TWI634188B - Adhesive and adhesive sheet - Google Patents

Abstract

Provided is an adhesive and an adhesive sheet excellent in both light leakage resistance and durability when applied to optical components such as a polarizing plate. The gel ratio of the adhesive is 45 to 90%, and the weight-average molecular weight of the sol portion measured by a gel permeation chromatography (GPC) method is 600,000 to 2.5 million. The adhesive preferably contains a first (meth) acrylate polymer (A) having a weight average molecular weight of 600,000 to 2.5 million, and a second (meth) acrylate having a weight average molecular weight of 8,000 to 300,000. A component obtained by crosslinking the polymer (B).

Description

Adhesive and adhesive sheet

The present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet, and particularly to a suitable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet for optical components such as a polarizing plate.

Generally, in a liquid crystal panel, an adhesive layer formed from an adhesive adhesive composition in which a polarizing plate and a retardation plate are adhered to a glass substrate or the like is often used. However, optical components such as polarizers and retardation plates are liable to shrink due to heat and the like, and shrinkage due to thermal changes occurs. As a result, the base adhesive layer laminated on the optical component cannot follow the shrinkage, and peeling occurs at the interface ( The so-called floating and peeling) causes the problem of light leakage (so-called white spots) due to the deviation of the optical axis of the optical component caused by the stress when the optical component shrinks.

As a method for preventing this problem, (1) a method of suppressing the optical component itself by adhering an adhesive layer having high adhesive force and excellent form stability to an optical component such as a polarizing plate, Alternatively, (2) a method using an adhesive layer in which the stress during shrinkage of the optical component is small. As the method (1), as shown in Patent Document 1, it is effective to use an adhesive layer having a high storage modulus. On the other hand, as a method of (2), it is effective to use an adhesive layer which is excellent in the stress relaxation rate which can flexibly respond to the deformation of an optical member. However, conventionally, in order to form such an adhesive layer having an excellent stress relaxation ratio, it is necessary to set the crosslinking density in the adhesive layer to be low. In this way, There is a problem that the strength of the adhesive layer itself becomes low and the durability becomes poor.

Therefore, in Patent Documents 2 to 4, instead of setting the crosslinking density of the adhesive layer low, plasticizers, flowing paraffin, urethane elastomers, and the like are added to the acrylic adhesive, and the resulting adhesives are made. The composition is moderately soft, and the stress relaxation rate is imparted to the adhesive layer, so that light leakage resistance and durability are desired.

[Patent Document 1] JP 2006-235568

[Patent Document 2] Japanese Unexamined Patent Publication No. 5-45517

[Patent Document 3] Japanese Unexamined Patent Publication No. 9-137143

[Patent Document 4] JP 2005-194366

However, if a plasticizer or a flowing paraffin adhesive composition is added, the formed adhesive layer will ooze out of the plasticizer and the flowing paraffin with time. In addition, due to this, the adhesion durability becomes low, the liquid crystal cell of the adherend is contaminated, and the like, and various problems are worrying me. In addition, if the adhesive composition to which the urethane elastomer is added is intended to maintain compatibility, the amount of the urethane elastomer added has an upper limit, and the improvement of the stress relaxation rate tends to be insufficient. Further, in order to increase the stress relaxation rate, if the amount of the urethane elastomer is increased, the compatibility with the acrylic adhesive becomes low, and problems such as turbidity occur. As described above, in the conventional technology, it is difficult to fundamentally improve the light leakage resistance and durability of an adhesive layer formed of an adhesive composition.

The present invention has been made in view of this. An object of the present invention is to provide an adhesive and an adhesive sheet excellent in both light leakage resistance and durability when applied to optical components such as polarizing plates.

In order to achieve the above object, the first, the present invention, a formula An adhesive having a gel ratio of 45 to 90% and a weight average molecular weight of 600,000 to 2.5 million measured by a gel permeation chromatography (GPC) method of the sol portion (Invention 1).

The adhesive of the said invention (invention 1) contains the sol part which has a predetermined gel ratio and predetermined molecular weight, and can have the outstanding stress relaxation rate. When the adhesive having such an excellent stress relaxation rate is used for an optical component such as a polarizing plate, an adhesive sheet excellent in both light leakage resistance and durability can be obtained.

In the above invention (Invention 1), the first (meth) acrylate polymer (A) having a weight average molecular weight of 600,000 to 2.5 million and the second (a) having a weight average molecular weight of 8,000 to 300,000 are preferred. Base) A component obtained by crosslinking an acrylate polymer (B) (Invention 2).

In the above invention (Invention 2), it is preferable that the ratio of the second (meth) acrylate polymer (B) to 100 parts by mass of the first (meth) acrylate polymer (A) is 5 to 50. Parts by mass (Invention 3).

In the above-mentioned inventions (Inventions 2, 3), it is preferable that the second (meth) acrylate polymer (B) before crosslinking is used, and as a constituent, the monomer containing a reactive functional group exceeds 1% by mass Super, less than 50% by mass (Invention 4).

In the above invention (Invention 4), it is preferred that the second (meth) acrylate polymer (B) is reacted with the reactive functional group and a crosslinkable agent (C) having a reactive crosslinkable group. Thereby, it is crosslinked (Invention 5).

Secondly, the present invention is an adhesive sheet having a substrate and an adhesive layer, and the adhesive layer is formed of the adhesive (Inventions 1 to 5) (Invention 6).

In the above invention (Invention 6), the substrate is preferably an optical member (Invention 7).

Third, the present invention is an adhesive sheet having two release sheets and an adhesive layer held by the two release sheets, so that the adhesive layer is in contact with the two release sheets, and is characterized by the adhesive layer It consists of the said adhesive agent (inventions 1 to 5) (invention 8).

The adhesive of the present invention has a sol portion having a predetermined gel ratio and a predetermined molecular weight, and thus can exhibit an excellent stress relaxation ratio. When the adhesive having such an excellent stress relaxation rate is used for an optical component such as a polarizing plate, an adhesive sheet excellent in both light leakage resistance and durability can be obtained.

1A, 1B ‧‧‧ Adhesive Sheet

11‧‧‧ Adhesive layer

12, 12a, 12b ‧‧‧ peeling sheet

13‧‧‧ substrate

Fig. 1 is a sectional view of an adhesive sheet according to a first embodiment of the present invention.

Fig. 2 is a sectional view of an adhesive sheet according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a measurement field of a light leakage resistance test in a polarizing plate with an adhesive layer attached.

FIG. 4 is a diagram showing evaluation criteria for a light leakage resistance test (visual inspection) in a polarizer with an adhesive layer.

Hereinafter, embodiments of the present invention will be described.

[Adhesive]

The adhesive of this embodiment has a gel ratio of 45 to 90%, preferably 50. To 80%, especially good 55 to 70%.

If the adhesive of the present embodiment has a gel ratio, that is, a degree of crosslinking, within the above-mentioned range, the three-dimensional network structure formed by the crosslinking can be formed well and has an appropriate cohesive force. This makes it possible to obtain an adhesive sheet having excellent durability when the optical component is applied. The gel ratio of the adhesive is a value at the time of sticking (after the aging period has elapsed). Specifically, the adhesive composition was applied to a release sheet, and the gelation ratio after storage for 7 days in an environment of 23 ° C. and 50% RH after heat treatment. The gel ratio of the adhesive varies before the aging period elapses. From this point of view, if the aging period is unknown, it can be stored in an environment of 23 ° C. and 50% RH for 7 days, and the gel ratio may be within the above range.

In addition, in the adhesive according to this embodiment, the weight average molecular weight (Mw; polystyrene equivalent) measured by the gel permeation chromatography (GPC) method of the sol portion is 600,000 to 2.5 million, preferably 800 to 2.2 million, and particularly preferably 1 to 2 million. As described above, the sol portion is a relatively large weight average molecular weight, and the three-dimensional network structure formed by crosslinking has a high degree of freedom in forming a polymer compound (high molecular weight component), and the stress relaxation rate of the adhesive is excellent. This will be described in detail below.

In the adhesive of this embodiment, the low molecular weight component forms a three-dimensional network structure through a chemically crosslinked structure (estimated). Therefore, a low molecular weight component can hardly be extracted from a sol part. On the other hand, the high-molecular-weight component has a pseudo-crosslinked state (presumably) in the three-dimensional network structure, which is inserted with almost no chemical crosslinking. That is, high molecular weight polymers are not constrained with chemical cross-linking, but are mutually constrained (estimated) between the three-dimensional network structures described above. thus, The adhesive of this embodiment has the above-mentioned high-molecular-weight component with a high degree of freedom, and has an excellent stress relaxation rate compared with the conventional adhesive having only a chemically crosslinked structure. On the other hand, since the above-mentioned polymer components do not have a chemical cross-linked structure, but are mutually constrained, they have suitable cohesive force (estimated).

Here, as in the case of the measurement of the sol portion, as in the state where the adhesive of the present embodiment is immersed in a solvent, the above-mentioned three-dimensional network structure swells, and the network is widened (estimated). Furthermore, high-molecular-weight components have increased degrees of freedom due to the presence of a solvent. In addition, a part of the high molecular weight component is extracted from the above-mentioned three-dimensional network structure (presumably) because it does not have a chemical cross-linked structure. As a result, the sol portion turned to the high molecular weight side (estimated), as is characteristic of this embodiment.

For this reason, even if a low molecular weight component of a plasticizer is added to a general adhesive, the high molecular weight component is intertwined with each other and the chemical cross-linking structure is difficult to dissolve as a sol portion. The low molecular weight side of the molecular weight distribution is eluted as a sol portion. Suffice it to say that in the conventional adhesives, the sol portion has a high molecular weight as in this embodiment, and it is considered that it is only possible when the gel ratio is relatively low. That is, unlike the present embodiment, while having a predetermined gel ratio, the sol portion has a relatively high molecular weight as described above. It can be said that it is a very specific phenomenon that has never been seen in past adhesives.

Here, if the weight-average molecular weight of the sol portion is less than 600,000, there may not be an adhesive with a high molecular weight component insertion (presumed) structure in the three-dimensional network structure formed by the low molecular weight components as described above, or, In the case of an adhesive having an estimated structure, the molecular weight of the high molecular weight component is too small, and The pseudo-crosslinked state due to the three-dimensional network structure is not sufficiently formed (presumably). Thus, under the use conditions of sticking to a liquid crystal cell or the like, high-molecular-weight components ooze out of the adhesive over time. As a result, durability is low, and contamination with the adherend results in poor reusability. On the other hand, when the weight-average molecular weight of the sol portion exceeds 2.5 million, the compatibility with the three-dimensional network structure formed by cross-linking is deteriorated, and the Haze value is increased, and durability and the like are deteriorated. Possible.

The molecular weight distribution (Mw / Mn) of the sol portion is preferably from 1 to 20, particularly preferably from 1.5 to 5, and more preferably from 2.5 to 4.0. When the molecular weight distribution (Mw / Mn) exceeds 20, there will be more low-molecular-weight components in the sol portion. In practical use, particularly, the low-molecular-weight components will preferentially bleed out, and durability and the like will deteriorate.

The adhesive of this embodiment has the above-mentioned gel ratio and the sol portion having the above-mentioned molecular weight, and thereby can exhibit an appropriate cohesive force and an excellent stress relaxation rate. When an adhesive having such characteristics is used, it is possible to obtain an adhesive sheet excellent in both light leakage resistance and durability when applied to optical components such as polarizing plates.

It is preferable that the pressure-sensitive adhesive having the above-mentioned characteristics includes the first (meth) acrylate polymer (A) having a weight average molecular weight of 600,000 to 2.5 million and the second having a weight average molecular weight of 8,000 to 300,000. The (meth) acrylate polymer (B) is obtained as a component adhesive agent. In addition, in this specification, (meth) acrylate means both of an acrylate and a methacrylate. The same applies to other similar terms. In addition, "polymer" also includes the concept of "copolymer".

The above-mentioned adhesive preferably contains a first (meth) acrylate polymer (A) having a weight average molecular weight of 600,000 to 2.5 million and a second (meth) having a weight average molecular weight of 8,000 to 300,000. The adhesive composition of the acrylate polymer (B) and the crosslinking agent (C) is particularly preferably an adhesive composition further containing a silane coupling agent (D), and is obtained by crosslinking. Among the above-mentioned adhesives, a conventional low molecular weight polymer used as a plasticizer has a three-dimensional network structure formed by chemical crosslinking. In addition, in this three-dimensional network structure, a plurality of high-molecular-weight polymers are inserted, and high-molecular-weight polymers are constrained, and a pseudo-crosslinked structure between high-molecular-weight polymers is formed. Thereby, a high molecular weight adhesive having a relatively high sol fraction while having a predetermined gel ratio can be obtained. The obtained adhesive can exhibit suitable cohesive force and excellent stress relaxation rate based on the above-mentioned estimated structure. Hereinafter, the said adhesive composition is demonstrated.

The second (meth) acrylate polymer (B), (1) uses a monomer having a functional group (b1) capable of reacting with the crosslinking agent (C) as a constituent, and the polymer (B) contains The cross-linking agent (C) and the reactive functional group are substantially only functional groups (b1), and (2) preferably has a functional group having reactivity with the cross-linking agent (C) so as to satisfy the following formula (I) A monomer of (b1) and a monomer having a functional group (b2) having reactivity with the cross-linking agent (C) satisfying the following formula (I) are preferred as constituent components.

Reactivity with cross-linking agent (C): functional group (b2) <functional group (b1) ‧‧‧ (I)

That is, in the polymer (B) of (2), the reactivity of the functional group (b1) with the cross-linking agent (C) is preferably higher than that of the functional group (b2) with the cross-linking agent (C). Sex is high.

The (meth) acrylate polymer (A) or (B) is an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group, and contains a function capable of reacting with the crosslinking agent (C). Copolymer of other monomers (monomers containing a reactive functional group) and other monomers used as necessary. The first (meth) acrylate polymer (A) also preferably does not contain a monomer having the above-mentioned reactive functional group.

Alkyl (meth) acrylates having 1 to 20 carbon atoms as the alkyl group, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (formyl) N-butyl acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Isooctyl (meth) acrylate, n-Cylyl (meth) acrylate, n-lauryl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate Alkanoyl esters, stearyl (meth) acrylate, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

On the other hand, as the monomer containing a reactive functional group, a monomer having a hydroxyl group in the molecule (a monomer containing a hydroxyl group), a monomer having a carboxyl group in the molecule (a monomer containing a carboxyl group), and a monomer having an amino group in the molecule A monomer (an amino group-containing monomer) and the like are preferable.

Examples of the hydroxyl-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) (Meth) acrylic acid such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. Hydroxyalkyl enoates and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the amino-containing monomer include aminoethyl (meth) acrylate and n-butyl aminoethyl (meth) acrylate. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Furthermore, examples of the other monomers include (meth) acrylates having an aliphatic ring such as cyclohexyl (meth) acrylate, and aromatic rings such as a phenyl (meth) acrylate. (Meth) acrylic acid esters, non-crosslinkable acrylic acid amides such as acrylic acid amide, methacrylamide, N, N-dimethylaminoethyl (meth) acrylate, N (meth) acrylic acid, Non-crosslinkable tertiary amino (meth) acrylates such as N-dimethylaminopropyl ester, vinyl acetate, styrene, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The reactive functional group (a1) -containing monomer used for the first (meth) acrylate polymer (A) and the reactive functional group-containing (for the second (meth) acrylate polymer (B)) b1) The selection of the monomer is determined based on the relationship with the crosslinking agent (C) and the reactivity. The details are described below.

Here, it is preferable that the second (meth) acrylate polymer (B) contains a monomer having the above-mentioned reactive functional group (b1), exceeds 1% by mass, and its upper limit is less than 50% by mass. Preferably, it contains 5 to 30% by mass of the monomer having the above-mentioned reactive functional group (b1), and particularly preferably contains 10 to 20% by mass, more preferably The content is preferably 12 to 18% by mass. By making the reactive functional group (b1) -containing monomer within the above range, the degree of cross-linking of the second (meth) acrylate polymer (B) becomes good, and it is compatible with the first (meth) acrylate The combination of the polymer (A) sets the gel ratio of the obtained adhesive to a predetermined range, and the weight-average molecular weight of the sol portion is within the predetermined range. As a result, the obtained adhesive has an appropriate cohesive force and has an excellent stress relaxation rate. When the content of the reactive functional group (b1) -containing monomer is 1% by mass or less, the crosslinking of the second (meth) acrylate polymer (B) is insufficient, and the gel ratio is below a predetermined range. There is a possibility that the durability becomes lower. On the other hand, the content of the reactive functional group (b1) -containing monomer is 50% by mass or more, and the compatibility with other components (for example, the first (meth) acrylate polymer (A)) is deteriorated. . As a result, the pseudo-crosslinked structure described above cannot be sufficiently formed, and durability is lowered. In addition, if the upper limit of the content of the reactive functional group (b1) -containing monomer is 30% by mass, the light leakage resistance of the obtained adhesive sheet is more excellent.

The "substantially functional group is only (b1)" in the polymer (B) of the above (1), which refers to other functional groups in which the gum reacts with the crosslinker (C), and does not interfere with the functional group (b1) and cross-linking. The degree of reactivity of the crosslinking agent (C) is tolerable (in this case, the polymer (B) of (1) and the polymer (B) and repeating of (2)). That is, the second (meth) acrylate polymer (B) does not contain a monomer having a functional group (b2) having a lower reactivity than the functional group (b1) and the crosslinking agent (C) (containing a reactive function (Monomer of group (b2)) is particularly preferred as a constituent. However, when the monomer containing a reactive functional group (b2) is contained as a constituent, the reactive functional group (b1) is contained as a mass ratio. The content of the monomer is preferably 1/5 or less, and particularly preferably 1/10 or less.

When the second (meth) acrylate polymer (B) has a mass ratio of the monomer containing the reactive functional group (b2) exceeding 1/5 of the content of the monomer containing the reactive functional group (b1), The durability of the obtained adhesive layer becomes low. If there are too many reactive functional groups (b2) in the second (meth) acrylate polymer (B), the three-dimensional network structure formed therein also has a large excess of reactive functional groups (b2). The compatibility between the structure and the first (meth) acrylate polymer (A) is changed (estimated). As a result, the first (meth) acrylate polymer (A) in the three-dimensional network structure cannot be sufficiently inserted, and the gel ratio becomes lower than a predetermined range. In addition, the reactive functional group (b2) is a large amount of the remaining three-dimensional network structure, and the mobility of the first (meth) acrylate polymer (A) inserted into the three-dimensional network structure is excessively restricted (estimated) . As a result, durability deteriorates.

Here, the second (meth) acrylate polymer obtained by polymerizing a (meth) acrylic acid alkyl ester having a carbon number of 1 to 20, a crosslinking agent (C), and a monomer having a reactive functional group. The polymerized form of (B) may be a random copolymer or a block copolymer.

In this embodiment, the 2nd (meth) acrylate polymer (B) mentioned above may be used individually by 1 type, and may be used in combination of 2 or more type.

The weight average molecular weight of the second (meth) acrylate polymer (B) is preferably 8,000 to 300,000, particularly preferably 10,000 to 200,000, and more preferably 50,000 to 100,000. That is, the second (meth) acrylate polymer (B) is a low molecular weight polymer component. In addition, the weight average molecular weight in this specification is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

When the weight average molecular weight of the second (meth) acrylate polymer (B) is within the above range, a three-dimensional network structure unique to the adhesive composition of this embodiment is formed, which is advantageous and has an excellent stress relaxation rate. That is, if the weight average molecular weight of the second (meth) acrylate polymer (B) is less than 8,000, a good three-dimensional network structure cannot be obtained, and the gel ratio is lower than a predetermined range. On the other hand, the weight average molecular weight of the second (meth) acrylate polymer (B) exceeds 300,000, the compatibility decreases, and the polymer (A) in the three-dimensional network structure formed by the polymer (B) Insufficient insertion may cause the gel ratio to fall below a predetermined range. As a result, durability and reusability may be deteriorated.

It is preferable that the 1st (meth) acrylate polymer (A) does not contain the monomer which has a functional group which reacts with the crosslinking agent (C) as a component, or contains the monomer which has a 2nd (meth) acrylic acid The monomer of the above-mentioned functional group (b1) of the ester polymer (B) and the cross-linking agent (C) is a monomer having a low functional group (a1) as a constituent component. b1) A monomer having a highly reactive functional group with the crosslinking agent (C) is used as a constituent.

The 1st (meth) acrylate polymer (A) may not contain the monomer which has a functional group which reacts with a crosslinking agent (C). However, a monomer containing a reactive functional group (a1) having a lower reactivity than the reactive functional group (b1) of the second (meth) acrylate polymer (B) (containing a reactive functional group (a1) When a monomer is contained, it is preferable. When the polymer (A) contains a reactive functional group (a1), the reaction between the second (meth) acrylate polymer (B) and the crosslinking agent (C) can be promoted, or a silane coupling agent ( In the case of D), the reactive functional group (a1) of the first (meth) acrylate polymer (A) is reacted with the silane coupling agent (D), and the resulting adhesive is bonded to the liquid crystal monomer. The adhesion durability of the glass surface of the element will be further improved, so there are better occasions.

When the first (meth) acrylate polymer (A) contains a monomer having the above-mentioned reactive functional group (a1), the content thereof is usually 20% by mass or less, preferably 15% by mass or less, and 10% by mass % Is particularly preferred. If the content of the reactive functional group (a1) -containing monomer exceeds 20% by mass, the glass transition temperature (Tg) of the first (meth) acrylate polymer (A) is too high, and the obtained adhesive may not be obtained. Possible stress relaxation rate. From the viewpoint of providing reusability of the adhesive, the content of the reactive functional group (a1) -containing monomer is preferably 15% by mass or less.

In addition, in comparison with the second (meth) acrylate polymer (B) containing a monomer having a reactive functional group (b1), the reactivity contained in the first (meth) acrylate polymer (A) The ratio of the monomer of the functional group (a1) in the first (meth) acrylate polymer (A) to the reactive functional group (b1) in the second (meth) acrylate polymer (B) It is preferable that the ratio of the monomers of) in the second (meth) acrylate polymer (B) is small. Accordingly, the reaction between the reactive functional group (a1) and the crosslinking agent (C) contained in the first (meth) acrylate polymer (A) is suppressed, and the second (meth) acrylate polymer (B ) The reactive functional group (b1) and the cross-linking agent (C) contained can perform a reliable reaction. Thus, the gel ratio of the obtained adhesive and the weight average molecular weight of the sol portion are within predetermined values.

The 1st (meth) acrylate polymer (A) does not contain the reactivity with the crosslinking agent (C) in the molecule and the reactive functional group of the 2nd (meth) acrylate polymer (B) ( b1) monomers with equivalent or more functional groups are When it is contained, the content of the functional group monomer contained in the molecule is preferably 1% by mass or less in the polymer (A), and particularly preferably 0.5% by mass or less. When the content of the monomer exceeds 1% by mass, the reaction between the second (meth) acrylate polymer (B) and the cross-linking agent (C) that should be preferentially reacted may be hindered.

Here, the polymerized form of the first (meth) acrylate polymer (A) obtained by polymerizing an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group and a monomer containing a reactive functional group, Random copolymers are also possible, as are block copolymers.

In this embodiment, the 1st (meth) acrylate polymer (A) mentioned above may be used individually by 1 type, and may be used in combination of 2 or more type.

The weight average molecular weight of the 1st (meth) acrylate polymer (A) is preferably 600,000 to 2.5 million, particularly preferably 800,000 to 2.2 million, and more preferably 1 to 2 million. That is, the 1st (meth) acrylate polymer (A) is a high molecular weight polymer component.

When the weight average molecular weight of the first (meth) acrylate polymer (A) is within the above range, the first (meth) in the three-dimensional network structure formed by the second (meth) acrylate polymer (B) The acrylate polymer (A) can be inserted well, and two or more of the polymers (A) are constrained (presumably) in a state of a certain degree of freedom with a pseudo-crosslinked structure as a medium. In addition, the polymer (A) has a relatively large molecular weight as described above, and the three-dimensional network structure formed between the polymers (B) has a high degree of freedom as a molecular chain while maintaining a pseudo-crosslinked state. As a result, the formed adhesive has suitable cohesive force and excellent stress relaxation rate. As a result, it has excellent light leakage resistance. In addition, the adhesive durability under high temperature conditions is also sufficient, and it is possible to prevent floating and peeling.

Here, when the weight average molecular weight of the 1st (meth) acrylate polymer (A) is less than 600,000, when the formation of the above-mentioned pseudo-crosslinked structure is insufficient, the gel of the adhesive obtained is obtained. The ratio is lower than the predetermined range, and durability and reusability may be deteriorated. In addition, when the weight average molecular weight of the first (meth) acrylate polymer (A) exceeds 2.5 million, compatibility with the second (meth) acrylate polymer (B) and the like is deteriorated, and Haze (Haze) ) Value rises, and the required stress relaxation rate may not be obtained.

For 100 parts by mass of the first (meth) acrylate polymer (A), the ratio of the second (meth) acrylate polymer (B) is preferably 5 to 50 parts by mass, and more preferably 5 to 40 parts by mass. 10 to 30 parts by mass are particularly preferred.

An adhesive obtained from an adhesive composition having the above-mentioned ratio containing the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B), wherein the second (methyl ) The acrylate polymer (B) (low molecular weight polymer) uses the crosslinking agent (C) as a medium to form a three-dimensional network structure, and the three-dimensional network structure is the first (meth) acrylate polymer (A) (High molecular weight polymer) Two or more molecules are inserted structures, and the polymers (A) form a constrained pseudo-crosslinked structure in a state of a certain degree of freedom (presumably). The adhesive thus obtained had a gel ratio in a predetermined range, and the weight average molecular weight of the sol portion was in a predetermined range. In addition, such conditions satisfy the adhesive, and it is considered that the above-mentioned estimated structure is obtained. As a result, it has both an appropriate cohesive force and an excellent stress relaxation rate. Thereby, the obtained adhesive is excellent in durability and light leakage resistance.

As the crosslinking agent (C), an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a metal chelate-based crosslinking agent, and the like are preferred.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as benzylidene diisocyanate, diphenylmethane diisocyanate, and p-xylyl diisocyanate; aliphatic polyisocyanates such as cyclohexylene diisocyanate; and isoflurane diketone. Ester ring polyisocyanates such as isocyanates and hydrogenated diphenylmethane diisocyanates, etc., and these biuret bodies, isocyanurates, and further ethylene glycol, propylene glycol, neopentyl glycol, and trimethylol Adducts of low molecular active hydrogen-containing compounds such as propane and castor oil.

Examples of the epoxy-based crosslinking agent include 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane, N, N, N ', N'-tetraglycidyl m- P-xylyl diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidyl Amine, etc.

Examples of the aziridine-based cross-linking agent include diphenylmethane 4,4'-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinepropionate, Tetramethylolmethane tri-beta-azapropanepropionate, toluene 2,4-bis (1-azacyclopropanecarboxamide), triethylene melamine, bisisoisoxyldimethyl 1- ( 2-methylazacyclopropane), tri- (2-methylazacyclopropane) phosphine, trimethylolpropane tri-β- (2-methylazacyclopropane) propionate, and the like.

Among the metal chelate-based cross-linking agents, there are chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin and the like, and aluminum chelate compounds are preferred from the viewpoint of performance. As the aluminum chelate compound, for example, aluminum diisopropoxide monooleyl acetoacetate Acid salt, aluminum monoisopropoxy acetoacetate, aluminum monoisopropoxy monooleate monoethyl acetoacetate, aluminum diisopropoxy monolaurate acetoacetate, aluminum diisopropoxy Monostearyl acetoacetate, aluminum diisopropoxy monoisostearyl acetoacetate, and the like.

The content of the cross-linking agent (C) is a reactive functional group (b1) of the cross-linkable group (for example, an isocyanate group) to the second (meth) acrylate polymer (B) of the cross-linking agent (C). ) (For example, a hydroxyl group) is usually an amount of 0.05 to 5 equivalents, preferably an amount of 0.1 to 3.5 equivalents, and particularly preferably an amount of 0.3 to 1.0 equivalents. When the amount of the crosslinkable group is less than 0.1 equivalent, the gel ratio of the adhesive obtained may be less than 45%, and sufficient cohesive force may not be exhibited. When the amount of the crosslinkable group is 0.3 equivalent or more, the durability of the obtained adhesive is excellent. On the other hand, when the amount of the crosslinkable group is 3.5 equivalents or less, the reusability of the obtained adhesive is excellent. When the amount is 1.0 equivalent or less, the crosslinker (C) is used only with the reactive functional group (b1). ) Reaction, it is possible to obtain an adhesive with excellent stress relaxation rate.

In addition, in the present embodiment, the cross-linking agent (C) may be a cross-linking agent whose cross-linking relationship with both the reactive functional group (b1) and the reactive functional group (a1) is consistent. And use. From the viewpoint that the control of the three-dimensional network structure formed by the second (meth) acrylate polymer (B) is easy, for example, it is preferable to use only one type of crosslinking agent, as in the case of using only an isocyanate-based crosslinking agent. Furthermore, it is particularly preferable to use only one crosslinking agent as a compound.

Here, regarding the combination of the crosslinking agent (C) and the (meth) acrylate polymer (A) and (B) a monomer having a reactive functional group, the crosslinking agent (C) is an isocyanate-based crosslinking agent. In the case of polymer (A) The monomer of the reactive functional group (a1) is a monomer containing a carboxyl group, and as the reactive functional group (b1) monomer containing the polymer (B), a monomer containing a hydroxyl group or a monomer containing an amino group is preferred.

On the other hand, when the cross-linking agent (C) is an epoxy-based cross-linking agent, an aziridine-based cross-linking agent, or a metal chelate-based cross-linking agent, as a reactive functional group containing the polymer (A) ( The monomer of a1) is preferably a monomer containing a hydroxyl group, and a monomer containing a reactive functional group as the polymer (B) is more preferably a monomer containing a carboxyl group.

From the flexibility of the bond formed between the cross-linking agent (C) and the polymer (B) and the stability of the cross-linking reaction, further, from the reactive group of the polymer (A) and the silane coupling agent (D) A suitable reaction proceeds from the viewpoint of improving the cohesive force of the obtained adhesive. The crosslinking agent (C) is an isocyanate-based crosslinking agent, and the monomer containing the reactive functional group (a1) of the polymer (A) contains The monomer having a carboxyl group, the reactive functional group (b1) monomer containing the polymer (B) is a monomer containing a hydroxyl group, and it is particularly preferred that the monomer containing a reactive functional group (b2) is not used.

The adhesive composition of the present embodiment preferably further contains a silane coupling agent (D). If the silane coupling agent (D) is contained, when the first (meth) acrylate polymer (A) has a carboxyl group, the organic reactive group of the silane coupling agent (D) and the first (methyl) ) The carboxyl group of the acrylate polymer (A) reacts. On the other hand, the alkoxysilyl group of the silane coupling agent (D) acts on the adhered surface of the glass substrate or the like. Thus, for example, when the polarizing plate is bonded to a liquid crystal glass cell or the like, the adhesion between the adhesive and the liquid crystal glass cell is further improved.

As the silane coupling agent (D), there is at least one in the molecule The alkoxysilyl organosilicon compound has good compatibility with the adhesive components and has light transmittance. For example, a substance that is substantially transparent is suitable. The addition amount of such a silane coupling agent (D) is preferably 0.01 to 0.5 parts by mass, and particularly preferably 0.05 to 0.3 parts by mass, based on 100 parts by mass of the first (meth) acrylate polymer (A).

Specific examples of the silane coupling agent (D) include polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, and the like. Compounds, silicon compounds with epoxy structures such as 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethyl Amino-containing groups such as oxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Silicon compounds, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, etc. These may be used individually by 1 type, and may be used in combination of 2 or more type.

In the above adhesive composition, various additives commonly used in acrylic adhesives can be added as needed, such as adhesion-imparting agents, oxidation inhibitors, ultraviolet absorbers, light stabilizers, softeners, fillers, and antistatic agents. Refractive index adjuster, etc.

The above-mentioned adhesive composition may be mixed with a first (meth) acrylate polymer (A) and a second (meth) acrylate polymer (B), and a crosslinking agent (C) and Silane coupling agent (D) as required.

As a preferable specific example, (meth) acrylate polymers (A) and (B) can be prepared by a normal radical polymerization method. (Meth) acrylic The acrylate polymer (A) and (B) can be polymerized by a solution polymerization method using a polymerization initiator as necessary. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used in combination.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), and 1,1'-azobis (cyclohexane). 1-nitrile), 2,2'-azobis (2,4-dimethylnitrile), 2,2'-azobis (2,4-dimethyl4-methoxynitrile), dimethyl 2,2'-azobis (2-methylpropionic acid), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropane) Nitrile), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] and the like.

Examples of the organic peroxide include benzoyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, and di-n-peroxydicarbonate. Propyl ester, bis (2-ethoxyethyl) peroxydicarbonate, t-butylperoxyneodecanoate, t-butyl peroxybate butylperoxypyvalate), (3,5,5-trimethylcyclopentanone) peroxide, dipropionyl peroxide, and diacetyl peroxide.

Next, the obtained solutions of the polymers (A) and (B) are mixed, and a dilution solvent is added. Thereafter, a cross-linking agent (C) and a silane coupling agent (D) as necessary are added and mixed well to obtain an adhesive composition (coating solution) diluted with a solvent.

The diluent solvent used to make the coating solution diluted by the adhesive composition may be aliphatic hydrocarbons such as hexane, heptane, cyclohexane, toluene, dimethyl Aromatic hydrocarbons such as benzene, halogenated hydrocarbons such as dichloromethane, dichloroethane, alcohols such as methanol, ethanol, propanol, butanol, 1-methoxy 2-propanol, acetone, methylethyl Ketones, ketones such as 2-pentanol, isoflurane, and cyclopentanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as the coating solution can be applied, and may be appropriately selected according to the situation. For example, the concentration of the adhesive composition may be diluted to 10 to 40% by mass. In addition, when a coating solution is obtained, the addition of a diluent solvent or the like is not necessary, and the diluent solvent may not be added as long as the adhesive composition has a viscosity that can be applied. In this case, the adhesive composition can be used as it is as a coating solution.

The above-mentioned adhesive is obtained by crosslinking the above-mentioned adhesive composition. The crosslinking of the adhesive composition can be performed by heat treatment. In addition, this heat treatment can also be used as a volatilization drying treatment such as a diluent solvent for the adhesive composition.

When heat treatment is performed, the heating temperature is preferably 50 to 150 ° C, and more preferably 70 to 120 ° C. The heating time is preferably 30 seconds to 3 minutes, and particularly preferably 50 seconds to 2 minutes. Furthermore, after the heat treatment, it is particularly preferable to set a maturation period of about 1 to 2 weeks at normal temperature (for example, 23 ° C, 50% RH).

The heat treatment (and maturation) described above cross-links the second (meth) acrylate polymer (B) with the cross-linking agent (C) to form a dense three-dimensional network structure (presumably). In addition, the polymer (A) is constrained when two or more molecules of the first (meth) acrylate polymer (A) are inserted in the three-dimensional network structure without direct chemical bonds or with few chemical bonds. , Forming a pseudo-crosslinked structure (presumably). The first (meth) acrylate polymer (A) is When it has a carboxyl group, the 1st (meth) acrylate polymer (A) reacts with a silane coupling agent (D), and the adhesive durability of the obtained adhesive to a glass substrate, such as a liquid crystal cell, can be improved.

The adhesive described above is preferably used as an optical component. For example, it is suitable to adhere to a polarizing plate and a retardation plate, or to adhere a polarizing plate (a polarizing film) and a retardation plate (a retardation film) to a glass substrate. . The adhesive layer formed by the above-mentioned adhesive has a very good stress relaxation rate. Even when the size of the adherend changes greatly, the stress caused by the dimensional change will be absorbed and relaxed by the adhesive layer, so it is not long-term. It can be peeled off from the adherend, and at the same time, when the above-mentioned optical component is used, light leakage can be effectively prevented. That is, the adhesive of this embodiment has good light leakage resistance and durability when used on optical components.

[Adhesive sheet]

As shown in FIG. 1, the pressure-sensitive adhesive sheet 1A of the first embodiment is formed from the release sheet 12 and the release sheet 12 with the adhesive layer 11 laminated on the peeling surface and the base material 13 laminated on the adhesive layer 11 in the order from the bottom to the top. Make up.

In addition, as shown in FIG. 2, the adhesive sheet 1B of the second embodiment is configured by an adhesive layer 11 held by the two release sheets 12 a and 12 b and the two release sheets 12 a and 12 b. The adhesive layer is in contact with the release surfaces of the two release sheets 12a and 12b. In addition, the release surface of a release sheet in this specification is any of the surface which has peelability in a release sheet, the surface which performed the peeling process, and the surface which shows peelability even if it does not perform a peeling process.

Regardless of the adhesive sheet 1A or 1B, the adhesive layer 11 is an adhesive formed by cross-linking the above-mentioned adhesive composition.

The thickness of the adhesive layer 11 is appropriately determined according to the purpose of use of the adhesive sheets 1A, 1B, and is usually in the range of 5 to 100 μm, preferably 10 to 60 μm. For example, optical components are used as an adhesive layer for polarizing plates. In the case of 10 to 50 μm, particularly 10 to 30 μm is preferred.

The base material 13 is not particularly limited, and any material used as a base material sheet of a general adhesive sheet can be used. For example, in addition to the required optical components, woven or non-woven fabrics using fibers such as rayon, acrylic, polyester, etc .; high-quality paper, cellophane, impregnated paper, coated paper, etc .; metals such as aluminum and copper Foils; foams such as urethane foam, polyethylene foam, etc .; polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; Cellulose film such as triacetyl cellulose; polyurethane film; polyethylene film; polypropylene film; polyvinyl chloride film; polyvinylidene chloride film; polyvinyl alcohol film; ethylene vinyl acetate copolymer film; Polystyrene films; polycarbonate films; acrylic resin films; polybornene resin films; plastic films such as cycloolefin resin films; laminates of two or more of these; and the like. Plastic film, uniaxial calendar or biaxial calendar can be used.

Examples of the optical component include a polarizer (a polarizing film), a polarizer, a retardation plate (a retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, and a liquid crystal polymer film. Among them, a polarizer (polarizing film) is easy to shrink and has a large dimensional change. From the viewpoint of light leakage resistance, it is suitable as an object of use of the adhesive (the above-mentioned adhesive layer 11) of the present embodiment.

The thickness of the substrate 13 varies depending on the type. For example, in the case of an optical component, it is usually 10 μm to 500 μm, and preferably 50 μm to 300 μm.

Examples of the release sheets 12, 12a, and 12b include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, and vinyl chloride copolymers. Film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer polymer resin film, ethylene (Meth) acrylic copolymer film, ethylene‧ (meth) acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. These crosslinked films can also be used. Furthermore, these laminated films may be used.

It is preferable to perform a peeling process on the peeling surface (particularly the adhesive layer 11 and the surface contact | connecting) of the said release sheet. Examples of the release agent used in the release treatment include alkyd-based, siloxane-based, fluororesin-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

The thickness of the release sheets 12, 12a, 12b is not particularly limited, but is usually about 20 to 150 μm.

The above-mentioned adhesive sheet 1A is produced by applying a solution (coating solution) containing the above-mentioned adhesive composition on the peeling surface of the release sheet 12 and heat-treating the adhesive layer 11 to form the adhesive layer 11. The base material 13 is laminated. After that, it is preferable to provide a ripening period. The conditions for heat treatment and ripening are as described above.

In addition, in the production of the adhesive sheet 1B, a coating solution containing the adhesive composition is applied to the release surface of one release sheet 12a (or 12b), and the heat treatment is performed to form the adhesive layer 11. The other surface of the adhesive layer 11 overlaps the release surface of the release sheet 12b (or 12a).

Examples of the method for applying the coating solution include a roll coating method, a blade coating method, a roll coating method, a blade coating method, a pressure coating method, and a gravure coating method.

Here, for example, in the manufacture of a liquid crystal display device composed of a liquid crystal cell and a polarizing plate, a polarizing plate is used as the base material 13 of the adhesive sheet 1A, the peeling sheet 12 of the adhesive sheet 1A, and the exposed adhesive layer 11 is attached to the liquid crystal cell. Just close.

In addition, for example, in the manufacture of a liquid crystal display device in which a retardation plate is disposed between a liquid crystal cell and a polarizing plate, as an example, first, the release sheet 12a (or 12b) on one side of the adhesive sheet 1B is peeled off, and the adhesive layer exposed by the adhesive sheet 1B 11 is attached to the retardation plate. Next, the release sheet 12 of the adhesive sheet 1A using a polarizing plate as the base material 13 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1A is bonded to the retardation plate. Further, the release sheet 12b (or 12a) on the other side is peeled from the adhesive layer 11 of the adhesive sheet 1B, and the adhesive layer 11 exposed by the adhesive sheet 1B and the liquid crystal cell are bonded.

The stress relaxation rate of the above adhesive sheets 1A, 1B and the adhesive layer 11 is very good. For example, when the polarizer is used for adhesion, the stress generated by the deformation of the polarizer is absorbed and relaxed by the adhesive layer 11. Therefore, excellent light leakage resistance and high durability can be exhibited (estimated).

The embodiments described above are described for easy understanding of the present invention, and the present invention is not limited thereto. Therefore, each of the elements disclosed in the above embodiments includes all design changes and equivalents that fall within the technical scope of the present invention.

For example, the release sheet 12 of the adhesive sheet 1A may be omitted, and any one of the release sheets 12a and 12b in the adhesive sheet 1B may be omitted.

[Example]

Hereinafter, the present invention will be further specifically described with examples and the like, and the scope of the present invention is not limited by these examples and the like.

[Example 1]

1. Preparation of polymer (A)

97.0 parts by mass of n-butyl acrylate, 3.0 parts by mass of acrylic acid, 200 parts by mass of ethyl acetate, and 2,2'- were added to a reaction vessel having a stirrer, a thermometer, a reflux cooler, a dropping device, and a nitrogen introduction tube. 0.08 parts by mass of azobisisobutyronitrile, and the air in the reaction vessel was replaced with nitrogen. While stirring in this nitrogen atmosphere, the reaction solution was heated to 60 ° C, and after 16 hours of reaction, it was cooled to room temperature. Here, a part of the obtained solution was subjected to GPC measurement by the following method, and the production of the polymer (A) having a weight average molecular weight of 1.5 million was confirmed.

2. Preparation of polymer (B)

85.0 parts by mass of n-butyl acrylate, 15.0 parts by mass of 2-hydroxyethyl acrylate, and 200 parts by mass of ethyl acetate were added to a reaction vessel having a stirrer, a thermometer, a reflux cooler, a dropping device, and a nitrogen introduction tube. 0.12 parts by mass of 2,2'-azobisisobutyronitrile and 0.3 parts by mass of 2-mercaptoethanol. The air in the reaction vessel was replaced with nitrogen. While stirring in this nitrogen atmosphere, the reaction solution was heated to 70 ° C, and after reacting for 6 hours, it was cooled to room temperature. Here, a part of the obtained solution was subjected to GPC measurement by the following method, and production of a polymer (B) having a weight average molecular weight of 60,000 was confirmed.

3. Preparation of adhesive composition

100 parts by mass of the polymer (A) obtained in the step (1) (solid Component conversion value) was mixed with 15 parts by mass (solid content conversion value) of the polymer (B) obtained in the step (2), and then 0.6 equivalent of the hydroxyl group of the polymer (B) was used as the crosslinking agent (C). Tribenzyl diisocyanate (TDI-based) adduct of Trimethylolpropane (manufactured by Japan Polyurethane Co., Ltd., trade name: CORONATE-L) was added in 2.21 parts by mass. Finally, as the silane coupling agent (D), 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd .: KBM403) was added, and the mixture was sufficiently stirred to obtain an adhesive composition Dilute the solution.

Table 1 shows the formulation of the adhesive composition. The details of abbreviations and the like described in Table 1 are as follows.

[Polymer (A) and (B)]

BA: n-butyl acrylate

AA: Acrylic

HEA: 2-hydroxyethyl acrylate

4HBA: 4-hydroxybutyl acrylate

[Plasticizer]

‧ADEKASIZER-C-8: Trimellitic ester plasticizer (tris (triethylhexyl) trimellitate) (manufactured by Asahi Denka Kogyo Co., Ltd., trade name: ADEKASIZER-C-8)

[Crosslinking agent (C)]

‧Isocyanate crosslinking agent

CORONATE-L: benzylidene diisocyanate adduct of trimethylolpropane (manufactured by Japan Polyurethane Co., Ltd., trade name: CORONATE-L)

TAKENATE-D-110N: xylene diisocyanate of trimethylolpropane Adducts (manufactured by Mitsui Chemical Polyurethane Co., Ltd., trade name: TAKENATE-D-110N)

‧Epoxy Crosslinking Agent

TETRAD-X: N, N, N ', N'-tetraglycidyl m-p-xylyldiamine (manufactured by Mitsubishi Gas Chemical Company, trade name: TETRAD-X)

[Silane coupling agent (D)]

KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM403")

KBE9007: 3-isocyanatepropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KB E9007")

The release-treated surface of a polyethylene terephthalate film on one side of which was subjected to a release treatment with a siloxane-based release agent (Lintec Corporation, SP-PET3811, thickness: 38 μm) was obtained. The diluted solution of the adhesive composition was applied so that the thickness after drying was 25 μm. The coating was performed with a doctor blade coater, and then heat treatment was performed at 90 ° C. for 1 minute to form an adhesive layer.

Next, a polarizing film with a disc liquid crystal layer is formed, the polarizing film and the viewing angle expanding film are integrated polarizing plates, and the adhesive layer and the disc liquid crystal layer are bonded together to make them contact each other at 23 ° C. It was aged for 7 days at 50% RH to obtain a polarizer with an adhesive layer.

[Examples 2 to 13, Comparative Examples 1 to 5]

The types and ratios of the monomers constituting the adhesive composition, the types and addition amounts of the plasticizer, the cross-linking agent, and the silane coupling agent, and the composition of the polymer (A) and the polymer (B) are shown in Table 1. A polarizing plate with an adhesive layer was produced in the same manner as in Example 1 except that it was changed as shown.

Here, the above-mentioned weight average molecular weight (Mw) is permeated with a gel Permeation chromatography (GPC) measured the polystyrene-equivalent weight average molecular weight (GPC measurement) under the following conditions.

<Measurement conditions>

‧GPC measurement device: manufactured by Tosoh Corporation, HLC-8020

‧GPC column (passed in the following order): made by Tosoh

TSK guard column HXL-H

TSK gel GMHXL (× 2)

TSK gel G2000HXL

‧Determination solvent: tetrahydrofuran

‧Measuring temperature: 40 ℃

[Experimental Example 1] (Measurement of Gel Ratio)

The polarizing plate used in the production of the polarizing plate with an adhesive layer of the example or the comparative example was replaced, and a peeling treatment with a silicone-based release agent was performed on one side of a polyethylene terephthalate film. Deco Corporation, SP-PET3801, thickness: 38 μm), was used to produce an adhesive sheet. Specifically, the exposed adhesive layer on the structure constituted by the release sheet / adhesive layer (thickness: 25 μm) obtained in the manufacturing process of the example or the comparative example is laminated so that the release sheet and the release-treated surface side Connected. Thus, an adhesive sheet having a configuration of a release sheet / adhesive layer / release sheet was produced.

The obtained adhesive sheet was aged for 7 days under the conditions of 23 ° C. and 50% RH. Thereafter, the adhesive sheet was made into a sample having a size of 80 mm × 80 mm, and the adhesive layer was wrapped with a polyester mesh (net size 200), and the mass of the adhesive was measured by a precision balance. The mass at this time is taken as M1.

Next, the adhesive held by the polyester mesh was kept at room temperature. It was immersed with ethyl acetate for 24 hours at 23 ° C. After that, the adhesive was taken out and air-dried for 24 hours under an environment of a temperature of 23 ° C and a relative humidity of 50%, and further dried in an oven at 80 ° C for 12 hours. Only weigh the mass of the dried adhesive with a precision balance. The mass at this time is taken as M2. The gel ratio (%) is expressed as (M2 / M1) × 100. The results are shown in Table 2.

[Experimental Example 2] (Measurement of Optical Properties)

As a measurement sample, the same adhesive sheet as the one used in the measurement of the gel ratio (7 days ripe) was used. The adhesive layer of this adhesive sheet was subjected to a Haze value (%) (some times slightly Hz (%)) using a Haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000) based on the J IS K7105 standard. ) Measure. The results are shown in Table 2. And, the preferred range of the Haze value is from 0 to 5%.

[Experimental Example 3] (Durability Evaluation)

The polarizing plate with an adhesive layer obtained in the example or the comparative example was adjusted to a size of 233 mm × 309 mm with a cutting device (Super Knife, PN1-600, manufactured by Kono Seisakusho, Ltd.). The peeling sheet was peeled off, and the alkali-free glass (King Ning Corporation, Eagle XG) was attached based on the exposed adhesive layer, and then pressed in an autoclave manufactured by Kurihara Seisakusho at 0.5 MPa and 50 ° C. for 20 minutes.

After that, it was put in an environment of dry and durable conditions at 80 ° C., and observed with a 10-times magnifying glass after 500 hours. Changes in appearance were observed with the following criteria. The results are shown in Table 2.

◎: No problem in 4 sides

○: Among the 4 sides, there is no problem from the position of 0.6 mm or more from the outer peripheral end.

×: In at least one of the four sides, there is a difference in appearance of the adhesive of 0.1 mm or more from the outer peripheral end portion to a portion of 0.6 mm or more, such as floating, peeling, foaming, and streaks. often

[Experimental Example 4] (Light leakage resistance test)

The polarizing plate with an adhesive layer obtained in the example or the comparative example was adjusted to a size of 233 mm × 309 mm using a cutting device (Super Knife, PN1-600, manufactured by Kono Seisakusho, Ltd.). The release sheet was peeled off, and after the exposed adhesive layer was attached to an alkali-free glass (Eagle XG, manufactured by Corning Corporation), the autoclave manufactured by Kurihara Seisakusho was pressurized at 0.5 MPa and 50 ° C for 20 minutes. In addition, in the above bonding, the polarizing axis of the polarizer with the adhesive layer on the surface of the alkali-free glass is adjusted to a Nicole cross state (polarizing axis: ∠45 °, ∠135 °). In this state, it was left to stand in a dry environment at 80 ° C for 250 hours, and then left to stand in an environment at 23 ° C and 50% RH for 2 hours. As a sample, light leakage was performed by the method shown below. The results are shown in Table 2.

<Light leakage evaluation: ΔL *>

The MCPD-2000 manufactured by Otsuka Electronics Co., Ltd. was used to measure the lightness L * in each area shown in FIG. 3 in the above sample, and the lightness difference ΔL * was expressed by the formula: ΔL * = [(b + c + d + e) / 4] -a

(However, a, b, c, d, and e, the brightness at predetermined measurement points (1 in the center of each field) in areas A, B, C, D, and E.) It is calculated as light leakage. The smaller the value of ΔL *, the less the light leakage. In addition, L * max represents the maximum brightness in all the above-mentioned fields.

<Evaluation of light leakage: visual inspection>

The sample was placed on a flat-panel lamp (manufactured by Dentsu Industries, HF-SL-A312LC, illumination: 26,000 Lux, brightness: 10,000 cd), and a two-dimensional color luminance meter (manufactured by Konica Minolta) was used. , CA-2000) The image was converted into a luminance distribution image using analysis software (manufactured by Konica Minolta, CA-S20w). The brightness distribution image of the obtained sample was evaluated using the evaluation criteria shown in FIG. 4.

[Experimental Example 5] (Molecular weight measurement of sol portion)

The ethyl acetate used in the measurement of the gel ratio of Experimental Example 1 was concentrated with an evaporator to obtain a sol fraction. Next, the sol portion was diluted with tetrahydrofuran to a 0.1% by mass solution, and then the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) by GPC measurement were measured. The measurement conditions for GPC measurement are as described above.

As shown in Table 2, in the obtained polarizing plate with an adhesive layer, the gel ratio of the adhesive was in the range of 45 to 90%, and the weight average molecular weight of the sol portion was in the range of 600,000 to 2.5 million. , Excellent in durability and light leakage resistance. On the other hand, in the polarizing plate with an adhesive layer obtained in the comparative example, if at least one of the gel ratio and the weight average molecular weight of the sol portion is less than the above range, both or both of durability and light leakage resistance may change. difference.

The adhesive of the present invention is suitable for the adhesion of optical components such as polarizing plates and retardation plates, and the adhesive plate of the present invention is suitable as an adhesive plate for optical components such as polarizing plates and retardation plates.

Claims (8)

An adhesive containing an (meth) acrylate polymer polymerized by a solution polymerization method, characterized in that the gel ratio is 45 to 90%, and the sol part is subjected to a gel permeation chromatography (GPC) method. The measured weight-average molecular weight is 600,000 to 2.5 million, in which a disc liquid crystal layer of a polarizing plate formed by a polarizing film with a disc liquid crystal layer is bonded to a 25 μm-thick adhesive layer formed by the above-mentioned adhesive and The 233mm × 309mm size laminated body formed of alkali-free glass was placed in a dry environment at 80 ° C for 250 hours, and then after being left to stand in an environment of 23 ° C and 50% RH for 2 hours, the value of the difference ΔL * was 0.4 or less. . For example, the adhesive of the first scope of the patent application, wherein the adhesive contains a 1st (meth) acrylate polymer (A) having a weight average molecular weight of 600,000 to 2.5 million and a weight average molecular weight of 8,000 to 300,000. A component obtained by crosslinking 2 (meth) acrylate polymer (B). For example, as for the adhesive in the second item of the patent application, the ratio of the second (meth) acrylate polymer (B) is 5 to 100 parts by mass of the first (meth) acrylate polymer (A). 50 parts by mass. For example, the adhesive of the second scope of the patent application, wherein the above-mentioned second (meth) acrylate polymer (B) before crosslinking contains more than 1% by mass and less than 50% by mass of a monomer having a reactive functional group as Constituent. For example, the adhesive of the fourth scope of the patent application, wherein the second (meth) acrylate polymer (B) is reacted with a crosslinker (C) having a crosslinkable group capable of reacting with the reactive functional group, Thus being crosslinked. An adhesive sheet is an adhesive sheet provided with a base material and an adhesive layer. The adhesive sheet is characterized in that the adhesive layer is formed of an adhesive according to any one of claims 1 to 5. For example, the adhesive sheet according to item 6 of the patent application, wherein the substrate is an optical component. An adhesive sheet includes two release sheets and an adhesive layer that is in contact with the release surfaces of the two release sheets and is held by the release sheet. The adhesive sheet is characterized in that the adhesive layer is from the first to the first patent application scope. It is formed by the adhesive of any one of 5 items.