JP5617987B2 - Antistatic acrylic adhesive - Google Patents

Description

  The present invention relates to an antistatic pressure-sensitive adhesive and a method for producing the pressure-sensitive adhesive. In detail, this invention relates to the adhesive suitable for the surface protection film for protecting the to-be-adhered body surface mechanically and electrically for a predetermined period. More specifically, the pressure-sensitive adhesive of the present invention is suitably used for forming a surface-protective pressure-sensitive adhesive film for optical parts such as liquid crystal panels, plasma displays, polarizing plates, and CRTs (CRTs).

  Conventionally, the surface of various displays such as word processors, computers, mobile phones, TVs, or optical components such as polarizing plates and laminates equivalent thereto, electronic substrates, and the like, usually for the purpose of surface protection and imparting functionality, A transparent surface protective film (base film) such as polyester or polypropylene is laminated via an adhesive.

  In many cases, these surface protective pressure-sensitive adhesive films are peeled and removed after finishing the role of surface protection, for example, after the incorporation of a liquid crystal display or the like is completed. However, there is a problem that static electricity is generated when the surface protective adhesive film is peeled off and entraps surrounding dust. Furthermore, there may be a problem that the liquid crystal and the electronic circuit are destroyed due to peeling electrification generated when the surface protective adhesive film is peeled off.

Therefore, various measures as described below have been proposed as means for imparting antistatic properties to the surface protective adhesive film.
For example,
(1) imparting antistatic properties to the substrate film itself constituting the surface protective adhesive film;
(2) Between the base film and the pressure-sensitive adhesive layer constituting the surface protective pressure-sensitive adhesive film, on the side where the pressure-sensitive adhesive layer of the base film is not laminated, or between the base film and the pressure-sensitive adhesive layer In between, provide a layer having antistatic performance,
(3) Giving antistatic properties to the pressure-sensitive adhesive layer constituting the surface protective pressure-sensitive adhesive film, and the like.

The method (1) is a method in which a conductive base material is prepared by kneading an anionic compound such as an organic sulfonate group, a metal powder, or a conductive filler such as carbon black with a thermoplastic resin such as polyester or polyethylene as a raw material for the base film. In this case, the transparency of the base film is lowered or the film is colored.
By the way, while the surface protective adhesive film is stuck on the adherend, the surface protective appearance of the adherend needs to be continuously inspected through the adhesive film. Therefore, the surface protective pressure-sensitive adhesive film pressure-sensitive adhesive sheet itself is required to be excellent in transparency and optically free from defects.
Therefore, when the surface protection adhesive film using an antistatic agent containing base film is stuck on a to-be-adhered body, there exists a problem that an adherend surface becomes difficult to see. There is also a problem that the base film becomes expensive.

The method (2) has various variations as described below (Japanese Patent Laid-Open Nos. 7-26223, 11-256116, 2001-219520, 2002-060707). JP, 2002-275296, A, etc.).
(2-1) depositing a metal compound on at least one surface of the base film;
(2-2) An anionic surfactant such as a quaternary ammonium salt, a long-chain alkyl compound having a sulfonate group, a thiophene derivative, or a nitrogen element ionized in the main chain on at least one surface of the base film And a layer containing various antistatic agents such as sulfonate group-modified polystyrene.
However, since an anionic surfactant such as a long-chain alkyl compound having a sulfonate group has a relatively low molecular weight, a part of the antistatic agent moves through the antistatic coating film to form a base film. There is a problem of accumulating at the interface and transferring to the opposite surface of the base film, and a problem that the antistatic property decreases with time.
In addition, since the polymer having nitrogen element ionized in the main chain, sulfonate group-modified polystyrene, and the like have a relatively high molecular weight, the above-described problems do not occur. However, in order to obtain good antistatic performance, it is necessary to add a large amount of antistatic agent, and it is not economical because it is necessary to increase the thickness of the antistatic layer. Furthermore, when scrap film that has not been turned into a product (for example, film edges cut and removed in the manufacturing process) is collected and used as a recycled material for film production, it is included in the recycled material during melt film formation. There arises a problem that the antistatic agent component is thermally deteriorated, and the film to be regenerated is extremely colored and lacks practicality (recoverability is poor). In addition, there are disadvantages that the films are difficult to peel (block) and the coating film is easily scraped, and the solution is desired.

The method (3) is a method of imparting antistatic performance to the peeling interface where static electricity is generated, and a method of forming a pressure sensitive adhesive using a resin having antistatic performance, and a pressure sensitive adhesive containing an antistatic agent-containing pressure sensitive adhesive. There is a method of forming a layer (Patent Document 1: JP-A-1-253482).
In the former case, the antistatic performance of the resin itself, which can be paraphrased as electrical conductivity, is insufficient.
In the latter case, examples of the antistatic agent used include various surfactants and conductive powders such as carbon black. However, when a surfactant-containing pressure-sensitive adhesive is used, the surfactant generally tends to be concentrated on the surface of the pressure-sensitive adhesive layer, i.e., the bonding interface with the adherend, and the pressure-sensitive adhesive performance is low due to the surfactant. Very sensitive. That is, when moisture reduces the cohesive force of the pressure-sensitive adhesive layer and peels off the surface protective pressure-sensitive adhesive film, a part of the pressure-sensitive adhesive layer tends to remain on the adherend (so-called “glue residue”). On the other hand, when a conductive pressure-sensitive adhesive containing conductive powder such as carbon black is used, there arises a problem that transparency of the pressure-sensitive adhesive layer and the surface protective pressure-sensitive adhesive film is lowered or the film is colored.

The use of an antistatic agent that is excellent in transparency and hardly causes coloring problems is disclosed in Japanese Patent No. 2718519.
However, the invention described in Patent Document 2 is for an electrode pad that is applied to a living body although it relates to a conductive adhesive, and the conductive adhesive described in Patent Document 2 is used for a surface protective adhesive film. Was not at all usable.

JP-A-1-253482 Japanese Patent No. 2718519

  The object of the present invention is to provide excellent transparency and little coloration suitable as a pressure-sensitive adhesive for surface protective adhesive films of optical members such as various displays and polarizing plates. An object is to provide a pressure-sensitive adhesive.

  As a result of intensive studies, the present inventor has appropriate conductivity by adding an ionic compound (B) and a curing agent (C) to the acrylic copolymer (A) having a hydroxyl group and an alkylene oxide chain in the side chain. The present invention was completed by finding that an antistatic pressure-sensitive adhesive can be obtained.

That is, the antistatic acrylic pressure-sensitive adhesive of the present invention is an acrylic copolymer (A) having a hydroxyl group and an ethylene oxide chain in the side chain (except for those having a carboxyl group), lithium, iron, copper, sodium, An ionic compound (B) containing one cation selected from the group consisting of potassium and quaternary ammonium, and a curing agent (C) which is a trifunctional isocyanate compound,
The acrylic copolymer (A) is a solution polymerized monomer containing 1 to 30% by weight of a monomer having a hydroxyl group, 1 to 60% by weight of an acrylic monomer having an ethylene oxide chain and 2-ethylhexyl (meth) acrylate. Become
The dry film has a surface resistance value of 9 × 10 ⁹ Ω / □ or less.

  According to the present invention, an antistatic pressure-sensitive adhesive having an appropriate surface resistance value and excellent in transparency and removability can be obtained.

: An antistatic pressure-sensitive adhesive film in which an antistatic acrylic pressure-sensitive adhesive layer is laminated on the polarizing plate side of the PET film. : An antistatic pressure-sensitive adhesive film in which an antistatic acrylic pressure-sensitive adhesive layer is laminated on both sides of the polarizing plate side and the opposite side of the PET film. : An antistatic pressure-sensitive adhesive film in which an antistatic coating agent layer and further an antistatic acrylic pressure-sensitive adhesive layer are laminated on the polarizing plate side of the PET film. An antistatic pressure-sensitive adhesive film in which an antistatic acrylic pressure-sensitive adhesive layer is laminated on the polarizing plate side of the PET film and an antistatic coating agent layer is laminated on the opposite side.

  The acrylic copolymer (A) used in the present invention has a hydroxyl group and an alkylene oxide chain, and if necessary, an acrylic monomer having a hydroxyl group and an acrylic monomer having an alkylene oxide chain. It can be synthesized from other acrylic monomers that can be copolymerized.

  Examples of the acrylic monomer having a hydroxyl group used in the present invention include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate and the like. Can be mentioned. In the present invention, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable.

  In the present invention, the purpose of using the acrylic monomer having a hydroxyl group is to ensure the removability while ensuring the adhesive force to the adherend. More specifically, a cross-linked structure is formed by utilizing the reaction between a curing agent (C) such as an isocyanate curing agent described later used in forming the pressure-sensitive adhesive layer and these hydroxyl groups, and as described later. By controlling the molecular weight of the acrylic copolymer (A), it is possible to balance the adhesive strength and the removability.

  Therefore, when the acrylic copolymer (A) and the acrylic copolymer (D) having no alkylene oxide chain, which will be described later, are used in combination, the total monomer used for the copolymerization is 100% by weight. It is preferable that the acrylic monomer which has 1-30 weight%. More preferably, it is 3 to 10% by weight. If the acrylic monomer having a hydroxyl group is less than 1% by weight, the degree of cross-linking and cohesion as the pressure-sensitive adhesive layer are insufficient, and the pressure-sensitive adhesive force becomes excessively large or adhesive residue is liable to occur. If it exceeds 30% by weight, the degree of crosslinking becomes too high and the tackiness becomes poor.

  Examples of the acrylic monomer having an alkylene oxide chain used in the present invention include a monomer having an ethylene oxide chain, a monomer having a propylene oxide chain, and a monomer having both.

Examples of the monomer having an ethylene oxide chain include methoxypolyethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate.
Examples of the monomer having a propylene oxide chain include methoxypolypropylene glycol (meth) acrylate and polypropylene glycol (meth) acrylate.
In the present invention, a monomer having an ethylene oxide chain is preferable in consideration of compatibility with an ionic compound described later, and methoxypolyethylene glycol (meth) acrylate is particularly preferable.

  The purpose of using the acrylic monomer having an alkylene oxide chain in the present invention is to form a complex with the ionic compound (B) and the alkylene oxide to develop conductivity. Therefore, the role of the alkylene oxide chain is very large and not only provides a field for complex formation, but also serves as a transfer medium for the ionic compound (B). In other words, the conductivity in the present invention varies greatly depending on the amount of the ionic compound (B) and the content of the monomer having an alkylene oxide chain.

  Therefore, when the acrylic copolymer (A) and the acrylic copolymer (D) having no alkylene oxide chain described later are used in combination, the total monomer used for copolymerization is 100% by weight. The acrylic monomer having an oxide chain is preferably 1 to 60% by weight. More preferably, it is 5 to 50% by weight.

    Examples of the monomer that can be copolymerized with the acrylic monomer used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, 2 -Ethylhexyl (meth) acrylate, heptyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (Meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate Nonadecyl (meth) acrylate, eicosyl (meth) acrylate, heneicosyl (meth) acrylate and docosyl (meth) acrylate. In the present invention, it is preferable to use an acrylic monomer having 4 to 12 carbon atoms for copolymerization from the viewpoint of securing adhesive properties. More preferred are butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.

  The weight average molecular weight (Mw) of the acrylic copolymer (A) obtained by copolymerizing the above acrylic monomer having a hydroxyl group, an acrylic monomer having an alkylene oxide chain, and other monomers is 50,000 to 1,000,000. Preferably, it is a low molecular weight acrylic copolymer (A1) having a molecular weight of 50,000 to 200,000.

As described in the background art section, the adhesive for the protective film for optical members is required to have an antistatic function, removability and transparency. Therefore, from the viewpoint of the antistatic function, it is preferable that the acrylic copolymer (A) contains more alkylene oxide chains.
By the way, some optical members are very thin and fragile, while others are relatively strong. Depending on the type of adherend to which the protective film is attached, the protective film and adhesive are required. The magnitude of the peel force applied is different.
That is, when the fragile optical member is used as an adherend, the peeling force is preferably 200 g / 25 mm or less so as not to damage the adherend when the protective film is peeled off after sticking. More preferably, it is 100 g / 25 mm or less.
On the other hand, when a relatively strong optical member is used as the adherend, the peeling force can be allowed to be about 1000 g / 25 mm.
It should be noted that it is always required that the pressure-sensitive adhesive does not remain on the adherend when it is peeled regardless of the adherend.

  The peel strength of the pressure sensitive adhesive is greatly influenced by the cohesive strength of the main component itself constituting the pressure sensitive adhesive and the state of crosslinking between the main component and the curing agent (C) described later. In general, the peeling force can be reduced by using a large amount of the curing agent (C) with respect to the main component. In general, the cohesive force of the main component itself can be increased by increasing the molecular weight of the main component.

In the pressure-sensitive adhesive of the present invention, when a low peeling force of 200 g / 25 mm or less at the time of peeling is required, the curing agent (C) is added to 100 parts by weight of the main component, that is, the acrylic copolymer (A). It is preferable to use 10 to 40 parts by weight, more preferably 12.5 to 37.5 parts by weight, and still more preferably 15 to 30 parts by weight. In addition, it is preferable that there are many hardening | curing agents (C) from a viewpoint of low peeling force expression. However, if it is too much, crosslinking will be excessive, and it will not be able to peel off smoothly, but will peel off with squeaking.
The acrylic monomer having an alkylene oxide chain used in the present invention can generally be easily copolymerized with other acrylic monomers, but has a large chain transfer effect. Therefore, if the content of the alkylene oxide chain is increased from the viewpoint of improving conductivity, the molecular weight of the resulting acrylic copolymer (A) tends to decrease, and if the molecular weight decreases, the acrylic copolymer (A) itself The cohesive force tends to decrease, and the pressure-sensitive adhesive tends to remain on the adherend during peeling.
However, when a relatively large amount of the curing agent (C) is used with respect to the acrylic copolymer (A) in order to secure a low peeling force, a densely crosslinked pressure-sensitive adhesive layer can be obtained. Therefore, even if a relatively low molecular weight acrylic copolymer (A1) is used, the adhesive does not remain on the adherend during peeling.
Therefore, when the low resistance and the low peeling force as described above are required, the acrylic copolymer (A) has an Mw obtained by copolymerizing more acrylic monomers having an alkylene oxide chain of 50,000. It is one of the preferred embodiments to use ˜200,000 low molecular weight acrylic copolymer (A1).

In the present invention, a high molecular weight acrylic copolymer (A2) having an Mw of 200,000 to 1,000,000 can also be used as the acrylic copolymer (A). By copolymerizing while controlling the chain transfer effect of the acrylic monomer having an alkylene oxide chain, it is possible to obtain an acrylic copolymer (A2) having a relatively high molecular weight and excellent conductivity.
For example, it can be obtained by using a plurality of polymerization steps (multistage polymerization reaction), reducing the amount of the initiator, or controlling the monomer concentration. More specifically, an acrylic monomer having an alkylene oxide chain is used after the polymerization is advanced to a certain degree of high molecular weight with little or no use of an acrylic monomer having an alkylene oxide chain for copolymerization at the initial stage of the polymerization. It can be obtained by subjecting all or most of the monomers to polymerization. When such a so-called two-stage polymerization method is used, a polymerization initiator can be further used when the main amount of the acrylic monomer having an alkylene oxide chain is polymerized.

  The high molecular weight acrylic copolymer (A2) has a higher cohesive strength than the low molecular weight acrylic copolymer (A1). Therefore, even when the amount of the curing agent (C) is reduced, the high molecular weight acrylic copolymer (A2) No adhesive residue is likely to occur. However, when fine adhesion such as a peel strength of 100 g / 25 mm or less, preferably 50 g / 25 mm or less is required, it is preferable to form a dense cross-linked structure in the adhesive. Accordingly, the curing agent (C) is used in an amount of about 10 to 40 parts by weight with respect to 100 parts by weight of the high molecular weight acrylic copolymer (A2) as in the case of the low molecular weight acrylic copolymer (A1). preferable.

Furthermore, in the present invention, an acrylic copolymer (D) having no alkylene oxide chain can be used in combination, and a high molecular weight acrylic copolymer having no alkylene oxide chain having an Mw of 200,000 to 1,000,000. It is also one aspect of the present invention to use (D1) in combination with a low molecular weight acrylic copolymer (A1) having an alkylene oxide chain having an Mw of 50,000 to 200,000.
When the high molecular weight acrylic copolymer (D1) is used in combination, the low molecular weight acrylic copolymer (A1) / high molecular weight acrylic copolymer (D1) = 5 to 80/20 to 95 (weight ratio). It is preferably 10 to 60/40 to 90 (weight ratio).
As described above, the low molecular weight acrylic copolymer (A1) is excellent in conductivity in many cases, but uses a large amount of the curing agent (C) from the viewpoint of suppressing or preventing adhesive residue because of its small cohesive force. There is a need to. By using the high molecular weight acrylic copolymer (D1) in combination with such a low molecular weight acrylic copolymer (A1), the amount of the curing agent (C) used can be reduced. For example, 1 to 8 parts by weight of the curing agent (C) can be used with respect to a total of 100 parts by weight of the low molecular weight acrylic copolymer (A1) and the high molecular weight acrylic copolymer (D1). Part by weight can be used. In the case where a peeling force of up to about 1000 g / 25 mm can be tolerated at the time of peeling, various levels can be obtained by reducing the curing agent (C) while using the high molecular weight acrylic copolymer (D1) in this way. It is possible to meet the demand for antistatic property and removability.
Further, when 10 to 40 parts by weight of the curing agent (C) is used with respect to 100 parts by weight of the total of the low molecular weight acrylic copolymer (A1) and the high molecular weight acrylic copolymer (D1), the adhesive with low peeling force is used. An agent can also be obtained.

  The high molecular weight acrylic copolymer (D) having no alkylene oxide chain used in the present invention is obtained in the same manner as the acrylic copolymer (A) except that an acrylic monomer having an alkylene oxide chain is not subjected to polymerization. be able to.

  In the present invention, the acrylic copolymer (A) and the high molecular weight acrylic copolymer (D) are obtained in advance, and both may be mixed, or the high molecular weight acrylic copolymer (D And the monomer for the acrylic copolymer (A) may be polymerized in the presence of the high molecular weight acrylic copolymer (D). The latter method is somewhat similar to the multistage polymerization method for obtaining the acrylic copolymer (A) described above. The difference between the two is that in the multistage polymerization method for obtaining the acrylic copolymer (A), the alkylene oxide is used in the second and subsequent polymerizations in which the main amount of the acrylic monomer having an alkylene oxide chain is polymerized. Where only the acrylic monomer having a chain is subjected to polymerization, whereas the monomer for the acrylic copolymer (A) is polymerized in the presence of the high molecular weight acrylic copolymer (D), the second and subsequent stages are polymerized. In the polymerization, an acrylic monomer having an alkylene oxide chain and other monomers are used for the polymerization.

Examples of the ionic compound (B) used in the present invention include sodium chloride, potassium chloride, lithium chloride, lithium perchlorate, ammonium chloride, potassium chlorate, aluminum chloride, copper chloride, ferrous chloride, ferric chloride, ammonium sulfate. , Inorganic salts such as potassium nitrate, sodium nitrate, sodium carbonate, sodium thiocyanate,
Organic salts such as sodium acetate, sodium alginate, sodium lignin sulfonate, and sodium toluene sulfonate are listed.
These can be used alone or in combination. From the viewpoints of conductivity and safety, sodium chloride, potassium chloride, lithium perchlorate and the like are preferable.

  Moreover, the content is 100 parts by weight of the acrylic copolymer (A), or in the case where the acrylic copolymer (D) is used in combination, the total of 100 parts by weight of both copolymers, It is preferable that it is 0.1-50 weight part. More preferably, it is 1-30 weight part. If it is less than 0.1 parts by weight, sufficient ionic conductivity cannot be obtained, and even if it contains more than 50 parts by weight of the ionic compound (B), the effect of improving the conductivity can hardly be expected. And, since the whitening of the coating film tends to occur due to a decrease in compatibility with the resin, it is not preferable.

The stability over time of the pressure-sensitive adhesive film using an antistatic acrylic pressure-sensitive adhesive, that is, the protective film for optical members, includes the amount of the ionic compound (B) contained and the amount of alkylene oxide chain contained in the acrylic copolymer (A). The amount is greatly affected.
When the amount of the alkylene oxide chain is large, a complex can be formed efficiently with the ionic compound (B), but when the amount of the alkylene oxide chain is small and the amount of the ionic compound is large, an excess that cannot form a complex is formed. The ionic compound moves to the surface of the pressure-sensitive adhesive layer, and the whitening phenomenon as described above tends to occur. In addition, the surface resistance value with time tends to increase.
From these viewpoints, it is preferable to increase the amount of alkylene oxide chains contained in the pressure-sensitive adhesive layer as much as possible and to add the minimum ionic compound (B) capable of expressing the required conductivity.

In the antistatic acrylic pressure-sensitive adhesive of the present invention, a curing agent (C) can be suitably used in order to increase the cohesive strength and the degree of crosslinking.
The curing agent (C) of the present invention preferably has two or more functional groups that can react with functional groups such as hydroxyl groups contained in the acrylic copolymers (A) and (D). Those are preferred. For example, a known trifunctional isocyanate compound or a known polyfunctional epoxy compound can be suitably used. These can also be used in combination.

  The known trifunctional isocyanate compound includes a so-called adduct obtained by modifying a known diisocyanate compound with a trifunctional polyol component, a burette obtained by reacting the diisocyanate compound with water, and a 3 amount having an isocyanurate ring formed from three molecules of the diisocyanate compound. The body (isocyanurate body) can be used.

  Known diisocyanate compounds include aromatic diisocyanates, aliphatic diisocyanates, araliphatic diisocyanates, alicyclic diisocyanates, and the like.

  As aromatic diisocyanates, 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate Examples thereof include isocyanate, 4,4′-toluidine diisocyanate, dianisidine diisocyanate, and 4,4′-diphenyl ether diisocyanate.

  Aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4 , 4-trimethylhexamethylene diisocyanate and the like.

  Examples of the araliphatic diisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, 1, Examples include 4-tetramethylxylylene diisocyanate and 1,3-tetramethylxylylene diisocyanate.

  Examples of alicyclic diisocyanates include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4- Examples include cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanate methyl) cyclohexane, 1,4-bis (isocyanate methyl) cyclohexane, and the like. .

  As the diisocyanate compound used in the present invention, it is preferable to use 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate).

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

About the above-mentioned hardening | curing agent (C), a trifunctional isocyanate compound and a polyfunctional epoxy compound can be used individually and in combination, respectively. When used in applications that place importance on flexibility, it is preferable to use a trifunctional isocyanate compound. When heat resistance is required, it is preferable to use a polyfunctional epoxy compound.
As described above, when a low peeling force of 200 g / 25 mm or less, preferably 100 g / 25 mm or less is required, the curing agent (C) is used in an amount of 10 to 40 weights per 100 parts by weight of the acrylic copolymer (A). Part is preferably used, more preferably 12.5 to 37.5 parts by weight, and still more preferably 15 to 30 parts by weight.
Moreover, when using a polyfunctional epoxy compound, in order to act as a crosslinking agent more effectively, it is preferable that acrylic acid or methacrylic acid is contained in the acrylic copolymer (A). About the content, it is preferable that it is 0.5 to 5% by weight ratio in all the acrylic monomers. If it is less than 0.5%, it does not sufficiently act as a crosslinking agent, and if it exceeds 5%, the pot life after addition of the curing agent (C) tends to be short, such being undesirable.

  If necessary, the antistatic pressure-sensitive adhesive of the present invention may be used in combination with other resins such as acrylic resins, polyester resins, amino resins, epoxy resins, and polyurethane resins. Depending on the application, additives such as tackifiers, talc, calcium carbonate, titanium oxide, etc., colorants, ultraviolet absorbers, antioxidants, antifoaming agents, light stabilizers, etc. may be blended. good.

By using the antistatic pressure-sensitive adhesive of the present invention, it is possible to obtain a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive and a substrate such as a plastic film, paper, cloth, and foam are laminated. The surface of the agent layer can be covered with a release sheet.
The pressure-sensitive adhesive sheet can be obtained by applying or impregnating a pressure-sensitive adhesive to various substrates, and drying and curing it. Alternatively, a pressure-sensitive adhesive is applied on the release sheet, dried, and various substrates are laminated on the surface of the pressure-sensitive adhesive layer that is being formed, and a hydroxyl group in the pressure-sensitive adhesive and an isocyanate group in the curing agent (C), or It can also be obtained by advancing the reaction between the carboxyl group in the pressure-sensitive adhesive and the epoxy group in the curing agent (C).

  By applying the pressure-sensitive adhesive of the present invention to a transparent plastic film among the substrates, a surface protective pressure-sensitive adhesive film for an optical member can be suitably obtained.

  Examples of the plastic film include polyvinyl chloride film, polyethylene film, polyethylene terephthalate (PET) film, polyurethane film, nylon film, treated polyolefin film, untreated polyolefin film, and the like.

The antistatic pressure-sensitive adhesive of the present invention is preferably applied to a substrate so as to have a thickness of about 2 to 200 μm when dried and cured. If it is less than 2 μm, the ionic conductivity becomes poor, and if it exceeds 200 μm, the production and handling of the pressure-sensitive adhesive sheet becomes difficult.
In this manner, an antistatic pressure-sensitive adhesive film having a surface resistance value of the pressure-sensitive adhesive layer of 10 ¹¹ Ω / □ or less can be obtained.

The antistatic pressure-sensitive adhesive film of various aspects can be obtained using the antistatic pressure-sensitive adhesive of the present invention in consideration of its use, required performance, and the like.
For example, an antistatic pressure-sensitive adhesive film for a protective film for a polarizing plate will be described with reference to the drawings.
FIG. 1 shows an antistatic acrylic adhesive layer on the polarizing plate side of a PET film.
FIG. 2 shows an antistatic acrylic pressure-sensitive adhesive layer on both the polarizing plate side and the opposite side of the PET film.
FIG. 3 shows an antistatic coating agent layer and further an antistatic acrylic adhesive layer on the polarizing plate side of the PET film.
FIG. 4 shows an embodiment in which an antistatic acrylic pressure-sensitive adhesive layer is located on the polarizing plate side of the PET film and an antistatic coating agent layer is located on the opposite side.
When the pressure-sensitive adhesive of the present invention is used for a film for protecting the surface of an optical member or an electronic member, it is possible to take a form as shown in FIGS. 3 and 4 in order to further reduce the peel charge amount.
Moreover, in the use which gives functionality to a plastic film, it takes the form as shown in FIG. 2 and the functional film can be further bonded.
In consideration of workability and production cost, the case of FIG. 1 is most preferable.

  Used when an antistatic coating layer having no adhesiveness is provided between the adhesive layer and the plastic film or on the opposite side (top coat) of the plastic film that is not the adhesive layer side as shown in FIGS. Examples of the antistatic agent that can be used include metal fillers, quaternary ammonium salt derivatives, surfactants, and conductive resins.

  Examples of the metal filler include metal oxides such as tin oxide, zinc oxide, iron oxide and antimony oxide, and metals such as carbon, silver and copper. In consideration of the transparency of the coating film, tin oxide, antimony oxide and the like are preferable.

  As the quaternary ammonium salt derivative, a polymer of a (meth) acrylate monomer having a quaternary ammonium salt or a copolymer with another (meth) acrylate monomer can be used.

  The antistatic coating agent layer preferably has a thickness of 0.1 μm to 50 μm as a coating film, more preferably 1 μm to 20 μm. If it is 0.1 μm or less, the antistatic performance cannot be sufficiently exhibited, and if it is 50 μm or more, there are problems in cost, coatability and the like.

Synthesis example 1
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used, and the reaction kettle was 46% by weight of 2EHA, 50% by weight of BA, 50% by weight of 2HEA, and AM90G Total amount, ethyl acetate as solvent, azobisisobutyronitrile as initiator is charged in appropriate amount,
A solution prepared by adding appropriate amounts of the remaining monomer, ethyl acetate, and azobisisobutyronitrile was added dropwise over about 1 hour and polymerized at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate. This reaction solution had a solid content of 40%, a viscosity of 1300 cps, and Mw (weight average molecular weight) of 310,000.

Synthesis example 2
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a 4-neck flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used. The reaction kettle was 44% by weight of 2EHA, 2% by weight of HEA, the total amount of M40G, and ethyl acetate as a solvent. , Charge an appropriate amount of azobisisobutyronitrile as an initiator,
A solution prepared by adding appropriate amounts of the remaining monomer, ethyl acetate, and azobisisobutyronitrile was added dropwise over about 1 hour and polymerized at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate. This reaction solution had a solid content of 41%, a viscosity of 1200 cps, and a Mw (weight average molecular weight) of 350,000.

Synthesis example 3
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a 4-neck flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used. The reaction kettle was 35% by weight of 2EHA, 30% by weight of BA, 30% by weight of 2HEA, A suitable amount of ethyl acetate and azobisisobutyronitrile as an initiator is charged.
Next, an appropriate amount of 42% by weight of 2EHA, 40% by weight of BA, 40% by weight of 2HEA, 30% by weight of M90G, ethyl acetate, and azobisisobutyronitrile was added and mixed for about 1 hour. The solution was added dropwise and polymerized at about 80 ° C. for 1 hour in a nitrogen atmosphere.
Thereafter, a solution prepared by adding an appropriate amount of tolyl to the remaining monomers, ethyl acetate and azobisisobutyro was added dropwise over about 1 hour, and polymerization was performed at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate and toluene. This reaction solution had a solid content of 40%, a viscosity of 1500 cps, and Mw (weight average molecular weight) of 330,000.

Synthesis example 4
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used. The reaction kettle was 40% by weight of 2EHA, 30% by weight of BA, 30% by weight of 2HEA, A suitable amount of ethyl acetate and azobisisobutyronitrile as an initiator is charged.
Next, an appropriate amount of 46% by weight of 2EHA, 40% by weight of BA, 40% by weight of 2HEA, 20% by weight of M90G, ethyl acetate and azobisisobutyronitrile was added and mixed for about 1 hour. The solution was added dropwise and polymerized at about 80 ° C. for 1 hour in a nitrogen atmosphere.
Thereafter, a solution prepared by adding an appropriate amount of tolyl to the remaining monomers, ethyl acetate and azobisisobutyro was added dropwise over about 1 hour, and polymerization was performed at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate and toluene. This reaction solution had a solid content of 40%, a viscosity of 3700 cps, and Mw (weight average molecular weight) of 250,000.

Synthesis example 5
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a 4-neck flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer and a dropping funnel was used. The reaction kettle was 74% by weight of 2EHA, 50% by weight of 2HEA, ethyl acetate as a solvent, and as an initiator. An appropriate amount of azobisisobutyronitrile is charged,
A solution prepared by adding appropriate amounts of the remaining monomers, ethyl acetate, toluene, and azobisisobutyronitrile was added dropwise over about 1 hour and polymerized at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with toluene. This reaction solution had a solid content of 41%, a viscosity of 1000 cps, and Mw (weight average molecular weight) of 110,000.

Synthesis Example 6
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a 4-neck flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used, and the reaction kettle was 44% by weight of 2EHA, 50% by weight of BA, 50% by weight of 2HEA, 50% by weight, total amount of M40G, ethyl acetate as solvent, azobisisobutyronitrile as initiator,
A solution prepared by adding appropriate amounts of the remaining monomer, ethyl acetate, and azobisisobutyronitrile was added dropwise over about 1 hour and polymerized at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate. This reaction solution had a solid content of 40%, a viscosity of 2000 cps, and Mw (weight average molecular weight) of 320,000.

Synthesis example 7
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a 4-neck flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used. The reaction kettle was 88% by weight of 2EHA, 50% by weight of 2HEA, ethyl acetate as a solvent, and as an initiator. An appropriate amount of azobisisobutyronitrile is charged,
A solution prepared by adding appropriate amounts of the remaining monomers, ethyl acetate, toluene, and azobisisobutyronitrile was added dropwise over about 1 hour and polymerized at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with toluene. This reaction solution had a solid content of 40%, a viscosity of 400 cps, and a Mw (weight average molecular weight) of 105,000.

Synthesis Example 8
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used. The reaction kettle was 50% by weight of 2EHA, 50% by weight of BA, 50% by weight of 2HEA, A suitable amount of ethyl acetate and azobisisobutyronitrile as an initiator is charged.
A solution prepared by adding appropriate amounts of the remaining monomer, ethyl acetate, and azobisisobutyronitrile was added dropwise over about 1 hour and polymerized at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate. This reaction solution had a solid content of 41%, a viscosity of 1700 cps, and Mw (weight average molecular weight) 400,000.

Synthesis Example 9
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, a 4-neck flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel was used. An appropriate amount of azobisisobutyronitrile is charged,
Next, a solution prepared by adding appropriate amounts of 42% by weight of 2EHA, 40% by weight of BA, 30% by weight of M90G, ethyl acetate and azobisisobutyronitrile was added dropwise over about 1 hour, Polymerization was carried out at about 80 ° C. for 1 hour.
Thereafter, a solution prepared by adding an appropriate amount of tolyl to the remaining monomers, ethyl acetate and azobisisobutyro was added dropwise over about 1 hour, and polymerization was performed at about 80 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate and toluene. This reaction solution had a solid content of 40%, a viscosity of 1300 cps, and a Mw (weight average molecular weight) of 350,000.

Synthesis Example 10
A copolymer composed of monomers having the composition ratio shown in Table 1 was obtained in the following manner.
That is, using a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, the reactor was charged with all the monomers, benzene as the solvent, and azobisisobutyronitrile as the initiator. Then, polymerization was carried out at about 80 ° C. for 5 hours under a nitrogen atmosphere to obtain a reaction solution having a solid content of 40%.

[Example 1]
To 40 g of the solid content of the acrylic resin solution obtained in Synthesis Example 1, 3 g of lithium perchlorate and 10 g of tolylene diisocyanate trimethylolpropane adduct 37% ethyl acetate solution as a curing agent were blended to obtain an adhesive.
The obtained pressure-sensitive adhesive was coated on a release paper so as to have a dry coating film thickness of 25 μm, dried at 100 ° C. for 2 minutes, and then a polyethylene terephthalate film (thickness 50 μm) was laminated on the pressure-sensitive adhesive layer being formed. In the state, it was allowed to pass at room temperature for 2 days to obtain a test adhesive tape.
Using the pressure-sensitive adhesive tape, the adhesive strength, surface resistance value, removability, and transparency were evaluated according to the following methods.

<Adhesive strength>
The release paper of the pressure-sensitive adhesive tape for test was peeled off, and the exposed pressure-sensitive adhesive layer was attached to a glass plate having a thickness of 0.4 mm at 23 ° C.-65% RH and roll-bonded according to JIS. After 24 hours, the peel strength (180 degree peel, pulling speed 300 mm / min; unit g / 25 mm width) was measured with a shopper type peel tester.

<Surface resistance value>
The release paper of the pressure-sensitive adhesive tape for test was peeled off, and the exposed pressure-sensitive adhesive layer surface was measured using a surface resistance measuring device (manufactured by Mitsubishi Chemical Corporation) (Ω / □).

<Removability>
After peeling off the release paper of the test adhesive tape and sticking the exposed adhesive layer to the glass plate, it was left under the condition of 60 ° C.-95% RH, cooled to 23 ° C.-65% RH, and then peeled off. The adhesive residue was visually evaluated. After peeling
No adhesive transfer to the adherend ◎
Very few ○
Partially △
Fully migrated ×
As evaluated.

<Transparency>
After peeling the release paper of the test adhesive tape and sticking the exposed adhesive layer to a glass plate, it was left under the condition of 60 ° C.-95% RH, cooled to 23 ° C.-65% RH, and then visually. evaluated.
Colorless and transparent ◎
Very slightly cloudy ○
Those that are cloudy or aggregated △
Not transparent ×

[Examples 2, 3, and 5] [Comparative Example 3]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that each acrylic resin obtained in Synthesis Examples 2, 3, 5, and 9 was used and 5 g of lithium perchlorate was used, and evaluation was performed in the same manner as in Example 1.

[Reference Example 1]
Using the acrylic resin obtained in Synthesis Example 4 and using 3 g of lithium chloride, a pressure-sensitive adhesive was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

[Reference Example 2]
Adhesive as in Example 1 except that the acrylic resin obtained in Synthesis Example 6 was used and 3 g of a 5% toluene solution of N, N, N′N′-tetraglycidyl-m-xylenediamine was used as a curing agent. And evaluated in the same manner as in Example 1.

[Example 7]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 50 g of the acrylic resin solution obtained in Synthesis Example 5 and 50 g of the acrylic resin solution obtained in Synthesis Example 8 were mixed and 5 g of lithium perchlorate was used. Evaluation was performed in the same manner as in Example 1.

[Example 8]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 1 g of lithium perchlorate was used using the acrylic resin obtained in Synthesis Example 7, and evaluation was performed in the same manner as in Example 1.

[Example 9]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 3 g of lithium perchlorate was used, using the acrylic resin obtained in Synthesis Example 7, and evaluated in the same manner as in Example 1.

[Examples 10 and 11]
Evaluation was performed in the same manner as in Example 1 except that the acrylic resin obtained in Synthesis Examples 5 and 7 was used, 1 g of lithium perchlorate was used, and the test adhesive tape was obtained after 7 days at room temperature.

[Comparative Examples 1 and 4]
Using each acrylic resin obtained in Synthesis Examples 8 and 3, a pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that lithium perchlorate was not used, and evaluation was performed in the same manner as in Example 1.

[Comparative Example 2]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the acrylic resin obtained in Synthesis Example 8 was used, and evaluated in the same manner as in Example 1.

[Comparative Example 5]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the acrylic resin obtained in Synthesis Example 2 was used, 5 g of lithium perchlorate was used, and no curing agent was used, and evaluation was performed in the same manner as in Example 1.

[Comparative Example 6]
The acrylic resin solution obtained in Synthesis Example 10 was desolvated and then dissolved in acetylacetone, and 3% by weight of lithium perchlorate was added to the acrylic resin solid content and dissolved. This uniform viscous liquid was cast on an aluminum foil and dried at 80 ° C. for about 2 days to completely evaporate acetone. The obtained resin sheet was laminated on a polyethylene terephthalate film (thickness 50 μ) and evaluated in the same manner as in Example 1.

As described above, it can be seen that the antistatic pressure-sensitive adhesive of the present invention is excellent in surface resistance (conductivity), transparency and removability.
On the other hand, since the adhesive shown in Comparative Examples 1 and 4 does not contain an ionic compound, it has good removability and transparency, but has no conductivity. Since the pressure-sensitive adhesive shown in Comparative Example 2 does not have an alkylene oxide chain, the ionic compound does not dissolve and aggregates, resulting in poor transparency and surface resistance. Since the pressure-sensitive adhesive shown in Comparative Example 3 did not contain a hydroxyl group-containing monomer, the crosslinking effect by the curing agent was not obtained, and the removability was poor. Since the pressure-sensitive adhesive shown in Comparative Example 5 did not use a curing agent at all, the cohesive force was insufficient and the removability was poor.
In Comparative Example 6, after the acrylic copolymer (A) was obtained in advance as in the present invention, the acrylic copolymer (A) was further crosslinked with a curing agent between the release paper and the polyethylene terephthalate film. The adhesive layer is not formed, but an acrylic resin is simply laminated on the polyethylene terephthalate film, and no curing agent is used, so the cohesive force as an adhesive is insufficient and the removability is poor. .

1: Plastic film substrate (PET)
2: Antistatic acrylic adhesive layer 3: Polarizing plate 4: Antistatic coating agent layer

Claims (5)

Acrylic copolymer (A) having a hydroxyl group and an ethylene oxide chain in the side chain (excluding those having a carboxyl group), selected from the group consisting of lithium, iron, copper, sodium, potassium and quaternary ammonium Containing an ionic compound (B) containing one kind of cation and a curing agent (C) which is a trifunctional isocyanate compound;
The acrylic copolymer (A) is a solution polymerized monomer containing 1 to 30% by weight of a monomer having a hydroxyl group, 1 to 60% by weight of an acrylic monomer having an ethylene oxide chain and 2-ethylhexyl (meth) acrylate. Become
An antistatic acrylic pressure-sensitive adhesive characterized in that the dry film has a surface resistance value of 9 × 10 ⁹ Ω / □ or less. The antistatic acrylic pressure-sensitive adhesive according to claim 1, wherein the acrylic copolymer (A) has a weight average molecular weight of 50,000 to 1,000,000. The antistatic acrylic pressure-sensitive adhesive according to claim 1 or 2, wherein an adhesive strength at 180 ° peel to a glass plate in a 23 ° C-65% RH atmosphere and a pulling speed of 300 mm / min is 100 g / 25 mm or less.   The protective film characterized by laminating | stacking the antistatic acrylic adhesive of any one of Claims 1-3 on the at least single side | surface of a plastic base material. 5. The protective film according to claim 4, wherein the plastic substrate is an optical member.

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