JP6850175B2 - Adhesive compositions, adhesives, adhesive sheets, and optics - Google Patents

Description

The present invention relates to pressure-sensitive adhesive compositions, pressure-sensitive adhesives, pressure-sensitive adhesive sheets, and optical members.

Conventionally, many studies have been conducted to improve the performance of adhesives. For example, in Patent Document 1, a polymer for adding an adhesive, which has excellent compatibility with various polymers, does not show white turbidity or segregation phenomenon when added to various polymers, and has an excellent modifying effect. The modifier is disclosed. However, the present inventor has found that there is room for great improvement in conventional pressure-sensitive adhesive compositions, especially when forming a thin pressure-sensitive adhesive layer.

Japanese Patent No. 4442923

An object of the present invention is to provide an adhesive composition exhibiting excellent constant load peeling resistance, particularly when forming a thin adhesive layer. It is also an object of the present invention to provide a pressure-sensitive adhesive formed from such a pressure-sensitive adhesive composition. Furthermore, it is also an object of the present invention to provide a pressure-sensitive adhesive sheet and an optical member provided with a pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive composition.

The present inventor has made diligent studies to solve the above problems. As a result, the present inventor uses a (meth) acrylic triblock polymer having a relatively low molecular weight, so that the triblock polymer is unevenly distributed on the surface of the adhesive layer, and particularly excellent constant load peeling resistance can be obtained. I found that.

Aspects of the present invention are, for example, as follows.
[1] Adhesion containing a (meth) acrylic random polymer and a (meth) acrylic triblock polymer having a weight average molecular weight (Mw) of 3,000 to 30,000 as measured by a gel permeation chromatography method. Agent composition.
[2] The pressure-sensitive adhesive composition according to [1], wherein the blending amount of the (meth) acrylic triblock polymer is in the range of 1 to 49 parts by mass with respect to 100 parts by mass of the (meth) acrylic random polymer. ..
[3] The (meth) acrylic triblock polymer has a structure represented by [A]-[B]-[A] by blocks [A] and blocks [B], [1]. Alternatively, the pressure-sensitive adhesive composition according to [2].
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], which further contains an isocyanate-based cross-linking agent.
[5] The pressure-sensitive adhesive composition according to any one of [1] to [4] used for optical applications.
[6] A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition according to any one of [1] to [5].
[7] A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer formed on at least one surface of the base material by the pressure-sensitive adhesive composition according to any one of [1] to [6].
[8] The pressure-sensitive adhesive sheet according to [7], wherein the pressure-sensitive adhesive layer has a thickness of 15 μm or less.
[9] An optical member including an adhesive layer formed by the adhesive composition according to any one of [1] to [5].
[10] The optical member according to [9], wherein the thickness of the adhesive layer is 15 μm or less.

According to the present invention, it is possible to provide an adhesive composition exhibiting excellent constant load peeling resistance, particularly when forming a thin adhesive layer. According to the present invention, it is also possible to provide a pressure-sensitive adhesive formed from such a pressure-sensitive adhesive composition. Further, according to the present invention, it is also possible to provide a pressure-sensitive adhesive sheet and an optical member having a pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive composition.

Hereinafter, the pressure-sensitive adhesive composition, the pressure-sensitive adhesive, the pressure-sensitive adhesive sheet, and the optical member according to one aspect of the present invention will be described.

In addition, in this specification, "polymer" is used in the meaning which includes a homopolymer and a copolymer, and "polymerization" is used in the meaning which includes a homopolymer and a copolymer. Further, the compound represented by the formula (i) (i is a formula number) is also simply referred to as "compound (i)". Further, as used herein, (meth) acrylic means acrylic or methacrylic, (meth) acrylate means acrylate or methacrylate, and (meth) acrylo means acrylo or methacrylo.

[Adhesive composition]
The pressure-sensitive adhesive composition according to one aspect of the present invention contains a (meth) acrylic-based random polymer and a (meth) acrylic-based triblock polymer. Here, the (meth) acrylic triblock polymer has a weight average molecular weight (Mw) of 3,000 to 30,000 as measured by a gel permeation chromatography (GPC) method.

[1] (Meta) Acrylic Random Polymer The composition of the (meth) acrylic random polymer is not particularly limited. The (meth) acrylic random polymer may be synthesized by a normal radical polymerization method or may be synthesized by a living radical polymerization method. The weight average molecular weight (Mw) of the (meth) acrylic random polymer measured by the GPC method is, for example, 100,000 to 3,000,000, preferably 150,000 to 2,000,000, and more. It is preferably 200,000 to 2,000,000. The molecular weight distribution (Mw / Mn) of the (meth) acrylic random polymer measured by the GPC method is, for example, 30.0 or less, preferably 25.0 or less, and more preferably 20.0 or less.

<Raw material monomer>
As the raw material monomer of the (meth) acrylic random polymer, (meth) acrylic acid ester is mainly used, but other functional group-containing monomers, copolymerizable monomers and the like can also be further used.

《(Meta) acrylic acid ester》
Examples of the (meth) acrylic acid ester include alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, alkoxypolyalkylene glycol mono (meth) acrylate, alicyclic group or aromatic ring-containing (meth) acrylate. However, functional group-containing (meth) acrylates such as hydroxyl group-containing (meth) acrylate, carboxyl group-containing (meth) acrylate, and amino group-containing (meth) acrylate are excluded from the (meth) acrylic acid ester.

The number of carbon atoms of the alkyl group in the alkyl (meth) acrylate is preferably 1 to 20. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, and iso-butyl (iso-butyl). Meta) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, Examples thereof include decyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, oleyl (meth) acrylate, n-stearyl (meth) acrylate, iso-stearyl (meth) acrylate, and didecyl (meth) acrylate.

Examples of the alkoxyalkyl (meth) acrylate include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, and 3-ethoxypropyl (meth) acrylate. Examples thereof include meta) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, and ethoxydiethylene glycol mono (meth) acrylate. Examples thereof include methoxytriethylene glycol mono (meth) acrylate.

Examples of the alicyclic group or aromatic ring-containing (meth) acrylate include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate.

The total amount of the (meth) acrylic acid ester used is, for example, 70 to 99.9% by mass, preferably 80 to 99.5% by mass, and more preferably 89.95 to 98% with respect to the total mass of all the raw material monomers. It is 95% by mass.

The (meth) acrylic acid ester may be used alone or in combination of two or more.

<< Functional group-containing monomer >>
Examples of the functional group-containing monomer include a hydroxyl group-containing monomer, an acid group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, a nitrogen-based heterocyclic ring-containing monomer, and a cyano group-containing monomer. Examples of the acid group include a carboxyl group, an acid anhydride group, a phosphoric acid group, and a sulfate group.

Examples of the hydroxyl group-containing monomer include hydroxyl group-containing (meth) acrylates, and specifically, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroshikibutyl (meth) acrylate. , 6-Hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate and other hydroxyalkyl (meth) acrylates. The number of carbon atoms of the alkyl group in the hydroxyalkyl (meth) acrylate is usually 2 to 8, preferably 2 to 6.

Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, mono (meth) acryloyloxyethyl ester of succinate, and ω-carboxypolycaprolactone mono (meth) acrylate. , Acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid. Examples of the acid anhydride group-containing monomer include maleic anhydride. Examples of the phosphate group-containing monomer include a (meth) acrylic monomer having a phosphate group in the side chain, and examples of the sulfate group-containing monomer include a (meth) acrylic monomer having a sulfate group in the side chain.

Examples of the amino group-containing monomer include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and N-hexyl (meth) acrylamide. Examples of the nitrogen-based heterocyclic-containing monomer include vinylpyrrolidone, acryloylmorpholine, and vinylcaprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The total amount of the functional group-containing monomer used is preferably 0 to 10% by mass, more preferably 0.05 to 5% by mass, based on the total mass of all the raw material monomers.

The functional group-containing monomer may be used alone or in combination of two or more.

<< Copolymerizable Monomer >>
Examples of the copolymerizable monomer include alkyl styrene such as styrene, methyl styrene, dimethyl styrene, trimethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene and octyl styrene, fluorostyrene, chloro styrene, bromo styrene and dibromo. Examples thereof include styrene-based monomers such as styrene, styrene iodide, nitrostyrene, acetylstyrene and methoxystyrene, and vinyl acetate.

The copolymerizable monomer may be used alone or in combination of two or more.

[2] (Meta) Acrylic Triblock Polymer The (meth) acrylic triblock polymer used in the present invention has a weight average molecular weight (Mw) of 3,000 to 30,000 as measured by the GPC method. The weight average molecular weight (Mw) is preferably 3,000 to 20,000, more preferably 3,000 to 10,000. The molecular weight distribution (Mw / Mn) of the (meth) acrylic random polymer measured by the GPC method is, for example, 1.5 or less, preferably 1.4 or less, and more preferably 1.3 or less. is there.

As described above, by using the (meth) acrylic triblock polymer having a relatively low molecular weight, the present inventor causes uneven distribution of the triblock polymer on the surface of the adhesive layer, and obtains particularly excellent constant load peeling resistance. I found that it was possible. If the weight average molecular weight is too large, the triblock polymer is not significantly unevenly distributed on the surface of the adhesive layer, and it is difficult to achieve excellent constant load peeling resistance. On the other hand, if the weight average molecular weight is too small, the pressure-sensitive adhesive composition has insufficient cohesive force, and it is difficult to achieve excellent constant load peeling resistance.

The method for synthesizing the (meth) acrylic triblock polymer used in the present invention is not particularly limited. The (meth) acrylic triblock polymer may be synthesized by a normal radical polymerization method or may be synthesized by a living radical polymerization method.

The triblock polymer can be produced using common living radical polymerization. Of these, from the viewpoint of ease of control of the polymerization reaction, it can be suitably produced by atom transfer radical polymerization. The atom transfer radical polymerization method is a polymerization method using an organic halide or a sulfonyl halide compound as an initiator and a metal complex as a catalyst. When producing a triblock polymer by the living radical polymerization method, a method of sequentially adding monomer units, a method of polymerizing the next polymer block using a pre-synthesized polymer as a polymer initiator, or a method of polymerizing separately polymer blocks. Examples thereof include a method of binding by a reaction, but it is preferable to produce a triblock polymer by a method of sequentially adding monomer units.

The (meth) acrylic triblock polymer may be synthesized, for example, by reversible additional cleavage chain transfer (RAFT) polymerization. By using RAFT polymerization, the molecular weight and molecular weight distribution of the (meth) acrylic triblock polymer can be controlled more precisely.

The RAFT polymerization method is a method of polymerizing a radically polymerizable compound as a raw material monomer in the presence of a RAFT agent. The entire amount of the raw material monomer may be charged and polymerized at once, or a part of the raw material monomer may be polymerized and then the remaining monomer components may be added continuously or intermittently for polymerization.

<RAFT agent>
Conventionally known compounds can be used as the RAFT agent, and the agent is not particularly limited. Examples of the RAFT agent include thiocarbonylthio compounds such as bis (thiocarbonyl) disulfide, dithioester, trithiocarbonate, dithiocarbamate, and xantate.
Examples of bis (thiocarbonyl) disulfide compounds include tetraethylthiuram disulfide, tetramethylthiuram disulfide, bis (n-octyl mercapto-thiocarbonyl) disulfide, bis (n-dodecyl mercapto-thiocarbonyl) disulfide, and bis (benzyl mercapto-thiocarbonyl). ) Disulfide, bis (n-butyl mercapto-thiocarbonyl) disulfide, bis (t-butyl mercapto-thiocarbonyl) disulfide, bis (n-heptyl mercapto-thiocarbonyl) disulfide, bis (n-hexyl mercapto-thiocarbonyl) disulfide , Bis (n-pentyl mercapto-thiocarbonyl) disulfide, bis (n-nonyl mercapto-thiocarbonyl) disulfide, bis (n-decyl mercapto-thiocarbonyl) disulfide, bis (t-dodecyl mercapto-thiocarbonyl) disulfide, bis (N-Tetradecyl mercapto-thiocarbonyl) disulfide, bis (n-hexadecyl mercapto-thiocarbonyl) disulfide, bis (n-octadecyl mercapto-thiocarbonyl) disulfide, etc.;
Examples of the dithioester compound include 2-phenyl-2-propylbenzothioate, 4-cyano-4- (phenylthiocarbonylthio) pentanoic acid, 2-cyano-2-propylbenzodithioate and the like;
Examples of the trithiocarbonate compound include S- (2-cyano-2-propyl) -S-dodecyl trithiocarbonate, 4-cyano-4-[(dodecyl sulfanyl-thiocarbonyl) sulfanyl] pentanoic acid, and cyanomethyl dodecyltri. Thio-carbonate, 2- (dodecylthiocarbonothiolthio) -2-methylpropionic acid, bis [4- {ethyl-2- (hydroxyethyl) aminocarbonyl} -benzyl] trithiocarbonate, etc.;
As the dithiocarbamate compound, for example, cyanomethylmethyl (phenyl) carbamodithioate, cyanomethyldiphenylcarbamo-dithioate and the like;
Examples of the xanthate compound include xanthate esters and the like;

The amount of the RAFT agent used is usually 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the total amount of the raw material monomers. If the amount of the RAFT agent used is not less than the lower limit of the above range, the reaction control is easy, and if it is not more than the upper limit of the above range, the weight average molecular weight of the obtained polymer can be easily adjusted to the above range. ..

RAFT polymerization is preferably carried out in the presence of a polymerization initiator. Examples of the polymerization initiator include ordinary organic polymerization initiators, specifically, peroxides such as benzoyl peroxide and laurium peroxide, and azos such as 2,2'-assobisisobutyronitrile. Examples include compounds. The polymerization initiator may be used alone or in combination of two or more.

When the polymerization initiator is used, the amount used is usually 0.001 to 2 parts by mass, preferably 0.002 to 1 part by mass with respect to 100 parts by mass of the raw material monomer. The amount of the polymerization initiator used is usually 0.1 to 3000 mol, preferably 1 to 1000 mol, based on 1 mol of the RAFT agent.

<Raw material monomer>
As the raw material monomer constituting each block of the (meth) acrylic triblock polymer, (meth) acrylic acid ester is mainly used, but other functional group-containing monomers and copolymerizable monomers may be further used. it can. Examples of the (meth) acrylic acid ester, the functional group-containing monomer, and the copolymerizable monomer include those similar to those described above for the raw material monomer of the (meth) acrylic random polymer.

<Block configuration>
The (meth) acrylic triblock polymer used in the present invention preferably has a structure represented by [A]-[B]-[A] by the block [A] and the block [B]. .. When such a configuration is adopted, structural cohesive force is likely to be exhibited, and high cohesive force can be obtained even with a relatively low molecular weight, so that particularly excellent constant load peeling resistance can be obtained.

The weight of the block [A] is, for example, 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass of the entire (meth) acrylic triblock polymer. The weight of the block [B] is, for example, 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass of the entire (meth) acrylic triblock polymer.

The block [A] is _{formed from a monomer represented by the general formula CH 2} = CY ^1- COOY ² (Y ¹ is a hydrogen atom or a methyl group, and Y ² is an alkyl group having 1 to 20 carbon atoms). It is preferable that the component to be used is contained. Further, the block [B] is _{a monomer represented by the general formula CH 2} = CY ^3- COOY ⁴ (Y ³ is a hydrogen atom or a methyl group, and Y ⁴ is an alkyl group having 1 to 20 carbon atoms). It preferably contains a component formed from. In this case, it is more preferable that the carbon number of ^{Y 2} is larger than the carbon number of ^{Y 4.} When such a configuration is adopted, uneven distribution of the triblock polymer on the surface of the adhesive layer is more likely to occur, and particularly excellent constant load peeling resistance can be obtained.

^{Examples of the combination of Y 2} and Y ⁴ satisfying the above conditions include those shown in Table 1 below. The description in this table is merely an example and does not exclude combinations other than these.

The blending amount of the (meth) acrylic triblock polymer having a weight average molecular weight (Mw) of 3,000 to 30,000 measured by the GPC method is, for example, with respect to 100 parts by mass of the above (meth) acrylic random polymer. It is 1 to 49 parts by mass, preferably 1 to 39 parts by mass. By adjusting the blending amount of the (meth) acrylic triblock polymer within such a range, even better constant load peeling resistance can be obtained.

The pressure-sensitive adhesive composition according to the present invention may further contain a triblock polymer outside the molecular weight range, and may further contain a block polymer other than the triblock polymer.

[3] Other components As other components, the pressure-sensitive adhesive composition includes a cross-linking agent, a silane coupling agent, an antistatic agent, an organic solvent, an antioxidant, a light stabilizer, a metal corrosion inhibitor, a tackifier, and a plasticizer. It may further contain an agent, a cross-linking accelerator, nanoparticles and the like.

<Crosslinking agent>
Examples of the cross-linking agent include isocyanate-based compounds, epoxy-based compounds, and metal chelate-based compounds, which can exhibit good physical properties in the pressure-sensitive adhesive layer without hindering uneven distribution of the triblock polymer on the surface of the pressure-sensitive adhesive layer. In that respect, it is preferable to use an isocyanate-based cross-linking agent.

As the isocyanate compound, an isocyanate compound having two or more isocyanate groups in one molecule is usually used. Examples of the isocyanate compound include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl. Examples thereof include aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate, which have 7 to 30 carbon atoms. Diisocyanate can be mentioned. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylenediocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenyl propane diisocyanate.

Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples thereof include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanatebenzene, and 4,4', 4 ″ -triphenylmethane triisocyanate. Further, examples of the isocyanate compound include , Diphenylmethane diisocyanate trimerate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or tolylene diisocyanate biuret or isocyanurate, reaction product of trimethylol propane with tolylene diisocyanate or xylylene diisocyanate (eg, tolylene diisocyanate) Examples thereof include a three-molecule addition of isocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a three-molecule addition of hexamethylene diisocyanate), a polyether polyisocyanate, and a polyester polyisocyanate.

As the epoxy compound, for example, an epoxy compound having two or more epoxy groups in one molecule is usually used. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N, N, N', N' -Tetraglycidyl-m-xylylene diamine, N, N, N', N'-tetraglycidyl aminophenylmethane, triglycidyl isocyanurate, m-N, N-diglycidyl aminophenylglycidyl ether, N, N-diglycidyl Examples include truidin and N, N-diglycidyl aniline.

As the metal chelate compound, for example, alkoxide, acetylacetone, ethyl acetoacetate and the like are coordinated with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium. Examples include compounds. Specific examples thereof include aluminum isopropylate, aluminum secondary butyrate, aluminum ethyl acetoacetate / diisopropirate, aluminum tris ethyl acetoacetate, and aluminum tris acetyl acetonate.

The cross-linking agent is 0.01 to 5 parts by mass, preferably 0.01 to 2 parts by mass, more preferably 0.01 to 2 parts by mass, based on 100 parts by mass of the total of the (meth) acrylic random polymer and the (meth) acrylic triblock polymer. Is in the range of 0.01 to 1 part by mass. If a cross-linking agent is included in this range, durability and stress relaxation property can be balanced.

<Silane coupling agent>
The silane coupling agent firmly adheres the adhesive layer to an adherend such as a glass substrate, can prevent the adhesive layer from peeling off in a high humidity and heat environment, and when combined with the block polymer, has an effect of improving durability. large.

Examples of the silane coupling agent include polymerizable unsaturated group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-. Epoxy group-containing silane cups such as glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Ring agent; Amino group-containing silanes such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Coupling agent; Examples thereof include halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane.

Of these, an epoxy group-containing silane coupling agent is preferable in terms of stress relaxation and the like. In the composition of the present invention, the content of the silane coupling agent is usually 1 part by mass or less, preferably 1 part by mass or less, based on 100 parts by mass of the total of the (meth) acrylic random polymer and the (meth) acrylic triblock polymer. It is 0.01 to 1 part by mass, more preferably 0.05 to 0.5 part by mass. When the content is in the above range, peeling of the adhesive layer in a high humidity environment and bleeding of the silane coupling agent in a high temperature environment tend to be prevented.

<Antistatic agent>
Examples of the antistatic agent include a surfactant, an ionic compound, and a conductive polymer.

Examples of the surfactant include a cationic surfactant having a cationic group such as a quaternary ammonium salt, an amide quaternary ammonium salt, a pyridium salt, and a primary to tertiary amino group; a sulfonic acid base and a sulfate ester. Anionic surfactants having anionic groups such as bases and phosphate esters; amphoteric surfactants such as alkylbetaines, alkylimidazolinium betaines, alkylamine oxides, amino acid sulfate esters, glycerin fatty acid esters, etc. , Solbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, alkyldiethanolamides and other nonionic surfactants. Be done.

Further, as the surfactant, a reactive emulsifier having a polymerizable group can be mentioned, and a polymer-based surfactant having a high molecular weight of the above-mentioned surfactant or a monomer component containing the reactive emulsifier can also be used.

The ionic compound is composed of a cation part and an anion part, and may be in a solid state or a liquid state at room temperature (23 ° C./50% RH).

The cation portion constituting the ionic compound may be either an inorganic cation or an organic cation, or both. As the inorganic cation, alkali metal ion and alkaline earth metal ion are preferable, ^{and Li +} , Na ⁺ and K ⁺ having excellent antistatic properties are more preferable. Examples of the organic cation include pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, pyrazolium cation, and pyrazoli. Examples thereof include nium cations, tetraalkylammonium cations, trialkylsulfonium cations, tetraalkylphosphonium cations and derivatives thereof.

The anionic portion constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with the cation moiety. Specifically, F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , SCN ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (F ₂ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , TaF ₆ ⁻ , F (HF) _n ⁻ , (CN) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , C ₃ Examples include F ₇ ^{COO −} and (CF ₃ SO ₂ ) (CF ₃ CO) N ^−.

Examples of the ionic compound include lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) imide, potassium bis (difluorosulfonyl) imide, and 1 -Ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis (fluoro) Sulfonyl) imide, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide, (N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, N, N-diethyl- N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluorosphoniumimide, 1-octyl-3-methylpyridinium and trifluorosulfoniumimide are preferred.

Conductive polymers include, for example, polythiophene, polyaniline, polypyrrole and derivatives thereof.

In the composition of the present invention, the content of the antistatic agent is usually 3 parts by mass or less, preferably 0, based on 100 parts by mass in total of the (meth) acrylic random polymer and the (meth) acrylic triblock polymer. It is 0.01 to 3 parts by mass, more preferably 0.05 to 2.5 parts by mass.

<Organic solvent>
The pressure-sensitive adhesive composition according to the present invention does not necessarily have to contain a solvent, but may contain an organic solvent in order to adjust its coatability. In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent is usually 50 to 90% by mass, preferably 60 to 85% by mass. In the present specification, the "solid content" refers to all the components contained in the pressure-sensitive adhesive composition excluding the above-mentioned organic solvent, and the "solid content concentration" refers to 100% by mass of the pressure-sensitive adhesive composition. The ratio of the solid content.

There is no limitation on the use of the pressure-sensitive adhesive composition according to the present invention. However, the present inventor has found that the pressure-sensitive adhesive composition according to the present invention exhibits excellent performance particularly when forming a thin pressure-sensitive adhesive layer. Therefore, the pressure-sensitive adhesive composition according to the present invention is particularly useful in optical applications. Examples of optical applications include various display devices (liquid crystal display devices, organic EL display devices, electronic paper display devices, etc.), touch panels, cameras, microscopes, and the like.

[Adhesive]
The pressure-sensitive adhesive according to the present invention is formed by the pressure-sensitive adhesive composition described above. The gel fraction of this pressure-sensitive adhesive is not particularly limited, but is usually 80% by mass or less. The gel fraction is, for example, a value measured under the conditions described in Examples.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to the present invention is formed on both sides of a double-sided pressure-sensitive adhesive sheet, a base material, and a base material having only an adhesive layer formed on a peel-treated cover film (hereinafter, also referred to as a separator). A double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer (in this case, the base material is also referred to as a core material), a single-sided pressure-sensitive adhesive sheet having the base material and the pressure-sensitive adhesive layer formed on one surface of the base material, and their adhesion. Includes an adhesive sheet in which a peeled cover film is attached to a surface of the adhesive layer of the sheet that is not in contact with the base material.

Examples of the base material and cover film include polyester films such as polyethylene terephthalate (PET); polyolefin films such as polycarbonate, polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, polarizing plates, retardation films, light diffusion films, and brightness. Examples include plastic films such as improved films and glass. Further, as the plastic film and glass, various additives and those in which a plurality of layers are laminated can be used. In addition, in this specification, "polarizing plate" is used in the meaning which includes "polarizing film".

In particular, when the above-mentioned base material is used for optical purposes, for example, an optically transparent plastic film as described above is suitable, but when transparency or the like is not particularly required, a woven fabric or a non-woven fabric is suitable. , A metal vapor-deposited sheet, a metal mesh, or any other base material can be used.

As a method for applying the pressure-sensitive adhesive composition, a known method such as a spin coating method, a knife coating method, a roll coating method, a bar coating method, a blade coating method, a die coating method, or a gravure coating method is used to obtain a predetermined thickness. A method of applying and drying can be used.

The thickness of the adhesive layer is not particularly limited, but is, for example, 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less, still more preferably 15 μm or less, and particularly preferably 12 μm or less. As described above, the pressure-sensitive adhesive composition according to the present invention exhibits particularly excellent performance when forming a thin pressure-sensitive adhesive layer. Therefore, when the adhesive layer is a thin layer, the difference in performance from the case where the conventional composition is used becomes apparent.

[Optical member]
The optical member according to the present invention includes a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition. The method and thickness of the adhesive layer are the same as those described above.

Examples of optical members include polarizing plates, liquid crystal elements, cameras, microscopes, and the like. For example, the polarizing plate includes a polarizing plate main body and an adhesive layer laminated on at least one surface of the polarizing plate main body.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples. In the following examples and the like, unless otherwise specified, "parts" means "parts by mass".

[Mw, Mn]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the (meth) acrylic random polymer and the (meth) acrylic triblock polymer were determined by gel permeation chromatography (GPC method) under the following conditions. ..
-Measuring device: HLC-8320GPC (manufactured by Tosoh Corporation)
-GPC column configuration: The following 4-column column (all manufactured by Tosoh Corporation)
(1) TSKgel HxL-H (guard column)
(2) TSKgel GMHxL
(3) TSKgel GMHxL
(4) TSKgel G2500HxL
・ Flow velocity: 1.0 mL / min
-Column temperature: 40 ° C
-Sample concentration: 1.5% (w / v) (diluted with tetrahydrofuran)
・ Mobile phase solvent: Tetrahydrofuran ・ Standard polystyrene conversion

[Synthesis of (meth) acrylic random polymer]
[Synthesis Examples 1 to 3]
Tables of n-butyl acrylate (BA), acrylic acid (AA), 2-hydroxyethyl acrylate (2HEA), and methyl acrylate (MA) in a reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen introduction tube. The ratio was set to 2, 100 parts of ethyl acetate was charged, and the temperature was raised to 80 ° C. while introducing nitrogen gas. Next, 0.1 part of tert-butyl peroxypivalate was added, and a polymerization reaction was carried out at 80 ° C. for 6 hours in a nitrogen gas atmosphere. After completion of the reaction, a polymer solution having a solid content concentration of 30% by mass was prepared by diluting with ethyl acetate. The characteristics of the obtained (meth) acrylic copolymer are shown in Table 2.

[Synthesis of (meth) acrylic block polymer]
[Synthesis Example 4]
In a flask equipped with a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser, 50 parts by weight of methyl acrylate, bis [4- {ethyl-2- (hydroxyethyl) aminocarbonyl} -benzyl] trithiocarbonate, The contents of the flask were heated to 80 ° C. while introducing 10 parts by weight of nitrogen gas into the flask. Next, 0.03 part by weight of AIBN fully replaced with nitrogen gas was added into the flask with stirring, and heating and cooling were performed for 2 hours so that the temperature of the contents in the flask could be maintained at 80 ° C. The 105 ° C. non-volatile content of the acrylic polymer thus obtained was 99.5%. Next, the temperature of the contents in the flask was raised to 90 ° C., and then 50 parts by weight of butyl acrylate was added dropwise over 1 hour. After that, heating and cooling were carried out for 3 hours so that the temperature of the contents in the flask could be maintained at 90 ° C., and finally 25 parts by weight of ethyl acetate was added.

As described above, the (meth) acrylic triblock polymer MBM1 was obtained. The characteristics of the triblock polymer MBM1 are shown in Table 3 below.

[Synthesis Examples 5-8]
The (meth) acrylic triblock polymers MBM2-5 were synthesized in the same manner as in Synthesis Example 4, except that the weight average molecular weight of the finally obtained polymer was as shown in Table 3.
[Synthesis Example 9]
The (meth) acrylic triblock polymer BMB1 was prepared in the same manner as in Synthesis Example 4, except that the order of adding the monomers was changed and the weight average molecular weight of the finally obtained polymer was as shown in Table 3. Synthesized.

[Synthesis Example 10]
In the same manner as in Synthesis Example 4, except that the bis [4- {ethyl-2- (hydroxyethyl) aminocarbonyl} -benzyl] trithiocarbonate was changed to cyanomethyl N-methyl-N-phenyldithiocarbamate. A (meth) acrylic diblock polymer MB was synthesized. The properties of the diblock polymer MB are shown in Table 3 above.

[Examples 1 to 10 and Comparative Examples 1 to 6]
The (meth) acrylic polymer obtained in Synthesis Examples 1 to 10 and Coronate L (manufactured by Tosoh Corporation) as an isocyanate-based cross-linking agent were mixed in the combinations and ratios shown in Tables 4 and 5 below. A pressure-sensitive adhesive composition was obtained.

Each of the obtained pressure-sensitive adhesive compositions was applied to a light release film after adjusting the thickness of the pressure-sensitive adhesive layer after drying as shown in Tables 4 and 5, and after drying, a PET film having a thickness of 25 μm. Transferred to (Lumirror: manufactured by Toray Industries, Inc.). In this way, an adhesive layer was formed on the base material to produce an adhesive sheet. The thickness of the adhesive layer is also shown in Tables 4 and 5.

[Gel fraction]
0.1 g of the pressure-sensitive adhesive layer obtained in Examples and the like was placed in a sample bottle, 30 cc of ethyl acetate was added and allowed to permeate for 24 hours, and then the contents of the sample bottle were filtered through a 200-mesh stainless steel wire mesh. The weight of the residue after drying on a wire mesh at 100 ° C. for 2 hours was defined as the dry weight. Using the obtained weight measurement value, the gel fraction was calculated from the following formula. The results are also shown in Tables 4 and 5 above.

Gel fraction (%) = 100 x (dry weight / weight of collected adhesive layer)

[Adhesive force]
Using the pressure-sensitive adhesive sheet prepared in the above procedure, the exposed pressure-sensitive adhesive layer surface was pressure-bonded (attached) to a SUS plate using a 2 kg roller under 25 ° C./50% RH conditions. After allowing to stand for 20 minutes after application, the adhesive sheet is peeled from the SUS plate at a peeling speed of 300 mm / min under the conditions of 25 ° C./50% RH and a peeling angle of 180 °, and the peeling force (adhesiveness) of the adhesive layer of the adhesive sheet Force) was measured. The results are also shown in Tables 4 and 5 above.

[Holding power]
The holding force is performed in accordance with JIS Z 1541, the adhesive sheet is cut to a width of 20 mm, attached to a stainless steel plate so that an area of 20 x 20 mm is in contact, and a load of 1 kg is applied under the condition of a temperature of 80 ° C. for 1 hour. The presence or absence of falling when left unattended was observed. The results are also shown in Tables 4 and 5 above.

[Constant load peelability]
The exposed adhesive layer surface was attached to the lower surface side of the stainless steel substrate arranged so that the front and back surfaces were parallel to the horizontal direction. Next, the peeling distance in the longitudinal direction of the test piece when the test piece attached to the stainless steel substrate is left for 60 minutes with a load applied to the one end side in the longitudinal direction in the vertical direction (the peeling distance in the longitudinal direction). mm) or the time to drop (min) was measured. The load was 200 g when the measurement temperature was 40 ° C. and 100 g when the measurement temperature was 80 ° C. The results are also shown in Tables 4 and 5 above.

[Analysis of results]
In Examples 1 to 10, a (meth) acrylic random polymer and a (meth) acrylic triblock polymer having a weight average molecular weight (Mw) of 3,000 to 30,000 as measured by a gel permeation chromatography method were used. By using the pressure-sensitive adhesive composition contained therein, excellent pressure-sensitive adhesive strength, holding power, and constant load peeling property could be achieved. On the other hand, in Comparative Examples 1 to 6, since the pressure-sensitive adhesive composition containing no (meth) acrylic triblock polymer having a weight average molecular weight (Mw) of 3,000 to 30,000 was not used, the adhesive strength was not used. Alternatively, at least one of the constant load peeling properties is not excellent. Therefore, it was clarified that the pressure-sensitive adhesive compositions prepared in Examples 1 to 10 are superior to the pressure-sensitive adhesive compositions prepared in Comparative Examples 1 to 6.

Claims (10)

(Meth) acrylic-based random polymer, the weight average molecular weight measured by gel permeation chromatography method (Mw) is 3,000 to 1 0,000 (meth) PSA composition containing an acrylic triblock polymers Stuff. The pressure-sensitive adhesive composition according to claim 1, wherein the blending amount of the (meth) acrylic triblock polymer is in the range of 1 to 49 parts by mass with respect to 100 parts by mass of the (meth) acrylic random polymer. The (meth) acrylic triblock polymer has a structure represented by [A]-[B]-[A] by the block [A] and the block [B], according to claim 1 or 2. The pressure-sensitive adhesive composition described. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, further comprising an isocyanate-based cross-linking agent. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, which is used for optical applications. A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5. With the base material
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed on at least one surface of the base material by the pressure-sensitive adhesive composition according to any one of claims 1 to 6. The pressure-sensitive adhesive sheet according to claim 7, wherein the thickness of the pressure-sensitive adhesive layer is 15 μm or less. An optical member including an adhesive layer formed by the adhesive composition according to any one of claims 1 to 5. The optical member according to claim 9, wherein the thickness of the adhesive layer is 15 μm or less.