JP6738622B2 - Adhesive composition and adhesive sheet - Google Patents

Description

The present invention relates to an adhesive composition and an adhesive sheet.

Many image display units such as mobile phones and mobile terminals have a liquid crystal display device incorporated therein.
Generally, a liquid crystal display device includes a liquid crystal cell and an optical film such as a polarizing plate, a retardation plate, and a brightness enhancement film. In recent years, the number of liquid crystal display devices equipped with a touch panel is increasing. The liquid crystal cell and the optical film, the optical films, or the optical film and the touch panel are attached to each other via an adhesive layer formed of an adhesive composition.

Since an optical film such as a polarizing plate is usually formed by laminating members having different contraction rates, warpage occurs due to a change in temperature or humidity, and floating, peeling or foaming occurs at the interface between the pressure-sensitive adhesive layer and the optical film. Etc. may occur. Therefore, even when exposed to a high temperature environment or a high temperature and high humidity environment, the pressure-sensitive adhesive composition used for the polarizing plate (hereinafter, also referred to as “polarizing plate pressure-sensitive adhesive composition”) floats. There is a demand for a property that does not easily peel off, foam, or the like, that is, durability.

For example, in Patent Document 1, a carboxyl group-containing monomer and an aromatic ring-containing monomer are copolymerized, and an acrylic copolymer (A) having a weight average molecular weight of 500,000 to 3,000,000, a hydroxyl group-containing monomer, and an aromatic ring-containing monomer. Disclosed is a pressure-sensitive adhesive composition containing an acrylic copolymer (B) having a weight average molecular weight of 8,000 to 300,000, which is copolymerized with a monomer, and a crosslinking agent (C). In Patent Document 1, it is said that by combining two kinds of copolymers, appropriate cohesive force and excellent stress relaxation property are given to the pressure-sensitive adhesive composition, and excellent durability is realized.

JP 2012-214547 A

In recent years, the demand for liquid crystal display devices operated with a touch pen is increasing. In a liquid crystal display device operated with a touch pen, a local load is repeatedly applied to the liquid crystal display surface, so that the adhesive layer bonding the constituent members of the liquid crystal display device cannot cope with the local load, and the adhesive Dimples may occur on the surface of the layer. As a result, a dent is also formed on the liquid crystal display surface, causing a problem in the liquid crystal display.

Regarding the above-mentioned point, in the conventional pressure-sensitive adhesive composition including the pressure-sensitive adhesive composition described in Patent Document 1, the problem of the dent due to the local load, which may occur in the liquid crystal display device operated by the touch pen, is particularly It has not been considered.
For example, the pressure-sensitive adhesive composition described in Patent Document 1 has excellent stress relaxation properties and has durability such that peeling or the like is less likely to occur when exposed to a high temperature environment or the like, but an acrylic copolymer ( Since the cross-linked portion formed by A) is excessively soft, it cannot cope with the local load applied when the touch pen is operated, and the surface of the pressure-sensitive adhesive layer is dented, which causes a problem in liquid crystal display.

Such a problem is solved by, for example, making the pressure-sensitive adhesive layer extremely soft. This is because if the pressure-sensitive adhesive layer is extremely soft, even if it is dented once, the dent will be alleviated and returned. However, if the pressure-sensitive adhesive layer is too soft, problems such as sticking out of the pressure-sensitive adhesive when punching out the polarizing plate tend to occur, resulting in poor processability.
Further, the above-mentioned problems can be solved by making the pressure-sensitive adhesive layer extremely hard, for example. However, if the pressure-sensitive adhesive layer is too hard, when exposed to a high temperature environment or a high temperature and high humidity environment, floating, peeling, foaming or the like occurs.
As described above, a pressure-sensitive adhesive composition which has excellent durability and processability while solving the problem of dent due to local load that may occur in a liquid crystal display device operated with a touch pen has not been known.

The present invention has been made in view of the above circumstances, and has excellent durability and processability, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet that are unlikely to cause a dent due to a local load such as a touch pen operation. The challenge is to provide.

Specific means for solving the problems include the following aspects.
<1> Having a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl(meth)acrylate, the content of the structural unit derived from the monomer having a hydroxyl group is in all structural units. On the other hand, a (meth)acrylic copolymer A in the range of 0.01% by mass to 0.5% by mass, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from an alkyl(meth)acrylate. And the content of the structural unit derived from the monomer having a hydroxyl group is in the range of 0.1% by mass to 4% by mass with respect to all structural units, and (meth)acrylic copolymer B And a tolylene diisocyanate compound in the range of 5 to 30 parts by mass relative to 100 parts by mass of the total amount of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B. The constitution b in which the content ratio b of the structural unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B is derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer A The content ratio of the unit is higher than the content ratio a, and the content ratio of the (meth)acrylic copolymer A to the (meth)acrylic copolymer B [content of the (meth)acrylic copolymer A/(meth) The content of acrylic copolymer B] is in the range of 60/40 to 95/5 on a mass basis, and the solubility parameter of the (meth)acrylic copolymer A and the (meth)acrylic copolymer An adhesive composition in which the absolute value of the difference from the solubility parameter of the combined product B is 0.2 or less.

<2> In the (meth)acrylic copolymer A and the (meth)acrylic copolymer B, the content ratio of the constituent unit derived from the monomer having a hydroxyl group is the (meth)acrylic copolymer The pressure-sensitive adhesive composition according to <1>, which is in the range of 0.05 mass% to 1.5 mass% with respect to all the constituent units of the combined A and the (meth)acrylic copolymer B.
<3> Derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B with respect to the content ratio a of the structural unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer A The pressure-sensitive adhesive composition according to <1> or <2>, in which the ratio (b/a) of the content ratio b of the constituent unit is 5 to 200 on a mass basis.
<4> A silane coupling agent in the range of 0.05 parts by mass to 1 part by mass based on 100 parts by mass of the total amount of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B. The pressure-sensitive adhesive composition according to any one of <1> to <3>, which further comprises:

<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the tolylene diisocyanate compound is an adduct of tolylene diisocyanate and a polyol.
<6> Any one of <1> to <5> whose storage elastic modulus (G′) value at 30° C. after crosslinking is in the range of 2.0×10 ⁵ Pa to 1.0×10 ⁷ Pa. The pressure-sensitive adhesive composition according to.
<7> A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of <1> to <6>.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet that have excellent durability and processability and that are unlikely to cause dents due to local load due to operation of a touch pen or the like.

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and is carried out with appropriate modifications within the scope of the object of the present invention. be able to.

In the present specification, the numerical range indicated by using "to" means a range including the numerical values before and after "to" as the minimum value and the maximum value, respectively.
In the present specification, the amount of each component in the pressure-sensitive adhesive composition is present in the pressure-sensitive adhesive composition, unless a plurality of substances corresponding to each component are present in the pressure-sensitive adhesive composition, unless otherwise specified. Means the total amount of multiple substances.

In the present specification, “(meth)acrylate” is a term that includes both acrylate and methacrylate, and “(meth)acrylic” is a term that includes both acrylic and methacrylic.

In the present specification, the “structural unit derived from a monomer having a hydroxyl group” means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.
In the present specification, the “structural unit derived from alkyl(meth)acrylate” means a structural unit formed by addition polymerization of alkyl(meth)acrylate.

The "durability" in the present specification refers to a property that peeling hardly occurs and foaming can be suppressed when exposed to a high temperature environment or a high temperature and high humidity environment.

In the present specification, the term “process” is included in this term as long as the intended purpose of the process is achieved not only as an independent process but also when it cannot be clearly distinguished from other processes. Be done.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention has a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate, and the content of the structural unit derived from a monomer having a hydroxyl group is , (Meth)acrylic copolymer A in the range of 0.01% by mass to 0.5% by mass, and structural units derived from a monomer having a hydroxyl group and an alkyl(meth)acrylate. The content of the constituent unit derived from the monomer having a hydroxyl group is 0.1 mass% to 4 mass% with respect to all the constituent units (meth)acrylic copolymer. Polymer B, and a tolylene diisocyanate compound in the range of 5 to 30 parts by mass based on 100 parts by mass of the total amount of (meth)acrylic copolymer A and (meth)acrylic copolymer B; including.
Furthermore, in the pressure-sensitive adhesive composition of the present invention, the content b of the constituent units derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B is such that the hydroxyl group in the (meth)acrylic copolymer A is The content ratio of the structural unit derived from the monomer is higher than the content ratio a of the (meth)acrylic copolymer A to the (meth)acrylic copolymer B [(of the (meth)acrylic copolymer A Content/(content of (meth)acrylic copolymer B] (hereinafter, also referred to as “content ratio (A/B)”) is in the range of 60/40 to 95/5 on a mass basis, The absolute value of the difference between the solubility parameter of the (meth)acrylic copolymer A and the solubility parameter of the (meth)acrylic copolymer B is 0.2 or less.

Hereinafter, the (meth)acrylic copolymer A and the (meth)acrylic copolymer B are also referred to as “copolymer A” and “copolymer B”, respectively.
The (meth)acrylic copolymer A and the (meth)acrylic copolymer B are also collectively referred to as "(meth)acrylic copolymer".

The pressure-sensitive adhesive composition of the present invention has excellent durability and processability, and is unlikely to cause dents due to local load due to operation of a touch pen or the like.
The reason why the pressure-sensitive adhesive composition of the present invention can exert such effects is not clear, but the present inventor speculates as follows.

In the pressure-sensitive adhesive composition of the present invention, both the copolymer A and the copolymer B have a constitutional unit derived from a monomer having a hydroxyl group, and the hydroxyl group of the copolymer A and the copolymer B are The hydroxyl group and the tolylene diisocyanate compound are cross-linked. Due to these cross-linking reactions, the cohesive force of the pressure-sensitive adhesive composition is increased, and the pressure-sensitive adhesive force is improved, so that foaming between the adherend and the pressure-sensitive adhesive layer that may occur in a high temperature environment or a high temperature and high humidity environment is suppressed It is thought to be possible. Further, since the storage elastic modulus (G') of the pressure-sensitive adhesive layer is appropriately increased, for example, it is considered that the pressure-sensitive adhesive does not easily stick out during punching of the polarizing plate and is excellent in processability.

Further, the pressure-sensitive adhesive composition of the present invention contains the tolylene diisocyanate compound in an amount within a specific range, so that the (meth)acrylic copolymer is chemically mixed with the tolylene diisocyanate compound in the pressure-sensitive adhesive layer formed. There will be a cross-linked product that has been cross-linked, and a condensate of the tolylene diisocyanate compound formed by the reaction of the tolylene diisocyanate compound and water in the environment.
Since the crosslinked product obtained by chemically crosslinking the (meth)acrylic copolymer with the tolylene diisocyanate compound is relatively soft, the presence of the crosslinked product in the pressure-sensitive adhesive layer causes the pressure-sensitive adhesive layer to be partially softened. Therefore, it is considered that the adhesiveness to the adherend becomes good, and the peeling hardly occurs even when exposed to high temperature conditions or high temperature and high humidity conditions.
On the other hand, since the condensate of the tolylene diisocyanate-based compound is relatively hard, the presence of the condensate in the pressure-sensitive adhesive layer causes the pressure-sensitive adhesive layer to be appropriately hard as a whole, causing stress that causes peeling, that is, It is thought that the contraction of the body can be suppressed. More specifically, it is estimated as follows.

The pressure-sensitive adhesive composition of the present invention has a (meth)acrylic copolymer having a structural unit derived from a monomer having a hydroxyl group in the range of 0.01% by mass to 0.5% by mass based on all structural units. A and a (meth)acrylic copolymer B having a structural unit derived from a monomer having a hydroxyl group in the range of 0.1% by mass to 4% by mass based on all structural units. In the pressure-sensitive adhesive composition of the present invention, the content b of the constituent units derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B is such that the hydroxyl group in the (meth)acrylic copolymer A is It is higher than the content ratio a of the constituent unit derived from the monomer. Furthermore, the content ratio (A/B) is in the range of 60/40 to 95/5 on a mass basis. That is, the pressure-sensitive adhesive composition of the present invention contains two acrylic copolymers having different content ratios of constituent units derived from a monomer having a hydroxyl group in a predetermined ratio.
If there is a difference in the amount of hydroxyl groups between the two types of copolymers, the crosslinking of the copolymer having a large number of hydroxyl groups will proceed more and the crosslinking of the copolymer having a smaller number of hydroxyl groups will not proceed so much. And a soft cross-linked part occurs. For this reason, the (meth)acrylic copolymer is chemically crosslinked by the tolylene diisocyanate compound, and even in the relatively soft crosslinked portion, the relatively hard crosslinked portion and the relatively soft crosslinked portion have a predetermined ratio. Is formed by. The relatively hard crosslinked portion suppresses the occurrence of stress, that is, the contraction of the adherend, so that peeling is less likely to occur, and the relatively soft crosslinked portion enhances the adhesiveness with the adherend, so that peeling is less likely to occur. .. The pressure-sensitive adhesive composition of the present invention is considered to have excellent durability because it contains these two parts in an appropriate ratio.

On the other hand, if an excessively soft crosslinked portion is formed in the pressure-sensitive adhesive layer while maintaining the workability during punching, a dent occurs due to the local load applied when the touch pen is operated.
In the pressure-sensitive adhesive composition of the present invention, the absolute value of the difference between the solubility parameter of the (meth)acrylic copolymer A and the solubility parameter of the (meth)acrylic copolymer B is 0.2 or less, that is, the copolymer Since both the polymer A and the copolymer B have hydroxyl groups and their solubility parameters are close to each other, the progress of the crosslinking of the copolymer A and the copolymer B is properly aligned, and the adhesive layer is excessively softly crosslinked. It is considered that a portion is less likely to occur, and a depression due to a local load applied when operating the touch pen is less likely to occur. More specifically, the difference in the degree of cross-linking caused by the difference in the amount of hydroxyl groups in the two types of copolymers is taken into account by the two types of copolymers depending on the component other than the monomer having a hydroxyl group, that is, the component not involved in the cross-linking. The solubility parameter is adjusted so as to be close to each other to maintain the processability at the time of punching, and also suppresses the occurrence of an excessively soft crosslinked portion in the pressure-sensitive adhesive layer, and makes it difficult to cause a dent due to a local load.
That is, in the pressure-sensitive adhesive composition of the present invention, having a copolymer having many hydroxyl groups and a copolymer having less hydroxyl groups, by adjusting the difference in the solubility parameter of each other, a hard crosslinking site and a soft crosslinking site Since it occurs moderately, it is considered that the depression due to the local load applied when the touch pen is operated hardly occurs.
In addition, for example, in a pressure-sensitive adhesive composition containing a copolymer having a large difference in the rate of progress of cross-linking, a hard cross-linking site and a soft cross-linking site cannot be balanced, and dents due to local load cannot be suppressed.

[(Meth)acrylic copolymer A and (meth)acrylic copolymer B]
The pressure-sensitive adhesive composition of the present invention has a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate, and the content of the structural unit derived from a monomer having a hydroxyl group is Derived from the (meth)acrylic copolymer A (that is, the copolymer A) in the range of 0.01% by mass to 0.5% by mass with respect to all the constituent units, and the monomer having a hydroxyl group. Having a structural unit and a structural unit derived from an alkyl (meth)acrylate, the content of the structural unit derived from a monomer having a hydroxyl group is in the range of 0.1% by mass to 4% by mass with respect to all the structural units. And the copolymer B (that is, the copolymer B).
Furthermore, in the pressure-sensitive adhesive composition of the present invention, the content ratio b of the constituent unit derived from the monomer having a hydroxyl group in the copolymer B is less than that of the constituent unit derived from the monomer having a hydroxyl group in the copolymer A. The content ratio [content ratio (A/B)] of the copolymer A with respect to the copolymer B is higher than the content ratio a, and is in the range of 60/40 to 95/5 on a mass basis. The absolute value of the difference between the solubility parameter of 1 and the solubility parameter of the copolymer B is 0.2 or less.

Both the copolymer A and the copolymer B are preferably copolymers containing an alkyl (meth)acrylate as a main component. Here, the term “copolymer having alkyl (meth)acrylate as a main component” means that the content of the structural unit derived from alkyl (meth)acrylate is 50% by mass or more based on all the structural units of the copolymer. Means a copolymer having
The content of the structural unit derived from the alkyl (meth)acrylate is such that both the copolymer A and the copolymer B are easy to adjust the tackiness and viscoelasticity with respect to all the structural units of the copolymer. It is more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more.

From the viewpoint of adhesive strength, the total content of the copolymer A and the copolymer B in the pressure-sensitive adhesive composition of the present invention is 70% by mass to 95% by mass based on the total solid content of the pressure-sensitive adhesive composition. A range is preferred.

In the pressure-sensitive adhesive composition of the present invention, the content ratio [content ratio (A/B)] of the copolymer A to the copolymer B is in the range of 60/40 to 95/5 on a mass basis.
Since the pressure-sensitive adhesive composition of the present invention has a content ratio (A/B) of 60/40 or more, the pressure-sensitive adhesive layer as a whole becomes moderately hard, which causes stress, that is, Since shrinkage can be suppressed, peeling is less likely to occur. In addition, the pressure-sensitive adhesive composition of the present invention has a content ratio (A/B) of 95/5 or less, so that a soft crosslinked portion is formed when it is formed into a pressure-sensitive adhesive layer, and thus the adhesiveness to an adherend is low. It becomes good and peeling is less likely to occur.
From the same viewpoint as above, the content ratio (A/B) is preferably in the range of 65/35 to 90/10, more preferably in the range of 70/30 to 85/15.

In the pressure-sensitive adhesive composition of the present invention, the absolute value of the difference between the solubility parameter of copolymer A and the solubility parameter of copolymer B is 0.2 or less.
Since the absolute value of the difference between the solubility parameter of the copolymer A and the solubility parameter of the copolymer B is 0.2 or less, the pressure-sensitive adhesive composition of the present invention is subject to local load due to operation of a touch pen or the like. Dimples are unlikely to occur.

When an excessively soft crosslinked portion is generated in the adhesive layer, a dent is caused by a local load due to the operation of the touch pen or the like.
In the pressure-sensitive adhesive composition of the present invention, the solubility parameters of the two copolymers having different amounts of hydroxyl groups are brought close to each other, whereby the progress of crosslinking of the two copolymers is properly aligned, and the pressure-sensitive adhesive layer is excessively advanced. In addition, it suppresses the generation of soft cross-linking parts and makes it difficult for dents due to local loads to occur.

Further, the pressure-sensitive adhesive composition of the present invention has the absolute value of the difference between the solubility parameter of the copolymer A and the solubility parameter of the copolymer B of 0.2 or less, so that the copolymer A and the copolymer are Since the compatibility with B is excellent, the formed pressure-sensitive adhesive layer is unlikely to be whitened, and can be suitably used for laminating articles such as touch panels and optical films that require transparency.

The absolute value of the difference between the solubility parameter of the copolymer A and the solubility parameter of the copolymer B is from the viewpoint of making it more difficult to cause depression due to local load due to operation of a touch pen, and transparency of the touch panel, optical film, and the like. From the viewpoint of suitable use for laminating articles requiring the above, it is preferably 0.15 or less, more preferably 0.12 or less, still more preferably 0.08 or less. The lower limit value is not particularly limited, and for example, it is preferable that there is no difference in solubility parameter between the copolymer A and the copolymer B, that is, 0.

In the present specification, the solubility parameter [SP value, unit: (cal/cm ³ ) ^0.5 ] of the (meth)acrylic copolymer is the molecular attraction constant (G) of the constituent units constituting the copolymer. ). That is, the SP value of each homopolymer of each constitutional unit constituting the copolymer was calculated by the following calculation formula, and the SP value was multiplied by the mole fraction of each constitutional unit and summed. Then, the solubility parameter is calculated.
SP value of homopolymer=dΣG/M
Here, d represents the density (g/l) of the homopolymer, ΣG represents the sum of the molecular attraction constants in the molecules of the constituent units, and M represents the molecular weight (g/mol) of the constituent units. ..

In addition, the SP value of the homopolymer in a typical monomer that can form the copolymer A and the copolymer B is 8.980 for n-butyl acrylate and 9.720 for methyl acrylate, 2-hydroxyethyl acrylate is 12.50, 4-hydroxybutyl acrylate is 10.90, acrylic acid is 14.60, and t-butyl acrylate is 8.460.

Both the copolymer A and the copolymer B have a structural unit derived from a monomer having a hydroxyl group, and the hydroxyl group of the copolymer A and the hydroxyl group of the copolymer B are combined with a crosslinking agent (that is, And a tolylene diisocyanate-based compound described below) undergo a crosslinking reaction. These cross-linking reactions increase the cohesive force of the pressure-sensitive adhesive composition and improve the pressure-sensitive adhesive force, so that foaming between the adherend and the pressure-sensitive adhesive layer, which may occur in a high temperature environment or a high temperature and high humidity environment, occurs. Can be suppressed.

The content of the constituent unit derived from the monomer having a hydroxyl group in the copolymer A is in the range of 0.01% by mass to 0.5% by mass with respect to all the constituent units.
Since the content of the structural unit derived from the monomer having a hydroxyl group in the copolymer A is 0.01% by mass or more based on all the structural units, it does not become too soft when formed into a pressure-sensitive adhesive layer. The generation (foaming) of gas from the optical film can be suppressed. In addition, the content of the structural unit derived from the monomer having a hydroxyl group in the copolymer A is 0.5% by mass or less with respect to all the structural units, so that the adhesive layer does not become too hard. The adhesiveness to the adherend is excellent, and peeling from the adherend is suppressed.
From the same viewpoint as above, the content of the structural unit derived from the monomer having a hydroxyl group in the copolymer A is preferably 0.03 mass% to 0.5 mass% with respect to all the structural units. , And more preferably in the range of 0.05% by mass to 0.3% by mass.

The content of the constituent unit derived from the monomer having a hydroxyl group in the copolymer B is in the range of 0.1% by mass to 4% by mass with respect to all the constituent units.
Since the content of the structural unit derived from the monomer having a hydroxyl group in the copolymer B is 0.1% by mass or more based on all the structural units, it becomes moderately hard when used as an adhesive layer, It is possible to suppress the generation of stress due to shrinkage that may occur in the adherend (for example, a polarizing plate) exposed to the environment or the high temperature and high humidity environment, and it becomes difficult to peel off. In addition, the content of the structural unit derived from the monomer having a hydroxyl group in the copolymer B is 4% by mass or less with respect to all the structural units, so that the adhesive layer does not become too hard, and Excellent adhesion to the adherend and suppression of peeling from the adherend.
From the same viewpoint as above, the content of the structural unit derived from the monomer having a hydroxyl group in the copolymer B is preferably in the range of 0.5% by mass to 2% by mass with respect to all the structural units. ..

If there is a difference in the amount of hydroxyl groups between the two types of copolymers, the crosslinking of the copolymer having a large number of hydroxyl groups will proceed more and the crosslinking of the copolymer having a smaller number of hydroxyl groups will not proceed so much. And a soft cross-linked part occurs.
In the pressure-sensitive adhesive composition of the present invention, the content rate b of the constituent unit derived from the monomer having a hydroxyl group in the copolymer B is the content rate of the constituent unit derived from the monomer having a hydroxyl group in the copolymer A. higher than a. Therefore, the pressure-sensitive adhesive composition of the present invention contains two types of (meth)acrylic copolymers having different content ratios of constituent units derived from a monomer having a hydroxyl group, and is used as a pressure-sensitive adhesive layer. Occasionally, relatively soft and hard cross-links occur. As a result, the adhesiveness with the adherend can be enhanced while suppressing the generation of stress that causes peeling, and thus the pressure-sensitive adhesive composition of the present invention has excellent durability.

In the copolymer A and the copolymer B, the content ratio of the structural unit derived from the monomer having a hydroxyl group is 0.05% by mass to 1 with respect to all the structural units of the copolymer A and the copolymer B. The range of 0.5 mass% is preferable, and the range of 0.1 mass% to 1.0 mass% is more preferable.
When the content of the constituent unit derived from the monomer having a hydroxyl group in the copolymer A and the copolymer B is 0.05% by mass or more with respect to all the constituent units of the copolymer A and the copolymer B. If so, the pressure-sensitive adhesive layer does not become too soft, and for example, gas generation (foaming) from the optical film can be suppressed.
In the copolymer A and the copolymer B, the content of the structural unit derived from the monomer having a hydroxyl group is 1.5% by mass or less based on all the structural units of the copolymer A and the copolymer B. If so, the adhesive layer does not become too hard, has excellent adhesion to the adherend, and is prevented from peeling from the adherend.

In addition, in other words, the above content is included in the copolymer A in the pressure-sensitive adhesive composition with respect to all the constituent units (mass basis) of the copolymer A and the copolymer B in the pressure-sensitive adhesive composition. It is the ratio of the total mass of the structural unit derived from the monomer having a hydroxyl group and the structural unit derived from the monomer having a hydroxyl group contained in the copolymer B.

The ratio (b/a) of the content ratio b of the constituent unit derived from the monomer having a hydroxyl group in the copolymer B to the content a of the constituent unit derived from the monomer having a hydroxyl group in the copolymer A is From the viewpoint of further improving durability and processability, the range of 5 to 200 is preferable, the range of 5 to 100 is more preferable, and the range of 5 to 30 is further preferable on a mass basis.

Examples of the monomer having a hydroxyl group, which is one component of the copolymer A and the copolymer B, include a monomer having a hydroxyl group and an ethylenically unsaturated bond group.
Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and 3-methyl-3. -Hydroxybutyl (meth)acrylate, 1,3-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 glycol) mono(meth)acrylate, N-methylol(meth)acrylamide, N- Examples thereof include hydroxyethyl (meth)acrylamide, allyl alcohol, methallyl alcohol and the like.

Among these, as the monomer having a hydroxyl group, from the viewpoint of good compatibility and copolymerizability with other monomers and the good crosslinking reaction with a crosslinking agent, the number of carbon atoms is 1 to 1. A hydroxyalkyl (meth)acrylate having a hydroxyalkyl group of 5 is preferable, and a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group of 2 to 4 carbon atoms is more preferable. Specifically, as the monomer having a hydroxyl group, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferable, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are more preferable.

Both the copolymer A and the copolymer B may have only one type of structural unit derived from a monomer having a hydroxyl group, or may have two or more types.

The alkyl (meth)acrylate which is the main component of the copolymer A and the copolymer B is not particularly limited. The alkyl moiety of the alkyl (meth)acrylate may be linear, branched or cyclic. The carbon number of the alkyl moiety is preferably in the range of 1 to 18, more preferably in the range of 1 to 8, and further preferably in the range of 1 to 4.

Examples of the alkyl(meth)acrylate include methyl(meth)acrylate, ethyl(meth)acrylate, n-butyl(meth)acrylate, i-butyl(meth)acrylate, s-butyl(meth)acrylate, t-butyl(meth). Acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, Examples thereof include n-dodecyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.

As the alkyl (meth)acrylate that is the main component of the copolymer A, at least one selected from methyl (meth)acrylate and n-butyl (meth)acrylate is preferable from the viewpoint of easily achieving both hardness and softness. , At least one selected from methyl acrylate and n-butyl acrylate is more preferable, and n-butyl acrylate is further preferable.

As the alkyl (meth)acrylate that is the main component of the copolymer B, methyl (meth)acrylate, n-butyl (meth)acrylate, and t-butyl (meth) are easy to combine with hardness and softness. At least one selected from acrylates is preferable, at least one selected from methyl acrylate, n-butyl acrylate, and t-butyl acrylate is more preferable, and a combination of n-butyl acrylate and methyl acrylate or n-butyl acrylate and t is used. More preferred is the combination with -butyl acrylate.

The (meth)acrylic copolymer may have only one type of structural unit derived from an alkyl(meth)acrylate, or may have two or more types.

Both the copolymer A and the copolymer B are required as long as they do not impair the effects of the present invention, in addition to the structural unit derived from the monomer having a hydroxyl group and the structural unit derived from the alkyl (meth)acrylate. Accordingly, it may have a structural unit derived from another monomer.
Other monomers include (meth)acrylic monomers having a carboxy group, (meth)acrylic monomers having an aromatic ring, (meth)acrylic monomers having a nitrogen atom, and other Examples thereof include copolymerizable monomers.

Examples of the (meth)acrylic monomer having a carboxy group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamic acid, monohydroxyethyl succinate (meth ) Acrylate, monohydroxyethyl (meth)acrylate maleate, monohydroxyethyl (meth)acrylate fumarate, monohydroxyethyl (meth)acrylate phthalate, 1,2-dicarboxycyclohexanemonohydroxyethyl (meth)acrylate, (meth ) Acrylic acid dimer, ω-carboxy-polycaprolactone mono(meth)acrylate and the like can be mentioned.

Examples of the (meth)acrylic monomer having an aromatic ring include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide (EO) modified cresol (meth)acrylate, and ethylene oxide. (EO) modified nonylphenol (meth)acrylate, hydroxyethylated β-naphthol acrylate, biphenyl (meth)acrylate and the like can be mentioned.

Examples of the (meth)acrylic monomer having a nitrogen atom include aminoethyl(meth)acrylate, dimethylaminoethyl(meth)acrylate, dimethylaminopropyl(meth)acrylate, N,N-dimethyl(meth)acrylamide, N, Examples include N-diethyl acrylamide, N-ethyl, N-methyl (meth)acrylamide, N-isopropyl (meth)acrylamide and the like.

Other copolymerizable monomers include styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, vinyltoluene, vinylpyridine, acrylonitrile, methacrylonitrile, vinyl formate, vinyl acetate, Examples thereof include vinyl propionate and various derivatives thereof.

The weight average molecular weights (Mw) of the copolymer A and the copolymer B are not particularly limited, and are, for example, preferably 700,000 to 2,000,000, and more preferably 1,000,000 to 1,500,000.
The weight average molecular weight can be adjusted by the polymerization reaction temperature, time, amount of organic solvent and the like.
When the weight average molecular weights of the copolymer A and the copolymer B are each in the range of 700,000 to 2,000,000, the viscosity of the pressure-sensitive adhesive composition will be appropriately low and the coatability will be good.

The weight average molecular weight (Mw) of the copolymer A and the copolymer B is a value measured by the following method.
-Measurement method of weight average molecular weight (Mw)-
It is measured according to the following (1) to (3).
(1) A (meth)acrylic copolymer solution [solution containing a copolymer A or a copolymer B] is applied to release paper and dried at 100° C. for 2 minutes to obtain a film-shaped (meth)acrylic copolymer. A polymer is obtained.
(2) The film-like (meth)acrylic copolymer obtained in (1) above is dissolved in tetrahydrofuran so that the solid content is 0.2% by mass.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight (Mw) of the (meth)acrylic copolymer is measured as a standard polystyrene conversion value under the following conditions.

(conditions)
GPC: HLC-8220 GPC [Tosoh Corporation]
Column: TSK-GEL GMHXL 4 used [Tosoh Corporation]
Mobile phase solvent: Tetrahydrofuran Flow rate: 0.6 ml/min
Column temperature: 40°C

The method for producing the copolymer A and the copolymer B is not particularly limited. The copolymer A and the copolymer B are each obtained by polymerizing the above-mentioned monomer, that is, a monomer having a hydroxyl group, an alkyl (meth)acrylate, and optionally another monomer. Can be manufactured.
The polymerization method of the copolymer A and the copolymer B is not particularly limited and can be appropriately selected from the commonly used polymerization methods. Examples of the polymerization method include a solution polymerization method, an emulsion polymerization method and a suspension polymerization method. Among these, the solution polymerization method is preferable as the polymerization method because the production is relatively simple and can be performed in a short time.

In the solution polymerization method, generally, a predetermined organic solvent, a monomer, a polymerization initiator and, if necessary, a chain transfer agent are charged in a polymerization tank, and the mixture is stirred at a reflux temperature of the organic solvent in a nitrogen stream for several hours with stirring. Heat reaction for a period of time. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and/or the chain transfer agent may be sequentially added. The weight average molecular weights of the copolymer A and the copolymer B can be adjusted to desired values by adjusting the reaction temperature, time, amount of solvent, and type or amount of catalyst.

Examples of the organic solvent for polymerization used in the production of the copolymer A and the copolymer B include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, alcohols. A compound etc. are mentioned.
These organic solvents may be used alone or in combination of two or more.
Examples of the polymerization initiator include organic peroxides and azo compounds that can be used in ordinary polymerization methods.

[Tolylene diisocyanate compound]
The pressure-sensitive adhesive composition of the present invention contains the tolylene diisocyanate compound in the range of 5 parts by mass to 30 parts by mass based on 100 parts by mass of the total amount of the above-mentioned copolymer A and copolymer B.
In the pressure-sensitive adhesive composition of the present invention, the tolylene diisocyanate compound functions as a crosslinking agent.
The pressure-sensitive adhesive composition of the present invention contains the tolylene diisocyanate compound in the range of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the total amount of the above-mentioned copolymer A and copolymer B. When the pressure-sensitive adhesive layer is formed, the pressure-sensitive adhesive layer is appropriately hardened, and it is possible to suppress the occurrence of stress due to shrinkage that may occur in an adherend (eg, a polarizing plate) exposed to a high temperature environment or a high temperature and high humidity environment. More specifically, when the content of the tolylene diisocyanate compound is within the above range, not only the curing by the crosslinking reaction between the hydroxyl group of the (meth)acrylic copolymer and the tolylene diisocyanate compound described above, Also, curing occurs due to a condensation reaction between the tolylene diisocyanate compound and water. When the two curings occur, the pressure-sensitive adhesive layer has an appropriate hardness that can effectively suppress the peeling due to the shrinkage of the adherend exposed to the high temperature environment or the high temperature and high humidity environment.
The pressure-sensitive adhesive composition of the present invention contains the tolylene diisocyanate compound in the range of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the total amount of the above-mentioned copolymer A and copolymer B. Since the storage elastic modulus (G′) of the pressure-sensitive adhesive layer is appropriately increased, for example, the pressure-sensitive adhesive does not easily stick out when the polarizing plate is punched out, and the processability is excellent.

Examples of the tolylene diisocyanate-based compound include tolylene diisocyanate, a dimer of tolylene diisocyanate, an adduct of tolylene diisocyanate and a polyol, an isocyanurate body of a trimer or a pentamer of tolylene diisocyanate, and tolylene diisocyanate. And tolylene diisocyanate compounds derived from various tolylene diisocyanates such as burettes.
Among these, the tolylene diisocyanate compound is excellent in reactivity, can increase the crosslink density, and is excellent in compatibility with the above-described copolymer A and copolymer B. An adduct of diisocyanate and polyol is preferable, and an adduct of tolylene diisocyanate and trimethylolpropane is particularly preferable.

As the tolylene diisocyanate compound, a commercially available commercially available product may be used.
Examples of commercially available products include "Coronate (registered trademark) L" of Tosoh Corporation as an adduct of tolylene diisocyanate and trimethylol propane, and "Coronate of Tosoh Corporation" as an isocyanurate of tolylene diisocyanate. (Registered trademark) 2030” and the like (both are trade names).

The pressure-sensitive adhesive composition of the present invention may contain only one type of tolylene diisocyanate compound, or may include two or more types thereof.

The content of the tolylene diisocyanate compound in the pressure-sensitive adhesive composition of the present invention is in the range of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the total amount of the above-described copolymer A and copolymer B. is there.
In the pressure-sensitive adhesive composition of the present invention, the content of the tolylene diisocyanate compound is 5 parts by mass or more based on 100 parts by mass of the total amount of the above-described copolymer A and copolymer B, It can suppress foaming and peeling, and has excellent durability and processability. Further, in the pressure-sensitive adhesive composition of the present invention, the content of the tolylene diisocyanate compound is 30 parts by mass or less based on 100 parts by mass of the total amount of the above-mentioned copolymer A and copolymer B. As a result, the compatibility with the copolymer A and the copolymer B is improved, so that the pressure-sensitive adhesive layer formed is unlikely to be whitened, and is suitable for sticking to an article such as a touch panel or an optical film that requires transparency. Can be used for

The content of the tolylene diisocyanate compound in the pressure-sensitive adhesive composition of the present invention is 100% by mass of the total amount of the above-described copolymer A and copolymer B from the viewpoint of improving durability and processability, and suppressing whitening. The range of 10 parts by mass to 30 parts by mass is preferable, and the range of 12 parts by mass to 30 parts by mass is more preferable for the parts.

〔Silane coupling agent〕
The pressure-sensitive adhesive composition of the present invention further contains a silane coupling agent in the range of 0.05 parts by mass to 1 part by mass based on 100 parts by mass of the total amount of the above-mentioned copolymer A and copolymer B. It is preferable.
The pressure-sensitive adhesive composition of the present invention further contains a specific amount of the silane coupling agent as described above, thereby exhibiting excellent adhesiveness when formed into a pressure-sensitive adhesive layer, and a display device incorporating a polarizing plate (for example, , Even when the liquid crystal display device) is exposed to a high temperature environment or a high temperature and high humidity environment, the adhesive layer and the polarizing plate or the liquid crystal cell are more difficult to peel off.

Examples of the silane coupling agent include polymerizable unsaturated group-containing silane compounds (vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, etc.), mercapto group-containing silane compounds (3-mercaptopropyltrisilane). Methoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, etc.), a silane compound having an epoxy structure [2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.], an amino group-containing silane compound [3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, etc.], Tris-(3- And trimethoxysilylpropyl) isocyanurate.

As the silane coupling agent, a commercially available product on the market may be used.
Examples of commercially available products include "KBM-403", "KBM-303", "KBM-402", "KBE-402", "KBE-403" (all are trade names) manufactured by Shin-Etsu Chemical Co., Ltd. Are listed. All of these commercial products are silane compounds having an epoxy structure.

When the pressure-sensitive adhesive composition of the present invention further contains a silane coupling agent, it may contain only one silane coupling agent or two or more silane coupling agents.

When the pressure-sensitive adhesive composition of the present invention further contains a silane coupling agent, the content of the silane coupling agent in the pressure-sensitive adhesive composition may be the above-mentioned copolymer A and copolymer from the viewpoint of further improving durability. The range of 0.02 parts by mass to 0.7 parts by mass is more preferable, and the range of 0.1 parts by mass to 0.5 parts by mass is still more preferable, relative to 100 parts by mass of the total amount of B.

[Other ingredients]
The pressure-sensitive adhesive composition according to the present invention includes the (meth)acrylic copolymer A, the (meth)acrylic copolymer B, the tolylene diisocyanate compound, and the silane coupling agent, which is an optional component. In the range that does not impair the effect of, if necessary, solvent, other cross-linking agents, weather resistance stabilizers, tackifiers, plasticizers, softeners, release aids, dyes, pigments, inorganic fillers, surfactants, It may contain an antioxidant, a metal corrosion inhibitor, an ultraviolet absorber, a light stabilizer such as a hindered amine compound, and the like.

<Solvent>
The pressure-sensitive adhesive composition of the present invention may contain a solvent from the viewpoint of improving coatability with respect to optical films such as polarizing plates, touch panels, and liquid crystal cells.

As the solvent, hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, hydrocarbons such as methylcyclohexane, dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, halogenated hydrocarbons such as dichloropropane, methanol, ethanol, propanol, Isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol and other alcohols, diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran and other ethers, acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone and other ketones, methyl acetate, acetic acid Ethyl, butyl acetate, isobutyl acetate, amyl acetate, ethyl acetate, and other esters, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, and other polyols, and organic solvents such as their derivatives. ..

<Other cross-linking agents>
The pressure-sensitive adhesive composition according to the present invention may contain other cross-linking agent other than the tolylene diisocyanate compound, as long as the effects of the present invention are not impaired.
Other crosslinking agents are not particularly limited, and examples thereof include polyisocyanate compounds other than tolylene diisocyanate compounds, polyepoxy compounds, polyaziridine compounds, and metal chelate compounds.
When the pressure-sensitive adhesive composition of the present invention contains other cross-linking agent, it may contain only one kind of the other cross-linking agent, or may contain two or more kinds thereof.

[Physical properties of adhesive composition]
From the viewpoint of further improving durability, the pressure-sensitive adhesive composition of the present invention preferably has a storage elastic modulus (G′) value at 30° C. of 2.0×10 ⁵ Pa to 1.0×10 ⁷ after crosslinking. The range is Pa, more preferably 2.0×10 ⁵ Pa to 5.0×10 ⁶ Pa, and further preferably 3.0×10 ⁵ Pa to 5.0×10 ⁶ Pa.

When the value of the storage elastic modulus (G′) at 30° C. after crosslinking of the pressure-sensitive adhesive composition is 2.0×10 ⁵ Pa or more, the pressure-sensitive adhesive layer has sufficient hardness and stress is not generated. Since it can be sufficiently suppressed, peeling does not easily occur. In addition, since the pressure-sensitive adhesive layer has sufficient hardness, it is difficult for protrusion to occur when punching the polarizing plate.
When the value of the storage elastic modulus (G′) at 30° C. after crosslinking of the pressure-sensitive adhesive composition is 1.0×10 ⁷ Pa or less, the pressure-sensitive adhesive layer is not too hard, and thus the adhesion to the adherend Peeling is less likely to occur due to lack.

The storage elastic modulus (G′) of the pressure-sensitive adhesive composition was measured using a dynamic viscoelasticity measuring device as a measuring device, at an evaluation temperature of 30° C., a cone used of 8 mmφ, and a measuring gap of 0.6 mm. The sample is measured while applying shear stress at a frequency of 1 Hz.
As the dynamic viscoelasticity measuring apparatus, Physica MCR301 (product name) manufactured by Anton Paar can be preferably used. However, the measuring device is not limited to this.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition.
The pressure-sensitive adhesive sheet of the present invention may be a non-substrate type pressure-sensitive adhesive sheet having no substrate, or may be a substrate-type pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of a substrate such as an optical film.
Since the pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition, the interface between the adherend and the pressure-sensitive adhesive layer even when exposed to a high temperature environment or a high temperature and high humidity environment. It does not easily float or peel off, is excellent in workability, and is unlikely to cause dents due to the operation of the touch pen.

The thickness of the pressure-sensitive adhesive layer is not particularly limited and can be appropriately set depending on, for example, the use and the required performance. The thickness of the pressure-sensitive adhesive layer is, for example, in the range of 1 μm to 100 μm.

When the pressure-sensitive adhesive sheet of the present invention is used for optical applications, the pressure-sensitive adhesive layer preferably has high transparency. Specifically, the total light transmittance of the pressure-sensitive adhesive layer in the visible light wavelength region measured according to JIS K 7361 (1997) is preferably 85% or more, more preferably 90% or more.
The haze of the pressure-sensitive adhesive layer measured according to JIS K 7136 (2000) is preferably 2.5% or less, more preferably 2.0% or less, still more preferably 1.5% or less.

The exposed pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention may be protected by a release film. The release film is not particularly limited as long as it can be easily released from the pressure-sensitive adhesive layer, and examples thereof include a resin film having at least one surface subjected to an easy release treatment with a release treatment agent. Examples of the resin film include polyester films such as polyethylene terephthalate film. Examples of the release treatment agent include fluororesin, paraffin wax, silicone, and long-chain alkyl group compound. The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put into practical use, and is peeled off at the time of use.

The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by forming the pressure-sensitive adhesive layer by applying the above-mentioned pressure-sensitive adhesive composition to a release film or a base material, and curing the composition for a certain period after drying.
The curing condition can be set to, for example, 1 to 10 days under an environment of an atmospheric temperature of 23° C. and a relative humidity of 50%. By curing the pressure-sensitive adhesive layer, the (meth)acrylic copolymer can be sufficiently crosslinked with the tolylene diisocyanate compound.

The substrate-free pressure-sensitive adhesive sheet is formed, for example, by applying the pressure-sensitive adhesive composition to the release-treated surface of the release film and drying it to form a layer of the pressure-sensitive adhesive composition, which does not contact the release film. It can be prepared by a method in which another release film is placed on the exposed surface so that the release-treated surface is in contact with the exposed surface, and cured to form an adhesive layer.

The substrate-type pressure-sensitive adhesive sheet may be produced by a method of applying the pressure-sensitive adhesive composition to a substrate such as an optical film or a method of applying the pressure-sensitive adhesive composition to a release film. Specifically, a substrate-type pressure-sensitive adhesive sheet is, for example, coated with a pressure-sensitive adhesive composition on the release-treated surface of a release film, dried to form a layer of the pressure-sensitive adhesive composition, and then release the obtained layer. It can be prepared by a method in which a base material is attached to an exposed surface that does not come into contact with the film and cured to form an adhesive layer.

An optical film can be illustrated as a base material of the adhesive sheet of a base material type. Specific examples of the optical film include optical films used in liquid crystal display devices, and more specifically, polarizing plates, retardation films, antireflection films, viewing angle widening films, brightness enhancement films, ITO. Examples thereof include optical films such as films.
Among these, an optical film is preferable and a polarizing plate is more preferable as the substrate of the substrate-type pressure-sensitive adhesive sheet.

The polarizing plate may have at least a polarizer, and a polarizing plate having a protective film on one side of the polarizer, a polarizing plate having protective films on both sides of the polarizer, and the like can be used.
For example, a polyvinyl alcohol (PVA) film in which iodine is adsorbed and oriented is used as the polarizer of the polarizing plate, and a triacetyl cellulose (TAC) film, an acrylic film or the like is used as the protective film of the polarizer.

When the polarizing plate is used as the base material, the pressure-sensitive adhesive layer may be formed on the PVA film or the TAC film.

Examples of the method of applying the pressure-sensitive adhesive composition to the release film or the substrate include known methods using a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, and the like. To be

The pressure-sensitive adhesive sheet of the present invention can be suitably used for bonding an optical film or the like of a liquid crystal display device. That is, the pressure-sensitive adhesive sheet of the present invention includes a polarizing plate, a retardation film, an antireflection film, a viewing angle widening film, a brightness enhancement film, a film for adhering optical films such as an ITO film, and an optical film, a liquid crystal cell, and a glass substrate. It can be preferably used for bonding with a protective film or the like. Moreover, the pressure-sensitive adhesive sheet of the present invention can be suitably used for bonding a touch panel to a liquid crystal cell, a glass substrate, a protective film, or the like.

Examples of the pressure-sensitive adhesive sheet of the present invention include a substrate-free pressure-sensitive adhesive sheet having a structure (release film/pressure-sensitive adhesive layer/release film) in which release films are attached to both sides of the pressure-sensitive adhesive layer, and a pressure-sensitive adhesive layer. An example is a substrate-containing pressure-sensitive adhesive sheet having a structure (optical film/pressure-sensitive adhesive layer/release film) in which an optical film is bonded to one surface and a release film is bonded to the other surface.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples without departing from the spirit of the invention.

[Production of (meth)acrylic copolymer A]
<Production of resin A1>
In a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a reflux cooling tube, 92.49 parts by mass of n-butyl acrylate (BA) and methyl acrylate (MA) 7.5 as alkyl (meth)acrylate. After mass parts, 0.01 mass parts of 2-hydroxyethyl acrylate (2HEA) as a monomer having a hydroxyl group, and 110 mass parts of ethyl acetate as a solvent were put and mixed, the inside of the reactor was replaced with nitrogen. After that, the mixture in the reactor was heated to 70° C. with stirring, and then 0.04 parts by mass of azobisdimethylvaleronitrile (ABVN) as a polymerization initiator and 40 parts by mass of ethyl acetate as a solvent were sequentially added. Then, it was held for 6 hours to cause a polymerization reaction. After completion of the polymerization reaction, the solid content was adjusted to 40.0 mass% by diluting with ethyl acetate as a solvent to obtain a solution of (meth)acrylic copolymer A (resin A1).
The obtained resin A1 has a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate, and the content of the structural unit derived from 2HEA which is a monomer having a hydroxyl group. Is 0.01% by mass with respect to all the constituent units, and is therefore included in the (meth)acrylic copolymer A in the present invention.

<Production of Resins A2 to A8>
A solution of a (meth)acrylic copolymer A (resins A2 to A8) was obtained in the same manner as in the above-mentioned "Production of Resin A1" except that the monomer composition shown in Table 1 below was used.
Among the obtained resins A2 to A8, the resins A2 to A6 are hydroxyl group-containing monomers having a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate. Since the content of the structural unit derived from 2HEA is in the range of 0.01% by mass to 0.5% by mass with respect to all the structural units, it is included in the (meth)acrylic copolymer A in the present invention. ..

The monomer composition (unit: mass%), solubility parameter (SP value), and weight average molecular weight (Mw, unit: 10,000) of the resins A1 to A8 are shown in Table 1 below. The SP value and the weight average molecular weight of the resins A1 to A8 were obtained by the method described above.
In Table 1, "BA" represents "n-butyl acrylate", "MA" represents "methyl acrylate", "2HEA" represents "2-hydroxyethyl acrylate", and "AA" represents "acrylic acid".

[Production of (meth)acrylic copolymer B]
<Production of resin B1>
In a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a reflux cooling tube, n-butyl acrylate (BA) 87.0 parts by mass and methyl acrylate (MA) 12 parts by mass were used as alkyl (meth)acrylates. Then, 1 part by mass of 2-hydroxyethyl acrylate (2HEA) as a monomer having a hydroxyl group and 110 parts by mass of ethyl acetate as a solvent were added and mixed, and then the inside of the reactor was replaced with nitrogen. After that, the mixture in the reactor was heated to 70° C. with stirring, and then 0.04 parts by mass of azobisdimethylvaleronitrile (ABVN) as a polymerization initiator and 40 parts by mass of ethyl acetate as a solvent were sequentially added. Then, it was held for 6 hours to cause a polymerization reaction. After completion of the polymerization reaction, the solid content was adjusted to 40.0 mass% by diluting with ethyl acetate as a solvent to obtain a solution of (meth)acrylic copolymer B (resin B1).
The obtained resin B1 has a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate, and the content of the structural unit derived from 2HEA which is a monomer having a hydroxyl group. Is contained in the (meth)acrylic copolymer B in the present invention because it is 1% by mass based on all the constituent units.

<Production of Resins B2 to B9>
A solution of the (meth)acrylic copolymer B (resins B2 to B9) was obtained in the same manner as in the above-mentioned "Production of Resin B1" except that the monomer composition shown in Table 2 below was used.
Of the obtained resins B2 to B9, the resins B2 to B7 are hydroxyl group-containing monomers having a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate. Since the content of the constituent units derived from 2HEA is in the range of 0.1% by mass to 4% by mass with respect to all the constituent units, it is included in the (meth)acrylic copolymer B in the present invention.

The monomer composition (unit: mass%), solubility parameter (SP value), and weight average molecular weight (Mw, unit: 10,000) of the resins B1 to B9 are shown in Table 2 below. The SP value and the weight average molecular weight of the resins B1 to B9 were calculated by the method described above.
In Table 2, "BA" is "n-butyl acrylate", "t-BA" is "t-butyl acrylate", "MA" is "methyl acrylate", "2HEA" is "2-hydroxyethyl acrylate", " “AA” represents “acrylic acid”.

[Preparation of adhesive composition]
<Example 1>
168.0 parts by mass of solution of resin A1 as (meth)acrylic copolymer A (70.0 parts by mass as solid content) and 72.0 parts by mass of solution of resin B1 as (meth)acrylic copolymer B Part (30.0 parts by mass as solid content) and Coronate (registered trademark) L (trade name, adduct of tolylene diisocyanate and trimethylolpropane, Tosoh Corporation) as tolylene diisocyanate compound 20.0 Parts by mass (15.0 parts by mass as an active ingredient) and KBM-403 (trade name, 3-glycidoxypropyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent (SC agent) 0. 4 parts by mass (0.4 parts by mass as the active ingredient) were sufficiently stirred and mixed to obtain an adhesive composition of Example 1.

<Examples 2 to 19>
The pressure-sensitive adhesive compositions of Examples 2 to 19 were obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition shown in Table 3 below was used.

<Comparative Examples 1 to 13>
The pressure-sensitive adhesive compositions of Comparative Examples 1 to 13 were obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition shown in Table 3 below was used.

[Evaluation]
1. Coating hardness (preparation of coating hardness evaluation sample)
Using each of the pressure-sensitive adhesive compositions of Examples and Comparative Examples obtained above, a coating film hardness evaluation sample was prepared by the following procedure.
First, a pressure-sensitive adhesive composition was applied to the surface-treated surface of a release film (trade name: 100E-0010NO23, Fujimori Industry Co., Ltd.) surface-treated with a silicone-based release agent so that the film thickness after drying would be 20 μm. Applied. Then, the coating film of the pressure-sensitive adhesive composition formed on the release film is dried under the conditions of a heating temperature of 100° C. and a heating time of 90 seconds using a hot air circulation dryer, and a layer (hereinafter, referred to as a layer on the release film. "Adhesive layer") was formed. Subsequently, the surface of the pressure-sensitive adhesive layer formed on the release film and the surface-treated surface of the release film (trade name: 100E-0010NO23, Fujimori Industry Co., Ltd.) surface-treated with a separately prepared silicone release agent. And were adhered to each other to obtain a pressure-sensitive adhesive sheet sample having a laminated structure of release film/adhesive layer/release film.

Next, the pressure-sensitive adhesive sheet sample obtained above was cut into a size of 50 mm×75 mm to prepare a test piece.
One release film of the test piece was peeled off to expose the adhesive layer. The exposed surface of the pressure-sensitive adhesive layer was attached to the surface of the hard coat film [trade name: KB film G01S, hard-coated polyethylene terephthalate (PET) film, Kimoto Co., Ltd.) that was not hard-coated.
Then, the other release film of the test piece was peeled off to expose the pressure-sensitive adhesive layer. A hard coat film/adhesive layer was attached using a laminator so that the exposed surface of the adhesive layer is in contact with one surface of a 0.7 mm-thick non-alkali glass plate "#1737" (Corning Corporation). / A coating film hardness evaluation sample having a laminated structure of a non-alkali glass plate was obtained.

(Evaluation test)
The coating film hardness was evaluated using the coating film hardness evaluation sample obtained above. The evaluation test was carried out as follows according to JIS K 5600-5-4, except that the load was set to 500 g and the speed was set to 48 mm/s.
A coating film hardness evaluation sample was placed on a surface property measuring machine (product name: HEIDON-14DR, Shinto Kagaku Co., Ltd.) so that the hard coat film surface was facing upward. Then, a pencil for scratch resistance test (trade name: Mitsubishi Uni-3H, Mitsubishi Pencil Co., Ltd.) is applied with a load of 500 g at an angle of 45° to the hard coat film surface of the coating film hardness evaluation sample. Then, it was attached to a surface texture measuring machine. Then, with the tip of the attached pencil pressed against the hard coat film surface of the coating film hardness evaluation sample, after moving a distance of 25 mm at a speed of 48 mm/s, the presence or absence of indentations on the hard coat film surface was visually observed. I confirmed. The evaluation test was performed three times for each sample, and the coating film hardness was evaluated according to the following evaluation criteria.
In addition, if the evaluation result is [A] or [B], the coating film has a hardness that is unlikely to cause a dent due to a local load applied when the touch pen is operated, and there is no practical problem.

-Evaluation criteria-
A: No indentation occurred in all of the three evaluation tests.
B: Indentation occurred in one of the three evaluation tests.
C: Indentation occurred in two or more of the three evaluation tests.

2. Durability (preparation of durability evaluation sample)
Using the pressure-sensitive adhesive compositions of Examples and Comparative Examples obtained above, a durability evaluation sample was prepared by the following procedure.
First, an adhesive agent was applied to the surface-treated surface of a release film (trade name: 100E-0010NO23, Fujimori Kogyo Co., Ltd.) surface-treated with a silicone-based release agent so that the coating amount after drying would be 20 g/cm ^2. The composition was applied. Then, the release film after applying the pressure-sensitive adhesive composition is dried using a hot air circulation dryer under the conditions of a heating temperature of 100° C. and a heating time of 90 seconds to form a layer on the release film (hereinafter, referred to as “adhesive layer”). Referred to as ). Then, one surface of a polarizing plate having a structure of triacetyl cellulose (TAC)/polyvinyl alcohol (PVA)/TAC and the surface of the pressure-sensitive adhesive layer on the release film are laminated and laminated, and passed through a pressure nip roll. Crimped. After pressure bonding, autoclave treatment (treatment temperature: 50° C., pressure: 5 kg/cm ² , treatment time: 20 minutes) was performed, and curing was performed for 96 hours under the conditions of 35° C. and 45% RH, and a release film/adhesive layer/ An adhesive sheet sample having a laminated structure of polarizing plates was obtained.

Next, the pressure-sensitive adhesive sheet sample obtained above was cut so that the long side was 45° with respect to the absorption axis of the polarizing plate, and a test piece having a size of 140 mm×260 mm (long side) was produced.
After peeling off the release film of the test piece to expose the pressure-sensitive adhesive layer, the exposed surface of the pressure-sensitive adhesive layer is on one surface of a 0.7 mm-thick non-alkali glass plate "#1737" (Corning Co.). It stuck using a laminator so that it might contact. After sticking, autoclave treatment (treatment temperature: 50° C., pressure: 5 kg/cm ² , treatment time: 20 minutes) was performed, and the mixture was allowed to stand for 24 hours under the conditions of 23° C. and 50% RH, and the polarizing plate/adhesive layer/ A durability evaluation sample having a laminated structure of non-alkali glass plates was obtained.

(Evaluation test)
2-1. High temperature condition (80℃)
The durability evaluation sample obtained above was left in a high temperature environment of 80° C. for 500 hours. Durability evaluation after standing The appearance of the sample was visually observed, and the durability of the pressure-sensitive adhesive composition under high temperature conditions (80°C) was evaluated according to the following evaluation criteria.
If the evaluation result is [A] or [B], there is no practical problem.

-Evaluation criteria-
A: No foaming or peeling was confirmed.
B: Almost no foaming was confirmed, and peeling was not confirmed at a position of 0.5 mm or more from the outer peripheral end on the two sides.
C: Foaming was remarkably confirmed, or peeling was confirmed at a position of 0.5 mm or more from the outer peripheral end on two sides.

2-2. High temperature and high humidity conditions (60℃, 90%RH)
The durability evaluation sample obtained above was left for 500 hours in a high temperature and high humidity environment of 60° C. and 90% RH. The appearance of the durability evaluation sample after standing was visually observed, and the high temperature and high humidity conditions (60°C, 60°C) of the pressure-sensitive adhesive composition were evaluated according to the same evaluation criteria as the durability evaluation criteria under the above high temperature conditions (80°C). The durability at 90% RH) was evaluated.
If the evaluation result is [A] or [B], there is no practical problem.

3. Processing suitability (preparation of processing suitability evaluation sample)
Using each of the pressure-sensitive adhesive compositions obtained in the above Examples and Comparative Examples, a processability evaluation sample was prepared in the following procedure.
First, an adhesive agent was applied to the surface-treated surface of a release film (trade name: 100E-0010NO23, Fujimori Kogyo Co., Ltd.) surface-treated with a silicone-based release agent so that the coating amount after drying would be 20 g/cm ^2. The composition was applied. Then, the release film after applying the pressure-sensitive adhesive composition is dried using a hot air circulation dryer under the conditions of a heating temperature of 100° C. and a heating time of 90 seconds to form a layer on the release film (hereinafter, referred to as “adhesive layer”). Referred to as ). Then, one surface of the polarizing plate having a structure of triacetyl cellulose (TAC)/polyvinyl alcohol (PVA)/TAC and the surface of the pressure-sensitive adhesive layer on the release film are laminated and bonded, and passed through a pressure nip roll. Crimped. After pressure bonding, autoclave treatment (treatment temperature: 50° C., pressure: 5 kg/cm ² , treatment time: 20 minutes) was performed, and curing was performed for 96 hours under the conditions of 35° C. and 45% RH, and a release film/adhesive layer/ An adhesive sheet sample having a laminated structure of polarizing plates was obtained. Then, 30 sheets of the obtained pressure-sensitive adhesive sheet samples were piled up to prepare a processability evaluation sample.

(Evaluation test)
The processing suitability evaluation sample produced above was cut by a polarizing plate punching machine. After cutting, the presence or absence of protrusion of the pressure-sensitive adhesive from the side surface of the processability evaluation sample was visually confirmed.

-Evaluation criteria-
A: No protrusion of the adhesive was confirmed from the cut surface.
B: A slight protrusion of the adhesive was confirmed from the cut surface.
C: The protrusion of the adhesive was confirmed from the cut surface.

[Measurement of storage elastic modulus (G')]
(Preparation of storage elastic modulus measurement sample)
Using each of the pressure-sensitive adhesive compositions of Examples and Comparative Examples obtained above, a storage elastic modulus measurement sample was prepared by the following procedure.
First, on the surface-treated surface of release film A (trade name: 100E-0010NO23, Fujimori Kogyo Co., Ltd.) surface-treated with a silicone-based release agent, a pressure-sensitive adhesive composition so that the film thickness after drying is 20 μm Was applied. Then, the coating film of the pressure-sensitive adhesive composition formed on the release film is dried under the conditions of a heating temperature of 100° C. and a heating time of 90 seconds using a hot air circulation dryer, and a layer (hereinafter, referred to as a layer on the release film. "Adhesive layer") was formed. Then, the surface of the pressure-sensitive adhesive layer formed on the release film, and the surface-treated surface of the release film B (trade name: 25E-0010BD, Fujimori Industry Co., Ltd.) surface-treated with a silicone-based release agent, Were bonded together to obtain a pressure-sensitive adhesive sheet sample having a laminated structure of release film A/pressure-sensitive adhesive layer (film thickness: 20 μm)/release film B.
Then, the release film B of the obtained pressure-sensitive adhesive sheet sample was peeled off to expose the pressure-sensitive adhesive layer. After subjecting the exposed surface of the pressure-sensitive adhesive layer to corona treatment, the pressure-sensitive adhesive sheet sample was folded in two and the pressure-sensitive adhesive layers were bonded together to form a release film A/a pressure-sensitive adhesive layer (film thickness: 40 μm)/a release film A. An adhesive sheet sample having a laminated structure was obtained.
Next, one release film A of the obtained pressure-sensitive adhesive sheet sample was peeled off to expose the pressure-sensitive adhesive layer. After subjecting the exposed pressure-sensitive adhesive layer surface to corona treatment, the pressure-sensitive adhesive sheet sample was folded in two and the pressure-sensitive adhesive layers were bonded together to form a release film A/a pressure-sensitive adhesive layer (film thickness: 80 μm)/a release film A. An adhesive sheet sample having a laminated structure was obtained.
The above operation (peeling of the release film A from the pressure-sensitive adhesive sheet sample, corona treatment to the exposed pressure-sensitive adhesive layer, and bonding of the pressure-sensitive adhesive layers to each other) was repeated until the film thickness of the pressure-sensitive adhesive layer became 640 μm, to obtain The obtained adhesive sheet sample was used as a storage elastic modulus measurement sample.

(Measurement)
Using the storage elastic modulus measurement sample obtained above, the storage elastic modulus (G′) was measured under the following conditions.
Using a dynamic viscoelasticity measuring device (product name: Physica MCR301, Anton Paar) as a measuring device, an evaluation temperature: 30° C., a cone used: 8 mmφ, a measurement gap: 0.6 mm, with respect to a storage elastic modulus measurement sample Then, the storage elastic modulus (G′) (unit: Pa) was measured while applying shear stress at a frequency of 1 Hz.

Table 3 shows the compositions of the pressure-sensitive adhesive compositions of Examples 1 to 19 and Comparative Examples 1 to 13, the evaluation results, and the measurement results of the storage elastic modulus (G').

Details of the cross-linking agents a, b, and c in Table 3 are as follows.
Crosslinking agent a: Coronate (registered trademark) L (trade name, adduct of tolylene diisocyanate and trimethylolpropane, Tosoh Corporation)
Crosslinking agent b: Takenate (registered trademark) D-110N (trade name, xylene diisocyanate compound, Mitsui Chemicals, Inc.)
Crosslinking agent c: Sumidule (registered trademark) N-75 (trade name, hexamethylene diisocyanate compound, Sumika Covestrourethane Co., Ltd.)

In Table 3, "silane coupling agent" is referred to as "SC agent".
"-" in Table 3 means that there is no corresponding item.
In Table 3, "ND" indicates that the evaluation was impossible due to haze.

From the results in Table 3, all of the durability evaluation samples using the pressure-sensitive adhesive compositions of Examples 1 to 19 are less likely to peel or foam when exposed to high temperature conditions or high temperature and high humidity conditions, It became clear that it is excellent in sex. Moreover, it became clear that the processability evaluation sample using the adhesive composition of Examples 1-19 was excellent in processability. Furthermore, it is considered that the coating films formed from the pressure-sensitive adhesive compositions of Examples 1 to 19 have high hardness and are unlikely to cause dents due to the local load applied when the touch pen is operated.

On the other hand, a durability evaluation sample using the pressure-sensitive adhesive composition of Comparative Example 1 in which the content of the constituent unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer A is less than 0.01% by mass. It was revealed that the foam had poor durability when exposed to high temperature conditions or high temperature and high humidity conditions, and was inferior in durability. Further, the coating film formed from the pressure-sensitive adhesive composition of Comparative Example 1 did not have sufficient hardness.
The durability evaluation sample using the pressure-sensitive adhesive composition of Comparative Example 2 in which the content of the constituent unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer A exceeds 0.5% by mass It was revealed that peeling was likely to occur when exposed under the conditions or under high temperature and high humidity conditions, and the durability was poor.

A durability evaluation sample using the pressure-sensitive adhesive composition of Comparative Example 3 in which the content of the constituent unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B is less than 0.1% by mass, It was revealed that when exposed to high-temperature conditions or high-temperature and high-humidity conditions, peeling and foaming were likely to occur, resulting in poor durability.
The durability evaluation sample using the pressure-sensitive adhesive composition of Comparative Example 4 in which the content of the constituent unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B exceeds 4 mass% was measured under high temperature conditions. Or, when exposed to high temperature and high humidity conditions, peeling is likely to occur, resulting in poor durability. Further, the coating film formed from the pressure-sensitive adhesive composition of Comparative Example 4 did not have sufficient hardness.

From the pressure-sensitive adhesive compositions of Comparative Example 5 and Comparative Example 6 in which the absolute value of the difference between the solubility parameter of the (meth)acrylic copolymer A and the solubility parameter of the (meth)acrylic copolymer B exceeds 0.2 The formed coating film did not have sufficient hardness. Further, it was revealed that the durability evaluation samples using the pressure-sensitive adhesive compositions of Comparative Example 5 and Comparative Example 6 were liable to peel off when exposed to high temperature conditions and had poor durability.

The content ratio of the (meth)acrylic copolymer A to the (meth)acrylic copolymer B is less than 60/40 on a mass basis, and the pressure-sensitive adhesive composition of Comparative Example 7 and the comparative example exceeding 95/5. It was revealed that the durability evaluation sample using the pressure-sensitive adhesive composition of 8 was liable to peel off when exposed to high temperature conditions or high temperature and high humidity conditions, and was inferior in durability.
The durability evaluation sample using the pressure-sensitive adhesive composition of Comparative Example 9 containing no (meth)acrylic copolymer B was liable to peel off when exposed to high temperature conditions or high temperature and high humidity conditions. It became clear that it was inferior in sex.

The adhesive of Comparative Example 10 in which the content of the tolylene diisocyanate compound is less than 5 parts by mass based on 100 parts by mass of the total amount of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B. It was revealed that the processability evaluation sample using the composition was inferior in processability. Further, it has been revealed that when exposed to high temperature conditions, peeling easily occurs, resulting in poor durability.
The pressure-sensitive adhesive composition of Comparative Example 11 in which the content of the tolylene diisocyanate compound exceeds 30 parts by mass with respect to 100 parts by mass of the total amount of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B. The durability evaluation sample using the product could not be evaluated for durability because haze occurred.

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 12 containing a xylene diisocyanate-based compound instead of the tolylene diisocyanate-based compound was a (meth)acrylic copolymer (A and B) and a xylene diisocyanate-based compound. Since the compatibility was poor and haze occurred, the durability could not be evaluated.
Further, the coating film formed from the pressure-sensitive adhesive composition of Comparative Example 13 containing the hexamethylene diisocyanate compound instead of the tolylene diisocyanate compound did not have sufficient hardness.

Claims (5)

It has a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate, and the content of the structural unit derived from the monomer having a hydroxyl group is 0 with respect to all the structural units. .01 wt% to 0.3 wt% in the range der is, a weight average molecular weight area by der of 700,000 to 2,000,000 (meth) acrylic copolymer a,
It has a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth)acrylate, and the content of the structural unit derived from the monomer having a hydroxyl group is 0 with respect to all the structural units. range der .3 wt% to 4 wt% is, Ru der weight average molecular weight of from 700,000 to 2,000,000 and (meth) acrylic copolymer B,
A tolylene diisocyanate compound in the range of 5 to 30 parts by mass per 100 parts by mass of the total amount of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B;
A silane coupling agent in the range of 0.05 parts by mass to 1 part by mass based on 100 parts by mass of the total amount of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B;
Including
Structural unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer B with respect to the content ratio a of the structural unit derived from a monomer having a hydroxyl group in the (meth)acrylic copolymer A The ratio of the content rate b of is 10 to 100 on a mass basis,
The content ratio of the (meth)acrylic copolymer A to the (meth)acrylic copolymer B is in the range of 60/40 to 95/5 on a mass basis,
A pressure-sensitive adhesive composition, wherein the absolute value of the difference between the solubility parameter of the (meth)acrylic copolymer A and the solubility parameter of the (meth)acrylic copolymer B is 0.2 or less. In the (meth)acrylic copolymer A and the (meth)acrylic copolymer B, the content ratio of the structural unit derived from the monomer having a hydroxyl group is the (meth)acrylic copolymer A and The pressure-sensitive adhesive composition according to claim 1, which is in a range of 0.05 mass% to 1.5 mass% with respect to all the constituent units of the (meth)acrylic copolymer B. The pressure-sensitive adhesive composition according to claim 1 or 2 , wherein the tolylene diisocyanate compound is an adduct of tolylene diisocyanate and a polyol. The pressure-sensitive adhesive according to any one of claims 1 to 3 , wherein the value of storage elastic modulus G'at 30°C after crosslinking is in the range of 2.0 x 10 ⁵ Pa to 1.0 x 10 ⁷ Pa. Composition. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 4 .