JP2011178903A - Adhesive composition, optical film, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition which has a low viscosity, thereby giving excellent coating performance even if a coating solution has a high concentration of the solid content, gives a long pot life to coating solution, has excellent coating workability, and further is excellent in durability and suppression of generation of void, and to provide an optical film and a liquid crystal display device using the optical film. <P>SOLUTION: The adhesive composition includes an acrylic copolymer (A) containing a specific amount of a carboxy group-containing monomer as a copolymer component and having a weight-average molecular weight of 400,000 or more and less than 900,000, and an acrylic copolymer (B) containing a specific amount of a carboxy group-containing monomer and a hydroxy group containing monomer as a copolymer component and having a weight-average molecular weight of 400,000 or more and less than 900,000, and an isocyanate compound (C) which is added in an amount 5 pts.wt. or more and 30 pts.wt. or less, based on 100 pts.wt. of the mixture of the acrylic copolymer (A) and acrylic copolymer (B). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive composition, an optical film, and a liquid crystal display device using the optical film. More specifically, the present invention can be applied with a coating solution having a high solid content concentration, and is excellent in durability and suppression of occurrence of white spots, an optical film, and a liquid crystal using the optical film The present invention relates to a display device.

A liquid crystal display device usually comprises a liquid crystal cell in which a liquid crystal component oriented in a predetermined direction is sandwiched between two supporting substrates such as glass, and an optical film such as a polarizing film, a retardation film, and a brightness enhancement film. Has been. In many cases, an adhesive is used for laminating optical films and for attaching an optical film to a liquid crystal cell.

Liquid crystal display devices are widely used as display devices for personal computers, televisions, car navigation systems, and the like, and some of these applications have extremely severe use conditions such as high temperature and high humidity. Optical films tend to shrink and expand under high temperature and high humidity environments. Therefore, if the optical film is attached to a liquid crystal cell, etc., it is easy to foam or peel off when placed in a high temperature or high humidity environment, and the adhesive used for the optical film is foamed even in a high temperature and high humidity environment. It is required to be excellent in durability without causing peeling.

As pressure-sensitive adhesives satisfying such durability, pressure-sensitive adhesives using an acrylic copolymer having a high weight average molecular weight of, for example, 1 million or more (Patent Documents 1 and 2) have been proposed. These pressure-sensitive adhesives have high cohesive strength and good durability, but the viscosity of the acrylic copolymer is high, and the viscosity is such that it can be diluted with a large amount of solvent during coating. It was necessary to make a solution. In recent years, there has been a demand for a reduction in the amount of solvent used due to the trend of reducing waste solvent against the backdrop of intensifying cost competition and increasing interest in the environment. The pressure-sensitive adhesive using an acrylic copolymer having a weight average molecular weight of 1 million or more is coated with a coating solution whose solid content concentration is adjusted to about 10 to 15%. If the coating is applied as it is with high solids differentiation to a solid content concentration of about 30%, problems arise in workability during coating, and the coated surface becomes rough and a uniform coating film cannot be obtained. Also, if the weight average molecular weight of the acrylic copolymer is lowered, coating can be performed at a high solid content concentration, but simply reducing the weight average molecular weight results in low cohesive strength of the adhesive and durability. Problems arise. Furthermore, when the solid content concentration of the coating solution is increased, there is a problem that the pot life (pot life) of the coating solution is shortened and the coating workability is lowered.

Since the optical film has large dimensional changes such as shrinkage and expansion under high temperature and high humidity environment, the stress generated by the dimensional change cannot be relaxed by the adhesive layer, and the residual stress of the optical film is not uniform. Become. As a result, a phenomenon called “white spot” in which light leaks from the peripheral portion of the liquid crystal display device and turns white is also a problem.

JP 2009-167386 A JP 2005-298723 A

  The present invention has good coating properties because of its low viscosity even in a coating solution with a high solid content concentration, has a sufficiently long pot life of the coating solution and is excellent in coating workability. An object of the present invention is to provide a pressure-sensitive adhesive composition, an optical film, and a liquid crystal display device using the optical film, which are excellent in suppressing generation.

(1) Acrylic copolymer (A) having a weight average molecular weight of 400,000 or more and less than 900,000 containing 1% by weight or more and 4% by weight or less of a carboxyl group-containing monomer as a copolymer component;
The weight average molecular weight containing 0.1 to 4% by weight of a carboxyl group-containing monomer and 0.05 to 5% by weight of a hydroxyl group-containing monomer as a copolymer component is 400,000 to less than 900,000 Acrylic copolymer (B) of
Isocyanate compound (C) to be added in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B);
A pressure-sensitive adhesive composition comprising:

(2) The pressure-sensitive adhesive composition according to the above (1), wherein the acrylic copolymer (A) and the acrylic copolymer (B) are contained in a weight ratio of 50/50 or more and 99/1 or less. object.
(3) the difference between the solubility parameter (SP _B) of the solubility parameter of the acrylic copolymer (A) (SP _A) and the acrylic copolymer (B), -0.5 least 0. The pressure-sensitive adhesive composition according to the above (1) or (2), which is 5 or less.
(4) The relationship of the glass transition point and (Tg _B) of the glass transition point of the acrylic copolymer (A) (Tg _A) and the acrylic copolymer (B) satisfies _Tg A <Tg _B The pressure-sensitive adhesive composition according to any one of (1) to (3).

(5) The pressure-sensitive adhesive composition according to any one of (1) to (4), further comprising an epoxy compound or an aziridine compound.
(6) The epoxy compound or the aziridine compound is 0.005 parts by weight or more and 0.05 parts by weight or less with respect to 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B). The pressure-sensitive adhesive composition according to (5), which is added.
(7) An optical film having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of (1) to (6) above.
(8) A liquid crystal display device comprising the optical film according to (7).

  According to the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive composition can be applied with a coating solution having a high solid content, has a sufficient pot life, and is excellent in durability and suppression of occurrence of white spots. An optical film and a liquid crystal display device using the optical film can be provided. In addition, since the pressure-sensitive adhesive composition according to the present invention can be applied with a coating solution having a high solid content concentration, the cost performance can be reduced by reducing the amount of solvent used and saving energy by improving the drying efficiency during coating. It is possible to provide a pressure-sensitive adhesive composition that is excellent in environmental considerations.

It is sectional drawing of the optical film which concerns on this Embodiment. It is sectional drawing of the optical film which concerns on the modification of this Embodiment. It is sectional drawing of the liquid crystal display device which concerns on this Embodiment. It is sectional drawing of the liquid crystal display device which concerns on the modification of this Embodiment.

As a result of intensive studies, the inventors of the present invention contain a specific amount of a specific reactive functional group and a specific amount of a specific reactive functional group and an acrylic copolymer (A) that is a relaxation component. At the same time, unlike the acrylic copolymer (A), a pressure-sensitive adhesive composition in which a specific amount of the isocyanate compound (B) is added to a mixture with the acrylic copolymer (B), which is an elastic component, is used. The present inventors have found that a pressure-sensitive adhesive composition capable of achieving both durability and suppression of white spots can be provided even when the weight average molecular weight of the acrylic copolymer is lowered. Furthermore, even when the coating solution is adjusted to a high solid content concentration, the viscosity is low, the pot life of the coating solution is sufficiently long and excellent in coating workability, and the pressure-sensitive adhesive composition in consideration of cost and environment Found that can provide.

  Furthermore, since the inventor has high reactivity between the acrylic copolymer (B) and the isocyanate compound (C), first, chemical crosslinking between the acrylic copolymers (B) proceeds selectively. Then, the reaction between the isocyanate compound (C) and water in the environment, the chemical crosslinking between the acrylic copolymer (A) and the acrylic copolymer (B), the chemistry between the acrylic copolymers (A) It was thought that the crosslinking proceeded subsequently. The crosslinked structure between the acrylic copolymers (B) has a high cohesive force due to the properties of the acrylic copolymer (B), and the crosslinked structure between the acrylic copolymers (A) is The acrylic copolymer (A) has high flexibility due to the nature of the acrylic copolymer (A). The polymer produced by the reaction between the isocyanate compound (C) and water in the environment is hard, and not only restrains the movement of the acrylic copolymer and the crosslinked polymer composed of the copolymer by physical crosslinking, but also the acrylic polymer. It has been found that the cohesive force can be increased by the presence of a hard multimer in the entangled structure with a crosslinked polymer made of a copolymer.

  From the above findings, the present inventors have found that a highly cohesive portion due to chemical crosslinking between the acrylic copolymers (B), a hard multimeric portion generated by the reaction between the isocyanate compound (C) and water, and an acrylic Highly flexible portions due to chemical crosslinking between the copolymers (A) are dispersed non-uniformly, and further, chemical crosslinking between the acrylic copolymer (A) and the acrylic copolymer (B), And the adhesive composition which has the structure where the whole became intertwined by the physical bridge | crosslinking and the chemical bridge | crosslinking by the multimer produced | generated by reaction of an isocyanate compound (C) and water was discovered. The present inventor uses the pressure-sensitive adhesive composition having such a structure to achieve a high cohesive force, excellent flexibility, improved durability, and whiteness even with an acrylic copolymer having a low weight average molecular weight. It has been found that the suppression of noise can be realized at a high level.

Hereinafter, the embodiment will be described in detail.

[Embodiment]
The pressure-sensitive adhesive composition according to the embodiment of the present invention contains an acrylic copolymer having a weight average molecular weight of 400,000 or more and less than 900,000, which contains 1% by weight or more and 4% by weight or less of a carboxyl group-containing monomer as a copolymer component. An important average comprising the polymer (A), a carboxyl group-containing monomer of 0.1% by weight to 4% by weight and a hydroxyl group-containing monomer of 0.05% by weight to 5% by weight as a copolymer component It contains an acrylic copolymer (B) having a molecular weight of 400,000 or more and less than 900,000 and an isocyanate compound (C). The pressure-sensitive adhesive composition according to the embodiment includes a structure in which acrylic copolymers (A) that are relaxation components are cross-linked with an isocyanate compound (C), an acrylic copolymer (A), and an acrylic that is an elastic component. It contains a crosslinked polymer having a structure in which the system copolymer (B) is crosslinked with the isocyanate compound (C) and a structure in which the acrylic copolymers (B) are crosslinked with the isocyanate compound (C). Furthermore, the pressure-sensitive adhesive composition according to the embodiment comprises an isocyanate compound (C) that has not contributed to a crosslinking reaction with the acrylic copolymer (A) and the acrylic copolymer (B) and water in the environment. It has physical cross-linking that restrains the movement of the cross-linked polymer by a multimer generated by the reaction, and chemical cross-linking between the multimer and the cross-linked polymer. That is, in the pressure-sensitive adhesive composition according to the present embodiment, the reactive functional group of the acrylic copolymer (A) and the acrylic copolymer (B) and the isocyanate compound (C) undergo a crosslinking reaction, and isocyanate. The compound (C) includes a multimer produced by reacting the isocyanate group of the isocyanate compound (C) that has not contributed to the crosslinking reaction with water in the environment.

  In the embodiment, the acrylic copolymer (A) is a (meth) acrylic acid ester having, as a main component, an acrylic acid ester monomer and a methacrylic acid ester monomer as a copolymer component in the copolymer. And a copolymer obtained by copolymerizing a carboxyl group-containing monomer. Hereinafter, when a word including “acryl” and a word including “methacryl” are written together, it may be described as “(meth) acryl”. The acrylic copolymer (A) means a copolymer containing 80% by weight or more of (meth) acrylic acid ester, and a copolymer containing 90% by weight or more is preferable.

  The (meth) acrylic acid ester monomer of the acrylic copolymer (A) is not particularly limited as long as it has a (meth) acrylic acid ester structure. For example, methyl (meth) acrylate, ethyl (Meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meta ) Acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, carbon number of (meth) acrylic acid such as stearyl (meth) acrylate 1 to 18 linear or branched alkyl esters, and various derivatives thereof. May be used alone or two or more bodies. Of these, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like are preferably used.

  The constituent component in the acrylic copolymer (A) includes a carboxyl group-containing monomer for the purpose of reacting the acrylic copolymer (A) with the isocyanate compound (C). In addition, what is a carboxyl group-containing (meth) acrylic acid ester monomer is also contained as a copolymer component in the acrylic copolymer (A) when defining the acrylic copolymer (meta ) Counted as the amount of acrylate monomer.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamic acid, succinic acid monohydroxyethyl (meth) acrylate, and maleic acid. Acid monohydroxyethyl (meth) acrylate, fumarate monohydroxyethyl (meth) acrylate, phthalate monohydroxyethyl (meth) acrylate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate, (meth) acrylic acid dimer , Ω-carboxy-polycaprolactone mono (meth) acrylate, and the like can be used. Of these, acrylic acid, ω-carboxy-polycaprolactone mono (meth) acrylate and the like are preferably used.

  The proportion in which the carboxyl group-containing monomer is included as a copolymer component is included in the acrylic copolymer (A) for the purpose of increasing the cohesive force of the pressure-sensitive adhesive and improving the durability of the pressure-sensitive adhesive composition. On the other hand, it is 1% by weight or more, preferably 1.5% by weight or more. In addition, the ratio of the carboxyl group-containing monomer as a copolymer component has a sufficient pot life even for a coating solution having a high solid content concentration, and is intended to improve coating workability. The amount is 4% by weight or less, preferably 3% by weight or less, particularly preferably 2.5% by weight or less based on the acrylic copolymer (A).

  Examples of other monomers having a reactive functional group used in the acrylic copolymer (A) include a hydroxyl group-containing monomer, a glycidyl group-containing monomer, an amide group, and an N-substituted amide group-containing monomer. A monomer, a tertiary amino group-containing monomer, or the like can be appropriately used. These other polymerizable monomers may be used alone or in admixture of two or more. The use of a hydroxyl group-containing monomer can increase the cohesive strength of the acrylic copolymer (A). However, in order to maintain flexibility as a relaxation component of the acrylic copolymer (A), a hydroxyl group-containing monomer is used. It is preferable to use a very small amount of the monomer, such as less than 0.05 parts by weight, or not to use it.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 3-methyl- 3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-butyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (Meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly (ethylene glycol-propylene group) Call) mono (meth) acrylate, N- methylol acrylamide, allyl alcohol, can be used methallyl alcohol.

  Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, glycidyl (meth) allyl ether, 3,4 -Epoxy cyclohexyl (meth) allyl ether etc. can be used.

  Examples of the amide group and N-substituted amide group-containing monomer include acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, and N-ethoxy. Methyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-tert-butylacrylamide, N-octylacrylamide, diacetone acrylamide and the like can be used.

  As the tertiary amino group-containing monomer, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide and the like can be used.

  The acrylic copolymer (A) can contain a monomer other than the (meth) acrylic acid ester monomer as a copolymer component in a range not exceeding the definition of the acrylic copolymer (A). . As monomers other than the (meth) acrylic acid ester monomer, for example, saturated fatty acid vinyl ester, aromatic vinyl ester, vinyl cyanide monomer, maleic acid or fumaric acid diester can be used. Examples of the saturated fatty acid vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, “vinyl versatate” (trade name) and the like (preferably vinyl acetate); examples of the aromatic vinyl monomer include styrene, α -Methyl styrene, vinyl toluene, etc .; as vinyl cyanide monomers, for example, acrylonitrile, methacrylonitrile; as diesters of maleic acid or fumaric acid, for example, dimethyl maleate, di-N-butyl maleate, di- 2-ethylhexyl maleate, di-N-octyl maleate, dimethyl fumarate, di-N-butyl fumarate, di-2-ethylhexyl fumarate, di-N-octyl fumarate, etc. it can.

  The acrylic copolymer (B) is mainly composed of a (meth) acrylic acid ester monomer as a copolymer component in the copolymer, and a (meth) acrylic acid ester, a carboxyl group-containing monomer and a hydroxyl group. It is a copolymer obtained by copolymerizing the containing monomer, and is different from the acrylic copolymer (A). The acrylic copolymer (B) means a copolymer containing 80% by weight or more of (meth) acrylic acid ester, and a copolymer containing 90% by weight or more is preferable. The pressure-sensitive adhesive composition according to the embodiment uses a mixture of an acrylic copolymer (A) and an acrylic copolymer (B) as a resin component to adjust cohesive force and stress relaxation in a well-balanced manner. can do.

  The (meth) acrylic acid ester monomer of the acrylic copolymer (B) is not particularly limited as long as it has a (meth) acrylic acid ester structure, and the acrylic copolymer (A) A monomer similar to the exemplified (meth) acrylate monomer can be used. Of these, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, t-butyl (meth) acrylate, and the like are preferably used.

  The component in the acrylic copolymer (B) includes a carboxyl group-containing monomer and a hydroxyl group-containing monomer for the purpose of reacting the acrylic copolymer (B) with the isocyanate compound (C). . In addition, what is a carboxyl group-containing (meth) acrylic acid ester monomer and a hydroxyl group-containing (meth) acrylic acid ester monomer is also an acrylic copolymer (B) when defining an acrylic copolymer It is counted as the amount of (meth) acrylic acid ester monomer contained therein as a copolymer component. When the acrylic copolymer (B) contains a carboxyl group-containing monomer and a hydroxyl group-containing monomer, the acrylic copolymer (B) has a high cohesive force and easily adjusts the cohesive force and stress relaxation property of the resin component. An acrylic copolymer (B) that can be obtained can be realized.

  As the carboxyl group-containing monomer of the acrylic copolymer (B), the same monomers as the carboxyl group-containing monomer exemplified for the acrylic copolymer (A) can be used. Of these, acrylic acid or the like is preferably used.

  For the purpose of improving the durability of the pressure-sensitive adhesive composition by increasing the cohesive force of the pressure-sensitive adhesive, the proportion of the carboxyl group-containing monomer as the copolymer component of the acrylic copolymer (B) is as follows. The content is 0.1% by weight or more, preferably 0.3% by weight or more, particularly preferably 0.5% by weight or more based on the acrylic copolymer (B). Further, the proportion of the carboxyl group-containing monomer contained as a copolymer component of the acrylic copolymer (B) has a sufficient pot life even in a coating solution having a high solid content concentration. For the purpose of improving workability, the amount is 4% by weight or less, preferably 3% by weight or less, particularly preferably 2% by weight or less based on the acrylic copolymer (B).

  As the hydroxyl group-containing monomer of the acrylic copolymer (B), the same monomers as the hydroxyl group-containing monomer exemplified for the acrylic copolymer (A) can be used. Of these, 2-hydroxyethyl (meth) acrylate and the like are preferably used.

  The proportion of the hydroxyl group-containing monomer contained in the acrylic copolymer (B) as a copolymer component is 0.05 with respect to the acrylic copolymer (B) for the purpose of suppressing white spots. % By weight or more, preferably 0.1% by weight or more, more preferably 0.3% by weight or more. Further, the proportion of the hydroxyl group-containing monomer as a copolymer component of the acrylic copolymer (B) is 5% by weight or less, preferably for the purpose of suppressing the occurrence of peeling in the durability test. It is 3% by weight or less, particularly preferably 1% by weight or less.

  The copolymer component other than the (meth) acrylic acid ester monomer, carboxyl group-containing monomer, and hydroxyl group-containing monomer of the acrylic copolymer (B) is a monomer having a reactive functional group. A copolymer component similar to the copolymer component exemplified for the acrylic copolymer (A) can be used as a monomer other than the polymer and the (meth) acrylate monomer.

  The weight average molecular weight (Mw) of the acrylic copolymer (A) is 400,000 or more, preferably 500,000 or more for the purpose of giving sufficient cohesive force to the pressure-sensitive adhesive composition and suppressing the generation of bubbles. Particularly preferably, it is 600,000 or more. The acrylic copolymer (B) has a weight average molecular weight (Mw) of 400,000 or more, preferably 500,000 or more, particularly preferably 600,000 for the purpose of giving a sufficient cohesive force to the pressure-sensitive adhesive composition. That's it. Furthermore, the weight average molecular weight (Mw) of the acrylic copolymer (A) and the acrylic copolymer (B) is 90 for the purpose of ensuring coating workability with a coating solution having a high solid content concentration. Less than 10,000, preferably less than 850,000, particularly preferably less than 750,000.

The weight average molecular weight (Mw) of the acrylic copolymer (A) and the acrylic copolymer (B) is a value measured by the following method.
(Measurement method of weight average molecular weight (Mw))
It measures according to following (1)-(3).
(1) An acrylic copolymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The film-like acrylic copolymer obtained in (1) is dissolved in tetrahydrofuran so that the solid content is 0.2%.
(3) Under the following conditions, the weight average molecular weight (Mw) of the acrylic copolymer is measured using gel permeation chromatography (GPC).
(conditions)
GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
Column: 4 TSK-GEL GMHXL used Mobile phase solvent: Tetrahydrofuran Flow rate: 0.6 ml / min Column temperature: 40 ° C

The glass transition temperature (Tg _A ) of the acrylic copolymer (A) is preferably −80 ° C. or more for the purpose of giving sufficient cohesive force to the pressure-sensitive adhesive composition and exhibiting sufficient durability. Preferably, it is set to −60 ° C. or higher. In addition, the glass transition temperature (Tg _A ) of the acrylic copolymer (A) is used for the purpose of exhibiting sufficient adhesion to the support substrate in the pressure-sensitive adhesive composition and exhibiting durability that does not cause peeling. The temperature is preferably −20 ° C. or lower, more preferably −40 ° C. or lower.

On the other hand, it is preferable that the glass transition temperature (Tg _B ) of the acrylic copolymer ( _B ) is higher than the glass transition temperature of the acrylic copolymer (A), that is, satisfy the relationship of Tg _A <Tg _B. . If the Tg _B of Tg _A and an acrylic copolymer of acrylic copolymer (A) (B) is in the above relationship, the acrylic copolymer (B) is an acrylic copolymer (A) above Since it has a cohesive force, it is possible to easily balance the cohesive force of the resin component and the stress relaxation property. More specifically, the glass transition temperature of the acrylic copolymer (B) is preferably −60 ° C. or more for the purpose of giving the adhesive composition sufficient cohesive force and exhibiting sufficient durability. Is -50 ° C or higher. The glass transition temperature of the acrylic copolymer (B) is 0 ° C. or less for the purpose of exhibiting sufficient adhesiveness to the support substrate in the pressure-sensitive adhesive composition and exhibiting durability that does not cause peeling. The temperature is preferably -30 ° C or lower.

The glass transition temperature (Tg) of the acrylic copolymer (A) and the acrylic copolymer (B) is a value obtained by converting the temperature (K) obtained by the calculation of the following formula 1 into (° C.).
Formula 1 1 / Tg = M1 / Tg ₁ + M2 / Tg ₂ + M3 / Tg ₃ +... + Mn / Tg _n
In the formula, Tg ₁ , Tg ₂ , Tg ₃ ..., And Tg _n represent the glass transition temperatures (K) of the homopolymers of Component 1, Component 2, Component 3,. Moreover, in formula, M1, M2, M3 ... and Mn show the mole fraction of various components.

  The polymerization method of the acrylic copolymer (A) and the acrylic copolymer (B) used in the present embodiment is not particularly limited, and may be a method such as solution polymerization, emulsion polymerization, suspension polymerization. It can be polymerized. It should be noted that when the pressure-sensitive adhesive composition according to the embodiment is produced using a mixture of copolymers obtained by polymerization, it can be polymerized by solution polymerization because the treatment process is relatively simple and can be performed in a short time. preferable.

  In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, and stirred in a nitrogen stream or at the reflux temperature of the organic solvent. However, a method such as heating reaction for several hours can be used. In this case, at least a part of the organic solvent, the monomer and / or the polymerization initiator may be sequentially added. The weight average molecular weight of the acrylic copolymer (A) and the acrylic copolymer (B) is set to a desired molecular weight by adjusting the reaction temperature, time, amount of solvent, type and amount of the catalyst. Can do.

  Examples of the organic solvent used at the time of polymerization include aromatics such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Hydrocarbons; for example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, turpentine oil; , Ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate and the like; for example, acetone, methyl ethyl ketone, methyl-i- Such as butyl ketone, isophorone, cyclohexanone, methylcyclohexanone Tons; for example, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; for example, methyl alcohol, ethyl alcohol, n-propyl And alcohols such as alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol. These organic solvents can be used alone or in admixture of two or more.

  Of these organic solvents used in the polymerization, esters and ketones are preferably used for the polymerization of the acrylic copolymer, from the viewpoint of the solubility of the acrylic copolymer and the ease of the polymerization reaction. , Ethyl acetate, methyl ethyl ketone, acetone and the like are particularly preferable.

  As the polymerization initiator, it is possible to use organic peroxides, azo compounds and the like that can be used in ordinary solution polymerization. Examples of such organic peroxides include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, and di-i-propyl peroxydicarbonate. , Di-2-ethylhexyl peroxydicarbonate, t-butyl peroxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4- Di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) ) Propane, 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) butane, , 2-bis (4,4-di-t-octylperoxycyclohexyl) butane, and examples of the azo compound include 2,2′-azobis-i-butyronitrile and 2,2′-azobis-2. , 4-dimethylvaleronitrile, 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, and the like.

These polymerization initiators may be used alone or in combination of two or more, but the total content is about 0.005 to 2 parts by weight with respect to 100 parts by weight of the total monomers. It is more preferable that it is about 0.02 to 1 part by weight.

  Further, in the production of the acrylic copolymer according to the present embodiment, it is normal not to use a chain transfer agent, but it should be used as necessary within the range that does not impair the object and effect of the present invention. Is possible. Examples of such chain transfer agents include cyanoacetic acid; alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid; alkyl esters having 1 to 8 carbon atoms of bromoacetic acid; anthracene, phenanthrene, fluorene, 9 Aromatic compounds such as -phenylfluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene; benzoquinone, 2, 3, 5, Benzoquinone derivatives such as 6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloro Methane, tribromomethane, 3-chloro-1-p Halogenated hydrocarbons such as pens; Aldehydes such as chloral and fulleraldehyde: Alkyl mercaptans having 1 to 18 carbon atoms; Aromatic mercaptans such as thiophenol and toluene mercaptan; And alkyl esters of 1 to 12 carbons; terpenes such as vinylene and terpinolene; and the like.

  The polymerization temperature is generally about 30 to 180 ° C, preferably 40 to 150 ° C, more preferably 50 to 90 ° C. When an unreacted monomer is contained in a polymer obtained by a solution polymerization method or the like, it can be purified by a reprecipitation method using methanol or the like in order to remove the monomer.

  The pressure-sensitive adhesive composition according to the embodiment comprises 5 parts by weight or more and 30 parts by weight or less of an isocyanate compound with respect to 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B). (C) is contained.

  Examples of the isocyanate compound (C) include aromatic isocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate; for example, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated products of the aromatic isocyanate compound. It is possible to use isocyanate compounds derived from various isocyanates such as aliphatic or alicyclic isocyanates such as dimer or trimer of these isocyanates or adducts of these isocyanates and polyols such as trimethylolpropane. These can be used alone or in combination.

  Examples of the isocyanate compound (C) include “Coronate L”, “Coronate HX”, “Coronate HL-S”, “Coronate 2234” (manufactured by Nippon Polyurethane Industry Co., Ltd.), “Desmodur N3400” [Sumitomo Bayer Urethane ( "Duranate E-405-80T", "Duranate TSE-100" (manufactured by Asahi Kasei Corporation), "Takenate D-110N", "Takenate D-120N", "Takenate M-631N" [ Commercially available products such as “Mitsui Takeda Chemical Co., Ltd.” and the like can be suitably used.

  Among these, as the isocyanate compound (C), an isocyanate compound derived from an aromatic isocyanate is preferable from the viewpoint of durability and whiteness, and an isocyanate compound derived from tolylene diisocyanate is particularly preferable.

  The amount of the isocyanate compound (C) used relative to 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B) is 5 parts by weight or more for the purpose of suppressing white spots, The amount is preferably 10 parts by weight or more, particularly preferably 12 parts by weight or more. Moreover, the usage-amount of the isocyanate compound (C) with respect to 100 weight part of the mixture of an acrylic copolymer (A) and an acrylic copolymer (B) is an acrylic copolymer (A) and an isocyanate compound (C). In order to ensure the compatibility and to generate a sufficient tackiness as an adhesive, the amount is 30 parts by weight or less, preferably 20 parts by weight or less.

  Moreover, when the adhesive composition which concerns on embodiment forms the multimer by the isocyanate group of the isocyanate compound (C) which is not contributing to bridge | crosslinking with a copolymer reacting with the water in an environment. Conceivable. Reactivity between isocyanate groups and water is relatively high, and some isocyanate groups react with water in the environment to form multimers without adding an excessive amount of isocyanate groups relative to the reactive functional groups of the resin. The reaction between the acrylic copolymer (A) and the acrylic copolymer (B) for the purpose of suppressing white spots and forming many multimers in order to improve durability. More than 1 equivalent, preferably 1.2 equivalents or more, particularly preferably 1.5 equivalents or more of isocyanate groups are used per 1 equivalent of the total of functional groups.

  The pressure-sensitive adhesive composition according to the embodiment can be used in combination with a crosslinking agent other than the isocyanate compound (C). The crosslinking agent other than the isocyanate compound (C) is particularly limited as long as it reacts with the acrylic copolymer (A) and / or the acrylic copolymer (B) to form a crosslinked structure. Instead, an aziridine compound, an epoxy compound, a melamine formaldehyde condensate, a metal salt, a metal chelate compound and the like can be mentioned. These crosslinking agents other than the isocyanate compound (C) can be used alone or in combination of two or more. In the present embodiment, it is preferable to use an aziridine compound and / or an epoxy compound as a crosslinking agent other than the isocyanate compound (C).

  As the aziridine compound, a reaction product of an isocyanate compound and ethyleneimine can be used, and as the isocyanate compound, the compounds exemplified above can be used. A compound obtained by adding ethyleneimine to a polyvalent ester of a polyol such as trimethylolpropane or pentaerythritol and (meth) acrylic acid is also known and can be used.

  Examples of the aziridine compound include N, N′-hexamethylenebis (1-aziridinecarboxamide), methylenebis [N- (1-aziridinylcarbonyl))-4-aniline], tetramethylolmethane-tris (β- Aziridinylpropionate), trimethylolpropane-tris (β-aziridinylpropionate) and the like. Among these, for example, “TAZO”, “TAZM” [above Mutual Yakuhin Co., Ltd. Made by a trade name such as “Chemite PZ-33” (manufactured by Nippon Shokubai Co., Ltd.) can be suitably used.

  Examples of the epoxy compound include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1 , 6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneo Pentyl glycol diglycidyl ether , Trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1, 3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and the like can be used.

  Of the epoxy compounds, an epoxy compound containing three or more epoxy groups is preferable, among which tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1,3-bis (N, N-glycidylaminomethyl). ) The use of epoxy compounds such as cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine is more preferred, and 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N The use of N, N ′, N′-tetraglycidyl-m-xylylenediamine is particularly preferred. As such an epoxy compound, for example, those commercially available under trade names such as “TETRAD-C” and “TETRAD-X” (manufactured by Mitsubishi Gas Chemical Co., Inc.) can be suitably used.

  The amount of the aziridine compound and / or epoxy compound used relative to 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B) gives sufficient cohesive force to the pressure-sensitive adhesive composition, and is sufficient. For the purpose of exhibiting excellent durability, the amount is preferably 0.005 parts by weight or more, and particularly preferably 0.02 parts by weight or more. The amount of the aziridine compound and / or epoxy compound used for 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B) is sufficient to provide sufficient adhesion to the support substrate. 0.1 parts by weight or less is preferable, and 0.04 parts by weight or less is particularly preferable for the purpose of exerting the durability to the product so as not to cause peeling.

  The pressure-sensitive adhesive composition according to the present embodiment can further use a silane compound. Examples of such silane compounds include organic substituents such as mercapto group-containing silicone alkoxy oligomers, epoxy group-containing silicone alkoxy oligomers, amino group-containing silicone alkoxy oligomers, phenyl group-containing silicone alkoxy oligomers, and methyl group-containing silicone alkoxy oligomers. Silicone alkoxy oligomers; mercapto group-containing silane compounds such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane; for example, β- (3,4-epoxycyclohexyl) ethyltri Cycloaliphatic epoxy group-containing silane compounds such as methoxysilane and β- (3,4-epoxycyclohexyl) ethyltriethoxysilane; Epoxy group-containing silane compounds such as tri (glycidyl) silane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane; Propyl succinic acid (anhydride), 3-trimethoxysilylpropyl succinic acid (anhydride), 3-methyldimethoxysilylpropyl succinic acid (anhydride), methyldiethoxysilylpropyl succinic acid (anhydride), 1-carboxy- Carboxyl group-containing silane compounds such as 3-triethoxysilylpropyl succinic acid (anhydride); for example, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ- Aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ Amino group-containing silane compounds such as aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane; for example, γ-hydroxypropyltrimethoxysilane A hydroxyl group-containing silane compound such as γ-amidopropyltrimethoxysilane; an amide group-containing silane compound such as γ-isocyanatopropyltrimethoxysilane; an isocyanate group-containing silane compound such as γ-isocyanatopropyltrimethoxysilane; Isocyanurate skeleton-containing silane compounds such as methoxysilylpropyl) isocyanurate and tris (3-triethoxysilylpropyl) isocyanurate can be used. Use of a silane compound is preferable for improving durability.

  Moreover, the usage-amount of the silane compound with respect to 100 weight part of the mixture of an acrylic copolymer (A) and an acrylic copolymer (B) is set to 0. 0 for the purpose of improving the durability of an adhesive composition. The amount is from 01 to 3 parts by weight, preferably from 0.01 to 1 part by weight, particularly preferably from 0.02 to 0.5 part by weight.

Furthermore, the pressure-sensitive adhesive composition according to the present embodiment includes the acrylic copolymer (A), the acrylic copolymer (B), the isocyanate compound (C), and a crosslinking agent other than the isocyanate compound. In addition to the silane compound, various additives and the like can be appropriately blended in amounts that do not impair the effects exhibited by the pressure-sensitive adhesive composition according to the present embodiment. As various additives, various additives, solvents, weather resistance stabilizers, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers, and the like can be used.

  The range of the blending amount of the weather resistance stabilizer, tackifier, plasticizer, softener, dye, pigment, inorganic filler, etc. is a mixture of the acrylic copolymer (A) and the acrylic copolymer (B) 100. 30 parts by weight or less is preferable with respect to parts by weight, more preferably 20 parts by weight or less, and most preferably 10 parts by weight or less. By setting the blending amount within the range, the pressure-sensitive adhesive composition can maintain an appropriate balance of adhesive strength, wettability, heat resistance, paste transferability, and exhibit various physical properties. can get.

  In the pressure-sensitive adhesive composition according to the present embodiment, the reactive functional group of the acrylic copolymer (A) and the acrylic copolymer (B) and the isocyanate compound (C) form a cross-linked structure, and the cross-linking reaction It is thought that the isocyanate group that did not contribute to the reaction forms a multimer by reacting with water in the environment. The gel content after the formation of the crosslinked structure and the multimer is 60% by weight or more, preferably 70% by weight or more for the purpose of suppressing foaming in the durability evaluation. The gel content after the formation of the crosslinked structure and the multimer is 95% by weight or less, preferably 90% by weight or less for the purpose of suppressing the occurrence of peeling in durability evaluation.

The gel content can be measured by the following method.
(Measurement of gel content of adhesive composition)
It measures according to following (1)-(6).
(1) A solution of the pressure-sensitive adhesive composition was applied to a release sheet surface-treated with a silicone release agent so that the coating amount after drying was 25 g / m ^2, and hot air circulation type at 100 ° C. for 90 seconds. Dry with a drier to form a film-like pressure-sensitive adhesive layer.
(2) The formed pressure-sensitive adhesive layer is cured at 35 ° C. and 45% RH for 4 days.
(3) Apply about 0.25 g of the film-like pressure-sensitive adhesive layer obtained in (2) to a precisely weighed 250-mesh wire mesh (100 mm × 100 mm) and wrap so that the gel content does not leak. Thereafter, the weight is accurately measured with a precision balance to prepare a sample.
(4) The wire mesh is immersed in an ethyl acetate solution for 3 days.
(5) After immersion, the wire mesh is taken out, washed with a small amount of ethyl acetate, and dried at 120 ° C. for 24 hours. Thereafter, the weight is accurately measured with a precision balance.
(6) The gel content is calculated by the following formula.
Gel content (% by weight) = (C−A) / (B−A) × 100
However, A is the weight (g) of the wire mesh, B is the weight of the wire mesh (adhesive weight) (g), and C is the weight of the wire mesh (gel resin weight) (g) dried after immersion. is there.

The difference between the solubility parameter of the acrylic copolymer _(A) (SP A) and the solubility parameter (SP _B) of acrylic copolymer (B) (i.e., ΔSP ₌ SP A -SP _B) -0 It is preferably 0.5 or more and 0.5 or less, more preferably −0.4 or more and 0.4 or less. A solubility parameter difference (ΔSP) within the above range is preferable because the compatibility between the acrylic copolymer (A) and the acrylic copolymer (B) is extremely excellent.

Solubility parameters are calculated by the method of Fedor. The Fedor method is described, for example, in “SP Value Basics / Applications and Calculation Methods” (Hideki Yamamoto, published by Information Technology Corporation, 2005). In the Fedor method, the solubility parameter is calculated from the following equation 2.
Formula 2 Solubility parameter = √ (ΣEcoh / ΣV)
In Equation 2, Ecoh is the cohesive energy density and V is the molar molecular volume. Based on Ecoh and V determined for each atomic group, the solubility parameter can be calculated by obtaining the total ΣEcoh and ΣV of Ecoh and V in the repeating unit of the polymer. The solubility parameter of the copolymer is calculated by calculating the solubility parameter of each homopolymer of each constituent unit constituting the copolymer according to the above formula 2, and the mole value of each constituent unit is calculated for each of these SP values. Calculated by adding the product of the fractions.

  The mixing ratio of the acrylic copolymer (A) and the acrylic copolymer (B) is a weight ratio (acrylic copolymer (A) for the purpose of suppressing the occurrence of peeling in the durability test. ) / Weight of acrylic copolymer (B)) is 50/50 or more, preferably 70/30 or more, particularly preferably 80/20 or more. Moreover, the ratio which mixes an acrylic copolymer (A) and an acrylic copolymer (B) is a weight ratio (for the purpose of suppressing generation | occurrence | production of a foaming and white spot in a durability test ( 99/1 or less, preferably 95/5 or less, particularly preferably 90/10 or less in terms of weight of acrylic copolymer (A) / weight of acrylic copolymer (B).

  The pressure-sensitive adhesive composition according to the embodiment includes at least an acrylic copolymer (A) and an acrylic copolymer (B) that contain a reactive functional group, and an isocyanate compound that undergoes a crosslinking reaction with the reactive functional group ( And C). And in this mixing process, the equivalent of the isocyanate group of the isocyanate compound (C) is larger than the total equivalent of the reactive functional groups of the acrylic copolymer (A) and the acrylic copolymer (B). An amount of the isocyanate compound (C) is mixed into a mixture of the acrylic copolymer (A) and the acrylic copolymer (B). Specifically, a step of preparing an acrylic copolymer (A) and an acrylic copolymer (B) containing a reactive functional group, and an isocyanate compound (C) that undergoes a crosslinking reaction with the reactive functional group are prepared. And the step of mixing the prepared acrylic copolymer (A) and the acrylic copolymer (B) with the prepared isocyanate compound (C). And the process of preparing an isocyanate compound (C) is equivalent of the isocyanate group of an isocyanate compound (C) from the equivalent of the reactive functional group of an acrylic copolymer (A) and an acrylic copolymer (B). An isocyanate compound (C) is prepared in an amount that increases the amount of.

(Optical film)
FIG. 1 shows an outline of a cross section of an optical film according to the present embodiment, and FIG. 2 shows an outline of a cross section of an optical film according to a modification of the embodiment.

  The optical film which concerns on this Embodiment is an optical film which has the adhesive layer formed from the adhesive composition which concerns on embodiment. The specific manufacturing method is as follows. The pressure-sensitive adhesive composition according to the embodiment is formed on a release sheet as it is or diluted with an appropriate solvent such as ethyl acetate, toluene, methyl ethyl ketone, or the like to prepare a coating solution. Then, an adhesive layer is formed on the release sheet by applying and drying. Then, the pressure-sensitive adhesive layer formed on the release sheet can be transferred to an optical film and then cured.

Here, as the optical film, an optical film used for production of various display devices and the like can be used, and the type thereof is not particularly limited. For example, a polarizing film, a retardation film, a brightness enhancement film, or an antiglare film is used. Includes sheets. The optical film has two layers of optical materials, such as a laminate of a polarizing film and a retardation film, a laminate of a retardation film, and a laminate of a polarizing film and a brightness enhancement film or an antiglare sheet. It can also have the form which laminated | stacked above.

  For example, as shown in FIG. 1, the optical film according to the present embodiment is provided with a release sheet 4, an adhesive layer 3 provided on the release sheet 4 and made of the adhesive composition according to the present embodiment, and an adhesive. An optical film material 2 provided on the layer 3 and a protective film 1 provided on the optical film material 2 are provided. Moreover, as shown in FIG. 2, the optical film which concerns on the modification of this Embodiment is provided on the peeling sheet 4 and the peeling sheet 4, and the adhesion layer 3 which consists of an adhesive composition which concerns on this Embodiment. On the optical film material 2 provided on the adhesive layer 3, the adhesive layer 5 further provided on the optical film material 2, the optical film material 6 provided on the adhesive layer 5, and the optical film material 6 The protective film 1 provided is provided.

  As the release sheet, a synthetic resin sheet such as polyester subjected to release treatment with a release agent such as fluorine resin, paraffin wax, or silicone can be used.

The thickness of the pressure-sensitive adhesive layer formed on the release sheet is, for example, 1 μm or more and 100 μm or less, preferably 5 μm or more and 50 μm or less, more preferably 15 μm or more and 30 μm or less in terms of the thickness after drying.

The pressure-sensitive adhesive composition applied onto the release sheet can be dried with a hot air dryer under heating conditions of 70 ° C. or higher and 120 ° C. or lower and 1 minute or longer and 3 minutes or shorter.

  Furthermore, the coating solution comprising the pressure-sensitive adhesive composition according to the present embodiment has a property that the viscosity when the solid content is adjusted to 30% by weight by dilution with an appropriate solvent is 4000 mPa · s or less. It is. When the viscosity of the coating solution is 4000 mPa · s or less, the coating workability is good, which is preferable. Furthermore, in order to obtain a coating solution having a sufficient viscosity even with a coating solution having a high solid content concentration and having a low viscosity, the coating solution may contain a ketone solvent such as methyl ethyl ketone. preferable. A ketone solvent such as methyl ethyl ketone in the coating solution is added as a solvent used during polymerization or as a dilution solvent when preparing the coating solution.

(Liquid crystal display device)
FIG. 3 shows an outline of a cross section of the liquid crystal display device according to the present embodiment, and FIG. 4 shows an outline of a cross section of the liquid crystal display device according to a modification of the embodiment.

  The liquid crystal display device according to the present embodiment is a liquid crystal display device including the optical film according to the present embodiment. Moreover, a liquid crystal display device can be manufactured by sticking the optical film according to the present embodiment to one side or both sides of a liquid crystal cell via an adhesive layer of the optical film. For example, as shown in FIG. 3, in the liquid crystal display device, an optical film material 2 composed of a polarizing film 21 and a reflective layer 22 is attached to one surface of a liquid crystal cell 5 via an adhesive layer 3 according to the present embodiment. The polarizing film 21 is bonded to the other surface of the liquid crystal cell 5 via the adhesive layer 3 and manufactured. The liquid crystal cell 5 has a configuration in which the liquid crystal layer 50 is sandwiched between predetermined substrates 52. Furthermore, as shown in FIG. 4, another liquid crystal display device includes an optical film material 2 in which a polarizing film 21 and a reflective layer 22 are bonded via an adhesive layer 3 on one side and the other side of a liquid crystal cell. Each of these is manufactured by being bonded via the adhesive layer 3 according to the present embodiment. In the bonding, the polarizing film, the retardation film, and the like are performed so as to be in a predetermined arrangement position, and the arrangement position can be based on the conventional one. As the liquid crystal cell of the liquid crystal display device, for example, a liquid crystal cell of TN type, STN type, π type, or the like can be appropriately employed.

(Effect of embodiment)
Since the optical film provided with the adhesive composition which concerns on this Embodiment, and the adhesive layer which consists of this adhesive composition is provided with the structure mentioned above, an acrylic copolymer (A) and an acrylic copolymer (B ) Reactive functional groups and crosslinkers react with the chemical crosslinks, and isocyanate groups that do not contribute to the crosslink reaction of the isocyanate compound (C) react with moisture in the curing environment to form multimers. It is considered that the copolymer has a high cohesive force due to physical crosslinking that restricts the movement of the molecular chain of the copolymer, so the durability is good even when the weight average molecular weight of the acrylic copolymer is lowered. In addition, the physical cross-linking portion that restrains the movement of the molecular chain is considered to be excellent in stress relaxation because of its fluidity, and can have both durability and suppression of white spots at a high level.

  That is, in the pressure-sensitive adhesive composition according to the present embodiment, the isocyanate group of the isocyanate compound (C) is determined from the total equivalent weight of the reactive functional groups of the acrylic copolymer (A) and the acrylic copolymer (B). Since the isocyanate compound (B) is used in such an amount that the equivalent amount increases, not only the chemical crosslinking by the reaction between the reactive functional group of the acrylic copolymer (A) and the acrylic copolymer (B) and the crosslinking agent, Of the isocyanate compound (C) added to the acrylic copolymer (A) and the acrylic copolymer (B), it did not react with the acrylic copolymer (A) and the acrylic copolymer (B). A multimer derived from the isocyanate compound (C) having an isocyanate group is produced. As a result, the pressure-sensitive adhesive composition according to the present embodiment is a molecule generated by chemical cross-linking by the reaction between the reactive functional group of the acrylic copolymer (A) and the acrylic copolymer (B) and the cross-linking agent. A multimer of the isocyanate compound (C) is present in the chain entanglement structure. Therefore, in the pressure-sensitive adhesive composition according to the present embodiment, the multimer is unevenly dispersed in the entangled structure of the molecular chain generated by the chemical crosslinking by the reaction between the reactive functional group and the crosslinking agent. Even when an acrylic copolymer having a low weight average molecular weight is used while ensuring good transparency to visible light, durability and suppression of white spots can be achieved at a high level.

  Further, in the pressure-sensitive adhesive composition according to the present embodiment, the coating workability is good because the coating solution has a low viscosity and a sufficient pot life even at a high solid content concentration. It can be provided as a pressure-sensitive adhesive composition with consideration for cost performance and environmental aspects.

  Examples, comparative examples, and reference examples will be described below. In addition, preparation of the test piece used in the Example, the comparative example, and the reference example, and various test / measurement methods and evaluation methods are as follows.

(1) Measurement of solid content (non-volatile content) About 1 g of acrylic copolymer solution is weighed in a flat bottom plate made of aluminum, dried in an oven at 100 ° C. for 180 minutes, and the residue is weighed to calculate the remaining rate. , Solid content (nonvolatile content).

(2) Measurement of coating solution viscosity A coating solution of the pressure-sensitive adhesive composition adjusted to a solid content concentration of 30% by weight is 10 rpm with a BH viscometer (manufactured by Tokyo Keiki Co., Ltd.) at 25 ° C. The measurement was performed under the condition of rotation for 1 minute.

(3) Pot life evaluation test A coating solution of the pressure-sensitive adhesive composition adjusted to a solid content concentration of 30% by weight is stored at 23 ° C. and applied to the coating film formed by applying the pressure-sensitive adhesive composition solution. The storage time until uniform coating was confirmed without causing cloudiness or uneven coating was confirmed. The evaluation criteria are as follows. In addition, a coating composition is an adhesive composition so that the coating amount after drying may be 25 g / cm < ² > on the peeling film surface-treated with the silicone type release agent. Was applied and dried with a hot air circulation dryer at 100 ° C. for 90 seconds.

(Pot life evaluation criteria)
◎: 24 hours or more ○: 12 hours or more and less than 24 hours ×: Less than 12 hours

(4) Preparation of optical film for test A polarizing film having an adhesive layer was prepared using a polarizing film as an example of the optical film. A coating solution of the pressure-sensitive adhesive composition was applied on a release film surface-treated with a silicone release agent so that the coating amount after drying was 25 g / cm ² . Next, it was dried with a hot air circulation dryer at 100 ° C. for 90 seconds to form an adhesive layer. Subsequently, the pressure-sensitive adhesive layer surface is bonded to the back surface of a polarizing base film (a cellulose triacetate (TAC) film laminated on both sides of a polarizer mainly composed of a polyvinyl alcohol (PVA) film; about 190 μm), and then applied to a pressure nip roll. Crimped through. After pressure bonding, the film was cured at 35 ° C. and 45% RH for 4 days to obtain a polarizing film having an adhesive layer.
In Comparative Example 1, an optical film was prepared using a coating solution further diluted with ethyl acetate so that the coating solution viscosity was 3000 mPa · s.

(5) Evaluation of heat resistance and heat and humidity resistance The polarizing film prepared in “(4) Preparation of optical film for test” was cut to have a long side of 45 ° with respect to the absorption axis. Side) was applied to one side of a 0.7 mm Corning non-alkali glass plate “# 1737” using a laminator. Next, this sample was subjected to autoclaving (50 ° C., 5 kg / cm ² , 20 minutes), and allowed to stand at 23 ° C. and 50% RH for 24 hours to obtain a test sample. Test samples were prepared for each of the heat resistance evaluation and the heat and humidity resistance evaluation. Thereafter, the test sample for heat resistance evaluation was allowed to stand at a temperature of 105 ° C. for 500 hours, and the heat resistance was evaluated by visually observing the state of foaming and peeling. Moreover, the test sample for heat and moisture resistance evaluation was allowed to stand for 500 hours under the condition of 60 ° C. and 90% RH, and the heat and humidity resistance was evaluated by visually observing the peeling state. The evaluation criteria are as follows.

(Heat resistance evaluation criteria)
a) Foaming ◎: Foaming is not seen at all.
○: Foaming is hardly seen.
(Triangle | delta): Some foaming is seen a part.
X: Foaming is noticeable over the entire surface.

b) Peeling ◎: No peeling.
○: peeling is 0.3 mm or less.
X: Peeling is larger than 0.3 mm.

(Evaluation criteria for heat and humidity resistance)
a) Peeling ◎: No peeling.
○: peeling is 0.3 mm or less.
X: Peeling is larger than 0.3 mm.

(6) Evaluation test of white spot phenomenon 12 inch size obtained by cutting the polarizing film prepared in “(4) Preparation of optical film for test” so that the long side is 45 ° with respect to the absorption axis, that is, 140 mm Using a test piece of × 260 mm (long side), a polarizing film having an adhesive layer is pasted on both sides of a 0.7 mm Corning alkali-free glass plate “# 1737” so that the polarization axes thereof are orthogonal to each other. A test sample was prepared. Next, this sample was subjected to autoclaving (50 ° C., 5 kg / cm ² , 20 minutes), and left for 24 hours at 23 ° C. and 50% RH. Then, it was left to stand at 80 ° C. under dry conditions for 500 hours. After standing, a uniform light source was used under the conditions of 23 ° C. and 50% RH, and the white spots were visually inspected. The evaluation criteria are as follows.

(Evaluation criteria for white spots)
A: No white spots are observed.
○: Almost no white spots are observed.
X: White spots are large.

(Production of acrylic copolymer (A))
(Production Example 1)
25% by weight of a monomer solution consisting of 98 parts by weight of n-butyl acrylate (BA) and 2 parts by weight of acrylic acid (AA) in a reactor equipped with a thermometer, a stirrer, a sequential dropping device and a reflux condenser. Then, 55 parts by weight of ethyl acetate (EAc) was added and heated to raise the temperature in the system to the reflux temperature and left as it was for 20 minutes. Subsequently, a solution comprising 75% by weight of the remaining monomer mixture at reflux temperature, 40 parts by weight of ethyl acetate and 0.07 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile)) The reaction mixture was further reacted for 60 minutes and after completion of the reaction, the reaction mixture was diluted with 75 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 35.7% by weight. .

(Production Example 2)
In a reactor equipped with a thermometer, a stirrer, a sequential dropping device and a reflux condenser, a monomer solution consisting of 98.5 parts by weight of n-butyl acrylate (BA) and 1.5 parts by weight of acrylic acid (AA) Of these, 25% by weight and 40 parts by weight of ethyl acetate (EAc) were added and heated to raise the temperature in the system to the reflux temperature and left for 20 minutes. Next, a solution comprising 75% by weight of the remaining monomer mixture, 45 parts by weight of ethyl acetate, and 0.07 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile) at reflux temperature. The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 85 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 34.9% by weight. .

(Production Example 3)
In a reactor equipped with a thermometer, a stirrer, a sequential dropping device and a reflux condenser, 25% by weight of a monomer solution consisting of 99 parts by weight of n-butyl acrylate (BA) and 1 part by weight of acrylic acid (AA) Then, 65 parts by weight of ethyl acetate (EAc) was added and heated to raise the temperature in the system to the reflux temperature and left as it was for 20 minutes. Subsequently, a solution comprising 75% by weight of the remaining monomer mixture at reflux temperature, 40 parts by weight of ethyl acetate and 0.07 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile)) The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 65 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 35.2% by weight. .

(Production Example 4)
Production Example 1 except that 98 parts by weight of n-butyl acrylate (BA) was changed to 97 parts by weight of n-butyl acrylate (BA) and 2 parts by weight of acrylic acid (AA) was changed to 3 parts by weight of acrylic acid (AA). An acrylic copolymer was obtained in the same manner as in Example 1.

(Production Example 5)
25% by weight of a monomer solution consisting of 98 parts by weight of n-butyl acrylate (BA) and 2 parts by weight of acrylic acid (AA) in a reactor equipped with a thermometer, a stirrer, a sequential dropping device and a reflux condenser. Then, 40 parts by weight of ethyl acetate (EAc) was added and heated to raise the temperature in the system to the reflux temperature and left as it was for 20 minutes. Next, a solution comprising 75% by weight of the remaining monomer mixture, 65 parts by weight of ethyl acetate and 0.02 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile) at reflux temperature The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 65 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 34.8% by weight. .

(Production Example 6)
Production Example 1 except that 98 parts by weight of n-butyl acrylate (BA) was changed to 95 parts by weight of n-butyl acrylate (BA) and 2 parts by weight of acrylic acid (AA) was changed to 5 parts by weight of acrylic acid (AA). An acrylic copolymer was obtained in the same manner as in Example 1.

(Production Example 7)
In Production Example 1, 98 parts by weight of n-butyl acrylate (BA) was changed to 99.5 parts by weight of n-butyl acrylate (BA), and 2 parts by weight of acrylic acid (AA) was changed to 0.5 parts by weight of acrylic acid (AA). Except that, an acrylic copolymer was obtained in the same manner as in Production Example 1.

(Production of acrylic copolymer (B))
(Production Example 8)
In a reactor equipped with a thermometer, stirrer, sequential dropping device and reflux condenser, n-butyl acrylate (BA) 83.5 parts by weight, t-butyl acrylate (tBA) 15 parts by weight, acrylic acid (AA) 1 25 parts by weight of a monomer solution consisting of 0.5 parts by weight of 2-hydroxyethyl acrylate (2HEA) and 55 parts by weight of ethyl acetate (EAc) are added and heated, and the temperature inside the system is brought to the reflux temperature. Raised and left for 20 minutes. Subsequently, a solution comprising 75% by weight of the remaining monomer mixture at reflux temperature, 40 parts by weight of ethyl acetate and 0.07 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile)) The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 75 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 34.7% by weight. .

(Production Example 9)
In a reactor equipped with a thermometer, stirrer, sequential dropping device and reflux condenser, n-butyl acrylate (BA) 83.5 parts by weight, t-butyl acrylate (tBA) 15 parts by weight, acrylic acid (AA) 1 25 parts by weight of a monomer solution consisting of 0.5 parts by weight of 2-hydroxyethyl acrylate (2HEA) and 40 parts by weight of ethyl acetate (EAc) are added and heated, and the temperature inside the system is brought to the reflux temperature. Raised and left for 20 minutes. Next, a solution comprising 75% by weight of the remaining monomer mixture, 45 parts by weight of ethyl acetate, and 0.07 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile) at reflux temperature. The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 85 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 34.6% by weight. .

(Production Example 10)
In a reactor equipped with a thermometer, stirrer, sequential dropping device and reflux condenser, n-butyl acrylate (BA) 83.5 parts by weight, t-butyl acrylate (tBA) 15 parts by weight, acrylic acid (AA) 1 25 parts by weight of a monomer solution consisting of 0.5 parts by weight of 2-hydroxyethyl acrylate (2HEA) and 65 parts by weight of ethyl acetate (EAc) are added and heated. Raised and left for 20 minutes. Subsequently, a solution comprising 75% by weight of the remaining monomer mixture at reflux temperature, 40 parts by weight of ethyl acetate and 0.07 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile)) The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 65 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 34.8% by weight. .

(Production Example 11)
In Production Example 8, 83.5 parts by weight of n-butyl acrylate (BA) is 83.7 parts by weight of n-butyl acrylate (BA), and 0.5 part by weight of 2-hydroxyethyl acrylate (2HEA) is 2-hydroxyethyl acrylate. (2HEA) An acrylic copolymer was obtained in the same manner as in Production Example 8, except that the amount was changed to 0.3 parts by weight.

(Production Example 12)
In a reactor equipped with a thermometer, stirrer, sequential dropping device and reflux condenser, n-butyl acrylate (BA) 83.5 parts by weight, t-butyl acrylate (tBA) 15 parts by weight, acrylic acid (AA) 1 25 parts by weight of a monomer solution consisting of 0.5 parts by weight of 2-hydroxyethyl acrylate (2HEA) and 40 parts by weight of ethyl acetate (EAc) are added and heated, and the temperature inside the system is brought to the reflux temperature. Raised and left for 20 minutes. Next, a solution comprising 75% by weight of the remaining monomer mixture, 65 parts by weight of ethyl acetate and 0.02 parts by weight of ABNV (2,2′-azobis (2,4-dimethylvaleronitrile) at reflux temperature The reaction mixture was further reacted for 60 minutes, and after completion of the reaction, the reaction mixture was diluted with 65 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 34.7% by weight. .

Tables 1 and 2 show the copolymer composition, solid content, glass transition point (Tg), solubility parameter (SP value), and weight average molecular weight (Mw) of each example.

(Production of pressure-sensitive adhesive composition for optical film)
Example 1
As shown in Table 3, the acrylic copolymer (A) produced in Production Example 1 so that the blend ratio of the acrylic copolymer (A) and the acrylic copolymer (B) was 85:15. While mixing 238 parts by weight of the solution (however, 85 parts by weight as the active ingredient) and 43 parts by weight of the acrylic copolymer (B) solution produced in Production Example 8 (however, 15 parts by weight as the active ingredient) 18.7 parts by weight of Coronate L as isocyanate compound (C) in the mixture (polyisocyanate compound manufactured by Nippon Polyurethane Co., Ltd., 14 parts by weight of active ingredient, amount of isocyanate group relative to 1 equivalent total of reactive functional groups of acrylic copolymer (note that In Tables 3 to 5, described as “NCO / resin functional group”) 2.22 equivalents) and TETRAD-X as an epoxy compound (manufactured by Mitsubishi Gas Chemical Co., Inc., 100 active ingredients) %) 0.02 part by weight and 0.1 part by weight of 3-glycidoxypropyltrimethoxysilane as a silane compound (a silane compound manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-403, active ingredient 0.1 part by weight) Then, 80 parts by weight of methyl ethyl ketone was added as a diluent solvent, and the mixture was sufficiently stirred and mixed to obtain a coating solution of the pressure-sensitive adhesive composition according to Example 1 having a solid content concentration of 30% by weight.

(Other examples, comparative examples, and reference examples)
Instead of the blending composition in Example 1, the blending composition of each example shown in Tables 3 to 4 was adopted, and the solid content concentration was 30 in the same manner as in Example 1 except that the weight part of the diluent solvent was appropriately changed. A coating solution of a weight percent pressure-sensitive adhesive composition (that is, pressure-sensitive adhesive compositions according to Examples 2 to 7 and Comparative Examples 1 to 3) was prepared. Using the obtained coating solution of the pressure-sensitive adhesive composition, a test optical film was prepared by the above-described test optical film preparation method, and various measurements described above were performed. The results for each example are shown in Tables 3-5.

In addition, the symbol of each compound in Table 3-Table 4 is as follows, and the addition amount of each component is a weight part of an active ingredient.
Coronate L: Tolylene diisocyanate adduct of trimethylolpropane manufactured by Nippon Polyurethane, 75% by weight of active ingredient, isocyanate compound (C)
TETRAD-X: Epoxy compound manufactured by Mitsubishi Gas Chemical Co., Inc., trade name: TETRAD-X, chemical name: N, N, N ′, N′-tetraglycidyl-m-xylenediamine, active ingredient 100% by weight, epoxy compound KBM -403: Shin-Etsu Chemical Co., Ltd. silane compound, trade name: KBM-403, chemical name: 3-glycidoxypropyltrimethoxysilane, active ingredient 100 wt%, silane compound X-41-1053: Shin-Etsu Chemical Co., Ltd. Silane compound, trade name: X-41-1053, epoxy group-containing silicone alkoxy oligomer containing an epoxy group as an organic substituent as an organic substituent, 100% by weight of active ingredient, silane compound

  The pressure-sensitive adhesive compositions according to the embodiments and the examples have good coating properties even when the coating solution has a high solid content concentration, so that the coating property is good and the pot life of the coating solution is sufficiently long. Since the workability is excellent, it is possible to provide a pressure-sensitive adhesive composition in consideration of cost and environment. Furthermore, the optical film having the optical film pressure-sensitive adhesive according to the embodiment and the examples has good durability and suppresses white spots, and thus is used for display devices such as personal computers, televisions, and car navigation systems. It can be applied to optical films.

  As mentioned above, although embodiment and the Example of this invention were described, embodiment described above and an Example do not limit the invention which concerns on a claim. In addition, it should be noted that not all the combinations of features described in the embodiments and examples are necessary for the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1 Protective film 2 Optical film material 3 Adhesive layer 4 Release sheet 5 Adhesive layer 6 Optical film material

21 Polarizing film 22 Reflecting layer

50 Liquid crystal layer 52 Substrate

Claims (8)

An acrylic copolymer (A) having a weight average molecular weight of from 400,000 to less than 900,000 containing 1% by weight to 4% by weight of a carboxyl group-containing monomer as a copolymer component;
The weight average molecular weight containing 0.1 to 4% by weight of a carboxyl group-containing monomer and 0.05 to 5% by weight of a hydroxyl group-containing monomer as a copolymer component is 400,000 to less than 900,000 Acrylic copolymer (B) of
Isocyanate compound (C) to be added in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B);
A pressure-sensitive adhesive composition comprising:   The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer (A) and the acrylic copolymer (B) are contained in a weight ratio of 50/50 or more and 99/1 or less. The difference between the solubility parameter (SP _B) of the solubility parameter of the acrylic copolymer _(A) (SP A) and the acrylic copolymer (B), -0.5 to 0.5 The pressure-sensitive adhesive composition according to claim 1 or 2. The glass transition point of the acrylic copolymer _(A) (Tg A) and the relationship between the glass transition point of the acrylic copolymer (B) and (Tg _B) satisfies _Tg A <Tg _B Claim 1 4. The pressure-sensitive adhesive composition according to any one of 3 above.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising an epoxy compound or an aziridine compound.   The epoxy compound or the aziridine compound is added in an amount of 0.005 parts by weight or more and 0.05 parts by weight or less based on 100 parts by weight of the mixture of the acrylic copolymer (A) and the acrylic copolymer (B). The pressure-sensitive adhesive composition according to claim 5.   The optical film which has an adhesive layer formed from the adhesive composition of any one of Claims 1-6.   A liquid crystal display device comprising the optical film according to claim 7.