JP5751905B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet that can be re-peeled. More specifically, the present invention relates to a pressure-sensitive adhesive sheet that is excellent in appearance characteristics and that is excellent in prevention of an increase in adhesive strength over time, scratch resistance, and antistatic properties and that can be removed again.

  In the manufacturing and processing process of optical members (optical materials) including optical films such as polarizing plates, retardation plates, and antireflection plates, for the purpose of preventing scratches and dirt on the surface, improving cutting workability, and suppressing cracks A surface protective film is used by being attached to the surface of an optical member (see Patent Documents 1 and 2). As these surface protective films, a removable pressure-sensitive adhesive sheet in which a removable pressure-sensitive adhesive layer is provided on the surface of a plastic film substrate is generally used.

  Conventionally, solvent-based acrylic pressure-sensitive adhesives have been used for these surface protective film applications as pressure-sensitive adhesives for forming the pressure-sensitive adhesive layer (see Patent Documents 1 and 2). Since it contains an organic solvent, conversion to a water-dispersed acrylic pressure-sensitive adhesive is attempted from the viewpoint of work environment at the time of coating (see Patent Documents 3 to 5).

  These surface protective films are required to exhibit sufficient adhesiveness while being attached to the optical member. Furthermore, since it peels after using in the manufacturing process of an optical member, etc., the outstanding peelability (removability) is calculated | required. In order to have excellent re-peelability, in addition to having a small peel force (light peel), the adhesive force (peel force) does not easily increase over time after being attached to an adherend such as an optical member. (Adhesion strength preventing property) is required.

  In order to obtain characteristics such as light peeling and prevention of increase in adhesive strength, it is effective to use a water-insoluble crosslinking agent for the adhesive (or adhesive composition) forming the adhesive layer. As a pressure-sensitive adhesive composition using a water-insoluble crosslinking agent, for example, a re-peeling water-dispersed acrylic pressure-sensitive adhesive composition containing an oil-soluble crosslinking agent is known (see Patent Documents 6 and 7).

  However, like the above-mentioned pressure-sensitive adhesive composition, the water-dispersed acrylic pressure-sensitive adhesive composition using a water-insoluble crosslinking agent does not sufficiently disperse large particles of the water-insoluble crosslinking agent in the pressure-sensitive adhesive composition. Due to this, when forming the pressure-sensitive adhesive layer, appearance defects such as “dents” are likely to occur on the surface of the pressure-sensitive adhesive layer. For this reason, particularly when using a water-insoluble crosslinking agent for the pressure-sensitive adhesive layer of the surface protective film, there may be a problem that it becomes difficult to inspect the adherend while the surface protective film is stuck. . In order to eliminate the dent caused by such a water-insoluble crosslinking agent, for example, a leveling agent is used.

  A water-dispersed acrylic pressure-sensitive adhesive composition generally has poor antifoaming properties when it contains a surfactant such as the leveling agent or emulsifier. If air bubbles are included in the coating liquid during the formation of the pressure-sensitive adhesive layer, the air bubbles remain in the pressure-sensitive adhesive layer formed by application by the coating head, forming a dent on the surface of the pressure-sensitive adhesive layer, and the appearance of the pressure-sensitive adhesive layer This causes problems such as deterioration of the thickness of the pressure-sensitive adhesive layer, variation in the thickness of the pressure-sensitive adhesive layer, and residual bubble defects after drying of the pressure-sensitive adhesive layer. In order to improve antifoaming properties, it is effective to use an antifoaming agent. However, problems such as repellency due to the addition of an antifoaming agent, and when a solid nucleating agent such as silica is included as an antifoaming agent, the nucleating agent becomes a foreign substance and the coating appearance is deteriorated.

  Therefore, a pressure-sensitive adhesive formed from a water-dispersed acrylic pressure-sensitive adhesive composition, which has excellent adhesiveness and removability (particularly an anti-adhesive property), and has reduced appearance defects such as “dents” and has excellent appearance characteristics. The layer is not obtained at present.

  Furthermore, in surface protective film applications (especially for optical member surface protective film applications), adhesive residue (so-called “glue residue”) remains on the surface of the adherend (optical member, etc.) when the adhesive sheet is peeled off. Contamination of the adherend surface due to transfer of components contained in the adhesive layer to the adherend surface causes problems such as an adverse effect on the optical characteristics of the optical member. For this reason, the low adhesiveness with respect to a to-be-adhered body is strongly calculated | required by the adhesive and the adhesive layer.

Japanese Patent Laid-Open No. 11-961 JP 2001-64607 A JP 2001-131512 A JP 2003-27026 A Japanese Patent No. 3810490 JP 2004-91563 A JP 2006-169596 A

  On the other hand, in surface protection film applications, there is a demand for characteristics (sometimes referred to as “scratch resistance”) that the surface (substrate surface) is less likely to be scratched. If there is a scratch on the surface of the surface protective film (base material surface), it is difficult to determine whether such a scratch is on the surface protective film or on an adherend (such as an optical member) that is the subject of visual inspection. It is. Improves scratch resistance of the surface of the surface protective film, that is, the surface opposite to the surface (adhesive layer surface) to be attached to the adherend (surface of the base material side, sometimes referred to as “rear surface”) Examples of the technique include a technique of providing a hard surface layer (topcoat layer) on the back surface of the surface protective film.

  However, when the top coat layer is provided on the back surface of the surface protective film, the surface protective film affixed to the adherend is observed from the back side (for example, observed in a bright room where external light enters or under a fluorescent lamp in the bright room) Then, the external appearance of the surface protection film looks entirely or partially whitish, thereby causing a problem that visibility of the adherend surface is lowered. Furthermore, when the thickness of the topcoat layer varies, the reflectance varies depending on the location, and the thick portion looks relatively white, thereby further reducing the visibility of the adherend surface.

  Accordingly, there is a need for a surface protective film having a top coat layer exhibiting excellent scratch resistance on the back surface (base material surface), and which does not look entirely or partially whitish but exhibits an excellent appearance.

  In addition, when surface protective films are used in the processing or transporting of articles that dislike static electricity such as liquid crystal cells and semiconductor devices, these surface protective films are difficult to be charged (antistatic properties). Sex) is also required.

  Therefore, an object of the present invention is to have an acrylic pressure-sensitive adhesive layer on at least one side of a transparent film substrate having a topcoat layer, and to reduce appearance characteristics (such as dents and bubble defects). In addition, the present invention is to provide a pressure-sensitive adhesive sheet that is excellent in that it is difficult to look whitish), and that is also excellent in prevention of an increase in adhesive strength over time, scratch resistance, and antistatic properties.

  As a result of intensive studies to achieve the above object, the present inventors have found that a raw material monomer having a specific composition is provided on at least one side of a transparent film substrate having a topcoat layer having a specific configuration in which variation in average thickness and thickness is controlled. And a water-dispersed acrylic pressure-sensitive adhesive composition comprising a specific structure of polypropylene glycol (PPG) / polyethylene glycol (PEG) block copolymer (or a derivative thereof) as a constituent component By finding a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet has excellent scratch resistance and antistatic properties, and is further excellent in appearance characteristics and adhesive strength rise prevention. Completed the invention.

That is, the present invention is a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer on at least one side of a transparent film substrate, wherein the transparent film substrate comprises a base layer made of a resin material, and a first surface of the base layer A topcoat layer provided on the topcoat layer, the topcoat layer being composed of polythiophene, an acrylic resin, and a melamine-based crosslinking agent, an average thickness _Dave of 2 to 50 nm, and a thickness variation ΔD of 40% or less And the acrylic pressure-sensitive adhesive layer is composed of (meth) acrylic acid alkyl ester and carboxyl group-containing unsaturated monomer as essential raw material monomers, and contains (meth) acrylic acid alkyl ester in the total amount of raw material monomers. The amount is 70 to 99.5% by weight, the content of the carboxyl group-containing unsaturated monomer is 0.5 to 10% by weight, and the radical weight in the molecule is Re-peeling water-dispersed acrylic pressure-sensitive adhesive composition containing an acrylic emulsion polymer (A) polymerized using a reactive emulsifier containing a functional functional group and a compound (B) represented by the following formula (I) The present invention provides a pressure-sensitive adhesive sheet, which is a pressure-sensitive adhesive layer formed more.
_{^{R 1 O- (PO) a -}} (EO) b - (PO) c -R 2 (I)
(Wherein R ¹ and R ² represent a linear or branched alkyl group or a hydrogen atom. PO represents an oxypropylene group, EO represents an oxyethylene group. A, b and c are (Each is a positive integer. The addition form of EO and PO is a block type.)

  Furthermore, the pressure-sensitive adhesive sheet is provided in which the resin material constituting the base layer contains polyethylene terephthalate or polyethylene naphthalate as a main resin component.

  Furthermore, the water-removable acrylic pressure-sensitive adhesive composition for re-peeling provides the pressure-sensitive adhesive sheet further comprising a water-insoluble crosslinking agent (C) having two or more functional groups capable of reacting with carboxyl groups in the molecule. .

  Furthermore, the said adhesive sheet which is a surface protection film for optical members is provided.

  Since the pressure-sensitive adhesive sheet of the present invention has the above-mentioned transparent film substrate, it is excellent in scratch resistance and antistatic properties, and is difficult to look whitish. In addition, since the pressure-sensitive adhesive sheet of the present invention has the above acrylic pressure-sensitive adhesive layer, there are few appearance defects such as dents and bubble defects, and it has good removability and adhesiveness, particularly for adherends. Adhesive strength hardly increases over time. As described above, the pressure-sensitive adhesive sheet of the present invention has particularly excellent appearance characteristics by having the above-described configuration, and performs an appearance inspection of the adherend while it is still attached to the adherend (such as an optical member). It is easy and inspection accuracy can be improved. For this reason, the pressure-sensitive adhesive sheet of the present invention is particularly useful for surface protection of optical films.

  The pressure-sensitive adhesive sheet of the present invention has an acrylic pressure-sensitive adhesive layer on at least one side of the transparent film substrate. In the present specification, the term “adhesive sheet” includes a tape-shaped material, that is, an “adhesive tape”. The surface of the pressure-sensitive adhesive layer (acrylic pressure-sensitive adhesive layer) of the pressure-sensitive adhesive sheet of the present invention may be referred to as “pressure-sensitive adhesive surface”.

  The pressure-sensitive adhesive sheet of the present invention may be a double-sided pressure-sensitive adhesive sheet whose both surfaces are pressure-sensitive adhesive surfaces, or a single-sided pressure-sensitive adhesive sheet in which only one surface is a pressure-sensitive adhesive surface. Especially, it is preferable that it is a single-sided adhesive sheet from a viewpoint of protecting the surface of a to-be-adhered body. That is, the pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) having an acrylic pressure-sensitive adhesive layer on one side of the transparent film substrate. In particular, from the viewpoint of antistatic properties, the pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) preferably has a configuration in which one surface is a surface of a top coat layer described later and the other surface is a pressure-sensitive adhesive surface.

[Transparent film substrate]
The transparent film base material in the adhesive sheet of this invention has at least the base layer which consists of resin materials, and the below-mentioned topcoat layer provided on the 1st surface of this base layer. The transparent film substrate may have a configuration (laminated configuration) having the top coat layer only on one surface (first surface) side of the base layer, or both surfaces of the base layer (first surface and The structure (lamination structure) which has the said topcoat layer in the 2nd surface) side may be sufficient. Especially, it is preferable that the said transparent film base material is the structure (lamination structure of a "base layer / topcoat layer") which has the said topcoat layer only in the one surface (1st surface) side of the said base layer.

[Base layer]
The base layer of the transparent film substrate is a transparent film (thin film) molded body made of a resin material. That is, as the base layer, a resin film formed by molding various resin materials into a film shape can be preferably used. Although it does not specifically limit as a resin material which comprises the said base layer, The resin film excellent in the characteristic of 1 or 2 or more among transparency, mechanical strength, thermal stability, moisture shielding property, and isotropic property etc. More specifically, for example, polyester polymers such as polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate; cellulose polymers such as diacetyl cellulose and triacetyl cellulose; polycarbonate polymers A resin material comprising an acrylic polymer such as polymethyl methacrylate as the main component (resin component) (a component occupying 50% by weight or more of the main component of the resin material, eg, 100% by weight of the resin material), More preferably polyethylene terephthalate or polyethylene The naphthalate is a resin material whose main component. Examples of the resin material include styrene polymers such as polystyrene and acrylonitrile-styrene copolymers; olefin polymers such as polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, and ethylene-propylene copolymers; vinyl chloride. Amide polymers such as nylon 6, nylon 6,6, aromatic polyamide; imide polymers; sulfone polymers; polyethersulfone polymers; polyetheretherketone polymers; polyphenylene sulfide polymers; polyvinyl alcohol polymers Polyoxymethylene polymers; epoxy polymers and the like can also be used. The base layer may be formed from a blend of two or more of the polymers. The base layer is more preferable as the anisotropy of optical properties (such as retardation) is smaller. In particular, in the application of a surface protective film for an optical member, it is beneficial to reduce the optical anisotropy of the base layer. The base layer may have a single layer structure or a structure in which a plurality of layers having different compositions are stacked. Especially, it is preferable that the said base layer is a single layer structure.

  The base layer may contain various additives such as an antioxidant, an ultraviolet absorber, an antistatic component, a plasticizer, and a colorant (pigment, dye, etc.) as necessary.

  For example, corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer are applied to the first surface of the base layer (the surface on which the topcoat layer is provided). Surface treatment may be performed. Such surface treatment is performed, for example, for the purpose of enhancing the adhesion between the base layer and the topcoat layer, and in particular, polar groups such as hydroxyl groups (—OH groups) are present on the first surface of the base layer. Surface treatment as introduced is preferably employed.

  Also, the same surface treatment as described above may be applied to the second surface of the base layer (usually the surface on which the acrylic pressure-sensitive adhesive layer is formed). Such surface treatment is performed, for example, for the purpose of improving the adhesion between the transparent film substrate and the acrylic pressure-sensitive adhesive layer (the anchoring property of the acrylic pressure-sensitive adhesive layer).

  The thickness of the base layer can be appropriately selected according to the application and purpose, and is not particularly limited, but is 10 to 200 μm in view of workability such as strength and handleability and cost and appearance inspection properties. More preferably, it is 15-100 micrometers, More preferably, it is 20-70 micrometers.

  Although the refractive index of the said base layer is not specifically limited, 1.43-1.6 are preferable from a viewpoint of an external appearance characteristic, More preferably, it is 1.45-1.5.

  The total light transmittance in the visible light wavelength region of the base layer (according to JIS K7361-1) is not particularly limited, but is preferably 80 to 97%, more preferably 85 to 95% from the viewpoint of appearance characteristics. .

  The arithmetic average roughness (Ra) of the surface of the base layer is not particularly limited. For example, the arithmetic average roughness of the second surface (usually the surface on which the acrylic pressure-sensitive adhesive layer is formed) is 0. It is preferable that it is 001-1 micrometer, More preferably, it is 0.01-0.7 micrometer. When the arithmetic average roughness of the second surface exceeds 1 μm, the acrylic pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present invention has a high solvent-insoluble content, and thus the thickness accuracy of the coated surface (glue surface) decreases. In some cases, the pressure-sensitive adhesive does not penetrate into the irregularities on the surface of the transparent film substrate and the contact area is reduced, so that the anchoring property between the acrylic pressure-sensitive adhesive layer and the transparent film substrate is lowered. On the other hand, when the arithmetic average roughness is less than 0.001 μm, blocking may easily occur, handling properties may decrease, and industrial production may be difficult.

[Topcoat layer]
The topcoat layer of the transparent film substrate in the pressure-sensitive adhesive sheet of the present invention is a surface layer formed on at least the first surface side of the base layer, and contains at least polythiophene, an acrylic resin, and a melamine-based crosslinking agent as essential components. Composed. By having the top coat layer, the pressure-sensitive adhesive sheet of the present invention can exhibit various functions such as scratch resistance, antistatic property, solvent resistance, printability, and print adhesion. In the case where the pressure-sensitive adhesive sheet of the present invention has the above functions, it can be preferably used particularly for surface protection of optical films.

  The acrylic resin in the topcoat layer is a basic component (base resin) that contributes to the formation of the topcoat layer, and the acrylic polymer is a base polymer (main component in the polymer component, that is, 50% by weight or more). A resin contained as a component). That is, the content of the acrylic polymer in the acrylic resin (100% by weight) is 50% by weight or more (for example, 50 to 100% by weight), preferably 70 to 100% by weight, more preferably 90 to 100%. % By weight.

  The above “acrylic polymer” is a polymer containing a monomer having at least one (meth) acryloyl group in one molecule (inside the molecule) (hereinafter sometimes referred to as “acrylic monomer”) as a main monomer component. Say. That is, of the total amount (100% by weight) of monomer components constituting the acrylic polymer, the acrylic monomer content is 50% by weight or more. In the present specification, “(meth) acryloyl group” means an acryloyl group and / or a methacryloyl group (one or both of an acryloyl group and a methacryloyl group).

  Although it does not specifically limit as said acrylic resin, For example, various types of acrylic resins, such as a thermosetting acrylic resin, an ultraviolet curable acrylic resin, an electron beam curable acrylic resin, a two-component mixed acrylic resin, etc. can be used. The above-mentioned various types of acrylic resins can be used alone or in combination of two or more. Among them, acrylic having excellent scratch resistance (for example, the result of evaluation of scratch resistance in the section “(Evaluation)” described later is good (◯)) and capable of forming a top coat layer having excellent light transmittance. It is preferable to select a resin. The acrylic resin can be grasped as a binder (binder resin) of polythiophene (antistatic component) in the top coat layer.

  The acrylic polymer that is the base polymer of the acrylic resin is not particularly limited, but is preferably an acrylic polymer containing methyl methacrylate (MMA) as a main monomer component (monomer component), more preferably, It is a copolymer of methyl methacrylate and one or more other monomers (preferably acrylic monomers other than methyl methacrylate). The copolymerization ratio of methyl methacrylate in the acrylic polymer is not particularly limited, but is 50% by weight or more (for example, 50 to 90% by weight) with respect to the total amount of monomer components (100% by weight) constituting the acrylic polymer. And more preferably 60% by weight or more (for example, 60 to 85% by weight).

  In the acrylic polymer, the monomer copolymerized with methyl methacrylate is not particularly limited, and examples thereof include (meth) acrylic acid alkyl esters other than methyl methacrylate, and more specifically, for example, (Meth) acrylic acid alkyl ester having a linear or branched alkyl group, (meth) acrylic acid alkyl ester (cycloalkyl (meth) acrylate) having an alicyclic alkyl group (cycloalkyl group), etc. Is preferably exemplified.

  Although it does not specifically limit as said (meth) acrylic-acid alkylester which has the said linear or branched alkyl group, For example, methyl acrylate, ethyl acrylate, acrylic acid n-butyl (BA), acrylic acid 2 -An alkyl acrylate having 1 to 12 carbon atoms (alkyl acrylate ester) such as ethylhexyl (2EHA); an alkyl group such as ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate Examples thereof include alkyl methacrylate having 2 to 6 carbon atoms (methacrylic acid alkyl ester). In addition, the (meth) acrylic acid alkyl ester having an alicyclic alkyl group is not particularly limited. For example, an acryl group having 5 to 7 carbon atoms in a cycloalkyl group such as cyclopentyl acrylate and cyclohexyl acrylate. Cycloalkyl; cycloalkyl methacrylate having 5 to 7 carbon atoms in the cycloalkyl group such as cyclopentyl methacrylate and cyclohexyl methacrylate (CHMA).

  Preferable specific embodiments of the acrylic polymer include, for example, an acrylic polymer composed of monomer components including at least methyl methacrylate (MMA) and cyclohexyl methacrylate (CHMA). In this case, the copolymerization ratio of cyclohexyl methacrylate is not particularly limited. For example, it is 25% by weight or less (for example, 0.1 to 25% by weight) with respect to the total amount of monomer components (100% by weight) constituting the acrylic polymer. ), And more preferably 15% by weight or less (for example, 0.1 to 15% by weight).

  Other preferable specific embodiments of the acrylic polymer include, for example, methyl methacrylate (MMA) and a monomer component containing at least n-butyl acrylate (BA) and / or 2-ethylhexyl acrylate (2EHA). The acrylic polymer comprised is mentioned. In this case, the copolymerization ratio of n-butyl acrylate and 2-ethylhexyl acrylate (when both are included, the total amount thereof) is not particularly limited. For example, the total amount of monomer components constituting the acrylic polymer ( 100% by weight) is preferably 40% by weight or less (for example, 1 to 40% by weight), more preferably 10 to 40% by weight, still more preferably 30% by weight or less (for example, 3 to 30% by weight). Preferably it is 15-30 weight%.

  Particularly preferred specific embodiments of the acrylic polymer include, for example, substantially methyl methacrylate (MMA), cyclohexyl methacrylate (CHMA), and n-butyl acrylate (BA) and / or acrylic acid 2- An acrylic polymer composed of a monomer component composed of ethylhexyl (2EHA) is exemplified. Specifically, it is composed of MMA, CHMA, and monomer components containing BA and / or 2EHA, and MMA, CHMA, BA, and 2EHA with respect to the total amount of monomer components (100% by weight) constituting the acrylic polymer. An acrylic polymer having a total content (total content) of 52% by weight or more is preferred.

  The acrylic polymer may be copolymerized with a monomer other than the above (other monomers) as long as the effects of the present invention are not significantly impaired. Examples of other monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; vinyl acetate and propionic acid. Vinyl esters such as vinyl; aromatic vinyl compounds such as styrene and α-methylstyrene; amide group-containing monomers such as acrylamide and N, N-dimethylacrylamide; aminoethyl (meth) acrylate, (meth) acrylic acid N, Amino group-containing monomers such as N-dimethylaminoethyl; imide group-containing monomers such as cyclohexylmaleimide; epoxy-group-containing monomers such as glycidyl (meth) acrylate; vinyl ethers such as (meth) acryloylmorpholine; methyl vinyl ether; Meta Acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate And hydroxyl group-containing monomers such as (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, vinyl alcohol, allyl alcohol, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. The copolymerization ratio of these “other monomers” (the total amount when two or more are used) is not particularly limited, but is preferably 20% by weight or less, more preferably 10% by weight or less, and still more preferably 5%. % By weight or less, most preferably 3% by weight or less. The “other monomer” may not be substantially copolymerized. For example, the content of the other monomer is 0.1% with respect to the total amount of monomers (100% by weight) constituting the acrylic polymer. It may be not more than% by weight.

  It is preferable that the acrylic polymer has a copolymer composition that does not substantially contain a monomer having an acidic functional group (for example, acrylic acid or methacrylic acid). Specifically, the content of the monomer having an acidic functional group is preferably 0.1% by weight or less with respect to the total amount of monomer components constituting the acrylic polymer. As a constituent of the top coat layer, by using a combination of an acrylic polymer substantially free of monomers having the acidic functional group and a melamine crosslinking agent, the hardness of the top coat layer can be increased, And it exists in the tendency which can improve the adhesiveness with respect to the base layer of a topcoat layer. In the present specification, the “acidic functional group” means a functional group capable of exhibiting acidity such as a carboxyl group and an acid anhydride group, and the same applies to the following.

  The acrylic polymer is preferably a copolymer composition containing a monomer having a hydroxyl group (hydroxyl group-containing monomer). By copolymerizing the hydroxyl group-containing monomer, the adhesion of the topcoat layer to the base layer can be enhanced.

  The acrylic resin constituting the top coat layer may contain other resin components (excluding polythiophene) in addition to the acrylic polymer. In addition, content of the said other resin component in the said acrylic resin (100 weight%) is less than 50 weight%.

  The polythiophene in the top coat layer is a component (antistatic component) having an action of preventing charging of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive sheet of the present invention exhibits excellent antistatic properties by including polythiophene in the topcoat layer, so that the surface is used in the processing or transporting process of articles that dislike static electricity such as liquid crystal cells and semiconductor devices. It can be particularly preferably used as a protective film.

  Furthermore, since the polythiophene has high hydrophobicity and hardly absorbs moisture in a high humidity environment (humidified), it does not easily cause whitening of the transparent film substrate (more specifically, whitening of the topcoat layer). On the other hand, when a highly hygroscopic component (for example, an ammonium salt) is used as the antistatic component of the topcoat layer, the whitening of the substrate (more specifically, the topcoat layer) Whitening) is likely to occur.

  Examples of the polythiophene include, in addition to unsubstituted thiophene polymers, substituted thiophene polymers such as 3,4-ethylenedioxythiophene. Among these, from the viewpoint of antistatic properties, the polythiophene is preferably poly (3,4-ethylenedioxythiophene), which is a polymer of 3,4-ethylenedioxythiophene.

The polystyrene equivalent weight average molecular weight (Mw) of the polythiophene is not particularly limited, but is preferably 40 × 10 ⁴ or less (eg, 0.1 × 10 ⁴ to 40 × 10 ⁴ ), more preferably 0.5 × 10. ⁴ to 30 × 10 ⁴ or less. When the Mw of the polythiophene exceeds 40 × 10 ⁴ , the compatibility may be insufficient depending on the combination with other components constituting the top coat layer, resulting in a decrease in appearance characteristics or a decrease in solvent resistance. On the other hand, if the Mw of the polythiophene is less than 0.1 × 10 ⁴ , the scratch resistance may be inferior.

Although the usage-amount (content in a topcoat layer) of the said polythiophene is not specifically limited, 10-200 weight part is preferable with respect to 100 weight part of acrylic polymers in a topcoat layer, More preferably, it is 25-150. Part by weight, more preferably 40 to 120 parts by weight. If the amount used is less than 10 parts by weight, the surface resistivity of the surface of the transparent film base on the topcoat layer side becomes too large, and the antistatic property may be lowered. On the other hand, if the amount used exceeds 200 parts by weight, the thickness variation ΔD of the topcoat layer tends to increase, and the pressure-sensitive adhesive sheet may appear partially whitish and the appearance characteristics may deteriorate. Further, depending on the combination with other components constituting the top coat layer, the compatibility of polythiophene may be insufficient, resulting in a decrease in appearance characteristics and a decrease in solvent resistance.

As a method of forming the topcoat layer, as described later, when a method of applying a liquid composition (coating composition for forming the topcoat layer) to the surface of the base layer and drying or curing the composition is used, As the polythiophene used for preparing the product, a polythiophene in which the polythiophene is dissolved or dispersed in water (polythiophene aqueous solution or dispersion) can be preferably used. Such a polythiophene aqueous solution or dispersion is obtained by, for example, dissolving or dispersing a polythiophene having a hydrophilic functional group (which can be synthesized by a method such as copolymerizing a monomer having a hydrophilic functional group in the molecule) in water. Can be prepared. Examples of the hydrophilic functional group include a sulfo group, an amino group, an amide group, an imino group, a hydroxyl group, a mercapto group, a hydrazino group, a carboxyl group, a quaternary ammonium group, and a sulfate ester group (—O—SO ₃ H). And phosphate ester groups (for example, —O—PO (OH) ₂ ) and the like. These hydrophilic functional groups may form a salt. As the polythiophene aqueous solution, a commercial product such as a trade name “Denatron” series (manufactured by Nagase ChemteX Corporation) can be used.

  Among the polythiophene aqueous solutions, a polythiophene aqueous solution containing polystyrene sulfonate (PSS) (which may be in a form in which PSS is added as a dopant to polythiophene) is particularly preferable in that stable charging characteristics can be obtained. The ratio of polythiophene and polystyrene sulfonate [polythiophene: polystyrene sulfonate] in the polythiophene aqueous solution containing PSS is not particularly limited, but is preferably 1: 5 to 1:10. The total content (total content) of the polythiophene and polystyrene sulfonate in the polythiophene aqueous solution containing the PSS is not particularly limited, but is preferably 1 to 5% by weight. As the polythiophene aqueous solution containing the PSS, for example, a commercial product such as a trade name “Baytron” (manufactured by HC Stark) may be used. In addition, when using the polythiophene aqueous solution containing PSS, the total amount of polythiophene and polystyrene sulfonate is not particularly limited, but is 10 to 200 parts by weight with respect to 100 parts by weight of the acrylic polymer in the topcoat layer. The amount is preferably 25 to 150 parts by weight, more preferably 40 to 120 parts by weight.

  By using the acrylic resin as the base resin in combination with polythiophene as the antistatic component, the top coat layer can provide a transparent film substrate having a small surface resistivity even when the top coat layer is thin. . In particular, when an acrylic resin mainly composed of an acrylic polymer having a copolymer composition that does not substantially contain a monomer having an acidic functional group is used as the acrylic resin, a better result can be obtained.

  The melamine-based crosslinking agent in the topcoat layer has at least one effect (especially, among scratch resistance improvement, solvent resistance improvement, print adhesion improvement, and friction coefficient reduction) by crosslinking the acrylic polymer. , To improve the scratch resistance). The said melamine type crosslinking agent is a compound which has a melamine structure. Examples of the melamine-based crosslinking agent include, for example, monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine; methoxymethyl melamine, ethoxymethyl melamine, propoxymethyl melamine, Alkoxymethyl melamines such as butoxymethyl melamine, hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexabutoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyloxymethyl melamine, methoxybutyl melamine, ethoxybutyl melamine, Alkoxybutyl melamine such as propoxybutyl melamine and butoxybutyl melamine Such as alkoxyalkyl melamines and the like.

  Examples of the melamine-based crosslinking agent include trade names “Cymel 202”, “Cymel 212”, “Cymel 232”, “Cymel 235”, “Cymel 253”, “Cymel 266”, “Cymel 267”, “Cymel 270”. ”,“ Cymel 272 ”,“ Cymel 285 ”,“ Cymel 300 ”,“ Cymel 301 ”,“ Cymel 303 ”,“ Cymel 327 ”,“ Cymel 350 ”,“ Cymel 370 ”,“ Cymel 701 ”,“ Cymel 703 ” "Cymel 771" (manufactured by Cytec Industries, Inc.), trade names "Nikarak MW-30", "Nikarak MW-30M", "Nikarak MW-30HM", "Nikarak MW-45", "Nikarak MW-" 390 "," Nikarak MX-270 "," Nikarak MX- " 02 "," NIKALACK MX-706 "," NIKALACK MX-750 "(or more, (Ltd.) manufactured by Sanwa Chemical) can also be used commercially available products, such as.

  Although the usage-amount (content in the coating composition for the below-mentioned topcoat layer formation) of the said melamine type crosslinking agent is not specifically limited, 5-100 with respect to 100 weight part of acrylic polymers in a topcoat layer. Part by weight is preferable, more preferably 10 to 80 parts by weight, and still more preferably 20 to 50 parts by weight. If the amount used is less than 5 parts by weight, the scratch resistance may be inferior. On the other hand, if the amount used exceeds 100 parts by weight, the printability may be inferior. Moreover, depending on the combination with the other component which comprises a topcoat layer, the compatibility of a melamine type crosslinking agent may be insufficient, and an external appearance characteristic may fall, or solvent resistance may fall.

  As described above, as the main component of the acrylic resin, an acrylic polymer that does not substantially contain the monomer having the acidic functional group is used, and this is used in combination with a melamine-based cross-linking agent. The hardness tends to be higher and the adhesion of the topcoat layer to the base layer tends to be improved.

  The top coat layer preferably contains a lubricant in order to exhibit better scratch resistance with respect to the pressure-sensitive adhesive sheet of the present invention. As the lubricant, a known or commonly used lubricant can be used. For example, a fluorine-based or silicone-based lubricant can be preferably used. Of these, silicone-based lubricants (silicone-based lubricants) are preferable. Examples of the silicone-based lubricant include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. In addition, as the lubricant, a lubricant containing a fluorine compound or a silicone compound having an aryl group or an aralkyl group (sometimes referred to as “printable lubricant” in order to improve printability) may be used. Moreover, you may use the lubricant (reactive lubricant) containing the fluorine compound or silicone compound which has a crosslinkable reactive group.

  Although the usage-amount of the said lubricant is not specifically limited, 5-90 weight part is preferable with respect to 100 weight part of acrylic polymers in a topcoat layer, More preferably, it is 10-70 weight part, More preferably, it is 15 weight part Above (for example, 15 to 50 parts by weight), particularly preferably 20 parts by weight or more, and most preferably 25 parts by weight or more. If the amount of lubricant used is less than 5 parts by weight, scratch resistance may be reduced. On the other hand, if the amount of the lubricant used exceeds 90 parts by weight, the printability may be insufficient, or the appearance characteristics of the topcoat layer (and thus the transparent film substrate or pressure-sensitive adhesive sheet) may deteriorate.

  The lubricant is presumed to reduce the coefficient of friction by bleeding on the surface of the topcoat layer and imparting slipperiness to the surface. Therefore, by using the lubricant appropriately, the scratch resistance can be improved through the reduction of the friction coefficient. The lubricant can make the surface tension of the composition for forming a topcoat layer, which will be described later, uniform, and can contribute to reducing the thickness unevenness of the topcoat layer and reducing interference fringes (and thus improving the appearance characteristics). Such an improvement in appearance characteristics is particularly significant in the surface protective film for optical members. In addition, when the acrylic resin constituting the top coat layer is an ultraviolet curable acrylic resin, a fluorine-based or silicone-based lubricant is added thereto, and a composition for forming a top coat layer described later is applied to the base layer. When the coating is dried, the lubricant bleeds to the surface of the coating film (interface with the air), which suppresses the inhibition of curing by oxygen when irradiated with ultraviolet rays, and the UV curable acrylic resin is sufficient even on the outermost surface of the topcoat layer. Can be cured.

  The top coat layer may contain an antistatic component other than polythiophene, an antioxidant, a colorant (pigment, dye, etc.), a fluidity modifier (thixotropic agent, an increase agent) as necessary, as long as the effects of the present invention are not impaired. Additives such as a viscosity agent, a film-forming aid, and a catalyst (for example, an ultraviolet polymerization initiator in a composition containing an ultraviolet curable acrylic resin) may be included.

  As the antistatic component other than the polythiophene, a known or commonly used antistatic component can be used, and is not particularly limited. For example, an organic or inorganic conductive substance, various antistatic agents, and the like can be used. .

  Although it does not specifically limit as said organic electroconductive substance, For example, the conductive polymer except polythiophenes, such as a polyaniline, a polypyrrole, a polyethyleneimine, an allylamine type polymer, is mentioned. The said conductive polymer can be used individually or in combination of 2 or more types. Moreover, you may use in combination with another antistatic component (an inorganic electroconductive substance, an antistatic agent, etc.).

  As said polyaniline, commercial items, such as brand name "aqua-PASS" (Mitsubishi Rayon Co., Ltd. product, polyaniline sulfonic acid aqueous solution), can also be used, for example.

  The inorganic conductive material is not particularly limited. For example, tin oxide, antimony oxide, indium oxide, cadmium oxide, titanium oxide, zinc oxide, indium, tin, antimony, gold, silver, copper, aluminum, nickel, chromium , Titanium, iron, cobalt, copper iodide, ITO (indium oxide / tin oxide), ATO (antimony oxide / tin oxide), and the like.

  The method for forming the top coat layer of the transparent film substrate in the pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, the acrylic resin, polythiophene, melamine-based crosslinking agent, and additives used as necessary There is a technique including applying a liquid composition (topcoat layer forming composition) dispersed or dissolved in an appropriate solvent to the surface of the base layer. More specifically, for example, a method of forming the topcoat layer by applying the liquid composition to the surface of the base layer and drying, and performing a curing treatment (heat treatment, ultraviolet treatment, etc.) as necessary. Preferably it can be adopted.

  The solid content (NV) of the liquid composition (topcoat layer forming composition) is not particularly limited, but is preferably 5% by weight or less (for example, 0.05 to 5% by weight), more preferably 1% by weight. % Or less (for example, 0.1 to 1% by weight), more preferably 0.5% by weight or less, and particularly preferably 0.3% by weight or less. When the solid content exceeds 5% by weight, the viscosity of the liquid composition is increased, and the variation in drying time depending on the location is likely to occur. Thus, the top is thin and uniform (that is, the variation in thickness ΔD is small). It may be difficult to form a coat layer. The lower limit of the solid content of the liquid composition is not particularly limited, but is preferably 0.05% by weight, more preferably 0.1% by weight. If the solid content is less than 0.05% by weight, repellency is likely to occur in the coating film depending on the material of the base layer, the surface condition, and the like, which may increase ΔD.

  As the solvent constituting the liquid composition (topcoat layer forming composition), a solvent that can stably dissolve or disperse the components (acrylic resin, polythiophene, melamine-based crosslinking agent, etc.) of the topcoat layer is preferable. . As said solvent, an organic solvent, water, these mixed solvents etc. can be used, for example. Examples of the organic solvent include esters such as ethyl acetate; ketones such as methyl ethyl ketone, acetone and cyclohexanone; cyclic ethers such as tetrahydrofuran (THF) and dioxane; aromatic hydrocarbons such as toluene and xylene; methanol, One or more selected from aliphatic or alicyclic alcohols such as ethanol, n-propanol, isopropanol, and cyclohexanol; glycol ethers and the like can be used. Among these, from the viewpoint of forming a stable coating film, a solvent containing glycol ethers as a main component (for example, a solvent containing 50% by weight or more of glycol ethers) is preferable.

  As the glycol ethers, one or more selected from alkylene glycol monoalkyl ether and dialkylene glycol monoalkyl ether can be preferably used. Specifically, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Examples include monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-2-ethylhexyl ether, and the like.

The average thickness D _ave of the top coat layer is 2 to 50 nm, preferably 2 to 30 nm, more preferably 2 to 20 nm, and still more preferably 2 to 10 nm. When the average thickness D _ave of the top coat layer exceeds 50 nm, the appearance of the transparent film substrate looks whitish as a whole, and the appearance characteristics of the transparent film substrate (and thus the pressure-sensitive adhesive sheet having the transparent film substrate) are likely to deteriorate. Become. On the other hand, when the average thickness D _ave of the top coat layer is less than 2 nm, it is difficult to form the top coat layer uniformly.

The average thickness D _ave of the top coat layer is measured at five measurement points arranged at equal intervals along a straight line across the top coat layer (for example, a straight line across the top coat layer in the width direction). It can be obtained by measuring the thickness of the layer and calculating the arithmetic average value of the thickness at the five measurement points. In addition, it is preferable that the said measurement point is 2 cm or more (preferably 5 cm or more) apart from the adjacent measurement point.

The thickness of the topcoat layer (the thickness of the topcoat layer at each measurement point) is measured, for example, by observing the cross section of the transparent film substrate (or adhesive sheet) with a transmission electron microscope (TEM). be able to. Specifically, for example, a transparent film substrate (or adhesive sheet) is used as a sample, and after carrying out heavy metal dyeing treatment to clearly discriminate the topcoat layer, resin embedding is performed, and the above is performed by an ultrathin section method. The result obtained by TEM observation of the cross section of the sample can be adopted as the thickness of the top coat layer. As the TEM, for example, a transmission electron microscope (model “H-7650”) manufactured by Hitachi, Ltd. can be used.
In the examples described later, after performing binarization processing on a cross-sectional image obtained under the conditions of acceleration voltage: 100 kV and magnification: 60,000 times, the cross-sectional area of the topcoat layer is divided by the sample length in the field of view. Thus, the thickness of the top coat layer (average thickness in the field of view) was measured.
In addition, heavy metal dyeing | staining may be abbreviate | omitted when a topcoat layer can be observed clearly clearly, without performing heavy metal dyeing | staining.
Alternatively, a calibration curve for the correlation between the thickness grasped by the TEM and the detection results by various thickness detectors (for example, a surface roughness meter, an interference thickness meter, an infrared spectrometer, various X-ray diffractometers, etc.) The thickness of the top coat layer may be determined by creating and calculating

The thickness variation ΔD of the top coat layer is 40% or less (for example, 0 to 40%), preferably 30% or less, more preferably 25% or less, and still more preferably 20% or less.
The thickness variation ΔD of the top coat layer is measured at five measurement points arranged at equal intervals along a straight line across the top coat layer (for example, a straight line across the top coat layer in the width direction). The thickness of the layer was measured, and the difference between the maximum value D _max and the minimum value D _{min of} these measured values divided by the average thickness D _ave [ΔD (%) = (D _max −D _min ) / D _ave × 100 ] Is defined. In addition, it is preferable that the said measurement point is 2 cm or more (preferably 5 cm or more) apart from the adjacent measurement point. Moreover, the thickness at each measurement point of the topcoat layer may be directly measured by the above-described method (for example, by TEM observation, or the detection result obtained by an appropriate thickness detection device may be converted into the thickness by a calibration curve. ).
More specifically, the average thickness D _ave and the thickness variation ΔD of the topcoat layer can be measured according to the thickness measurement method described in Examples described later.
When the thickness variation ΔD of the top coat layer is 40% or less, streaks and unevenness due to partial whitening are difficult to be visually recognized, and good appearance characteristics are exhibited. That is, the smaller the ΔD, the better the appearance characteristics. Further, when the ΔD is small is advantageous in terms of D _ave is small and form a small transparent film substrate surface resistivity.

The X-ray intensity variation ΔI by fluorescent X-ray (XRF) analysis of the topcoat layer is not particularly limited, but is preferably 40% or less (for example, 0 to 40%), more preferably 30% or less, and still more preferably Is 25% or less, particularly preferably 20% or less. The X-ray intensity variation ΔI is obtained by performing XRF analysis on five measurement points arranged at equal intervals along a straight line across the topcoat layer (for example, a straight line across the topcoat layer in the width direction). The X-ray intensity I is measured, and the difference between the maximum value I _max and the minimum value I _{min of} these measured values divided by the average X-ray intensity I _ave [ΔI (%) = (I _max −I _min ) / I _ave × 100]. In addition, it is preferable that the said measurement point is 2 cm or more (preferably 5 cm or more) apart from the adjacent measurement point.
Here, the average X-ray intensity I _ave is an arithmetic average value of the X-ray intensity I at the five measurement points. As a unit of the X-ray intensity, kcps (number of X-ray photons incident through the counter tube window per second (count number)) is usually used. Specifically, for example, I _ave and ΔI can be measured according to the X-ray intensity variation measurement method described in the examples described later. When ΔI of the top coat layer is 40% or less, streaks and unevenness due to partial whitening are difficult to be visually recognized, and good appearance characteristics tend to be exhibited. In general, the smaller the above-described thickness variation ΔD, the smaller ΔI. Therefore, it ΔI is small, D _ave is small and the surface resistivity is also advantageous to form a small transparent film substrate.

  The element to be subjected to the XRF analysis is not particularly limited as long as it is an element capable of XRF analysis among the elements contained in the topcoat layer. For example, a sulfur atom (for example, a sulfur atom (S) derived from polythiophene contained in the topcoat layer), a silicon atom (for example, a silicon atom (Si) derived from a silicone-based lubricant contained in the topcoat layer), A tin atom (for example, a tin atom (Sn) derived from a tin oxide particle contained as a filler in the topcoat layer) or the like can be preferably employed as the target of the XRF analysis. Among them, it is preferable that the variation ΔI of the X-ray intensity based on the XRF analysis of the sulfur atom is 40% or less, or the variation ΔI of the X-ray intensity based on the XRF analysis of the silicon atom is 40% or less.

The XRF analysis can be performed as follows, for example. That is, as the XRF apparatus, a commercially available apparatus can be preferably used, and a spectral crystal can be appropriately selected and used, for example, a Ge crystal can be preferably used. The output setting and the like can be appropriately selected according to the apparatus to be used, and are not particularly limited. Usually, sufficient sensitivity can be obtained with an output of about 50 kV and 70 mA. More specifically, for example, the XRF analysis conditions described in Examples described later can be preferably employed.
From the viewpoint of improving measurement accuracy, the X-ray intensity per area corresponding to a circle having a diameter of 30 mm is approximately 0.01 kcps or more (more preferably 0.03 kcps or more, for example, 0. It is preferable that an element to be analyzed is 05 to 3.00 kcps).

  The transparent film substrate in the pressure-sensitive adhesive sheet of the present invention is a transparent substrate. Specifically, the total light transmittance in the visible light wavelength region of the transparent film substrate (according to JIS K7361-1) is not particularly limited, but is preferably 80 to 97%, more preferably 85 to 95%. is there. The haze of the transparent film substrate (according to JIS K7136) is not particularly limited, but is preferably 1.0 to 5.0%, more preferably 2.0 to 3.5%. When the total light transmittance and / or haze of the transparent film substrate is out of the above range, it tends to be difficult to accurately perform the appearance inspection of the adherend.

  Although the thickness of the said transparent film base material is not specifically limited, 10-150 micrometers is preferable, More preferably, it is 30-100 micrometers. If the thickness is less than 10 μm, the scratch preventing effect of the optical member may be impaired. On the other hand, if the thickness exceeds 150 μm, the cost may increase.

[Acrylic adhesive layer]
The acrylic pressure-sensitive adhesive layer (pressure-sensitive adhesive layer) in the pressure-sensitive adhesive sheet of the present invention is a water-dispersed acrylic pressure-sensitive adhesive composition (re-peeling) containing the acrylic emulsion polymer (A) and the compound (B) as essential components. Water-dispersed acrylic pressure-sensitive adhesive composition) (sometimes referred to as “pressure-sensitive adhesive composition of the present invention”). The pressure-sensitive adhesive composition of the present invention preferably further contains a water-insoluble crosslinking agent (C).

[Acrylic emulsion polymer (A)]
The acrylic emulsion polymer (A) in the pressure-sensitive adhesive composition of the present invention is a polymer comprising (meth) acrylic acid alkyl ester and a carboxyl group-containing unsaturated monomer as essential raw material monomers (raw material monomer components). (Acrylic polymer). That is, the acrylic emulsion polymer (A) is a polymer obtained from a monomer mixture containing (meth) acrylic acid alkyl ester and a carboxyl group-containing unsaturated monomer as essential components. The acrylic emulsion polymer (A) can be used alone or in combination of two or more. In the present specification, “(meth) acryl” means “acryl” and / or “methacryl” (one or both of “acryl” and “methacryl”).

  The (meth) acrylic acid alkyl ester is used as a main monomer component constituting the acrylic emulsion polymer (A), and has basic characteristics as a pressure-sensitive adhesive (or pressure-sensitive adhesive layer) such as adhesiveness and peelability. Play a role to express. Among them, alkyl acrylates tend to impart flexibility to the polymer forming the pressure-sensitive adhesive layer (acrylic pressure-sensitive adhesive layer) and exhibit the effect of exhibiting adhesiveness and adhesiveness in the pressure-sensitive adhesive layer. Alkyl esters tend to give the polymer forming the pressure-sensitive adhesive layer hardness and exert the effect of adjusting the removability of the pressure-sensitive adhesive layer. Although it does not specifically limit as said (meth) acrylic-acid alkylester, It is C1-C16 (more preferably 2-10, more preferably 4-8), linear, branched or cyclic alkyl. And (meth) acrylic acid alkyl ester having a group.

  Among them, as the alkyl acrylate ester, for example, an alkyl acrylate ester having an alkyl group having 2 to 14 carbon atoms (more preferably 4 to 8) is preferable, such as n-butyl acrylate, isobutyl acrylate, acrylic acid s. -It has a linear or branched alkyl group such as butyl, isoamyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, nonyl acrylate, or isononyl acrylate. And alicyclic alkyl acrylates such as alkyl acrylate and isobornyl acrylate. Of these, 2-ethylhexyl acrylate, n-butyl acrylate, and isobornyl acrylate are preferable.

  Further, as the alkyl methacrylate, for example, alkyl methacrylate having an alkyl group having 1 to 16 carbon atoms (more preferably 1 to 8) is preferable, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid. Methacrylic acid alkyl ester having a linear or branched alkyl group such as isopropyl acid, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, bornyl methacrylate And alicyclic methacrylic acid alkyl ester such as isobornyl methacrylate. Among these, methyl methacrylate and n-butyl methacrylate are preferable.

  The said (meth) acrylic-acid alkylester can be suitably selected according to the target adhesiveness etc., and can be used individually or in combination of 2 or more types.

  Content of the said (meth) acrylic-acid alkylester is 70-99.5 weight% in the total amount (total amount) (total raw material monomer) (100 weight%) of the raw material monomer which comprises an acrylic emulsion type polymer (A). More preferably, it is 85 to 99% by weight. When the content exceeds 99.5% by weight, the content of the carboxyl group-containing unsaturated monomer decreases, so that the anchoring property, low contamination and emulsion of the acrylic pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition In the case of less than 70% by weight, the adhesiveness and removability of the acrylic pressure-sensitive adhesive layer are lowered. When 2 or more types of (meth) acrylic-acid alkylesters are used, the total amount (total content) of all the (meth) acrylic-acid alkylesters should just satisfy the said range. The content ratio of the alkyl acrylate ester to the alkyl methacrylate ester in the (meth) acrylic acid alkyl ester (content of acrylic acid alkyl ester: content of alkyl methacrylate) is not particularly limited, but is 100: 0. About 30:70 (weight ratio) is preferable, More preferably, it is 100: 0-50: 50.

  The carboxyl group-containing unsaturated monomer can exhibit a function of forming a protective layer on the surface of the emulsion particles made of the acrylic emulsion polymer (A) and preventing shear breakage of the emulsion particles. This is further improved by neutralizing the carboxyl group with a base. The stability of emulsion particles against shear failure is more generally referred to as mechanical stability. In addition, by using a polyfunctional compound that reacts with a carboxyl group (for example, a polyfunctional epoxy compound) in combination of one or more, it can be used as a crosslinking point in the formation stage of the acrylic pressure-sensitive adhesive layer by removing water. Can act. Furthermore, the adhesion (anchoring property) between the acrylic pressure-sensitive adhesive layer and the substrate can be improved via the polyfunctional compound. Examples of such carboxyl group-containing unsaturated monomers include (meth) acrylic acid (acrylic acid, methacrylic acid), itaconic acid, maleic acid, fumaric acid, crotonic acid, carboxyethyl acrylate, carboxypentyl acrylate, and the like. Can be mentioned. The carboxyl group-containing unsaturated monomer includes acid anhydride group-containing unsaturated monomers such as maleic anhydride and itaconic anhydride. Among these, acrylic acid is preferable because it has a high relative concentration on the surface of the emulsion particles and can easily form a higher-density protective layer. In addition, the said carboxyl group-containing unsaturated monomer can be used individually or in combination of 2 or more types.

  Content of the said carboxyl group-containing unsaturated monomer is 0.5-10 weight% in the total amount (total raw material monomer) (100 weight%) of the raw material monomer which comprises an acrylic emulsion type polymer (A). , Preferably 1 to 5% by weight, more preferably 2 to 4% by weight. When the content exceeds 10% by weight, the carboxyl group-containing unsaturated monomer (for example, acrylic acid) is generally water-soluble, and thus polymerizes in water to cause thickening (increased viscosity). Furthermore, after the acrylic pressure-sensitive adhesive layer is formed, the interaction with the functional group on the surface of the polarizing plate, which is the adherend, increases, and the adhesive force increases with time, and peeling may become difficult. On the other hand, if it is less than 0.5% by weight, the mechanical stability of the emulsion particles decreases. Moreover, the adhesiveness (throwing property) of an acrylic adhesive layer and a transparent film base material falls, and it becomes a cause of adhesive residue.

  As a monomer component (raw material monomer) constituting the acrylic emulsion polymer (A), for the purpose of imparting a specific function, other than the above (meth) acrylic acid alkyl ester and carboxyl group-containing unsaturated monomer. A monomer component may be used in combination. Examples of such a monomer component include amide group-containing monomers such as (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N, N- for the purpose of improving cohesion. About 0.1 to 10% by weight of amino group-containing monomers such as dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate may be added (used). In addition, for purposes such as refractive index adjustment and reworkability, (meth) acrylic acid aryl esters such as phenyl (meth) acrylate; vinyl esters such as vinyl acetate and vinyl propionate; styrene monomers such as styrene, You may add (use) in the ratio of 15 weight% or less. Furthermore, for the purpose of improving emulsion particle cross-linking and cohesive strength, epoxy group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether, and polyfunctional monomers such as trimethylolpropane tri (meth) acrylate and divinylbenzene, You may add (use) in the ratio of less than weight%. Furthermore, in order to form hydrazide bridge | crosslinking in combination with a hydrazide type | system | group crosslinking agent and to improve especially low pollution property, diacetone acrylamide (DAAM), allyl acetoacetate, 2- (acetoacetoxy) ethyl (meth) acrylate, etc. A keto group-containing unsaturated monomer may be added (used) in a proportion of less than 10% by weight (preferably 0.5 to 5% by weight).

  Moreover, as said other monomer component, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( (Meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl Hydroxyl group-containing unsaturated monomers such as vinyl ether, 4-hydroxybutyl vinyl ether and diethylene glycol monovinyl ether may be used. The hydroxyl group-containing unsaturated monomer preferably has a smaller addition amount (use amount) from the viewpoint of further reducing whitening contamination. Specifically, the addition amount of the hydroxyl group-containing unsaturated monomer is preferably less than 1% by weight, more preferably less than 0.1% by weight, and still more preferably substantially free (for example, 0.05% by weight). Less than%). However, when the purpose is to introduce cross-linking points such as cross-linking of hydroxyl groups and isocyanate groups or cross-linking of metal cross-links, about 0.01 to 10% by weight may be added (used).

  In addition, the addition amount (usage amount) of said other monomer component is content in the total amount (total raw material monomer) (100 weight%) of the raw material monomer which comprises an acrylic emulsion polymer (A).

  In particular, from the viewpoint of improving the appearance of the pressure-sensitive adhesive sheet of the present invention, the monomer component (raw material monomer) constituting the acrylic emulsion polymer (A) is selected from the group consisting of methyl methacrylate, isobornyl acrylate and vinyl acetate. It is preferred to use at least one selected monomer. Particularly preferred is methyl methacrylate. Monomer selected from the group consisting of the above monomers (methyl methacrylate, isobornyl acrylate and vinyl acetate) in the total amount (total raw material monomers) (100 wt%) of the raw material monomers constituting the acrylic emulsion polymer (A) ) Is preferably 1 to 15% by weight, more preferably 2 to 10% by weight, and still more preferably 2 to 5% by weight. When the content is less than 1% by weight, the effect of improving the appearance may not be obtained, and when it exceeds 15% by weight, the acrylic pressure-sensitive adhesive layer may become too hard and adhesion may be lowered. In addition, when two or more monomers chosen from the group which consists of methyl methacrylate, isobornyl acrylate, and vinyl acetate are contained in the raw material monomer which comprises an acrylic emulsion type polymer (A), methyl methacrylate The total content (total content) of isobornyl acrylate and vinyl acetate should satisfy the above range.

  The acrylic emulsion polymer (A) in the present invention is obtained by emulsion polymerization of the above raw material monomer (monomer mixture) with an emulsifier and a polymerization initiator.

  The emulsifier used for emulsion polymerization of the acrylic emulsion polymer (A) is a reactive emulsifier (reactive emulsifier containing a radical polymerizable functional group) in which a radical polymerizable functional group is introduced into the molecule. That is, the acrylic emulsion polymer (A) is an acrylic emulsion polymer polymerized using a reactive emulsifier containing a radical polymerizable functional group in the molecule. The reactive emulsifier containing the radical polymerizable reactive group may be used alone or in combination of two or more.

  The reactive emulsifier containing a radical polymerizable functional group (hereinafter referred to as “reactive emulsifier”) is an emulsifier containing at least one radical polymerizable functional group in a molecule (in one molecule). The reactive emulsifier is not particularly limited, and various reactive emulsifiers having a radical polymerizable functional group such as vinyl group, propenyl group, isopropenyl group, vinyl ether group (vinyloxy group), and allyl ether group (allyloxy group). 1 type or 2 or more types can be selected and used. Use of the reactive emulsifier is preferable because the emulsifier is incorporated into the polymer and contamination from the emulsifier is reduced.

  Examples of the reactive emulsifier include nonionic anionic emulsifiers such as sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl sulfosuccinate (nonionic). A reactive emulsifier having a form in which a radical polymerizable functional group (radical reactive group) such as a propenyl group or an allyl ether group is introduced into an anionic emulsifier having a hydrophilic hydrophilic group) (or corresponding to the form) Can be mentioned. Hereinafter, a reactive emulsifier having a form in which a radical polymerizable functional group is introduced into an anionic emulsifier is referred to as an “anionic reactive emulsifier”. A reactive emulsifier having a form in which a radical polymerizable functional group is introduced into a nonionic anionic emulsifier is referred to as a “nonionic anionic reactive emulsifier”.

  In particular, when an anionic reactive emulsifier (particularly, a nonionic anionic reactive emulsifier) is used, the emulsifier is incorporated into the polymer, so that the low contamination property can be improved. Furthermore, when the water-insoluble crosslinking agent (C) is a polyfunctional epoxy-based crosslinking agent having an epoxy group, the reactivity of the crosslinking agent can be improved by its catalytic action. When an anionic reactive emulsifier is not used, the crosslinking reaction is not completed by aging, and the adhesive force of the pressure-sensitive adhesive layer may change over time. Furthermore, there may be a problem that the adhesive force with the adherend increases with time due to unreacted carboxyl groups. In addition, since the anionic reactive emulsifier is incorporated in the polymer, it is generally used as a catalyst for an epoxy crosslinking agent, such as a quaternary ammonium compound (for example, see JP-A-2007-31585). In addition, since it does not precipitate on the surface of the adherend, it cannot cause whitening contamination, which is preferable.

  Examples of such reactive emulsifiers include the trade name “ADEKA rear soap SE-10N” (manufactured by ADEKA), the trade name “AQUALON HS-10” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the trade name “AQUALON”. Commercial products such as “HS-05” (Daiichi Kogyo Seiyaku Co., Ltd.) can also be used.

In particular, since impurity ions may be a problem, it is desirable to remove the impurity ions and use a reactive emulsifier having an SO ₄ ^2- ion concentration of 100 μg / g or less. In the case of an anionic emulsifier, it is desirable to use an ammonium salt reactive emulsifier. As a method for removing impurities from the reactive emulsifier, an appropriate method such as an ion exchange resin method, a membrane separation method, or a precipitation filtration method for impurities using alcohol can be used.

  The amount (use amount) of the reactive emulsifier is not particularly limited, but is 0.1 to 5 with respect to 100 parts by weight of the total amount of raw material monomers (total raw material monomers) constituting the acrylic emulsion polymer (A). Part by weight is preferred, more preferably 0.5 to 3 parts by weight. If the blending amount exceeds 5 parts by weight, the cohesive force of the pressure-sensitive adhesive (pressure-sensitive adhesive layer) may be reduced to increase the amount of contamination on the adherend, and contamination with an emulsifier may occur. On the other hand, if the blending amount is less than 0.1 parts by weight, stable emulsification may not be maintained.

  The polymerization initiator used for emulsion polymerization of the acrylic emulsion polymer (A) is not particularly limited, and examples thereof include 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-amidinopropane). ) Dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2, Azo polymerization initiators such as 2'-azobis (N, N'-dimethyleneisobutylamidine); persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide, hydrogen peroxide, etc. Peroxide-based polymerization initiators; redox initiators in combination with peroxides and reducing agents, such as peroxides Combination with scorbic acid (combination of hydrogen peroxide and ascorbic acid), combination of peroxide and iron (II) salt (combination of hydrogen peroxide and iron (II) salt), persulfate A redox polymerization initiator based on a combination of a salt and sodium hydrogen sulfite can be used. In addition, the said polymerization initiator can be used individually or in combination of 2 or more types.

  The blending amount (use amount) of the polymerization initiator can be appropriately determined according to the type of the initiator and the raw material monomer, and is not particularly limited. However, the amount of the raw material monomer constituting the acrylic emulsion polymer (A) is not particularly limited. The amount is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.5 part by weight, based on 100 parts by weight of the total amount (total raw material monomers).

  For the emulsion polymerization of the acrylic emulsion polymer (A), any method such as general batch polymerization, continuous dropping polymerization, and divided dropping polymerization can be used, and the method is not particularly limited. From the viewpoint of reducing contamination, it is desirable to perform polymerization at the same time and at a low temperature (for example, 55 ° C. or less, preferably 30 ° C. or less). When polymerization is performed under such conditions, it is presumed that contamination is reduced because high molecular weight products are easily obtained and low molecular weight products are reduced.

  The acrylic emulsion polymer (A) is a polymer having a structural unit derived from a (meth) acrylic acid alkyl ester and a structural unit derived from a carboxyl group-containing unsaturated monomer as essential structural units. The content of the structural unit derived from the (meth) acrylic acid alkyl ester in the acrylic emulsion polymer (A) is preferably 70 to 99.5% by weight, more preferably 85 to 99% by weight. The content of the structural unit derived from the carboxyl group-containing unsaturated monomer in the acrylic emulsion polymer (A) is preferably 0.5 to 10% by weight, more preferably 1 to 5% by weight, even more preferably. Is 2 to 4% by weight.

  The solvent-insoluble content of the acrylic emulsion polymer (A) (ratio of solvent-insoluble components, sometimes referred to as “gel fraction”) is preferably 70% (% by weight) or more, more preferably 75% by weight or more. More preferably, it is 80 weight% or more. If the solvent-insoluble content is less than 70% by weight, the acrylic emulsion polymer (A) contains a large amount of low molecular weight substances, so that the low molecular weight component in the pressure-sensitive adhesive layer cannot be sufficiently reduced only by the effect of crosslinking. There are cases where adherend contamination resulting from molecular weight components or the like occurs or the adhesive strength is too high. The solvent-insoluble content can be controlled by the polymerization initiator, reaction temperature, type of emulsifier and raw material monomer, and the like. Although the upper limit of the said solvent insoluble part is not specifically limited, For example, 99 weight% is preferable.

In the present invention, the solvent insoluble content of the acrylic emulsion polymer (A) is a value calculated by the following “method for measuring the solvent insoluble content”.
(Measurement method of solvent insoluble matter)
Acrylic emulsion polymer (A): About 0.1 g was collected and wrapped in a porous tetrafluoroethylene sheet (trade name “NTF1122”, manufactured by Nitto Denko Corporation) having an average pore diameter of 0.2 μm, and then threaded The weight at that time is measured, and this weight is defined as the weight before immersion. The weight before immersion is the total weight of the acrylic emulsion polymer (A) (collected above), the tetrafluoroethylene sheet, and the kite string. Further, the total weight of the tetrafluoroethylene sheet and the kite string is also measured, and this weight is defined as the wrapping weight.
Next, the acrylic emulsion polymer (A) wrapped with a tetrafluoroethylene sheet and bound with a kite string (referred to as “sample”) is placed in a 50 ml container filled with ethyl acetate at 23 ° C. Let stand for 7 days. Then, the sample (after ethyl acetate treatment) is taken out from the container, transferred to an aluminum cup, dried in a dryer at 130 ° C. for 2 hours to remove ethyl acetate, the weight is measured, and the weight is immersed. After weight.
And a solvent insoluble content is computed from a following formula.
Solvent insoluble matter (% by weight) = (XY) / (ZY) × 100 (1)
(In Formula (1), X is the weight after immersion, Y is the weight of the bag, and Z is the weight before immersion.)

  The weight average molecular weight (Mw) of the solvent-soluble component (sometimes referred to as “sol component”) of the acrylic emulsion polymer is not particularly limited, but is preferably 40,000 to 200,000, more preferably 50,000 to 150,000, more preferably 60,000 to 100,000. When the weight average molecular weight of the solvent-soluble component of the acrylic emulsion polymer is 40,000 or more, the wettability of the pressure-sensitive adhesive composition to the adherend is improved, and the adhesion to the adherend is improved. Moreover, when the weight average molecular weight of the solvent-soluble component of the acrylic emulsion polymer is 200,000 or less, the residual amount of the pressure-sensitive adhesive composition on the adherend is reduced, and the low contamination property is improved.

The weight average molecular weight of the solvent-soluble component of the acrylic emulsion polymer is determined by air-drying the treated solution (ethyl acetate solution) after the ethyl acetate treatment obtained in the measurement of the solvent-insoluble component of the acrylic emulsion polymer at room temperature. The sample (solvent-soluble content of the acrylic emulsion polymer) obtained by the measurement can be obtained by measurement by GPC (gel permeation chromatography). Specific methods for measuring include the following methods.
[Measuring method]
GPC measurement is carried out using a GPC device “HLC-8220GPC” manufactured by Tosoh Corporation, and the molecular weight is determined in terms of polystyrene. The measurement conditions are as follows.
Sample concentration: 0.2 wt% (THF solution)
Sample injection volume: 10 μl
Eluent: THF
Flow rate: 0.6 ml / min
Measurement temperature: 40 ° C
Column: Sample column; 1 TSKguardcolumn SuperHZ-H + 2 TSKgel SuperHZM-H Reference column; 1 TSKgel SuperH-RC Detector: Differential refractometer

  The content of the acrylic emulsion polymer (A) in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably 80% by weight or more, more preferably 100% by weight of the nonvolatile content of the pressure-sensitive adhesive composition. Is 90 to 99% by weight.

[Compound (B)]
The compound (B) in the pressure-sensitive adhesive composition (water-dispersed acrylic pressure-sensitive adhesive composition) of the present invention is a compound represented by the following formula (I).
_{^{R 1 O- (PO) a -}} (EO) b - (PO) c -R 2 (I)

In the above formula (I), R ¹ and R ² represent a linear or branched alkyl group or a hydrogen atom. R ¹ and R ² may be the same or different from each other. Although it does not specifically limit as said linear or branched alkyl group, For example, C1-C4 alkyl groups, such as a methyl group, an ethyl group, a propyl group, a butyl group, are illustrated preferably. R ¹ and R ² are particularly preferably both hydrogen atoms.

In the above formula (I), PO represents an oxypropylene group [—CH ₂ CH (CH ₃ ) O—]. A and c are each a positive integer (an integer of 1 or more), preferably 1 to 100, more preferably 10 to 50, and still more preferably 10 to 30. a and c may be the same as or different from each other.

In the above formula (I), EO represents an oxyethylene group [—CH ₂ CH ₂ O—]. B is a positive integer (an integer of 1 or more), preferably 1 to 50, more preferably 1 to 30, and still more preferably 1 to 15.

  In the above formula (I), the addition form (copolymerization form) of EO and PO is a block type. That is, the compound (B) is a triblock having a block [polyoxypropylene block, polypropylene glycol (PPG) block] composed of PO on both sides of a block composed of EO [polyoxyethylene block, polyethylene glycol (PEG) block]. It is a copolymer or a derivative thereof.

  By blending the compound (B) in the pressure-sensitive adhesive composition, it is possible to eliminate defects due to bubbles due to the defoaming property.

  The compound (B) has a block-type structure in which the polyoxyethylene block is located at the center of the molecule, and has a structure in which a block composed of a hydrophobic group PO exists at both ends of the molecule. It is difficult to line up evenly at the interface and can exhibit defoaming properties. Compared with PPG-PEG-PPG triblock copolymer, PEG-PPG-PEG triblock copolymer and polyoxyethylene and polyoxypropylene diblock copolymer having polyoxyethylene block at both ends of the molecule Since it is easy to arrange uniformly at the gas-liquid interface, it has the effect of stabilizing the foam.

Furthermore, since the compound (B) has high hydrophobicity, it is unlikely to cause whitening contamination that occurs on the adherend in a high humidity environment, and the low contamination property is improved. In the case of a highly hydrophilic compound (especially a water-soluble compound), in a high humidity environment, the compound dissolves in water and is easily transferred to the adherend, or the bleed compound swells on the adherend. Since it becomes easy to whiten, it is easy to cause whitening contamination.
In addition, by using the compound (B), the pressure-sensitive adhesive layer (acrylic pressure-sensitive adhesive layer) formed from the pressure-sensitive adhesive composition of the present invention is hardly whitened (humidified whitening) even under humidified storage. When the pressure-sensitive adhesive sheet is used for a surface protective film for an optical member, if the pressure-sensitive adhesive layer is whitened (that is, the pressure-sensitive adhesive sheet is whitened), the optical member inspection process may be hindered.

  Ratio of “total weight of EO” to “total weight of compound (B)” of the above compound (B) [(total weight of EO) / (total weight of compound (B)) × 100] (unit:% by weight) (%)) Is not particularly limited, but is preferably 50% by weight or less, more preferably 5 to 50% by weight, and still more preferably 10 to 30% by weight. When the said ratio (EO content rate) exceeds 50 weight%, the hydrophilic property of a compound (B) will become high and defoaming property may be lost. Moreover, if the said ratio is less than 5 weight%, the hydrophobicity of a compound (B) will become high too much, and it may cause a repellency. The above-mentioned “total weight of compound (B)” means “the total amount of all compounds (B) in the pressure-sensitive adhesive composition of the present invention”, and “total weight of EO” means “this It is "the total amount of the weight of EO contained in all the compounds (B) in the pressure-sensitive adhesive composition of the invention". The ratio of the “total weight of EO” to the “total weight of compound (B)” may be referred to as “EO content”. Examples of the method for measuring the EO content include NMR, chromatography (chromatography), and TOF-SIMS (time-of-flight secondary ion mass spectrometry).

  As for the number average molecular weight of the said compound (B) in the adhesive composition of this invention, 1500-4000 are preferable. When the number average molecular weight is less than 1500, the compatibility of the compound (B) with the system (the system of the pressure-sensitive adhesive composition) becomes too high, and the defoaming effect may not be obtained. On the other hand, if the number average molecular weight exceeds 4000, the incompatibility with the system becomes too high, so that the defoaming property becomes high, but it causes repelling when the pressure-sensitive adhesive composition is applied to a substrate or the like. There is.

  The compound (B) may be a commercially available product. Specifically, for example, trade names “Adeka Pluronic 25R-1”, “Adeka Pluronic 25R-2”, “Adeka Pluronic” manufactured by ADEKA Corporation. 17R-2 ”,“ Adeka Pluronic 17R-3 ”; manufactured by BASF Japan Ltd.,“ Pluronic RPE series ”, and the like.

  The said compound (B) can be used individually or in mixture of 2 or more types.

  When blending the above compound (B) during the production of the pressure-sensitive adhesive composition of the present invention, it is preferable to blend only the compound (B) without using a solvent, from the viewpoint of improving blending workability, etc. Those obtained by dispersing or dissolving the compound (B) in various solvents may be used. Examples of the solvent include 2-ethylhexanol, butyl cellosolve, dipropylene glycol, ethylene glycol, propylene glycol, normal propyl alcohol, and isopropanol.

  Although the compounding quantity (content in the adhesive composition of this invention) of the said compound (B) is not specifically limited, 0.01-1 weight part with respect to 100 weight part of acrylic emulsion type polymers (A). More preferably, it is 0.02-0.8 weight part, More preferably, it is 0.02-0.5 weight part, Most preferably, it is 0.02-0.3 weight part. When the blending amount is less than 0.01 parts by weight, defoaming properties may not be imparted, and when it exceeds 1 part by weight, contamination may easily occur.

[Water-insoluble crosslinking agent (C)]
The cross-linking agent used in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but a water-insoluble cross-linking agent is preferable from the viewpoint of being able to prevent an increase in adhesive force due to low contamination. Furthermore, a water-insoluble crosslinking agent (C) having two or more functional groups capable of reacting with a carboxyl group in the molecule (in one molecule) is preferable. In the present specification, the “water-insoluble crosslinking agent (C) having two or more functional groups capable of reacting with a carboxyl group in the molecule” may be simply referred to as “water-insoluble crosslinking agent (C)”. is there. That is, the pressure-sensitive adhesive composition of the present invention preferably further contains a water-insoluble crosslinking agent (C).

  The water-insoluble crosslinking agent (C) is a water-insoluble compound and has two or more (for example, 2 to 6) functional groups capable of reacting with a carboxyl group in the molecule (in one molecule). It is. The number of functional groups that can react with a carboxyl group in one molecule is not particularly limited, but 3 to 5 is preferable. As the number of functional groups capable of reacting with a carboxyl group in one molecule increases, the pressure-sensitive adhesive composition crosslinks more closely (that is, the cross-linked structure of the polymer forming the acrylic pressure-sensitive adhesive layer becomes dense). For this reason, it becomes possible to prevent the wetting and spreading of the pressure-sensitive adhesive layer after forming the acrylic pressure-sensitive adhesive layer. Further, since the polymer forming the acrylic pressure-sensitive adhesive layer is constrained, the functional group (carboxyl group) in the acrylic pressure-sensitive adhesive layer segregates on the adherend surface, and the acrylic pressure-sensitive adhesive layer and the adherend are separated. It becomes possible to prevent the adhesive force from increasing with time. On the other hand, if the number of functional groups capable of reacting with a carboxyl group in one molecule exceeds 6 and is too large, a gelled product may be formed.

  Although it does not specifically limit as a functional group which can react with the carboxyl group in the said water-insoluble crosslinking agent (C), For example, an epoxy group, an isocyanate group, a carbodiimide group etc. are mentioned. Among these, an epoxy group is preferable from the viewpoint of reactivity. Furthermore, since the reactivity is high, unreacted substances in the cross-linking reaction hardly remain, which is advantageous for low contamination, and the adhesive force with the adherend increases with time due to unreacted carboxyl groups in the acrylic pressure-sensitive adhesive layer. From the viewpoint of preventing this, a glycidylamino group is preferable. That is, as the water-insoluble crosslinking agent (C), an epoxy-based crosslinking agent having an epoxy group is preferable, and among them, a crosslinking agent having a glycidylamino group (glycidylamino-based crosslinking agent) is preferable. When the water-insoluble crosslinking agent (C) is an epoxy crosslinking agent (particularly glycidylamino crosslinking agent), the number of epoxy groups (particularly glycidylamino group) in one molecule is 2 or more (for example, 2 to 6) is preferable, and 3 to 5 is more preferable.

  The water-insoluble crosslinking agent (C) is a water-insoluble compound. The term “water-insoluble” means that the solubility in 100 parts by weight of water at 25 ° C. (the weight of the compound (crosslinking agent) that can be dissolved in 100 parts by weight of water) is 5 parts by weight or less, preferably 3 It is 2 parts by weight or less, more preferably 2 parts by weight or less. By using a water-insoluble cross-linking agent, the cross-linking agent remaining without cross-linking is less likely to cause whitening contamination on the adherend in a high-humidity environment (under humidification), and the low-contamination property is improved. . In the case of a water-soluble crosslinking agent, in a high-humidity environment (humidified), the remaining crosslinking agent dissolves in moisture and is easily transferred to the adherend, and thus easily causes whitening contamination. In addition, the water-insoluble cross-linking agent has a higher contribution to the cross-linking reaction (reaction with a carboxyl group) than the water-soluble cross-linking agent, and has a high effect of preventing the adhesive force from increasing with time. Furthermore, since the water-insoluble crosslinking agent has a high crosslinking reaction reactivity, the crosslinking reaction proceeds promptly by aging, and the adhesive force with the adherend increases with time due to unreacted carboxyl groups in the adhesive layer. Can be prevented.

In addition, the solubility with respect to water of said crosslinking agent can be measured as follows, for example.
(Measurement method of water solubility)
The same weight of water (25 ° C.) and the crosslinking agent are mixed using a stirrer at a rotation speed of 300 rpm for 10 minutes, and separated into an aqueous phase and an oil phase by centrifugation. Next, the aqueous phase is collected and dried at 120 ° C. for 1 hour, and the nonvolatile content in the aqueous phase (parts by weight of nonvolatile components relative to 100 parts by weight of water) is determined from the loss on drying.

  Specifically, as the water-insoluble crosslinking agent (C), 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (for example, trade name “TETRAD-C” manufactured by Mitsubishi Gas Chemical Co., Ltd.) Etc.] [Solubility of 2 parts by weight or less with respect to 100 parts by weight of water at 25 ° C.] 1,3-bis (N, N-diglycidylaminomethyl) benzene (for example, trade name “TETRAD-” manufactured by Mitsubishi Gas Chemical Co., Ltd.) X ”etc.) [glycidylamino-based cross-linking agent such as solubility in 100 parts by weight of water at 25 ° C. of 2 parts by weight or less]; Tris (2,3-epoxypropyl) isocyclicate (for example, product name“ Nissan Chemical Co., Ltd. Other epoxy-based cross-linking agents such as “TEPIC-G” and the like] [solubility of 2 parts by weight or less with respect to 100 parts by weight of water at 25 ° C.] are exemplified. In addition, the said water-insoluble crosslinking agent (C) may be used independently and may use 2 or more types together.

  When the water-insoluble cross-linking agent (C) is added at the time of preparing the pressure-sensitive adhesive composition of the present invention, the water-insoluble cross-linking agent (C) is added to the liquid water-insoluble cross-linking agent (C) as it is ( May be added after being dissolved and / or diluted with an organic solvent (however, the amount of the organic solvent used is preferably as small as possible). The method of emulsifying the water-insoluble crosslinking agent (C) with an emulsifier is not preferable because the emulsifier bleeds and easily causes contamination (particularly whitening contamination).

  The blending amount of the water-insoluble crosslinking agent (C) (content in the pressure-sensitive adhesive composition of the present invention) is that of the carboxyl group-containing unsaturated monomer used as the raw material monomer of the acrylic emulsion polymer (A). It is preferable that the amount of the functional group capable of reacting with the carboxyl group of the water-insoluble crosslinking agent (C) is 0.3 to 1.3 mol with respect to 1 mol of the carboxyl group. That is, the “carboxyl of all water-insoluble crosslinking agents (C)” with respect to “the total number of moles of carboxyl groups of all carboxyl group-containing unsaturated monomers used as raw material monomers of the acrylic emulsion polymer (A)” The ratio of “the total number of moles of functional groups capable of reacting with groups” [functional group capable of reacting with carboxyl groups / carboxyl groups] (molar ratio) is preferably 0.3 to 1.3, more preferably 0.8. It is 4-1.1, More preferably, it is 0.5-1.0. When [functional group / carboxyl group capable of reacting with carboxyl group] is less than 0.3, there are many unreacted carboxyl groups in the acrylic pressure-sensitive adhesive layer, and due to the interaction between the carboxyl group and the adherend, There may be an increase in adhesive strength over time. Moreover, when it exceeds 1.3, many unreacted non-water-soluble crosslinking agents (C) exist in an acrylic adhesive layer, and an external appearance defect may arise.

  In particular, when the water-insoluble crosslinking agent (C) is an epoxy-based crosslinking agent, the [epoxy group / carboxyl group] (molar ratio) is preferably 0.3 to 1.3, more preferably 0.8. It is 4-1.1, More preferably, it is 0.5-1.0. Furthermore, when the water-insoluble crosslinking agent (C) is a glycidylamino crosslinking agent, it is preferable that [glycidylamino group / carboxyl group] (molar ratio) satisfy the above range.

For example, when 4 g of water-insoluble crosslinking agent (C) having a functional group equivalent of 110 (g / eq) that can react with a carboxyl group is added (blended) to the pressure-sensitive adhesive composition, water-insoluble The number of moles of the functional group capable of reacting with the carboxyl group of the functional crosslinking agent (C) can be calculated as follows, for example.
Number of moles of functional group capable of reacting with carboxyl group of water-insoluble crosslinking agent (C) = [blending amount (addition amount) of water-insoluble crosslinking agent (C)] / [functional group equivalent] = 4/110
For example, when 4 g of an epoxy-based crosslinking agent having an epoxy equivalent of 110 (g / eq) is added (blended) as the water-insoluble crosslinking agent (C), the number of moles of epoxy groups possessed by the epoxy-based crosslinking agent is, for example, It can be calculated as follows.
Number of moles of epoxy group possessed by epoxy-based crosslinking agent = [blending amount (addition amount) of epoxy-based crosslinking agent] / [epoxy equivalent] = 4/110

  The pressure-sensitive adhesive composition of the present invention is a water-dispersed pressure-sensitive adhesive composition. The “water-dispersed type” means that it can be dispersed in an aqueous medium, that is, the pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition that can be dispersed in an aqueous medium. The aqueous medium is a medium (dispersion medium) containing water as an essential component, and may be a mixture of water and a water-soluble organic solvent in addition to water alone. The pressure-sensitive adhesive composition of the present invention may be a dispersion using the above aqueous medium or the like.

  The pressure-sensitive adhesive composition of the present invention may contain a polyfunctional hydrazide-based crosslinking agent as another crosslinking agent other than the water-insoluble crosslinking agent (C). By using a polyfunctional hydrazide-based crosslinking agent, the removability of the acrylic pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, the adhesiveness, and the anchoring property with the substrate can be improved. A polyfunctional hydrazide-based crosslinking agent (sometimes simply referred to as “hydrazide-based crosslinking agent”) is a compound having at least two hydrazide groups in a molecule (in one molecule). The number of hydrazide groups in one molecule is preferably 2 or 3, more preferably 2. The compound used as such a hydrazide-based cross-linking agent is not particularly limited. Acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, naphthalic acid dihydrazide, acetone dicarboxylic acid dihydrazide, fumaric acid dihydrazide, maleic acid Itaconic acid dihydrazide, trimellitic acid dihydrazide, 1,3,5-benzenetricarboxylic acid dihydrazide, pyromellitic acid dihydr Hydrazide, dihydrazide compounds such as aconitic acid dihydrazide are preferred. Among these, particularly preferred are adipic acid dihydrazide and sebacic acid dihydrazide. These hydrazide crosslinking agents may be used alone or in combination of two or more.

  Commercially available products may be used as the hydrazide-based crosslinking agent, for example, “Adipic acid dihydrazide (reagent)” manufactured by Tokyo Chemical Industry Co., Ltd., “Adipoil dihydrazide (reagent)” manufactured by Wako Pure Chemical Industries, Ltd. Etc. can be used.

  The blending amount of the hydrazide crosslinking agent (content in the pressure-sensitive adhesive composition of the present invention) is not particularly limited, but is a keto group-containing unsaturated monomer used as a raw material monomer for the acrylic emulsion polymer (A). The amount is preferably 0.025 to 2.5 mol, more preferably 0.1 to 2 mol, and still more preferably 0.2 to 1.5 mol, per 1 mol of the keto group. If the blending amount is less than 0.025 mol, the effect of adding a crosslinking agent is small, the acrylic pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet is delaminated, and a low molecular weight component remains in the polymer forming the acrylic pressure-sensitive adhesive layer. In some cases, whitening contamination of the adherend tends to occur. Moreover, when it exceeds 2.5 mol, an unreacted crosslinking agent component may cause a contamination.

  From the viewpoint of low contamination, it is preferable not to add a quaternary ammonium salt to the pressure-sensitive adhesive composition of the present invention, and it is preferable not to add a quaternary ammonium compound. Therefore, the pressure-sensitive adhesive composition of the present invention preferably does not substantially contain a quaternary ammonium salt, and preferably does not substantially contain a quaternary ammonium compound. These compounds are generally used as a catalyst for improving the reactivity of the epoxy crosslinking agent. However, these compounds are not incorporated into the polymer forming the pressure-sensitive adhesive layer, and can move freely in the pressure-sensitive adhesive layer, so that they easily deposit on the surface of the adherend, and these compounds are contained in the pressure-sensitive adhesive composition. In some cases, whitening contamination is likely to occur, and low contamination may not be achieved. Specifically, the content of the quaternary ammonium salt in the pressure-sensitive adhesive composition of the present invention is preferably less than 0.1% by weight, more preferably based on 100% by weight of the pressure-sensitive adhesive composition (nonvolatile content). Is less than 0.01% by weight, more preferably less than 0.005% by weight. Furthermore, it is preferable that the content of the quaternary ammonium compound satisfies the above range.

  In addition, although a quaternary ammonium salt is not specifically limited, Specifically, it is a compound represented, for example by a following formula.

In the above formula, R ³ , R ⁴ , R ⁵ , and R ⁶ represent an alkyl group, an aryl group, or a group derived therefrom (excluding a hydrogen atom, such as an alkyl group or an aryl group having a substituent). . X ⁻ represents a counter ion.

  The quaternary ammonium salt and the quaternary ammonium compound are not particularly limited, but for example, water such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. Alkylammonium oxide and its salts, arylammonium hydroxide such as tetraphenylammonium hydroxide and its salts, trilaurylmethylammonium ion, didecyldimethylammonium ion, dicocoyldimethylammonium ion, distearyldimethylammonium ion, dioleyldimethylammonium ion Ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, behenyltrimethylammonium ion, cocoylbis (2-hydride) Xylethyl) methylammonium ion, polyoxyethylene (15) cocostearylmethylammonium ion, oleylbis (2-hydroxyethyl) methylammonium ion, cocobenzyldimethylammonium ion, laurylbis (2-hydroxyethyl) methylammonium ion, decylbis (2- And a base having hydroxyethyl) methylammonium ion as a cation and salts thereof.

  Furthermore, the pressure-sensitive adhesive composition of the present invention is for improving the reactivity of the epoxy-based crosslinking agent in the same manner as the quaternary ammonium salt (or quaternary ammonium compound) from the viewpoint of low contamination. It is preferable not to add a tertiary amine and an imidazole compound which are generally used as a catalyst or the like. Therefore, it is preferable that the pressure-sensitive adhesive composition of the present invention does not substantially contain a tertiary amine and an imidazole compound. Specifically, the content of the tertiary amine and the imidazole compound (the total content of the tertiary amine and the imidazole compound) in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but the pressure-sensitive adhesive composition (Non-volatile content) It is preferably less than 0.1% by weight, more preferably less than 0.01% by weight, and still more preferably less than 0.005% by weight with respect to 100% by weight.

  Examples of the tertiary amine include tertiary amine compounds such as triethylamine, benzyldimethylamine, and α-methylbenzyl-dimethylamine. Examples of the imidazole compound include 2-methylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 4-ethylimidazole, 4-dodecylimidazole, 2-phenyl-4-hydroxymethylimidazole, and 2-ethyl-4. -Hydroxymethylimidazole, 1-cyanoethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like.

  In addition, the adhesive composition of this invention may contain various additives other than the above in the range which does not affect pollution property. Examples of the various additives include pigments, fillers, leveling agents, dispersants, plasticizers, stabilizers, antioxidants, ultraviolet absorbers, ultraviolet stabilizers, anti-aging agents, and antiseptics.

  Although it does not specifically limit as said leveling agent, For example, an acetylene diol type compound (diol compound which has an acetylene bond in a molecule | numerator), a fluorocarbon modified polyacrylate, etc. are mentioned. The blending amount of the leveling agent (content in the pressure-sensitive adhesive composition of the present invention) is not particularly limited, but is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic emulsion polymer (A). More preferably, it is 0.1 to 5 parts by weight. In addition, the said leveling agent may be used independently and may use 2 or more types together.

  The pressure-sensitive adhesive composition of the present invention can be produced by mixing the acrylic emulsion polymer (A) and the compound (B). If necessary, the water-insoluble crosslinking agent (C), other crosslinking agents, and various additives may be mixed. In addition, the said mixing method can use the mixing method of a well-known and usual emulsion, Although it does not specifically limit, For example, stirring using a stirrer is preferable. Although stirring conditions are not specifically limited, For example, as for temperature, 10-50 degreeC is preferable, More preferably, it is 20-35 degreeC. The stirring time is preferably 5 to 30 minutes, more preferably 10 to 20 minutes. The stirring rotation speed is preferably 10 to 2000 rpm, more preferably 30 to 1000 rpm.

  In the above mixing, the timing of adding the compound (B) is not particularly limited, and the compound (B) may be added during the polymerization of the acrylic emulsion polymer (A), or the acrylic emulsion polymer (A after polymerization) ) And compound (B) may be mixed. The timing at which the water-insoluble crosslinking agent (C) is added is not particularly limited, but is preferably just before the application of the pressure-sensitive adhesive composition from the viewpoint of pot life.

  The pressure-sensitive adhesive composition obtained as described above is applied to at least one side of the transparent film substrate, and is dried as necessary to form an acrylic pressure-sensitive adhesive layer. A pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention on at least one side of the film substrate can be obtained. Crosslinking is performed by dehydrating in the drying step, heating the pressure-sensitive adhesive sheet after drying, or the like. In the pressure-sensitive adhesive sheet of the present invention, the acrylic pressure-sensitive adhesive layer is preferably formed by the so-called direct copying method in which the pressure-sensitive adhesive composition is directly applied to the surface of the transparent film substrate as described above. Since the acrylic pressure-sensitive adhesive layer has a high solvent-insoluble content, a so-called transfer method in which an acrylic pressure-sensitive adhesive layer is once formed on a release film and then transferred (bonded) to the transparent film substrate is used. Since sufficient anchorage (adhesiveness) of the acrylic pressure-sensitive adhesive layer may not be obtained, the direct copy method is preferably used. However, the pressure-sensitive adhesive sheet of the present invention may be a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention on at least one side of the substrate, and the production method is not particularly limited.

  The thickness of the acrylic pressure-sensitive adhesive layer (after crosslinking) in the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but is preferably 1 to 50 μm, more preferably 1 to 35 μm, and still more preferably 3 to 25 μm.

The solvent-insoluble content of the acrylic pressure-sensitive adhesive layer (after crosslinking) is not particularly limited, but is preferably 90% by weight or more, and more preferably 95% by weight or more. When the solvent-insoluble content is less than 90% by weight, transfer of contaminants to the adherend increases, whitening contamination may occur, and re-peelability may be insufficient (heavy release). Although the upper limit of the solvent insoluble content of the acrylic pressure-sensitive adhesive layer (after crosslinking) is not particularly limited, for example, 99% by weight is preferable.
In addition, the solvent insoluble matter of the said acrylic adhesive layer (after bridge | crosslinking) can be measured by the method similar to the measuring method of the solvent insoluble matter of the above-mentioned acrylic emulsion type polymer. Specifically, it can be measured by a method in which “acrylic emulsion polymer” is replaced with “acrylic pressure-sensitive adhesive layer (after crosslinking)” in the above-mentioned “method for measuring solvent-insoluble matter”.

  The glass transition temperature of the acrylic polymer (after crosslinking) forming the acrylic pressure-sensitive adhesive layer is not particularly limited, but is preferably −70 to −10 ° C., more preferably −70 to −20 ° C., and still more preferably. It is -70 to -40 degreeC, Most preferably, it is -70 to -60 degreeC. When the glass transition temperature exceeds −10 ° C., the adhesive strength is insufficient, and floating or peeling may occur during processing. Moreover, if it is less than -70 degreeC, there exists a possibility that it may peel heavily in a higher peeling speed (tensile speed) area | region, and work efficiency may fall. The glass transition temperature of the acrylic polymer (after crosslinking) that forms this acrylic pressure-sensitive adhesive layer can be adjusted, for example, by the monomer composition when preparing the acrylic emulsion polymer (A).

  The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive force (180 ° peel test) against a polarizing plate (triacetylcellulose (TAC) plate) (with a surface arithmetic average roughness Ra of 50 nm or less) at a tensile rate of 0.3 m / min. The peeling force when peeling the pressure-sensitive adhesive sheet attached to the polarizing plate) is preferably 0.01 to 5 N / 25 mm, more preferably 0.02 to 3 N / 25 mm, and still more preferably 0.03 to 2 N / mm. 25 mm, most preferably 0.04 to 1 N / 25 mm. When the adhesive strength exceeds 5 N / 25 mm, it is difficult to peel off the adhesive sheet in the manufacturing process of the polarizing plate or the liquid crystal display device, and the productivity and the handleability may be lowered. If it is less than 0.01 N / 25 mm, the pressure sensitive adhesive sheet may float or peel off during the production process, and the protective function as a pressure sensitive adhesive sheet for surface protection may be reduced. The arithmetic average roughness Ra can be measured using, for example, P-15 (contact type surface shape measuring device) manufactured by KLA Tencor. The surface roughness (arithmetic average roughness Ra) is not particularly limited, and can be measured, for example, under the conditions of a measurement length of 1000 μm, a scanning speed of 50 μm / second, a scanning frequency of once, and a load of 2 mg.

  Although the total light transmittance (according to JIS K7361-1) in the visible light wavelength region of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, it is preferably 80 to 97%, more preferably 85 to 95%. Further, the haze (according to JIS K7136) of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but is preferably 1.0 to 3.5%, more preferably 2.0 to 3.2%. When the total light transmittance and / or haze of the transparent film substrate is out of the above range, it tends to be difficult to perform an appearance inspection of the adherend.

The surface resistivity of the top coat layer surface of the transparent film substrate, that is, the top coat layer surface of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but is 100 × 10 ⁸ Ω / □ or less (for example, 0.1 × 10 ^{8 to} 100 × 10 ⁸ Ω / □), preferably 50 × 10 ⁸ Ω / □ or less (for example, 0.1 × 10 ⁸ to 50 × 10 ⁸ Ω / □), and more preferably 1 × 10 ^8. ~ 50 × 10 ⁸ Ω / □. When the surface resistivity is 100 × 10 ⁸ Ω / □ or less, it can be preferably used particularly as a surface protective film used in processing or transporting an article that dislikes static electricity such as a liquid crystal cell or a semiconductor device. The value of the surface resistivity can be calculated from the value of the surface resistance measured under an atmosphere of 23 ° C. and relative humidity 55% RH using a commercially available insulation resistance measuring device. Specifically, the value of the surface resistivity obtained by the surface resistivity measuring method described in the examples described later can be preferably employed.

Although the friction coefficient of the topcoat layer surface of the said transparent film base material, ie, the topcoat layer surface of the adhesive sheet of this invention, is not specifically limited, 0.4 or less is preferable. By controlling the friction coefficient to 0.4 or less, when a load is applied to the topcoat layer surface of the pressure-sensitive adhesive sheet (a load that causes a scratch (scratch)), the load is applied to the topcoat layer surface. It can be swept along and the frictional force can be reduced. Accordingly, it is possible to better prevent an event in which the top coat layer is cohesively broken or peeled off from the base layer (interface fracture) to cause a scratch. The lower limit value of the friction coefficient is not particularly limited. For example, 0.1 is preferable and 0.15 is more preferable in consideration of balance with other characteristics (appearance characteristics, printability, and the like). That is, although the said friction coefficient is not specifically limited, 0.1-0.4 are preferable, More preferably, it is 0.15-0.4.
The friction coefficient is a value obtained by rubbing the surface of the top coat layer of the transparent film substrate (or the pressure-sensitive adhesive sheet of the present invention) with a vertical load of 40 mN, for example, in a measurement environment of 23 ° C. and a relative humidity of 50% RH. Can be adopted. As a method of reducing (adjusting) the friction coefficient, a method of adding various lubricants (leveling agents, etc.) to the topcoat layer, a method of increasing the crosslink density of the topcoat layer by adding a crosslinking agent or adjusting film forming conditions Etc. can be adopted as appropriate.

The surface of the top coat layer of the transparent film substrate, that is, the surface of the top coat layer of the pressure-sensitive adhesive sheet of the present invention can be easily printed with oil-based ink or water-based ink (for example, using an oil-based marking pen) (“printability” It may be referred to as “. Such a surface protective film (adhesive sheet) is used to identify an identification number or the like of an adherend to be protected in the process of processing or transporting an adherend (for example, an optical component) bonded with the surface protective film. Suitable for displaying on a surface protective film. Therefore, the pressure-sensitive adhesive sheet of the present invention is preferably a surface protective film that is excellent in printability in addition to appearance characteristics, and is particularly high in printing for oil-based inks that are alcohol-based and contain pigments. It is preferable to have properties. Further, it is preferable that the printed ink has a characteristic that it is difficult to remove by rubbing or transfer (sometimes referred to as “print adhesion”). The degree of the printability can be grasped by, for example, the following printability evaluation.
(Printability (print adhesion) evaluation)
After printing on the surface of the topcoat layer using an X stamper manufactured by Shachihata Co., Ltd. in a measurement environment of 23 ° C. and 50% RH, a cellophane adhesive tape manufactured by Nichiban Co., Ltd. , Width 19 mm), and then peeled under conditions of a peeling speed of 30 m / min and a peeling angle of 180 °. Then, the surface after peeling was visually observed, and x (printability failure) when 50% or more of the print area was peeled off, and ○ (good printability) when 50% or more of the print area remained without peeling. ).

Furthermore, the surface of the top coat layer of the transparent film substrate, that is, the surface of the top coat layer of the pressure-sensitive adhesive sheet of the present invention is visible even if the print is wiped with alcohol (for example, ethyl alcohol) when the print is corrected or erased. It is preferable to have a solvent resistance that does not cause noticeable changes (whitening). The degree of the solvent resistance can be grasped by, for example, the following solvent resistance evaluation.
(Solvent resistance evaluation)
In a room (dark room) where outside light is blocked, the top coat layer surface is wiped 15 times with a cloth (cloth) soaked with ethyl alcohol, and the appearance is visually observed. As a result, when no difference in appearance was observed between the part wiped with ethyl alcohol and the other part (no change in appearance due to wiping with ethyl alcohol), ○ (good solvent resistance) The case where wiping unevenness was confirmed was evaluated as x (poor solvent resistance).

  The pressure-sensitive adhesive sheet of the present invention is excellent in the whitening contamination inhibiting property of the adherend. This can be evaluated, for example, as follows. The pressure-sensitive adhesive sheet is bonded to a polarizing plate (trade name “SEG1425DUHC”, manufactured by Nitto Denko Corporation) under the conditions of 0.25 MPa and 0.3 m / min, left at 80 ° C. for 4 hours, and then peeled off. . The polarizing plate after the pressure-sensitive adhesive sheet is peeled is further left for 12 hours in an environment of 23 ° C. and 90% RH, and then the surface is observed. At this time, it is preferable that no whitening is observed on the surface of the polarizing plate. When whitening occurs on the polarizing plate as an adherend under humidification conditions (high humidity conditions) after sticking / peeling the pressure-sensitive adhesive sheet, low contamination is not sufficient for use as a surface protective film for optical members.

  The pressure-sensitive adhesive sheet of the present invention can be a wound body, and can be wound up in a roll shape with the release film (separator) protecting the acrylic pressure-sensitive adhesive layer. The back side of the pressure-sensitive adhesive sheet (the surface opposite to the side where the acrylic pressure-sensitive adhesive layer is provided, usually the surface of the topcoat layer) is a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent. A release treatment and / or antifouling treatment with an agent, silica powder or the like may be performed, and a back treatment layer (release treatment layer, antifouling treatment layer, etc.) may be provided. As the pressure-sensitive adhesive sheet of the present invention, an acrylic pressure-sensitive adhesive layer / transparent film substrate / back treatment layer is preferable.

  The pressure-sensitive adhesive sheet of the present invention is excellent in adhesiveness and removability (easy releasability), and can be re-removed, so that it can be used for re-removal (for re-removal). That is, the adhesive sheet of the present invention is used for re-peeling [for example, masking tape for architectural curing, masking tape for automobile coating, masking tape for electronic parts (lead frame, printed circuit board, etc.), masking tape for sandblasting, etc. Surface protection film for aluminum sash, surface protection film for optical plastic, surface protection film for optical glass, surface protection film for automobile protection, surface protection film for metal plate, back grind tape, pellicle fixing Tape, dicing tape, lead frame fixing tape, cleaning tape, dust removal tape, carrier tape, cover tape, and other semiconductor / electronic parts manufacturing process adhesive tapes, electronic equipment and electronic parts packaging tapes, transportation Temporary fixing tape , Bundling tapes, preferably used in the label such], and the like.

  Furthermore, the pressure-sensitive adhesive sheet of the present invention has excellent appearance characteristics because appearance defects of the pressure-sensitive adhesive layer such as dents and bubble defects are reduced and it does not look whitish despite having a top coat layer. Moreover, the adhesive sheet of this invention can exhibit the outstanding scratch resistance and antistatic property by having the said topcoat layer. For this reason, the pressure-sensitive adhesive sheet of the present invention constitutes a panel such as a liquid crystal display, organic electroluminescence (organic EL), field emission display, etc., which requires particularly excellent appearance characteristics, scratch resistance, and antistatic properties. For surface protection applications (surface protection films for optical members, etc.) of optical members (optical plastics, optical glass, optical films, etc.) such as polarizing plates, retardation plates, antireflection plates, wave plates, optical compensation films, brightness enhancement films, etc. Preferably used. However, the application is not limited to this. Surface protection and damage prevention in the manufacture of microfabricated parts such as semiconductors, circuits, various printed boards, various masks, and lead frames, or removal of foreign substances, masking, etc. Can also be used.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Production Example 1 [Production Example of Transparent Film Base]
(Preparation of composition for forming topcoat layer)
After charging 25 g of toluene into the reactor and raising the temperature in the reactor to 105 ° C., 30 g of methyl methacrylate (MMA), 10 g of n-butyl acrylate (BA), 5 g of cyclohexyl methacrylate (CHMA), azobisisobutyl A solution mixed with 0.2 g of ronitrile was continuously added dropwise to the reactor over 2 hours. After completion of the dropwise addition, the temperature in the reactor was adjusted to 110 to 115 ° C. and kept at the same temperature for 3 hours to carry out a copolymerization reaction. After 3 hours, a mixed solution of 4 g of toluene and 0.1 g of azobisisobutyronitrile was dropped into the reactor and kept at the same temperature for 1 hour. Thereafter, the temperature in the reactor is cooled to 90 ° C., toluene is added to adjust to NV 5 wt%, and a solution containing 5 wt% acrylic polymer (binder polymer 1; Tg 48 ° C.) as a binder in toluene ( A binder solution 1) was prepared.
Next, 2 g of binder solution 1 (including 0.1 g of binder polymer 1) and 40 g of ethylene glycol monoethyl ether were added to a beaker having a capacity of 150 mL and stirred and mixed. Furthermore, 1.2 g of NV 4.0 wt% conductive polymer solution 1 (aqueous solution) containing polyethylene dioxythiophene (PEDT) and polystyrene sulfonate (PSS), 55 g of ethylene glycol monomethyl ether, and polyether were added to this beaker. Modified polydimethylsiloxane-based leveling agent (lubricant solution) (BYK Chemie, trade name “BYK-300”, NV 52% by weight) 0.05 g and melamine cross-linking agent (manufactured by Sanwa Chemical Co., Ltd., trade name “ Nicalac MW-30M ”(non-volatile content: 100%) (0.02 g) was added, and the mixture was stirred for about 20 minutes and mixed well. Thus, the top containing 48 parts by weight of conductive polymer, 26 parts by weight of lubricant, and 20 parts by weight of melamine crosslinking agent (all in terms of solid content) with respect to 100 parts by weight of binder polymer 1 (acrylic polymer). A composition for forming a coat layer (NV: 0.2% by weight) was prepared.

(Formation of top coat layer)
Using a bar coater, the topcoat layer forming composition is applied to the corona-treated surface of a transparent polyethylene terephthalate film (PET film) having a thickness of 38 μm, a width of 30 cm, and a length of 40 cm. It applied so that the thickness after drying might be set to about 10 nm. The coated material was heated at 130 ° C. for 2 minutes and dried to form a topcoat layer on one surface of the PET film. Thus, the transparent film base material (it may be called "the base material 1") which has a transparent topcoat layer on the single side | surface of PET film was produced.

Production Example 2 [Production Example of Transparent Film Base]
In Production Example 1, the amount of conductive polymer solution 1 used was changed from 1.2 g to 2.5 g, and the amount of ethylene glycol monomethyl ether used was changed from 55 g to 17 g. The topcoat layer forming solution was applied so that the thickness after drying was about 20 nm. About the other point, it carried out similarly to manufacture example 1, and produced the transparent film base material (it may be called "the base material 2") which has a transparent topcoat layer on the single side | surface of PET film.

Production Example 3 [Production Example of Transparent Film Base]
In Production Example 1, the amount of ethylene glycol monoethyl ether used was changed from 40 g to 19 g, the amount of conductive polymer solution 1 used was changed from 1.2 g to 0.7 g, and ethylene glycol monomethyl ether was not used. . The topcoat layer forming solution was applied so that the thickness after drying was about 40 nm. About the other point, it carried out similarly to manufacture example 1, and produced the transparent film base material (it may be called "the base material 3") which has a transparent topcoat layer on the single side | surface of PET film.

Production Example 4 [Production Example of Transparent Film Base]
The amount of ethylene glycol monoethyl ether used was changed from 19 g to 15 g. The topcoat layer forming solution was applied so that the thickness after drying was about 50 nm. About the other point, it carried out similarly to manufacture example 3, and produced the transparent film base material (it may be called "the base material 4") which has a transparent topcoat layer on the single side | surface of PET film.

Production Example 5 [Production Example of Transparent Film Base]
(Preparation of composition for forming topcoat layer)
After charging toluene 25g into the reactor and raising the temperature in the reactor to 105 ° C, methyl methacrylate (MMA) 32g, n-butyl acrylate (BA) 5g, methacrylic acid (MAA) 0.7g, cyclohexyl methacrylate A solution in which 5 g of (CHMA) and 0.2 g of azobisisobutyronitrile were mixed was continuously added dropwise to the reactor over 2 hours. After completion of the dropwise addition, the temperature in the reactor was adjusted to 110 to 115 ° C. and maintained at the same temperature for 3 hours to carry out a copolymerization reaction. After 3 hours, a mixed solution of 4 g of toluene and 0.1 g of azobisisobutyronitrile was dropped into the reactor and kept at the same temperature for 1 hour. Thereafter, the temperature in the reactor was cooled to 90 ° C., and diluted by adding 31 g of toluene. In this way, a solution (binder solution 2) containing about 42% by weight of an acrylic polymer (binder polymer 2; Tg 72 ° C.) as a binder in toluene was prepared.
Next, 5.5 g of binder solution 2 (including 2.3 g of binder polymer 2) and 30 g of ethylene glycol monoethyl ether were placed in a beaker having a capacity of 150 mL and mixed with stirring. Furthermore, 14 g of NV 1.3 wt% conductive polymer solution 2 (aqueous solution) containing PEDT and PSS, 6 g of ethylene glycol monomethyl ether, and 0.5 g of a lubricant solution (BYK-300) were added to this beaker, and the mixture was stirred for about 30 minutes. And mixed well. In this way, a composition for forming a topcoat layer containing 8 parts by weight of a conductive polymer and 11 parts by weight of a lubricant (both based on solid content) is prepared with respect to 100 parts by weight of binder polymer 2 (acrylic polymer). did. In addition, the crosslinking agent is not mix | blended with this composition for topcoat layer formation.

(Formation of top coat layer)
The top coat layer forming composition is dried on a corona-treated surface of a transparent polyethylene terephthalate film (PET film) having a thickness of 38 μm, a width of 30 cm, and a length of 40 cm, which is corona-treated on one side, using a bar coater. The thickness of the coating was about 610 nm. The coated material was heated to 80 ° C. for 2 minutes and dried to form a topcoat layer. Thus, the transparent film base material (it may be called "the base material 5") which has a transparent topcoat layer on the single side | surface of PET film was produced.

Production Example 6 [Production Example of Transparent Film Base]
(Preparation of composition for forming topcoat layer)
The reactor was charged with 25 g of toluene and the temperature in the reactor was raised to 105 ° C., then 30 g of methyl methacrylate (MMA), 10 g of n-butyl acrylate (BA), 5 g of cyclohexyl methacrylate (CHMA), hydroxyethyl methacrylate ( (HEMA) 5 g and azobisisobutyronitrile 0.2 g were mixed dropwise into the reactor continuously over 2 hours. After completion of the dropwise addition, the temperature in the reactor was adjusted to 110 to 115 ° C. and maintained at the same temperature for 3 hours to carry out a copolymerization reaction. After 3 hours, a mixed solution of 4 g of toluene and 0.1 g of azobisisobutyronitrile was dropped into the reactor and kept at the same temperature for 1 hour. Thereafter, the temperature in the reactor was cooled to 90 ° C., and diluted with toluene. In this way, a solution (binder solution 3) containing about 5% by weight of an acrylic polymer (binder polymer 3; Tg 49 ° C.) as a binder in toluene was prepared.
Next, 2 g of the binder solution 3 (including 0.1 g of the binder polymer 3) and 40 g of ethylene glycol monoethyl ether were added to a beaker having a capacity of 150 mL and stirred and mixed. Furthermore, 1.2 g of NV 4.0 wt% conductive polymer solution 1 (aqueous solution) containing polyethylene dioxythiophene (PEDT) and polystyrene sulfonate (PSS), 55 g of ethylene glycol monomethyl ether, and polyether were added to this beaker. Modified polydimethylsiloxane-based leveling agent (lubricant solution) (BYK Chemie, trade name “BYK-300”, NV 52% by weight) 0.05 g and melamine cross-linking agent (manufactured by Sanwa Chemical Co., Ltd., trade name “ Nicalac MW-30M ”) and 0.02 g were added, and the mixture was stirred for about 20 minutes and mixed well. Thus, with 100 parts by weight of the binder polymer 3 (acrylic polymer), the top containing 48 parts by weight of the conductive polymer, 26 parts by weight of the lubricant, and 20 parts by weight of the melamine crosslinking agent (all in terms of solid content). A composition for forming a coat layer (NV: 0.2% by weight) was prepared.

(Formation of top coat layer)
Using a bar coater, the topcoat layer forming composition is applied to the corona-treated surface of a transparent polyethylene terephthalate film (PET film) having a thickness of 38 μm, a width of 30 cm, and a length of 40 cm. It applied so that the thickness after drying might be set to about 8 nm. The coated material was heated at 130 ° C. for 2 minutes and dried to form a topcoat layer on one surface of the PET film. Thus, the transparent film base material (it may be called "the base material 6") which has a transparent topcoat layer on the single side | surface of PET film was produced.

  In Table 1, the composition of the topcoat layer in the transparent film base materials (base materials 1 to 6) produced above and the evaluation results of these transparent film base materials according to the evaluation procedure described later are shown.

Production Example 7 [Production Example of Water-dispersed Acrylic Adhesive Composition]
(Preparation of acrylic emulsion polymer)
In a container, as shown in Table 2, 90 parts by weight of water and 96 parts by weight of 2-ethylhexyl acrylate (2EHA), 4 parts by weight of acrylic acid (AA), nonionic anionic reactive emulsifier (Daiichi Kogyo Seiyaku ( Co., Ltd., trade name “AQUALON HS-10”) 3 parts by weight were blended and then stirred and mixed with a homomixer to prepare a monomer emulsion.
Next, in a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, 50 parts by weight of water, 0.01 part by weight of a polymerization initiator (ammonium persulfate), and 10% of the monomer emulsion prepared above %, And emulsion polymerization was carried out at 75 ° C. for 1 hour while stirring. Thereafter, 0.05 parts by weight of a polymerization initiator (ammonium persulfate) was further added, and then all of the remaining monomer emulsion (amount corresponding to 90% by weight) was added over 3 hours with stirring. The reaction was carried out at 0 ° C. for 3 hours. Next, this was cooled to 30 ° C. and adjusted to pH 8 by adding ammonia water having a concentration of 10% by weight to prepare an aqueous dispersion of an acrylic emulsion polymer.

(Preparation of water-dispersed acrylic pressure-sensitive adhesive composition)
1.0 weight of "Adekapluronic 25R-1" which is the compound (B) is added to 100 parts by weight of the acrylic emulsion polymer (solid content) in the aqueous dispersion of the acrylic emulsion polymer obtained above. Part, "EFKA-3570" as a leveling agent, 0.2 parts by weight, epoxy-based crosslinking agent which is a water-insoluble crosslinking agent [Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad-C", 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, epoxy equivalent: 110, functional group number: 4] 3 parts by weight are stirred and mixed using a stirrer under stirring conditions of 23 ° C., 300 rpm, 10 minutes, and water-dispersed. An acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 1”) was prepared.

Production Example 8 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, a water-dispersed acrylic resin was prepared in the same manner as in Production Example 7 except that 3 parts by weight of “Adekaria soap SE-10N” was used as the reactive emulsifier instead of “Aqualon HS-10”. A pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 2”) was prepared.

Production Example 9 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, the monomer raw material of the acrylic emulsion polymer was changed to 92 parts by weight of 2-ethylhexyl acrylate (2EHA), 4 parts by weight of methyl methacrylate (MMA), and 4 parts by weight of acrylic acid (AA). A water-dispersed acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 3”) was prepared in the same manner as in Production Example 7.

Production Example 10 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, in the same manner as in Production Example 8 except that 0.5 part by weight of “Adekapluronic 17R-3” was used instead of “Adekapluronic 25R-1” as the compound (B), A dispersion-type acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 4”) was prepared.

Production Example 11 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, as compound (B), 0.5 parts by weight of “PPO-PEO-PPO” was used instead of “Adekapluronic 25R-1”, and as water-insoluble crosslinking agent (C), A water-dispersed acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 5”) in the same manner as in Production Example 7, except that 3 parts by weight of “tetrad-X” was used instead of “tetrad-C”. ) Was prepared.

Production Example 12 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, a water-dispersed acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 6”) was prepared in the same manner as in Production Example 7 except that the copolymer (B) was not used. Prepared).

Production Example 13 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, production examples except that a compound other than the compound (B) (0.5 parts by weight of “POLYRan (EO-PO)”) was used instead of the copolymer as the compound (B). In the same manner as in No. 7, a water-dispersed acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 7”) was prepared.

Production Example 14 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, Production Example 7 except that a compound other than the compound (B) (3.0 parts by weight of “PEO-PPO-PEO”) was used instead of the copolymer as the compound (B). In the same manner, a water-dispersed acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 8”) was prepared.

Production Example 15 [Production Example of Water-dispersed Acrylic Adhesive Composition]
As shown in Table 2, the compounding amount of “Adekapluronic 25R-1” which is the compound (B) is changed to 0.1 parts by weight with respect to 100 parts by weight of the acrylic emulsion polymer (solid content). Prepared a water-dispersed acrylic pressure-sensitive adhesive composition (sometimes referred to as “pressure-sensitive adhesive 9”) in the same manner as in Production Example 7.

  Table 2 shows the composition of the water-dispersed acrylic pressure-sensitive adhesive composition (pressure-sensitive adhesives 1 to 9) prepared above.

Example 1
As shown in Table 3, the water-dispersed acrylic pressure-sensitive adhesive composition (pressure-sensitive adhesive 1) obtained above was placed on the side opposite to the topcoat layer of the transparent film base material (base material 1) obtained above. Using an applicator manufactured by Tester Sangyo Co., Ltd., the surface is coated (coated) so that the thickness after drying is 15 μm, and then dried in a hot air circulation oven at 120 ° C. for 2 minutes, and the pressure-sensitive adhesive after drying After bonding the silicone-treated surface of a PET film (Mitsubishi Resin Co., Ltd., “MRF38”) surface-treated with silicone to the layer, it was cured (aged) at 50 ° C. for 3 days to obtain an adhesive sheet.

Examples 2-9, Comparative Examples 1-6
As shown in Table 3, the type of the water-dispersed acrylic pressure-sensitive adhesive composition and the transparent film substrate was changed, and a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.
The trade name “Diafoil T100G” (manufactured by Mitsubishi Chemical Corporation) used as a base material in Comparative Example 6 is a PET film (antistatic treated PET film) having an antistatic layer on one surface. . The antistatic layer contains a compound having an ammonium base as an antistatic agent.

[Evaluation]
About the transparent film base material produced above and the adhesive sheet obtained by the Example and the comparative example, it evaluated by the following measuring method or evaluation method. In addition, the solvent insoluble content of the acrylic emulsion polymer, the weight average molecular weight of the solvent soluble content of the acrylic emulsion polymer, and the solvent insoluble content of the acrylic pressure-sensitive adhesive layer (after crosslinking) were measured by the above-described measurement methods. .
The evaluation results are shown in Tables 1-3.

(1) Topcoat layer thickness (average thickness and thickness variation)
The thickness of the topcoat layer was measured by observing a cross section of the transparent film substrate produced in the production example with a transmission electron microscope (TEM).
On the other hand, the surface of the topcoat layer of the transparent film substrate is subjected to sulfur atoms (PEDT and PSS contained in the topcoat layer) using an X-ray fluorescence analyzer (manufactured by Rigaku, XRF apparatus, model “ZSX-100e”). The peak intensity of (derived) was measured. X-ray fluorescence analysis was performed under the following conditions.
[X-ray fluorescence analysis]
Apparatus: XRF apparatus manufactured by Rigaku, model “ZSX-100e”
X-ray source: Vertical Rh tube Analysis range: within a circle with a diameter of 30 mm Detection X-ray: S-Kα
Spectroscopic crystal: Ge crystal Output: 50 kV, 70 mA
Based on the thickness (actual value) of the topcoat layer obtained by the TEM observation and the result of the fluorescent X-ray analysis, a calibration curve for grasping the thickness of the topcoat layer from the peak intensity in the fluorescent X-ray analysis was prepared.
Using the calibration curve, the thickness of the top coat layer of the transparent film substrate was measured. Specifically, along a straight line that crosses the region in which the topcoat layer is formed in the width direction (a direction perpendicular to the moving direction of the bar coater), 1/6 of the width from one end to the other end in the width direction. 2/6, 3/6, 4/6, and 5/6 advanced X-ray fluorescence analysis, the results (X-ray intensity of sulfur atoms (kcps)), topcoat layer composition (PEDT and PSS) Content) and the calibration curve, the thickness of the topcoat layer at the five measurement positions was determined. The average thickness D _ave was measured by arithmetically averaging the thickness of the top coat layer at the above five measurement points. The thickness variation ΔD is obtained by calculating the average thickness D _ave and the maximum value D _max and the minimum value D _min among the thicknesses of the top coat layer at the five measurement points, as follows: ΔD = (D _max −D _min ) / D _ave × 100 (%);

(2) Variation in X-ray intensity on the surface of the topcoat layer By arithmetically averaging the X-ray intensity (kcps) of sulfur atoms obtained by performing fluorescent X-ray analysis at each of the above positions (5 measurement positions) The average X-ray intensity I _ave was determined. Further, the average X-ray intensity I _ave and the maximum value I _max and the minimum value I _min of the X-ray intensity at each position (five measurement positions) are expressed by the following equation: ΔI = (I _max −I _min ) / I By substituting into _ave × 100 (%) ;, the X-ray intensity variation ΔI was calculated.

(3) Appearance of transparent film substrate The transparent film substrate (base materials 1 to 6) in a room (light room) having a window where external light enters, at a window that is not exposed to direct sunlight during sunny days. The back surface (surface on the topcoat layer side) of the film was visually observed. Based on these observation results, the appearance of the transparent film substrate was evaluated according to the following criteria.
○ (Good appearance): No unevenness or streaks were confirmed. × (Poor appearance): Unevenness or streaks were confirmed.

(4) Surface resistivity of topcoat layer surface In accordance with JIS K6911, using an insulation resistance meter (trade name “Hiresta-up MCP-HT450” manufactured by Mitsubishi Chemical Analytech Co., Ltd.), 23 ° C., relative humidity In a 55% atmosphere, the surface resistance Rs of the surface on the topcoat layer side of the transparent film substrate (base materials 1 to 6) prepared above was measured. The applied voltage was 100 V, and the surface resistance Rs was read 60 seconds after the start of measurement. From the results, the surface resistivity was calculated according to the following formula.
ρs = Rs × E / V × π (D + d) / (D−d)
Where ρs is the surface resistivity (Ω / □), Rs is the surface resistance (Ω), E is the applied voltage (V), V is the measured voltage (V), and D is the inner diameter of the annular electrode on the surface. (Cm) and d represent the outer diameter (cm) of the inner circle of the surface electrode, respectively.

(5) Scratch resistance on the surface of the topcoat layer A sample of 10 cm ² (width 10 cm × length 10 cm) was cut out from the transparent film substrate (base materials 1 to 6) prepared above. A tester rubs the back surface (surface on the topcoat layer side) of the sample with a nail in a room (light room) having a window through which external light enters, and scratch resistance was evaluated based on how scratches were caused by this. Specifically, when the back surface of the sample after rubbing with a nail is observed with an optical microscope, the presence of falling off debris in the topcoat layer is confirmed as x (poor scratch resistance). The case where no was confirmed was evaluated as ○ (good scratch resistance).

(6) Prevention of increase in adhesive strength (initial adhesive strength)
The pressure-sensitive adhesive sheets (sample size: 25 mm width × 100 mm length) obtained in Examples and Comparative Examples were 0.25 MPa, 0.00 mm using a bonding machine (manufactured by Tester Sangyo Co., Ltd., small bonding machine). Under conditions of 3 m / min, a polarizing plate (material: triacetyl cellulose (TAC), surface arithmetic average roughness Ra is about 21 nm in the MD direction, about 31 nm in the TD direction, and an average of about 26 nm in the MD direction and the TD direction. Pasted together).
Using the above-mentioned sample of the pressure-sensitive adhesive sheet and the polarizing plate, after leaving for 20 minutes in an environment of 23 ° C. and 50% RH, a 180 ° peel test is performed according to the following conditions, and the pressure-sensitive adhesive strength (N / 25 mm) was measured and designated as “initial adhesive strength”.
(Adhesion after storage at 40 ° C for 1 week)
The pressure-sensitive adhesive sheets (sample size: 25 mm width × 100 mm length) obtained in Examples and Comparative Examples were 0.25 MPa, 0.00 mm using a bonding machine (manufactured by Tester Sangyo Co., Ltd., small bonding machine). Under conditions of 3 m / min, a polarizing plate (material: triacetyl cellulose (TAC), surface arithmetic average roughness Ra is about 21 nm in the MD direction, about 31 nm in the TD direction, and an average of about 26 nm in the MD direction and the TD direction. Pasted together).
Using the above-mentioned adhesive sheet and polarizing plate bonded sample, it was stored in an environment of 40 ° C. for 1 week, then left in an environment of 23 ° C. and 50% RH for 2 hours, and then subjected to a 180 ° peel test according to the following conditions. Then, the adhesive strength (N / 25 mm) of the adhesive sheet to the polarizing plate was measured, and was defined as “adhesive strength after pasting and storage at 40 ° C. for 1 week”.
The 180 ° peel test was performed using a tensile tester in an environment of 23 ° C. and 50% RH at a tensile speed of 0.3 m / min.
If the difference between the initial adhesive strength and the adhesive strength after storage at 40 ° C. for 1 week [(Adhesive strength after storage at 40 ° C. for 1 week) − (initial adhesive strength)] is 0.10 N / 25 mm or less, the increase in adhesive strength is prevented. It can be judged that it is excellent in property.

(7) Whitening of adhesive sheet under humidified storage (whitening property)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were allowed to stand in an environment of 50 ° C. and 95% RH for 24 hours (humidified storage), and then “Digital Haze Meter (DIGITAL HAZEMETER) NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd. The haze value was measured ("Haze value after humidification storage"). The measurement was performed within 3 minutes after removing the sample from the environment of 50 ° C. × 95% RH. For comparison, the haze value before humidification storage was also measured (referred to as “the haze value before humidification storage”).

(8) Appearance of adhesive sheet (appearance characteristics)
The state of the acrylic pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was visually observed, and the number of defects (dents and bubbles) within the observation range of 10 cm long × 10 cm wide was measured. Together with the evaluation results of the appearance of the transparent film substrate, the appearance (appearance characteristics) of the pressure-sensitive adhesive sheet was comprehensively evaluated according to the following criteria.
Appearance of the pressure-sensitive adhesive sheet is poor (x): When the appearance of the transparent film substrate is poor, or when the appearance of the transparent film substrate is good, but the number of the above defects is 101 or more Appearance is good (O): When the appearance of the transparent film substrate is good and the number of the above defects is 0 to 100

The abbreviations used in Tables 2 and 3 are as follows.
Hereinafter, the ratio of “total weight of EO” to “total weight of compound (B)” is expressed as “EO content”.
[Raw material monomer]
2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate AA: acrylic acid [emulsifier]
HS-10: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name “AQUALON HS-10” (nonionic anionic reactive emulsifier)
SE-10N: manufactured by ADEKA Corporation, trade name “ADEKA rear soap SE-10N” (nonionic anionic reactive emulsifier)
[Crosslinking agent]
Tetrad C: manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name “TETRAD-C (Tetrad-C)” (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, epoxy equivalent: 110, number of functional groups: 4 )
Tetrad X: Trade name “TETRAD-X (Tetrad-X)” (1,3-bis (N, N-diglycidylaminomethyl) benzene, manufactured by Mitsubishi Gas Chemical Company, Inc., epoxy equivalent: 100, number of functional groups: 4 )
[Compound (B)]
Adeka Pluronic 25R-1: Product name "Adeka Pluronic 25R-1" manufactured by ADEKA Corporation (number average molecular weight 2800, EO content 10% by weight, active ingredient 100% by weight)
Adeka Pluronic 17R-3: Product name “Adeka Pluronic 17R-3” manufactured by ADEKA Corporation (number average molecular weight 2000, EO content 30% by weight, active ingredient 100% by weight)
PPO-PEO-PPO: manufactured by SIGMA-ALDRICH (Sigma-Aldrich), poly (propylene glycol) -block-poly (ethylene glycol) -block-poly (propylene glycol) (number average molecular weight 2000, EO content 50% by weight , Active ingredient 100% by weight)
[Compounds other than compound (B)]
POLYRan (EO-PO): manufactured by SIGMA-ALDRICH (Sigma-Aldrich), poly [ethylene glycol-ran-propylene glycol] (number average molecular weight 2500, EO content 75% by weight, active ingredient 100% by weight)
PEO-PPO-PEO: manufactured by SIGMA-ALDRICH (Sigma-Aldrich), poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (number average molecular weight 1900, EO content 50% by weight , Active ingredient 100% by weight)
[Leveling agent]
EFKA-3570: BASF, neutralized fluorocarbon-modified polymer [base material (transparent film base material)]
T100G: Antistatic-treated PET film, trade name “Diafoil T100G” (manufactured by Mitsubishi Chemical Corporation)

As is clear from the results in Table 3, the pressure-sensitive adhesive sheets (Examples) satisfying the provisions of the present invention had a good appearance, and the increase in adhesive strength over time after application was small. Moreover, it had excellent antistatic properties and scratch resistance. Furthermore, it was not whitened when stored under humidification.
On the other hand, a comparative example (Comparative Examples 1 to 3) in which the compound (B) is not added, and a comparative example (Comparative Example 4) in which the average thickness and / or thickness variation of the topcoat layer of the substrate do not satisfy the provisions of the present invention. In 5), the appearance of the pressure-sensitive adhesive sheet was poor. Moreover, the comparative example (comparative example 5) which does not contain a melamine type crosslinking agent as a structural component of a topcoat layer was inferior also in scratch resistance. In Comparative Example (Comparative Example 2) using a compound other than Compound (B) in place of Compound (B), a large increase in haze value was observed due to humid storage, and whitening of the pressure-sensitive adhesive sheet was confirmed under humid storage. It was. Furthermore, when the antistatic layer of the base material is not a topcoat layer having a structure containing polythiophene, an acrylic resin, and a melamine-based crosslinking agent (Comparative Example 6), an increase in haze value due to humidification storage is observed, and It was inferior in scratch property.

Claims (4)

A pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer on at least one side of a transparent film substrate,
The transparent film substrate has a base layer made of a resin material, and a topcoat layer provided on the first surface of the base layer,
The top coat layer is composed of polythiophene, an acrylic resin, and a melamine-based cross-linking agent, the average thickness _Dave is 2 to 50 nm, and the thickness variation ΔD is 40% or less,
The acrylic pressure-sensitive adhesive layer is composed of (meth) acrylic acid alkyl ester and a carboxyl group-containing unsaturated monomer as essential raw material monomers, and the content of (meth) acrylic acid alkyl ester in the total amount of raw material monomers is 70. Acrylic polymerized using a reactive emulsifier containing -99.5% by weight, a carboxyl group-containing unsaturated monomer content of 0.5 to 10% by weight, and containing a radical polymerizable functional group in the molecule A pressure-sensitive adhesive layer formed from a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling containing an emulsion polymer (A) and a compound (B) represented by the following formula (I) Sheet.
_{^{R 1 O- (PO) a -}} (EO) b - (PO) c -R 2 (I)
(Wherein R ¹ and R ² represent a linear or branched alkyl group or a hydrogen atom. PO represents an oxypropylene group, EO represents an oxyethylene group. A, b and c are (Each is a positive integer. The addition form of EO and PO is a block type.)   The pressure-sensitive adhesive sheet according to claim 1, wherein the resin material constituting the base layer comprises polyethylene terephthalate or polyethylene naphthalate as a main resin component.   The pressure-sensitive adhesive according to claim 1 or 2, wherein the water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling further comprises a water-insoluble crosslinking agent (C) having two or more functional groups capable of reacting with a carboxyl group in the molecule. Sheet.   It is a surface protective film for optical members, The adhesive sheet of any one of Claims 1-3.