TW201406895A - Adhesive composition for polarizer, polarizer with adhesive, and display device - Google Patents

Abstract

The present invention provides an adhesive composition for a polarizer, including: acrylic copolymer A having a structural unit derived from an alkyl (meth)acrylate, a structural unit derived from a monomer having a carboxy group, and a weight-average molecular weight of from 300, 000 to 700, 000; acrylic copolymer B having a structural unit derived from an alkyl (meth)acrylate, a structural unit derived from a monomer having a carboxy group, a structural unit derived from a monomer having a hydroxyl group, and a weight-average molecular weight of from 1, 000, 000 to 2, 000, 000; and an isocyanate cross-linking agent at a content of 20 parts by mass relative to a combined total amount of 100 parts by mass of the acrylic copolymer A and the acrylic copolymer B, in which the glass transition temperature of the acrylic copolymer A is equal to or higher than the glass transition temperature of the acrylic copolymer B.

Description

Adhesive composition for polarizing plate, adhesive with polarizing plate attached thereto, and display device

The present invention relates to an adhesive composition for a polarizing plate, an adhesive polarizer, and a display device.

In recent years, as display devices for displaying images, such as liquid crystal display devices or organic electroluminescence, devices of various display modes have been widely used. In particular, the liquid crystal display device generally has a liquid crystal element in which a liquid crystal component that is aligned in a predetermined direction is sandwiched between two supporting substrates of glass or the like, and is bonded to an optical film such as a polarizing plate, a retardation film, or a saliency lift film. structure. When the optical films are laminated to each other or when the optical film is attached to the liquid crystal element, an adhesive is used.

A liquid crystal display device is widely used as a display device such as a personal computer, a television, or a car navigator. For example, it is used in various environmental conditions such as high temperature and high humidity, high water content, or low humidity and dry environment. Under various environmental conditions. Therefore, it is required to provide a bonding portion (that is, an interface between the adhesive layer and the liquid crystal element or the polarizing film) which is bonded by an adhesive even when used for a long period of time, or not in the adhesive layer. No cracking occurs, and high durability such as generation of bubbles is less likely to occur in the adhesive layer.

Further, the polarizing plate has a polarizing film (polarized sheet) using PVA or the like. When a stretched film is used in this polarizing film, once it is exposed to a severe environment such as high temperature and high humidity, dimensional change easily occurs with shrinkage or expansion, and stress is generated in the polarizing plate. Stress caused by dimensional changes, not When the adhesive disposed between the polarizing plate and the liquid crystal element is relaxed, residual stress is unevenly generated in the polarizing plate. As a result, the phases of the two polarizing plates which are arranged such that the extending axes of the polarizing films are interlaced with each other on the front and back surfaces of the display panel are deviated. Therefore, the four peripheral portions of the display portion of the liquid crystal display device leak light and become white, that is, a so-called "white spot" color spot occurs.

The occurrence frequency or occurrence pattern of the above white spots varies depending on the size of the display panel. From this point of view, generally, a soft display adhesive is used for a small display panel, and a hard hard adhesive is used for a large display panel. When the hard adhesive is attempted to be applied to a small display panel, stress accompanying shrinkage or the like tends to concentrate on the side edges, and the white spots tend to appear remarkably around the periphery of the panel. On the other hand, when a large-sized adhesive is manufactured for a large-sized display panel, it is one of the causes of a decrease in productivity because the edge portion of the entire sheet cannot be effectively utilized. Further, since the soft adhesive is soft, it tends to adhere to the processing blade and tends to have poor punchability.

In order to improve the above white spots, an adhesive which adds a low molecular weight polymer to the adhesive composition to alleviate stress has been proposed. For example, an adhesive composition for a polarizing plate is disclosed, which is composed of a high molecular weight acrylic copolymer, a low molecular weight acrylic copolymer having a weight average molecular weight of 30,000 or less, and a polyfunctional compound. Since there is a characteristic that the dimensional change occurring in the polarizing plate is followed, the color unevenness between the edge portion and the central portion is small (for example, refer to Patent Document 1).

Further, an adhesive composition for a polarizing plate is disclosed, which comprises a (meth)acrylic copolymer (A) having a weight average molecular weight of 65 to 95,000 in a specified ratio, and a weight average molecular weight of 105 to 1.35 million ( The methyl methacrylate copolymer (B) also contains an isocyanate compound, so that it has durability under high temperature and high humidity, and white spots are suppressed (for example, refer to Patent Document 2).

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 10-279907

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-231189

However, as in the above-mentioned conventional techniques, in order to prevent the occurrence of stains represented by white spots, a technique of using a (meth)acrylic copolymer having a different weight average molecular weight has been disclosed, but if it is only mixed, only When a plurality of kinds of molecular weights are different, it is difficult to maintain good durability at the same time to prevent foaming, peeling, or cracking, and to prevent the occurrence of white spots.

The adhesive, from the past, has been continuously adjusted for the composition of the adhesive depending on the use or size. On the other hand, an adhesive which can be applied to a large-sized display panel and a small-sized display panel at the same time and which does not affect the size regardless of the size, and which is excellent in durability and workability has not been proposed yet.

The present invention has been made in view of the above problems. Under the above circumstances, it is considered necessary to have an adhesive composition for a polarizing plate and an adhesive for attaching an adhesive which have high durability against foaming, peeling, and the like, and which are irreducible in size and which suppress the occurrence of color spots (particularly white spots). Further, it is considered necessary to display a display device having a small number of image spots.

The present invention has been achieved based on the following findings. which is, When two or more kinds of resins having different weight average molecular weights are used for blending, among two or more kinds of resins, a resin having a small molecular weight does not contain a polar group such as a hydroxyl group, and the molecular weight is larger than that of the resin compared with a polar group. When a large resin has a small reactivity between a resin having a small molecular weight and a crosslinking agent, the molecular weight tends to decrease, and the durability tends to be lowered. Therefore, focusing on the glass transition temperature of the resin, the isocyanate is adjusted by the copolymerization component. The reactivity between the crosslinking agents can achieve the durability of the adhesive and the prevention of the occurrence of stains.

Specific means for achieving the above problems are as follows.

According to a first aspect of the invention, there is provided a composition for an adhesive for a polarizing plate comprising: a constituent unit derived from an alkyl (meth)acrylate; and a constituent unit derived from a monomer having a carboxyl group, and having a weight average molecular weight of 300,000 or more An acrylic copolymer A of 700,000 or less; a constituent unit derived from an alkyl (meth)acrylate; a constituent unit derived from a monomer having a carboxyl group; and a constituent unit derived from a monomer having a hydroxyl group, and having a weight average molecular weight of An acrylic copolymer B having a content of 1,000,000 or more and 2,000,000 or less; and an isocyanate crosslinking agent in an amount of 20 parts by mass or less based on 100 parts by mass of the total amount of the acrylic copolymer A and the acrylic copolymer B; Further, the glass transition temperature (TgA) of the acrylic copolymer A is equal to or higher than the glass transition temperature (TgB) of the acrylic copolymer B.

According to a second aspect of the invention, there is provided an adhesive polarizer comprising a polarizer sheet and an adhesive layer formed on the polarizer according to the adhesive composition for a polarizing plate of the first invention.

The present invention provides an adhesive composition for a polarizing plate and an adhesive for a polarizing plate which have high durability against foaming, peeling, and the like, and which suppress the occurrence of color spots (especially white spots) irrespective of size. also, The present invention provides a display device in which the displayed image stain is small.

Hereinafter, the adhesive composition for a polarizing plate of the present invention, and an adhesive polarizer and an image display device using the same will be described in detail.

<Binder composition for polarizing plate>

The adhesive composition for a polarizing plate of the present invention is composed of an alkyl (meth)acrylate. a constituent unit and a constituent unit derived from a monomer having a carboxyl group, an acrylic copolymer A having a weight average molecular weight of 300,000 or more and 700,000 or less; a constituent unit derived from an alkyl (meth)acrylate; and a monomer derived from a carboxyl group The constituent unit of the body and the constituent unit derived from the monomer having a hydroxyl group, and the acrylic copolymer B having a weight average molecular weight of 1,000,000 or more and 2,000,000 or less; and an isocyanate crosslinking agent. In the adhesive composition for a polarizing plate of the present invention, the content of the isocyanate crosslinking agent is set to 20 masses per 100 parts by mass of the total amount of the acrylic copolymer A and the acrylic copolymer B. In the range below, the glass transition temperature (TgA) of the acrylic copolymer A and the glass transition temperature (TgB) of the acrylic copolymer B satisfy the relationship of TgA ≧ TgB.

Further, in addition to the acrylic copolymer A and the acrylic copolymer B, the adhesive composition for a polarizing plate of the present invention may further contain other components such as a crosslinking agent, a decane coupling agent, or other additives, as needed.

From the past, techniques for forming an adhesive using a plurality of copolymers having different molecular weights have been known. However, if only a part of the copolymer has a small molecular weight, the effect of suppressing stains such as white spots due to stress relaxation can be expected, but the durability is remarkably low, and the occurrence of foaming, peeling, and the like cannot be suppressed. . Therefore, in the present invention,

When the isocyanate crosslinking agent having a relatively high polarity is used as a crosslinking agent in a specified ratio, at least the higher molecular weight acrylic copolymer B has a hydroxyl group as a polar group, and a lower molecular weight acrylic copolymer A is used. The glass transition temperature (TgA) is equal to or higher than the glass transition temperature (TgB) of the acrylic copolymer B. Thereby, the reaction between the lower molecular weight acrylic copolymer A and the isocyanate crosslinking agent is promoted. By reducing the molecular weight of the acrylic copolymer, stress relaxation is obtained, and embrittlement due to low molecular weight is prevented, irrespective of size, and prevention of occurrence of color spots (especially white spots) in the adhesive is achieved. With the improvement of durability.

The adhesive composition for a polarizing plate of the present invention is excellent in durability and prevention of color spots (especially white spots), and is therefore applicable to a large display panel of 19 inches or more (that is, a large display device). Applicable to small display panels (ie, small display devices) that are less than 19 inches (again, less than 10 inches). In other words, the adhesive composition for a polarizing plate of the present invention is used for manufacturing a large display surface. At the same time as the adhesive for the board, since the adhesive for a small display panel can be manufactured from the edge portion of the entire sheet, the yield is improved. Therefore, it is possible to manufacture the size of the adhesive in accordance with the demand, and there is no need to stock and store.

Further, the term "(meth)acrylic group in the present invention means an acryl group or a methacryl group; and the so-called (meth) acrylate means an acrylate or a methacrylate.

Hereinafter, each component will be described in detail.

(acrylic copolymer A)

The adhesive composition for a polarizing plate of the present invention contains at least one of an acrylic copolymer A containing a constituent unit derived from an alkyl (meth)acrylate and a carboxyl group-containing compound. The constituent unit of the monomer has a weight average molecular weight of 300,000 or more and 700,000 or less. The acrylic copolymer A is a copolymer obtained by copolymerizing at least an alkyl (meth) acrylate with a monomer having a carboxyl group, and may further copolymerize another monomer, and further contains a monomer derived from the monomer. The unit that constitutes the unit.

Examples of the (meth)acrylic acid alkyl ester constituting the acrylic copolymer A include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylic acid. Butyl ester, tert-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ortho(meth)acrylate Ester, isodecyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, and octadecyl (meth)acrylate. Among them, it is easy to adjust the cohesive force and adhesion force of the adhesive, and it is preferable to use an alkyl (meth) acrylate having an alkyl carbon number of 1 to 4, and an alkyl carbon number of 1 to 4. An alkyl acrylate is preferred, and n-butyl acrylate is particularly preferred.

The ratio of the constituent unit derived from the alkyl (meth)acrylate in the acrylic copolymer A is preferably 65.0 to 99.5 mass%, more preferably 65.0 to 94.5 mass%, and particularly preferably 75.0 to 90.0 mass%. The (meth)acrylic acid alkyl ester is contained as a main component constituting the copolymer, and if the content ratio is within the above range, the optimum elastic modulus can be adjusted, and it is advantageous from the viewpoint of ensuring durability and adhesion. .

A preferred aspect of the acrylic copolymer A in the present invention is that, in addition to containing an alkyl (meth)acrylate as a main component, a monomer further different from the alkyl (meth)acrylate participates in copolymerization, wherein The glass transition temperature of the homopolymer formed by the monomer is between the glass transition temperature of the polymer obtained by separately polymerizing the (meth)acrylic acid alkyl ester (the carbon number of the alkyl group is preferably 1 to 4). The absolute value of the temperature difference is 30 ° C or more and 90 ° C or less. In this way, the glass transition temperature is increased, that is, the polarity of the resin is increased to improve the reactivity with the isocyanate crosslinking agent, and the durability can be further improved.

Among them, a monomer having an absolute value of the temperature difference of the glass transition temperature of the formed homopolymer in the foregoing range is methyl acrylate, butyl acrylate, phenoxy acrylate, methacrylic acid. N-butyl ester is preferred. The particularly preferred acrylic copolymer A is a form in which n-butyl acrylate is copolymerized with methyl acrylate and/or tertiary butyl acrylate.

In addition to the alkyl (meth) acrylate as a main component, when a monomer other than the main component (preferably methyl acrylate or butyl acrylate) is contained, the constituent unit derived from the monomer is The proportion in the acrylic copolymer A is preferably 5 to 30% by mass, more preferably 5 to 20% by mass. When the content ratio is within this range, it is advantageous from the viewpoint of improving the reactivity with the isocyanate crosslinking agent.

The carboxyl group-containing monomer constituting the acrylic copolymer A is preferably a carboxyl group-containing (meth)acrylic monomer. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, and ω-carboxypolycaprolactone mono(meth)acrylate. Among them, acrylic acid is preferred in view of high reactivity with other monomers in the copolymerization reaction and reduction of unreacted monomers.

The proportion of the constituent unit derived from the monomer having a carboxyl group in the acrylic copolymer A is preferably 0.5 to 5% by mass, more preferably 0.5 to 3% by mass. When the content ratio of the monomer having a carboxyl group is within this range, it is advantageous from the viewpoint of ensuring the pot life and the degree of crosslinking of the resin can be appropriately adjusted.

The weight average molecular weight of the acrylic copolymer A is 300,000 or more and 700,000 or less. The weight average molecular weight is in this range, and the acrylic copolymer A is a resin having a relatively low molecular weight among a plurality of resins contained in the adhesive composition for a polarizing plate. Also, when acrylic copolymer A When the weight average molecular weight is less than 300,000 and becomes too small, peeling or the like is likely to occur, and durability (especially, durability when applied to a large size (for example, 19 Å or more) is low). On the other hand, when the weight average molecular weight of the acrylic copolymer A exceeds 700,000 and becomes too large, the molecular size is close to that of the acrylic copolymer B, and the stress relaxation effect by the combination with the acrylic copolymer A becomes small, and it is impossible to Inhibit the occurrence of color shifts (especially white spots). This situation occurs remarkably, especially when applied to large sizes (eg, above 19 inches).

The glass transition temperature (TgA) of the acrylic copolymer A is preferably in the range of -50 ° C to -30 ° C, more preferably in the range of -48 ° C to 40 ° C. When the TgA is -50 ° C or more, the modulus of elasticity can be adjusted, and the durability and (anti-) white spot property are excellent. Further, when the TgA is -30 ° C or less, the viscosity is not extremely impaired, and the adhesion and the suitability are excellent.

The content of the acrylic copolymer A in the adhesive composition for a polarizing plate can be appropriately selected within a range satisfying the content ratio A/B to be described later, and preferably, the total amount of the adhesive composition for the polarizing plate. The solid content is in the range of 50% by mass or more and 74% by mass or less, more preferably in the range of 54% by mass or more and 69% by mass or less. When the content of the acrylic copolymer A is within this range, flexibility is imparted to the adhesive, and occurrence of color spots (especially white spots) is suppressed by stress relaxation.

(acrylic copolymer B)

The adhesive composition for a polarizing plate of the present invention contains at least one of an acrylic copolymer B containing a constituent unit derived from an alkyl (meth)acrylate and a single derived from a carboxyl group. The constituent unit of the body and the constituent unit derived from the monomer having a hydroxyl group, and the weight average molecular weight is 1,000,000 or more and 2,000,000 or less. The acrylic copolymer B is a copolymer obtained by copolymerizing at least a (meth)acrylic acid alkyl ester, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer, and may further copolymerize other monomers, and further contain From the constituent units of the monomer.

Examples of the (meth)acrylic acid alkyl ester constituting the acrylic copolymer B include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylic acid. Butyl ester, butyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, (methyl) propyl 2-ethylhexyl acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, and (methyl) ) octadecyl acrylate and the like. Among them, from the viewpoint of easily adjusting the cohesive force and the adhesion force of the adhesive, it is preferable to use an alkyl (meth)acrylate having an alkyl carbon number of 1 to 8, and an alkyl carbon number of 1 to 8. An alkyl acrylate is preferred, and particularly preferably n-butyl acrylate, butyl acrylate, methyl acrylate or 2-ethylhexyl acrylate.

The proportion of the constituent unit derived from the alkyl (meth)acrylate in the acrylic copolymer B is preferably 93 to 99.4% by mass, more preferably 96 to 99.4% by mass. The (meth)acrylic acid alkyl ester is contained as a main component constituting the copolymer, and if the content ratio is within this range, it can be adjusted to an optimum elastic modulus, which is advantageous from the viewpoint of durability or adhesive properties.

The carboxyl group-containing monomer constituting the acrylic copolymer B is preferably a carboxyl group-containing (meth)acrylic monomer. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, and ω-carboxypolycaprolactone mono(meth)acrylate. Among them, acrylic acid is preferred in view of high reactivity with other monomers in the copolymerization reaction and reduction of unreacted monomers.

The proportion of the constituent unit derived from the monomer having a carboxyl group in the acrylic copolymer B is preferably 0.5 to 5% by mass, more preferably 0.5 to 3% by mass. When the content ratio of the monomer having a carboxyl group is within this range, it is advantageous from the viewpoint of ensuring the pot life and appropriately adjusting the degree of crosslinking of the resin.

The hydroxyl group-containing monomer constituting the acrylic copolymer B is preferably a hydroxyl group-containing (meth)acrylic monomer, and more preferably a hydroxyl group-containing (meth)acrylate. As the monomer having a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, or (meth)acrylic acid 4- Hydroxybutyl ester, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-(meth)acrylate Trimethyl-3-hydroxypentyl ester, 2-ethyl-3-hydroxyhexyl (meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly (ethylene glycol-propylene glycol) mono(meth)acrylate or the like.

Among them, the polymerization reactivity is high, and the crosslinking reactivity in the case where the obtained copolymer is contained in the composition is excellent, and the hydroxyalkyl (meth) acrylate is preferable, and the carbon number of the alkyl moiety is 1 ~4 The hydroxyalkyl (meth) acrylate is more preferred, and further suitable are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate.

The proportion of the constituent unit derived from the monomer having a hydroxyl group in the acrylic copolymer B is preferably 0.1 to 2.0% by mass, more preferably 0.1 to 1.0% by mass. When the content ratio of the monomer having a hydroxyl group is within this range, the reactivity with the isocyanate crosslinking agent can be ensured, and it is advantageous to maintain good durability.

The weight average molecular weight of the acrylic copolymer B is 1,000,000 or more and 2,000,000 or less. The weight average molecular weight is in this range, and the acrylic copolymer B is a resin having a relatively high molecular weight among a plurality of resins contained in the adhesive composition for a polarizing plate. In addition, when the weight average molecular weight of the acrylic copolymer B is less than 1,000,000 and becomes too small, peeling or the like is likely to occur, and durability (especially, durability when applied to a large size (for example, 19 Å or more) is low). When the weight average molecular weight of the acrylic copolymer B exceeds 2,000,000 and becomes too large, the stress relaxation effect by the acrylic copolymer A in combination is inferior. Therefore, it becomes difficult to follow the shrinkage, and cracking or peeling easily occurs in the adhesive, and the durability is deteriorated, and at the same time, it is impossible to suppress the color unevenness particularly when applied to a small size (for example, less than 10 inches) ( Especially the occurrence of white spots).

The glass transition temperature (TgB) of the acrylic copolymer B is preferably in the range of -50 ° C to 40 ° C, more preferably in the range of -50 ° C to -45 ° C. When the TgB is -50 ° C or more, the modulus of elasticity can be adjusted, and the durability and (anti-) white spot property are excellent. Further, when the TgB is -40 ° C or lower, the viscosity is not extremely impaired, and the adhesion and the suitability are excellent.

The content of the acrylic copolymer B in the adhesive composition for a polarizing plate can be appropriately selected within a range satisfying the content ratio A/B to be described later, and preferably, the total amount of the adhesive composition for the polarizing plate. The solid content is in the range of 17% by mass or more and 37% by mass or less, more preferably in the range of 21% by mass or more and 32% by mass or less. When the content of the acrylic copolymer B is within this range, the ratio of the high molecular weight component in the adhesive is maintained, and the durability is improved.

In the acrylic copolymer A and the acrylic copolymer B of the present invention, a (meth)acrylic acid alkyl ester or a carboxyl group-containing monomer constituting each copolymer is provided between the acrylic copolymer A and the acrylic copolymer B. They can be different from each other or they can be the same.

In the present invention, the glass transition temperature (TgA; ° C) of the acrylic copolymer A and the glass transition temperature (TgB; ° C) of the acrylic copolymer B satisfy the relationship of TgA ≧ TgB. When the TgA system is lower than TgB, in addition to the relatively small molecular weight, the reactivity with the isocyanate crosslinking agent is insufficient, and failure such as foaming or peeling easily occurs, and durability is poor. Among them, from the viewpoint of further improving the prevention effect and durability of the stain (especially white spots), the temperature difference (TgA-TgB; ° C) between TgA and TgB is preferably 1 ° C or more and 5 ° C or less. The range is preferably in the range of 1 ° C or more and 3 ° C or less.

In the present specification, the glass transition temperature (Tg) of the acrylic copolymer is the molar average glass transition temperature obtained by the following calculation. Tg ₁ , Tg ₂ , ..., and Tg _n in the following formula are the glass transition temperatures of the homopolymers of each of the component 1, the component 2, ..., and the component n, and are converted into absolute temperatures. Calculated by (°K). m ₁ , m ₂ , ..., and m _n are the molar fractions of the respective components.

[Formulation formula of glass transition temperature (Tg)]

In addition, the "glass transition temperature (Tg) of a homopolymer" is applied to the monomer glass transition temperature described in "The Mechanical Properties of Polymers" by L.E. Nielsen and Konogi.

Further, the ratio (MwA/MwB) of the weight average molecular weight (MwA) of the acrylic copolymer A to the weight average molecular weight (MwB) of the acrylic copolymer B is preferably 0.5 or less. When MwA/MwB is 0.5 or less, the effect of preventing stains (especially white spots) can be further enhanced. Among them, MwA/MwB is more preferably 0.35 or less for the same reason.

The content ratio of the acrylic copolymer A to the acrylic copolymer B (A/B), depending on the quality standard, is preferably in the range of 60/40 to 80/20. When the content ratio A/B is at least the lower limit ratio, the ratio of the acrylic copolymer A having a relatively small molecular weight is relatively large, and the effect of improving the stain resistance (especially white spots) due to stress and relaxation is high, and the acrylic system is high. Since the glass transition temperature of the copolymers A and B satisfies the relationship of TgA ≧ TgB, there is little doubt that the durability due to the large ratio of the acryl-based copolymer A is low. In addition, the content relaxation ratio A/B is equal to or less than the upper limit ratio, the stress relaxation effect due to the low molecular weight, and the durability maintenance effect by maintaining the relative amount of the high molecular weight acrylic copolymer B. The balance between the two is maintained.

Among them, as the content ratio A/B, for the same reason, it is more preferably in the range of 65/35 to 75/25.

In the above, the combination of the acrylic copolymer A and the acrylic copolymer B in the present invention is preferably in the following (1) first aspect to (3) third aspect. which is,

(1) The first aspect:

The acrylic copolymer A includes a constituent unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms, a constituent unit derived from (meth)acrylic acid, and a constituent unit derived from the characteristic monomer. And the temperature difference between the glass transition temperature of the homopolymer formed by the characteristic monomer and the glass transition temperature of the polymer obtained by separately polymerizing the alkyl (meth)acrylate having 1 to 4 carbon atoms The absolute value is 30° C. or more and 90° C. or less; the acrylic copolymer B contains a constituent unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms, and a constituent unit derived from (meth)acrylic acid. And a constituent unit derived from hydroxyalkyl (meth)acrylate.

(2) The second aspect:

The acrylic copolymer A contains a constituent unit derived from n-butyl acrylate, a constituent unit derived from a carboxyl group-containing (meth)acrylic monomer, and a methyl acrylate and/or a tertiary butyl acrylate. The acryl-based copolymer B contains a constituent unit derived from n-butyl acrylate, a constituent unit derived from a carboxyl group-containing (meth)acrylic monomer, and a hydroxyalkyl (meth) acrylate. Form the unit.

(3) The third aspect:

The acrylic copolymer A comprises a constituent unit derived from n-butyl acrylate, a constituent unit derived from (meth)acrylic acid, a constituent unit derived from methyl acrylate and/or a tertiary butyl acrylate, and an acrylic copolymer. The substance B includes a constituent unit derived from n-butyl acrylate, a constituent unit derived from (meth)acrylic acid, and a constituent unit derived from hydroxyalkyl (meth)acrylate.

The method for polymerizing the acrylic copolymer in the present invention is not particularly limited, and methods such as solution polymerization, emulsion polymerization, and suspension polymerization can be applied. Solution polymerization is preferred because the treatment step is simple and can be carried out in a short period of time.

In solution polymerization, generally, a specified organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are placed in a polymerization tank, and heated while stirring in a nitrogen stream or an organic solvent. The reaction was allowed to continue for several hours. The polymerization initiator is not particularly limited, and for example, an azo compound can be used.

The weight average molecular weight (Mw) of the acrylic copolymer can be adjusted to a desired molecular weight by adjusting the reaction temperature, time, amount of solvent, and type or amount of the catalyst.

In the present specification, the weight average molecular weight (Mw) of the acrylic copolymer is a value measured by the following method. That is, the measurement is performed in accordance with the following (1) to (3).

(1) The acrylic copolymer solution was applied onto a release sheet (release sheet), and dried at 100 ° C for 2 minutes to obtain a film-form acrylic copolymer.

(2) The film-form acrylic copolymer obtained in the above (1) was dissolved in tetrahydrofuran to have a solid content of 0.2% by mass.

(3) The weight average molecular weight (Mw) of the (meth)acrylic copolymer was measured by gel permeation chromatography (GPC) under the following conditions.

. GPC: HLC-8220 GPC [Dongcao (share) company system]

. Column: TSK-GEL GMHXL (using 4 tubes)

. Mobile phase solvent: tetrahydrofuran

. Standard sample: standard polystyrene

. Flow rate: 0.6ml/min

. Column temperature: 40 ° C

(isocyanate crosslinking agent)

The adhesive composition for a polarizing plate of the present invention contains at least one of isocyanate crosslinking agents. This crosslinking agent is a compound having a polarity, and when the composition contains such a crosslinking agent, the effect of the present invention (prevention of color spots (especially white spots) and durability improvement) will be more effective.

As the isocyanate crosslinking agent, a toluene diisocyanate compound is preferable. As the toluene diisocyanate-based compound, various isocyanate-derived toluene diisocyanate compounds such as a dimer or a trimer of an isocyanate or an adduct of an isocyanate and a trimethylolpropane polyol can be used.

As a toluene diisocyanate-based compound, a commercially available product which is commercially available can be used, and as a commercial product, "CORONATEL" (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd. may be used.

The content of the isocyanate-based crosslinking agent in the adhesive composition for a polarizing plate is set to be 20 parts by mass or less based on 100 parts by mass of the total amount of the acrylic copolymer. When the content of the isocyanate crosslinking agent exceeds 20 parts by mass, the cohesive force becomes excessive, and when exposed to high temperature and high humidity, with a polarizing plate (especially with cellulose triacetate (TAC) which is a protective sheet thereof) The subsequent nature is easily lowered, and the occurrence of peeling cannot be suppressed. The content of the isocyanate crosslinking agent is preferably in the range of 8 parts by mass or more and 20 parts by mass or less, more preferably in the range of 10 parts by mass or more and 15 parts by mass or less. When the content of the isocyanate-based crosslinking agent is 8 parts by mass or more, the cohesive force which exhibits a good inhibitory effect on the shrinkage stress of the polarizing plate after the adhesion of the adhesive layer is exhibited, and the occurrence of white spots is more effectively suppressed.

(epoxy resin crosslinker)

The adhesive composition for a polarizing plate of the present invention preferably contains the above-mentioned isocyanate crosslinking agent and an epoxy resin crosslinking agent. When the adhesive composition for a polarizing plate contains an epoxy resin-based crosslinking agent, the cohesive force is easily adjusted, and it can be suppressed even when exposed to high temperature and high humidity. Observed abnormality.

Examples of the epoxy resin crosslinking agent include 1,3-bis(N,N-diglycidylaminemethyl)cyclohexane, N,N,N',N'-tetraglycidyl. Toluene diamine and the like.

In addition, as an example of a commercially available product, a commercially available product can be used as the epoxy resin crosslinking agent, and "TETRAD-X" and "TETRAD-C" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd. can be used. It is appropriate.

The content of the epoxy resin crosslinking agent in the adhesive composition for a polarizing plate is preferably 0.001% by mass or more and 0.1% by mass or less based on the total amount of the acrylic copolymer A and the acrylic copolymer B. When the content of the epoxy resin crosslinking agent is within this range, the cohesive force of the adhesive layer can be adjusted, which is advantageous from the viewpoint of suppressing occurrence of peeling on durability (moisture resistance).

(decane coupling agent)

The adhesive composition for a polarizing plate of the present invention preferably contains a decane coupling agent. When the adhesive composition for a polarizing plate contains a decane coupling agent, a display device (for example, a liquid crystal display device) provided with a polarizing plate is still exposed between the adhesive layer and the polarizing plate or the liquid crystal element even when exposed to a high temperature and high humidity environment. It is not easy to peel off. The adhesive composition for a polarizing plate of the present invention is preferable from the viewpoint of exhibiting good adhesion of the smooth glass.

The decane coupling agent may, for example, be a decane compound containing a polymerizable unsaturated group such as vinyltrimethoxydecane, vinyltriethoxyphosphonium, or 3-methylpropenyloxypropyltrimethoxydecane. a decane-containing decane-based compound such as 3-mercaptopropyltrimethoxydecane, 3-mercaptopropyltriethoxydecane, and 3-mercaptopropyldimethoxymethylnonane; and 3-glycidoxypropane a decane compound having an epoxy structure such as propyltrimethoxydecane or 2-(3,4-epoxycyclohexane)ethyltrimethoxydecane; 3-aminopropyltrimethoxydecane, N-( 2-aminoethyl)-3-aminopropyltrimethoxydecane, and amine-containing decane compound such as N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane; - Trimethoxy propyl propyl) isocyanurate or the like. These may be used alone or in combination of two or more.

As the decane coupling agent, a commercially available product which is already on the market can be used, and as an example of a commercially available product, "KBM-403" (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. may be used.

The content of the decane coupling agent in the adhesive composition for a polarizing plate is preferably 0.01% by mass or more and 2.0% by mass or less based on 100 parts by mass of the total of the acrylic copolymer A and the acrylic copolymer B. . When the content of the decane coupling agent is within this range, the adhesion of the adhesive layer can be further enhanced.

In addition to the above components, the adhesive composition for a polarizing plate of the present invention may be appropriately blended with various additives such as ultraviolet absorbers, solvents, and the like.

<attached adhesive polarizer>

The adhesive-attached polarizing plate of the present invention comprises at least a polarizer sheet and an adhesive layer formed on the polarizer sheet by the application of the adhesive composition for a polarizing plate of the present invention.

As the polarizing plate, for example, a polyvinyl alcohol (PVA) film or the like is generally used. The polarizer sheet can be used, for example, as a structure held between protective sheets such as cellulose triacetate (TAC), for example, a polarizing plate having a three-layer structure (e.g., TAC/polar sheet/TAC).

The adhesive composition for a polarizing plate of the present invention is applied to at least one surface of a polarizing plate having a three-layer structure of, for example, TAC/polarized sheet/TAC, to provide an adhesive layer, thereby preparing an adhesive for attachment. Polarizer. In this case, the composition may be applied to the polarizing plate, but it is preferably applied to a protective sheet (release sheet) which is peeled off during use. The application of the adhesive composition for a polarizing plate can be suitably carried out by a coating method such as a dipping method, a coating method or an inkjet method using a liquid polarizing plate adhesive composition. Among them, the coating method is preferred.

Specifically, the adhesive composition for a polarizing plate of the present invention is applied onto a protective sheet (release sheet), dried, and an adhesive layer is formed on the protective sheet, and then the adhesive layer is transferred onto a polarizing plate. And hardening it, and the adhesive film attached with the adhesive was produced.

The adhesive composition to be applied to the protective sheet (release sheet) is preferably a hot air dryer. Drying is carried out at 70 to 120 ° C for 1 to 3 minutes.

Further, from the viewpoint of protecting the contact surface of the object to be bonded, it is preferable to provide a protective sheet (peeling sheet) for protecting the exposed surface in close contact with the exposed surface of the adhesive layer provided on the polarizing plate. In order to facilitate the peeling from the adhesive layer, a synthetic resin sheet such as polyester which has been subjected to release treatment with a release agent such as a fluorine resin, paraffin or fluorenone is suitably used as the protective sheet. When attached to a glass plate or the like of the display panel, the protective sheet is peeled off, and the exposed surface of the adhesive layer is adhered to a glass substrate or the like.

Further, a surface protective sheet for protecting the surface may be further provided on the surface (exposed surface) of the polarizing plate where the adhesive layer is not provided. A protective film or the like which is subsequently processed to one side of the PET film can be suitably used as a surface protective layer.

The layer thickness of the subsequent layer is not particularly limited, and the thickness after drying is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and still more preferably 15 μm or more and 30 μm or less.

The adhesive polarizer of the present invention can be applied even if the liquid crystal element to be stacked has a size of 19 Å (260 mm × 415 mm) or more. When the size of the liquid crystal element is 19 Å or more (260 mm × 415 mm) or more, the expansion and contraction of the polarizing plate due to the influence of heat or humidity become large. Therefore, in the case of the conventional adhesive polarizer, when the exposure to high temperature and high humidity is performed, the stress cannot be sufficiently suppressed, so that when the light source of a large display device (for example, a liquid crystal display device) is turned on, it cannot be suppressed. The occurrence of white spots around the border. On the other hand, in the adhesive-attached polarizer of the present invention, since the resin design of the copolymer and the type and amount of the crosslinking agent are optimized, the stress is suppressed even when exposed to high temperature and high humidity. It is also easy to use, and it is also applicable to liquid crystal elements of a size of 19 吋 wide (260 mm × 415 mm) or larger; even if it is applied to a small display device (liquid crystal display device) of less than 19 吋 (more preferably, less than 10 吋), Moderate stress relaxation can suppress the occurrence of white spots.

<display device>

The display device of the present invention is configured by providing a display panel for displaying an image and an attached adhesive polarizing plate of the present invention disposed on at least one side of the display panel.

As the display panel, a liquid crystal display panel in which a liquid crystal compound is sealed, an organic electroluminescence display panel, or the like can be exemplified.

As an example of the display device of the present invention, a liquid crystal display device having the following structure can be exemplified. The adhesive polarizer of the present invention is disposed on both sides of the liquid crystal display panel, so that the adhesive layer is in contact with the surface of the liquid crystal display panel (for example, the surface of the glass substrate), and the polarizing plate is passed through the adhesive layer. The structure of both sides of the liquid crystal display panel (polar plate/substrate layer/liquid crystal display panel/substrate layer/polar plate structure).

Hereinafter, an adhesive composition for a polarizing plate of the present invention, an adhesive polarizer and an image display device, and the like are disclosed.

<1> A binder composition for a polarizing plate comprising: a constituent unit derived from an alkyl (meth)acrylate; and a constituent unit derived from a monomer having a carboxyl group, and having a weight average molecular weight of 300,000 or more and 700,000 or less The acrylic copolymer A; a constituent unit derived from an alkyl (meth)acrylate, a constituent unit derived from a monomer having a carboxyl group, and a constituent unit derived from a monomer having a hydroxyl group, and the weight average molecular weight is An acrylic copolymer B having a content of 1,000,000 or more and 2,000,000 or less; and an isocyanate crosslinking agent in an amount of 20 parts by mass or less based on 100 parts by mass of the total amount of the acrylic copolymer A and the acrylic copolymer B; Further, the glass transition temperature (TgA) of the acrylic copolymer A is equal to or higher than the glass transition temperature (TgB) of the acrylic copolymer B.

<2> The adhesive composition for polarizing plates of the above <1>, wherein the acrylic copolymer B has a glass transition temperature (TgB) of -50 ° C or more and -40 ° C or less.

<3> The adhesive composition for polarizing plates according to <1> or <2> above, wherein the weight average molecular weight (MwA) of the acrylic copolymer A is relative to the weight average molecular weight of the acrylic copolymer B (MwB) The ratio (MwA/MwB) is 0.5 or less.

The adhesive composition for polarizing plates of any one of the above-mentioned <1> to <3>, the content ratio (A/B) of this acrylic copolymer A with respect to this acrylic copolymer B, According to the quality standard, it is 60/40~80/20.

The adhesive composition for polarizing plates of any one of the above-mentioned <1>- <4> which contains the alkyl group which has the alkyl group number of 1-4. a constituent unit of an alkyl acrylate, a constituent unit derived from (meth)acrylic acid, and a constituent unit derived from the characteristic monomer, and a glass transition temperature of the homopolymer formed by the characteristic monomer, and the alkyl carbon The absolute difference of the temperature difference between the glass transition temperatures of the polymer obtained by polymerizing the alkyl (meth)acrylate having a number of 1 to 4 is 30 ° C or more and 90 ° C or less; The acrylic copolymer B contains a constituent unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms, a constituent unit derived from (meth)acrylic acid, and a (meth)acrylic acid. a constituent unit of a hydroxyalkyl ester.

<6> An adhesive-attached polarizing plate comprising a polarizing plate and a composition of an adhesive for a polarizing plate according to any one of <1> to <5>, which is formed on a polarizer Then the agent layer.

<7> A display device comprising a display panel for displaying an image and an adhesive polarizer attached as described in <6> on at least one surface of the display panel.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention should not be construed as limited to Also, unless otherwise mentioned, "parts" are quality benchmarks.

(Manufacturing Example A1)

79.0 parts by mass of n-butyl acrylate (BA), 20.0 parts by mass of methyl acrylate (MA), and 1.0 part by mass of acrylic acid (AA) were placed in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooling tube. After 110 parts by mass of ethyl acetate (EAc) and 0.1 part by mass of azobisdimethylvaleronitrile (ABVN) were mixed, the inside of the reactor was replaced with nitrogen. Then, while stirring the obtained mixture, the mixture in the reactor was heated to 65 ° C and maintained for 8 hours to carry out a polymerization reaction. After the end of the polymerization reaction, the reaction mixture was diluted with ethyl acetate to adjust the solid content to 37.0% by mass. In this manner, a solution of the BA/MA/AA copolymer A1 (acrylic copolymer A) was obtained. With respect to the obtained BA/MA/AA copolymer A1, the measurement of the weight average molecular weight and the calculation of the glass transition temperature (Tg) were carried out by the method shown below. The results are shown in Table 1 below.

The weight average molecular weight is determined by gel permeation chromatography (GPC) using TSK-GEL GMHXL (styrene polymer filler manufactured by Tosoh Corp.) as a column, and then subjected to polymerization. Calculated by styrene conversion.

Tg is the molar average glass transition temperature calculated by the calculation formula of the glass transition temperature (Tg) already described.

(Manufacturing Examples A2 to A11)

In Production Example A1, the ratio of n-butyl acrylate (BA), methyl acrylate (MA), and acrylic acid (AA) used for the synthesis of BA/MA/AA copolymer A1 was generally changed as shown in Table 1 below. At the same time, as shown in the following Table 1, by adjusting the amount of the solvent or the amount of the catalyst to adjust the molecular weight, the solution of the BA/MA/AA copolymer A2 to A11 (acrylic acid) was obtained in the same manner as in Production Example A1. Copolymer A).

Further, in the same manner as in the copolymer A1 of Production Example A1, the measurement of Mw and the calculation of Tg were carried out. The results are shown in Table 1 below.

(Manufacturing Examples A12 to A14)

In Production Example A1, n-butyl acrylate (BA), methyl acrylate (MA), and acrylic acid (AA) for synthesis were changed to the constituent monomers shown in Table 2 below, and then synthesized. A solution (acrylic copolymer A) of the copolymers A12 to A14 was obtained in the same manner as in Production Example A1.

Further, in the same manner as in the copolymer A1 of Production Example A1, the measurement of Mw and the calculation of Tg were carried out. The results are shown in Table 2 below.

(Manufacturing Example B1)

In a reactor equipped with a thermometer, a stirrer, a nitrogen gas introduction tube, and a reflux cooling tube, 89.0 parts by mass of n-butyl acrylate (BA), 9.5 parts by mass of methyl acrylate (MA), and 1.0 part by mass of acrylic acid (AA) were placed. 0.5 parts by mass of 2-hydroxyethyl acrylate (2HEA), 90 parts by mass of ethyl acetate (EAc), and 0.03 parts by mass of azobisdimethylvaleronitrile (ABVN), and mixed, and then nitrogen was carried out in the reactor. Replace. Then, while stirring the resulting mixture, the mixture in the reactor is raised. The polymerization was carried out by heating to 65 ° C for 8 hours. After the end of the polymerization reaction, the reaction mixture was diluted with ethyl acetate to adjust the solid content to 17.0% by mass. In this manner, a solution of BA/MA/AA/2HEA copolymer B1 (acrylic copolymer B) was obtained.

Further, in the copolymer B1, the measurement of Mw and the calculation of Tg were carried out in the same manner as in the copolymer A1 of Production Example A1. The results are shown in Table 1 below.

(Manufacturing examples B2 to B5, B7 to B9)

In Production Example B1, n-butyl acrylate (BA), methyl acrylate (MA) acrylic acid (AA), and 2-hydroxyethyl acrylate (2HEA) for synthesizing BA/MA/AA/2HEA copolymer B1. The ratio is generally changed as shown in the following Table 1. At the same time, as shown in the following Table 1, the molecular weight is adjusted by adjusting the amount of the solvent or the amount of the catalyst, and otherwise, the BA/MA is obtained in the same manner as in Production Example B1. /AA/2HEA Copolymer B2~B5, B7~B9 solution (acrylic copolymer B).

Further, in the same manner as in the copolymer B1 of Production Example B1, the measurement of Mw and the calculation of Tg were carried out for each copolymer. The results are shown in Table 1 below.

(Manufacturing example B6)

In Production Example B1, the ratio of n-butyl acrylate (BA), acrylic acid (AA), and 2-hydroxyethyl acrylate (2HEA) used for the synthesis of BA/MA/AA/2HEA copolymer B1 is as follows: The modification is generally changed, and 9.5 parts of methyl acrylate (MA) is substituted for 15 parts of 2-ethylhexyl acrylate (2EHA), and as shown in the following Table 1, by adjusting the amount of solvent or the amount of catalyst A solution of the BA/2EHA/AA/2HEA copolymer B6 (acrylic copolymer B) was obtained in the same manner as in Production Example B1 except that the molecular weight was adjusted.

Further, in the same manner as in the copolymer B1 of Production Example B1, the measurement of Mw and the calculation of Tg were carried out for each copolymer. The results are shown in Table 1 below.

(Manufacturing example B10 to B13)

In Production Example B1, n-butyl acrylate (BA), methyl acrylate (MA), acrylic acid (AA), and 2-hydroxyethyl acrylate (2HEA) for synthesis were changed to those shown in Table 2 below. The monomers were synthesized and synthesized, and a solution (acrylic copolymer B) of the copolymers B10 to B13 was obtained in the same manner as in Production Example B1.

Further, in the same manner as in the copolymer B1 of Production Example B1, the measurement of Mw and the calculation of Tg were carried out for each copolymer. The results are shown in Table 2 below.

(Example 1)

- Modulation of the composition of the adhesive -

189.2 parts by mass of a solution of the BA/MA/AA copolymer A1 obtained in the above-mentioned Production Example A1 of the acrylic copolymer A (solid content of BA/MA/AA copolymer: 70.0 parts by mass) as an acrylic copolymer 176.5 parts by mass of a solution of BA/MA/AA/2HEA copolymer B1 obtained in the above Production Example B1 of the material B (solid content of BA/MA/AA/2HEA copolymer: 30.0 parts by mass), CORONATE as an isocyanate compound L 20 parts by mass (isocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd., active ingredient: 15 parts by mass), and TETRAD-X as an epoxy resin compound: 0.02 parts by mass (epoxy of Mitsubishi Gas Chemical Co., Ltd.) Resin compound, active ingredient: 0.02 parts by mass), KBM-403 (a decane cross-linking agent manufactured by Shin-Etsu Chemical Co., Ltd., active ingredient: 0.1 part by mass) as a decane compound (SC agent), 0.1 part by mass, fully The mixture was stirred and mixed to obtain an adhesive composition.

At this time, the weight average molecular weight (MwA) of the BA/MA/AA copolymer A1 (acrylic copolymer A) and the weight average molecular weight (MwB) of the BA/MA/AA/2HEA copolymer (acrylic copolymer B) The molecular weight ratio (MwA/MwB) was 0.33; regarding Tg, the acrylic copolymer A was higher than the acrylic copolymer B.

- Production of optical film samples -

The adhesive composition was applied to the release agent-treated surface of the release film surface-treated with an anthrone-based release agent, and the amount of coating after drying was 25 g/cm ² . Then, it was dried at 100 ° C for 90 seconds using a hot air circulation dryer to form an adhesive layer on the release film. Next, a polarizing base film [Laminating a cellulose triacetate (TAC) film on both sides of a polarizing plate mainly composed of a polyvinyl alcohol (PVA) film, and having a laminated structure of a TAC film/PVA film/TAC film The back surface of about 190 μm was laminated on the surface of the adhesive layer, and then pressed by a pressure roll. After press-bonding, it was hardened for 10 days under the environmental conditions of 23 ° C and 65% RH to prepare a polarizing film having a laminated structure of a release film/adhesive layer/polarized base film as an optical film sample.

-Evaluation-

The following evaluation was performed using the polarizing film produced above. The evaluation results are shown in Table 1 below.

(1) Adhesion

The inclined ball adhesion value (inclined plate angle = 30°) was measured in accordance with the method specified in JIS Z 0237, and the stopped ball number was evaluated in accordance with the following evaluation criteria.

<Evaluation criteria>

A: The ball number is 7 or more.

B: The rolling ball number is 5~6.

C: The ball number is 3~4.

D: The ball number is less than 3.

(2) Durability

(2-1) 4.3 吋 (dry, wet)

A test piece (4.3 inches) of 54 mm × 96 mm (long side) was prepared, and the test piece was made to have a long side with respect to the absorption axis at 45° by the polarizing film obtained in the above-mentioned "production of an optical film sample". The cut was obtained, and then the release film was peeled off from the test piece. The surface of the adhesive agent layer exposed by peeling was adhered to one side of a 0.7 mm alkali-free glass plate (#1737, manufactured by Corning Co., Ltd.), whereby the test piece was superposed on the glass plate, and then laminated. The machine is attached to form a laminate. Next, the laminate was subjected to autoclave treatment (50 ° C, 5 kg/cm ² , 20 minutes), and allowed to stand under conditions of 23 ° C and 65% RH for 24 hours. Then, it was placed in a dry environment (80 ° C, 0% RH) under high temperature and low humidity conditions, and a wet environment (60 ° C, 90% RH) under high temperature and high humidity conditions for 500 hours. After the standing time, the state of foaming and peeling was visually observed, and evaluation was performed according to the following evaluation criteria.

<Evaluation criteria>

A: Foaming and peeling were not observed at all.

B: Foaming and peeling were hardly observed.

C: A little foaming and peeling were observed.

D: Obvious foaming and peeling were observed.

(2-2) 19吋 (dry, wet)

In the above-mentioned "(2-1) 4.3 吋 (dry, wet)", the size of the test piece obtained by cutting the polarizing film was changed to 240 mm × 427 mm (19 吋), and otherwise, according to "(2) The durability (4.3 吋: dry, wet) was evaluated in the same manner.

(3) stain

(3-1) White spot phenomenon (4.3吋)

Two polarizing film test pieces cut to the same size as the above-mentioned "(2-1)4.3吋 (dry, wet)" were prepared, and the polarizing axes were attached to the 0.7 mm alkali-free glass perpendicularly to each other. A sample was prepared on both sides of a plate (#1737, manufactured by Corning Co., Ltd.). Next, this sample was subjected to autoclave treatment (50 ° C, 5 kg/m ² , 20 minutes), and allowed to stand under conditions of 23 ° C and 50% RH for 24 hours. Then, it was allowed to stand in a dry environment (70 ° C, 0% RH) for 500 hours. After being placed, they were placed on the backlight of the liquid crystal screen at 23 ° C and 50% RH to visually observe the state of the white spots.

<Evaluation criteria>

A: It is completely impossible to determine white spots.

B: Almost no white spots can be determined.

C: A few white spots were determined.

D: A large white spot is determined.

(3-2) White spot phenomenon (7吋)

In the above-mentioned "(3-1) White spot phenomenon (4.3吋)", the size of the test piece obtained by cutting the polarizing film is changed to 88 mm × 156 mm (7.0 吋), and otherwise, according to "(3- 1) White spot phenomenon (4.3吋) is evaluated in the same way.

(3-3) White spot phenomenon (19吋)

In the above-mentioned "(3-1) White spot phenomenon (4.3吋)", the size of the test piece obtained by cutting the polarizing film is changed to 240 mm × 427 mm (19 吋), and otherwise, according to "(3- 1) White spot phenomenon (4.3吋) is evaluated in the same way.

(Examples 2 to 21, Comparative Examples 1 to 6)

The monomer composition or physical property (Tg, Mw) and weight average of the acrylic copolymer in Example 1. The amount of the component, the content ratio of the acrylic copolymers A and B, and the amount of the crosslinking agent are generally changed as shown in the following Tables 1 to 2, and the composition of the adhesive is prepared in the same manner as in the first embodiment. And making a polarizing film for evaluation.

As shown in Tables 1 to 2, in the examples, regardless of the dry environment and the wet environment, the occurrence of foaming or peeling can be suppressed, and good durability can be obtained. Moreover, regardless of the size, it is possible to effectively suppress the occurrence of white spots. Moreover, there is no bubble entrapment which is likely to occur at the time of bonding, and good adhesion is exhibited.

The entire disclosure of Japanese Patent Application No. 2012-128291 is incorporated herein by reference.

All documents, patent applications, and technical specifications described in the specification are used in the same manner as the specific documents and patent applications, and the technical specifications are used as the reference system and are individually described. As a reference.

Claims (7)

An adhesive composition for a polarizing plate comprising: an acrylic copolymer A comprising a constituent unit derived from an alkyl (meth)acrylate and a constituent unit derived from a monomer having a carboxyl group, and having a weight average molecular weight of 300,000 or more 700,000 or less; the acrylic copolymer B contains a constituent unit derived from an alkyl (meth)acrylate, a constituent unit derived from a monomer having a carboxyl group, and a constituent unit derived from a monomer having a hydroxyl group, and the weight average molecular weight is 1,000,000 or more and 2,000,000 or less; and the isocyanate-based crosslinking agent is contained in an amount of 20 parts by mass or less based on 100 parts by mass of the total amount of the acrylic copolymer A and the acrylic copolymer B; and the acrylic copolymer The glass transition temperature (TgA) of A is equal to or higher than the glass transition temperature (TgB) of the acrylic copolymer B. The adhesive composition for a polarizing plate according to the first aspect of the invention, wherein the acrylic copolymer B has a glass transition temperature (TgB) of from -50 ° C to 40 ° C. The adhesive composition for a polarizing plate according to claim 1 or 2, wherein the weight average molecular weight (MwA) of the acrylic copolymer A is relative to the weight average molecular weight (MwB) of the acrylic copolymer B. The ratio (MwA/MwB) is 0.5 or less. The adhesive composition for a polarizing plate according to claim 1 or 2, wherein the content ratio (A/B) of the acrylic copolymer A to the acrylic copolymer B is 60/by mass. 40~80/20. The adhesive composition for a polarizing plate according to claim 1 or 2, wherein the acrylic copolymer A comprises a composition of an alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms. a unit, a constituent unit derived from (meth)acrylic acid, and a constituent unit derived from the characteristic monomer, and a glass transition temperature of the homopolymer formed by the characteristic monomer, and a carbon number of the alkyl group of 1 to 4 The absolute difference of the temperature difference between the glass transition temperatures of the polymers obtained by polymerizing the alkyl (meth)acrylates is from 30 ° C to 90 ° C. The acrylic copolymer B contains from the alkyl carbon number of 1~. A constituent unit of 8 (meth)acrylic acid alkyl ester, a constituent unit derived from (meth)acrylic acid, and a constituent unit derived from hydroxyalkyl (meth)acrylate. An adhesive with an adhesive, comprising a polarizer, and by the scope of the patent application The polarizing plate according to any one of items 1 to 5, which is an adhesive layer formed on the polarizer sheet, with an adhesive composition. A display device comprising a display panel for displaying an image and an adhesive polarizer attached to at least one side of the display panel as set forth in claim 6 of the patent application.