JP2007224186A - Emulsion type pressure-sensitive adhesive and pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emulsion type pressure-sensitive adhesive forming a pressure-sensitive adhesive layer having excellent water resistance and hardly causing staining of an adherend, and preferably usable for an optical film material or the like; and to provide a pressure-sensitive adhesive sheet using the adhesive. <P>SOLUTION: The emulsion type pressure-sensitive adhesive contains (2) a polymer emulsion obtained by polymerizing (1) a monomer emulsion having ≤10 μm of 50% particle diameter, and containing 0.05-1 pt.wt. of (B) a nonreactive surfactant and water based on 100 pts.wt. of (A) a radically polymerizable unsaturated monomer consisting essentially of an alkyl (meth)acrylate having a 1-8C alkyl group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an emulsion-type pressure-sensitive adhesive and a pressure-sensitive adhesive sheet using the emulsion-type pressure-sensitive adhesive. Specifically, the present invention relates to an emulsion-type pressure-sensitive adhesive that is excellent in water resistance, has little adherend contamination, and can be preferably used for an optical film material and the like, and a pressure-sensitive adhesive sheet using the same.

Various flat panel displays (FPDs) have been used as display devices in various fields. For example, FPDs are not only used indoors, including personal computer displays and liquid crystal televisions, but are also used in vehicles such as car navigation displays. Examples of these FPDs include a liquid crystal display (LCD), a plasma display (PDP), a rear projection display (RPJ), an EL display, and a light emitting diode display.
These display devices include an antireflection film for preventing reflection from an external light source, a light diffusion film for diffusing light from an internal light source, and a protective film for preventing scratches on the surface of the display device ( Protect film) is used.
Further, the FPD is not only used as a display device, but may be used as an input device by providing a touch panel function on the surface thereof. A protective film, an antireflection film, an ITO vapor deposition resin film, and the like are also used for this touch panel.
Further, the LCD of the FPD has a polarizing film or a retardation film laminated on a glass member for a liquid crystal cell.
Further, although not for FPD applications, blindfold sheets and the like for decorating glass are widely used indoors and outdoors.

Various films and sheets used for these are used by being adhered to an adherend with an adhesive. In the above applications, it is placed under high humidity or exposed to cold or warm water, but even under such an environment, it is required that there is no change in appearance, and the adhesive layer has moisture resistance and water resistance. Required. Therefore, a solvent-type pressure-sensitive adhesive that is excellent in water resistance and mainly contains an acrylic resin has been used more favorably than before.
By the way, after sticking a polarizing film to the glass member for liquid crystal cells, the presence or absence of air at the pasting interface and the presence or absence of dust at the pasting interface are inspected. And when there is air and dust, a polarizing film etc. are peeled off from a glass member, and a new polarizing film etc. are stuck again. Therefore, when peeling off a polarizing film, it is calculated | required that an adhesive component does not remain in a glass member, ie, there is no adherend contamination.
Further, even in the case of a blindfold sheet, it is premised that the sheet is peeled off from the glass after fulfilling the purpose.
Here, the surface of the adherend contaminated by the remaining pressure-sensitive adhesive has a high contact angle with water. Therefore, for example, the degree of contamination of the adherend when glass is used as the adherend increases how much the water contact angle on the glass surface after peeling the film is larger than the water contact angle on the original glass surface. It can be estimated from this perspective.

In recent years, from the viewpoint of protecting the global environment (suppressing the emission of volatile organic compounds), improving the working environment, and effectively using resources, the use of water-based emulsion adhesives has been studied as an alternative to solvent-based adhesives.
For example, in Japanese Patent No. 2698536 (Patent Document 1) and Japanese Patent No. 3207001 (Patent Document 2), a monomer containing a long-chain alkyl (meth) acrylate, which is hardly water-soluble, is prepared using water and a surfactant. There has been proposed a method of preparing an emulsion and polymerizing the emulsion to obtain an emulsion-type pressure-sensitive adhesive.
However, since the obtained polymer is water-repellent, adherend contamination is likely to occur.
In JP-A-2000-313865 (Patent Document 3), a monomer emulsion is prepared by using a long-chain alkyl (meth) acrylate and a tackifier resin for improving water resistance using a surfactant and water. Has been proposed to obtain an emulsion-type pressure-sensitive adhesive, but in the method of Patent Document 3, in addition to the adherend contamination occurring, the emulsion-type pressure-sensitive adhesive is weak against light and heat. It contains a resin and cannot be used for FPD applications requiring weather resistance.
As described above, various attempts have been made to give the emulsion-type pressure-sensitive adhesive the same performance as that of the solvent-type pressure-sensitive adhesive, but it has been insufficient so far.
Japanese Patent No. 2698536 Japanese Patent No. 3206001 JP 2000-313865 A

  The present invention provides an emulsion-type pressure-sensitive adhesive that is excellent in water resistance, can form a pressure-sensitive adhesive layer with little adherend contamination, and can be preferably used for optical film materials, and a pressure-sensitive adhesive sheet using the same. For the purpose.

In order to solve the above-mentioned problems, the present inventor has intensively studied to arrive at the present invention.
That is, the first invention is a non-reactive interface with respect to 100 parts by weight of the radically polymerizable unsaturated monomer (A) mainly composed of (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms. Emulsion-type adhesive comprising polymer emulsion (2) obtained by polymerizing monomer emulsion (1) containing 0.05 to 1 part by weight of activator (B) and water and having a 50% particle size of 10 μm or less It relates to the agent.

  The second invention is characterized in that the emulsion-type pressure-sensitive adhesive further comprises inorganic particles (C) and / or pre-crosslinked organic particles (D) having a gel fraction of 99% or more. The present invention relates to an emulsion-type pressure-sensitive adhesive described in the invention.

  In the third invention, the average particle diameter of the inorganic particles (C) and the crosslinked organic particles (D) having a gel fraction of 99% or more is 0.01 to 50 μm, and the true specific gravity is 0.9 to 6. The total amount of (C) and (D) is 100 parts by weight or less based on 100 parts by weight of the dry weight of the polymer emulsion (2). It relates to the agent.

  Furthermore, the fourth invention relates to a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer formed from the emulsion-type pressure-sensitive adhesive according to any one of the first to third inventions is provided on at least one surface of a plastic film substrate.

  Furthermore, the fifth invention relates to the pressure-sensitive adhesive sheet according to the fourth invention, wherein the plastic film substrate is an optical film substrate.

  The present invention provides an emulsion-type pressure-sensitive adhesive that can form an pressure-sensitive adhesive layer with excellent water resistance and less adherend contamination, and can be preferably used for optical film materials, and a pressure-sensitive adhesive sheet using the same. I was able to do it.

  In the present invention, it is important that the radical polymerizable unsaturated monomer (A) used for forming the monomer emulsion (1) is mainly composed of (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms. It is. Examples of the alkyl methacrylate having 1 to 8 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, iso-propyl (meth) acrylate, Examples include butyl (meth) acrylate, iso-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. The alkyl group (meth) acrylic acid alkyl ester having 1 to 8 carbon atoms in the alkyl group is contained in an amount of 70 to 99.9% by weight in a total of 100% by weight of the radical polymerizable unsaturated monomer (A). It is contained above.

In the radically polymerizable unsaturated monomer (A), a carboxyl group-containing monomer or an alcoholic hydroxyl group-containing monomer is used alone or in combination as a polar group-containing monomer. The content is preferably 1 to 20% by weight, more preferably 0.2 to 5% by weight, and still more preferably 0.2 to 2% by weight.
Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic acid, and crotonic acid.
Examples of the alcoholic hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like. It is done.
When the ratio of the total amount of the carboxyl group-containing monomer and the alcoholic hydroxyl group-containing monomer is less than 0.1% by weight, particles that are dispersoids (hereinafter referred to as particles that are dispersoids) constituting the monomer emulsion (1) to be formed. The dispersion state of “emulsion particles” in water tends to be unstable, and the polymerization tends to become unstable. On the other hand, if it exceeds 20% by weight, the adhesion between the emulsion particles is inhibited during drying, and the uniformity of the pressure-sensitive adhesive layer tends to be lowered.

  In addition, as the radically polymerizable unsaturated monomer (A) used in the present invention, monomers other than those described above can be used as necessary. Examples of such monomers include polyethylene glycol (meth) acrylate, glycidyl. Epoxy group-containing monomers such as acrylate and glycidyl methacrylate, N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, methylolated acrylamide, N- (1,1-dimethyl-3oxobutyl) acrylamide, diacetone acrylamide (Meth) acrylamide monomer such as, phosphate group-containing vinyl monomer and vinyl monomers such as vinyl acetate, styrene, butadiene, acetoacetoxyethyl methacrylate, alkoxysilyl group-containing monomer, etc. Can be used in a proportion of a total of 100 wt% 0-10 wt% of radical polymerizable unsaturated monomer (A), can be used alone or in combination.

By the way, an adhesive sheet forms an adhesive layer by apply | coating the adhesive in a liquid state to a sheet-like base material, and drying and removing the liquid medium contained in the adhesive.
In the case of a solvent-type pressure-sensitive adhesive, by removing the liquid medium, the contained polymer component is formed as it is to form a pressure-sensitive adhesive layer. On the other hand, in the case of an emulsion-type pressure-sensitive adhesive, when the liquid medium is removed, the emulsion particles approach, adhere to, and fuse together to form a film. Therefore, in order to improve the uniformity of the pressure-sensitive adhesive layer, it is important to promote the fusion of the emulsion particles. Therefore, it is preferable to use interparticle crosslinking in order to promote fusion between the emulsion particles.
In order to generate interparticle cross-linking, the radical polymerizable unsaturated monomer (A) is preferably used in combination with a monomer having a functional group capable of causing a cross-linking reaction. Among these, it is preferable to use a monomer having a carboxyl group or a hydroxyl group in combination with a monomer having a functional group that can undergo a crosslinking reaction during film formation. These functional groups may have self-crosslinking properties.
Furthermore, the interparticle crosslinking can be generated also by using a crosslinking agent described later.
Monomers that are preferably used to form interparticle crosslinks include epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, methylolated acrylamide, dye Monomers such as (meth) acrylamide monomers such as acetone acrylamide and silane monomers can be exemplified, and in particular, when the adherend is glass or when particles (C) described later are added, adhesion to the glass It is preferable to use a silane monomer for the purpose of improving the property and bonding the polymer and the particles (C).
Examples thereof include 3-methacryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-acryloyloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinyl Butyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxy Sill trimethoxysilane, 10-acryloyloxydecyl trimethoxysilane, 10-methacryloyloxydecyl triethoxysilane, 10-acryloyloxydecyl triethoxysilane and the like.

  In the present invention, when the above-mentioned various radical polymerizable unsaturated monomers (A) are polymerized, the glass transition temperature (Tg) of the obtained polymer is preferably 0 ° C. or lower, and is −10 ° C. or lower. Is more preferable, and it is still more preferable that it is -20 degrees C or less. Even when a polymer emulsion is obtained using a radically polymerizable unsaturated monomer having a glass transition temperature of more than 0 ° C., it is difficult to obtain a pressure-sensitive adhesive having good adhesion performance from such a polymer emulsion. .

Next, the non-reactive surfactant (B) will be described.
In the present invention, the type and amount of the surfactant used are extremely important.
If the mixed solution of the radical polymerizable unsaturated monomer (A) is simply emulsified in an aqueous medium, a so-called reactive surfactant having a radical polymerizable functional group or a non-reactive surfactant having no such functional group Any of the dispersing agents called “acrylic polymer emulsifiers” and “acrylic water-soluble resin dispersants” can be used.
However, in order to obtain a pressure-sensitive adhesive layer with excellent uniformity, it is important to use a non-reactive surfactant (B).

  When polymerizing the radically polymerizable unsaturated monomer (A), a reactive surfactant or a dispersant called “acrylic polymer emulsifier” or “acrylic water-soluble resin dispersant” is used as the radically polymerizable unsaturated monomer (A). It is considered that the reactive surfactant, acrylic polymer emulsifier or acrylic water-soluble resin dispersant that has lost the degree of freedom is immobilized near the surface of the emulsion particles of the polymer emulsion. The emulsion particles are composed of a radically polymerizable unsaturated monomer (A) that is relatively rich in lipophilicity. Therefore, when the emulsion-type pressure-sensitive adhesive is dried and the pressure-sensitive adhesive layer is formed, the hydrophilic part derived from the immobilized surfactant or dispersant is a lipophilic part that occupies most of the emulsion particles because of its hydrophilicity. Is considered to inhibit the fusion of the emulsion particles without affinity. As a result, it is difficult to obtain a pressure-sensitive adhesive layer having excellent uniformity from a pressure-sensitive adhesive containing a polymer surfactant obtained using a reactive surfactant, an acrylic polymer emulsifier, or an acrylic water-soluble resin dispersant.

  On the other hand, when the non-reactive surfactant (B) is used, since the surfactant is present near the surface of the emulsion particles of the polymer emulsion, it is not immobilized. It can move through the membrane in the course of the membrane. That is, since the non-reactive surfactant (B) does not inhibit fusion between the lipophilic emulsion particles, the pressure-sensitive adhesive containing the polymer emulsion obtained by using the non-reactive surfactant (B). Can form a dense and uniform pressure-sensitive adhesive layer. Since the pressure-sensitive adhesive layer is dense and uniform, it has excellent water resistance. Therefore, it is preferable to use a non-reactive surfactant.

  Examples of the non-reactive surfactant (B) used in the present invention include ionic and nonionic surfactants, which can be used alone or in combination.

  Nonionic surfactants among the non-reactive surfactant (B) include polyoxyalkylene alkyl ethers typified by polyoxyethylene alkyl ethers and ether types such as polyoxyalkylene polycyclic phenyl ethers, as well as polytypes. Examples thereof include oxyethylene glyceryl ether fatty acid ester, polyoxyethylene hydrogenated castor oil fatty acid ester, polyoxyethylene trimethylolpropane fatty acid ester, amino acid derivative, polyglycerin fatty acid ester, and silicon surfactant.

  As the ionic surfactant among the non-reactive surfactant (B), an ionic surfactant such as a sulfate ester obtained by anionizing the nonionic surfactant or a salt thereof can be used.

It is important that the amount of the non-reactive surfactant (B) used is 0.05 to 1 part by weight with respect to 100 parts by weight of the total amount of the radical polymerizable unsaturated monomer (A). The amount is preferably 0.8 part by weight, and more preferably 0.1 to 0.5 part by weight. When the non-reactive surfactant (B) is less than 0.05 parts by weight, the stability of the monomer emulsion itself is poor, and the radically polymerizable unsaturated monomer (A) layer and the aqueous layer are easily separated. If a monomer emulsion having poor dispersion stability is to be polymerized, the polymerization will also become unstable and a large amount of aggregates will be generated.
On the other hand, when the amount of the non-reactive surfactant (B) exceeds 1 part by weight, an excessive amount of the non-reactive surfactant (B) is reduced between the emulsion particles when the resulting acrylic polymer emulsion is dried. It tends to inhibit fusion and reduce the uniformity of the pressure-sensitive adhesive layer.
In the present invention, a part of the non-reactive surfactant (B) to be used may be added in advance to the polymerization vessel in order to control the emulsion particle size.
Further, in the present invention, it is important to use the non-reactive surfactant (B). However, the reactive surfactant may be used as necessary within a range that does not impair the transparency and water resistance of the obtained pressure-sensitive adhesive layer. Alternatively, “acrylic polymer emulsifier” or “acrylic water-soluble resin dispersant” may be used.

It is important that the monomer emulsion (1) containing the radical polymerizable monomer (A), the specific amount of the non-reactive surfactant (B) and water has a 50% particle size of the emulsion particles of 10 μm or less, It is preferable that it is 0.1-5 micrometers, and it is more preferable that it is 0.1-1 micrometer. By controlling the stirring conditions and the like, the particle diameter of the emulsion particles of the monomer emulsion (1) can be controlled.
In the present invention, “50% particle diameter” refers to the median diameter on a volume basis.

  The present invention can impart stability to a monomer emulsion with a very small amount of use compared to the amount of surfactant used in emulsion polymerization of a conventional adhesive emulsion. When the 50% particle diameter exceeds 10 μm, the radically polymerizable unsaturated monomer (A) layer and the water layer are easily separated, and the monomer emulsion tends to become unstable.

Next, the polymer emulsion (2) of the present invention will be described.
In the polymer emulsion (2), for example, the radical polymerizable monomer (A) is sufficiently mixed, the non-reactive surfactant (B) and water are added to this mixture, and the mixture is stirred and mixed, and if necessary, an ultrasonic emulsifier. Or a homomixer or the like to obtain a monomer emulsion (1) having a 50% particle diameter of 10 μm or less of the emulsion particles, and the monomer emulsion (1) is put into a dropping device.
Then
Water is put into a reaction vessel equipped with heating and stirring means, and the monomer emulsion (1) is dropped into the water to polymerize,
Water and a part of the monomer emulsion (1) are put in a reaction vessel equipped with heating and stirring means, and the remaining monomer emulsion (1) is dropped therein to polymerize,
Water and a non-reactive surfactant (B) can be put into a reaction vessel equipped with heating and stirring means, and the monomer emulsion (1) can be dropped into the aqueous surfactant solution to polymerize.
In the case of the third exemplified method, the amount of the non-reactive surfactant (B) that can be blended in the water in the reaction vessel is an amount that does not decrease the transparency and water resistance of the pressure-sensitive adhesive layer to be formed. It is preferable that the amount of the non-reactive surfactant (B) used for forming the monomer emulsion (1) is 0.05 to 1 weight with respect to 100 parts by weight of the radical polymerizable monomer (A). It is preferable to be a part.

The polymerization initiator used for obtaining the polymer emulsion (2) of the present invention will be described.
As the polymerization initiator, either a water-soluble or water-insoluble one can be used, and a water-soluble polymerization initiator is preferably used. As those generally used, water-soluble thermal decomposition polymerization initiators such as persulfates such as potassium persulfate and ammonium persulfate, azobis cation salts or hydroxyl adducts, and redox initiators can be used. . Redox initiators include combinations of organic peroxides such as t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide and reducing agents such as Rongalite, sodium metabisulfite, or sodium persulfate, ammonium persulfate and Rongalite. , A combination of sodium thiosulfate and the like, a combination of hydrogen peroxide and ascorbic acid, etc. can be used, but when a polymer is crosslinked using a crosslinking agent to be described later, it is possible to obtain a polymer having a small branched structure, Since it is preferable in terms of the uniformity of the pressure-sensitive adhesive layer, it is preferable to use an azo-based initiator rather than a persulfate-based or peroxide-based one.
The amount of the polymerization initiator used is preferably 0.02 to 3 parts by weight and more preferably 0.1 to 1 part by weight with respect to 100 parts by weight of the radical polymerizable unsaturated monomer (A). .
As a method for adding a polymerization initiator, the whole amount is charged in a reaction vessel, the reaction may be started, a part thereof is charged in a reaction vessel, and the remainder may be added in portions or added dropwise. The entire amount may be added in portions or added dropwise. In the case of divided addition or dropwise addition, it may be used in a mixed state with a monomer emulsion.

Further, mercaptan-based, thioglycol-based, and β-mercaptopropionic acid-based alkyl esters can be used as chain transfer agents in order to control the molecular weight and molecular weight distribution of the polymer obtained. When using a chain transfer agent, the addition amount can be used, adjusting molecular weight at 0-0.1 weight part with respect to 100 weight part of radically polymerizable unsaturated monomers (A).
The polymerization reaction for obtaining the polymer emulsion (2) is usually performed in a temperature range of 40 ° C. to 90 ° C. over 2 to 6 hours.

The pressure-sensitive adhesive containing the polymer emulsion (2) of the present invention preferably crosslinks emulsion particles between particles or polymer molecules during drying.
for that purpose,
After radical polymerization of the radically polymerizable unsaturated monomer (A), the radically polymerizable unsaturated monomer (A) is functionalized so that the functional groups derived from the monomer (A) can undergo a crosslinking reaction in the drying process and in the aging process performed as necessary. Select the type of functional group in the saturated monomer (A),
It is preferable to contain a crosslinking agent capable of reacting with the functional group derived from the monomer (A).
For example, when a monomer having an acetoacetoxy group or a silane monomer is used as one of the radically polymerizable unsaturated monomers (A), acrylic polymers constituting the emulsion particles can self-crosslink in the drying process.

  As a crosslinking agent, a compound capable of reacting with a functional group derived from the radically polymerizable unsaturated monomer (A) in the acrylic polymer emulsion (2), such as a hydroxyl group, a carboxyl group, an epoxy group, etc. during the drying process or aging. Can be used. Such a crosslinking agent is not particularly limited as long as it is generally used. Epoxy compounds, hydrazide compounds, semicarbazide derivatives, isocyanate compounds, carbodiimide compounds, aziridine compounds, complexable metals Examples include chelate compounds. When the crosslinking agent is difficult to dissolve or disperse in water, the crosslinking agent may be dissolved in or dispersed in a small amount of a surfactant or solvent.

  Known metal chelate compounds include titanium chelate compounds, aluminum chelate compounds, zirconium chelate compounds and the like.

  The epoxy compound is not particularly limited as long as it is a compound having a plurality of epoxy groups in the molecule. Specific examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A / epichlorohydrin type epoxy resin, N, N , N′N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine and the like. .

  The isocyanate compound includes a known diisocyanate compound, a so-called adduct obtained by modifying a known diisocyanate compound with a trifunctional polyol component, a burette obtained by reacting the diisocyanate compound with water, and an isocyanurate ring formed from three molecules of the diisocyanate compound. Trimers (isocyanurates) and polyisocyanate compounds can be used.

  As the known diisocyanate compound, aromatic diisocyanate, aliphatic diisocyanate, araliphatic diisocyanate, alicyclic diisocyanate and the like can be used, and examples thereof include 1,3-phenylene diisocyanate, trimethylene diisocyanate, ω, ω. '-Diisocyanate-1,3-dimethylbenzene, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and the like.

  As the aziridine compound, a compound having at least two aziridinyl groups in one molecule can be used, and examples thereof include tri-1-aziridinylphosphine oxide, N, N′-hexamethylene-1,6-bis. (1-aziridine carboxyamide), N, N′-diphenylethane-4,4′-bis (1-aziridine carboxyamide), trimethylolpropane-tri-β-aziridinylpropionate, N, N′— Examples include toluene-2,4-bis (aziridinecarboxyamide), bisisophthaloyl-1- (2-methylaziridine) phosphine, and trimethylolpropane-tri-β- (2-methylaziridine) propionate.

  Examples of the hydrazide compound include isophthalic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, thiocarbohydrazide and the like.

  Examples of the semicarbazide derivative include 1,6-hexamethylenebis (N, N-dimethylsemicarbazide), 1,1,1 ′, 1′-tetramethyl-4,4 ′-(methylene-di-para-phenylene) disemicarbazide. 4,4-dimethyl-1-phenyl semicarbazide and the like.

  Examples of the carbodiimide compound include N, N′-dicyclohexylcarbodiimide, N, N′-diisopropylcarbodiimide, N-ethyl-N ′-(3-dimethylaminopropyl) -carbodiimide / hydrochloride, and the like.

  The amount of crosslinking agent used is preferably determined in consideration of the required adhesive properties, but in the drying and aging processes, fusion between emulsion particles and interparticle crosslinking proceed in a competitive manner. it is conceivable that. Therefore, if the interparticle cross-linking proceeds before the fusion between the emulsion particles hardly progresses, it is considered that the cross-linked portion becomes a kind of barrier for the fusion between the emulsion particles. Therefore, it is preferable that the amount of the crosslinking agent is not too large.

An emulsion-type pressure-sensitive adhesive can be obtained by further adding various additives as necessary to the polymer emulsion (2) of the present invention. Specific examples of additives include wetting agents (surfacing prevention surfactants, etc.), antifoaming agents, neutralizing agents, plasticizers, thickeners, colorants, antiseptics, rust inhibitors, solvents, and the like. .
In addition, when adding various additives, it is preferable to disperse the additives well using a homomixer or the like.
In addition, when the additive is water-soluble and non-volatile, it is considered that the adhesive particles are likely to inhibit fusion between the emulsion particles when the pressure-sensitive adhesive is dried, as with the reactive surfactant. It is done. Accordingly, the amount of the water-soluble and non-volatile additive is preferably 3% by weight or less in 100% by weight of the solid content of the emulsion-type pressure-sensitive adhesive.
When it exceeds 3% by weight, the water-soluble additive becomes a fusion barrier between the emulsions when the resulting acrylic polymer emulsion is dried, which is not preferable because the uniformity and water resistance of the pressure-sensitive adhesive layer are lowered.
Furthermore, it is not preferable that the emulsion-type pressure-sensitive adhesive of the present invention contains a tackifying resin that is easily deteriorated by light or heat.

In addition, the emulsion-type pressure-sensitive adhesive obtained in the present invention can be obtained by further containing inorganic particles (C) and / or already crosslinked organic particles (D) having a gel fraction of 99% or more as a light diffusing agent. Light diffusibility can be imparted to the pressure-sensitive adhesive layer.
Examples of inorganic particles (C) that can be used in the present invention include calcium carbonate, iron oxide, calcium carbonate, magnesium oxide, magnesium hydroxide, basic magnesium carbonate, silica powder, hydrotalcite, glass beads, alumina, diatomaceous earth, and zircon oxide. , Synthetic silica, aluminum hydroxide, bentonite, calcium silicate, zeolite, kaolin clay, pyrophyllite (rholite clay), talc, serinite, attapulgite, mica, calcium sulfate, zircon silicate, carbon black, calcium sulfite, acetylene Black, titanium oxide, furnace black, graphite powder, potassium titanate, carbon fiber, barium sulfate, silicon nitride, silicon carbide, barium carbonate, antimony trioxide, barium titanate, molybdenum disulfide, tourmaline, gem Examples thereof include inorganic particles such as rumanium and zinc oxide.

In the present invention, in addition to inorganic particles (C), pre-crosslinked organic particles (D) having a gel fraction of 99% or more can also be used.
In addition, the gel fraction here means the value calculated from the weight change before and after being immersed for 24 hours at room temperature using toluene as an extraction solvent.
When the gel fraction of the crosslinked organic particles is less than 99%, it tends to be dissolved or swelled easily in the pressure-sensitive adhesive, which causes a change in particle diameter and makes the physical properties of the pressure-sensitive adhesive unfavorable.
As such a crosslinked organic particle (D) having a gel fraction of 99% or more, a crosslinked type composed of polyolefin, polystyrene, polycarbonate, urethane resin, acrylic resin, Teflon (registered trademark), fatty acid amide, or the like. Organic particle | grains are mentioned.

In the present invention, the particle size of the particles (C) and (D) is preferably 0.01 to 50 μm, more preferably 0.01 to 30 μm, and still more preferably 0.01 to 20 μm. .
The true specific gravity of the particles is preferably 0.9-6. When the true specific gravity of the particles is smaller than 0.9 or larger than 6, in both cases, the problem of separation of the pressure-sensitive adhesive component other than the particles from the particles tends to occur, and the stability of the pressure-sensitive adhesive decreases.
The total amount of (C) and (D) is preferably 100 parts by weight or less, and 40 parts by weight or less with respect to 100 parts by weight of the dry weight of the polymer emulsion (2). More preferred is 30 parts by weight or less. Moreover, only 1 type may be used for the kind of particle | grains, and 2 or more types may be used together. When the amount of particles used exceeds 100 parts by weight, the light transmittance is lowered.
These various additive components are preferably mixed well into the polymer emulsion (2) using a homomixer or the like.
Thus obtained emulsion type pressure-sensitive adhesive having a light diffusion function can be preferably used for applications such as a light diffusion film for FPD.

A pressure-sensitive adhesive sheet can be obtained by coating the emulsion-type pressure-sensitive adhesive of the present invention on a plastic film substrate and drying it.
In the pressure-sensitive adhesive sheet of the present invention, an emulsion-type pressure-sensitive adhesive is coated on a release paper, dried, and provided with a pressure-sensitive adhesive layer. Then, the pressure-sensitive adhesive layer and the plastic film substrate are bonded together, and the pressure-sensitive adhesive layer is formed into a film base. It can also be obtained by a transfer method on a material, a so-called transfer method.
The method of coating the emulsion-type pressure-sensitive adhesive on the plastic film substrate or release paper is not particularly limited, and includes a roll coater such as a comma coater, a blade coater, and a gravure coater, a slot die coater, a lip coater, and a curtain coater. A conventionally known coating apparatus can be used.
Examples of the plastic film substrate include cellophane and various plastic sheets (polyester film, polycarbonate film, triacetate film, cycloolefin film, polyacrylic film, and other various films). Moreover, various base materials can also be used independently, and the thing in the multilayer state formed by laminating | stacking a several thing can also be used. Further, the surface can be peeled off.

In the present invention, an optical film substrate can be particularly preferably used as the plastic film substrate, and an adhesive sheet for optical applications can be obtained.
In the pressure-sensitive adhesive sheet of the present invention, it is important that the emulsion particles forming the pressure-sensitive adhesive layer have sufficient fusion or cross-linking reaction. Emulsion-type pressure-sensitive adhesives are often dried at around 100 ° C. for several tens of seconds. Under such conditions, when the fusion between the emulsion particles is insufficient, the adhesion of the emulsion particles and the crosslinking reaction can be advanced by further aging the pressure-sensitive adhesive sheet after drying. For example, it is preferable to age for about 25 ° C.-7 days or 40 ° C.-3 days. By aging, the shape of the polymer in the form of particles collapses to form a uniform phase, and a pressure-sensitive adhesive sheet in which the crosslinking reaction is completed is obtained.

The pressure-sensitive adhesive sheet of the present invention thus obtained is excellent in water permeability and has little adherend contamination, and is useful for applications such as optical members such as window films and polarizing plates.
The “base material” in the present invention is intended to include not only a relatively short length but also a long so-called web state.

  Specific examples of the present invention will be described below together with comparative examples, but the present invention is not limited to the following examples. In the following examples and comparative examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively. In addition, the number of ethylene oxide repeating polyethylene oxide is defined as “EO number”.

Example 1
As radical polymerizable unsaturated monomers, 2-ethylhexyl acrylate: 50.5 parts, butyl acrylate: 40.5 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, chain transfer agent Octyl thioglycolate: 0.01 parts were mixed and dissolved to obtain a monomer mixture.
To this mixture, 0.5 parts of polyoxyethylene alkyl ether sulfate having an alkyl carbon number of 12 and an EO number of 18, which is a non-reactive surfactant, and 45.6 parts of deionized water are added and stirred with a homomixer. A monomer emulsion having a% particle size of 0.5 μm was obtained, and the monomer emulsion was charged into a dropping tank.

Deionized water: 46 parts, alkyl carbon number 12 and EO number 18 polyoxyethylene alkyl ether sulfate: 0 in a polymerization vessel equipped with a heating device, stirrer, reflux cooling device, thermometer, nitrogen introduction tube and dropping tank .1 part was charged and stirred under a nitrogen atmosphere to raise the internal temperature to 78 ° C., and 0.065 part of a 5% potassium persulfate aqueous solution was added as a solid content. After 5 minutes, 0.187 parts of the monomer emulsion and 5% aqueous ammonium persulfate aqueous solution as solids were added dropwise from separate dropping tanks over 3 hours for polymerization.
After completion of dropping, the temperature is kept at 80 ° C. for 30 minutes, and then the internal temperature is set to 60 to 65 ° C. over 30 minutes, and t-butyl hydroperoxide: 0.01 part and Rongalite: 0.012 part in a 5% aqueous solution. It was added in 3 portions every 10 minutes. The mixture was further reacted for 1 hour with stirring, neutralized with ammonia water, and filtered through a 175 mesh nylon filter cloth to obtain a polymer emulsion having a nonvolatile content of 49.7%, a viscosity of 220 mPa · s, and a 50% particle size of 150 nm. It was.
In 100 parts of the polymer emulsion obtained above, 0.1 part of antifoaming agent (50% by weight is a water-soluble component), sodium dioctylsulfosuccinate that is water-soluble as a wetting agent: 0.1 part, preservative: 0 Add 3 parts (5% by weight water-soluble component), and add 1 part (30% by weight water-soluble component) thickener to 5000 mPa · s (BL viscometer, # 4 rotor / 60 rpm at 25 ° C.) The emulsion type pressure-sensitive adhesive was obtained. The pressure-sensitive adhesive was prepared with a homomixer.
<50% particle size><Nonvolatilecontent>
The particle size of the monomer emulsion and polymer emulsion was measured by “Microtrack” manufactured by Nikkiso Co., Ltd., and the nonvolatile content was measured by measuring the weight ratio after drying at 150 ° C. for 20 minutes in an electric oven.
The obtained emulsion-type adhesive is coated on a film separator with a doctor blade so that the dry film thickness is 20 μm, dried at 100 ° C. for 75 seconds, and a 50 μm PET film is laminated to prepare a coated product. Aged at 40 ° C. for 3 days to obtain an adhesive sheet.
The water resistance and adherend contamination of the pressure-sensitive adhesive sheet were evaluated by the following methods. The results are listed in Table 1.

<Water resistance evaluation>
Before water immersion: The release sheet was peeled off, a 50 μm PET film was laminated, and haze was measured using an ultraviolet-visible-near infrared spectrophotometer (V-570: manufactured by JASCO Corporation).
After water immersion: The release sheet is peeled off, immersed in water at 25 ° C., left for 24 hours, then taken out, immediately laminated with a 50 μm PET film on the adhesive layer, and an ultraviolet-visible near-infrared spectrophotometer (V-570). : Manufactured by JASCO Corporation). It shows that there are few external appearance changes of an adhesive sheet, so that the change of the haze before and behind water immersion is small.

<Adherent contamination evaluation>
Cut the adhesive sheet into a strip with a width of 20 mm, peel off the release paper, attach it to the glass as the adherend, reciprocate once with a 2 kg roll, and attach it at 300 mm / mm in a 23 ° C. atmosphere after 24 hours. The contact angle of water on the glass surface, which was peeled in the direction of 180 ° at a speed of minutes and the adhesive sheet was adhered, was measured with an automatic contact angle meter (CA-V type: manufactured by Kyowa Interface Science Co., Ltd.).
In addition, the contact angle of the water of the clean glass surface which has not stuck the adhesive sheet was 20 degrees. As this angle increases, it means that the adherend is contaminated.

(Example 2)
In Example 1, the same experiment as in Example 1 was performed except that the aging conditions were changed to 25 ° C.-7 days.

(Example 3)
The same experiment as in Example 1 was performed except that the coated product was not aged.

Example 4
2-ethylhexyl acrylate: 50.4 parts, butyl acrylate: 40.5 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, 3-methacryloxypropyltrimethoxysilane: 0 0.1 part octyl thioglycolate as a chain transfer agent: 0.01 part was mixed and dissolved to obtain a monomer mixture.
Thereafter, the same experiment as in Example 1 was performed.

(Example 5)
2-ethylhexyl acrylate: 50.5 parts, butyl acrylate: 40.5 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, 2-hydroxyethyl methacrylate: 1 part, thio which is a chain transfer agent Octyl glycolate: 0.01 part was mixed and dissolved to obtain a monomer mixture.
To this mixture, 0.5 parts of polyoxyethylene alkyl ether sulfate having an alkyl carbon number of 12 and an EO number of 18, which is a non-reactive surfactant, and 45.6 parts of deionized water are added and stirred with a homomixer. A monomer emulsion having a% particle size of 0.5 μm was obtained, and the monomer emulsion was charged into a dropping tank.

Deionized water: 46 parts, alkyl carbon number 12 and EO number 18 polyoxyethylene alkyl ether sulfate: 0 in a polymerization vessel equipped with a heating device, stirrer, reflux cooling device, thermometer, nitrogen introduction tube and dropping tank .1 part was charged and stirred under a nitrogen atmosphere to raise the internal temperature to 78 ° C., and 0.065 part of a 5% potassium persulfate aqueous solution was added as a solid content. After 5 minutes, 0.187 parts of the monomer emulsion and 5% aqueous ammonium persulfate aqueous solution as solids were added dropwise from separate dropping tanks over 3 hours for polymerization.
After completion of dropping, the temperature is kept at 80 ° C. for 30 minutes, and then the internal temperature is set to 60 to 65 ° C. over 30 minutes, and t-butyl hydroperoxide: 0.01 part and Rongalite: 0.012 part in a 5% aqueous solution. It was added in 3 portions every 10 minutes. The mixture was further reacted for 1 hour with stirring, neutralized with aqueous ammonia, and filtered through a 175 mesh nylon filter cloth to obtain a polymer emulsion having a nonvolatile content of 49.8%, a viscosity of 400 mPa · s, and a 50% particle size of 140 nm. It was.
In 100 parts of the polymer emulsion obtained above, 0.1 part of antifoaming agent (50% by weight is a water-soluble component), sodium dioctylsulfosuccinate that is water-soluble as a wetting agent: 0.1 part, preservative: 0 .3 parts (5% by weight is a water-soluble component), “Takenate WD-725” (manufactured by Mitsui Takeda Chemical Co., Ltd.): 0.5 part (no water-soluble component) as a polyisocyanate-based cross-linking agent, and a thickener 1 part (30% by weight is a water-soluble component) was thickened to 5000 mPa · s (BL type viscometer, measured at 25 ° C. with # 4 rotor / 60 rpm) to obtain an emulsion-type pressure-sensitive adhesive. The pressure-sensitive adhesive was prepared with a homomixer.
Thereafter, the same experiment as in Example 1 was performed.

(Example 6)
Anti-foaming agent: 0.1 part (50% by weight is a water-soluble component), sodium dioctylsulfosuccinate that is water-soluble as a wetting agent: 0.1 part, antiseptic, to 100 parts of the polymer emulsion obtained in Example 4 Agent: 0.3 parts (5% by weight is a water-soluble component), tourmaline particles having an average particle diameter of 3 μm and a true specific gravity of 3.06: 10 parts, and a thickener: 1 part (30% by weight is a water-soluble component) ) To 5000 mPa · s (BL type viscometer, measured at 25 ° C. with # 4 rotor / 60 rpm) to obtain an emulsion type adhesive. The pressure-sensitive adhesive was prepared with a homomixer.
Thereafter, the same experiment as in Example 4 was performed.

(Comparative Example 1)
In Example 1, the 50% particle size of the monomer emulsion was adjusted to 20 μm, but when the stirring was stopped, the monomer layer and the aqueous layer were separated, and the subsequent experiment was stopped.

(Comparative Example 2)
An experiment similar to that of Example 1 was conducted except that the polyoxyethylene alkyl ether sulfate having 12 alkyl carbons and 18 EO, which is a non-reactive surfactant, was changed to 2 parts.

(Comparative Example 3)
Instead of the polyoxyethylene alkyl ether sulfate having 12 alkyl carbon atoms and 18 EO number which is the non-reactive surfactant used in Example 1, polyoxyethylene (EO number: 10) − which is a reactive surfactant The same experiment as in Example 1 was conducted except that 1- (allyloxymethyl) alkyl ether sulfate ammonium salt was used.

(Comparative Example 4)
Lauryl methacrylate: 81 parts, 2-ethylhexyl acrylate: 15 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, octyl thioglycolate as a chain transfer agent: 0.01 part, benzoyl peroxide: 0. 3 parts were mixed and dissolved to obtain a monomer mixture.
To this mixture, 0.5 parts of polyoxyethylene alkyl ether sulfate having an alkyl carbon number of 12 and an EO number of 18, which is a non-reactive surfactant, and 45.6 parts of deionized water are added and stirred with a homomixer. A monomer emulsion having a% particle size of 0.4 μm was obtained.

A polymerization vessel equipped with a heating device, a stirrer, a reflux cooling device, a thermometer, and a nitrogen introduction tube was charged with 46 parts of deionized water and the monomer emulsion obtained above and stirred under a nitrogen atmosphere. 0.25 part of a solid potassium persulfate solution was added as a solid, and the temperature was raised to an internal temperature of 78 ° C. Thereafter, polymerization was carried out over 6 hours.
Next, the internal temperature is lowered to 40 ° C., neutralized with aqueous ammonia, and filtered through a 175 mesh nylon filter cloth to obtain a polymer emulsion having a nonvolatile content of 49.8%, a viscosity of 120 mPa · s, a 50% particle size of 300 nm. It was.
In 100 parts of the polymer emulsion obtained above, 0.1 part of antifoaming agent (50% by weight is a water-soluble component), sodium dioctylsulfosuccinate that is water-soluble as a wetting agent: 0.1 part, preservative: 0 .3 parts (5% by weight of water-soluble component) is added, and thickener: 1 part (30% by weight of water-soluble component) is 5000 mPa · s (BL viscometer, # 4 rotor / 25 rpm at 25 ° C. ) To increase the viscosity to obtain an emulsion-type pressure-sensitive adhesive. The pressure-sensitive adhesive was prepared with a homomixer.
Thereafter, the same experiment as in Example 1 was performed.

Claims (5)

The non-reactive surfactant (B) is added to 0.1 parts by weight with respect to 100 parts by weight of the radical polymerizable unsaturated monomer (A) mainly composed of an alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms. An emulsion-type pressure-sensitive adhesive comprising a polymer emulsion (2) obtained by polymerizing a monomer emulsion (1) containing 50 to 1 part by weight and water and having a 50% particle size of 10 μm or less. The emulsion-type pressure-sensitive adhesive according to claim 1, wherein the emulsion-type pressure-sensitive adhesive further comprises inorganic particles (C) and / or pre-crosslinked organic particles (D) having a gel fraction of 99% or more. The inorganic particles (C) and the crosslinked organic particles (D) having a gel fraction of 99% or more have an average particle diameter of 0.01 to 50 μm and a true specific gravity of 0.9 to 6, and (C) and (D) The emulsion-type pressure-sensitive adhesive according to claim 1 or 2, wherein the total amount thereof is 100 parts by weight or less with respect to 100 parts by weight of the dry weight of the polymer emulsion (2). A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the emulsion-type pressure-sensitive adhesive according to claim 1 on at least one surface of a plastic film substrate. The pressure-sensitive adhesive sheet according to claim 4, wherein the plastic film substrate is an optical film substrate.