JP4906035B2 - Aqueous pressure-sensitive adhesive composition and method for producing pressure-sensitive adhesive sheet using the same - Google Patents

Description

The present invention is usually produced by emulsion polymerization or the like, and the adhesive microsphere particles (A) having an average particle size of 1 μm or more produced by suspension polymerization or the like, mainly as a binder for the adhesive microsphere particles. An aqueous pressure-sensitive adhesive comprising fine particles (B) having an average particle diameter of less than 1 μm and a viscosity modifier (C) for increasing the viscosity of the dispersion liquid of these particles and maintaining the viscosity at an appropriate level In the composition, the adhesive fine sphere particles (A) are at least one kind of high melting point fine spherical particles (A ₁ ) having a melting temperature higher than 60 ° C. and low melting point fine spherical particles (A) having a melting temperature of 60 ° C. or less. ₂ ) Pressure-sensitive adhesive comprising at least one kind, and the viscosity modifier is composed of at least one kind of ionic viscosity modifier (C ₁ ) and nonionic viscosity modifier (C ₂ ). Agent composition and pressure-sensitive adhesive sheet using the same Granulation method, and a pressure-sensitive adhesive sheet which is produced by such compositions and methods.

  In particular, in the present invention, the obtained pressure-sensitive adhesive sheet is an adherend such as paper, metal, or plastic, and the surface thereof has a good adhesion to any adherend having a smooth surface or a rough surface. When this pressure-sensitive adhesive sheet is used as a pressure-sensitive adhesive label, the pressure-sensitive adhesive component remains on the adherend when it is peeled off (hereinafter, sometimes referred to as “glue residue”) and can be peeled off again. And a method for producing a pressure-sensitive adhesive sheet using such a re-peelable pressure-sensitive adhesive composition, and such The present invention relates to a re-peelable pressure-sensitive adhesive sheet produced by the composition and method.

  The pressure-sensitive adhesive sheet is printed as an adhesive label for product labels, logistics management labels, etc., printed and printed with information on various trademarks, prices, precautions, etc., or designs, etc. Often used. In this case, the purpose of applying the label is to display information, design, etc., and the required quality of the pressure-sensitive adhesive composition is easily adhered to the adherend at the time of applying the label, and the subsequent processes such as storage and transportation However, it has sufficient adhesion to prevent the label from falling off, and its use (for example, pressure sensitive adhesive for cold food with excellent adhesion at low temperatures, rough surfaces such as cardboard and concrete, pressure sensitive adhesive sheets such as polyolefin, etc. It is used properly according to the pressure sensitive adhesive having strong adhesion to non-polar adherends and the like, and the label once attached is permanently or semi-permanently adhered.

  The sticking of the pressure-sensitive adhesive label to the adherend here varies depending on the number of the labels to be stuck and the work process, but is performed using an apparatus such as a manual work or an auto labeler. At this time, the contact pressure with the adherend applied to the label is a wide range of 100 g weight to 2 kg weight in terms of the weight of the pressure roller according to the adhesive strength measurement method of JIS Z-0237, and JIS Z-0237 The pressure roller of 2 kg weight according to the adhesive strength measurement method of the above provides a sufficient contact area between the pressure-sensitive adhesive layer surface of the label and the adherend, but a contact pressure of 100 g weight provides a sufficient contact area. Because it is not possible, the label is easy to fall off when sticking. In general, since most adhesive labels have a flat adhesive surface, the adherend to which the label is applied is rough or the contact pressure with the adherend applied to the label is too low. In some cases, a sufficient contact area between the pressure-sensitive adhesive surface of the label and the adherend cannot be ensured, resulting in a low adhesive force, and the label is likely to fall off.

  For the purpose of reusing products and packaging, containers used for packing, wrapping paper, etc., and for distribution management, remove the adhesive label once applied from the adherend, or remove the label once removed. There is a use to stick it again. The required quality of these labels for the pressure-sensitive adhesive composition requires removability and restickability in addition to the adhesiveness.

  As such a re-peelable pressure-sensitive adhesive composition having adhesiveness, re-peelability, and re-adhesiveness, a number of acrylic copolymer or rubber copolymer organic solvent solutions or Pressure-sensitive adhesives based on aqueous emulsion dispersions have been proposed, but the re-peelable pressure-sensitive adhesive sheet obtained from these has a smoothness because the pressure-sensitive adhesive layer is flat. Although the contact area is easy to obtain on the adherend and there is no problem such as dropping of the pressure-sensitive adhesive sheet, the adhesive force increases with the elapsed time after sticking, the base material of the pressure-sensitive adhesive sheet is broken, the adhesive remains, etc. Tends to occur and re-peeling becomes difficult. Conversely, for adherends with rough surfaces such as cardboard and concrete, the contact area with the pressure-sensitive adhesive layer surface is not sufficient, resulting in low adhesion and light pressure bonding such as auto labelers. Under certain conditions, the pressure-sensitive adhesive sheet tends to fall off. For this reason, in order to obtain removability, there was a problem that the type of adherend and the pasting period had to be limited.

  In order to improve such problems, attempts have been made to include unevenness on the surface of the pressure-sensitive adhesive layer by including sticky microsphere particles in the pressure-sensitive adhesive layer. For example, Patent Document 1 proposes a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer composed of a binder and “elastomeric copolymer microspheres” embedded therein. Here, the “elastomeric copolymer microsphere” specifically refers to isooctyl acrylate or the like using an oil-soluble polymerization initiator such as benzoyl peroxide in water in the presence of an anionic surfactant. Adhesive microsphere particles of about 10 to 150 μm obtained by copolymerizing the main adhesive copolymer-forming monomer, and the “binder” is itself used as a pressure-sensitive adhesive It is composed of an aqueous copolymer dispersion or a film derived from an aqueous copolymer dispersion forming a harder film, an epoxy resin film, a cellulose resin film, a urethane resin film, and the like. The method of embedding adhesive microsphere particles is also a method of coating a dispersion containing adhesive microsphere particles after forming a binder film on a substrate, a solution or dispersion of the binder and adhesive microspheres. For example, a method of coating a mixed solution with a dispersion containing particles on a substrate is mentioned.

  Further, in Patent Document 2, a layer of “adhesive microparticles” is formed on a substrate directly or through an undercoat layer in order to obtain removability to various adherends, especially paper products such as paper or fabric. Proposed pressure sensitive adhesive sheets have been proposed. The “adhesive microparticles” used here are obtained by copolymerizing monomers mainly composed of 2-ethylhexyl acrylate, butyl acrylate, etc. in an organic solvent using an oil-soluble polymerization initiator, Alternatively, it is obtained by adding and stirring an aqueous solution containing an oil-soluble nonionic surfactant or the like to obtain an aqueous suspension, and its particle size is preferably about 10 to 100 μm. . The undercoat layer is formed of acrylic resin, saturated polyester resin, polybutyral resin, epoxy resin, or the like.

  In the method described in Patent Document 1 and Patent Document 2 described above, the pressure-sensitive adhesive layer surface is uneven because the adhesive microsphere particles protrude from the surface of the pressure-sensitive adhesive layer. It is possible to reduce the contact (adhesion) area between the easy-to-smooth adherend and the pressure-sensitive adhesive. On the other hand, it is presumed that the unevenness of the pressure-sensitive adhesive layer surface increases the contact (adhesion) area on the rough adherend that is difficult to adhere. Therefore, it can be inferred that the obtained re-peelable pressure-sensitive adhesive sheet can easily obtain a constant contact area regardless of the roughness of the adherend, and can maintain an adhesive force that allows re-peeling and re-sticking. However, the shape of the adhesive microsphere particles is not necessarily stable with respect to pressure. For example, when the pressure-sensitive adhesive sheet is stored in a wound state, the adhesive microsphere particles are removed by the tightening pressure. When the particles are flattened (the hemispherical or spherical sticky microsphere particles are plastically deformed into a flat shape by pressure), the unevenness of the pressure-sensitive adhesive layer surface is reduced, and light pressure bonding to rough surfaces such as cardboard There was a problem that the adhesive strength of the sheet was lowered.

  For this reason, as a means for preventing the flattening of the adhesive microsphere particles due to the external pressure, a method of crosslinking the adhesive microsphere particles has been proposed. For example, Patent Document 3 is prepared by the same method as Patent Document 2. A method of cross-linking adhesive microsphere particles with metal ions such as calcium; Patent Document 4 uses a polyfunctional monomer such as tetraallyloxyethane together with an acrylic monomer that forms an adhesive copolymer. A method of producing “adhesive microspheres” which are suspension-polymerized in an aqueous medium and internally crosslinked; in Patent Document 5, the adhesive microspheres of an adhesive copolymer prepared by the same method as Patent Document 2 Adhesive microspheres obtained by suspension polymerization in particles or an aqueous medium are cross-linked with an oil-soluble cross-linking agent such as epoxy resin, butyl or melamine resin in an aqueous suspension to form an adhesive How to make a coalesced microsphere; It is draft.

  However, since these all increase the hardness of the adhesive microsphere particles by crosslinking the particles themselves, there is an effect of preventing flattening due to external pressure, but the adhesiveness of the adhesive microsphere particles decreases, Adhesiveness to nonpolar adherends such as polyethylene is reduced. Accordingly, there is a drawback that the adhesiveness, which is the inherent performance required for the pressure-sensitive adhesive, becomes insufficient.

  On the other hand, in Patent Document 6, a group that reacts with a functional group such as a carboxyl group contained in an adhesive microsphere particle and a binder for fixing the adhesive microsphere particle to a substrate for improving removability. A label is attached by adding two or more cross-linking agents in one molecule and improving both the adhesion between the adhesive microsphere particles and the binder and the adhesion to the base material by the chemical bonding effect. There has been proposed a method for suppressing adhesive residue when peeled off from the body. The binder is usually obtained by emulsion polymerization of an acrylic monomer. However, even with this method, adhesive residue may occur over time under environmental conditions such as high temperature and high humidity or excessive pressure, and re-peelability under severe conditions is insufficient.

  Patent Document 7 discloses that a functional group is bonded to each molecule of a copolymer that is an “elastic microsphere” and an adhesive copolymer that covers the entire surface of the “microsphere”, and By compounding a crosslinking agent that can react with a functional group, the pressure-sensitive adhesive and the adhesive microspheres are chemically bonded, and the adhesive copolymer and the microspheres are bonded to the substrate by a chemical bond or an anchor effect. It is described that the bonding effectively prevents the adhesive component from remaining on the adherend.

  However, even with the above method, the adhesion of the fine sphere particles to the substrate is not necessarily sufficient, and there is a problem that adhesive residue may occur depending on the type of adherend and environmental conditions. Furthermore, by increasing the amount of the binder and the amount of the cross-linking agent, the adhesive residue on the adherend can be suppressed. Since the contact area to the surface decreases, it has been difficult to achieve both re-peeling and re-adhesion while maintaining a relatively high initial adhesive force.

  In order to solve the above-mentioned problems of the prior art, the present inventors have previously proposed two proposals relating to a re-peelable pressure-sensitive adhesive composition containing sticky microsphere particles, namely, a specific one. A re-peelable pressure-sensitive adhesive composition (Patent Document 8) containing adhesive microsphere particles having a storage elastic modulus of 5 and a adhesive microsphere particle having a gel content and a molecular weight in a specific range A proposal for a re-peelable pressure-sensitive adhesive composition (Patent Document 9) was made. These pressure-sensitive adhesive sheets based on the re-peelable pressure-sensitive adhesive composition proposed by the present inventors are more advantageous in terms of initial adhesiveness, re-peeling / re-adhesiveness than pressure-sensitive adhesive sheets according to the prior art. It was very good.

  By the way, conventionally, when producing a pressure-sensitive adhesive sheet, rather than a direct coating method in which a pressure-sensitive adhesive composition is directly applied to the surface of a substrate and dried to form a pressure-sensitive adhesive layer on the surface of the substrate. Rather, after the pressure-sensitive adhesive composition is applied and dried once on a release material (the surface of a paper or plastic film is released with a silicone resin or the like), a pressure-sensitive adhesive layer is formed. Many transfer methods for transferring this to the surface of the substrate are employed. This is because the base material such as paper is directly applied and dried with the pressure-sensitive adhesive composition, which causes deformation due to wrinkles or shrinkage, and the quality of the product is often significantly reduced. In the case of heat-sensitive recording paper, it takes a long time to process because the heating temperature during drying cannot be increased, and the components contained in the pressure-sensitive adhesive composition, such as surfactants and organic solvents This is because, for example, capsules containing pigments and dyes contained in the thermal recording paper may be broken and color may develop.

  However, in the pressure-sensitive adhesive composition containing the sticky microsphere particles, as a feature thereof, the pressure-sensitive adhesive layer formed as described above is protruded and uneven in the surface of the pressure-sensitive adhesive layer. If this is directly transferred to the base material, it is clear that the contact area between the base material and the pressure-sensitive adhesive layer becomes small, and problems with adhesion are likely to occur. In addition, the new surface of the pressure-sensitive adhesive layer after transfer to the substrate is a fairly flat surface because it was dried in contact with the release material before transfer, and in particular, binders etc. This tendency is remarkable in the pressure-sensitive adhesive composition containing the same. When such a pressure-sensitive adhesive composition is used for a re-peelable pressure-sensitive adhesive sheet, there are the same problems as in the case of the pressure-sensitive adhesive composition that does not contain the above-mentioned microsphere particles. The problem of transfer of pressure-sensitive adhesive is more likely to occur due to the problem of substrate adhesion of the pressure-sensitive adhesive layer. Also, the proposals of Patent Documents 8 and 9 by the present inventors have been found that the same problems cannot be avoided when these pressure-sensitive adhesive compositions are used in a transfer method.

  In order to solve the problems associated with the above transfer method, Patent Document 10 discloses that a strong pressure-sensitive adhesive layer is formed on at least one surface of a support (base material), and a fine spherical pressure-sensitive adhesive layer is formed on the strong pressure-sensitive adhesive layer. An adhesive tape having a slightly adhesive layer on which is formed has been proposed. According to this proposal, both the pressure-sensitive adhesive layer formed by directly applying and drying on the support and the microspherical pressure-sensitive adhesive layer formed by separately applying and drying on the release paper, After laminating the layers so that the layers face each other, the support and release paper are peeled off to transfer the fine spherical adhesive layer onto the strong adhesive layer on the support.

  However, the method of Patent Document 10 employs a complicated and costly method in which two pressure-sensitive adhesive layers are separately applied and dried, and the strong pressure-sensitive adhesive layer on the substrate directly Since it is formed by the coating method, the above-mentioned problem of base material deformation cannot be avoided, and it is difficult to use thermal paper or the like as the base material.

  Furthermore, the pressure-sensitive adhesive sheet of the type using the number of adhesive microsphere particles as described above has been mainly used in the temporary use field where re-peeling and re-sticking can be performed with low adhesion. However, recently, a higher adhesive force is required, such as a non-adhesive microsphere particle number type solvent-type pressure-sensitive adhesive or an aqueous dispersion-type pressure-sensitive adhesive. The use up to the “medium adhesion” area has been demanded. And of course, it is used in the field of the use of “medium-adhesive” pressure-sensitive adhesives as well as demands for such curved surfaces and uneven surfaces as well as for removability, as well as in the production of ordinary pressure-sensitive adhesive sheets. There is a need for sheet production by the transfer method.

In general, in order to increase the adhesive force with the pressure sensitive adhesive of the number of sticky microsphere particles type, methods such as increasing the adhesive force of the number of microsphere particles or increasing the amount of the binder are conceivable. However, such a method has a problem that the number of adhesive microsphere particles and the binder are easily transferred to the adherend. Usually, an ionic viscosity modifier is used for the pressure sensitive adhesive of the number of sticky microsphere particles type, but the ionic viscosity modifier is a pressure-sensitive adhesive formed by time-dependent migration. There is a problem in that the surface of the adhesive microsphere particles in the layer moves to the surface, the surface of the microsphere particles becomes hard and the adhesive force is reduced, and the adhesive force to the adherend tends to be reduced. I understood that. In addition, pressure-sensitive adhesives whose viscosity has been adjusted with an ionic viscosity modifier usually have thixotropic viscosity characteristics, which may make it difficult to transfer with a pump during coating. For example, it has a problem that it is not suitable for coating using a coater having a relatively low share.
JP-A-50-2736 (Claims, specification, page 1, column 2, lines 11 to 15, page 5, column 16, line 6 to page 8, column 28, column 12 Example 1 ~ 11) JP-A-53-65330 (Claims, specification, page 1, right column, lines 7-12, page 2, lower right column, lines 12-18, page 3, upper right column, line 3-lower left column) (Line 18) JP-A-53-69233 (Claims, specification, page 1, right column, lines 7-13, page 3, upper left column, lines 4-8, page 3, lower left column, lines 4-4) (Upper left column, 5th line) JP-A-61-148278 (Claims, Specification, Page 4, Column 11, Lines 7-8) JP-A-61-258854 (Claims, specification, page 5, lower left column, line 7 to page 6, upper left column, line 19) JP-A-61-152779 (Claims) JP-A-61-261382 (Claims) JP 2000-281996 A (the whole specification) JP 2000-281999 A (the full description) JP-A-05-171118 (Claims, specification, second page, second column [0012] to third page, third column [0015], third page, third column [0017] to fourth column [0020] ])

The pressure-sensitive adhesive composition containing the adhesive microsphere particles allows the pressure-sensitive adhesive composition of the conventional adhesive microsphere particle type, such as curved surface adhesion, rough surface adhesion, removability, and restickability. Development of a pressure-sensitive adhesive composition capable of producing a pressure-sensitive adhesive sheet that has a higher adhesive strength and enters the so-called “medium-tackiness” region, while maintaining the advantages of the adhesive, and in particular, transfer to a substrate by a transfer method As a result, development studies have been conducted on a method of forming a pressure-sensitive adhesive layer having excellent adhesion to the substrate surface. As a result, first, at least one fine spherical particle (A ₁ ) having a melting temperature of 100 ° C. or higher, for example, which does not melt at the time of drying, and fine spherical particles having a melting temperature of, for example, about 40 ° C. A ₂ ) The viscosity of the adhesive microsphere particles comprising at least one kind, the microparticles (B) mainly acting as a binder of the adhesive microsphere particles, and the dispersion of these particles are increased, and the viscosity is increased. When a pressure-sensitive adhesive layer was formed by applying and drying an aqueous pressure-sensitive adhesive composition containing a viscosity modifier (C) to keep it properly, the fine spherical particles (A ₂ ) that melt at the drying temperature It was found that the surface and the back surface (surface on the side in contact with the mold release material) form a substantially similar surface state having moderate irregularities in a low hill shape because of melting. Such a pressure-sensitive adhesive layer can be transferred relatively easily onto a general-purpose substrate such as fine paper, and the resulting pressure-sensitive adhesive layer has excellent adhesion to the substrate and has excellent re-use. It has been found that it has peelability.

  Furthermore, as the above-mentioned viscosity modifier (C), an ionic viscosity modifier is used together with a conventionally used ionic viscosity modifier and a nonionic viscosity modifier such as a urethane-modified polyether type viscosity modifier. In the past, non-adhesive microsphere particle type solvent-type pressure-sensitive adhesives and water-dispersed pressure-sensitive adhesives have been used. In addition, it can be used up to the so-called “medium tackiness” region where higher adhesive strength is required, and can impart excellent viscosity characteristics to the pressure-sensitive adhesive composition. The present inventors have found that a pressure-sensitive adhesive composition excellent in various stability and workability can be provided, and completed the present invention.

According to the present invention, adhesive microsphere particles (A) having a volume average particle diameter (d _A ) of 1 μm or more, fine particles (B) having a volume average particle diameter (d _B ) of less than 1 μm, and a viscosity modifier (C) In the water-based pressure-sensitive adhesive composition comprising the above, the adhesive microsphere particles (A) are at least one kind of high melting point microsphere particles (A ₁ ) having a melting temperature higher than 60 ° C. and a melting temperature of 60 ° C. The following low melting point fine sphere particles (A ₂ ) are composed of at least one kind, and the viscosity modifier is composed of at least one kind of ionic viscosity modifier (C ₁ ) and nonionic viscosity modifier (C ₂ ). A pressure-sensitive adhesive composition is provided.

Further, according to the present invention, adhesive microsphere particles (A) having a volume average particle diameter (d _A ) of 1 μm or more, fine particles (B) having a volume average particle diameter (d _B ) of less than 1 μm, and a viscosity modifier (C In the method for producing a pressure-sensitive adhesive sheet using an aqueous pressure-sensitive adhesive composition comprising:
(1) The aqueous pressure-sensitive adhesive composition of the present invention is applied on a release material whose surface has been release-treated,
(2) The object to be coated on the release material is dried at a temperature of 60 ° C. or higher, and is not yet put in the binder layer containing the molten low melting point fine sphere particles (A ₂ ) and the formed fine particles (B). The melted high melting point fine sphere particles (A ₁ ) are dispersed and fixed to form a pressure-sensitive adhesive layer having a number of low hill-like irregularities on the surface, and (3) the resulting pressure sensitive Pressurizing the base material on the adhesive layer and transferring the pressure-sensitive adhesive layer on the base material;
The manufacturing method characterized by comprising is provided.

  Furthermore, according to the present invention, the pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a number of low hill-like irregularities, and the pressure-sensitive adhesive layer uses the aqueous pressure-sensitive adhesive composition of the present invention. There is provided a pressure-sensitive adhesive sheet characterized by being formed by the manufacturing method of the present invention.

  The pressure-sensitive adhesive sheet formed using the water-based pressure-sensitive adhesive composition of the present invention can be applied to any of various types of adherends such as paper, metal, plastics, etc. whose surface is a smooth or rough surface. However, it has good adhesiveness, can be re-peeled without any adhesive residue at the time of peeling, and can be repeatedly applied and peeled off.

  In addition, since the pressure-sensitive adhesive sheet formed using the aqueous pressure-sensitive adhesive composition of the present invention can maintain a high adhesive force on the surface of the fine sphere particles, conventionally, a non-adhesive fine sphere particle type solvent-type pressure sensitive It can be used up to the so-called “medium tackiness” region where higher adhesive strength is required, where adhesives and water-dispersed pressure sensitive adhesives have been used.

  In particular, the aqueous pressure-sensitive adhesive composition of the present invention can be used for the production of a pressure-sensitive adhesive sheet by a transfer method, which is difficult with a pressure-sensitive adhesive composition containing ordinary adhesive microsphere particles. The obtained pressure-sensitive adhesive sheet is excellent not only in adhesion to the substrate but also in adhesion to the adherend, removability, and repeatability of sticking and peeling.

Hereinafter, the present invention will be described in more detail.
The pressure-sensitive adhesive composition of the present invention has a melting temperature higher than 60 ° C., more preferably 80 ° C. or higher, as adhesive microsphere particles (A) that are relatively coarse particles having a volume average particle diameter (d _A ) of 1 μm or more. In particular, high melting point microsphere particles (A ₁ ) having a melting temperature of 100 ° C. or higher and a low melting point having a melting temperature of 60 ° C. or lower, more preferably 55 ° C. or lower, particularly 50 ° C. or lower. The first feature is that it contains at least two types of adhesive microsphere particles comprising at least one type of microsphere particles (A ₂ ).

When the melting point of the high melting point fine sphere particles (A ₁ ) is equal to or lower than the above melting temperature, when the pressure sensitive adhesive composition is produced using the resulting pressure sensitive adhesive composition, The advantage of combining microspheres is lost when all are melted, and the compression elastic modulus of the high melting point microsphere particles (A ₁ ) is not so high, so that the pressure sensitive adhesive sheet can be wound or stored. The adhesive microsphere particles are flattened by an external pressure, which may cause a problem in product storage stability such as deterioration in the quality of the pressure-sensitive adhesive sheet. On the other hand, when the melting temperature of the low melting point fine sphere particles (A ₂ ) is higher than the above melting temperature, when the pressure sensitive adhesive sheet is produced, the adhesive fine sphere particles (A ₂ ) do not melt at the time of drying. Desirable low hill-like moderate unevenness is difficult to obtain, and when transferred to a substrate, adhesion to the substrate cannot be obtained sufficiently, which is not preferable.

The “melting temperature” in the present specification means the temperature at which the melt viscosity measured by a flow tester [“CFT-500D”; manufactured by Shimadzu Corporation] is 1.0 × 10 ⁴ Pa · s. It shall be said.

The high-melting-point fine sphere particles (A ₁ ) used in the present invention are fine sphere particles having an adhesive property per se, and are not particularly limited as long as the above conditions are satisfied. From the viewpoint of excellent physical properties of the pressure-sensitive adhesive composition, an acrylic (co) polymer, that is, a (co) polymer based on a monomer containing at least 50% by weight of a (meth) acrylic acid ester monomer It is preferable that it is formed by.

Such acrylic (co) polymers specifically include the following monomers (a ₁₁ ) to (a ₁₄ ),
_{(A 11)} the general formula _CH 2 = CHCOOR ¹ (where, ^{R 1} represents a straight-chain or branched alkyl group having 4 to 10 carbon atoms) acrylate monomer represented by,
_{(A 12)} an unsaturated monomer having a carboxyl group,
(A ₁₃₎ a monomer having at least two radically polymerizable unsaturated groups in the molecule, and,
_{(A 14)} the monomers _{(a 11) ~ (a 13} ) and copolymerizable, the monomer _{(a 11) ~ (a 13} ) than the unsaturated monomer,
(Co) polymerized is preferable.

The monomer (a ₁₁ ) is an acrylate ester represented by the formula CH ₂ ═CHCOOR ¹ , and R ¹ represents a linear or branched alkyl group having 4 to 10 carbon atoms. Examples of R ¹ are n-butyl, i-butyl, n-hexyl, 2-ethylhexyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl. Examples include groups. Specific examples of such acrylates include n-butyl acrylate, i-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl. Examples thereof include acrylate and n-decyl acrylate. Among these, it is preferable to use n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl acrylate and the like.

The amount of the acrylic acid ester used as the monomer (a ₁₁ ) is based on the weight of the (co) polymer that forms the high melting point microsphere particles (A ₁ ), that is, the monomer that forms the (co) polymer. For example, 60 to 100% by weight, preferably 65 to 99.8% by weight, and particularly preferably 70 to 99.5% by weight, based on the total 100% by weight of the monomers (a ₁ ) to (a ₄ ). By using the monomer (a ₁ ) above the lower limit value, the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength, and has a good balance between adhesive strength and cohesive strength. It is preferable because stability and heat and humidity resistance can be achieved. On the other hand, by the monomer the amount of (a ₁₎ and more than the upper limit, the dispersion when the addition mechanical stability (shear force of a dispersion of high-melting fine spherical particles (A ₁₎ Stability) can be further improved, which is preferable.

Examples of the monomer having a carboxyl group as the monomer (a ₁₂ ) include α, β-unsaturated mono- or di-carboxylic acid monomers. The use of β-unsaturated mono- or di-carboxylic acid monomers is preferred. Specific examples of such monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and citraconic acid. Among these, the use of acrylic acid, methacrylic acid, and itaconic acid is more preferable.

The amount of the monomer _{(a 12),} based on the total 100% by weight of the monomer _{(a 11) ~ (a 14} ), for example 0-10% by weight, preferably from 0.2 to 5% by weight, Particularly preferred is 0.5 to 2% by weight. If the amount of the monomer (a ₁₂ ) used is less than or equal to the upper limit, the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesion, and a good balance between adhesion and cohesion, adhesion Is preferable because it can achieve the stability over time and the heat and humidity resistance. On the other hand, when the amount of the monomer (a ₁₂ ) used is not less than the lower limit, the mechanical stability of the dispersion of the high melting point microsphere particles (A ₁ ) (the dispersion of the dispersion when the shearing force is applied) Stability) can be further improved, which is preferable.

Further, examples of the monomer (a ₁₃ ) that has at least two radically polymerizable unsaturated groups in the molecule include divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate. , Ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexane Examples include diol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and allyl (meth) acrylate. Among these, use of divinylbenzene, diallyl phthalate, triallyl cyanurate, ethylene glycol di (meth) acrylate, or the like is preferable.

The amount of the monomer (a ₁₃ ) used is, for example, 0 to 1% by weight, preferably 0.001 to 0.5% by weight based on the total 100% by weight of the monomers (a ₁₁ ) to (a ₁₄ ). %, Particularly preferably 0.005 to 0.2% by weight. If the amount of the monomer (a ₁₃ ) used is less than or equal to the upper limit value, the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength, and preferably has good removability. . On the other hand, when the amount of the monomer (a ₁₃ ) used is not less than the lower limit, the high melting point microsphere particles (A ₁ ) are flattened by external pressure during winding or storage of the pressure sensitive adhesive sheet. Therefore, it is preferable because problems such as a problem in product storage stability such as deterioration of the quality of the pressure-sensitive adhesive sheet hardly occur.

Further, the monomeric _{(a 14),} the monomer _{(a 11) ~ (a 13} ) and copolymerizable, the monomer _{(a 11) ~ (a 13} ) than the unsaturated monomer As, for example, acrylic acid ester having 1 to 3 carbon atoms of alkyl group such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, etc .; for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i -Methacrylic acid esters such as butyl methacrylate can be mentioned.

Examples of the monomer (a ₁₄ ) include saturated fatty acid vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate and “vinyl versatate” (trade name) (preferably vinyl acetate); for example, styrene, α -Aromatic vinyl monomers such as methylstyrene and vinyltoluene (preferably styrene); for example, dimethylmalate, di-n-butylmalate, di-2-ethylhexylmalate, di-n-octylmalate, dimethylfuma Maleic acid or fumaric acid diesters such as rate, di-n-butyl fumarate, di-2-ethylhexyl fumarate, di-n-octyl fumarate; and more selected comonomers can be used as well.

Further, as the monomer (a ₁₄ ), a monomer having at least one functional group other than a carboxyl group in addition to one radical polymerizable unsaturated group in the molecule may be used.

Examples of such a monomer (a ₁₄ ) include functional groups such as an amide group or a substituted amide group, an amino group or a substituted amino group, a hydroxyl group, a lower alkoxyl group, an epoxy group, a mercapto group, or a silicon-containing group. The monomer which has can be mentioned.

Specific examples of these monomers (a ₁₄ ) include acrylamide, methacrylamide, diacetone acrylamide, N-methylol acrylamide, N-methylol methacrylamide, Nn-butoxymethyl acrylamide, Ni-butoxymethyl acrylamide, Amide group or substituted amide group-containing monomers such as N, N-dimethylacrylamide and N-methylacrylamide (preferably acrylamide and methacrylamide); for example, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N -Diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate (preferably N, N-dimethylaminoethyl methacrylate, N, N-diethylamino Amino or substituted amino group-containing monomers methacrylate) and the like;

For example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, methallyl alcohol, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate (preferably 2-hydroxyethyl Hydroxyl group-containing monomers such as acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate);

For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-n-butoxyethyl acrylate, 2-methoxyethoxyethyl acrylate, 2-ethoxyethoxyethyl acrylate, 2-n-butoxyethoxyethyl acrylate, 2-methoxyethyl methacrylate 2-ethoxyethyl methacrylate, 2-n-butoxyethyl methacrylate, 2-methoxyethoxyethyl methacrylate, 2-ethoxyethoxyethyl methacrylate, 2-n-butoxyethoxyethyl methacrylate, methoxypolyethylene glycol monoacrylate, methoxypolyethylene glycol monomethacrylate, (Preferably 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl methacrylate Rate, 2-ethoxyethyl methacrylate, methoxy polyethylene glycol monoacrylate, methoxy polyethylene glycol monomethacrylate) a lower alkoxyl group-containing monomers such as;

For example, epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, glycidyl methallyl ether (preferably glycidyl acrylate, glycidyl methacrylate); mercapto group-containing monomers such as allyl mercaptan;

For example, vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-propoxysilane, vinyltri-i-propoxysilane, vinyltri-n-butoxysilane, vinyltris (2-methoxyethoxy) silane , Vinyltris (2-hydroxymethoxyethoxy) silane, vinyltriacetoxysilane, vinyldiethoxysilanol, vinylethoxysiladiol, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, allyltrimethoxysilane, allyltri Ethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltris (2-meth Monomers having silicon-containing groups such as (ciethoxy) silane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-acryloxypropyldimethylmethoxysilane, 2-acrylamidoethyltriethoxysilane; And the like.

The amount of the monomer (a ₁₄ ) used is, for example, 0 to 40% by weight, preferably 0 to 30% by weight, based on the total 100% by weight of the monomers (a ₁₁ ) to (a ₁₄ ). Especially preferably, it is the range of 0-28 weight%. The amount of the monomer (a ₁₄ ) used can vary depending on the type of the monomer and is not uniquely determined. However, the balance between adhesive strength and tackiness, and the balance between these and cohesive strength, etc. Since it helps to adjust as desired, it can be appropriately selected in the range amount so as to meet such purpose.

If the amount of the monomer (a ₁₄ ) used is less than or equal to the above upper limit, the tackiness becomes too low, and the initial adhesiveness, particularly for rough surfaces such as cardboard, and for polyolefin-based adherends such as polyethylene. Inconveniences such as lowering of adhesive strength are unlikely to occur. Therefore, when the monomer (a ₁₄ ) is used, it is preferable to appropriately select and use within the range of the upper limit.

The high-melting-point microsphere particles (A ₁ ) used in the aqueous pressure-sensitive adhesive composition of the present invention are (co) polymerized using, for example, the monomer compositions (a ₁₁ ) to (a ₁₄ ) using an appropriate method. It is preferable that it is formed by the acrylic (co) polymer obtained by this, and the glass transition temperature (Tg _A1 ) of such a (co) polymer is usually −40 ° C. or lower, and further − It is preferably 50 ° C. or lower, particularly −60 ° C. or lower. If the glass transition temperature (Tg _A1 ) is equal to or lower than the upper limit value, it is preferable because disadvantages such as excessively low tackiness and reduced initial adhesiveness are unlikely to occur.

In the present invention, high-melting fine spherical particles (A ₁₎ and a glass transition temperature of the (co) polymers such as low-melting fine spherical particles (A ₂₎ and fine particles (B) to be described later, the differential scanning calorimeter It is a value measured using (DSC).

The volume average particle diameter (d _A1 ) of the high melting point fine sphere particles (A ₁ ) is usually in the range of _{1 to} 60 μm, preferably 10 to 50 μm, particularly preferably 20 to 40 μm. If the particle diameter (d _A1 ) is equal to or greater than the lower limit value, low hill-like moderate irregularities are formed on the surface of the resulting pressure-sensitive adhesive layer, and excellent re-peeling with excellent tackiness and adhesive strength. If it is below the upper limit, it is preferable because it has excellent adhesion to a substrate and good removability.

In the present invention, the volume average particle diameter of the adhesive microsphere particles (A) such as the high melting point microsphere particles (A ₁ ) and the low melting point microsphere particles (A ₂ ) described later is a light scattering type particle diameter measuring device [ “Mastersizer” 2000 (trade name); manufactured by Sysmex Corporation].

The high melting point microsphere particles (A ₁ ) used in the present invention are not necessarily limited, but it is usually preferable to produce them by a known suspension polymerization method. Specifically, for example, the polymerization initiator is dissolved in a mixture of the monomers (a ₁₁ ) to (a ₁₄ ) in an aqueous medium in the presence of a surfactant and, if necessary, a suspension stabilizer. Then, the mixture is stirred for a certain period of time to obtain an oil droplet emulsified liquid having a desired particle diameter range, and then the temperature is raised under a certain stirring rotational speed to initiate the polymerization reaction. The polymerization temperature can usually be exemplified by about 50 to 90 ° C.

  At the time of the suspension polymerization, a monomer is (co) polymerized by the generated radical to form a main chain, and at the same time, a crosslinking reaction occurs by a radical chain transfer reaction between the generated (co) polymer and the radical. Conceivable. However, this radical chain transfer reaction has a large uncertain factor, and in order to obtain a stable quality having a constant cross-linked state by radical reaction, it is important to control the initial reaction at the start of polymerization. The initial reaction can be controlled by raising the temperature in the presence of a substance having a polymerization inhibiting effect such as substitution with nitrogen or the like at the target temperature.

The “aqueous medium” means water or an aqueous solution of a water-soluble organic solvent. Examples of such water-soluble organic solvents include water-soluble alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; water-soluble ketones such as acetone; and water-soluble water such as methyl cellosolve, cellosolve, butyl cellosolve, carbitol, and butylcarbitol. Ethers; and the like. These can be used alone or in combination, and the amount used can be exemplified by about 0 to about 30% by weight as the concentration of the water-soluble organic solvent. The organic solvent can be used for the purpose of adjusting the melting temperature of the high melting point fine sphere particles (A ₁ ) composed of the (co) polymer, and contains the fine sphere particles (A ₁ ). From the viewpoint of standing stability and mechanical stability of the aqueous pressure-sensitive adhesive composition, it is more preferable to perform suspension polymerization in water substantially free of these organic solvents.

  In the present invention, as the surfactant, anionic surfactants and nonionic surfactants can be used alone or in combination, and in order to produce a suspension in particular, Anionic surfactants are preferred.

  Examples of the anionic surfactant include higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate; alkyl or alkenyl sulfate salts such as sodium lauryl sulfate and oleyl sulfate; For example, polyoxyethylene alkyl or alkenyl ether sulfate salts such as polyoxyethylene lauryl ether sulfate sodium salt, polyoxyethylene stearyl ether sulfate sodium salt, polyoxyethylene oleyl ether sulfate ammonium salt; for example, polyoxyethylene nonylphenyl ether Polyoxyethylene alkylaryl ether sulfate salts such as sodium sulfate ester; Sodium, sodium dioctylsulfosuccinate, sodium polyoxyethylene lauryl sulfosuccinate, alkyl or alkenyl sulfosuccinic acid ester salts and derivatives such as ammonium polyoxyethylene oleyl sulfosuccinate; and the like can be exemplified.

  The anionic surfactant that can be used in the present invention is further represented by the following general formula:

[Wherein R ⁴ represents a hydrocarbon group containing one or more aromatic rings, and M ⁺ represents a monovalent counter ion such as Na ⁺ , K ⁺ or NH ₄ ⁺ ]

R ⁴ in the above general formula is preferably derived from any of distyryl represented by the following three structural formulas or a mixture thereof.

  The length (value of p) of the polyoxyethylene chain in the general formula is generally in the range of 4 to 50, preferably in the range of 5 to 45.

  Specific examples of such anionic surfactants include, for example, “Hytenol NF-13”, “Hytenol NF-17” [trade name; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], “New Coal 707SF”. ”,“ New Coal 710SF ”,“ New Coal 714SF ”,“ New Coal 723SF ”,“ New Coal 740SF ”[trade name; manufactured by Nippon Emulsifier Co., Ltd.] and the like.

  These anionic surfactants can be used alone or in combination of two or more.

  Examples of the nonionic surfactant include polyoxyethylene alkyl or alkenyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; for example, polyoxyethylene octylphenyl ether, Polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether; for example, sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate; for example, polyoxyethylene sorbitan monolaurate Polyoxyethylene sorbitan higher fatty acid esters; for example, glycerin higher fatty acids such as oleic acid monoglyceride and stearic acid monoglyceride Ester such; for example, polyoxyethylene-polyoxypropylene block copolymer; the like can be exemplified.

These surfactants can be used in appropriate combinations, and the amount used is generally based on the weight of the (co) polymer forming the high melting point microsphere particles (A ₁ ), that is, the (co) polymer is used. Examples include about 0 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, based on a total of 100 parts by weight of the monomers (a ₁₁ ) to (a ₁₄ ) to be formed.

  Furthermore, recently, when surfactants containing alkylphenyl groups, which are widely used in aqueous dispersions of acrylic copolymers, are contained in wastewater and discharged into rivers, etc., these surfactants are hydrolyzed. Alkylphenols generated by decomposition are taken up by organisms that live in these rivers and the seas into which they flow, especially fish and shellfish, and act as substances that destroy the endocrine function (endocrine) of these organisms (so-called environmental hormones). Became known. It has been pointed out that such alkylphenols have a high risk of entering the human body through the intake of these fishery products, or directly through the water of the waterworks that use water such as rivers.

In the present invention, the above-mentioned nonionic and anionic surfactants are used for suspension polymerization of high melting point microsphere particles (A ₁ ) and low melting point microsphere particles (A ₂ ) and emulsion polymerization of microparticles (B). Among these, high melting point fine sphere particles (A ₁ ) and low melting point fine sphere particles (A ₂ ) in which the above-mentioned problems are eliminated by selecting and using those which do not substantially contain an alkylphenyl group as described above. And other additives such as a viscosity modifier (C), a tackifier (D), and a crosslinking agent (E) which will be described later. By selecting and using those which do not substantially contain an alkylphenyl group, an aqueous pressure-sensitive adhesive composition substantially free of an alkylphenyl group can be obtained.

  Examples of such surfactants include anionic surfactants such as higher fatty acid salts, alkylaryl sulfonates, alkyl or alkenyl sulfate esters, polyoxyethylene alkyl or alkenyl ether sulfate esters, alkyl or alkenyl sulfosuccinic acids. Polyoxyethylene polycyclic phenyl ether type surfactants of the above general formula (1) such as ester salts and derivatives thereof can be used. Nonionic surfactants include polyoxyethylene alkyl or alkenyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan higher fatty acid esters, polyoxyethylene sorbitan higher fatty acid esters, glycerin higher fatty acid esters, polyoxyethylene Ethylene / polyoxypropylene / block copolymers can be used.

  Here, “substantially free of alkylphenyl group” means that a surfactant containing the alkylphenyl group is not intentionally used in suspension polymerization or emulsion polymerization described later. Yes, even if the surfactant is contained as a contaminant in each raw material, an aqueous suspension, aqueous dispersion or final product of the (co) polymer obtained as a result of polymerization It means that the amount of surfactant containing an alkylphenyl group contained in the adhesive composition is 100 ppm or less, preferably 50 ppm or less.

Furthermore, in the present invention, a suspension stabilizer can be used as necessary in addition to the surfactant. As the suspension stabilizer, use of a water-soluble protective colloid is preferable. For example, polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose salt and the like Of cellulose derivatives; and the like. The amount of the water-soluble protective colloid used is generally based on the weight of the (co) polymer forming the high-melting microsphere particles (A ₁ ), that is, the monomer (a) forming the (co) polymer. 0.1-5 parts by weight based on 100 parts by weight of ₁₁₎ ~ _{(a 14),} preferably it can be exemplified 0.5 to 3 parts by weight.

Examples of the polymerization initiator used in the production of the high melting point microsphere particles (A ₁ ) suitably used in the present invention include benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butylperoxybivalate, t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyro Oils such as nitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobismethylisobutyrate The use of a soluble polymerization initiator is preferred. The oil-soluble polymerization initiator is used in an amount of 0.1 to 1.2 parts by weight, preferably 0.2 to 1 part by weight based on 100 parts by weight of the total of the monomers (a ₁₁ ) to (a ₁₄ ). Parts, particularly preferably 0.3 to 0.8 parts by weight. When the amount used is greater than or equal to the lower limit value, it is easy to control the initial reaction at the start of polymerization, and a stable quality having a certain cross-linked state can be obtained. When the amount used is less than the upper limit value, the molecular weight becomes too low. It is preferable because such a problem does not occur.

The pressure-sensitive adhesive composition of the present invention comprises low melting point microsphere particles (A ₂ ), that is, microspheres having a melting temperature of 60 ° C. or less, together with at least one high melting point microsphere particles (A ₁ ) detailed above. It contains at least one kind of particles (A ₂ ). By including such low-melting-point fine sphere particles (A ₂ ), it becomes possible to produce a pressure-sensitive adhesive sheet by a transfer method, which has been difficult with a normal pressure-sensitive adhesive composition containing fine sphere particles. . The reason for this is not necessarily unpleasant, but when the aqueous pressure-sensitive adhesive composition of the present invention is applied and dried on a release material, the low-melting microsphere particles (A ₂ ) are melted, or the resulting pressure-sensitive adhesive. It was found that both the surface and the back surface of the agent layer (the surface on the side in contact with the mold release material) formed substantially the same surface state having moderate undulations in a low hill shape. Such a pressure-sensitive adhesive layer can be transferred relatively easily onto a general-purpose substrate such as fine paper, and the resulting pressure-sensitive adhesive layer has excellent adhesion to the substrate and has a low melting Since the melting point microsphere particles (A ₂ ) component is firmly joined to the remaining high melting point microsphere particles (A ₁ ) and prevented from falling off, the adhesive is hardly transferred to the adherend. Excellent removability.

The low-melting-point microsphere particles (A ₂ ) used in the present invention are not particularly limited as long as they themselves are microsphere particles having adhesiveness and have a melting temperature of 60 ° C. or less. Is based on an acrylic (co) polymer, that is, a monomer containing at least 50% by weight of a (meth) acrylic acid ester monomer, from the viewpoint of excellent physical properties of the resulting pressure-sensitive adhesive composition. It is preferably formed of a (co) polymer.

Specifically, such acrylic (co) polymers include the following monomers (a ₂₁ ) to (a ₂₃ ),
(A ₂₁ ) an acrylate monomer represented by the general formula CH ₂ = CHCOOR ¹ wherein R ¹ is as defined in (a ₁₁ ) of the high-melting-point microsphere particles (A ₁ ),
_{(A 22)} an unsaturated monomer having a carboxyl group, and _{(a 23)} the monomers _{(a 21)} and _{(a 22)} and copolymerizable, the monomer _{(a 21)} and _{(a 22} ) Unsaturated monomers other than
(Co) polymerized is preferable.

Examples of the monomers _{(a 21),} can use the same acrylic acid ester monomer _{(a 11)} in the refractory fine spherical particles _{(A 1),} n- butyl acrylate, n- Use of hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl acrylate and the like is preferable.

The amount of the acrylic acid ester used as the monomer (a ₂₁ ) is based on the weight of the (co) polymer that forms the low-melting microsphere particles (A ₂ ), that is, the monomer that forms the (co) polymer. For example, 60 to 100% by weight, preferably 65 to 99.8% by weight, and particularly preferably 70 to 99.5% by weight, based on the total 100% by weight of the monomers (a ₂₁ ) to (a ₂₃ ). It is preferable to use the monomer (a ₂₁ ) above the lower limit value because the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesive force, and is excellent in adhesion to the substrate. On the other hand, it is preferable that the amount of the monomer (a ₂₁ ) be less than or equal to the upper limit because the pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength and good removability.

The monomer (a ₂₂ ) also includes the same α, β-unsaturated mono- or di-carboxylic acid monomer as the monomer (a ₁₂ ) in the high melting point microsphere particles (A ₁ ). The use of acrylic acid, methacrylic acid, itaconic acid is preferred.

The amount of the monomer (a ₂₂ ) used is, for example, 0 to 10% by weight, preferably 0.2 to 5% by weight, based on the total 100% by weight of the monomers (a ₂₁ ) to (a ₂₃ ). Particularly preferred is 0.5 to 2% by weight. If the amount of the monomer (a ₂₂₎ is less than the upper limit value, which has adhesive strength and tack pressure-sensitive adhesive sheet excellent obtained, good balance of cohesive strength and adhesive strength, adhesive strength Is preferable because it can achieve the stability over time and the heat and humidity resistance. On the other hand, by the monomer the amount of (a ₂₂₎ and said lower limit amount or more, the dispersion of the low-melting fine spherical particles (A ₂₎ Mechanical Stability (of the dispersion when added shear Stability) can be further improved, which is preferable.

Further, the monomeric _{(a 23),} the monomer _{(a 21)} and _{(a 22)} and copolymerizable, the monomer _{(a 21)} and _{(a 22)} than the unsaturated monomer As the same monomer group as the monomer (a ₁₄ ) in the high melting point microsphere particles (A ₁ ), that is, an acrylate ester, methacrylate ester or saturated fatty acid having an alkyl group having 1 to 3 carbon atoms. More than vinyl ester, aromatic vinyl monomer, diester of maleic acid or fumaric acid, monomer having at least one functional group other than carboxyl group in addition to one radical polymerizable unsaturated group in the molecule Separate comonomer can be used as well.

The amount of the monomer _{(a 23),} based on the total 100% by weight of the monomer _{(a 21) ~ (a 23} ), for example, 0 to 40 wt%, preferably 0-30 wt%, Especially preferably, it is the range of 0-28 weight%. The amount of the monomer (a ₂₃ ) used can vary depending on the type of the monomer and cannot be uniquely determined. However, the balance between adhesive force and tackiness, and the balance between these and cohesive force, etc. Since it helps to adjust as desired, it can be appropriately selected in the range amount so as to meet such purpose.

If the amount of the monomer (a ₂₃ ) used is less than or equal to the above upper limit value, the tackiness becomes too low, and the initial adhesiveness, particularly for rough surfaces such as corrugated cardboard, and for polyolefin-based adherends such as polyethylene. Inconveniences such as a decrease in adhesive strength are unlikely to occur. Therefore, when the monomer (a ₂₃ ) is used, it is preferable to appropriately select and use within the range of the upper limit.

The low-melting-point microsphere particles (A ₂ ) used in the aqueous pressure-sensitive adhesive composition of the present invention may be prepared by, for example, combining the monomer compositions (a ₂₁ ) to (a ₂₃ ) with an appropriate method (both). It is preferable that it is formed of an acrylic (co) polymer obtained by polymerization, and the glass transition temperature (Tg _A2 ) of such a (co) polymer is generally −40 ° C. or lower, Is preferably −50 ° C. or lower, particularly preferably −60 ° C. or lower. It is preferable that the glass transition temperature (Tg _A2 ) is equal to or lower than the upper limit because disadvantages such as insufficient adhesion to the substrate tend to be insufficient.

The volume average particle diameter (d _A2 ) of the low melting point fine sphere particles (A ₂ ) is usually in the range of 1 to 60 μm, preferably 10 to 50 μm, particularly preferably 20 to 40 μm. If the particle diameter (d _A2 ) is at least the lower limit value, the resulting pressure-sensitive adhesive sheet is preferable because it has good removability along with excellent tackiness and adhesive strength. The pressure-sensitive adhesive sheet is preferable because it has excellent tackiness and adhesive force and also has excellent adhesion to the substrate.

The method for producing the low melting point fine sphere particles (A ₂ ) used in the present invention is not particularly limited, but usually, for example, the same as the production of the above high melting point fine sphere particles (A ₁ ), for example, The total of the monomers (a ₂₁ ) to (a ₂₃ ) is added at a polymerization temperature of about 50 to 90 ° C. in an aqueous medium in the presence of a surfactant, a polymerization initiator, and if necessary, a suspension stabilizer. It is preferably produced by aqueous suspension polymerization.

The amount of each component used in the production of low-melting fine spherical particles (A _2), based on the weight of forming a low-melting fine spherical particles (A ₂₎ (co) polymer, i.e. (co) For a total of 100 parts by weight of the monomers (a ₂₁ ) to (a ₂₃ ) forming the polymer: surfactant, generally 0.5 to 10 parts by weight, preferably about 0.5 to 5 parts by weight; A water-soluble protective colloid that is a suspension stabilizer, generally 0.1 to 5 parts by weight, preferably about 0.5 to 3 parts by weight; a polymerization initiator, generally 0.1 to 1.2 parts by weight, preferably 0.2. Examples thereof include 2 to 1 part by weight, particularly preferably 0.3 to 0.8 part by weight.

In the production of the low melting point fine sphere particles (A ₂ ), for the purpose of adjusting the melting temperature to be low, the water-soluble organic solvent is contained in an appropriate amount such as about 30% by weight or less in the aqueous medium. be able to. The polymerization initiator can be appropriately selected from those exemplified with respect to the production of the high melting point fine sphere particles (A ₁ ).

Further, a chain transfer agent can be used for the purpose of adjusting the melting temperature to be lower. Examples of such chain transfer agent include n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, 2-mercapto. Examples include ethanol, 2-ethylhexyl thioglycolate, trichlorobromomethane, and the like. As the used amount, the 100 parts by weight of the total of the monomers _{(a 21) ~ (a 23} ), can be exemplified such usage example 0.001 to 0.01 parts by weight.

The weight ratio of the content of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ) in the pressure-sensitive adhesive composition of the present invention is not necessarily limited, but for example, (A ₁ ) / (A ₂ ) is in the range of 20/80 to 80/20, preferably in the range of 30/70 to 70/30, and more preferably in the range of 40/60 to 60/40. If the use ratio of the high melting point fine sphere particles (A ₁ ) is equal to or higher than the lower limit, the resulting pressure-sensitive adhesive sheet is preferable because it has excellent removability as well as excellent tackiness and adhesive strength. The pressure-sensitive adhesive sheet is preferable because the pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength and also has excellent adhesion to the substrate.

The aqueous pressure-sensitive adhesive composition of the present invention comprises the above-mentioned adhesive fine sphere particles (A) composed of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ), and the adhesive fine particles. It contains fine particles (B) having a particle diameter smaller than that of the spherical particles (A). In the aqueous pressure-sensitive adhesive composition, the fine particles (B) exist in a state of being uniformly dispersed in the form of an aqueous dispersion, and the high melting point fine sphere particles (A ₁ ) and the low melting point fine particles are present. In addition to improving the dispersion stability of the spherical particles (A ₂ ), the high-melting microsphere particles (A ₁ ) and the low-melting microsphere particles ( It is considered that A ₂ ) functions as a binder that bonds the _two to each other and physically fixes them to the substrate.

Examples of the fine particles (B) include (co) polymers obtained by emulsion polymerization, particularly acrylic (co) polymers, that is, monomers containing at least 50% by weight of (meth) acrylic acid ester monomers. It is preferable to be formed of a (co) polymer based on the above. The fine particles (B) are not particularly limited as long as they have the above-mentioned functions. However, due to the excellent physical properties of the resulting pressure-sensitive adhesive composition, the following monomers (b ₁ ) to (B ₃ ),
(B ₁ ) represented by the general formula CH ₂ = CR ² COOR ³ (where R ² represents H or CH ₃ , and R ³ represents a linear or branched alkyl group having 4 to 12 carbon atoms) (meth) Acrylic ester monomers,
(B ₂ ) an unsaturated monomer having a carboxyl group, and (b ₃ ) the monomers (b ₁ ) and (b ₂ ) copolymerizable with the monomers (b ₁ ) and (b ₂ ). ) Unsaturated monomers other than
It is preferable that it is a thing formed by copolymerizing.

R ³ in the monomer (b ₁ ) is, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, n-hexyl group, 2-ethylhexyl group, An n-octyl group, an i-octyl group, an n-nonyl group, an i-nonyl group, an n-decyl group, an n-dodecyl group, and the like can be given. Specific examples of such (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and n-hexyl (meth) acrylate. 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, etc. It can be illustrated.

The amount of the monomer (b ₁ ) used is based on the weight of the (co) polymer that forms the fine particles (B), that is, the monomers (b ₁ ) to (b ₃ ) that form the copolymer. For example, 50 to 100% by weight, preferably 55 to 99.8% by weight, particularly preferably 60 to 99.5% by weight. It is preferable to use the monomer (b ₁ ) above the lower limit value because the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength, and excellent adhesion to the substrate. On the other hand, by the monomer the amount of (b ₁₎ and more than the upper limit, making it possible to use such monomers containing the carboxyl group, acrylic (co) polymer This is preferable because the storage stability of the aqueous dispersion itself containing the fine particles (B) hardly causes a problem.

Examples of the monomer containing a carboxyl group is a monomer (b _2), the monomer in the refractory fine spherical particles (A ₁₎ (a ₂₎ the same, alpha, beta-unsaturated mono- -Or di-carboxylic acid monomers can be used, and the use of acrylic acid, methacrylic acid, itaconic acid is preferred.

The amount of the monomer (b ₂ ) used is, for example, 0 to 10% by weight, preferably 0.2 to 5% by weight, based on the total 100% by weight of the monomers (b ₁ ) to (b ₃ ). Particularly preferred is 0.5 to 2% by weight. If the amount of the monomer (b ₂ ) used is less than or equal to the upper limit value, the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength, and also has excellent adhesion to the substrate. preferable. On the other hand, the use of the lower limit value or more is preferable because problems in storage stability of the aqueous dispersion containing the acrylic (co) polymer microparticles (B) hardly occur.

Further, the monomeric _{(b 3),} the monomer _{(b 1)} and _{(b 2)} and copolymerizable, the monomer _{(b 1)} and _{(b 2)} than the unsaturated monomer As a saturated fatty acid vinyl ester, aromatic vinyl monomer, maleic acid or fumaric acid diester exemplified in the monomer (a ₄ ) in the high melting point microsphere particles (A ₁ ), A comonomer selected from monomers having a functional group other than at least one carboxyl group in addition to one radically polymerizable unsaturated group can be similarly used.

The amount of the monomer (b ₃ ) used is, for example, 0 to 50% by weight, preferably 0 to 40% by weight, based on the total 100% by weight of the monomers (b ₁ ) to (b ₃ ). Especially preferably, it is the range of 0 to 38 weight%. The amount of the monomer (b ₃ ) used can vary depending on the type of the monomer and is not uniquely determined. However, the balance between adhesive force and tackiness, and the balance between these and cohesive strength, etc. Since it helps to adjust as desired, it can be appropriately selected in the range amount so as to meet such purpose.

If the amount of the monomer (b ₃ ) used is less than or equal to the above upper limit value, the resulting pressure-sensitive adhesive sheet has excellent tackiness and adhesive strength, and also has excellent adhesion to the substrate. When the monomer (b ₃ ) is used, it is preferably selected and utilized appropriately within the range of the upper limit value.

The acrylic (co) polymer microparticles (B) preferably used in the water-based pressure-sensitive adhesive composition of the present invention may be prepared, for example, by combining the monomer compositions (b ₁ ) to (b ₃ ) with appropriate surface activity. It is preferable that it is formed by a (co) polymer obtained by emulsion polymerization in an aqueous medium using an agent, and the glass transition temperature (Tg _B ) of such a (co) polymer is generally It is preferably + 20 ° C. or lower, more preferably in the range of −60 to + 15 ° C., particularly preferably in the range of −40 to + 10 ° C. If the glass transition temperature (Tg _B ) is less than or equal to the upper limit, problems such as poor adhesiveness (adhesive strength and peeling method) of the pressure-sensitive adhesive sheet based on the resulting pressure-sensitive adhesive composition are unlikely to occur. Therefore, it is preferable that the lower limit value or more be used because problems such as poor removability of the pressure-sensitive adhesive sheet hardly occur.

Moreover, the volume average particle diameter (d _B ) of the fine particles (B) is usually in the range of 50 to 900 nm, preferably 80 to 500 nm, particularly preferably 100 to 300 nm. If the particle diameter (d _B ) is equal to or greater than the lower limit value, a large amount of emulsifier is not required when producing the fine particles (B), and therefore the stability over time and the heat and humidity resistance of the resulting pressure-sensitive adhesive sheet. And the like is preferable, and if it is less than or equal to the upper limit, it is preferable because problems such as problems in storage stability of the aqueous dispersion containing the acrylic copolymer microparticles (B) are less likely to occur.

  In the present invention, the volume average particle diameter of the fine particles (B) is measured by a light scattering particle diameter measuring apparatus “Zeta Sizer 1000HS” (trade name; manufactured by Sysmex Corporation).

As the surfactant used in the production of the fine particles (B), anionic surfactants and nonionic surfactants exemplified as those used in the production of the high melting point fine sphere particles (A ₁ ). Those appropriately selected from the above can be used alone or in combination. The amount of the surfactant used is 100 parts by weight of the (co) polymer that forms the fine particles (B), that is, the total of the monomers (b ₁ ) to (b ₃ ) that form the copolymer. Usually, it is preferably in the range of about 1 to 10 parts by weight with respect to 100% by weight.

In the emulsion polymerization, water-soluble polymerization initiators such as persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, hydrogen peroxide, and the like are added to the monomers (b ₁ ) to (b ₃ ). It is preferable to use in the range of about 0.05 to 1 part by weight per 100 parts by weight of the total. Further, in aqueous emulsion polymerization, if desired, as a reducing agent, for example, reducing organic compounds such as ascorbic acid, tartaric acid, citric acid and glucose; for example, sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite and the like A reducing inorganic compound can be illustrated. The amount of these reducing agents used is not particularly limited, but is used in the range of about 0.05 to 1 part by weight with respect to 100 parts by weight of the total of the monomers (b ₁ ) to (b ₃ ). can do.

The amount of the fine particles (B) used in the pressure-sensitive adhesive composition of the present invention is not necessarily limited, but the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The total amount is 100 parts by weight, for example, 5 to 100 parts by weight, preferably 10 to 50 parts by weight, and more preferably 15 to 35 parts by weight. If the use ratio of the fine particles (B) is equal to or higher than the lower limit value, the resulting pressure-sensitive adhesive sheet is preferable because it has excellent tackiness and adhesive strength, and also has excellent adhesion to the substrate, and the upper limit. If it is less than the value, the pressure-sensitive adhesive sheet is preferable because it has excellent tackiness and adhesive strength and good removability.

The aqueous pressure-sensitive adhesive composition of the present invention comprises the above-mentioned adhesive microsphere particles (A) [that is, high-melting microsphere particles (A ₁ ) and low-melting microsphere particles (A ₂ )], and fine particles ( B) and a viscosity modifier (C) are included. The second feature of the present invention is that the viscosity modifier (C) contains at least one ionic viscosity modifier (C ₁ ) and at least one nonionic viscosity modifier (C ₂ ).

  Generally, viscosity modifiers maintain various stability such as storage stability during storage, transportation and use of pressure-sensitive adhesive compositions, and correspond to the coating suitability of various coating machines (coaters) during coating. Used to make it possible.

  Conventionally, ionic viscosity modifiers that have been mainly used usually impart thixotropic viscosity characteristics, and can make a pressure-sensitive adhesive composition to a desired viscosity with a relatively small amount and good workability. It has the advantage that it can. In the thixotropic viscosity characteristic, the viscosity is high when the shearing force (share) is low, but rapidly decreases when the shear is high. Therefore, since the viscosity is high during storage and storage, sedimentation of the sticky microsphere particles in the pressure-sensitive adhesive composition is suppressed. However, if this property is too strong, it is difficult to transport the pressure-sensitive adhesive composition because the pump blades are idle, for example, in pump transportation where high shear is partially applied. Further, when a coating means having a relatively low share such as a comma type coater is used, it is applied in a region where the pressure-sensitive adhesive composition has a high viscosity, and problems such as uneven coating tend to occur.

  On the other hand, in order to increase the viscosity of a pressure-sensitive adhesive composition to a desired range using a nonionic viscosity modifier, the amount used is usually larger than that of an ionic viscosity modifier, Workability also tends to be slightly reduced. The viscosity characteristics of the resulting pressure-sensitive adhesive composition are relatively close to Newtonian flow, and the viscosity does not decrease so much even where the share is high. Therefore, if this property is too strong, when the pressure-sensitive adhesive composition is stored, in order to suppress sedimentation of the adhesive microsphere particles in the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition has a low share. It is necessary to keep the viscosity of the coating high, and in this case, coating with such a pressure-sensitive adhesive composition, especially with a reverse coater or lip coater that increases the share during coating, becomes difficult. Become.

  Accordingly, the viscosity characteristic of the pressure-sensitive adhesive composition is likely to cause problems even if it is too biased to thixotropic properties or too close to Newtonian flow.

The inventors of the present invention have obtained such a viscosity characteristic by combining a normal viscosity of a pressure-sensitive adhesive composition, for example, a viscosity in a high shear region with a viscosity at 25 ° C. and 60 rpm by a B-type rotational viscometer, for example, The determination was successful by measuring both the viscosity at 25 ° C. and a shear rate of 1 × 10 ⁴ sec ⁻¹ . In addition, using such means, as described above, both the ionic viscosity modifier (C ₁ ) and the nonionic viscosity modifier (C ₂ ) are blended into the pressure-sensitive adhesive composition, and By adjusting the amount used, the inventors succeeded in developing an aqueous pressure-sensitive adhesive composition having favorable viscosity characteristics.

Examples of the ionic viscosity modifier (C ₁ ) include polyacrylic acid, sodium polyacrylate, ammonium polyacrylate, sodium polyitaconate, modified polyacrylic acid, modified sodium polyacrylate, and partially saponified polyacrylic acid. Esters, sodium polyacrylate / polyacrylamide copolymer, carboxylated styrene / butadiene copolymer, methyl vinyl ether / maleic anhydride copolymer, (meth) acrylic acid copolymer, alkali thickening type (meth) acrylic Examples thereof include polycarboxylic acid type viscosity modifiers such as acid copolymer emulsions. Among them, alkali thickening type (meth) acrylic acid copolymer emulsions are preferred.

Specific examples of the polycarboxylic acid type viscosity modifier which is a preferable ionic viscosity modifier (C ₁ ) that can be used in the present invention include, for example, “Nicazole VT-253A” {trade name, Nippon Carbide Industries, Ltd. )}; "Aron A-20P", "Aron A-7150", "Aron A-7070", "Aron B-300", "Aron B-300K", "Aron B-500" {Product name, above Manufactured by Toagosei Co., Ltd .; “Julimar AC-10LHP”, “Julimar AC-10SHP”, “Leogic 250H”, “Leogic 835H”, “Junron PW-110”, “Junron PW-150” [Nippon Junyaku Co., Ltd.]; “Primal ASE-60”, “Primal TT-615”, “Primal RM-5” [trade name, Rohm and Ha "SN thickener A-818", "SN thickener A-850" [trade name, manufactured by San Nopco Co., Ltd.]; "Leorate 430" [trade name, Elementis Japan Co., Ltd.] Among them, particularly as the alkali-thickening type (meth) acrylic acid copolymer emulsion, “Nicazole VT-253A”, “Aron B-300K”, “Aron B— 500 "," Primal ASE-60 "," Primal TT-615 "," Primal RM-5 "," SN thickener A-850 "and the like.

Nonionic viscosity modifiers (C ₂ ) include, for example, surfactant type viscosity modifiers, polyether type viscosity modifiers, urethane-modified polyether type viscosity modifiers, guar gum, xanthan gum, carboxylated methylcellulose, hydroxyethylcellulose, polyvinyl Alcohol, hectorite, polysaccharide, polyethylene oxide and the like can be mentioned, and among them, urethane-modified polyether type viscosity modifier is preferable.

Specific examples of preferable nonionic viscosity modifier (C ₂ ) that can be used in the present invention include, for example, “Adecanol UH-420”, “Adecanol UH-450”, “Adecanol UH-540”, “Adecanol” “UH-752” [trade name, manufactured by Asahi Denka Kogyo Co., Ltd.]; “SN thickener 601”, “SN thickener 612”, “SN thickener 621N”, “SN thickener 623N” [trade name, above San Nopco) “Reorate 244”, “Leorate 278”, “Leorate 300” (trade name, manufactured by Elementis Japan Co., Ltd.); “DK Thickener SCT-275” [trade name, Daiichi Kogyo Seiyaku Co., Ltd.] Among them, particularly as urethane-modified polyether type viscosity modifier, “Adecanol U -752 "," SN thickener 621N "," SN thickener 623N "," Rheolate 244 ", and the like" Rheolate 278 ".

The amount of the viscosity modifier (C) used can be determined appropriately according to the desired viscosity and viscosity characteristics depending on the use of the aqueous pressure-sensitive adhesive composition of the present invention, but the adhesive microsphere particles (A) [ That is, the ionic viscosity modifier (C ₁ ) and the nonionic property with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ )] and the fine particles (B). the total amount of the active ingredient viscosity modifier _{(C 2),} in general, 1 to 10 parts by weight, preferably 2 to 8 parts by weight. In addition, when the viscosity modifier (C) is used, the ratio of the ionic viscosity modifier (C ₁ ) to the nonionic viscosity modifier (C ₂ ) is generally determined using the ionic viscosity modifier (C ₁ ) / Nonionic viscosity modifier (C ₂ ) = 90 / 10-20 / 80, preferably 70 / 30-40 / 60.

The aqueous pressure-sensitive adhesive composition of the present invention comprises the above-mentioned adhesive microsphere particles (A) [high-melting microsphere particles (A ₁ ) and low-melting microsphere particles (A ₂ )], fine particles (B) In addition to the viscosity modifier (C) [ionic viscosity modifier (C ₁ ) and nonionic viscosity modifier (C ₂ )], a tackifier (D) can be contained as necessary. The tackifier (D) is an initial adhesive property of the pressure-sensitive adhesive composition of the present invention, particularly an adhesive property to a rough surface adherend such as corrugated cardboard under light pressure bonding conditions, and a nonpolar adherend such as polyethylene. It is used for the purpose of improving.

  Examples of the tackifier (D) include natural resins, synthetic resins, and derivatives thereof. Specific examples thereof include terpenes such as polyterpene resins and modified terpenes. Rosin resins such as rosin, rosin ester, hydrogenated rosin ester, and the like. Examples of synthetic resins include aliphatic hydrocarbon resins, cyclopentadiene resins, C5 petroleum resins, and aromatic resins. Examples include petroleum resins such as petroleum resins; coumarone-indene resins, phenol resins, styrene resins, xylene resins, and the like. Of these, the use of petroleum resins, rosin resins or terpene resins is preferred.

  The softening point of the tackifier (D) is generally 70 to 180 ° C, preferably 100 to 160 ° C, particularly preferably 120 to 150 ° C, and its weight average molecular weight (Mw) is 5000 or less, particularly 2000 to 2000 ° C. 4000 is desirable.

  The tackifier (D) that can be used in the present invention is desirably one that can be stably dispersed in an aqueous medium, and the average particle size of the dispersed particles at this time is preferably 400 nm or less. More preferably, it is in the range of 50 to 350 nm. Moreover, it is preferable that tackifier (D) is a thing which does not contain an alkylphenyl type surfactant substantially in the aqueous dispersion.

The amount of the tackifier (D) used is usually 25 parts by weight or less with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). Is 0.1 to 25 parts by weight, more preferably 0.5 to 20 parts by weight, still more preferably 1 to 15 parts by weight, and particularly preferably 2 to 10 parts by weight. If the usage-amount of a tackifier (D) is more than this lower limit, since this pressure sensitive adhesive sheet has the outstanding adhesiveness and adhesive force, it is preferable. Further, the tackifier (D) generally does not significantly affect the physical properties of the pressure-sensitive adhesive layer obtained even when the amount used is increased, but it can be obtained depending on the type of the tackifier (D). In some cases, the viscosity of the pressure-sensitive adhesive composition may decrease, and in this case, the amount of thickener used may increase and affect the physical properties of the pressure-sensitive adhesive layer. It is preferable to use the imparting agent (D) within a range not exceeding the upper limit.

The aqueous pressure-sensitive adhesive composition of the present invention can further contain a crosslinking agent (E) as necessary. The crosslinking agent (E) is a combination of the high melting point fine sphere particles (A ₁ ) and the melted low melting point fine sphere particles (A ₂ ), and the fine particles of the adhesive fine sphere particles and the acrylic copolymer. For the purpose of enhancing the bond with the film based on the particles (B) and further improving the adhesion to the substrate, that is, increasing the cohesive force of the pressure-sensitive adhesive layer and the anchoring force of the pressure-sensitive adhesive layer and the substrate. Used for that purpose. In particular, when this aqueous pressure-sensitive adhesive composition is used as a re-peelable pressure-sensitive adhesive composition, this can improve re-peelability.

The crosslinking agent (E) is a functional group contained in the molecule of the copolymer constituting the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the fine particles (B). Is not particularly limited as long as it has two or more groups having reactivity with one molecule in the crosslinking agent, but by adding the crosslinking agent (E) to the aqueous pressure-sensitive adhesive composition It is preferable that the composition itself does not cause gelation or aggregates. That is, the crosslinking agent (E) is chemically stable (having storage stability) in the pressure-sensitive adhesive composition that is an aqueous dispersion, and the dispersion medium is used when the pressure-sensitive adhesive composition is applied. It is desirable to cause an irreversible cross-linking reaction by volatilization of or by means such as thermal energy for drying the pressure-sensitive adhesive composition.

  Specific examples of such a crosslinking agent (E) include carbodiimide crosslinking agents, oxazoline crosslinking agents, epoxy crosslinking agents, hydrazine crosslinking agents, and isocyanate crosslinking agents.

  The carbodiimide-based crosslinking agent is a compound containing two or more carbodiimide groups (—N═C═N—) in the molecule, and preferably has good water solubility or water dispersibility. Examples of the carbodiimide-based crosslinking agent include “Carbodilite V-02”, “Carbodilite V-02-L2”, “Carbodilite V-04”, “Carbodilite V-06” [trade name: manufactured by Nisshinbo Co., Ltd.] and the like. be able to.

When a carbodiimide-based crosslinking agent is used as the crosslinking agent (E), the molecules of the copolymer constituting the high-melting-point microsphere particles (A ₁ ), the low-melting-point microsphere particles (A ₂ ), and / or the fine particles (B) It is necessary to contain a carboxyl group, a hydroxyl group or an amino group as a counter functional group having reactivity with a carbodiimide group, and a monomer containing these functional groups is selected when polymerizing these particles. And copolymerize.

  The oxazoline-based cross-linking agent is a polymer obtained by (co) polymerizing an oxazoline group-containing monomer represented by the following general formula together with at least one other monomer copolymerizable therewith as necessary. It is preferably a water-soluble or water-dispersible polymer compound that is a compound and can be easily blended with the acrylic copolymer aqueous dispersion.

(Wherein R ^{5 to} R ⁸ are each independently hydrogen, halogen, an alkyl group, a cycloalkyl group, an aralkyl group or an aryl group; X is a single bond, —A ¹ —OCO—, —A ^2. —NHCO— or —A ³ —O—, each of A ^{1 to} A ³ independently represents a single bond or an alkylene group having 1 to 3 carbon atoms;

であり、Ｒ^９〜Ｒ^１１は、それぞれ独立して、水素又は炭素数１〜２のアルキル基である）

And R ^{9 to} R ¹¹ are each independently hydrogen or an alkyl group having 1 to 2 carbon atoms)

  Examples of the group Y include C2-C4 such as vinyl group, allyl group, propenyl group, i-propenyl group, α-butenyl group, β-butenyl group, γ-butenyl group, i-butenyl group, and the like. Alkenyl groups; for example, (meth) acryloyl group-containing groups such as (meth) acryloyloxy groups and (meth) acrylamide groups; for example, alkenyloxy groups having 2 to 4 carbon atoms such as vinyloxy groups and allyloxy groups. .

  Specific examples of such oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-i -Propenyl-2-oxazoline, 2-i-propenyl-4-methyl-2-oxazoline, 2-i-propenyl-5-ethyl-2-oxazoline can be exemplified, and 2 for reasons such as availability -The use of vinyl-2-oxazoline is preferred.

  The details of the high molecular weight oxazoline-based compound that can be used as the crosslinking agent (E) in the present invention are disclosed in, for example, JP-A-5-295275, and are produced according to the method disclosed in the publication. Can be used.

  The high molecular weight oxazoline-based cross-linking agent is, for example, “Epocross WS-500”, “Epocross WS-700” (manufactured by Nippon Shokubai Co., Ltd.), “NK LINKER FX” [Shin Nakamura Chemical Co., Ltd. As an emulsion type, for example, “Epocross K-1020E”, “Epocross K-2010E”, “Epocross K-2020E” (manufactured by Nippon Shokubai Co., Ltd.), etc. These are commercially available under the trade names, and any of these can be used as the crosslinking agent component in the present invention.

When an oxazoline-based cross-linking agent is used as the cross-linking agent (E), the molecules of the copolymer constituting the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the fine particles (B) It is necessary to contain a carboxyl group therein, and in the polymerization of these particles, a monomer containing a carboxyl group is preferably selected and copolymerized.

  In the present invention, the epoxy crosslinking agent that can be used as the crosslinking agent (E) is preferably water-soluble or water-dispersible.

  As such an epoxy-based crosslinking agent, for example, a polyol polyglycidyl ether compound, a polyacid polyglycidyl ester compound and the like can be suitably used. Specific examples of the polyol polyglycidyl ether compound include, for example, ethylene glycol diglycidyl ether, Diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol tri Glycidyl ether, polyglycerol (n ≒ 4,6 etc.) polyglycidyl ether Examples include trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, and specific examples of polyacid polyglycidyl ester compounds include, for example, adipic acid diglycidyl ester Can be mentioned. Among these epoxy-based crosslinking agents, particularly preferred are ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol triglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether It is.

  As such an aqueous solution of an epoxy-based cross-linking agent, for example, those sold by Nagase Kasei Kogyo Co., Ltd. under the trade name “Denacol” can be preferably used. For example, “Denacol EX-313”, “Denacol” What is marketed as "EX-314", "Denacol EX-611", "Denacol EX-614", "Denacol EX-810" can be used especially suitably.

When an epoxy-based crosslinking agent is used as the crosslinking agent (E), the molecules of the copolymer constituting the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the fine particles (B). It is necessary to contain a functional group having an active hydrogen having reactivity with an epoxy group, for example, a hydroxyl group, a carboxyl group, a mercapto group, an amino group or a substituted amino group. In this case, it is preferable to select and copolymerize monomers containing these functional groups.

In the present invention, the hydrazine-based crosslinking agent that can be used as the crosslinking agent (E) is a compound having two or more hydrazine residues (H ₂ N—NH—) in the molecule, and is water-soluble. Is preferably high. Specific examples of such hydrazine-based crosslinking agents include, for example, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, A dihydrazide of a dicarboxylic acid containing 2 to 10 carbon atoms such as isophthalic acid dihydrazide; for example, carbon number of ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine, etc. Mention may be made of organic dihydrazines containing 2-4. Of these, the use of dihydrazides of dicarboxylic acids containing 2 to 10 carbon atoms, particularly adipic acid dihydrazide, isophthalic acid dihydrazide, and succinic acid dihydrazide is particularly preferred.

When a hydrazine-based crosslinking agent is used as the crosslinking agent component (E), the copolymer constituting the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the fine particles (B) In the molecule, it is necessary to contain a carbonyl group as a counter-functional group having reactivity with a hydrazine residue. When polymerizing these particles, a monomer containing a carbonyl group is selected and copolymerized. Good.

  In the present invention, the isocyanate crosslinking agent that can be used as the crosslinking agent (E) includes a water-dispersible polyisocyanate composition, that is, an aqueous dispersion of a polyisocyanate compound or a water-dispersible polyisocyanate composition. It is preferable that it is a thing.

  Examples of the polyisocyanate compound include aromatic polyisocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate; aromatics such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated xylylene diisocyanate. Aliphatic or alicyclic polyisocyanates such as hydrogenated polyisocyanate compounds; dimers or trimers of these polyisocyanates or urethane-modified products of these polyisocyanates with dihydric alcohols; these polyisocyanates and trimethylolpropane And polyisocyanate compounds derived from various polyisocyanates such as adducts with polyols.

  The above-mentioned water-dispersible isocyanate composition usually contains an emulsifying dispersant component in order to increase its water dispersibility. Such an emulsifying dispersant component is a reaction between a polyisocyanate and a polyoxyalkylene compound. Preferably it is a product.

  Details of these water-dispersible isocyanate-based compositions and methods for producing the same are disclosed in JP-A-61-291613, JP-A-7-10950 and JP-A-8-85716. In order to avoid such a problem, these documents are referred to here to replace the detailed description.

  In the present invention, the water-dispersible isocyanate composition that can be suitably used as the isocyanate-based crosslinking agent can be appropriately selected from commercially available products. For example, “Aquanate 100”, “ "Aquanate 110", "Aquanate 200", "Aquanate 210" [trade name; manufactured by Nippon Polyurethane Industry Co., Ltd.]; and the like can be preferably used.

When an isocyanate-based crosslinking agent is used as the crosslinking agent (E), the molecules of the copolymer constituting the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the fine particles (B). It is necessary to contain a functional group having an active hydrogen having reactivity with an isocyanate group, for example, a hydroxyl group, a carboxyl group, a mercapto group, and the like. It is preferable to copolymerize by selecting a monomer containing.

  The water-based pressure-sensitive adhesive composition of the present invention can be appropriately selected and used from the above-mentioned crosslinking agents (E) as necessary, but the pot life of the resulting pressure-sensitive adhesive composition can be used. From the viewpoint of the crosslinking speed after drying the pressure-sensitive adhesive layer and the like, the use of a carbodiimide-based crosslinking agent is particularly preferable.

The amount of the crosslinking agent (E) used is not necessarily limited, but the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ), and / or the acrylic copolymer fine particles. The functional group in (B), that is, a total of 1 equivalent of carboxyl group, hydroxyl group, amino group, carbonyl group and the like is usually 2 equivalents or less, preferably 0.2 to 1.5 equivalents, more preferably 0.4. It should be in the range of ˜1 equivalent.

The aqueous pressure-sensitive adhesive composition of the present invention includes, for example, an aqueous dispersion of adhesive high-melting microsphere particles (A ₁ ) obtained by suspension polymerization as described above, and low-melting microsphere particles (A _2). ) And an aqueous dispersion of fine particles (B) obtained by emulsion polymerization are mixed in a predetermined amount, and then, if necessary, a tackifier (D) and a crosslinking agent (E), etc. And, if necessary, other additives are added and mixed, and the ionic viscosity modifier (C ₁ ) and nonionic viscosity modifier (C ₂ ) are appropriately added. It can produce by adjusting a viscosity and a viscosity characteristic by adding in quantity. Examples of other additives include a plasticizer, a pH adjuster, an antifoaming agent, an antiseptic / antifungal agent, a pigment, an inorganic filler, a stabilizer, a wetting agent, and a wetting agent.

  The aqueous pressure-sensitive adhesive composition of the present invention thus obtained generally has a solid content of 10 to 60% by weight, preferably 15 to 50% by weight, more preferably 20 to 45% by weight, and B-type rotational viscosity. The viscosity at 20 ° C. and 60 rpm is 100 to 10,000 mPa · s, preferably 500 to 5000 mPa · s, more preferably 1000 to 3000 mPa · s, and pH 4.0 to 8.5, preferably 6.0 to 8. 5, more preferably in the range of 6.5 to 8.5. In particular, when the crosslinking agent (E) is a high molecular weight oxazoline compound, the pH adjuster is preferably ammonia water from the viewpoint of curability and the stability of the pressure-sensitive adhesive composition. In particular, the range of 7.5 to 8.5 is preferable. Moreover, it is preferable that the water-based pressure-sensitive adhesive composition of the present invention does not substantially contain an alkylphenyl surfactant from the viewpoint of environmental conservation.

  As the surface base material of the pressure-sensitive adhesive sheet that can be produced using the aqueous pressure-sensitive adhesive composition of the present invention, in particular, the re-peelable pressure-sensitive adhesive sheet, it is possible to use one that is generally used. For example, printing paper such as high-quality paper, art paper, coated paper, cast paper; information recording paper such as thermal recording paper, thermal transfer recording paper, electrostatic recording paper, inkjet recording paper; other kraft paper, impregnated paper, low Paper base materials such as size paper and water-soluble paper; film base materials such as PET film, PE film and PP film; synthetic paper; non-woven fabric; and the like. These base materials alone or with a pressure-sensitive adhesive A substrate on which an anchor layer is laminated for the purpose of improving the adhesion can be used.

  The water-based pressure-sensitive adhesive composition of the present invention forms a pressure-sensitive adhesive layer, particularly a re-peelable pressure-sensitive adhesive layer, on at least one surface of the appropriate substrate selected according to the application. Thus, it can be used for producing a pressure-sensitive adhesive sheet, particularly a re-peelable pressure-sensitive adhesive sheet.

As a method for forming the pressure-sensitive adhesive layer, generally, using a known coating means, it is directly applied to the surface of the substrate, dried, and a release material is placed on the formed pressure-sensitive adhesive layer. It can be produced by a method of winding or cutting as necessary (direct method). The thickness of the pressure-sensitive adhesive layer is generally adjusted to about 3 to 30 g / m ² , preferably about 8 to 18 g / m ² . If the thickness of the pressure-sensitive adhesive layer is equal to or greater than the lower limit value, it is preferable because problems such as insufficient adhesion performance of the resulting pressure-sensitive adhesive sheet are unlikely to occur. This is preferable because a pressure-sensitive adhesive sheet of excellent quality can be obtained without increasing the above burden. In addition, as for the base material used, it is desirable to adjust the moisture content of water appropriately from viewpoints, such as the storage stability of the pressure sensitive adhesive sheet obtained.

In the above-described direct method, it is preferable to use a material in which a sealing layer is laminated on the coated surface of the substrate for the purpose of suppressing wrinkles due to penetration of the pressure-sensitive adhesive composition during coating. The sealing layer is not particularly limited. For example, casein, dextrin, starch, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, styrene-butadiene copolymer, methylmethacrylate-butadiene copolymer, ethylene-chloride. Using a material mainly composed of a natural or synthetic resin and a pigment such as a vinyl copolymer, an ethylene-vinyl acetate copolymer, and an acrylate copolymer, about 0.1 to 10 g / m ^{2 by} dry weight. The thickness can be provided. Examples of pigments used include inorganic pigments such as kaolin, calcium carbonate, clay, talc, calcined kaolin, deramikaolin, titanium dioxide, aluminum hydroxide, silica, white carbon; polystyrene resin microsphere particles, urea-formalin resin microspheres Organic synthetic pigments such as particles and fine hollow particles can be used.

  In the case of a substrate that is easily affected by heat, such as heat-sensitive recording paper or various films, it is preferable to select a substrate with a high heat resistance and to lower the drying temperature.

  Examples of the coating means used for coating the aqueous pressure-sensitive adhesive composition of the present invention include a roll coater, a reverse roll coater, a knife coater, an air knife coater, a bar coater, a slot die coater, and a lip coater. , Gravure coater, reverse gravure coater, and the like, and printing machines such as screen printing and gravure printing can also be used.

  Employing the direct method as the method for forming the pressure-sensitive adhesive layer requires the provision of a sealing layer on the surface of the base material for the purpose of preventing wrinkles of the base material as described above, and the type and processing of the base material. There are problems such as restrictions on conditions. In addition, some of the thermal recording paper and the like contain capsules containing pigments and dyes contained in the thermal recording paper for components contained in the pressure-sensitive adhesive composition, such as surfactants and organic solvents. There is also a problem in that the color of the material may be destroyed.

  The water-based pressure-sensitive adhesive composition of the present invention is widely used in the field of conventional pressure-sensitive adhesive sheet production, the indirect method (= transfer method) -that is, the pressure-sensitive adhesive composition is once applied on the release material. The third characteristic is that it can be used for the production of an excellent quality pressure-sensitive adhesive sheet by applying the same coating means as in the above-mentioned direct method, drying and then bonding to the substrate surface. It is.

  The conventional pressure-sensitive adhesive composition containing adhesive microsphere particles is characterized by forming a pressure-sensitive adhesive layer in which the adhesive microsphere particles protrude on the surface and become uneven, and thus the pressure-sensitive adhesive obtained. Adhesive sheets have the advantage that a constant contact area can be easily obtained regardless of the roughness of the adherend, and the adhesive strength that allows re-removal and re-adhesion can be maintained. In the production of the pressure-sensitive adhesive sheet, the contact area between the pressure-sensitive adhesive layer with the projections and depressions on the surface formed on the release material and the substrate is reduced, and there is a problem in the adhesion of the pressure-sensitive adhesive layer. Prone to occur. In addition, the new surface of the pressure-sensitive adhesive layer after transfer to the substrate is a fairly flat surface because it was dried in contact with the release material before transfer, and in particular, binders etc. This tendency is remarkable in the pressure-sensitive adhesive composition containing the same.

  Thus, the pressure-sensitive adhesive sheet prepared by the transfer method using the pressure-sensitive adhesive composition containing the conventional adhesive microsphere particles has the above-mentioned advantages of the pressure-sensitive adhesive layer containing the adhesive microsphere particles. Further, it was found that it was completely lost, and in addition, there was a problem with the adhesion to the base material, and it was found that it was completely unsuitable for producing a re-peelable pressure-sensitive adhesive sheet by the transfer method.

The present inventors use a pressure-sensitive adhesive composition containing sticky microsphere particles, and a method for forming a pressure-sensitive adhesive layer having excellent adhesion to a substrate, particularly on the substrate surface by a transfer method. As described above, as a result of the development study on the high-melting-point fine spherical particles (A ₁ ) and the low-melting-point fine particles as the adhesive fine spherical particles (A) that are relatively coarse particles having a volume average particle diameter of 1 μm or more as described above. As sphere particles (A ₂ ), relatively fine particles (B) having a volume average particle diameter of less than 1 μm, and viscosity modifier (C), ionic viscosity modifier (C ₁ ) and nonionic viscosity modifier An aqueous pressure-sensitive adhesive composition containing an agent (C ₂ ) was developed.

According to the water-based pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer formed on the release material is due to the melting of the fine spherical particles (A ₂ ) that melt at the drying temperature, and the surface is also the back surface. (The surface on the side in contact with the mold release material) also forms a substantially similar surface state having moderate irregularities in a low hill shape, and such a pressure-sensitive adhesive layer is relatively easy on the various substrates. It was found that the resulting pressure-sensitive adhesive layer was excellent in adhesion to the substrate and had excellent removability.

That is, the method for producing a pressure-sensitive adhesive sheet of the present invention comprises: adhesive microsphere particles ( _A ) having a volume average particle diameter (d _A ) of 1 μm or more, and fine particles (B) having a volume average particle diameter (d _B ) of less than 1 μm. And a method for producing a pressure-sensitive adhesive sheet using an aqueous pressure-sensitive adhesive composition comprising the viscosity modifier (C), the method comprising the following steps:
(1) An aqueous pressure-sensitive adhesive composition according to any aspect of the present invention is applied on a release material whose surface has been release-treated,
(2) The object to be coated on the release material is dried at a temperature of 60 ° C. or higher, and is not yet put in the binder layer containing the molten low melting point fine sphere particles (A ₂ ) and the formed fine particles (B). The molten high melting point microsphere particles (A ₁ ) are dispersed and fixed to form a pressure-sensitive adhesive layer having a large number of low hill-like irregularities on the surface, and (3) the resulting pressure sensitive Pressurizing the base material on the adhesive layer and transferring the pressure-sensitive adhesive layer on the base material;
It is a manufacturing method characterized by including.

Furthermore, the present invention provides a pressure-sensitive adhesive sheet having a number of low hill-like irregularities on the surface of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is an aqueous pressure-sensitive adhesive composition according to any aspect of the present invention. There is also provided a pressure-sensitive adhesive sheet characterized in that it is formed by using the above-mentioned method or formed by the above-described production method of the present invention.
As used herein, the “surface of the pressure-sensitive adhesive layer” refers to the surface that is in contact with the release material that is usually protected by the release material during storage or transportation, and is directly covered during use. It is the surface on the side in contact with the adherend, and does not mean the surface on the side in contact with the substrate of the pressure-sensitive adhesive sheet.

The release material that can be used in the present invention is not particularly limited, and general materials can be used. The base material of the release material is, for example, laminated paper such as polyethylene; glassine paper; clay-coated paper; glassine paper, kraft paper, high-quality paper, etc., with a thickness of about 0.1 to 10 g / m ^2. The base paper provided in the above; film base materials such as PET film, PE film, PP film; synthetic paper; non-woven fabric;

  The same material as in the base material for pressure-sensitive adhesive formation in the direct method is used for the sealing layer.

As the release agent, a general release agent can be used. For example, water-dispersed, solvent-type or solvent-free silicone resin, fluororesin, or the like is used, and 0.05% by dry weight is used for the base material of the release material. After applying so as to be about ˜3 g / m ^{2, a} release material can be obtained by forming a release layer by thermal curing, ionizing radiation curing or the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Production Examples. However, the present invention is not limited to these examples.

  In addition, preparation of the test piece used in an Example and a comparative example and various physical-property tests using it followed the following method.

(1) Preparation of re-peelable pressure-sensitive adhesive sheet An aqueous pressure-sensitive adhesive composition is wired on a release paper surface-treated with a silicone-based release agent so that the coating amount after drying is 16 g / m ^2. After applying with a bar and drying with a hot air circulation dryer at 105 ° C. for 90 seconds to form a pressure-sensitive adhesive layer, a substrate [high quality paper 70.4 g / m ^2] was formed on the surface of the pressure-sensitive adhesive layer. ; Manufactured by Oji Paper Co., Ltd.] using a squeegee and then pressed with a laminating roll, which was cured in a 400 ° C. thermostatic bath for 3 days to obtain a releasable pressure-sensitive adhesive sheet.

(2) Before measurement of initial adhesive strength The re-peelable pressure-sensitive adhesive sheet prepared in (1) was cut into a length of about 100 mm and a width of 25 mm to obtain a sample, and # 360 specified in JIS R-6253 SUS304 stainless steel plate (hereinafter sometimes abbreviated as SUS) polished with water-resistant abrasive paper and K liner paper (manufactured by Oji Paper Co., Ltd.) were used as adherends, and these samples were used according to the method of JIS Z-0237. A test piece was prepared by pressure bonding to the adherend. The test piece was allowed to stand for 30 minutes at 23 ° C. and 50% RH, and then the adhesive strength at 180 ° peeling at a peeling speed of 300 mm / min was measured under the same temperature and humidity conditions.

  For the measurement of the adhesive force, a constant speed extension type tensile tester was used, and an average peel force (unit: gf / 25 mm) was obtained from the obtained chart. The measurement was performed on three test pieces, and the average value thereof was taken as the value of the adhesive strength of the test pieces.

  In consideration of the practical suitability of the re-peelable pressure-sensitive adhesive sheet (adhesive strength that does not fall off from the adherend), the initial adhesive strength is generally preferably 50 gf / 25 mm or more. In consideration of reworking of the adhesive sheet, when the adherend is SUS, it is preferably 100 to 800 gf / 25 mm, more preferably 200 to 600 gf / 25 mm, and when the adherend is K liner paper. Considering the strength of the adherend, the initial adhesive strength is preferably 80 to less than 400 gf / 25 mm, more preferably 100 to 200 gf / 25 mm or less.

(3) Before adhesion to base material The peeled state of the test piece from the SUS adherend when the initial adhesive strength was measured in (2) was visually observed and evaluated according to the following evaluation criteria.

[Evaluation criteria]
○: Neither floating nor stringing is observed between the pressure-sensitive adhesive sheet base material and the pressure-sensitive adhesive layer.
◯: No adhesive remains on the adherend, but floating or stringing is observed between the pressure-sensitive adhesive sheet substrate / pressure-sensitive adhesive layer.
Δ: The pressure-sensitive adhesive layer peeled off from the pressure-sensitive adhesive sheet base material, and the adhesive residue generation area on the adherend was less than 50%.
X: The pressure-sensitive adhesive layer is peeled off from the pressure-sensitive adhesive sheet base material, and the adhesive remaining area on the adherend is 50% or more.

(4) Before the measurement of the adhesive strength with time, the test piece prepared in the same manner as in the item (2) was left in a constant temperature and humidity chamber of 40 ° C. × 90% RH for 7 days, and further at 23 ° C., 65% RH. After being left in the environment for 2 hours, the adhesive strength was measured in the same manner as in the previous item (2).

  When considering the practical suitability of the re-peelable pressure-sensitive adhesive sheet (adhesive strength that can be re-peeled from the adherend), the time-dependent adhesive strength is 1200 gf / 25 mm or less when the adherend is SUS, It is preferable that it is 1000 gf / 25 mm or less. When the adherend is K liner paper, the adhesive strength with time is preferably 700 gf / 25 mm or less, more preferably 450 gf / 25 mm or less, considering the strength of the adherend.

(5) Before re-peeling evaluation The peeled state of the test piece from the adherend during the time-dependent adhesion measurement in (3) was visually observed and evaluated according to the following evaluation criteria.

[Evaluation criteria]
○: Paper breakage of the pressure-sensitive adhesive sheet substrate and the adherend (K liner), as well as stringing of the pressure-sensitive adhesive at the time of peeling and no adhesive residue on the adherend (SUS and K liner).
○ △: Paper of pressure-sensitive adhesive sheet substrate and adherend (K liner) is not broken, and there is no adhesive residue on adherend (SUS and K liner) at the time of peeling, but pressure sensitive adhesive yarn at the time of peeling There is a whisper.
Δ: Paper breakage of the pressure-sensitive adhesive sheet substrate and adherend (K liner) is not torn, but part of the adhesive remains on the adherend (SUS or K liner) and the pressure-sensitive adhesive is stringed at the time of peeling. .
X: The pressure-sensitive adhesive sheet substrate and the adherend (K liner) were torn, or there was a sheet-like adhesive residue on the adherend (SUS or K liner) at the time of peeling, and it was not possible to peel off cleanly.

(6) Evaluation of curved surface adhesion The re-peelable pressure-sensitive adhesive sheet prepared in (1) above was cut into a size of 16 mm x 20 mm, and a cylindrical K having a diameter of 50 mm. The sample was attached to the side of the liner paper so that the 20 mm portion was curved, and the degree of floating and peeling after 24 hours was evaluated according to the following evaluation criteria.

[Evaluation criteria]
○: No lifting or peeling of the pressure-sensitive adhesive sheet.
◯: The area of the pressure-sensitive adhesive sheet where the pressure-sensitive adhesive sheet does not float or peel is 80% or more and less than 100%.
(Triangle | delta): The area of the part which a pressure-sensitive adhesive sheet does not float and peel is 50% or more and less than 80%.
X: The area of the part which does not float and peel of a pressure-sensitive adhesive sheet is less than 50%, or peels off completely.

[Production of high melting point fine sphere particles (A ₁ )]
Production Example A ₁ -1
In a reactor equipped with a thermometer, a stirrer, a raw material introduction tube, a nitrogen introduction tube and a reflux condenser, 150 parts by weight of ion-exchanged water, partially saponified polyvinyl alcohol “GOHSENOL KH-17” [trade name; Nippon Synthetic Chemical Co., Ltd. )] (KH-17) 5 wt% aqueous solution 60 parts by weight (active ingredient amount 3 parts by weight), anionic surfactant “Newcol 707SF” [trade name; polyoxyethylene (n = 7) distyrylphenyl Sodium sulfate ether salt and ammonium salt; manufactured by Nippon Emulsifier Co., Ltd.] (N707SF) aqueous solution (active ingredient 30% by weight) 0.32 part by weight (active ingredient amount 0.096 part by weight) was charged and stirred thoroughly. Dissolved.

  Next, in another container, 99.3 parts by weight of 2-ethylhexyl acrylate (EHA), 0.7 parts by weight of acrylic acid (AA), 0.1 part by weight of ethylene glycol dimethacrylate (EDM), “Perbutyl PV” [trade name T-butyl peroxypivalate (active ingredient concentration 70% by weight); manufactured by Nippon Oil & Fats Co., Ltd.] (PBPV) 0.34 parts by weight was mixed with stirring, and this monomer mixture was prepared in advance. After adding to the aqueous solution in the reactor and stirring at a stirring speed of about 300 rpm for 1 hour, 101 parts by weight of ion-exchanged water was added to the reaction vessel to perform nitrogen substitution, and heating was started. The polymerization reaction started at 52 to 55 ° C, and the heat was suddenly increased to around 80 ° C. This was cooled and kept at 75 ° C. for 4 hours.

The resulting aqueous suspension was then cooled to 30 ° C. and 2.5% by weight aqueous ammonia was added to pH 8-9. The characteristic value of the obtained aqueous suspension is 35.0% by weight of solid content and pH 8.4. The characteristic value of the fine sphere particles is a volume average particle diameter (d _A1 ) of 28 μm, a melting temperature of 120 ° C. The glass transition temperature (Tg _A1 ) of the polymer was -75 ° C.

Production Example A ₁ -2 to Production Example A ₁ -4
Production Example A ₁ -1, except for changing the stirring speed of the monomer mixture after addition to the reactor the polymerization reaction was conducted in the same manner as in Production Example A ₁ -1. Table 1 shows the stirring speed employed, the characteristic value of the obtained aqueous suspension, and the characteristic value of the fine spherical particles.

Production Example _A 1 -5 to Production Example _A 1 -7
Production Example A ₁ -1, changing the amount instead of using 0.1 parts by weight of EDM, or except not using this polymerization reaction was carried out in the same manner as in Production Example A ₁ -1. Table 1 shows the stirring speed employed, the characteristic value of the obtained aqueous suspension, and the characteristic value of the fine spherical particles.

Production Example _A 1 -8 to Production Example _A 1 -10
Production Example _A 1 -1, instead of using 99.3 parts by weight EHA, replacing a part or the whole as shown in Table 1 in butyl acrylate (BA), or more except using methyl methacrylate (MMA) the polymerization reaction was carried out in the same manner as in production example a ₁ -1. Table 1 shows the stirring speed employed, the characteristic value of the obtained aqueous suspension, and the characteristic value of the fine spherical particles.

[Production of Low Melting Point Microsphere Particles (A ₂ )]
Production Example A ₂ -1
The same reactor as used in Production Example A ₁ -1, 5 wt% aqueous solution of 20 parts by weight of 70 parts by weight of ion-exchanged water, partially saponified polyvinyl alcohol (KH-17) (amount of active ingredient 1 part by weight), anionic 1.68 parts by weight (active ingredient amount: 0.504 parts by weight) of an aqueous solution of the system surfactant N707SF (active ingredient concentration: 30% by weight) was charged and dissolved with sufficient stirring.

Next, 99 parts by weight of EHA, 1 part by weight of AA, 0.04 part by weight of n-dodecyl mercaptan (nDM), and 0.34 part by weight of PBPV are stirred and mixed in another container, and this monomer mixture is prepared in advance. Then, the mixture was added to the aqueous solution in the reactor and stirred at a stirring speed of about 300 rpm for 1 hour, and then 92 parts by weight of ion-exchanged water was added to the reaction vessel, and the temperature was increased by replacing with nitrogen. The polymerization reaction started at 52 to 55 ° C, and the heat was suddenly increased to around 80 ° C. This was cooled and kept at 75 ° C. for 4 hours. Thereafter, the resulting aqueous suspension was cooled to 30 ° C., and 2.5 wt% aqueous ammonia was added to adjust the pH to 8-9. The characteristic value of the obtained aqueous suspension is 35.0% by weight of solid content and pH 8.5, and the characteristic value of the fine sphere particles is a volume average particle diameter (d _A2 ) of 30 μm, a melting temperature of 40 ° C. The glass transition temperature (Tg _A2 ) of the polymer was -75 ° C.

Production Example A ₂ -2 to Production Example A ₂ -4
Production Example A ₂ -1, except for changing the stirring speed of the monomer mixture after addition to the reactor the polymerization reaction was conducted in the same manner as in Production Example A ₂ -1. Table 2 shows the amount of nDM used, the stirring speed employed, the characteristic value of the obtained aqueous suspension, and the characteristic value of the microsphere particles.

Production Example _A 2 -5
Production Example _A 2 -1, instead of using 0.04 parts by weight of nDM, except for using 0.01 parts by weight Polymerization was conducted in the same manner as in Production Example _A 2 -1. Table 2 shows the amount of nDM used, the stirring speed employed, the characteristic value of the obtained aqueous suspension, and the characteristic value of the microsphere particles.

Production Example _A 2 -6 to Production Example _A 2 -8
Production Example _A 2 -1, instead of using 99 parts by weight EHA, replacing a part or the whole as shown in Table 2 to BA, or even except for using MMA in the same manner as in Production Example _A 2 -1 A polymerization reaction was performed. Table 2 shows the amount of nDM used, the stirring speed employed, the characteristic value of the obtained aqueous suspension, and the characteristic value of the microsphere particles.

[Production of acrylic copolymer microparticles (B)]
Production Example B-1
The same reactor as used in Production Example A ₁ -1, was charged with ion-exchanged water 40 parts by weight, the internal temperature was raised to 60 ° C.. On the other hand, in another container, 19.8 parts by weight of ion-exchanged water, nonionic emulsifier “Emulgen E-1135-70” (trade name; polyoxyethylene alkyl ether (active ingredient concentration 70% by weight); manufactured by Kao Corporation) 4.15 parts by weight of aqueous solution (2.91 parts by weight of active ingredient), anionic surfactant “Neoperex G-65” [trade name; sodium alkylbenzene sulfonate (active ingredient concentration 65% by weight); Kao ( Co., Ltd.] 0.15 parts by weight (0.098 parts by weight of active ingredient) was charged and dissolved by stirring, and then 71.5 parts by weight of butyl acrylate (BA) and 27.5 parts by weight of methyl methacrylate (MMA). And a monomer mixture consisting of 1 part by weight of AA was added and stirred to obtain a monomer premix.

The reactor contents were heated with stirring under a nitrogen stream, and when the water temperature in the reactor reached 60 ° C., the polymerization initiator potassium persulfate (KPS) and the reducing agent sodium metabisulfite (SMBS) were each 0 After the addition of 0.073 parts by weight, a monomer premix, 6.7 parts by weight of a 2.5% by weight ammonium persulfate (APS) aqueous solution and 6.7 parts by weight of a 2.5% by weight SMBS aqueous solution were sequentially added to initiate polymerization. The polymerization reaction was carried out for about 2.5 hours. After completion of the polymerization reaction, stirring was continued at the same temperature for about 2 hours, followed by cooling, and 25 wt% aqueous ammonia was added to adjust pH to obtain an aqueous dispersion of acrylic copolymer microparticles. The characteristic values of this aqueous dispersion are solid content 55.0% by weight, pH 7.0, viscosity 100 mPa · s (25 ° C., BH type rotational viscometer 20 rpm), the characteristic values of acrylic copolymer microparticles are volume average particles The diameter was 170 nm and the glass transition temperature (Tg _B ) of the copolymer.

Production Example B-2 to Production Example B-5
In Production Example B-1, instead of using 71.5 parts by weight of BA and 27.5 parts by weight of MMA, the amount used was changed as shown in Table 3, or Production Example B-1 except that a part of BA was replaced with EHA. The polymerization reaction was carried out in the same manner as above. Table 3 shows the monomer composition used, the characteristic values of the obtained aqueous dispersion, and the volume average particle diameter and melting temperature of the adhesive microsphere particles.

[Preparation of re-peelable pressure-sensitive adhesive composition]
Example 1
Refractory fine spherical particles obtained in Production Example _A 1 -1 aqueous suspension 128.6 parts by weight (fine spherical particles of about 45 parts by weight) of _{(A 1),} the low obtained in Production Example _A 2 -1 aqueous suspensions 157.1 parts by weight of the melting fine spherical particles (a ₂₎ to (fine spherical particles of about 55 parts by weight), aqueous production example B-1 obtained in the acrylic copolymer microparticles (B) 36.4 parts by weight of dispersion (about 20 parts by weight of fine particles), ionic viscosity modifier (C ₁ ) “Nicazole VT-253A” [trade name; polycarboxylic acid type viscosity regulator; active ingredient 27% by weight; Japan Carbide Industries Co., Ltd.] (VT253A) 11.6 parts by weight (active ingredient 3.14 parts by weight), nonionic viscosity modifier (C ₂ ) “SN thickener 621N” [trade name; urethane-modified polyether type viscosity Conditioner; active ingredient 30% by weight; manufactured by San Nopco Co., Ltd.] (SN621N 8.6 parts by weight (active ingredient 2.57 parts by weight), aqueous dispersion of tackifier (D) “Superester E-788” [trade name; polymerized rosin tackifier; active ingredient 50% by weight; Arakawa Chemical Co., Ltd.] (E788) (10 parts by weight (active ingredient: about 5 parts by weight)) was added, then 25% by weight aqueous ammonia was added to adjust the pH, and then the aqueous solution of the crosslinking agent (E) “carbodilite” V-04 "[trade name: carbodiimide type cross-linking agent (carbodiimide equivalent 334), active ingredient 40 wt%; manufactured by Nisshinbo Co., Ltd.] (V04) 6.2 parts by weight (active ingredient about 2.47 parts by weight) added Thus, a re-peelable pressure-sensitive adhesive composition was produced.

The characteristic values of the obtained pressure-sensitive adhesive composition are solid content 37.1% by weight, pH 8.3, viscosity 2500 mPa · s, fine spherical particles (A ₁ ), fine spherical particles (A ₂ ), The total amount (T) of carboxyl groups contained in the polymer microparticles (B) is about 0.01148 equivalent parts, and the carbodiimide group of the crosslinking agent (E) is 0.00040 equivalent parts. The amount of carbodiimide groups relative to the total amount of carboxyl groups The equivalent ratio (E / T) was 0.5.

  Here, the “equivalent part” represents the number of equivalents when the “part by weight” is read as the number of grams. For example, when 1 equivalent of a predetermined functional group is present in 100 g of a substance, the substance 100 It is assumed that 1 equivalent part of the functional group is present in parts by weight.

  Using the obtained pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet was prepared according to the above, and various physical property tests were performed. The test results are shown in Table 6.

Examples 2-5 and Comparative Examples 1-2
In Example 1, the use ratio of the fine sphere particles (A ₁ ) obtained in Production Example A ₁ -1 and the fine sphere particles (A ₂ ) obtained in Production Example A ₂ -1 was changed, or the fine sphere particles A re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that (A ₁ ) or microsphere particles (A ₂ ) were not used, and a pressure-sensitive adhesive sheet was prepared using this to produce various physical properties. A test was conducted. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 6 to 8 and Comparative Example 3
In Example 1, re-peelable pressure-sensitive adhesive in the same manner as in Example 1 except that the amount of the acrylic copolymer microparticles (B) obtained in Production Example B-1 was changed or not used. An agent composition was prepared, a pressure-sensitive adhesive sheet was prepared using the composition, and various physical property tests were performed. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 9 to 10 and Comparative Examples 4 to 5
In Example 1, the re-peeling pressure sensitive sensor was changed in the same manner as in Example 1 except that the amounts of the ionic viscosity modifier (C ₁ ) and the nonionic viscosity modifier (C ₂ ) were changed or not used. An adhesive composition was prepared, a pressure-sensitive adhesive sheet was prepared using the adhesive composition, and various physical property tests were performed. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 11-13
In Example 1, instead of using VT253A as the ionic viscosity modifier (C ₁ ), “Aron B300K” [trade name; polycarboxylic acid type viscosity modifier; active ingredient 44% by weight; manufactured by Toa Gosei Co., Ltd.] ( B300K), “Primal TT-615” [trade name; polycarboxylic acid type viscosity modifier; active ingredient 30% by weight; manufactured by Rohm and Haas Japan Co., Ltd.] (TT615), or a combination of VT253A and B300K Except that, a re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a pressure-sensitive adhesive sheet was prepared using this and subjected to various physical property tests. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 14-16
In Example 1, instead of using SN621N as the nonionic viscosity modifier (C ₂ ), “SN thickener 623N” [trade name; urethane-modified polyether type viscosity modifier; active ingredient 30% by weight; manufactured by San Nopco Co., Ltd. (SN623N), “Adecanol UH-752” [trade name; urethane-modified polyether type viscosity modifier; active ingredient 30 wt%; manufactured by Asahi Denka Kogyo Co., Ltd.] (UH752), or a combination of SN621N and SN623N Except that, a re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was prepared using this, and various physical property tests were performed. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 17-21
In Example 1, a re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the amount of the tackifier (D) used was changed, or this was not used, and pressure sensitive was used using this. An adhesive sheet was prepared and subjected to various physical property tests. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 22-24
In Example 1, the amount of V04 used as the crosslinking agent (E) was changed, or instead of V04, “carbodilite V-02” [trade name; carbodiimide-based crosslinking agent (carbodiimide equivalent 590), active ingredient 40 wt%; Nisshinbo Co., Ltd.] A re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that 10.9 parts by weight (active ingredient: about 4.37 parts by weight) was added. A pressure-sensitive adhesive sheet was prepared using and various physical property tests were performed. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 25-28
In Example 1, instead of using the acrylic copolymer fine particles (B) obtained in Production Example B-1, Example 1 is used except that any one of Production Example B-2 to Production Example B-5 is used. Similarly, a re-peelable pressure-sensitive adhesive composition was prepared, and a pressure-sensitive adhesive sheet was prepared using the composition, and various physical property tests were performed. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 29 to 35 and Comparative Example 6
In Example 1, instead of using the microsphere particles (A ₂ ) obtained in Production Example A ₂ -1, any one of Production Example A ₂ -2 to Production Example A ₂ -8 and Production Example A ₁ -6 A re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that was used, and a pressure-sensitive adhesive sheet was prepared using this and subjected to various physical property tests. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Example 36
In Example 1, instead of using the fine spherical particles obtained in Production Example _{A 2} -1 _(A 2), using a fine spherical particles obtained in Production Example _{A 2} -5 _(A 2), the crosslinking agent ( A re-peelable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that E) was not used, and a pressure-sensitive adhesive sheet was prepared and subjected to various physical property tests. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

Examples 37-45
In Example 1, instead of using the fine spherical particles obtained in Production Example _A 1 -1 _{(A 1),} except for using any one of Preparation _A 1 -2 to Production Example _A 1 -10 Example 1 In the same manner as above, a re-peelable pressure-sensitive adhesive composition was prepared, and a pressure-sensitive adhesive sheet was prepared using the composition, and various physical property tests were performed. Table 4 and Table 5 show the compounding composition of the pressure-sensitive adhesive composition and the equivalent ratio of carbodiimide groups to the total amount of carboxyl groups, and Table 6 shows the characteristic values of the pressure-sensitive adhesive composition and the results of various physical properties tests. Show.

  Next, the gist of the present invention and preferred embodiments thereof will be listed.

[1] Including an adhesive microsphere particle (A) having a volume average particle diameter (d _A ) of 1 μm or more, a fine particle (B) having a volume average particle diameter (d _B ) of less than 1 μm, and a viscosity modifier (C). In the water-based pressure-sensitive adhesive composition, the adhesive microsphere particles (A) are at least one kind of high melting point microsphere particles (A ₁ ) having a melting temperature higher than 60 ° C. and a low melting temperature of 60 ° C. or lower. The melting point microsphere particles (A ₂ ) are composed of at least one kind, and the viscosity modifier is composed of at least one kind of ionic viscosity modifier (C ₁ ) and nonionic viscosity modifier (C ₂ ). A pressure-sensitive adhesive composition.

[2] The pressure-sensitive adhesive composition according to the above [1], wherein the high melting point fine sphere particles (A ₁ ) are formed of an acrylic (co) polymer.
[3] The pressure-sensitive adhesive composition according to the above [2], wherein the acrylic (co) polymer is composed of repeating units based on a monomer containing at least 50% by weight of a (meth) acrylic acid ester monomer. object.

[4] An acrylic (co) polymer has the following monomers (a ₁₁ ) to (a ₁₄ ):
_{(A 11)} the general formula _CH 2 = CHCOOR ¹ (where, ^{R 1} represents a straight-chain or branched alkyl group having 4 to 10 carbon atoms) acrylate monomer 60 to 100% by weight represented by,
_{(A 12)} unsaturated monomer 0 to 10% by weight having a carboxyl group,
(A ₁₃ ) 0 to 1% by weight of a monomer having at least two radically polymerizable unsaturated groups in the molecule, and
_{(A 14)} the monomers _{(a 11) ~ (a 13} ) and copolymerizable, the monomer _{(a 11) ~ (a 13} ) than the unsaturated monomer 0 to 40% by weight,
The pressure-sensitive adhesive composition according to the above [2] or [3], which is obtained by (co) polymerizing.

[5] The above [4], wherein the amount of the monomer (a ₁₁ ) used is in the range of 65 to 99.8% by weight based on the weight of the copolymer that forms the high melting point microsphere particles (A ₁ ). ] Pressure-sensitive adhesive composition as described in any one of the above.
[6] The above [4], wherein the amount of the monomer (a ₁₁ ) used is in the range of 70 to 99.5% by weight based on the weight of the copolymer forming the high melting point microsphere particles (A ₁ ). ] Or the pressure-sensitive adhesive composition according to [5].

[7] The above-mentioned, wherein the amount of the monomer (a ₁₂ ) used is in the range of 0.2 to 5% by weight based on the weight of the (co) polymer forming the high-melting microsphere particles (A ₁ ). [4] The pressure-sensitive adhesive composition according to [4].
[8] The amount of the monomer (a ₁₂ ) used is in the range of 0.5 to 2% by weight based on the weight of the (co) polymer forming the high melting point microsphere particles (A ₁ ). The pressure-sensitive adhesive composition according to [4] or [7].

[9] The amount of the monomer (a ₁₃ ) used is in the range of 0.001 to 0.5% by weight based on the weight of the (co) polymer forming the high melting point microsphere particles (A ₁ ). The pressure-sensitive adhesive composition according to [4] above.
[10] The amount of the monomer (a ₁₃ ) used is in the range of 0.005 to 0.2% by weight based on the weight of the (co) polymer forming the high melting point microsphere particles (A ₁ ). The pressure-sensitive adhesive composition according to [4] or [9] above.

[11] The pressure-sensitive adhesive composition according to the above [1], wherein the low melting point fine sphere particles (A ₂ ) are formed of an acrylic (co) polymer.
[12] The pressure-sensitive adhesive composition according to [11], wherein the acrylic (co) polymer is composed of repeating units based on a monomer containing at least 50% by weight of a (meth) acrylic acid ester monomer. object.
[13] An acrylic (co) polymer has the following monomers (a ₂₁ ) to (a ₂₃ ):
(A ₂₁ ) 60-100% by weight of an acrylate monomer represented by the general formula CH ₂ = CHCOOR ¹ [wherein R ¹ is as defined in (a ₁₁ ) of [4] above,
_{(A 22)} unsaturated monomer 0 to 10% by weight having a carboxyl group, and _{(a 23)} the monomers _{(a 21)} and _{(a 22)} and copolymerizable, the monomer _{(a 21} ) And 0 to 40% by weight of unsaturated monomer other than (a ₂₂ ),
The pressure-sensitive adhesive composition according to the above [11] or [12], which is obtained by (co) polymerizing.

[14] The above [13], wherein the amount of the monomer (a ₂₁ ) used is in the range of 65 to 99.8% by weight based on the weight of the copolymer forming the low-melting microsphere particles (A ₂ ). ] Pressure-sensitive adhesive composition as described in any one of the above.
[15] The above [13], wherein the amount of the monomer (a ₂₁ ) used is in the range of 70 to 99.5% by weight, based on the weight of the copolymer forming the low-melting microsphere particles (A ₂ ). ] Or the pressure-sensitive adhesive composition according to [14].

[16] The above [13], wherein the amount of the monomer (a ₂₂ ) used is in the range of 0.2 to 5% by weight based on the weight of the copolymer forming the low-melting microsphere particles (A ₂ ). ] Pressure-sensitive adhesive composition as described in any one of the above.
[17] The above [13], wherein the amount of the monomer (a ₂₂ ) used is in the range of 0.5 to 2% by weight based on the weight of the copolymer forming the low-melting microsphere particles (A ₂ ). ] Or the pressure-sensitive adhesive composition according to [16].

[18] The volume average particle diameter (d _A1 ) and / or (d _A2 ) of the high melting point fine sphere particles (A ₁ ) and / or the low melting point fine sphere particles (A ₂ ) is in the range of 1 to 60 μm. The pressure-sensitive adhesive composition according to [1], [2] or [11].
[19] The volume average particle size (d _A1 ) and / or (d _A2 ) of the high melting point fine sphere particles (A ₁ ) and / or the low melting point fine sphere particles (A ₂ ) is in the range of 10 to 50 μm. 1], [2], [11] or [18] The pressure-sensitive adhesive composition according to [18].
[20] The volume average particle diameter (d _A1 ) and / or (d _A2 ) of the high melting point fine sphere particles (A ₁ ) and / or the low melting point fine sphere particles (A ₂ ) is in the range of 20 to 40 μm. 1], [2], [11], [18] or [19] The pressure-sensitive adhesive composition according to [19].

[21] The above [1], wherein the glass transition temperature (Tg _A1 ) and / or (Tg _A2 ) of the high melting point fine sphere particles (A ₁ ) and / or the low melting point fine sphere particles (A ₂ ) is −40 ° C. or lower. , [2], [11] and [18] to [20].
[22] The above-mentioned [1], wherein the glass transition temperature (Tg _A1 ) and / or (Tg _A2 ) of the high-melting microsphere particles (A ₁ ) and / or the low-melting microsphere particles (A ₂ ) is −50 ° C. or lower. , [2], [11] and [18] to [21].
[23] The above [1], wherein the glass transition temperature (Tg _A1 ) and / or (Tg _A2 ) of the high melting point fine sphere particles (A ₁ ) and / or the low melting point fine sphere particles (A ₂ ) is −60 ° C. or less. , [2], [11] and [18] to [22].

[24] The above [ ₁ ], wherein the weight ratio of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ) is in the range of (A ₁ ) / (A ₂ ) = 20/80 to 80/20. ] Pressure-sensitive adhesive composition as described in any one of the above.
[25] The above [ ₁ ], wherein the weight ratio of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ) is in the range of (A ₁ ) / (A ₂ ) = 30/70 to 70/30. ] Or the pressure-sensitive adhesive composition according to [24].
[26] The above [ ₁ ], wherein the weight ratio of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ) is in the range of (A ₁ ) / (A ₂ ) = 40/60 to 60/40. ], [24] or [25].

[27] The above [1], [2], [11] and [18], wherein the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ) are obtained by aqueous suspension polymerization. [26] The pressure-sensitive adhesive composition according to any one of the above.
[28] The pressure-sensitive adhesive composition according to the above [27], wherein the aqueous suspension polymerization is performed in the presence of a surfactant substantially free from an alkylphenyl surfactant.

[29] The pressure-sensitive adhesive composition according to the above [1], wherein the fine particles (B) are formed of an acrylic (co) polymer.
[30] The pressure-sensitive adhesive composition according to [29], wherein the acrylic (co) polymer is composed of repeating units based on a monomer containing at least 50% by weight of a (meth) acrylic acid ester monomer. object.
[31] An acrylic (co) polymer has the following monomers (b ₁ ) to (b ₃ ):
(B ₁ ) represented by the general formula CH ₂ = CR ² COOR ³ (where R ² represents H or CH ₃ , and R ³ represents a linear or branched alkyl group having 4 to 12 carbon atoms) (meth) 50-100% by weight of acrylic ester monomer,
_{(B 2)} an unsaturated monomer 0 to 10% by weight having a carboxyl group, and _{(b 3)} the monomer _{(b 1)} and _{(b 2)} and copolymerizable, the monomer _{(b 1} ) and _{(b 2)} than the unsaturated monomer 0-50% by weight,
The pressure-sensitive adhesive composition according to the above [30], which is obtained by copolymerizing

[32] The above-mentioned [31], wherein the amount of the monomer (b ₁ ) used is in the range of 55 to 99.8% by weight based on the weight of the copolymer forming the fine particles (B). Pressure sensitive adhesive composition.
[33] The above [31] or [32], wherein the amount of the monomer (b ₁ ) used is in the range of 60 to 99.5% by weight, based on the weight of the copolymer forming the fine particles (B). ] Pressure-sensitive adhesive composition as described in any one of the above.

[34] The amount of the monomer (b ₂ ) used in the above [31], which is in the range of 0.2 to 5% by weight based on the weight of the copolymer that forms the fine particles (B). Pressure sensitive adhesive composition.
[35] The above [31] or [34], wherein the amount of the monomer (b ₂ ) used is in the range of 0.5 to 2% by weight based on the weight of the copolymer forming the fine particles (B). ] Pressure-sensitive adhesive composition as described in any one of the above.

[36] The pressure-sensitive adhesive composition according to the above [1] or [29], wherein the volume average particle diameter (d _B ) of the fine particles (B) is in the range of 50 to 900 nm.
[37] The pressure-sensitive adhesive composition according to the above [1], [29] or [36], wherein the volume average particle diameter (d _B ) of the fine particles (B) is in the range of 80 to 500 nm.
[38] The pressure-sensitive adhesive composition according to the above [1], [29], [36] or [37], wherein the volume average particle diameter (d _B ) of the fine particles (B) is in the range of 100 to 300 nm. .

[39] The glass transition temperature (Tg _B) is + 20 ° C. or less above the fine particles (B) [1], [ 29] and [36] - The pressure sensitive adhesive composition according to any one of [38] .
[40] The glass transition temperature (Tg _B) is less than -60 to + 15 ° C. of the microparticles (B) [1], [ 29] and [36] The pressure sensitive according to any one of - [39] Agent composition.
[41] The glass transition temperature (Tg _B) is less than -40 to + 10 ° C. of the microparticles (B) [1], [ 29] and [36] The pressure sensitive according to any one of - [40] Agent composition.

[42] The pressure-sensitive adhesive composition according to any one of [1], [29] and [36] to [41], wherein the fine particles (B) are obtained by aqueous emulsion polymerization.
[43] The pressure-sensitive adhesive composition according to [42], wherein the aqueous emulsion polymerization is performed in the presence of a surfactant substantially free from an alkylphenyl surfactant.

[44] The amount of the fine particles (B) used is in the range of 5 to 100 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure-sensitive adhesive composition according to the above [1].
[45] The amount of the fine particles (B) used is in the range of 10 to 50 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure-sensitive adhesive composition according to the above [1] or [44].
[46] The amount of the fine particles (B) used is in the range of 15 to 35 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure-sensitive adhesive composition according to the above [1], [44] or [45].

[47] The high melting point fine sphere particles (A ₁ ) are used as the total active ingredient amount of the ionic viscosity modifier (C ₁ ) and the nonionic viscosity modifier (C ₂ ) when the viscosity modifier (C) is used. The pressure-sensitive adhesive composition according to the above [1], which is in the range of 1 to 10 parts by weight with respect to a total of 100 parts by weight of the low melting point fine sphere particles (A ₂ ) and the fine particles (B).
[48] The high melting point fine sphere particles (A ₁ ) are used as the total active ingredient amount of the ionic viscosity modifier (C ₁ ) and the nonionic viscosity modifier (C ₂ ) when the viscosity modifier (C) is used. The pressure-sensitive adhesive according to [1] or [47], which is in the range of 2 to 8 parts by weight with respect to 100 parts by weight in total of the low melting point fine sphere particles (A ₂ ) and the fine particles (B). Composition.

[49] The use ratio of the ionic viscosity modifier (C ₁ ) and the nonionic viscosity modifier (C ₂ ) is expressed as: ionic viscosity modifier (C ₁ ) / nonionic viscosity modifier (C ₂ ) The pressure-sensitive adhesive composition according to [1], which is in a range of 90/10 to 20/80.
[50] The use ratio of the ionic viscosity modifier (C ₁ ) to the nonionic viscosity modifier (C ₂ ) is expressed as: ionic viscosity modifier (C ₁ ) / nonionic viscosity modifier (C ₂ ) The pressure-sensitive adhesive composition according to the above [1] or [49], which is in the range of 70/30 to 40/60.
[51] The pressure-sensitive adhesive composition according to any one of [1] and [47] to [50], wherein the ionic viscosity modifier (C ₁ ) is a polycarboxylic acid type viscosity modifier.

[52] The pressure-sensitive adhesive composition according to any one of [1] and [47] to [50], wherein the nonionic viscosity modifier (C ₂ ) is a urethane-modified polyether type viscosity modifier.

[53] The pressure-sensitive adhesive composition according to the above [1], wherein the aqueous pressure-sensitive adhesive composition further contains a tackifier (D).
[54] The pressure-sensitive adhesive composition according to the above [1] or [53], wherein the tackifier (D) is a petroleum resin, a rosin resin, or a terpene resin.

[55] The pressure-sensitive adhesive composition according to the above [1], [53] or [54], wherein the softening point of the tackifier (D) is in the range of 70 to 180 ° C.
[56] The pressure-sensitive adhesive composition according to any one of [1] and [53] to [55] above, wherein the softening point of the tackifier (D) is in the range of 100 to 160 ° C.
[57] The pressure-sensitive adhesive composition according to any one of [1] and [53] to [56], wherein the softening point of the tackifier (D) is in the range of 120 to 150 ° C.

[58] The pressure-sensitive adhesive composition according to any one of [1] and [53] to [57], wherein the tackifier (D) has a weight average molecular weight (Mw) of 5000 or less.
[59] The pressure-sensitive adhesive composition according to any one of the above [1] and [53] to [58], wherein the weight average molecular weight (Mw) of the tackifier (D) is in the range of 2000 to 4000.

[60] The pressure-sensitive adhesive composition according to the above [1] or [53], wherein the tackifier (D) can be stably dispersed in an aqueous medium.
[61] The pressure-sensitive adhesive composition according to the above [1], [53] or [60], wherein the tackifier (D) has an average particle size of 400 nm or less.
[61] The pressure-sensitive adhesive composition according to the above [1], [53] or [60], wherein the tackifier (D) has an average particle size in the range of 50 to 350 nm.
[62] The pressure-sensitive adhesive composition according to the above [1], [53], [60] or [61], wherein the tackifier (D) does not substantially contain an alkylphenyl surfactant.

[63] The content of the tackifier (D) is 0.1 to 25 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure-sensitive adhesive composition according to [53], which is in a range.
[64] The content of the tackifier (D) is 0.5 to 20 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure-sensitive adhesive composition according to the above [53] or [63], which is a range.
[65] The content of the tackifier (D) is in the range of 1 to 15 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). A pressure-sensitive adhesive composition according to the above [53], [63] or [64].
[66] The content of the tackifier (D) is in the range of 2 to 10 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure-sensitive adhesive composition according to any one of the above [53] and [63] to [65].

[67] The pressure-sensitive adhesive composition according to [1], wherein the aqueous pressure-sensitive adhesive composition further contains a crosslinking agent (E).
[68] The pressure-sensitive adhesive composition according to [67], wherein the crosslinking agent (E) is a compound containing a carbodiimide group in the molecule.

[69] The functional group in the crosslinking agent (E) is used in the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the acrylic copolymer fine particles (B). The pressure-sensitive adhesive composition according to the above [67] or [68], which is in the range of 0.2 to 1.5 equivalents per 1 equivalent in total.
[70] The functional group in the crosslinking agent (E) is used in the high melting point fine sphere particles (A ₁ ), the low melting point fine sphere particles (A ₂ ) and / or the acrylic copolymer fine particles (B). The pressure-sensitive adhesive composition according to any one of the above [67] to [69], which is in the range of 0.4 to 1 equivalent per 1 equivalent of the total.

[71] The pressure-sensitive adhesive composition according to the above [1], wherein the aqueous pressure-sensitive adhesive composition does not substantially contain an alkylphenyl surfactant.
[72] The pressure-sensitive adhesive composition according to the above [1], wherein the aqueous pressure-sensitive adhesive composition is used for producing a pressure-sensitive adhesive sheet by a transfer coating method.
[73] The pressure-sensitive adhesive composition according to any one of [1] to [72], wherein the pressure-sensitive adhesive composition is a re-peelable pressure-sensitive adhesive composition.

[74] Including an adhesive microsphere particle (A) having a volume average particle diameter (d _A ) of 1 μm or more, a fine particle (B) having a volume average particle diameter (d _B ) of less than 1 μm, and a viscosity modifier (C). In the method for producing a pressure-sensitive adhesive sheet using the aqueous pressure-sensitive adhesive composition, the method comprises the following steps:
(1) The aqueous pressure-sensitive adhesive composition according to any one of the above [1] to [73] is applied onto a release material whose surface has been release-treated,
(2) The object to be coated on the release material is dried at a temperature of 60 ° C. or higher, and is not yet put in the binder layer containing the molten low melting point fine sphere particles (A ₂ ) and the formed fine particles (B). The molten high melting point microsphere particles (A ₁ ) are dispersed and fixed to form a pressure-sensitive adhesive layer having a large number of low hill-like irregularities on the surface, and (3) the resulting pressure sensitive Pressurizing the base material on the adhesive layer and transferring the pressure-sensitive adhesive layer on the base material;
The manufacturing method characterized by comprising.

[75] A pressure-sensitive adhesive sheet having a large number of low hill-like irregularities on the surface of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is water-based as described in any one of [1] to [73]. A pressure-sensitive adhesive sheet formed by using a pressure-sensitive adhesive composition or formed by the production method according to [74] above.

[76] The pressure-sensitive adhesive sheet according to the above [75], wherein the low hill-shaped unevenness includes molten low melting point fine sphere particles (A ₂ ) and undissolved high melting point fine sphere particles (A ₁ ).

  The water-based pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive sheet having good adhesion to an adherend having a smooth surface or a rough surface, such as paper, metal and plastics. It can be used for production, and can be suitably used for production of a re-peelable pressure-sensitive adhesive sheet that can be re-peeled without any adhesive residue and can be repeatedly stuck and peeled.

  The pressure-sensitive adhesive sheet formed using the water-based pressure-sensitive adhesive composition of the present invention has conventionally used a non-tacky microsphere particle type solvent-type pressure-sensitive adhesive or an aqueous dispersion-type pressure-sensitive adhesive. It can be used up to the so-called “medium-adhesion” region where higher adhesion is required.

In particular, the aqueous pressure-sensitive adhesive composition of the present invention can be used for the production of a pressure-sensitive adhesive sheet by a transfer method, which is difficult with a pressure-sensitive adhesive composition containing ordinary adhesive microsphere particles. The obtained pressure-sensitive adhesive sheet is excellent not only in adhesion to the substrate but also in adhesion to the adherend, removability, and repeatability of sticking and peeling.

Claims (15)

The volume average particle diameter _(d A) is 1μm or more adhesive fine spherical particles (A), the volume average particle diameter _(d B) is less than 1μm fine particles (B), and include the viscosity modifier and (C) In the aqueous pressure-sensitive adhesive composition, the adhesive microsphere particles (A) and the microparticles (B) are each based on a monomer containing 50% by weight or more of a (meth) acrylate monomer. It is an acrylic (co) polymer composed of units, and the adhesive microsphere particles (A) are at least one high melting point microsphere particle (A ₁ ) having a melting temperature higher than 60 ° C., and a melting temperature. There consists of at least one 60 ° C. or less of the low-melting fine spherical particles (a _2), and viscous modifier (C) is an ionic viscosity modifier (C ₁₎ at least one, and nonionic becomes viscous adjusting agent (C ₂₎ at least one and, the ionic viscosity The pressure-sensitive adhesive composition is characterized in that the property modifier (C ₁ ) is a polycarboxylic acid type viscosity modifier and the nonionic viscosity modifier (C ₂ ) is a urethane-modified polyether type viscosity modifier. . The volume average particle diameter (d _A1 ) of the high melting point fine sphere particles (A ₁ ) and / or the volume average particle diameter (d _A2 ) of the low melting point fine sphere particles (A ₂ ) is in the range of 1 to 60 μm. The pressure-sensitive adhesive composition described in 1. The glass transition temperature of the high-melting fine spherical particles _{(A 1) (T} gA1) and / or to claim 1 or 2 glass transition temperature of the low-melting fine spherical particles _{(A 2) (T} gA2) is -40 ℃ or less The pressure-sensitive adhesive composition as described. The weight ratio of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ) is in the range of (A ₁ ) / (A ₂ ) = 20/80 to 80/20 . The pressure-sensitive adhesive composition according to any one of the above. Refractory fine spherical particles (A ₁₎ and the low-melting fine spherical particles (A ₂₎ is a pressure sensitive adhesive composition according to any one of claims 1 to 4 is obtained by aqueous suspension polymerization. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the volume average particle diameter (d _B ) of the fine particles (B) is in the range of 50 to 900 nm. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the glass transition temperature ( _TgB ) of the fine particles (B) is + 20 ° C or lower. The pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the fine particles (B) are obtained by aqueous emulsion polymerization. The amount of fine particles (B) is, per 100 parts by weight of high-melting fine spherical particles _{(A 1)} and the low-melting fine spherical particles _{(A 2),} according to claim 1 in the range of 5 to 100 parts by weight The pressure-sensitive adhesive composition according to any one of -8 . The amount of viscosity modifier (C) is, as the total amount of active ingredient of the ionic viscosity modifier (C ₁₎ and a non-ionic viscosity modifier (C _2), high melting fine spherical particles (A ₁₎ and low melting point The pressure-sensitive adhesive composition according to any one of claims 1 to 9, which is in a range of 1 to 10 parts by weight with respect to a total of 100 parts by weight of the fine sphere particles (A ₂ ) and the fine particles (B). object. The ratio of use of the ionic viscosity modifier (C ₁ ) and the nonionic viscosity modifier (C ₂ ) is 90/90 as ionic viscosity modifier (C ₁ ) / nonionic viscosity modifier (C ₂ ). It is the range of 10-20 / 80, The pressure sensitive adhesive composition as described in any one of Claims 1-10 . The pressure-sensitive adhesive according to any one of claims 1 to 11, wherein the aqueous pressure-sensitive adhesive composition further contains any one of a petroleum resin, a rosin resin, and a terpene resin as a tackifier (D). Adhesive composition. The content of the tackifier (D) is in the range of 0.1 to 25 parts by weight with respect to a total of 100 parts by weight of the high melting point fine sphere particles (A ₁ ) and the low melting point fine sphere particles (A ₂ ). The pressure sensitive adhesive composition according to claim 12 . The pressure-sensitive adhesive composition according to any one of claims 1 to 13, wherein the aqueous pressure-sensitive adhesive composition further contains a crosslinking agent (E). The pressure-sensitive adhesive composition according to claim 14 , wherein the crosslinking agent (E) is a compound containing a carbodiimide group in the molecule.