JP2003327933A - Pressure sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a pressure sensitive adhesive sheet having a pressure sensitive adhesive layer formed by using an acrylic emulsion type pressure sensitive adhesive, mild to the environment and excellent in resistance to the spewing of the pressure sensitive adhesive and water resistance. <P>SOLUTION: This pressure sensitive adhesive sheet is applied with the pressure sensitive adhesive layer by using the acrylic emulsion type pressure sensitive adhesive obtained by emulsion polymerization in the presence of a tackifier and having ≥50% gel fraction and ≤300 nm average particle size on one side of a film substrate material. The adhesive sheet has retaining power expressed by ≤300 μm shear of the sheet measured after 70000 seconds in a specific condition and whitening resistance to water expressed by ≤7.00 haze value of the sheet after 24 hours of immersion in warm water at 60°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adhesive sheet,
More specifically, it has a pressure-sensitive adhesive layer formed using an acrylic emulsion pressure-sensitive adhesive on one surface of the film substrate,
The present invention relates to a pressure-sensitive adhesive sheet which is environmentally friendly and has good adhesive performance even on adherends such as polyolefin having low polarity and which is excellent in sticking out property (holding power) and water resistance.

[0002]

2. Description of the Related Art In recent years, pressure-sensitive adhesive sheets do not require high pressure or energy to obtain a practical adhesive force like ordinary adhesives. It is used in many fields because it is easy to use (pressure-sensitive tack) in use and has good workability in use.

Applications of this pressure-sensitive adhesive sheet include, for example, packaging / bundling, office / household use, joining, paint masking, surface protection, anticorrosion / waterproofing, sealing, electrical insulation, electronic equipment / optical parts. For medical and hygiene materials, identification
Examples include decorations and labels. This pressure-sensitive adhesive sheet is generally composed of a base material sheet, a pressure-sensitive adhesive layer formed on the surface of the base material sheet, and a release sheet provided on the pressure-sensitive adhesive layer as necessary. When used, the release sheet is provided. If it is, peel off the release sheet,
The pressure-sensitive adhesive layer is brought into contact with an adherend to be attached.

Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer include acrylic type, urethane type, rubber type, and silicone type. Among them, the adhesive force, the holding force, the weather resistance,
Acrylic adhesives are often used from the viewpoint of performance such as heat resistance. As the acrylic pressure-sensitive adhesive, solvent-type ones have hitherto been mainly used, but in recent years, volatilization of an organic solvent at the time of coating has become a problem in terms of environmental hygiene and safety.

On the other hand, the emulsion type has no particular problems in terms of environment, hygiene, and safety, and high-speed coating due to high concentration and cost reduction due to solvent removal are possible. Instead of the solvent type, emulsion type has come to be used. By the way, in the acrylic emulsion pressure-sensitive adhesive,
For adherends with low polarity such as polyolefins, cohesive force is sacrificed in order to improve adhesion to the adherend, and adhesives with increased wettability to the adherend are often used. There is. Such an acrylic pressure-sensitive adhesive having a low cohesive force is likely to cause the pressure-sensitive adhesive to squeeze out after slitting or after punching, especially in the summer. Also,
A tackifier is usually added to improve adhesion performance to polyolefins and the like. However, in this case, since the emulsified tackifier is blended in the acrylic resin emulsion, a large amount of emulsifier is present, and as a result, the water resistance of the acrylic pressure-sensitive adhesive is unavoidably reduced. There was a problem.

Therefore, in order to avoid a decrease in water resistance due to the emulsifier, for example, a method of decreasing the dispersed particle size in the emulsion (JP-A-62-297372), a method of increasing the crosslink density, and a reactive emulsifier are used. Method to be used
-202488) and the like have been proposed. However, it was not always sufficiently satisfactory as an adhesive having good adhesive strength, holding power and water resistance.

Further, a method of emulsion-polymerizing an ethylenically unsaturated monomer as a raw material in the presence of a tackifier has been attempted, instead of blending the emulsified tackifier (Japanese Patent Laid-Open No. Hei. No. 202488, Japanese Patent Laid-Open No. 2001-34
No. 8551). However, in this case, there is a problem that polymerization inhibition and aggregates are likely to occur, and when the tackifier is a rosin type, chain transfer occurs and the degree of polymerization becomes low.

[0008]

Under the circumstances, the present invention has a pressure-sensitive adhesive layer formed using an acrylic emulsion-type pressure-sensitive adhesive, and is environmentally friendly and has a low polarity such as polyolefin. It is an object of the present invention to provide a pressure-sensitive adhesive sheet that has good adhesiveness to an adherend and is excellent in sticking-out resistance (holding power) and water resistance.

[0009]

Means for Solving the Problems As a result of intensive studies to develop a pressure-sensitive adhesive sheet having the above-mentioned preferable properties, the present inventors have found that as an acrylic emulsion-type pressure-sensitive adhesive,
It has been found that a pressure-sensitive adhesive sheet obtained by using a pressure-sensitive adhesive having a gel fraction of a certain value or more and an average particle diameter of a certain value or less, and having a specific holding power and water whitening resistance can meet the purpose. . The present invention has been completed based on such findings.

That is, the present invention is (1) obtained by emulsion polymerization on one surface of a film substrate in the presence of a tackifier, having a gel fraction of 50% or more and an average particle diameter of 300.
A pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer using an acrylic emulsion pressure-sensitive adhesive having a thickness of nm or less, wherein (a) the pressure-sensitive adhesive layer has a thickness of 20 μm, a sheet shape of 25 mm × 25 mm, a test plate SUS380, and drying at 40 ° C. Under the conditions of load 9.
The amount of sheet deviation after 70000 seconds measured at 8N is 300
a pressure-sensitive adhesive sheet having a holding power of μm or less, and (b) water-whitening resistance having a sheet haze value of 7.00 or less after being immersed in warm water of 60 ° C. for 24 hours,

(2) An acrylic emulsion-type pressure-sensitive adhesive is obtained by emulsion-polymerizing an ethylenically unsaturated monomer with a reactive emulsifier in the presence of a tackifier, and has a keto group as an internal cross-linking agent. The pressure-sensitive adhesive sheet (1) and (3) the acrylic emulsion-type pressure-sensitive adhesive using the contained ethylenically unsaturated monomer are reactive with the ethylenically unsaturated monomer in the presence of the tackifier. The presence of a tackifier in the pressure-sensitive adhesive sheet (1) and (4) an acrylic emulsion-type pressure-sensitive adhesive obtained by emulsion polymerization using an emulsifier and using a hydrazide compound as an external crosslinking agent. The adhesive sheet according to (1) above, which is obtained by emulsion-polymerizing an ethylenically unsaturated monomer using a reactive emulsifier and uses an internal crosslinking agent and an external crosslinking agent as the crosslinking agent. (5) The pressure-sensitive adhesive sheet according to any one of (2) to (4), wherein the amount of the reactive emulsifier used is in the range of 0.5 to 8% by weight based on the total amount of the ethylenically unsaturated monomer. Is.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The film substrate in the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and known films conventionally used as film substrates for pressure-sensitive adhesive sheets such as polyester (eg, polyethylene terephthalate,
Vapor-deposited polyethylene terephthalate, polyethylene naphthalate), polyolefins (eg polypropylene, polyethylene), polyvinyl chloride, polyvinylidene chloride,
Examples thereof include plastic films such as polystyrene, polycarbonate and polyvinyl alcohol, cellulose-based films such as cellulose triacetate, cellulose diacetate and cellophane, and synthetic paper. The thickness of this substrate may be appropriately determined depending on the purpose of use and the situation, but is usually 10 to 250 μm, preferably 25 to 10 μm.
It is in the range of 0 μm.

When a plastic film is used as the base material, one surface or both surfaces thereof may be roughened by sandblasting, solvent treatment, or the like, if desired, for the purpose of improving the adhesiveness with a layer provided thereon. processing,
Alternatively, corona discharge treatment, ozone / ultraviolet irradiation treatment, flame treatment, chromic acid treatment, hot air treatment, or other oxidation treatment can be performed.

In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer provided on one surface of the film substrate is obtained by emulsion polymerization as a pressure-sensitive adhesive in the presence of a tackifier and has a gel fraction of 50%. Above, an acrylic emulsion type adhesive having an average particle diameter of 300 nm or less is used. If the gel fraction is less than 50%, it is difficult to obtain a pressure-sensitive adhesive sheet having a low cohesive force, a desired holding power, and excellent sticking-out property of the pressure-sensitive adhesive, and the object of the present invention cannot be achieved. Further, if the gel fraction is too high, the adhesive performance may be insufficient, so the preferable gel fraction is in the range of 55 to 65%. The gel fraction is a value measured by the following method.

<Measurement Method of Gel Fraction> 1) The weight of SUS wire mesh is measured. 2) A test piece in which the adhesive of the present invention is applied to one side of a polyethylene terephthalate (PET) film having a thickness of 50 mm × 50 mm and a thickness of 50 μm is attached to a SUS wire net and the weight is measured. 3) Immerse in ethyl acetate (about 200 cc), and at 23 ° C,
Leave for 24 hours. 4) The test piece is taken out, dried under vacuum at 100 ° C. for 2 hours, and the weight after drying is measured. 5) The test piece is peeled off from the SUS wire mesh, and the weight of only the PET film (base material) from which the remaining adhesive is removed is measured. 6) Calculate the gel fraction (%) from the following formula. (Weight after drying-weight of wire mesh-weight of base material) x 100 / {(weight of wire mesh + test piece) -weight of wire mesh-weight of base material}

On the other hand, when the average particle diameter of the acrylic emulsion type pressure-sensitive adhesive exceeds 300 nm, the emulsion stability is poor, and a pressure-sensitive adhesive sheet having a desired adhesive property, particularly an adhesive property to polyolefin cannot be obtained. The object of the present invention cannot be achieved. The lower limit of the average particle size is not particularly limited, but it is usually 50 nm industrially.
It is a degree. More preferably, it is 250 nm to 150 nm. In addition, this average particle diameter is a value measured by the following method. <Measurement Method of Average Particle Size> The acrylic emulsion pressure-sensitive adhesive of the present invention filtered after synthesis is diluted to 100 ppm with water. This dispersion was added to NICOMP Model 370.
(Particle Sizing Systems I
nc. (Manufactured by Mitsui Chemicals Co., Ltd.) was used to measure by light scattering method.

In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer has a thickness of 20 μm, a sheet shape of 25 mm × 25 mm, a test plate of SUS380 and a load of 9.8 under dry conditions at 40 ° C.
The amount of sheet deviation after 300,000 seconds measured by N is 300.
It has a holding power of less than μm. If the amount of deviation of this sheet exceeds 300 μm, the holding force becomes insufficient, and the desired pressure-sensitive adhesive cannot be squeezed out, which may cause squeeze-out of the adhesive after slitting or punching. 7
The sheet deviation amount after 0000 seconds is preferably 200 μm or less, and particularly preferably 150 μm or less. The method for measuring the holding force is shown below.

Further, the sheet has a haze value of 7.00 or less after being immersed in warm water of 60 ° C. for 24 hours, and has water whitening resistance. When the haze value of this sheet exceeds 7.00, the water resistance becomes insufficient and the object of the present invention cannot be achieved. The haze value is preferably 6.00 or less, and particularly 5.
A value of 00 or less is suitable.

In the pressure-sensitive adhesive sheet of the present invention, as an acrylic emulsion-type pressure-sensitive adhesive, it is obtained by emulsion polymerization in the presence of a tackifier, and has the above-mentioned gel fraction and average particle size, and the pressure-sensitive adhesive sheet obtained. However, it is necessary to use an adhesive having the above-mentioned properties. Such an acrylic emulsion-type pressure-sensitive adhesive is obtained by emulsion-polymerizing an ethylenically unsaturated monomer with a reactive emulsifier in the presence of a tackifier, and (1) as a cross-linking agent containing a keto group-containing ethylene. By using a polyunsaturated monomer, (2) using a hydrazide compound as an external crosslinking agent, or (3) using an internal crosslinking agent and an external crosslinking agent in combination.
It can be manufactured. The internal crosslinking agent here is
At the time of polymerization, it refers to a cross-linkable reactive monomer capable of introducing a cross-linking structure into the polymer molecule, while the external cross-linking agent refers to a compound capable of introducing a cross-linking structure between polymer particles. When an external crosslinking agent is used, it is essential that the polymer particles to be crosslinked have a crosslinkable functional group introduced into the molecule.

As the acrylic resin contained in the acrylic emulsion pressure-sensitive adhesive according to the present invention, a (meth) acrylic acid ester-based polymer which is a polymer obtained from an ethylenically unsaturated monomer is used. As this (meth) acrylic acid ester-based polymer, an arbitrary one can be appropriately selected and used from the (meth) acrylic acid ester-based polymers used in ordinary acrylic pressure-sensitive adhesives. Examples thereof include (meth) acrylic acid ester homopolymers, copolymers containing two or more kinds of (meth) acrylic acid ester units, and (meth) acrylic acid esters and other functional monomers and others. Examples thereof include a copolymer with an ethylenically unsaturated monomer such as the above monomer. These may be used alone or in combination of two or more kinds.

The (meth) acrylic acid ester is preferably a (meth) acrylic acid ester having an alkyl group having 1 to 20 carbon atoms, specifically, methyl (meth) acrylate and ethyl (meth) acrylate. , Propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid 2
-Ethylhexyl, isooctyl (meth) acrylate,
Examples thereof include decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. These may be used alone or in combination of two or more.

Examples of other functional monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) acrylic. (Meth) acrylic acid hydroxyalkyl ester such as 2-hydroxybutyl acid, 3-hydroxybutyl (meth) acrylic acid, 4-hydroxybutyl (meth) acrylic acid; acetoacetoxymethyl (meth) acrylate; acrylamide, methacrylamide, N-methyl acrylamide,
Acrylamides such as N, N-dimethylacrylamide, N-methylmethacrylamide, N, N-dimethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, and diacetoneacrylamide; (meth) acrylic acid mono Or (meth) acrylate mono- or dialkylaminoalkyl such as dimethylaminoethyl, mono- or diethylaminoethyl (meth) acrylate, mono- or dimethylaminopropyl (meth) acrylate, mono- or diethylaminopropyl (meth) acrylate; acrylic acid , Ethylenically unsaturated carboxylic acids such as methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid. These monomers may be used alone or in combination of two or more.

The functional group in this functional monomer serves as a crosslinking point when an external crosslinking agent is used. Further, other monomers include, for example, vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene,
Examples include stainless steel-based monomers such as α-methylstyrene; diene-based monomers such as butadiene, isoprene, and chloroprene; nitrile-based monomers such as acrylonitrile and methacrylonitrile. These may be used alone or in combination of two or more. Also,
Examples of the cross-linking reactive monomer that is an internal cross-linking agent include polyfunctional ethylenically unsaturated monomers, keto group-containing ethylenically unsaturated monomers, and alkoxysilyl group-containing ethylenically unsaturated monomers. Can be mentioned.

Here, as the polyfunctional ethylenically unsaturated monomer, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate,
Polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butylene glycol di (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, Trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, glycerin methacrylate acrylate, tris (meth) Methacryloyloxy phosphate, glycerin di (meth) acrylate, diallyl terephthalate, tetraallyloxyethane, divinylbenzene, tri (meth) allyl isocyanurate.

Examples of the keto group-containing ethylenically unsaturated monomer include diacetone acrylamide, 2- (acetoacetoxy) ethyl (meth) acrylate, acetoacetoxymethyl (meth) acrylate and allyl acetoacetate. Examples of the alkoxysilyl group-containing ethylenically unsaturated monomer include 2- (meth) acryloxyethyltrimethoxysilane, 2- (meth) acryloxyethyltriethoxysilane, and γ- (meth) acryloxypropyltrimethoxysilane. , Γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ
-(Meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, γ- (meth) acryloxypropyltrichlorosilane, γ- (meth) acryloxypropylmethyldichlorosilane, γ- ( (Meth) acryloxypropyldimethylchlorosilane, γ- (meth) acryloxypropyltripropoxysilane, γ- (meth) acryloxypropylmethyldipropoxysilane, γ- (meth) acryloxypropyltributoxysilane, (meth) Acryloxybutyltrimethoxysilane, (meth) acryloxypentyltrimethoxysilane, (meth) acryloxyhexyltrimethoxysilane, (meth) acryloxyhexyltriethoxysilane, (meth) acryloxyoctyltrimethoxysilane , (Meth) acryloxy-decyl trimethoxysilane, (meth) acryloxy dodecyl trimethoxy silane, (meth) acryloxy-octadecyl trimethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropoxysilane,
Examples thereof include vinylmethyldimethoxysilane, vinylmethyldiethoxysilane and vinylmethyldipropoxysilane.

These internal cross-linking agents may or may not be used when a hydrazide compound is used as the external cross-linking agent, but when an external cross-linking agent is not used or when an external cross-linking agent other than the hydrazide compound is used. It becomes indispensable when a crosslinking agent is used. The internal cross-linking agents may be used alone or in combination of two or more, and among these, keto group-containing ethylenically unsaturated monomers are particularly preferable. The content of the internal cross-linking agent is preferably 1.0 to 10.0 parts by weight with respect to 100 parts by weight of the acrylic emulsion.

On the other hand, examples of the external cross-linking agent include isocyanate compounds, epoxy compounds, melamine compounds, aziridine compounds, hydrazide compounds, oxazoline compounds, carbodiimide compounds, urea compounds, dialdehyde compounds, and metals. Examples thereof include chelate compounds, metal alkoxides and metal salts. These may be used alone or in combination of two or more, and among these, a hydrazide compound is particularly preferable from the viewpoint of performance. Examples of the hydrazide compound include adipic acid hydrazide and carbohydrazide. The compounding amount of the external crosslinking agent is preferably 0.2 to 7.0 parts by weight with respect to 100 parts by weight of the acrylic emulsion.

These external cross-linking agents are used when the keto group-containing ethylenically unsaturated monomer is used as the internal cross-linking agent.
Although it may or may not be used, it is essential when no internal cross-linking agent is used or when an internal cross-linking agent other than the keto group-containing ethylenically unsaturated monomer is used. When the above-mentioned cross-linking agent is used in combination, the amount of acrylic emulsion 10
0.5 to 5.0 parts by weight of the internal crosslinking agent with respect to 0 parts by weight,
The external cross-linking agent is preferably 0.2 to 0.4 part by weight. The internal cross-linking agent is added at the time of polymerization, but the external cross-linking agent is added to the acrylic resin emulsion obtained by emulsion polymerization.

The tackifier used in the acrylic emulsion type pressure-sensitive adhesive according to the present invention is not particularly limited, and can be appropriately selected and used from those conventionally used as a tackifier in conventional pressure-sensitive adhesives. . Examples of the tackifier include rosin resin, xylene resin, terpene-phenol resin, petroleum resin, coumarone indene resin, terpene resin, styrene resin, ethylene / vinyl acetate resin, styrene-butadiene block polymer, and styrene-isoprene. Examples thereof include block polymers, ethylene-isoprene-styrene block polymers, vinyl chloride / vinyl acetate-based polymers, and elastomers such as acrylic rubber.

Specific examples of commercially available products include Super Ester A-75 (manufactured by Arakawa Chemical Co., Ltd.) and Super Ester A-1.
00 (manufactured by Arakawa Chemical Co., Ltd.), super ester A-125
(Arakawa Chemical Co., Ltd.) rosin ester, Pencel D12
Polymerization rosin ester such as 5 (manufactured by Arakawa Chemical Co., Ltd.), Pencel D160 (manufactured by Arakawa Chemical Co., Ltd.), Rikatak PCJ (manufactured by Rika Finetech Co., Ltd.), Nikanol HP-100 (manufactured by Mitsubishi Gas Chemical Co., Inc.), Nikanol HP-150 (Mitsubishi Gas Chemical Co., Ltd.), xylene resin such as Nikanol H-80, YS
Polyster T-115 (manufactured by Yasuhara Chemical Co., Ltd.), terpene-phenolic resin such as Mitec G125 (manufactured by Yasuhara Chemical Co., Ltd.), petroleum resin such as FTR-6120 (manufactured by Mitsui Chemicals, Inc.), FTR-6100 (manufactured by Mitsui Chemicals, Inc.), etc. is there. These tackifiers may be used alone or in combination of two or more.

In the present invention, the compounding amount of the tackifier is usually 1 with respect to 100 parts by weight of the total amount of each ethylenically unsaturated monomer used as a raw material of the acrylic resin.
It is selected in the range of 50 parts by weight. If this amount is less than 1 part by weight, it is difficult to obtain sufficient adhesiveness, particularly for polyolefins. On the other hand, if it exceeds 50 parts by weight, polymerization becomes unstable and sufficient adhesiveness and tack cannot be obtained. Is not preferable. The preferred blending amount of this tackifier is 5 to 40 parts by weight, especially 7 to 3
A range of 0 parts by weight is preferred.

The acrylic emulsion type pressure-sensitive adhesive according to the present invention is produced by emulsion-polymerizing each ethylenically unsaturated monomer in the presence of the above-mentioned tackifier. In this emulsion-polymerization, an emulsifier is used. A reactive emulsifier is used as. The reactive emulsifier is not particularly limited and can be appropriately selected and used from conventionally known ionic and nonionic emulsifiers. Examples of the reactive emulsifier include general formulas (I) to (VII)

[0033]

[Chemical 1]

[0034]

[Chemical 2]

(Wherein R ¹ is an alkyl group, R ² is a hydrogen atom or a methyl group, R ³ is an alkylene group, X is a hydrogen atom or a sulfonate group, and n, m and k are integers of 1 or more. And a compound having a structure represented by m + k = 3).

Specific examples of such reactive emulsifiers include commercially available products such as ADEKA REASOAP SE-20N (anionic), ADEKA REASOAP SE-10N (anionic) and ADEKA REASOAP NE-10 (nonionic). , ADEKA rear soap NE-20 (nonionic), ADEKA rear soap NE-30 (nonionic), ADEKA rear soap N
E-40 (nonionic), ADEKA rear soap SDX-7
30 (anionic), ADEKA rear soap SDX-731
(Anionic) [above, manufactured by Asahi Denka Co., Ltd.], Eleminol JS-2 (anionic), Eleminol RS-30
(Anionic) [above, Sanyo Kasei Co., Ltd.], Latemul S-180A (anionic), Latemul S-180 (anionic) [above, Kao Corporation], Aqualon BC-
05 (anionic), AQUARON BC-10 (anionic), AQUARON BC-20 (anionic), AQUARON HS-05 (anionic), AQUARON HS-10
(Anionic), AQUARON HS-20 (anionic), AQUARON RN-10 (nonionic), AQUARON RN-20 (nonionic), AQUARON RN-30
(Nonionic), Aqualon RN-50 (Nonionic), New Frontier S-510 (Anion) [above, Dai-ichi Kogyo Seiyaku Co., Ltd.], Phosphinol TX
(Anionic) [manufactured by Toho Chemical Industry Co., Ltd.] and the like can be mentioned. By using such a reactive emulsifier, an acrylic emulsion-type pressure-sensitive adhesive having good water resistance can be obtained.

The reactive emulsifiers may be used alone or in combination of two or more. Further, the amount of the reactive emulsifier to be blended is 1 total amount of each ethylenically unsaturated monomer used as a raw material of the acrylic resin.
It is usually selected in the range of 0.5 to 8 parts by weight with respect to 00 parts by weight. If the blending amount is less than 0.5 part by weight, it is difficult to obtain an emulsion-type pressure-sensitive adhesive having an average particle size of 300 nm or less, and the polymerization tends to be unstable, while if it exceeds 8 parts by weight, the water resistance of the pressure-sensitive adhesive sheet obtained is increased. Cause decrease. The amount of the reactive emulsifier to be added is preferably 0.8 to 7 parts by weight, and particularly preferably 1 to 5 parts by weight.

Next, a preferred embodiment of the method for producing an acrylic emulsion pressure-sensitive adhesive according to the present invention will be described. First, the reactive emulsifying agent is dissolved in an aqueous medium, and then each ethylenically unsaturated monomer as a raw material of an acrylic resin and a tackifier are added in a predetermined ratio to perform an emulsification treatment. At this time, the amount of the aqueous medium used is usually 50 to 400 parts by weight, preferably 70 to 200 parts by weight based on 100 parts by weight of the total amount of the ethylenically unsaturated monomer and the tackifier.
The range is parts by weight.

The emulsification treatment is preferably carried out using a high-pressure homogenizer or ultrasonic waves. In this case, the emulsion-type pressure-sensitive adhesive finally obtained is emulsified so that the average particle diameter thereof is 300 nm or less. To prepare an emulsion. Next, the emulsion thus prepared is heated to about 40 to 90 ° C. in the presence of a polymerization initiator to carry out polymerization. At this time, as the polymerization initiator, conventionally known compounds such as organic peroxides, azo compounds, persulfates and various redox catalysts can be used.

If necessary, the above-mentioned external cross-linking agent is added to the acrylic resin emulsion thus obtained,
Further, if desired, various additives such as antiseptic and antifungal agents,
Freeze-thaw stabilizer, rust inhibitor, plasticizer, high boiling point solvent, pigment,
Fillers and the like can be added. In this way
A desired acrylic emulsion type pressure-sensitive adhesive can be obtained.

In the pressure-sensitive adhesive sheet of the present invention, the above-mentioned acrylic emulsion-type pressure-sensitive adhesive is used on one surface of the film substrate, and the thickness is usually 5 to 100 μm, preferably 10 to 10.
An adhesive layer in the range of 60 μm is provided. Examples of the method of providing the pressure-sensitive adhesive layer include a method of directly applying the emulsion-type pressure-sensitive adhesive to one surface of a film substrate by a known method to form the pressure-sensitive adhesive layer, or the emulsion-type pressure-sensitive adhesive on a release sheet. Can be applied by a known method to form a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer is attached to one surface of the film substrate and the pressure-sensitive adhesive layer is transferred.

In the pressure-sensitive adhesive sheet of the present invention, a release sheet can be provided on the pressure-sensitive adhesive layer thus formed, if desired. Examples of the release sheet include high-density base paper such as glassine paper, clay-coated paper,
Kraft paper, high-quality paper and other laminated paper laminated with polyethylene resin, or polyethylene terephthalate, polyethylene naphthalate, polyolefin and other plastic films, release agent such as fluororesin and silicone resin in dry weight 0.1 to 3 g / m
Examples thereof include those having a release layer which is applied by about ² and is heat-cured or UV-cured. The thickness of this release layer is not particularly limited, but is usually 25 to 20.
It is in the range of 0 μm.

[0043]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The various properties of the pressure-sensitive adhesive sheet obtained in each example were determined according to the procedures described below.

(1) Adhesive strength The adhesive sheet is adhered to a polyethylene plate (Japan test panel standard test plate) at 23 ° C. and 50% RH, and JIS is applied.
The 180-degree peel strength was measured according to the method for measuring the adhesive strength of Z 0237.

(2) As shown in FIG. 1, only the base material is cut out from the pressure-sensitive adhesive sheet which has a resistance to sticking out, as shown in FIG. 1 (in FIG. 1, the shaded portion is the cutout portion). Then, a polyethylene terephthalate (PET) film having a thickness of 50 μm was overlaid, and a press test was performed for 24 hours under an atmosphere of 40 ° C. and a pressure of 5.9 N / mm ² . The protrusion of the pressure-sensitive adhesive for 24 hours was visually observed, and the pressure-sensitive adhesive protrusion resistance was evaluated according to the following criteria. ◯: There is no protrusion of the adhesive. Δ: Slight sticking out of the adhesive can be confirmed. X: The protrusion of the adhesive can be confirmed.

(3) Coercive power The emulsion of the sample is dried and coated on a release paper so as to have a thickness of 20 μm, and dried at 90 ° C. for 1 minute, and then 50
A pressure-sensitive adhesive sheet is prepared by laminating a PET film having a metal vapor deposition of μm. The adhesive sheet was attached to a stainless plate (S
US380) test plate with an area of 25 mm x 25
It is attached so that it becomes mm, and it is 9.8 under the condition of 40 ° C drying.
A load of N is applied, and the amount of deviation of the film after 70,000 seconds is measured according to the method for measuring the holding force of JIS Z 0237.

(4) Water whitening resistance Emulsion of a sample was coated on a release paper to give a thickness of 20 μm and dried at 90 ° C. for 1 minute, and then 50
A pressure-sensitive adhesive sheet is prepared by laminating it on a PET film having a thickness of μm. Then, the release paper is peeled off and laminated on a PET film of 50 μm, and then a test piece of 50 mm × 50 mm is prepared. Next, after leaving the test piece in warm water at 60 ° C. for 24 hours, the test piece is taken out from the warm water and the haze value thereof is measured with a haze meter.

Example 1 (1) Emulsion polymerization 125 parts by weight of ion-exchanged water, 3 parts by weight of anionic reactive emulsifier "Latemuru S-180A" (manufactured by Kao Corporation), and sodium diphosphate 0.3. Parts by weight, 0.5 parts by weight of ammonium persulfate, 2-ethylhexyl acrylate 4
From 2 parts by weight, 53 parts by weight of n-butyl acrylate, 3 parts by weight of acrylic acid, 2 parts by weight of diacetone acrylamide and 18 parts by weight of tackifier "Bencel D-125" (manufactured by Arakawa Chemical Co., Ltd., polymerized rosin ester type). The resulting mixed solution is emulsified with a high pressure homogenizer to obtain an average particle size of 250.
nm emulsion was prepared. Next, this emulsion is heated to 80 ° C.
The emulsion was polymerized by heating for 8 hours to obtain an acrylic resin emulsion.

(2) Preparation of pressure-sensitive adhesive To 100 parts by weight of the acrylic resin emulsion obtained in (1) above, 0.45 part by weight of adipic hydrazide as an external crosslinking agent was added to prepare an acrylic emulsion-type pressure-sensitive adhesive. Was prepared. The acrylic emulsion pressure-sensitive adhesive had a gel fraction of 62% and an average particle diameter of 200 nm.

(3) Preparation of pressure-sensitive adhesive sheet The acrylic emulsion pressure-sensitive adhesive prepared in (2) above was used as a release sheet "SP-8LK2" (manufactured by Lintec Corporation).
Apply it so that the thickness after drying will be 20 μm.
After drying at 0 ° C. for 1 minute, it was attached to a PET film having a thickness of 50 μm to prepare an adhesive sheet. With respect to this pressure-sensitive adhesive sheet, pressure-sensitive adhesive strength, pressure-sensitive adhesive squeeze-out property, holding power and water whitening resistance were determined. The results are shown in Table 1.

Example 2 In Example 1 (1), 1 part by weight of acrylic acid and 4 parts by weight of acetoacetoxymethyl acrylate as an internal cross-linking agent were used instead of 3 parts by weight of acrylic acid and 2 parts by weight of diacetone acrylamide. Emulsion polymerization was carried out in the same manner as in Example (1) except that the acrylic resin emulsion was obtained. The gel fraction of this emulsion was 56.2%, and the average particle size was 200 nm. Using the above emulsion as an acrylic emulsion type pressure-sensitive adhesive, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 (3),
The anti-adhesive agent was required to have squeeze-out property, holding power and water whitening resistance. The results are shown in Table 1.

Example 3 In Example 1 (1), as a tackifier, "YS-Polystar N-1" was used instead of "Bencel D-125".
25 "(Yasuhara Chemical Co., Ltd., terpene-phenol resin type) was used to prepare an adhesive sheet in the same manner as in Example 1 to obtain adhesive strength, adhesive squeeze-out resistance, holding power and water whitening resistance. I asked. The results are shown in Table 1. The acrylic emulsion pressure-sensitive adhesive has a gel fraction of 65.
%, And the average particle size was 180 nm.

Example 4 In Example 1 (1), as a tackifier, “YS Resin SX-10” was used instead of “Bencel D-125”.
0 "(manufactured by Yasuhara Chemical Co., Ltd., styrene resin type) was used to prepare a pressure-sensitive adhesive sheet in the same manner as in Example 1, and the pressure-sensitive adhesive strength, pressure-sensitive adhesive squeeze-out property, holding power and water-whitening resistance were determined. . The results are shown in Table 1. The acrylic emulsion pressure-sensitive adhesive had a gel fraction of 60% and an average particle diameter of 220 nm.

Example 5 In Example 1, 0.5 parts by weight of diacetone acrylamide as an internal cross-linking agent and 1.5 parts by weight of ethylene glycol diacrylate were added in place of 2 parts by weight of diacetone acrylamide, and externally added. 0.3 part by weight of adipic dihydrazide was added as a cross-linking agent to prepare an acrylic emulsion type pressure-sensitive adhesive. The acrylic emulsion pressure-sensitive adhesive had a gel fraction of 61% and an average particle size of 1
It was 80 nm. Using the above emulsion as an acrylic emulsion type pressure-sensitive adhesive, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 (3), and the pressure-sensitive adhesive strength, pressure-sensitive adhesive squeeze-out property, holding power, and water whitening resistance were determined. The results are shown in Table 1.

Comparative Example 1 (1) Emulsion Polymerization In Example 1 (1), the tackifier "Bencel D-1" was used.
Emulsion polymerization was carried out in the same manner as in Example 1 (1) except that "25" was not used to obtain an acrylic resin emulsion.

(2) Preparation of pressure-sensitive adhesive For the acrylic resin emulsion obtained in (1) above,
Pre-emulsified "Bencel D-125" emulsion having an average particle size of 300 nm was added with 18 parts by weight of "Bencel D-125" and 0.45 part by weight of adipic acid dihydrazide to give an acrylic emulsion-type adhesive. Prepared. The acrylic emulsion pressure-sensitive adhesive had a gel fraction of 60.0% and an average particle diameter of 220 nm. (3) Production of pressure-sensitive adhesive sheet Using the acrylic emulsion-type pressure-sensitive adhesive obtained in (2) above, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 (3),
Adhesion strength, pressure-sensitive adhesive squeeze-out property, holding power and water whitening resistance were determined. The results are shown in Table 1.

Comparative Example 2 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the external crosslinking agent, adipic acid hydrazide, was not used. And the water-whitening resistance. The results are shown in Table 1. The gel fraction of acrylic emulsion adhesive is 1
It was 5.4% and the average particle diameter was 200 nm.

Comparative Example 3 Adhesion was performed in the same manner as in Example 1 except that the nonionic non-reactive emulsifier "Emulgen 920" (manufactured by Kao Corporation) was used in place of the reactive emulsifier in Example 1 (1). A sheet was prepared, and the adhesive strength, the sticking-out resistance of the adhesive, the holding power and the water whitening resistance were determined. The results are shown in Table 1. The gel fraction of the acrylic emulsion adhesive is 60.1%
And the average particle diameter was 210 nm.

Comparative Example 4 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 2 except that the internal cross-linking agent, acetoacetoxymethyl acrylate, was not used in Example 2 (1). The agent's squeeze-out property, holding power and water whitening resistance were sought. The results are shown in Table 1. The acrylic emulsion pressure-sensitive adhesive had a gel fraction of 10.3% and an average particle size of 2
It was 20 nm.

[0060]

[Table 1]

[0061]

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed by using an acrylic emulsion-type pressure-sensitive adhesive on one surface of a film base material, and is environmentally friendly and is coated with a low-polarity polyolefin or the like. It is a pressure-sensitive adhesive sheet that has good adhesiveness to a body and has excellent sticking-out resistance (holding power) and water resistance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for determining the sticking-out resistance of a pressure-sensitive adhesive sheet.

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) C09J 133/06 C09J 133/06 151/00 151/00 (72) Inventor Tatsuya Tsukita 5-14 Nishikicho, Warabi-shi, Saitama Prefecture −42 Lintec Stock Company F-term (reference) 4J004 AA10 AB01 CA02 CA04 CA05 CA06 CB03 CC02 CD08 CD10 4J011 KA06 KA29 KB14 KB29 PA57 PA63 PA64 PA65 PA66 PA68 PA69 PA75 PA76 PA79 PA83 PB39 PC02 PC06 4J026 AA08 A25 A64 A38 AA A AA68 AA69 AA76 AB01 AB46 AC04 AC09 AC16 BA21 BA25 BA27 BA28 BA30 BA32 BA34 BA39 BA41 BA43 BA50 BB01 BB03 BB04 DB04 DB08 DB10 DB12 DB14 DB15 DB28 EA08 4J040 DF011 DF041 DF16HC21HC16 HC16HC21 HC16 HC21HC16 HC21HC16 HC21HC16 HC21HC16 HC21HC16HC21HC16HC16HC21HC16HC16HC21HC16HC17HC21HC16HC17EF21HC06HC17EF21GA06HC17EF15GA06HC17EF15GA06 MA10 MB03 PA02 PA23

Claims (5)

[Claims] 1. An acrylic emulsion pressure-sensitive adhesive having a gel fraction of 50% or more and an average particle diameter of 300 nm or less, which is obtained by emulsion-polymerizing one surface of a film substrate in the presence of a tackifier. A pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer, comprising: (a) thickness of the pressure-sensitive adhesive layer 20 μm, sheet shape 25 mm × 25 mm, test plate SUS380 and 40 ° C.
Under a dry condition of 7, the sheet has a holding force such that the amount of sheet deviation after 300,000 seconds measured under a load of 9.8 N is 300 μm or less, and (b) the sheet after being immersed in warm water at 60 ° C. for 24 hours. An adhesive sheet having a water whitening resistance having a haze value of 7.00 or less. 2. An acrylic emulsion pressure-sensitive adhesive is obtained by emulsion-polymerizing an ethylenically unsaturated monomer with a reactive emulsifier in the presence of a tackifier, and contains a keto group as an internal cross-linking agent. The pressure-sensitive adhesive sheet according to claim 1, which comprises an ethylenically unsaturated monomer. 3. An acrylic emulsion pressure-sensitive adhesive is obtained by emulsion-polymerizing an ethylenically unsaturated monomer with a reactive emulsifier in the presence of a tackifier, and a hydrazide compound as an external crosslinking agent. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet is used. 4. An acrylic emulsion pressure-sensitive adhesive is obtained by emulsion-polymerizing an ethylenically unsaturated monomer using a reactive emulsifier in the presence of a tackifier, and an internal cross-linking agent and a cross-linking agent are used as a cross-linking agent. The pressure-sensitive adhesive sheet according to claim 1, which uses an external crosslinking agent. 5. The pressure-sensitive adhesive sheet according to claim 2, wherein the amount of the reactive emulsifier used is in the range of 0.5 to 8% by weight based on the total amount of the ethylenically unsaturated monomer.