WO2016163287A1 - Adhesive composition, adhesive obtained using same, and adhesive for polarizing plates - Google Patents

Abstract

As an adhesive composition having excellent aging characteristics, which is free from the occurrence of bleeding and adverse effect on durability even if the content of an antistatic agent is increased, and which is capable of stably exhibiting antistatic properties over a long period of time, the present invention provides an adhesive composition which contains (A) an acrylic resin and (B) an antistatic agent, and wherein: the acrylic resin (A) contains an amide group and a functional group other than an amide group; a structural unit derived from a monomer (a1) containing a functional group other than an amide group accounts for 1-10% by weight of the acrylic resin (A); the antistatic agent (B) is composed of an ammonium-based antistatic agent; and the content of the antistatic agent (B) is 1.2-15 parts by weight relative to 100 parts by weight of the acrylic resin (A).

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive using the same, and pressure-sensitive adhesive for polarizing plate

The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive using the same, and a pressure-sensitive adhesive for polarizing plates. More specifically, the present invention has a well-balanced antistatic property, durability and aging characteristics at room temperature and low temperature conditions. The present invention relates to a pressure-sensitive adhesive composition that forms an excellent pressure-sensitive adhesive, a pressure-sensitive adhesive using the same, and a pressure-sensitive adhesive for polarizing plates.

The liquid crystal display plate is usually obtained by attaching a polarizing plate to the surface of a liquid crystal cell in which an aligned liquid crystal component is sandwiched between two glass plates with an adhesive. Conventionally, a polarizing plate having a three-layer structure in which a polarizer made of a polyvinyl alcohol resin is sandwiched between protective films made of a triacetyl cellulose resin is used.

In recent years, as polarizing plates for liquid crystal display panels, a protective film that protects both sides of the polarizer (polyvinyl alcohol film) using a highly hydrophobic resin such as an acrylic resin or a cycloolefin resin has appeared. ing. However, a polarizing plate using these hydrophobic resins for the protective film is more easily charged than a polarizing plate using a conventional triacetyl cellulose-based film for the protective film, and thus rubs against the backlight of the liquid crystal display panel. Due to frictional charging caused by the liquid crystal display, display defects (so-called display unevenness, whitening phenomenon) may occur due to disorder of liquid crystal alignment, which is a problem.

Therefore, as a solution to the problem of frictional charging, an antistatic agent is added to the pressure-sensitive adhesive layer provided on the surface of the polarizing plate for adhesion (crimping) with the liquid crystal cell to prevent static charging. Attempts to improve performance have been proposed (see Patent Document 1).

JP 2009-79205 A

However, if the amount of the antistatic agent added to the pressure-sensitive adhesive composition used for adhesion of the polarizing plate as in Patent Document 1 is increased, under severe conditions such as high temperature and high humidity conditions, low temperature conditions, heat cycle tests, etc. Over time, the antistatic agent in the composition may bleed out from the pressure-sensitive adhesive layer, resulting in a decrease in durability (weather resistance) such as a decrease in antistatic performance and peeling of the polarizing plate. Moreover, in the adhesive for polarizing plates like patent document 1, since the lithium salt type antistatic agent was mainly used, aging took time.

Therefore, there is a demand for a pressure-sensitive adhesive composition that can maintain antistatic performance without bleeding out even when a large amount of antistatic agent is added, and has excellent aging characteristics.

The present invention has been made in view of such circumstances, and even if the content of the antistatic agent is increased, bleedout does not occur and the durability is not adversely affected. An object of the present invention is to provide a pressure-sensitive adhesive composition that can be stably exerted over a long period of time and has excellent aging characteristics, a pressure-sensitive adhesive using the same, and a pressure-sensitive adhesive for polarizing plates.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, in the pressure-sensitive adhesive composition containing the acrylic resin (A) and the antistatic agent (B), the antistatic agent (B ) And a specific amount of an ammonium-based antistatic agent, and the acrylic resin (A) contains two types of functional groups other than an amide group and an amide group with respect to the entire resin component. By increasing the content of the “functional group” [that is, the content of the structural unit derived from the monomer (a1) containing a functional group other than an amide group] more than the amount considered appropriate in the conventional technical common sense, Bleed does not occur even when the content of the antistatic agent is increased, and when used as a pressure-sensitive adhesive for polarizing plates, antistatic performance and durability can be maintained at a high level in a well-balanced manner, and ammonium salt-based antistatic Found that pressure-sensitive adhesive composition excellent in the aging characteristics can be obtained by using a specific amount, and have completed the present invention.

That is, the gist of the present invention is a pressure-sensitive adhesive composition containing an acrylic resin (A) and an antistatic agent (B), wherein the acrylic resin (A) has an amide group and a functional group other than the amide group. And the structural unit derived from the monomer (a1) containing a functional group other than an amide group accounts for 1 to 10% by weight of the acrylic resin (A), and the antistatic agent (B) A pressure-sensitive adhesive composition comprising an antistatic agent, wherein the content of the antistatic agent (B) is 1.2 to 15 parts by weight with respect to 100 parts by weight of the acrylic resin (A). It is.

Furthermore, the present invention relates to a pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition with a cross-linking agent (C), and a pressure-sensitive adhesive for a polarizing plate using the pressure-sensitive adhesive.

The pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive obtained by crosslinking the same are excellent in anti-static performance over time, and even when blending more anti-static agents than conventional products, no bleed out occurs. It has excellent antistatic performance and durability, and also has excellent aging characteristics because the gel fraction increases in a short time.

Furthermore, the above-mentioned pressure-sensitive adhesive composition and the pressure-sensitive adhesive obtained using the same are excellent not only in durability but also in light leakage resistance and reworkability.

The present invention is described in detail below.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acrylate means acrylate or methacrylate, and (meth) acrylamide means acrylamide or methacrylamide. The acrylic resin is a resin obtained by polymerizing a polymerization component containing at least one (meth) acrylate monomer. And the monomer in this invention is a compound which has a polymerizable unsaturated group, The said polymerizable unsaturated group is not contained in the functional group which a monomer has.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing an acrylic resin (A) and an antistatic agent (B), wherein the acrylic resin (A) is a functional group other than an amide group and an amide group. The antistatic agent (B) comprises an ammonium antistatic agent.

<Acrylic resin (A)>
The acrylic resin (A) constituting the pressure-sensitive adhesive composition of the present invention contains an amide group and a functional group other than an amide group, and is a structural unit derived from a monomer (a1) containing a functional group other than an amide group. The content is 1 to 10% by weight of the entire acrylic resin (A). The content of the structural unit derived from the monomer (a1) containing a functional group other than an amide group is preferably 1.5 to 8% by weight, more preferably 2 to 5% by weight, particularly preferably 2.5 to 4%. % By weight. If the content of the structural unit derived from the monomer (a1) containing a functional group other than an amide group is too large, a large amount of the functional group remains, so that there is a tendency for physical properties to change over time. Since the ratio of the polar component increases and the pressure-sensitive adhesive layer easily absorbs moisture, the durability tends to decrease, such as foaming by heating. If the content of the structural unit derived from the monomer (a1) containing a functional group other than an amide group is too small, the acrylic resin does not sufficiently react with the cross-linking agent in the cross-linking reaction, and sufficient cohesive force is produced as an adhesive. Therefore, durability tends to decrease.

Examples of the monomer (a1) containing a functional group other than the amide group include monomers having a functional group that reacts with a crosslinking agent (C) described later. Examples thereof include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and an acetoacetyl group. And a monomer containing an isocyanate group, a monomer containing an isocyanate group, and a monomer containing a glycidyl group. Among these, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferable in that a crosslinking reaction can be efficiently performed, and it is preferable to use a hydroxyl group-containing monomer and a carboxyl group-containing monomer in combination.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( Examples thereof include hydroxyalkyl esters of acrylic acid such as (meth) acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate.

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycolic acid, and cinnamic acid. Etc. Of these, (meth) acrylic acid is preferably used in terms of copolymerizability and durability.

Examples of the acetoacetyl group-containing monomer include 2- (acetoacetoxy) ethyl (meth) acrylate and allyl acetoacetate.

Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

As the glycidyl group-containing monomer, for example, glycidyl (meth) acrylate, allyl glycidyl (meth) acrylate, or the like can be used.

The functional group-containing monomer (a1) other than the amide group may be used alone or in combination of two or more.

In the present invention, it is preferable that the acrylic resin (A) has a carboxyl group as a functional group other than an amide group in that the gel fraction increases in a short time and the aging property is improved. It is preferable to contain 1 to 5% by weight of a structural unit derived from a carboxyl group-containing monomer as the monomer (a1) containing the above functional group. The content of the structural unit derived from the carboxyl group-containing monomer is more preferably 1.5 to 4% by weight, and particularly preferably 2 to 3.5% by weight. If the content of the structural unit derived from the carboxyl group-containing monomer of the acrylic resin (A) is too small, it is difficult to obtain a catalytic effect of the carboxyl group in the crosslinking reaction. There is a tendency that the reaction with the isocyanate-based crosslinking agent does not proceed sufficiently and aging tends to take a long time, and if the content is too high, functional groups having reactivity remain, and thus physical properties tend to change over time. Moreover, since the ratio of the polar component in the pressure-sensitive adhesive composition is increased, the pressure-sensitive adhesive layer tends to absorb moisture, and the durability tends to decrease, such as foaming by heating.

The acrylic resin (A) of the present invention contains an amide group, preferably contains 1 to 25% by weight of structural units derived from the amide group-containing monomer (a2), more preferably 2 to 10%. % By weight, particularly preferably 3 to 7% by weight. If the content of the structural unit derived from the amide group-containing monomer (a2) is too large, the proportion of the polar component of the acrylic resin increases, and the pressure-sensitive adhesive layer formed by crosslinking it easily absorbs moisture. If the amount is too small, sufficient cohesive force as an adhesive cannot be obtained, and durability after heating and humidification tends to decrease.

Examples of the amide group-containing monomer (a2) include amide group-containing (meth) acrylates. Examples of the amide group-containing (meth) acrylate include methoxymethyl (meth) acrylamide, ethoxymethyl (meth) acrylamide, propoxymethyl (meth) acrylamide, isopropoxymethyl (meth) acrylamide, and n-butoxymethyl (meth) acrylamide. , Alkoxyalkyl (meth) acrylamide monomers such as isobutoxymethyl (meth) acrylamide; dialkyl (meth) acrylamide monomers such as dimethyl (meth) acrylamide and diethyl (meth) acrylamide; (meth) acrylamide, N-methylol (meta ) Acrylamide, (meth) acryloylmorpholine, and the like. Of these, dialkyl (meth) acrylamide monomers are preferred, and dimethyl (meth) acrylamide is particularly preferred from the viewpoint of compatibility with the antistatic agent (B) described below and durability.

In addition, the said amide group containing monomer (a2) may be used independently, and may use 2 or more types together.

The acrylic resin (A) of the present invention preferably further contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer (a3), and, if necessary, other copolymerizable ethylenic monomers. You may contain the structural unit derived from unsaturated monomer (a4) (Hereinafter, it may describe as "other copolymerizable monomer (a4).").

The structural unit derived from the (meth) acrylic acid alkyl ester monomer (a3) occupies the main structural unit of the acrylic resin (A), and the content is preferably 50 to 99% by weight, more preferably. Is 60 to 98% by weight, more preferably 70 to 95% by weight, particularly preferably 70 to 93% by weight. When the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a3) is too large, the structural unit derived from the amide group-containing monomer (a2) and the monomer (a1) containing a functional group other than the amide group When the content of the structural unit is decreased, the effects of the present invention tend to be difficult to obtain. When the content is too small, it is difficult to increase the molecular weight of the acrylic resin, and the productivity tends to decrease.

As the above (meth) acrylic acid alkyl ester monomer (a3), for example, the alkyl group usually has 1 to 20, preferably 1 to 18, more preferably 1 to 12, particularly 1 to 8 carbon atoms. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) ) Acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate , Cyclohexyl (meth) acrylate, Bornyl (meth) acrylate and the like. Of these, n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferred from the viewpoint of versatility and adhesive properties. These may be used alone or in combination of two or more.

The content of the structural unit derived from the other copolymerizable monomer (a4) is preferably 0 to 50% by weight, more preferably 3 to 20% by weight, still more preferably 5 to 20% by weight, particularly preferably. Is 6 to 15% by weight. If the content of the other copolymerizable monomer (a4) is too large, the glass transition temperature tends to be high and the reworkability tends to be reduced. If the content is too small, the refractive index adjustment effect tends to be difficult to be exhibited. .

Examples of the other copolymerizable monomer (a4) include aromatic ring-containing monomers such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and orthophenylphenoxyethyl (meth) acrylate. Alicyclic monomers such as cyclohexyloxyalkyl (meth) acrylate, t-butylcyclohexyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentanyl (meth) acrylate; acrylonitrile, methacrylonitrile, Examples thereof include vinyl acetate, vinyl stearate, vinyl chloride, vinylidene chloride, vinyl toluene, vinyl pyrrolidone, methyl vinyl ketone, and dimethylallyl vinyl ketone. These may be used alone or in combination of two or more.

Among these, an aromatic ring-containing monomer is preferable from the viewpoint of easy adjustment of refractive index and birefringence, and more preferably benzyl (meth) acrylate, phenoxy (meth) ethyl acrylate, phenoxydiethylene glycol ( (Meth) acrylate is used. In addition, an alicyclic-containing monomer is preferably used because it is easy to adjust the refractive index and birefringence and is excellent in adhesion to a low-polar adherend (cycloolefin).

In particular, when the other copolymerizable monomer (a4) is other than an aromatic ring-containing monomer and an alicyclic ring-containing monomer, the content of structural units derived from the other copolymerizable monomer (a4) is 0 to 10% by weight. Preferably, it is 0 to 5% by weight. When there is too much content, the tendency for the long-term storage stability of an adhesive composition to fall or for compatibility to fall will be seen.

The content ratio of the structural units derived from the monomers (a1) to (a4) in the acrylic resin (A) can be measured, for example, as follows. That is, from the polarizing plate with the pressure-sensitive adhesive layer obtained by the method described later, only the pressure-sensitive adhesive layer was collected by picking, and ¹ H-NMR measurement (CDCl) was performed under the following <measurement conditions> using the NMR apparatus described later. ₃ , 300K) and ¹³ C-NMR measurement (CDCl ₃ , MAS, 300K), the content ratio of the structural units derived from the monomers (a1) to (a4) in the acrylic resin in the pressure-sensitive adhesive layer was determined. Can be calculated.

<measuring equipment>
NMR (Bruker Biospin AVANCE-600 (1H), Varian, UNITY-INOVA-400 (13C))

<Measurement condition>
Observation frequency: 600MHz (1H), 100MHz (13C)
Measurement solvent: CDCl ₃ (addition of a small amount of pyridine-d5 at the time of 13C measurement)
Measurement temperature: 300K (1H), 300K (13C)
Chemical shift standard: Measurement solvent (1H; 7.25 ppm, 13C; 77.05 ppm)
Sample rotation speed: 20 Hz (1 H), 2,000 Hz (13 C)

The acrylic resin (A) used in the present invention is a monomer (a1) containing a functional group other than an amide group, an amide group-containing monomer (a2), and a (meth) acrylic acid alkyl ester monomer, which are appropriately selected. The copolymer component containing (a3) and other copolymerizable monomers (a4) can be produced by polymerization. The polymerization can be performed by a conventionally known method such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization or the like.

That is, the acrylic resin (A) is polymerized under predetermined polymerization conditions by, for example, mixing or dropping a copolymerization component containing a monomer appropriately selected from the above and a polymerization initiator in an organic solvent. Can do. Of these polymerization methods, solution radical polymerization and bulk polymerization are preferable, and solution radical polymerization is more preferably used.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane; esters such as ethyl acetate and butyl acetate; n-propyl alcohol and isopropyl alcohol. Aliphatic alcohols such as acetone; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Among these solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, methyl isobutyl ketone from the viewpoint of ease of polymerization reaction, chain transfer effect, ease of drying during adhesive coating, and safety Of these, ethyl acetate, acetone, and methyl ethyl ketone are preferably used.

Examples of the polymerization initiator used for the solution radical polymerization include 2,2′-azobisisobutyronitrile and 2,2′-azobis-2-methylbutyronitrile, which are usual radical polymerization initiators. Azo initiators such as 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (methylpropionic acid); benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, cumene Examples thereof include organic peroxides such as hydroperoxide, which can be appropriately selected according to the monomer used. These solvents are used alone or in combination of two or more.

In the present invention, the weight average molecular weight of the acrylic resin (A) is preferably 600,000 to 2,500,000, more preferably 1,000,000 to 1,800,000, still more preferably 1,200,000 to 1,550,000, particularly preferably 1,400,000. ~ 150,000. When the weight average molecular weight is too small, the durability tends to be lowered. When the weight average molecular weight is too large, a large amount of a diluent solvent is required at the time of production, and thus the drying property tends to be lowered.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in a high performance liquid chromatography (The Japan Waters company, "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler Measured by using three series of particle diameters: 10 μm).

In the present invention, the acrylic resin (A) may be a single acrylic resin or may be a blend of two or more acrylic resins. Among them, a point where a wide range of physical properties can be adjusted, a gel fraction can be finely adjusted by blending, and a blend of two or more acrylic resins from the viewpoint of durability is preferable. In consideration of productivity and the like, it is preferable to blend two kinds of acrylic resins.

In the case where the acrylic resin (A) is an acrylic resin composition obtained by blending two types of acrylic resins, the structural unit derived from the amide group-containing monomer (a2) is included in both of the acrylic resins to be blended. Acrylic resin that does not contain a structural unit derived from the monomer (a1) containing a functional group other than an amide group, although it may be contained only in one of the acrylic resins. It is preferable that it is contained.

Further, the structural unit derived from the monomer (a1) containing a functional group other than the amide group may be contained in both of the acrylic resins to be blended, or may be contained only in one acrylic resin, It is preferably contained only in one of the acrylic resins, and more preferably, it is contained in the acrylic resin not containing the structural unit derived from the amide group-containing monomer (a2). .

That is, as an acrylic resin (A), in particular, when an acrylic resin composition containing two types of acrylic resins is used, the combination of the two types of acrylic resins to be blended includes an amide group Combination of acrylic resin (Aab) containing both structural unit derived from monomer (a2) and structural unit derived from monomer (a1) containing functional group other than amide group, derived from amide group-containing monomer (a2) A structure derived from an acrylic resin (Aa) containing a structural unit and not containing a structural unit derived from a monomer (a1) containing a functional group other than an amide group, and a monomer (a1) containing a functional group other than an amide group A combination with an acrylic resin (Ab) containing a unit and containing no structural unit derived from the amide group-containing monomer (a2), or an amide The acrylic resin (Aa) or the acrylic resin containing an acrylic resin (Aab) containing both the structural unit derived from the monomer (a2) and the structural unit derived from the monomer (a1) containing a functional group other than an amide group. Any of the resins (Ab) can be combined.

Among them, in the present invention, an acrylic resin (Aa) containing a structural unit derived from the amide group-containing monomer (a2) and not containing a structural unit derived from the monomer (a1) containing a functional group other than the amide group; It is possible to blend an acrylic resin (Ab) containing a structural unit derived from the monomer (a1) containing a functional group other than an amide group and not containing a structural unit derived from the amide group-containing monomer (a2). It is preferable in terms of durability.

This is because a pseudo-crosslinked structure is formed between the two types of acrylic resins due to the interaction between the acrylic resins (Aa) and (Ab). This is presumed to be due to exerting strength and excellent stress relaxation properties. In particular, when an acrylic resin containing a carboxyl group is used as the acrylic resin (Ab) containing a functional group other than an amide group, an amide group that is an electron donating group and a carboxyl group that is an electron withdrawing group Due to the electronic interaction between the two resins, a physical pseudo-bonding force is generated between the acrylic resins (Aa) and (Ab), and the internal cohesive force becomes higher. Therefore, the stress relaxation property is excellent and the durability is high. It is considered that a good pressure-sensitive adhesive layer is formed.

The content of the amide group-containing monomer (a2) in the acrylic resin (Aa) is preferably 1 to 25% by weight, more preferably 2 to 15% by weight based on the total polymerization components of the acrylic resin (Aa). %, More preferably 3 to 10% by weight, particularly preferably 4 to 7% by weight. When the ratio with respect to the whole polymerization component is too small, sufficient cohesive force as an adhesive does not appear, and the durability after heating and humidification tends to be lowered. On the other hand, if the proportion of the polymerization component is too large, the proportion of the polar component of the pressure-sensitive adhesive increases, and the pressure-sensitive adhesive layer easily absorbs moisture, so that the durability is similarly reduced, such as foaming in a heating test. There is a tendency to

In the acrylic resin (Ab), the amount of the monomer (a1) containing a functional group other than an amide group is preferably 1 to 20% by weight based on the entire polymerization component of the acrylic resin (Ab). More preferred is 1.5 to 15% by weight, still more preferred is 2 to 12% by weight, and particularly preferred is 2.5 to 8% by weight. If the ratio to the entire polymerization component is too small, a large number of functional groups remain, which tends to cause changes in physical properties over time, and the ratio of the polar component of the adhesive increases, and the adhesive layer absorbs moisture. Therefore, durability tends to decrease, such as foaming by heating. When the ratio with respect to the whole polymerization component is too large, the acrylic resin does not sufficiently react with the cross-linking agent in the cross-linking reaction, and sufficient cohesive force does not appear as an adhesive, so that the durability tends to decrease.
As the monomer (a1) containing a functional group other than an amide group in the acrylic resin (Ab), a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferable, and in particular, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are used in combination. It is preferable.

As a blend ratio when blending two kinds of acrylic resins, for example, an acrylic resin (Aa) having a structural unit derived from an amide group-containing monomer (a2) and a monomer containing a functional group other than an amide group In the case of a combination with the acrylic resin (Ab) having a structural unit derived from (a1), it is preferable that (Ab) :( Aa) = 100: 40 to 100: 500 (weight ratio), more preferably ( Ab) :( Aa) = 100: 60 to 100: 400 (weight ratio), more preferably (Ab) :( Aa) = 100: 80 to 100: 350 (weight ratio). If the ratio of the acrylic resin (Aa) to the acrylic resin (Ab) is too large, the crosslinking degree of the pressure-sensitive adhesive tends to decrease and the cohesive force tends to decrease, and if it is too small, the crosslinking degree of the pressure-sensitive adhesive increases. Tends to decrease.

In the case where two or more kinds of acrylic resins are blended, the weight average molecular weight of each acrylic resin is preferably 1 million to 2 million, particularly preferably 1.3 million to 1.6 million. If the weight average molecular weight is too small, the durability tends to decrease, and if the weight average molecular weight is too large, the compatibility tends to decrease and the adhesive properties tend to be non-uniform.

When blending two or more kinds of acrylic resins, the degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) in which two or more kinds are blended is preferably 30 or less. Preferably it is 15 or less, More preferably, it is 7 or less, Most preferably, it is 5 or less. If the degree of dispersion is too high, the cohesive force tends to decrease. The lower limit of the degree of dispersion is usually 2.

<Antistatic agent (B)>
Next, the antistatic agent (B) used in the pressure-sensitive adhesive composition of the present invention will be described. The antistatic agent (B) used in the pressure-sensitive adhesive composition of the present invention is an ammonium antistatic agent. Specifically, a quaternary ammonium salt cation type antistatic agent such as an alkylammonium sulfonate is used. can give. Examples of the alkylammonium salts include, for example, methyltri-n-butylammonium bis (trifluoromethanesulfonyl) imide [melting point: 27.5 ° C. (manufacturer published value) (product name: FC-4400) manufactured by 3M]], tetra Butylammonium bis (trifluoromethylsulfonyl) imide [melting point 92 ° C. (manufacturer announced value) (manufactured by MERCK)], tetrabutylammonium bromide [melting point 119 ° C. (manufacturer announced value) (manufactured by Wako Pure Chemical Industries, Ltd.)], tetra Pentylammonium bromide [melting point: 98 ° C. (manufacturer published value) (manufactured by Wako Pure Chemical Industries, Ltd.)], tetraoctyl ammonium bromide [melting point: 99 ° C. (manufacturer published value) (manufactured by Wako Pure Chemical Industries, Ltd.)], ethyldimethylpropylammonium bis (Trifluoromethylsulfonyl) imide [melting point-1 ° C (manufactured value) (manufactured by MERCK)], n-butyltrimethylammonium bis (trifluoromethanesulfonyl) imide [melting point: 19 ° C (from ionic liquid II CMC publication ISBN 978-4-7813-0878-4)], methyltri Octylammonium bis (trifluoromethylsulfonyl) imide [melting point −75 ° C. (from ionic liquid II CMC publication ISBN978-4-7813-0878-4)], tributylmethylammonium methyl sulfate [solid (manufactured by Ardrich)], tributyl Methylammonium methylsulfate, tetrabutylammonium bis (trifluoromethylsulfonyl) imide, tetraethylammonium trifluoromethanesulfonate, tetrabutylammonium benzoate, tetrabuty Examples thereof include ruammonium methane sulfate, tetrabutylammonium nonafluorobutanesulfonate, tetra-n-butylammonium hexafluorophosphate, tetrabutylammonium trifluoroacetate, tetrahexylammonium tetrafluoroborate, and tetrahexylammonium bromide. These may be used alone or in combination of two or more.

The antistatic agent (B) is preferably solid at room temperature (25 ° C.), and preferably has a melting point of 25 to 120 ° C., particularly preferably 25 to 100 ° C. The temperature is preferably 25 to 50 ° C. If the melting point is too low, the durability tends to decrease drastically when bleeded out.If it is too high, the antistatic agent will remain untied when dissolved, and it will take a long time to dissolve. Tend. In addition, regarding the melting point when two or more kinds are mixed as the antistatic agent (B), the average melting point value calculated from the melting point and the blending ratio (distribution ratio) of each antistatic agent to be mixed is regarded as the melting point.

Therefore, the antistatic agent (B) is, among the above examples, methyltri-n-butylammonium bis (trifluoromethanesulfonyl) imide (manufactured by 3M), tetrabutylammonium bis (trifluoromethylsulfonyl) from the viewpoint of melting point. Imido (made by MERCK), tetrabutylammonium bromide (made by Wako Pure Chemical Industries), tetrapentylammonium bromide (made by Wako Pure Chemical Industries), tetraoctylammonium bromide (made by Wako Pure Chemical Industries), tributylmethylammonium methyl Sulfate (manufactured by Ardrich) is preferably used, and methyltri-n-butylammonium bis (trifluoromethanesulfonyl) imide (manufactured by 3M) is particularly preferably used.

From the viewpoint of antistatic performance, an antistatic agent in which the anionic component of the antistatic agent (B) is a (trifluoromethanesulfonyl) imide anion is preferable, and in particular, methyltri-n-butylammonium bis (trifluoromethane). Sulfonyl) imide (manufactured by 3M) is preferably used.

The cation component of the ammonium antistatic agent (B) of the present invention is preferably an alkylammonium cation, and the alkyl chain has 1 carbon atom in view of excellent compatibility with the acrylic resin (A). Particularly preferred are alkylammonium cations having from 6 to 6 alkyl groups. When the carbon number of the alkyl chain is too large, the melting point and the conductivity tend to decrease.

The content of the antistatic agent (B) is 1.2 to 15 parts by weight, more preferably 2.5 to 14 parts by weight, still more preferably 5 to 5 parts by weight based on 100 parts by weight of the acrylic resin (A). 13 parts by weight, particularly preferably 9 to 12 parts by weight. If the content of the antistatic agent (B) is too small, sufficient antistatic performance may not be obtained, or the antistatic performance tends to deteriorate over time, and if it is too large, the antistatic agent (B) However, it tends to bleed out as a crystal and cause a defective appearance as a bright spot of a liquid crystal display panel, and the durability tends to be remarkably reduced.

In the present invention, the antistatic agent (B) is composed of an ammonium antistatic agent, but an antistatic agent other than the ammonium antistatic agent may be used in combination. Examples of other antistatic agents include those commonly used, such as imidazolium salts, aliphatic sulfonates, higher alcohol sulfates, higher alcohol alkylene oxide adduct sulfates, higher alcohol phosphates. Anionic antistatic agents such as higher alcohol alkylene oxide adduct phosphoric acid ester salts, alkali metal salts such as potassium bis (fluorosulfonyl) imide, lithium bis (trifluorosulfonyl) imide and lithium chloride, alkaline earth metal salts, Examples include higher alcohol alkylene oxide adducts, polyalkylene glycol fatty acid esters, and the like. When the other antistatic agent is used in combination, it may be used within a range that does not impair the effect of the ammonium antistatic agent. Specifically, the blending amount of the other antistatic agent is usually charged. It is used in the range of 5% by weight or less of the whole inhibitor.

The pressure-sensitive adhesive composition of the present invention contains the specific acrylic resin (A) and the antistatic agent (B) as essential components, and the pressure-sensitive adhesive composition is crosslinked with a crosslinking agent (C). Thus, the pressure-sensitive adhesive of the present invention can be obtained.

Examples of the crosslinking agent (C) include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, metal chelate crosslinking agents, and the like. .

Examples of the isocyanate crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof And adducts of polyol compounds such as trimethylolpropane, and burettes and isocyanurates of these polyisocyanate compounds. Among them, an adduct body of 2,4-tolylene diisocyanate with trimethylolpropane is particularly preferable in terms of a long pot life and excellent compatibility with a resin.

Examples of the epoxy-based crosslinking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl ether. , Trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N , N, N′N′-tetraglycidyl-m-xylylenediamine and the like. Of these, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane and N, N, N′N′-tetraglycidyl-m-xylylenediamine are particularly preferred because of high reactivity.

Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4. Examples include '-bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like.

Examples of the melamine-based crosslinking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexaptoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyloxymethyl melamine, and melamine resin. .

Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

Examples of the amine crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, and polyamide.

Examples of the metal chelate-based crosslinking agent include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. can give.

Among these, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are preferable from the viewpoint of excellent durability and light leakage resistance, and it is particularly preferable to use an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent in combination. Moreover, in this invention, an isocyanate type crosslinking agent is preferable also from the point which aging property improves by the catalytic effect of an ammonium type antistatic agent.

In addition, these crosslinking agents (C) may be used independently and may use 2 or more types together.

The content of the crosslinking agent (C) is preferably 0.001 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, and still more preferably 0.001 parts by weight with respect to 100 parts by weight of the acrylic resin (A). 3 to 7 parts by weight, particularly preferably 0.5 to 6 parts by weight. When the amount of the crosslinking agent (C) is too small, the durability tends to decrease. When the amount is too large, the stress relaxation property tends to decrease or the aging property tends to decrease.

The pressure-sensitive adhesive composition of the present invention preferably further contains a silane coupling agent (D). When this silane coupling agent (D) is blended, the adhesiveness to the optical member can be improved when it is used as an adhesive.

Examples of the silane coupling agent (D) include an epoxy group-containing silane coupling agent, a (meth) acryloyl group-containing silane coupling agent, a mercapto group-containing silane coupling agent, a hydroxyl group-containing silane coupling agent, and a carboxyl group-containing. Examples thereof include a silane coupling agent, an amino group-containing silane coupling agent, an amide group-containing silane coupling agent, and an isocyanate group-containing silane coupling agent. These may be used alone or in combination of two or more.

Among these, an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent are preferably used, and it is also possible to use an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent in combination with moisture and heat resistance. It is preferable in that the improvement and the adhesive strength do not increase excessively. An oligomer type silane compound that is partially hydrolyzed and polycondensed is also preferred in terms of excellent durability and reworkability.

Specific examples of the epoxy group-containing silane coupling agent include, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycol. Sidoxypropylmethyldimethoxysilane, methyltri (glycidyl) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and the like are preferable. Γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, and the like. .

Specific examples of the mercapto group-containing silane coupling agent include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, SH group-containing silicone alkoxy oligomer (mercapto group-modified). Ethyl / methyl silicate low condensate).

The content of the silane coupling agent (D) is usually 0.001 to 10 parts by weight, preferably 0.01 to 1 part by weight, more preferably 100 parts by weight of the acrylic resin (A). Is 0.03 to 0.8 part by weight, particularly preferably 0.05 to 0.5 part by weight. When there is too little content of the said silane coupling agent (D), the tendency for the adhesiveness with respect to an optical member to be not improved is seen, and when too much, the tendency for bleed out and durability to fall is seen. Further, the adhesiveness of the pressure-sensitive adhesive is excessively increased and the reworkability tends to be lowered.

Furthermore, the pressure-sensitive adhesive composition of the present invention includes other pressure-sensitive adhesives, urethane resins, rosins, rosin esters, hydrogenated rosin esters, phenol resins, aliphatic petroleum resins, and fats as long as the effects of the present invention are not impaired. Various additives such as tackifiers such as cyclic petroleum resins and styrene resins, colorants, fillers, antioxidants, UV absorbers, functional dyes, and coloration or discoloration caused by UV or radiation irradiation Such compounds can be blended. In addition to the above additives, a small amount of impurities and the like contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition may be contained. These blending amounts are appropriately set so as to obtain desired physical properties.

In the present invention, an optical member with an adhesive layer can be obtained by laminating and forming an adhesive layer formed by crosslinking the adhesive composition of the present invention on an optical member (optical laminate).

In the optical member with the pressure-sensitive adhesive layer, it is preferable to further provide a release sheet on the surface opposite to the optical member surface of the pressure-sensitive adhesive layer.

As a manufacturing method of the said optical member with an adhesive layer, after apply | coating an adhesive composition on an optical member and drying, a release sheet is bonded and it is room temperature (23 degreeC) or a heating state. [2] A method in which the pressure-sensitive adhesive composition is applied on a polarizing plate, dried, and further subjected to aging treatment at room temperature or in a heated state, and then a release sheet is pasted, [3 ] A method in which a pressure-sensitive adhesive composition is applied on a release sheet and dried, and then a polarizing plate is bonded thereto, followed by aging treatment at room temperature or in a heated state. [4] A pressure-sensitive adhesive composition on a release sheet. There is a method in which a polarizing plate is pasted after applying, drying, and performing an aging treatment at room temperature or in a heated state. Especially, the method of said [2] is preferable at the point which does not damage a base material and the point which is excellent in adhesiveness with a base material.

The above aging treatment is performed to balance the physical properties of the adhesive as the reaction time of the chemical crosslinking of the adhesive. As the aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. Specifically, for example, the treatment may be performed under conditions of 23 ° C. for 1 day to 20 days, 23 ° C. for 3 days to 10 days, 40 ° C. for 1 day to 7 days, and the like.

The above-mentioned aging treatment is a treatment performed to balance the physical properties of the adhesive. For example, when the adhesive composition is crosslinked using an isocyanate-based crosslinking agent, the aging is particularly preferably about 23 days at 23 ° C.

Note that the pressure-sensitive adhesive composition of the present invention has excellent aging characteristics, cross-linking proceeds in a short time, and the gel fraction increases and stabilizes, so that even if the aging treatment period is short, the pressure-sensitive adhesive properties are excellent. Adhesive can be obtained. Therefore, the aging treatment period can be shortened compared to the conventional case, which is very advantageous in terms of productivity. In addition, since the physical properties of the adhesive are stabilized in a short time, for example, when the film with the pressure-sensitive adhesive layer is stored in a roll, the so-called “Yuzu skin” problem that the particles of the anti-blocking layer of the protective film are transferred to the pressure-sensitive adhesive can be suppressed. .

In applying the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition is preferably diluted with a solvent, and the diluted concentration is preferably 5 to 60% by weight, more preferably 10 to 10% as a heating residue concentration. 30% by weight. The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition. For example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone, methyl ethyl ketone, A ketone solvent such as methyl isobutyl ketone, an aromatic solvent such as toluene and xylene, and an alcohol solvent such as methanol, ethanol and propyl alcohol can be used. Among these, ester solvents, particularly ethyl acetate, ketone solvents, particularly methyl ethyl ketone, are preferably used from the viewpoints of solubility, drying properties, cost, and the like.

In addition, the application of the pressure-sensitive adhesive composition is performed by a conventional method such as roll coating, die coating, gravure coating, comma coating, or screen printing.

Regarding the gel fraction of the pressure-sensitive adhesive layer produced by the above-mentioned method, the gel fraction of the pressure-sensitive adhesive layer that has passed for one day after the application and drying of the pressure-sensitive adhesive composition solution is defined as “initial gel fraction Gi” and room temperature (23 The gel fraction of the sample aged for another 6 days under “° C.” is “gel fraction Ga after aging”, and the gel fraction of the pressure-sensitive adhesive layer heated for 24 hours in an 80 ° C. oven after the above 6-day aging In the case of “gel fraction Gh after heating”, the gel fraction Ga of the pressure-sensitive adhesive layer is preferably 40 to 85%, more preferably 45 to 75 from the viewpoint of durability performance and light leakage prevention performance. %, And more preferably 50 to 70%. If the gel fraction Ga is too low, the cohesive force of the pressure-sensitive adhesive layer becomes weak and tends to generate bubbles at high temperatures. If it is too high, the pressure-sensitive adhesive layer becomes hard, There is a tendency that the adhesiveness of the resin is lowered and peeling easily occurs. The gel fraction is adjusted, for example, by adjusting the amount and type of the crosslinking agent, the blend ratio of the acrylic resin (A) that is a component of the pressure-sensitive adhesive composition, the monomer composition of the acrylic resin (A), and the molecular weight. It can be adjusted depending on the situation.

Further, the rate of change (Ga / Gi) of the gel fraction Ga after aging of the pressure-sensitive adhesive layer produced by the above method with respect to the initial gel fraction Gi is usually less than 300%, preferably less than 150%. . When the change rate (Ga / Gi) of the gel fraction Ga after the aging is too high, the aging period until the physical properties of the pressure-sensitive adhesive layer are stabilized tends to be long, and the productivity tends to decrease.

Furthermore, the rate of change (Gh / Ga) of the gel fraction Gh after heating of the pressure-sensitive adhesive layer with respect to the gel fraction Ga after aging is usually 90 to 110%, preferably 95 to 105%. When the rate of change (Gh / Ga) of the gel fraction Gh after the heating is too low or too high, the physical properties of the pressure-sensitive adhesive vary depending on the environment of the storage location, and the durability tends to decrease. is there.

In addition, the said gel fraction becomes a standard of the crosslinking degree (hardening degree) of a composition, for example, is computed by the following method. That is, the pressure-sensitive adhesive layer is peeled off from the pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is formed on the optical member (for example, a polarizing plate) as a base material, and the pressure-sensitive adhesive layer is wrapped with a 200-mesh SUS wire mesh, The weight percentage of the insoluble pressure-sensitive adhesive component (cross-linked portion) immersed in the wire mesh at 23 ° C. for 24 hours is defined as the gel fraction. The initial gel fraction Gi, the gel fraction Ga after aging, and the gel fraction Gh after heating, including the aging conditions and measurement methods, will be described in detail in the following examples.

The initial adhesive strength is calculated as follows. About the polarizing plate with an adhesive layer, it cut | judged to width 25mm width, peels a release sheet, presses the adhesive layer side to a non-alkali glass board (Corning company make, "Eagle XG"), A glass plate is bonded. Thereafter, after autoclaving (50 ° C., 0.5 MPa, 20 minutes), the sample is left at 23 ° C. and 50% RH for 24 hours, and then subjected to a 180 ° C. peeling test.

The thickness of the pressure-sensitive adhesive layer in the optical member with the pressure-sensitive adhesive layer is preferably 5 to 300 μm, more preferably 10 to 50 μm, and still more preferably 10 to 30 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, the physical properties of the pressure-sensitive adhesive tend to be difficult to stabilize, and if it is too thick, the appearance defect tends to increase such as bubbles being included during production.

The optical member in the present invention is not particularly limited, and an optical film suitably used for an image display device such as a liquid crystal display device, an organic EL display device, or a PDP, such as a polarizing plate, a retardation plate, or an elliptical polarizing plate. , Optical compensation films, brightness enhancement films, and those in which these are laminated. Especially, it is effective in this invention that it is a polarizing plate, and it is effective in this invention that it is especially a polarizing plate by which high durability is requested | required, such as resisting the shrinkage | contraction of a polarizer.

Therefore, the liquid crystal display panel in which the polarizing plate is attached to the liquid crystal cell (glass plate) using the pressure-sensitive adhesive of the present invention has antistatic performance on the surface even if it is continuously used under severe conditions such as high temperature and high humidity. However, the liquid crystal display panel is excellent in durability and does not deteriorate over a long period of time and does not cause defects such as peeling off of the polarizing plate.

In addition, the polarizing plate used in the present invention is usually laminated as a protective film on both sides of the polarizing film, and for the purpose of thinning, the protective film on the side to be bonded to the polarizing plate is eliminated. There is also a film polarizing plate. Examples of the protective film include highly hydrophobic resin films such as acrylic films, polyethylene films, polypropylene films, and cycloolefin films. In addition, in this invention, it can apply also to what used the normal triacetylcellulose film as a protective film.

As the polarizing film, a film made of a polyvinyl alcohol-based resin having an average polymerization degree of 1,500 to 10,000 and a saponification degree of 85 to 100 mol% is used as an original film, and an iodine-potassium iodide aqueous solution or two A uniaxially stretched film dyed with a chromatic dye (usually a stretch ratio of about 2 to 10 times, preferably about 3 to 7 times) is used.

The polyvinyl alcohol resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), olefins, vinyl ether And a component copolymerizable with vinyl acetate, such as an unsaturated sulfonate. Moreover, you may use what is called polyvinyl acetal resin and polyvinyl alcohol derivatives, such as polybutyral resin, polyvinyl formal resin, etc. which reacted polyvinyl alcohol with aldehydes in presence of an acid.

As the antistatic performance of the polarizing plate with the pressure-sensitive adhesive layer produced by the above method, after producing the polarizing plate with the pressure-sensitive adhesive layer, the plate is allowed to stand for 24 hours in an atmosphere of 23 ° C. × 50% RH, The “initial surface resistance value Ri” obtained by removing the separator and measuring the surface resistance value of the pressure-sensitive adhesive layer using a surface resistivity measuring apparatus described later is preferably 1.0 × 10 ¹² Ω / Less than □, more preferably less than 1.0 × 10 ¹¹ Ω / □, and still more preferably less than 5.0 × 10 ⁹ Ω / □. If the initial surface resistance value Ri is too high, the polarizing plate is charged due to friction with the backlight of the liquid crystal display panel, etc., and there is a tendency to cause display defects.

In addition, the antistatic property of the polarizing plate with the pressure-sensitive adhesive layer with respect to time stability is as follows. After the polarizing plate with the pressure-sensitive adhesive layer is produced, it is stored in an oven at a temperature of 40 ° C. and a humidity of 90% RH for 100 hours. After leaving still for 24 hours in an atmosphere of 50 ° C. × 50% RH, the separator of the pressure-sensitive adhesive layer was removed, and the value obtained by measuring the surface resistance value of the pressure-sensitive adhesive layer using a surface resistivity measuring device described later was used. In the case of “surface resistance value Rt after humidification”, “surface resistance value Rt after humidification” / “initial surface resistance value Ri” = time-dependent change rate, the time-dependent change rate (Rt / Ri) is preferably 0. In the range of 0.6 to 1.4, more preferably in the range of 0.8 to 1.2, and still more preferably in the range of 0.9 to 1.1. If the anti-static performance changes over time (the change in the rate of change over time) is too large, the product will vary, and the polarizing plate may become damaged due to friction with the backlight of the liquid crystal display panel in long-term or high-temperature / high-humidity use. There is a tendency to be charged and display defects. Further, when used for a touch panel or the like, the sensitivity of the sensor changes, and there is a tendency that it does not drive normally.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, “parts” and “%” mean weight basis.

First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight of acrylic resin and the gel fraction of an adhesive, it measured according to the above-mentioned method.

[Preparation of acrylic resin (A)]
In the following resin production, (a1) to (a4) added after the substance name represent the type of monomer, (a1) represents a monomer containing a functional group other than an amide group, and (a2) represents an amide group. The containing monomer, (a3) is a (meth) acrylic acid alkyl ester monomer, and (a4) is another copolymerizable monomer.

<Manufacture of acrylic resin (A-1)>
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 82.5 parts of butyl acrylate [BA] (a3), 10 parts of benzyl acrylate [BzA] (a4), 0.5 parts of 2-hydroxyethyl acrylate [HEA] (a1), 7 parts of acrylic acid [AAc] (a1), 47.2 parts of ethyl acetate as a solvent, 42 parts of acetone, azobisisobutyronitrile as a polymerization initiator [AIBN] 0.013 part was added, and AIBN and ethyl acetate were added as appropriate. After reacting at reflux temperature for 3.25 hours, diluted with ethyl acetate to obtain acrylic resin (A-1) (weight average molecular weight) A solution with 1.5 million and a dispersity of 3.3) was obtained.

<Manufacture of acrylic resin (A-2)>
Into a four-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 88.5 parts of butyl acrylate (a3), 10 parts of benzyl acrylate (a4), 2-hydroxyethyl acrylate ( a1) 0.5 part, 1 part of acrylic acid (a1), 47.2 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.013 part of azobisisobutyronitrile [AIBN] as a polymerization initiator were charged appropriately. And ethyl acetate were added, reacted at reflux temperature for 3.25 hours, diluted with ethyl acetate, and a solution of acrylic resin (A-2) (weight average molecular weight 1,500,000, dispersity 3.4) was obtained. Obtained.

<Manufacture of acrylic resin (A-3)>
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 93 parts of butyl acrylate (a3), 2 parts of methyl methacrylate [MMA] (a3), dimethylacrylamide [DMAA] (A2) 5 parts, 43 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.011 part of azobisisobutyronitrile [AIBN] as a polymerization initiator were added at a reflux temperature while appropriately adding AIBN and ethyl acetate. After reacting for 3.25 hours, the reaction solution was diluted with ethyl acetate to obtain a solution of acrylic resin (A-3) (weight average molecular weight 1.4 million, dispersity 4.6).

<Manufacture of acrylic resin (A-4)>
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 78 parts of butyl acrylate (a3), 2 parts of methyl methacrylate (a3), 20 parts of dimethylacrylamide (a2), 43 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.011 part of azobisisobutyronitrile [AIBN] as a polymerization initiator were added, and after reacting at reflux temperature for 3.25 hours while appropriately adding AIBN and ethyl acetate. Then, it was diluted with ethyl acetate to obtain a solution of acrylic resin (A-4) (weight average molecular weight 1.4 million, dispersity 3.6).

<Manufacture of acrylic resin (A-5)>
Into a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 89.8 parts of butyl acrylate (a3), 5 parts of dimethylacrylamide (a2), 2-hydroxyethyl acrylate ( a1) 0.2 parts, acrylic acid (a1) 5 parts, ethyl acetate 43 parts, acetone 42 parts, azobisisobutyronitrile [AIBN] 0.011 part as a polymerization initiator, and AIBN and acetic acid as appropriate After reacting at reflux temperature for 3.25 hours while adding ethyl, the solution was diluted with ethyl acetate to obtain a solution of acrylic resin (A-5) (weight average molecular weight 1,500,000, dispersity 3.5). .

For the acrylic resins (A-1) to (A-5) produced as described above, the content of the raw material monomer component, the weight average molecular weight (Mw), and the degree of dispersion are shown in Table 1 below.

<Antistatic agent (B)>
Moreover, the following were prepared as an antistatic agent (B).
(B-1): Methyltri-n-butylammonium bis (trifluoromethanesulfonyl) imide Melting point 27.5 ° C. (manufacturer published value) (manufactured by 3M, “FC-4400”)
(B-2): tetrabutylammonium bis (trifluoromethylsulfonyl) imide melting point 92 ° C. (manufacturer published value) (manufactured by MERCK)
(B-3): Tributylmethylammonium methyl sulfate solid (manufactured by Ardrich)
(B-4): 1-butyl, 2,3-dimethylimidazolium trifluoromethanesulfonate Melting point 100 ° C. (manufacturer published value) (manufactured by MERCK)
(B-5): Tetrabutylphosphonium bromide Melting point 100 ° C (manufacturer published value) (manufactured by Wako Pure Chemical Industries, Ltd.)
(B-6): Lithium bistrifluoromethanesulfonylimide (tetraethylene glycol dimethyl ether dispersion) (“Sanconol TGR” manufactured by Sanko Chemical Co., Ltd.)

<Crosslinking agent (C)>
And the following were prepared as a crosslinking agent (C).
(C-1): 55% ethyl acetate solution of tolylene diisocyanate adduct of trimethylolpropane (manufactured by Nippon Polyurethane, “Coronate L-55E”)
(C-2) 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, “Tetrad-C”)

<Silane coupling agent (D)>
Moreover, the following were prepared as a silane coupling agent (D).
(D-1): Epoxy silane coupling agent [3-glycidoxypropyltrimethoxysilane (“KBM-403” manufactured by Shin-Etsu Chemical Co., Ltd.)]

[Examples 1 to 10, Comparative Examples 1 to 7]
[Preparation of adhesive composition (solution)]
A pressure-sensitive adhesive composition was prepared by blending each of the blended components prepared and prepared as described above in the ratio shown in Table 2 below, and this was diluted with ethyl acetate to obtain a pressure-sensitive adhesive composition solution. (Solid content concentration 13%). In Table 2 below, the blending amounts of the antistatic agent (B), the crosslinking agent (C), and the silane coupling agent (D) are values converted based on 100 parts by weight of the entire acrylic resin (A). is there.

Next, the pressure-sensitive adhesive composition solutions of Examples and Comparative Examples were applied to a polyester release sheet so that the thickness after drying was 25 μm, dried at 100 ° C. for 3 minutes, and then formed pressure-sensitive adhesive. The composition layer was transferred to a polarizing plate (protective film: TAC film manufactured by Fuji Film Co., Ltd.) and aged for 7 days under conditions of 23 ° C. × 65% RH to obtain a polarizing plate with a pressure-sensitive adhesive layer for testing.

Using the polarizing plate with the pressure-sensitive adhesive layer obtained above, antistatic performance [initial and humidified surface resistance value and rate of change thereof], aging characteristics [initial and after aging, gel fraction after heating and , Its rate of change] and durability [heat resistance and moist heat resistance] were measured and evaluated according to the following methods. These results are also shown in Table 3 below. In addition, the test sample of the polarizing plate with an adhesive layer was cut and used so that it might become 0 degree | times (parallel) with respect to the extending | stretching axis | shaft of a polarizing plate.

[Evaluation of initial antistatic performance]
The specimen of the polarizing plate with the pressure-sensitive adhesive layer was allowed to stand for 24 hours in an atmosphere of 23 ° C. × 50% RH, and then the separator of the pressure-sensitive adhesive layer was peeled off to obtain a surface resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd.). And the device name “Hiresta-UP MCP-HT450”), the surface resistance value of the pressure-sensitive adhesive layer was measured. This measured value was used as the initial surface resistance value. The evaluation criteria are as follows.
(Evaluation criteria)
A: Less than 5.0 × 10 ⁹ Ω / □ ○: 5.0 × 10 ⁹ Ω / □ or more and less than 1.0 × 10 ¹¹ Ω / □ Δ: 1.0 × 10 ¹¹ Ω / □ or more and 1.0 × Less than 10 ¹² Ω / □ ×: 1.0 × 10 ¹² Ω / □ or more

[Evaluation of antistatic performance after humidification]
In order to see the time-dependent change in antistatic properties, the specimen of the polarizing plate with the pressure-sensitive adhesive layer was stored in an oven at a temperature of 40 ° C. and a relative humidity of 90% for 100 hours, and further under an atmosphere of 23 ° C. × 50% RH. Then, the separator of the pressure-sensitive adhesive layer was peeled off, and the surface resistance value of the pressure-sensitive adhesive layer was measured. This was defined as the surface resistance value after aging (heating). The rate of change was calculated by the following formula using the initial surface resistance value and the surface resistance value after heating. The evaluation criteria are as follows.
Rate of change (change over time) = [surface resistance value after heating] / [initial surface resistance value]
(Evaluation criteria)
◎: Change rate is 0.9 or more and less than 1.1 ○: Change rate is 0.8 or more and less than 0.9, or 1.1 or more and less than 1.2 △: Change rate is 0.6 or more and less than 0.8, Or 1.2 or more and less than 1.4 X: Change rate is less than 0.6 or 1.4 or more

[Evaluation of aging characteristics]
A resin solution is applied to a polyester release sheet so that the thickness after drying is 25 μm, and after drying at 100 ° C. for 3 minutes, the formed pressure-sensitive adhesive composition layer is coated with a polarizing plate (protective film: Fuji TAC film manufactured by Film Co., Ltd.), and samples passed for 1 day under the conditions of 23 ° C. × 65% RH, samples for “initial gel fraction” measurement, 7 days (6 days in addition to the above 1 day) A sample for measuring “gel fraction after aging” was measured, and a sample obtained by aging for 7 days and then put in an oven at 80 ° C. for 24 hours was used as a sample for measuring “gel fraction after heating”.

As described above, the gel fraction was calculated by the following method. That is, the pressure-sensitive adhesive layer is peeled off from a pressure-sensitive adhesive sheet (with no separator attached) formed on a polarizing plate as a base material, and the pressure-sensitive adhesive layer is wrapped with a 200-mesh SUS wire mesh, It was immersed in ethyl at 23 ° C. for 24 hours, and the weight percentage of the insoluble adhesive component remaining in the wire mesh was defined as “gel fraction”.

From the “initial gel fraction” and “gel fraction after aging” obtained by the above method, the change rate of the gel fraction after aging was calculated according to the following formula. The evaluation criteria are as follows.
Change rate of gel fraction after aging (%) = [gel fraction after aging] / [initial gel fraction] × 100
(Evaluation criteria for rate of change of gel fraction after aging)
○: Change rate is less than 150% △: Change rate is 150% or more, less than 300% ×: Change rate is 300% or more

Further, the change rate of the gel fraction after heating was calculated from the “gel fraction after aging” and the “gel fraction after heating” obtained by the above method according to the following formula. The evaluation criteria are as follows.
Change rate of gel fraction after heating (%) = [gel fraction after heating] / [gel fraction after aging] × 100
(Evaluation criteria for rate of change of gel fraction after heating)
○: Change rate is 95% or more and less than 105% Δ: 90% or more and less than 95%, or 105% or more and less than 110% ×: Change rate is less than 90% or 110% or more

[Evaluation of durability]
The release sheet of the obtained polarizing plate sample with the pressure-sensitive adhesive layer is peeled off, and the pressure-sensitive adhesive layer side is pressed against a non-alkali glass plate (Corning Corp., Eagle XG) to bond the polarizing plate and the glass plate. After that, autoclave treatment (50 ° C., 0.5 MPa, 20 minutes) was performed, and then foaming and peeling were evaluated visually in the following durability tests (heat resistance test, heat resistance test). In addition, the size of the test piece used for the test is 20 cm × 15 cm (punching).

〔durability〕
(1) Heat resistance test The evaluation was as follows in an endurance test at 80 ° C for 240 hours.
(2) Moisture and heat resistance test It evaluated as follows in the endurance test of 60 degreeCx90% RH * 240 hours, and the endurance test of 85 degreeCx85% RH * 240 hours.
(Evaluation criteria)
For each of the tests (1) and (2), the presence or absence of defects (foaming, streaks, floating, peeling) was evaluated by optical microscope observation and visual observation. The evaluation criteria are as follows.
(Evaluation criteria)
(Double-circle): The fault was not seen in optical microscope observation.
○: In observation with an optical microscope, defects were observed at the edge within 0.5 mm from the edge of the polarizing plate.
(Triangle | delta): The fault of about 1 mm which can be confirmed visually was seen by the edge part within 0.5 mm from the edge part of a polarizer.
X: The defect which can be confirmed visually was seen in the inner side (near center) from 0.5 mm from the edge part of a polarizing plate. Or peeling of 1 mm or more was observed.

These test results and evaluation are summarized in Table 3 below.

From the evaluation results in Table 3 above, the pressure-sensitive adhesives of Examples 1 to 10 comprising the pressure-sensitive adhesive composition of the present invention are excellent in antistatic performance, durability and aging characteristics in a well-balanced manner. The pressure-sensitive adhesives of Comparative Examples 2 and 3 in which the structural unit derived from the monomer (a1) containing the functional group is less than 1% by weight of the acrylic resin (A) are remarkably inferior in aging characteristics and inferior in durability. It turns out that it is a thing. Further, the pressure-sensitive adhesive of Comparative Example 4 in which the acrylic resin (A) does not have a structural unit derived from the amide group-containing monomer (a2) does not satisfy the temporal stability of the antistatic performance and has poor durability. It can be seen that it is.

Furthermore, the pressure-sensitive adhesives of Comparative Examples 5 to 7 using an antistatic agent other than the ammonium-based antistatic agent as the antistatic agent (B) are also at least one of antistatic performance with time stability, aging characteristics, and durability. It turns out that it is what is not satisfied. And it turns out that the adhesive of Comparative Example 1 in which the blending amount of the antistatic agent (B) is less than the specific range does not satisfy the initial antistatic performance.

In addition, from the evaluation results shown in Table 3 above, in Examples 2, 3 and 9, 10 in which a relatively large amount of the antistatic agent (B) was blended, the pressure-sensitive adhesive layer after the durability test showed that the antistatic agent No occurrence of defects due to bleed out was observed, and the adhesive of the present invention has both durability and aging characteristics even when a relatively large amount of antistatic agent is blended in order to improve the antistatic performance over time. It can be seen that it is excellent in balance.

Further, using the polarizing plate with the pressure-sensitive adhesive layer obtained by using the pressure-sensitive adhesive compositions of Examples 1 to 3, 8 to 10 and Comparative Example 1, antistatic performance [surface resistance value, ESD ganmura disappearance time] was measured and evaluated according to the following methods. The test is shown in Table 4 below.

[Antistatic performance evaluation under low temperature conditions]
After the polarizing plate with the pressure-sensitive adhesive layer produced in each of the above Examples and Comparative Examples was left to stand for 24 hours in a 4 ° C. × 55% RH atmosphere, the pressure-sensitive adhesive layer separator was peeled off, and a surface resistivity measuring device (Mitsubishi Chemical) The evaluation criteria for measuring the surface resistance value of the pressure-sensitive adhesive layer in an atmosphere of 4 ° C. and 55% RH using an apparatus manufactured by Analitech Co., Ltd. (“Hiresta-UP MCP-HT450”) are as follows.
(Evaluation criteria)
A: Less than 5.0 × 10 ⁹ Ω / □ ○: 5.0 × 10 ⁹ Ω / □ or more and less than 1.0 × 10 ¹¹ Ω / □ Δ: 1.0 × 10 ¹¹ Ω / □ or more and 1.0 × Less than 10 ¹² Ω / □ ×: 1.0 × 10 ¹² Ω / □ or more

[LCD unevenness test (ESD gunmura disappearance time)]
The polarizing plate with the pressure-sensitive adhesive layer produced in each of the above Examples and Comparative Examples was cut into 100 mm × 100 mm, and then the release sheet was peeled off and attached to a liquid crystal panel (INNOLAX). In addition, in order to become an opposite surface, the polarizing plate with an adhesive layer prepared separately was stuck in the crossed Nicols state, and it was set as the state which interrupted | blocked the transmitted light.
Next, the liquid crystal panel on which the polarizing plate with the pressure-sensitive adhesive layer was pasted was allowed to stand on the backlight, and an electrostatic tester (ESSB3011 (static tester) manufactured by Noise Research Laboratories) and GT The static electricity of +15 kV was contact-discharged with -30R (discharge gun). At that time, the time (seconds) from the occurrence of the uneven static electricity (whitening phenomenon) to the return to the original state was measured and evaluated. The shorter the time, the better the electrical characteristics. When static electricity is generated on the surface of the polarizing plate, whitening occurs due to static electricity unevenness and the liquid crystal becomes defective in display. The measurement was performed in a 23 ° C., 55% RH atmosphere and in a 4 ° C., 55% RH atmosphere.
(Evaluation criteria)
A: Static unevenness disappeared in less than 1 second.
○: Static electricity nonuniformity disappeared in 1 second or more and less than 5 seconds.
Δ: Static electricity nonuniformity disappeared in 5 seconds or more and less than 20 seconds.
X: Static electricity nonuniformity disappeared in 20 seconds or more.

From the evaluation results shown in Table 4 above, the pressure-sensitive adhesives of Examples 1 to 3 and 8 to 10 made of the pressure-sensitive adhesive composition of the present invention have low surface resistance values even under low temperature conditions, and have excellent antistatic performance. You can see that In Examples 1 to 3 and 8 to 10, the surface resistance values of the polarizing plates under the low temperature conditions are all the same evaluation results, and there is no difference depending on the blending amount of the antistatic agent (B). In the display unevenness test on the liquid crystal panel closer to the practical state, Examples 2, 3, 9 and 10 containing a large amount of the antistatic agent (B) are shorter in the disappearance time of the display unevenness and more excellent charging. Further, it can be seen that Examples 3 and 10 have performance against display unevenness comparable to that at room temperature (the above-described initial antistatic performance evaluation conditions). .
From this, the pressure-sensitive adhesive of the present invention has excellent durability and aging characteristics in a balanced manner even when a relatively large amount of antistatic agent is blended in order to improve the temporal stability of the antistatic performance. It can be seen that has excellent antistatic performance even under low temperature conditions.

In the above embodiments, specific forms in the present invention have been described. However, the above embodiments are merely examples and are not construed as limiting. Various modifications apparent to those skilled in the art are contemplated to be within the scope of this invention.

The pressure-sensitive adhesive composition of the present invention and a pressure-sensitive adhesive obtained by crosslinking the same do not cause bleed-out even when the content of the antistatic agent is increased, and the antistatic performance is stable over a long period without adversely affecting the durability. The surface of a polarizing plate using a highly hydrophobic resin for the protective film, particularly an optical member with an adhesive layer obtained by using as an adhesive for optical members. It is very useful as a pressure-sensitive adhesive for adhesion to be applied.

Claims (10)

1. An adhesive composition containing an acrylic resin (A) and an antistatic agent (B), wherein the acrylic resin (A) contains an amide group and a functional group other than an amide group, and an amide group The structural unit derived from the monomer (a1) containing a functional group other than occupies 1 to 10% by weight of the acrylic resin (A), and the antistatic agent (B) comprises an ammonium antistatic agent. A pressure-sensitive adhesive composition, wherein the content of the inhibitor (B) is 1.2 to 15 parts by weight with respect to 100 parts by weight of the acrylic resin (A).
2. The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic resin (A) has a carboxyl group as a functional group other than the amide group.
3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the structural unit derived from a monomer having a carboxyl group accounts for 1 to 5% by weight of the acrylic resin (A).
4. The acrylic resin (A) has a structural unit derived from the amide group-containing monomer (a2), and the structural unit derived from the amide group-containing monomer (a2) accounts for 1 to 25% by weight of the acrylic resin (A). The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein:
5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the acrylic resin (A) is an acrylic resin composition comprising two or more acrylic resins.
6. 6. The pressure-sensitive adhesive composition according to claim 5, wherein the two or more kinds of acrylic resins each have a weight average molecular weight of 1,000,000 to 2,000,000.
7. An acrylic resin (A) containing a structural unit derived from the amide group-containing monomer (a2) and not containing a structural unit derived from the monomer (a1) containing a functional group other than the amide group; An acrylic resin containing an acrylic resin (Ab) containing a structural unit derived from the monomer (a1) containing a functional group other than an amide group and not containing a structural unit derived from the amide group-containing monomer (a2) The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive composition is a composition.
8. The pressure-sensitive adhesive composition according to any one of claims 1 to 7, further comprising a crosslinking agent (C).
9. A pressure-sensitive adhesive, wherein the pressure-sensitive adhesive composition according to any one of claims 1 to 8 is crosslinked with a crosslinking agent (C).
10. A pressure-sensitive adhesive for polarizing plates, comprising the pressure-sensitive adhesive according to claim 9.