (made by Nihon Denshoku Kogyo Co., Ltd.) based on JISK7361-1 similarly. The haze value of an adhesive layer can be computed as haze value (%) = (diffusion transmittance / total light transmittance) x100 from the value of the obtained total light transmittance and the diffuse transmittance.

In addition, the measurement of a haze value and a total light transmittance in this invention is a value which stuck only to the adhesion layer to optical PET (total light transmittance = 91.6%, haze value = 0.7%) and measured.

The pressure-sensitive adhesive made of the pressure-sensitive adhesive composition of the present invention can be suitably used as a double-sided adhesive sheet, especially a double-sided adhesive sheet having no (substrate) base material, and particularly has high adhesive force, excellent heat resistance and impact resistance, and high light It is hard to generate haze with permeability, and optical sheets, such as glass, an ITO transparent electrode sheet, polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PmmA), a polarizing film, and a phase difference film It is useful for the optical member pasting uses, such as an optical compensation film and a brightness improving film. Moreover, it can use suitably about the touch panel which consists of these optical members.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, in an Example, "part" and "%" mean a basis of weight.

First, various acrylic resin solutions (hereinafter, may be described as "acrylic resin solution (I)") were prepared as follows. In addition, the measurement of the weight average molecular weight, number average molecular weight, and glass transition temperature of acrylic resin solution (I) was measured according to the method mentioned above.

In addition, solid content concentration of acrylic resin solution (I) takes 1-2 g of acrylic resin solutions to aluminum foil, heat-drys for 45 minutes with a ket (infrared dryer, 185 W, height 5 cm), and measures the weight change before and behind drying. Calculated by About the measurement of the viscosity of acrylic resin solution (I), it measured according to 4.5.3 rotary clay meter of JISK5400 (1990).

[Preparation of Acrylic Resin Solution (I)] (See Table 1.)

[Acrylic resin solution (I-1)]

28 parts of methyl ethyl ketone and 8 parts of toluene were put into a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 90 ° C, 95 parts of butyl acrylate (a1) and 2-hydroxyethyl acryl A mixture of 0.16 parts of azobisisobutyronitrile (AIBN)) as a polymerization initiator was added dropwise to 5 parts of rate (a2) over 2 hours. In the middle of superposition | polymerization, superposition | polymerization was carried out for 7 hours, adding the polymerization catalyst liquid which melt | dissolved A6N 0.06 part in 2 parts of ethyl acetate in order, acrylic resin solution (I-1) (solid content concentration 72.5%, viscosity 4,700 mPa * s / 25 degreeC), The weight average molecular weight 127,000, number average molecular weight 47,200, dispersion degree 2.69, and glass transition temperature -53.3 degreeC) were obtained.

[Acrylic resin solution (I-2)]

28 parts of methyl ethyl ketone and 8 parts of toluene were put into a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 90 ° C, 55 parts of butyl acrylate (a1) and methyl acrylate (a1) were added. A mixture in which 0.16 parts of azobisisobutyronitrile (AIBN)) was dissolved in 40 parts and 5 parts of 2-hydroxyethyl acrylate (a2) was added dropwise over 2 hours. During the polymerization, the polymerization catalyst solution in which 0.06 parts of AIBN was dissolved in 2 parts of ethyl acetate was sequentially added, followed by polymerization for 7 hours to obtain an acrylic resin solution (I-2) (solid content concentration of 72.5%, viscosity of 14,400 mPa · s / 25 ° C., weight). Average molecular weight 134,000, number average molecular weight 50, 200, dispersion degree 2.67, and glass transition temperature -31.5 ° C.

[Acrylic resin solution (I-3)]

30 parts of methyl ethyl ketone and 10 parts of toluene were put into a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 90 ° C, 88 parts of butyl acrylate (a1) and methyl acrylate (a1) were added. To 10 parts and 2 parts of 2-hydroxyethyl acrylate (a2) was added dropwise a mixture of 0.16 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator over 2 hours. In the middle of superposition | polymerization, it superposes | polymerizes for 7 hours, adding the polymerization catalyst liquid which melt | dissolved 0.06 parts of AIBN in 2 parts of ethyl acetate in order, and acrylic resin solution (I-3) (70% of solid content concentration, viscosity 8,000 mPa * s / 25 degreeC), weight Average molecular weight 235,000, number average molecular weight 78,900, dispersion degree 2.98, and glass transition temperature -49.3 ° C) were obtained.

[Acrylic resin solution (I-4)]

21 parts of methyl ethyl ketone and 19 parts of toluene are put into a reactor equipped with a thermometer, a stirrer, a dropping lot and a reflux condenser, and the temperature is increased while stirring. When the temperature reaches 90 ° C, 80 parts of butyl acrylate (a1) and methyl acrylate (a1) 10 parts of 2-hydroxyethyl acrylate (a2) was added dropwise over 2 hours to a mixture of 0.16 parts of azobisisobutyronitrile (AIBN) dissolved as a polymerization initiator. In the middle of polymerization, the polymerization catalyst solution in which 0.06 parts of AIBN was dissolved in 13 parts of ethyl acetate was sequentially added, followed by polymerization for 7 hours to give an acrylic resin solution (I-4) (solid content concentration of 65%, viscosity of 7,800 mPa · s / 25 ° C., weight). Average molecular weight 262,000, number average molecular weight 84,500, dispersion degree 3.12, and glass transition temperature -49.3 ° C).

[Acrylic resin solution (I-5)]

28 parts of methyl ethyl ketone and 8 parts of toluene were placed in a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 90 ° C, 54.8 parts of butyl acrylate (a1) and methyl acrylate (a1) were added. A mixture of 40 parts, 5 parts of 2-hydroxyethyl acrylate (a2), 0.2 parts of dimethylaminoethyl acrylate (a2) and 0.16 parts of azobisisobutyronitrile (AIBN)) as a polymerization initiator was dissolved for 2 hours. It was dripped over. In the middle of the polymerization, the polymerization catalyst solution in which AIBN0.06 parts were dissolved in 2 parts of ethyl acetate was sequentially added, followed by polymerization for 7 hours to obtain an acrylic resin solution (I-5) (solid content concentration of 72.5%, viscosity of 10,400 mPa · s / 25 ° C.) The weight average molecular weight 118,000, the number average molecular weight 43,700, dispersion degree 2.70, and glass transition temperature -31.5 degreeC) were obtained.

[Acrylic resin solution (I-6)]

30 parts of methyl ethyl ketone and 10 parts of toluene were put into a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 90 ° C, 60 parts of butyl acrylate (a1) and methyl acrylate (a1) were added. To 10 parts and 30 parts of 2-hydroxyethyl acrylate (a2) was added dropwise a mixture of 0.16 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator over 2 hours. In the middle of superposition | polymerization, it superposed | polymerized for 7 hours, adding the polymerization catalyst liquid which melt | dissolved 0.06 parts of AIBN in 2 parts of ethyl acetate in order, and acrylic resin solution (I-6) (70% of solid content concentration, viscosity 8,900 mPa * s / 25 degreeC), weight Average molecular weight 107,000, number average molecular weight 40,200, dispersion degree 2.66, and glass transition temperature -38.9 ° C.

[Acrylic resin solution (I-7)]

30 parts of methyl ethyl ketone and 10 parts of toluene were put into a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 90 ° C, 88 parts of butyl acrylate (a1) and methyl acrylate (a1) were added. To 10 parts and 2 parts of 4-hydroxybutyl acrylate (a2), a mixture of 0.16 parts of azobis isobutyronitrile (AIBN) dissolved as a polymerization initiator was added dropwise over 2 hours. In the middle of superposition | polymerization, it superposed | polymerized for 7 hours, adding the polymerization catalyst liquid which melt | dissolved 0.06 parts of AIBN in 2 parts of ethyl acetate in order, and acrylic resin solution (I-7) (70% of solid content concentration, viscosity 8,200 mPa * s / 25 degreeC), weight The average molecular weight 215,000, the number average molecular weight 76,800, dispersion degree 2.80, and glass transition temperature -50.6 degreeC) were obtained.

[Acrylic resin solution (I-8)]

60 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser. When the temperature was raised to 78 ° C. while stirring, the mixture was 90 parts of butyl acrylate (a1), 5 parts of vinyl acetate (a3), and 2-hydroxy. A mixture of 0.05 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator was added dropwise to 5 parts of ethyl acrylate (a2) over 2 hours. During the polymerization, the polymerization catalyst solution in which 0.05 parts of AIBN was dissolved in 6 parts of toluene was sequentially added, followed by polymerization for 7 hours, followed by dilution with 84 parts of toluene to obtain an acrylic resin solution (I-8) (solid content concentration of 40%, viscosity 7,500). mPa * s / 25 degreeC, the weight average molecular weight 752,000, the number average molecular weight 176,900, dispersion degree 4.25, and glass transition temperature -50.1 degreeC) were obtained.

[Acrylic resin solution (I-9)]

60 parts of ethyl acetate and 10 parts of methyl ethyl ketone were placed in a reactor equipped with a thermometer, a stirrer, a dropping lot, and a reflux condenser, and the temperature was increased while stirring. When the temperature reached 75 ° C, 55 parts of butyl acrylate (a1) and methyl acrylate (a1) were added. ) 40 parts and 5 parts of 2-hydroxyethyl acrylate (a2) were added dropwise over 2 hours to a mixture obtained by dissolving 0.06 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator. In the middle of the polymerization, the polymerization catalyst solution in which 0.06 parts of AIBN was dissolved in 10 parts of ethyl acetate was sequentially added, followed by polymerization for 7 hours, followed by dilution with 86 parts of toluene to give an acrylic resin solution (I-9) (solid content concentration of 37.5%, viscosity). 7,800 mPa * s / 25 degreeC, the weight average molecular weight 570,000, the number average molecular weight 122,100, dispersion degree 4.67, and glass transition temperature -31.5 degreeC) were obtained.

Table 1 shows the type and weight ratio of the organic solvent (B), the chain transfer constant, and the compounding amount (part) in the acrylic resin solutions (I-1) to (I-9).

However, each symbol is as follows about Table 1.

BA: Butyl acrylate

MA: Methyl acrylate

HEA ： 2-hydroxyethyl acrylate

4HBA: 4-hydroxybutyl acrylate

DMAEA: Dimethylaminoethyl acrylate

VAc ： Vinyl acetate

Tol: Toluene

AcOEt ： Ethyl acetate

MEK: Methyl ethyl ketone

[Cross-linking system (C)]

The following were prepared as crosslinking agent (C-1).

55% ethyl acetate solution of tolylene diisocyanate adduct of trimetholpropane (manufactured by Nippon Polyurethane Co., Ltd., "Colonate L-55E")

[Examples 1-7, Comparative Examples 1, 2]

The acrylic adhesive composition was prepared by mix | blending a crosslinking agent (C) with the ratio shown in following Table 2 to the acrylic resin solution (I) prepared and prepared as mentioned above.

And the acrylic adhesive composition obtained above was apply | coated to polyester mold release sheet with thickness of 250 micrometers, it dried at 90-100 degreeC for 3 minutes, and the film thickness after drying formed the adhesive layer of 175 micrometers. Thereafter, the formed pressure-sensitive adhesive layer side was pasted with a polyester-based release sheet, and aged under conditions of 40 ° C for 10 days to obtain a double-sided pressure-sensitive adhesive sheet without a substrate.

Using the double-sided adhesive sheet without a base material obtained above, the adhesive layer request PET film was produced as follows, and it measured and evaluated in accordance with each method shown below a gel fraction, adhesive force, holding force, and corrosion resistance.

These results are shown together in Table 2 below.

[Production of PET film with adhesive layer]

The release sheet of one side was peeled from the adhesive of the double-sided adhesive sheet which is not described above, and it was pressed by the PET film with a film thickness of 100 micrometers, and the adhesive layer PET film was obtained.

[Gel fraction]

After cutting the said PET film with an adhesive layer to 40x40 mm, peeling a release sheet and pasting the adhesive layer side to the 50 * 100mm SUS mesh sheet (200 mesh), and centering the longitudinal direction of the SUS mesh sheet The gel fraction (%) was measured by the weight change of the adhesive layer before and after toluene immersion when it immersed in the sealed container which contained 250 g of toluene after wrapping a sample by folding in.

[adhesiveness]

The PET film with pressure-sensitive adhesive layer was cut into a width of 25 mm x length of 100 mm, and the release sheet was peeled off. The pressure-sensitive adhesive layer side was placed on a polycarbonate (PC) film or soda glass at 23 ° C. and a 50% relative humidity, 2 kg rubber. After pressure bonding by roller 2 reciprocation, and leaving it to stand for 30 minutes under the same atmosphere, 180 degree peeling strength (N / 25mm) was measured at the peeling speed of 300 mm / min at normal temperature.

[retention]

The PET film with pressure-sensitive adhesive layer was cut to 25 mm × 25 mm, the release sheet was peeled off, the pressure-sensitive adhesive layer side was stuck to the abrasive SUS plate, and subjected to a load of 1 kg under the conditions of 80 ° C., according to the measuring method of JISZ0237. The deviation was evaluated.

The evaluation criteria are as follows.

(evaluation)

○ ··· Do not cause deviation after 1440 minutes

△ ··· Takes off after 1440 minutes

Descends until 1440 minutes pass

〔Exterior〕

The acrylic pressure-sensitive adhesive composition obtained above is applied to a polyester-based release sheet at a thickness of 250 μm, dried at 90 to 100 ° C. for 3 minutes, and a pressure-sensitive adhesive layer having a thickness of 175 μm is formed to form an adhesive layer. Observed.

(evaluation)

No bubbles appear in the coating film.

(Triangle | delta) ... Although the bubble generate | occur | produces only in a coating film on the said conditions, if it dries again at 100 degreeC for 2 minutes, a bubble will disappear.

Bubbles generate on the coating film. Prolonging the drying time does not eliminate bubbles.

[Corrosion Resistance Evaluation Method]

The pressure-sensitive adhesive layer PET film was cut to 5 mm x 12 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer side was pasted onto the copper plate, and then stored for 7 days under an atmosphere of 60 ° C and a relative humidity of 90%. Then, the surface of the copper plate was visually observed from the PET film side, and the presence or absence of corrosion of the copper plate surface was confirmed. The evaluation criteria are as follows.

(evaluation)

○ ... corrosion is not recognized.

Corrosion is recognized

Using the double-sided adhesive sheet without a base material obtained above, the optical PET film with an adhesive layer was produced as follows, and the total light transmittance and haze value were measured and evaluated in accordance with each method shown below. These results are shown together in Table 2 below.

[Production of optical PET film with adhesive layer]

The above-mentioned double-sided adhesive sheet is cut to 3 cm x 4 cm, the release sheet on one side is peeled off, the pressure-sensitive adhesive layer side is pressed on the optical PET film, and the other release sheet is peeled off again to measure the total light transmittance and the haze value. A sample was obtained.

[Total light transmittance] and [haze value]

The release sheet of the optical PET film with the pressure-sensitive adhesive layer was peeled off, and the diffusion transmittance and the total light transmittance were measured using HAZE MATER NDH2000 (manufactured by Nihon Denshoku Kogyo Co., Ltd.). In addition, this apparatus is based on JISK7361-1. In addition, the haze value was computed by substituting the value of the obtained diffuse transmittance and total light transmittance into the following formula.

Haze value (%) = (diffusion transmittance / total light transmittance) × 100

In addition, the value when the said total light transmittance and haze value were measured only for an optical PET film is total light transmittance = 91.6%, haze value = 0.7%.

However, the numerical value in () of Table 2 is a compounding weight part. In addition, "*" of Table 2 shows that the adhesive layer formed on the optical PET film could not be tested because it contains many bubbles.

Although the adhesive layer obtained by hardening | curing the acrylic adhesive composition of Examples 1-7 is a thick film adhesive layer obtained by coating thicker than usual, all the favorable drawings can be obtained, and total light transmittance, a haze value, etc. are obtained. It has excellent optical properties and excellent adhesion properties.

On the other hand, in Comparative Examples 1 and 2, since the weight average molecular weight of the acrylic resin contained in the acrylic resin solution is high and the viscosity is high, it must be diluted with an organic solvent to a viscosity that can be coated, and the acrylic resin solution has a low solid content concentration. It is becoming. For this reason, even if it coats thickly like Examples 1-7, when the organic solvent is not blown off at the time of drying, many bubbles generate | occur | produce in the figure of the produced adhesive layer, and are inferior to optical physical property.

Although this invention was detailed also demonstrated with reference to the specific embodiment, it is clear for those skilled in the art that various changes and correction can be added without deviating from the mind and range of this invention. This application is based on the JP Patent application (patent application 2010-102410) of an application on April 27, 2010, The content is taken in here as a reference.

(Industrial availability)

The pressure-sensitive adhesive made of the pressure-sensitive adhesive composition of the present invention can be suitably used as a double-sided adhesive sheet, especially a double-sided adhesive sheet having no (substrate) base material, and particularly, has high adhesive strength, excellent heat resistance and impact resistance, and high light. Glass, ITO transparent electrode sheet, polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA) because it has permeability and is difficult to generate haze and does not cause corrosion to metals or metal oxides. It is useful for optical member pasting uses, such as optical sheets, a polarizing film, a phase difference film, an optical compensation film, and a brightness improving film.

Moreover, it can use suitably about the touch panel which consists of these optical members.

Claims (12)

It contains a weight average molecular weight 50,000-300,000 acrylic resin (A), and the organic solvent (B) whose chain transfer constant to the organic solvent of vinyl acetate at 60 degreeC becomes 250 or more, and solid content concentration is 60% or more Acrylic resin solution, characterized in that. The method according to claim 1,
The viscosity of an acrylic resin solution is 20,000 mPa * s / 25 degreeC or less, The acrylic resin solution characterized by the above-mentioned. The method according to claim 1 or 2,
Acrylic resin (A) does not contain an acidic group, Acrylic resin solution characterized by the above-mentioned. 4. The method according to any one of claims 1 to 3,
50 weight% or more of the organic solvent (B) is methyl ethyl ketone, The acrylic resin solution characterized by the above-mentioned. 5. The method according to any one of claims 1 to 4,
60 weight% or more is acrylic resin (A) with respect to the total solid in an acrylic resin solution, The acrylic resin solution characterized by the above-mentioned. The acrylic adhesive composition containing the acrylic resin solution of any one of Claims 1-5. The method of claim 6,
A crosslinking agent (C) is contained, The acrylic adhesive composition characterized by the above-mentioned. The acrylic adhesive composition of Claim 6 or 7 is bridge | crosslinked, The acrylic adhesive characterized by the above-mentioned. The adhesive layer containing the acrylic adhesive of Claim 8 is contained, The adhesive sheet characterized by the above-mentioned. It is an adhesive sheet which has an adhesive layer obtained by coating and drying the acrylic adhesive composition of Claim 6 or 7 with a film thickness of 80 micrometers or more on a base material, and the film thickness of the adhesive layer after drying is 50 micrometers or more, The adhesive sheet characterized by the above-mentioned. . The acrylic adhesive for optical members formed using the acrylic adhesive of Claim 8. The optical member with an adhesive layer containing the adhesive layer containing the acrylic adhesive of Claim 8, and an optical member.