JP2007224187A - Emulsion type pressure-sensitive adhesive and pressure-sensitive adhesive sheet using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emulsion type pressure-sensitive adhesive forming a pressure-sensitive adhesive layer having high light diffusivity, and hardly changing the light diffusivity with time under heating; and to provide a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed out of the adhesive. <P>SOLUTION: The emulsion type pressure-sensitive adhesive contains (2) a polymer emulsion obtained by polymerizing (1) a monomer emulsion having ≤2 μm of 50% particle diameter, and containing (A) a radically polymerizable unsaturated monomer forming a polymer having ≤0°C glass transition temperature, consisting essentially of an alkyl (meth)acrylate and containing a silane-based monomer, (B) a nonreactive surfactant, and water, and (C) inorganic particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

 The present invention relates to an emulsion-type pressure-sensitive adhesive. Specifically, the present invention relates to an emulsion-type pressure-sensitive adhesive that can form a pressure-sensitive adhesive layer having high light diffusibility and little change in light diffusibility with heating. Furthermore, this invention relates to the adhesive sheet in which the adhesive layer formed from the said emulsion type adhesive is provided.

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 rear projection display (RPJ), an EL display, and a light emitting diode display.
Among these display devices, LCDs and RPJs are provided with a light diffusion layer for diffusing light from an internal light source.
In addition to the display device, a light diffusion sheet is used, and examples thereof include a blindfold sheet for decorating glass indoors and outdoors.
The mainstream of these light diffusion sheets is one in which fine particles that diffuse light are kneaded into a sheet-like base material. However, it has been studied to include light diffusing fine particles in a pressure-sensitive adhesive that can be easily manufactured and processed.

Various films used for display devices and the like are used by being stuck to an adherend with an adhesive. In the above applications, it is placed under high humidity or exposed to cold or hot water, but even under such circumstances, it is required that there is no change in appearance, and the moisture resistance and heat resistance of the adhesive layer are required. Required. Therefore, a solvent-type pressure-sensitive adhesive mainly composed of an acrylic resin having excellent weather resistance has been used more favorably than before.
By the way, since the light diffusing sheet is used for a long time in a high temperature atmosphere, if the light diffusing fine particles are present in the pressure-sensitive adhesive layer that is originally a soft material, the uneven distribution of the fine particles occurs with the passage of time. There was a problem that the diffusibility was lowered.

Furthermore, in recent years, from the viewpoints of protecting the global environment (suppressing volatile organic compound emissions), improving the work environment, and effectively using resources, the use of water-based emulsion adhesives has been studied as an alternative to solvent-based adhesives.
None

 The present invention is provided with an emulsion-type pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having high light diffusibility and little change in light diffusibility with heating, and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive. It aims at providing an adhesive sheet.

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 radically polymerizable unsaturated monomer (A) containing a (meth) acrylic acid ester as a main component and containing a silane monomer, which can form a polymer having a glass transition temperature of 0 ° C. or less. A polymer emulsion (2) obtained by polymerizing a monomer emulsion (1) containing a reactive surfactant (B) and water and having a 50% particle size of 2 μm or less, and inorganic particles (C) It is related with the emulsion-type adhesive which comprises.

 The second invention is characterized in that the monomer emulsion (1) contains 3 to 30 parts by weight of a tackifier resin (D) with respect to 100 parts by weight of the radical polymerizable unsaturated monomer (A). The present invention relates to an emulsion-type pressure-sensitive adhesive described in the first invention.

 The third invention relates to the emulsion-type pressure-sensitive adhesive according to the first or second invention, wherein the emulsion-type pressure-sensitive adhesive further contains a silane compound (E).

 Moreover, 4th invention is the average particle diameter of inorganic particle | grains (C) 0.01-50 micrometers, true specific gravity is 0.9-6, and the quantity of inorganic particle | grains (C) is the drying of a polymer emulsion (2). The present invention relates to the emulsion-type pressure-sensitive adhesive according to any one of the first to third inventions, which is 0.1 to 50 parts by weight with respect to 100 parts by weight.

 Furthermore, the fifth 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 fourth inventions is provided on at least one surface of a sheet-like substrate.

 Furthermore, the sixth invention relates to the pressure-sensitive adhesive sheet according to the fifth invention, wherein the sheet-like substrate is a plastic film substrate.

 According to the present invention, an emulsion-type pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having high light diffusibility and little change in light diffusibility with heating, and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive are provided. An adhesive sheet can be provided.

 In the present invention, the radically polymerizable unsaturated monomer (A) used for forming the monomer emulsion (1) preferably contains (meth) acrylic acid alkyl ester as a main component. Such alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, iso-propyl (meth) acrylate, butyl (meth) acrylate, (meth) Linear or branched aliphatic such as iso-butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate Examples include acrylate esters of alcohol and the corresponding methacrylate esters. The alkyl group of the (meth) acrylic acid alkyl ester used preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 2-ethylhexyl acrylate as a main component. . The (meth) acrylic acid alkyl ester is contained in 69 to 99.895% by weight in a total of 100% by weight of the radical polymerizable unsaturated monomer (A), and is contained in one or more kinds.

In the radically polymerizable unsaturated monomer (A), a carboxyl group-containing monomer and / or an alcoholic hydroxyl group-containing monomer is used alone or in combination as a polar group-containing monomer, and the radically polymerizable unsaturated monomer (A) is 100% by weight in total. The content is preferably 0.1 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 proportion of the total amount of the carboxyl group-containing monomer and / or alcoholic hydroxyl group-containing monomer is less than 0.1% by weight, particles (hereinafter referred to as dispersoid) constituting the monomer emulsion (1) to be formed. The particles are referred to as “emulsion particles”) and the dispersion state 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 radical polymerizable unsaturated monomer 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 acrylate, glycidyl. Epoxy group-containing monomers such as methacrylate, N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, methylolated acrylamide, N- (1,1-dimethyl-3oxobutyl) acrylamide, diacetone acrylamide and the like ( (Meth) acrylamide monomers, vinyl monomers containing phosphate groups, vinyl monomers such as vinyl acetate, styrene and butadiene, acetoacetoxyethyl methacrylate, etc., and a total of 10 radical polymerizable unsaturated monomers Can be used in a proportion by weight% 0-10 wt%, it 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 suitably used to generate interparticle crosslinks include epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, and methylolated acrylamide. Monomers can be exemplified.
The present invention relates to a pressure-sensitive adhesive containing light diffusing particles, which can be preferably used for the production of a pressure-sensitive adhesive sheet with little change in light diffusibility with heating. The light diffusion sheet is used for display devices and indoor / outdoor glass, and is usually stuck to a vertical surface and exposed to a high temperature state for a long time. Therefore, when the light diffusing particles are contained in the pressure-sensitive adhesive layer that is a soft material, the light diffusing particles gradually move in the pressure-sensitive adhesive layer and become unevenly distributed, and the light diffusibility of the light diffusing sheet is increased. It is easy to cause a problem of lowering. In the present invention, a crosslinking reaction is formed between the light diffusing particles and the polymer forming the pressure-sensitive adhesive layer, and the movement of the particles is not caused in the pressure-sensitive adhesive layer.
In order to form a crosslinking reaction between such particles and a polymer, it is important to use a silane compound monomer as the radical polymerizable unsaturated monomer (A).
Examples of silane monomers that can be used in the present invention include 3-methacryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloyloxypropyltriethoxysilane, 3 -Methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-acryloyloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinyl Butyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltri And monomers having an alkoxysilyl group, such as toxisilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and the like. The radical polymerizable unsaturated monomer (A) can be used at a ratio of 0.005 to 1% by weight in a total of 100% by weight, and can be used alone or in combination of two or more.
By adding these silane monomers at the time of blending the pressure-sensitive adhesive, further effects can be obtained.

In the present invention, when the above-mentioned various radical polymerizable unsaturated monomers (A) are polymerized, it is important that the glass transition temperature (Tg) of the obtained polymer is 0 ° C. or lower, and −10 ° C. or lower. It is preferable that it is -20 degreeC 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 from such a polymer emulsion.
The glass transition temperature of a polymer obtained by polymerizing a radical polymerizable unsaturated monomer can be calculated by a known theoretical formula.

Next, the tackifier resin (D) will be described.
In the present invention, the tackifying resin (D) is used in an amount of 3 to 30 parts by weight with respect to a total of 100 parts by weight of the radical polymerizable unsaturated monomer (A) depending on the adhesive force required for the pressure-sensitive adhesive sheet. be able to.
When the amount of the tackifier resin (D) is less than 3 parts by weight, the resulting adhesive layer is not sufficiently improved in adhesive strength, whereas when it exceeds 30 parts by weight, the adhesive layer becomes too soft, The light diffusible particles are likely to be unevenly distributed, and the light diffusibility of the pressure-sensitive adhesive sheet tends to decrease with time.
Examples of the tackifier resin (D) include natural rosin, rosin ester, hydrogenated rosin, hydrogenated rosin ester, polymerized rosin, polymerized rosin ester, disproportionated rosin, disproportionated rosin ester, α-pinene resin, β-pinene. Examples of aromatic petroleum resins such as resins, terpene phenol resins, hydrogenated terpene phenol resins, and the like include styrene oligomers, α-methylstyrene / styrene copolymers, and the light diffusion sheet requires weather resistance. Hydrogenated or disproportionated tackifying resins are preferred.

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 dispersants, called “acrylic polymer emulsifiers” and “acrylic water-soluble resin dispersants” can be used.
However, in order to obtain a pressure-sensitive adhesive layer having excellent uniformity, it is important to use a non-reactive surfactant.

  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.

  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.

The amount of the non-reactive surfactant (B) used is preferably 0.05 to 2 parts by weight, preferably 0.1 to 1 part by weight based on 100 parts by weight of the radical polymerizable unsaturated monomer (A). More preferably, it is 0.1 to 0.8 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 2 parts by weight, an excessive amount of the non-reactive surfactant (B) is fused between the emulsion particles when the resulting polymer emulsion is dried. It tends to inhibit 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.

The monomer emulsion (1) containing the radical polymerizable monomer (A), the non-reactive surfactant (B) and water preferably has a 50% particle size of emulsion particles of 2 μm or less, preferably 0.1 to 1 μm. It is more preferable that 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.

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. Using a dispersing machine such as a homomixer, a monomer emulsion (1) having a 50% particle diameter of preferably 2 μm or less is obtained, 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.

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 functional groups derived from the monomer (A) are radically polymerizable so that they can undergo a crosslinking reaction in the drying process and the aging process performed as necessary. Select the type of functional group in the unsaturated 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 or dispersed in a small amount of surfactant or solvent and added.
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. A trimer (isocyanurate) can be used.

  As the known diisocyanate compound, aromatic diisocyanate, aliphatic diisocyanate, araliphatic diisocyanate, alicyclic diisocyanate and the like can be used. 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.
Further, when the additive is water-soluble and non-volatile, similarly to the reactive surfactant, it is easy to inhibit the fusion of the emulsion particles when the pressure-sensitive adhesive is dried. Therefore, the water-soluble additive is preferably 3% by weight or less in 100% by weight of the solid content of the emulsion-type pressure-sensitive adhesive.
If it exceeds 3% by weight, the water resistance of the pressure-sensitive adhesive layer is lowered, which is not preferable for use as a light diffusion sheet.

In the emulsion-type pressure-sensitive adhesive of the present invention, it is important to use inorganic particles (C) as a light diffusing agent.
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 addition to the inorganic particles (C), the gel fraction having a functional group capable of reacting with an alkoxysilyl group of a silane monomer in the emulsion-type pressure-sensitive adhesive or a silane compound (E) described later is 99% or more. Pre-crosslinked organic particles can also be used in combination.

The average particle diameter of the inorganic particles (C) is preferably 0.01 to 50 μm, more preferably 0.01 to 30 μm, and further preferably 0.01 to 20 μm.
When the average particle diameter is less than 0.01 μm, the light diffusion intensity decreases. On the other hand, when it exceeds 50 μm, problems such as difficulty in setting the thickness of the pressure-sensitive adhesive layer occur.
The true specific gravity of the inorganic particles (C) is preferably 0.9-6. When the true specific gravity of the particles is smaller than 0.9 or larger than 6, both of the adhesive components other than the inorganic particles (C) and the inorganic particles (C) are likely to be separated. Stability is reduced.
Moreover, it is preferable that the usage-amount of inorganic particle (C) is 0.1-50 weight part with respect to 100 weight part of dry weights of a polymer emulsion (2), and it is more preferable that it is 5-30 weight part. .
When the amount is less than 0.1 part by weight, the light diffusion performance is lowered. On the other hand, when the amount exceeds 50 parts by weight, the adhesive force is likely to be lowered.

In the emulsion-type pressure-sensitive adhesive of the present invention, it is preferable to contain a silane compound (E) in order to further fix the inorganic particles (C) in the pressure-sensitive adhesive layer.
Examples of the silane compound (E) include 3-glycidoxypropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane, and N- (2-aminoethyl) 3-aminopropyltrimethoxysilane. 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N N-bis (3- (trimethoxysilyl) propyl) ethylenediamine or the like can be used.
Furthermore, in addition to these, the silane monomer which can be used as the radically polymerizable unsaturated monomer (A) already exemplified can also be used.
These various additive components are preferably mixed well into the polymer emulsion (2) using a homomixer or the like.

A pressure-sensitive adhesive sheet can be obtained by coating the emulsion-type pressure-sensitive adhesive of the present invention on a sheet-like substrate and drying it.
The pressure-sensitive adhesive sheet of the present invention is also coated with an emulsion-type pressure-sensitive adhesive on a film separator or 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, Can also be obtained by a method of transferring the material onto a sheet-like substrate, a so-called transfer method.
The method of coating the emulsion-type pressure-sensitive adhesive on the sheet-like substrate, film separator or release paper is not particularly limited, and roll coaters such as comma coaters, blade coaters, gravure coaters, slot die coaters, lip coaters, curtains. A conventionally known coating apparatus such as a coater can be used.

In the present invention, it is preferable to use a plastic film substrate as the sheet-like substrate.
Examples of the plastic film substrate include cellophane and various plastic films (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.
Furthermore, in the present invention, an optical plastic film can be particularly preferably used as the plastic film substrate, and an adhesive sheet for optical applications can be obtained.
Since the pressure-sensitive adhesive sheet of the present invention has little change in light diffusibility with heating, it is useful for applications such as window films and optical members.
In addition, the base material as used in the field of this invention means not only the thing of comparatively short length but the thing of what is called a web state of elongate shape.

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. Further, the number of ethylene oxide repeats in one molecule is defined as “EO number”.
Example 1
2-ethylhexyl acrylate: 50.4 parts, butyl acrylate: 40.5 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, 3-methacryloyloxypropyltrimethoxysilane: 0 0.1 part octyl thioglycolate as a chain transfer agent: 0.01 part was mixed and dissolved to obtain a monomer mixture.
To this mixture, 0.8 part 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 46.2 parts of deionized water are added and stirred with a homomixer. A monomer emulsion having a% particle diameter of 1 μm was obtained, and the monomer emulsion was charged into a dropping tank.
In addition, the glass transition temperature calculated | required theoretically of the polymer obtained from the composition of the said radically polymerizable monomer is -57.3 degreeC.

Polymerization vessel equipped with heating device, stirrer, reflux cooling device, thermometer, nitrogen introduction tube and dropping tank deionized water: 44.6 parts, polyoxyethylene alkyl ether sulfate with 12 alkyl carbons and 18 EO : 0.1 part was charged, stirred in a nitrogen atmosphere and heated to an internal temperature of 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 240 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), hydrous magnesium silicate as inorganic particles (trade name: “High Filler # 5000PJ”, average particle size 1.8-2.8 μm, manufactured by Matsumura Sangyo Co., Ltd.): 10% Part and further thickening agent: 1 part (30% by weight is a water-soluble component), thickened to 5000 mPa · s (measured at BL type viscometer, # 4 rotor / 60 rpm at 25 ° C.), emulsion type An 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.
Remove the release sheet, attach it to glass, and make two reciprocations with a 2kg roll, and prepare two pieces. One is 23 ° C-50RH%, and the other is aged at 90 ° C for 1000 hours. Thus, a measurement sample was obtained.
The light diffusing ability of the pressure-sensitive adhesive sheet was evaluated by the following method. The results are listed in Table 1.

<Evaluation of light diffusion ability>
The haze was measured for the measurement sample obtained above using an ultraviolet-visible near-infrared spectrophotometer (V-570: manufactured by JASCO Corporation).
A higher haze indicates a higher light diffusion capacity.

(Example 2)
In 100 parts of the polymer emulsion obtained in Example 1, 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, antiseptic Agent: 0.3 parts (5% by weight is a water-soluble component), hydrous magnesium silicate as inorganic particles (trade name: “High Filler # 5000PJ”, average particle size 1.8-2.8 μm, manufactured by Matsumura Sangyo Co., Ltd.) : 10 parts by weight and 0.01 part of 3-glycidoxypropyltrimethoxysilane as a silane compound, and further thickener: 1 part (30% by weight is a water-soluble component) is 5000 mPa · s (BL type) Viscometer, measured at 25 ° C. with # 4 rotor / 60 rpm.) To give an emulsion type adhesive. The pressure-sensitive adhesive was prepared with a homomixer.
Thereafter, the same experiment as in Example 1 was performed.

(Example 3)
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 .1 part, Octyl thioglycolate as a chain transfer agent: 0.01 part, “KE-311” as a hydrogenated rosin ester (manufactured by Arakawa Chemical Co., Ltd.): 5 parts are mixed and dissolved to adhere to the monomer A mixture of imparting resins was obtained.
To this mixture, 0.8 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 48.8 parts of deionized water are added and stirred with a homomixer. A monomer emulsion having a% particle diameter of 1 μm was obtained, and the monomer emulsion was charged into a dropping tank.
In addition, the glass transition temperature calculated | required theoretically of the polymer obtained from the composition of the said radically polymerizable monomer is -57.3 degreeC.
Thereafter, the same experiment as in Example 1 was performed.

(Comparative Example 1)
The same experiment as in Example 1 was performed except that the composition of the radical polymerizable unsaturated monomer and the chain transfer agent in Example 1 was changed as follows.
2-ethylhexyl acrylate: 50.5 parts, butyl acrylate: 40.5 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, octyl thioglycolate as a chain transfer agent: 0.01 parts.

(Comparative Example 2)
2-ethylhexyl acrylate: 50.3 parts, butyl acrylate: 40.5 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, diacetone acrylamide: 0.2 part, chain Octyl thioglycolate as a transfer agent: 0.01 part was mixed and dissolved to obtain a monomer mixture.
To this mixture, 0.8 part 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 46.2 parts of deionized water are added and stirred with a homomixer. A monomer emulsion having a% particle diameter of 1 μm was obtained, and the monomer emulsion was charged into a dropping tank.
In addition, the glass transition temperature calculated | required theoretically of the polymer obtained from the composition of the said radically polymerizable monomer is -57.3 degreeC.

Polymerization vessel equipped with heating device, stirrer, reflux cooling device, thermometer, nitrogen introduction tube and dropping tank deionized water: 44.6 parts, polyoxyethylene alkyl ether sulfate with 12 alkyl carbons and 18 EO : 0.1 part was charged, stirred in a nitrogen atmosphere and heated to an internal temperature of 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 240 mPa · s, and a 50% particle size of 140 nm. It was.
To 100 parts of the polymer emulsion obtained above, 0.1 part of an antifoaming agent (50% by weight is a water-soluble component) and 0.1 part of adipic acid dihydrazide as a crosslinking agent are added in a 10% aqueous solution, and a wetting agent is added. Sodium dioctylsulfosuccinate, which is water-soluble as: 0.1 part, preservative: 0.3 part (5% by weight is a water-soluble component), hydrous magnesium silicate as inorganic particles (trade name: “High Filler # 5000PJ”, Average particle size 1.8 to 2.8 μm, manufactured by Matsumura Sangyo Co., Ltd.): 10 parts by weight, and further thickener: 1 part (30% by weight is a water-soluble component) 5000 mPa · s (BL viscometer, (Measured at # 4 rotor / 60 rpm at 25 ° C.)) 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.

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

The pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer formed from the emulsion-type pressure-sensitive adhesive obtained by the present invention has little change in light diffusibility even when heated and is excellent in heat resistance.

Claims (6)

A radically polymerizable unsaturated monomer (A) comprising a (meth) acrylic acid ester as a main component and containing a silane monomer, which can form a polymer having a glass transition temperature of 0 ° C. or lower, and a non-reactive surfactant (B) And an emulsion-type pressure-sensitive adhesive comprising a polymer emulsion (2) obtained by polymerizing a monomer emulsion (1) having a 50% particle diameter of 2 μm or less, and inorganic particles (C). The emulsion-type pressure-sensitive adhesive according to claim 1, wherein the monomer emulsion (1) contains 3 to 30 parts by weight of a tackifying resin (D) with respect to 100 parts by weight of the radical polymerizable unsaturated monomer (A). . The emulsion-type pressure-sensitive adhesive according to claim 1 or 2, wherein the emulsion-type pressure-sensitive adhesive further contains a silane compound (E). The average particle diameter of the inorganic particles (C) is 0.01 to 50 μm, the true specific gravity is 0.9 to 6, and the amount of the inorganic particles (C) is 0 with respect to 100 parts by weight of the dry weight of the polymer emulsion (2). The emulsion-type pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the amount is from 1 to 50 parts by weight. 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 sheet-like substrate. The pressure-sensitive adhesive sheet according to claim 5, wherein the sheet-like substrate is a plastic film substrate.