JP6602201B2 - Adhesive composition for polarizing plate, polarizing plate with adhesive, and display device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, a polarizing plate with a pressure-sensitive adhesive, and a display device.

  As a display device for displaying an image (for example, a liquid crystal display device, an organic electroluminescence display device, etc.), various display methods are widely used. Among these, a liquid crystal display device generally includes a liquid crystal cell in which a liquid crystal component oriented in a predetermined direction is sandwiched between two support substrates such as glass, and an optical device such as a polarizing plate, a retardation film, and a brightness enhancement film. It has a structure in which a film is bonded together. A pressure-sensitive adhesive is used when the optical films are laminated or when the optical film is attached to a liquid crystal cell.

Liquid crystal display devices are widely used as display devices for personal computers, televisions and the like. Liquid crystal display devices are used under various environmental conditions such as severe environmental conditions with a high amount of moisture at high temperature and high humidity and dry environmental conditions with low humidity. Therefore, even when used for a long period of time, the bonded portion bonded with the adhesive, that is, the interface between the adhesive layer and the polarizing film is not peeled off, or the adhesive layer does not break, It is required to have high durability such that bubbles are not easily generated in the pressure-sensitive adhesive layer. Furthermore, in recent years, with the development of mobile devices such as mobile phones and personal digital assistants, and the development of large televisions, there is a tendency to make the entire display device thinner and lighter. Therefore, further reduction in thickness and weight is demanded for optical films such as polarizing plates.
On the other hand, the usage environment has been diversified, such as being used in a harsh environment outdoors, and pressure-sensitive adhesives used for optical films have been required to have higher performance than before.

  The polarizing plate has a polarizing film (polarizer) using polyvinyl alcohol (PVA) or the like. When a stretched film is used for this polarizing film, for example, when exposed to a harsh environment such as high temperature and high humidity, a dimensional change accompanying shrinkage and expansion is likely to occur, and stress is generated in the polarizing plate. When the stress accompanying the dimensional change is not relaxed by the adhesive disposed between the polarizing plate and the liquid crystal cell, the residual stress is unevenly generated in the polarizing plate. As a result, there is a shift in the phase of the two polarizing plates arranged so that the extension axes of the polarizing film intersect each other on the front and back surfaces of the display panel, and so-called “white spots” unevenness (light leakage) Will occur. White spots are a phenomenon in which light leaks from four surroundings of the display unit of the liquid crystal display device and becomes white.

  As an adhesive composition that suppresses the occurrence of light leakage and has durability, a large amount of aromatic group-containing monomer in the range of about 20 to 60% by mass in the total mass of the (meth) acrylic copolymer The pressure-sensitive adhesive composition (see, for example, JP-A-2007-169329) and an aromatic group-containing monomer are copolymerized, and the dispersity (weight average molecular weight / number average molecular weight) is as wide as 10-50. A pressure-sensitive adhesive composition containing a copolymer having a degree of dispersion has been proposed (see, for example, JP-A-2007-138057).

However, the aromatic group-containing monomer has a specific odor. For example, when the aromatic group-containing monomer is used in a large amount as in the pressure-sensitive adhesive composition described in JP-A-2007-169329. However, odor due to residual monomers at the time of polymerization was a problem and was not put to practical use.
Further, when using a copolymer having a wide degree of dispersion, such as a pressure-sensitive adhesive composition described in Japanese Patent Application Laid-Open No. 2007-138057, a large amount of a polymerization initiator is added in the latter stage of polymerization in order to widen the degree of dispersion. In this case, the residual monomer is reduced, so even if a large amount of aromatic group-containing monomer is used, the problem of odor may not occur. However, by including a copolymer having a wide degree of dispersion, the durability is not sufficient, and it is difficult to solve the durability that requires higher performance while suppressing the odor, and the suppression of the occurrence of light leakage. Met.

  An object of the present invention is to provide a pressure-sensitive adhesive composition for a polarizing plate with less odor, excellent suppression of light leakage and excellent durability, and a polarizing plate with a pressure-sensitive adhesive and a display device using the same.

  The present invention relates to a (meth) acrylic copolymer having a specific range of the content ratio of a structural unit derived from a monomer having a weight average molecular weight and a dispersity in a specific range and having a cyclic group. Including the polyvalent isocyanate compound, the inventors have obtained the knowledge that an adhesive with excellent durability can be obtained while suppressing the occurrence of light leakage while preventing the problem of odor. It is a thing.

Specific means for solving the above-described problems are as follows.
<1> A structural unit derived from a monomer having a cyclic group and having a content ratio of 2% by mass to 9% by mass with respect to the total mass of the copolymer, a structural unit derived from a monomer having a hydroxyl group, and alkyl A (meth) acrylic copolymer containing a structural unit derived from (meth) acrylate and a polyvalent isocyanate compound are contained, and the weight average molecular weight of the (meth) acrylic copolymer is 800,000 to 1,800,000. And a dispersion (the ratio of the weight average molecular weight to the number average molecular weight of the (meth) acrylic copolymer (= weight average molecular weight / number average molecular weight)) of 4 to 9 is used. It is.

  <2> The pressure-sensitive adhesive for a polarizing plate according to <1>, wherein the structural unit derived from the hydroxyl group-containing monomer is contained in an amount of 1% by mass to 8% by mass in the total mass of the (meth) acrylic copolymer. Agent composition.

  <3> Further, a silane coupling agent having a thiol group is contained, and the content of the silane coupling agent with respect to 100 parts by mass of the (meth) acrylic copolymer is 0.01 parts by mass to 1.5 parts by mass. The pressure-sensitive adhesive composition for polarizing plates according to <1> or <2>.

  <4> The silane coupling agent having a thiol group is the pressure-sensitive adhesive composition for polarizing plates according to <3>, which is an oligomer type silane coupling agent.

  <5> Furthermore, it is the adhesive composition for polarizing plates as described in any one of said <1>-<4> containing an N-substituted imidazole compound.

  <6> Said <1 whose content ratio of the structural unit derived from the monomer which has the said cyclic group with respect to the structural unit derived from the monomer which has the said hydroxyl group is 0.3-9.0 on a mass basis > To the pressure-sensitive adhesive composition for a polarizing plate according to any one of <5>.

  <7> The total content of the structural unit derived from the monomer having a cyclic group and the structural unit derived from the monomer having a hydroxyl group is based on the total mass of the (meth) acrylic copolymer. It is an adhesive composition for polarizing plates as described in any one of said <1>-<6> which is 3 mass%-17 mass%.

  <8> A polarizer and a pressure-sensitive adhesive layer formed on the polarizer by applying the pressure-sensitive adhesive composition for a polarizing plate according to any one of <1> to <7>. It is a polarizing plate with an adhesive.

  <9> A display device comprising: a display panel for displaying an image; and the polarizing plate with an adhesive according to <8>, which is disposed on at least one surface of the display panel.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of light leakage is suppressed while preventing odor, and the adhesive composition for polarizing plates excellent in durability, and a polarizing plate with an adhesive and a display apparatus using the same are provided. The

In this specification, the term “process” is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. It is.
Moreover, the numerical value range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively.
Further, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. .
Moreover, (meth) acrylate means at least one of acrylate and methacrylate, and (meth) acryl means at least one of acrylic and methacryl.

<Adhesive composition for polarizing plate>
The pressure-sensitive adhesive composition for polarizing plates of the present invention (hereinafter, also simply referred to as “pressure-sensitive adhesive composition”) is derived from a monomer having a cyclic group, and the content ratio relative to the total mass of the copolymer is 2% by mass to A (meth) acrylic copolymer containing a structural unit of 9% by mass, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from an alkyl (meth) acrylate, and a polyvalent isocyanate compound. And the weight average molecular weight of the (meth) acrylic copolymer is 800,000 to 1,800,000, and the degree of dispersion (the ratio of the weight average molecular weight to the number average molecular weight of the (meth) acrylic copolymer (= The weight average molecular weight / number average molecular weight)) is 4-9. The said adhesive composition for polarizing plates may contain other components, such as a silane coupling agent, a hardening accelerator, and another additive, further as needed.

The pressure-sensitive adhesive composition for polarizing plate of the present invention is a cyclic group of a (meth) acrylic copolymer containing a structural unit derived from a monomer having a cyclic group and a structural unit derived from a monomer having a hydroxyl group. By adjusting the content of structural units derived from monomers having a specific range, and further adjusting the weight average molecular weight and dispersity of the (meth) acrylic copolymer to a specific range, While preventing problems, the occurrence of light leakage can be suppressed, and even better durability can be exhibited.
Although the operation of the present invention is not clear, it is estimated as follows.
By setting the degree of dispersion of the (meth) acrylic copolymer to a specific range, the proportion of low molecular weight components in the acrylic copolymer can be kept low. Thereby, since insufficient cohesive force of the pressure-sensitive adhesive layer can be suppressed, it is considered that foaming and bubbles generated during long-term use can be reduced.
Furthermore, the balance between birefringence control and stress relaxation can be achieved by making the content of the structural unit derived from the monomer having a cyclic group forming the (meth) acrylic copolymer into a specific range. It can be adjusted well, and the effect of suppressing light leakage is considered to be improved.

  Hereinafter, each component which comprises the adhesive composition for polarizing plates of this invention is explained in full detail.

(A) (Meth) acrylic copolymer The pressure-sensitive adhesive composition for polarizing plates of the present invention is derived from a monomer having a cyclic group, and the content ratio relative to the total mass of the copolymer is 2 mass% to 9 mass%. % (Meth) acrylic, comprising at least one structural unit derived from a monomer having a hydroxyl group, and at least one structural unit derived from an alkyl (meth) acrylate. It contains at least one type of copolymer (hereinafter also simply referred to as “copolymer”).
The (meth) acrylic copolymer includes a monomer having a cyclic group, a monomer having a hydroxyl group, an alkyl (meth) acrylate, and, if necessary, another monomer. It is a copolymer obtained by carrying out the copolymerization reaction of the monomer composition which is 2 mass%-9 mass% with respect to the total monomer amount.
When the monomer composition contains another monomer, the (meth) acrylic copolymer is a structural unit derived from a monomer having a cyclic group, or a structural unit derived from a monomer containing a hydroxyl group. In addition to structural units derived from alkyl (meth) acrylate, structural units derived from other monomers are included.

  The (meth) acrylic copolymer may be a random copolymer or a block copolymer, and particularly preferably a random copolymer.

  The (meth) acrylic copolymer contains at least one structural unit derived from a monomer having a cyclic group. By including a structural unit derived from a monomer having a cyclic group, the occurrence of light leakage can be more effectively suppressed when applied to a polarizing plate of a display device.

The monomer having a cyclic group is not particularly limited as long as it has at least one cyclic group in the molecule and is a polymerizable compound copolymerizable with a monomer having a hydroxyl group and an alkyl (meth) acrylate. .
Examples of the cyclic group in the monomer having a cyclic group include an aromatic hydrocarbon group, an aromatic heterocyclic group, an aliphatic hydrocarbon group, and the like, and preferably an aromatic hydrocarbon group having 6 to 6 carbon atoms. More preferably, it is 10 aromatic hydrocarbon groups. The number of cyclic groups in the monomer having a cyclic group is preferably 1 to 2, and more preferably 1.
Examples of the monomer having a cyclic group include (meth) acrylate having a cyclic group, (meth) acrylamide having a cyclic group, and a styrene derivative. Among them, the monomer having a cyclic group is preferably a (meth) acrylate having a cyclic group, more preferably a (meth) acrylate having an aromatic ring group, and the aromatic ring group is an alkylene group or an oxyalkylene. (Meth) acrylate having an ester bond via a group or a polyoxyalkylene group is more preferable, and (meth) acrylate having an aromatic ring group ester-bonded via an oxyalkylene group is particularly preferable.

Specific examples of the monomer having a cyclic group include phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypropyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and ethylene oxide (EO). Modified cresol (meth) acrylate, ethylene oxide (EO) modified nonylphenol (meth) acrylate, β-naphthyloxyethyl (meth) acrylate, biphenyl (meth) acrylate and other (meth) acrylates, styrene, α-methyl Examples thereof include styrene derivatives such as styrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene.
Among them, as for the monomer having a cyclic group, an aromatic ring group such as phenoxyethyl (meth) acrylate, phenoxypropyl (meth) acrylate, and β-naphthyloxyethyl (meth) acrylate is ester-bonded via an oxyalkylene group. A (meth) acrylate is preferred.
The monomer which has a cyclic group may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content ratio of the structural unit derived from the monomer having a cyclic group in the (meth) acrylic copolymer is 2% by mass to 9% by mass in the total mass of the (meth) acrylic copolymer, The content is preferably 2% by mass to 8% by mass, and more preferably 3% by mass to 7% by mass. When the content ratio of the structural unit derived from the monomer having a cyclic group is less than 2% by mass, the occurrence of light leakage cannot be more effectively suppressed when applied to a polarizing plate of a display device. Moreover, when the content rate of the structural unit derived from the monomer which has a cyclic group exceeds 9 mass%, it will be difficult to solve the problem of odor, and also the effect of suppressing the occurrence of light leakage will not be sufficient.

  The (meth) acrylic copolymer contains at least one structural unit derived from a monomer having a hydroxyl group. By including a structural unit derived from a monomer having a hydroxyl group, the cohesive force as an adhesive is improved, durability is improved, and the occurrence of light leakage is more effective when applied to a polarizing plate of a display device. Can be suppressed.

The monomer having a hydroxyl group constituting the (meth) acrylic copolymer is not particularly limited as long as it is a polymerizable compound having at least one hydroxyl group in one molecule and copolymerizable with alkyl (meth) acrylate. There is no. The number of hydroxyl groups in one molecule of the monomer having a hydroxyl group is not particularly limited, but is preferably 1.
Specific examples of the monomer having a hydroxyl group include hydroxyalkyl (meth) acrylate, (poly) alkylene glycol mono (meth) acrylate, N-hydroxyalkyl (meth) acrylamide, hydroxyalkyl vinyl ether, and ethylenic double bond. Examples thereof include alcohol derivatives. Especially, it is preferable that the monomer which has a hydroxyl group is a hydroxyalkyl (meth) acrylate, and it is more preferable that it is a hydroxyalkyl acrylate.

  The alkyl group in the hydroxyalkyl (meth) acrylate may be linear or branched. As carbon number of an alkyl group, it is preferable that it is 2-8, it is more preferable that it is 2-6, and it is still more preferable that it is 2-4. Further, the substitution position of the hydroxyl group is not particularly limited.

Specific 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, 6- Hydroxyhexyl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-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 ( Data) acrylate, poly (ethylene glycol - propylene glycol) mono (meth) acrylate, N- methylolacrylamide, N- hydroxyethyl acrylamide, 2-hydroxyethyl vinyl ether, allyl alcohol, mention may be made of methallyl alcohol and the like.
The monomer which has a hydroxyl group may be used individually by 1 type, and may be used in combination of 2 or more type.

The content ratio of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer is preferably 1% by mass to 8% by mass in the total mass of the (meth) acrylic copolymer. % To 7% by mass is more preferable, and 3.5% to 6% by mass is still more preferable.
When the content ratio of the structural unit derived from the monomer having a hydroxyl group is 1% by mass or more, it can be adjusted to an optimum elastic modulus, which is advantageous in terms of ensuring durability and tackiness. Further, when the content ratio of the structural unit derived from the monomer having a hydroxyl group is 8% by mass or less, an appropriate cohesive force is obtained, and the adhesiveness and durability tend to be excellent.
The content ratio of the structural unit derived from the monomer having a cyclic group and the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer is not particularly limited. From the viewpoint of durability and suppression of the occurrence of light leakage, the content ratio of the structural unit derived from the monomer having a cyclic group to the structural unit derived from the monomer having a hydroxyl group (on the monomer having a cyclic group) The structural unit derived from / the structural unit derived from the monomer having a hydroxyl group) is preferably 0.3 to 9.0, more preferably 0.4 to 5.0 on a mass basis. More preferably, it is 5-2.3.
The total content of the structural unit derived from the monomer having a cyclic group and the structural unit derived from a monomer having a hydroxyl group in the (meth) acrylic copolymer is not particularly limited. From the viewpoint of durability and suppression of light leakage, the total content of structural units derived from monomers having cyclic groups and structural units derived from monomers having hydroxyl groups is (meth) acrylic copolymer It is preferably 3% by mass to 17% by mass, more preferably 5% by mass to 14% by mass, and still more preferably 6% by mass to 13% by mass with respect to the total mass of the coalescence.

  The (meth) acrylic copolymer contains at least one structural unit derived from alkyl (meth) acrylate. The alkyl group in the alkyl (meth) acrylate may be linear or branched. The number of carbon atoms of the alkyl group is preferably 1-20, more preferably 1-18, still more preferably 1-12, and particularly preferably 1-6.

Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meta ) Acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) ) Acrylate and the like. Among them, the alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group in that the cohesive force and adhesive force of the pressure-sensitive adhesive are easily adjusted, and the alkyl group having 1 to 1 carbon atoms. 12 alkyl (meth) acrylates are more preferable, and alkyl acrylates having 1 to 6 carbon atoms in the alkyl group are more preferable.
An alkyl (meth) acrylate may be used individually by 1 type, and may be used in combination of 2 or more type.

  The structural unit derived from alkyl (meth) acrylate is preferably contained as a main component for forming the (meth) acrylic copolymer, and the content ratio as the main component is (meth) acrylic copolymer The total mass of the coalescence is preferably 80% by mass or more, more preferably 85% by mass to 97% by mass, and still more preferably 87% by mass to 96% by mass. When the content ratio of the structural unit derived from the alkyl (meth) acrylate is within the above range, it can be adjusted to an optimal elastic modulus, which is advantageous in terms of ensuring durability and tackiness.

In addition to a structural unit derived from a monomer having a cyclic group, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from an alkyl (meth) acrylate, The structural unit derived from other monomers other than these may be included.
Other monomers include monomers having an acidic group such as acrylic acid, methacrylic acid, and ω-carboxypolycaprolactone mono (meth) acrylate; aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethyl Monomers having basic groups such as aminopropyl (meth) acrylate and vinylpyridine; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; vinyls such as vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate An ester monomer etc. can be mentioned.

  The (meth) acrylic copolymer may include a structural unit derived from a monomer having an acidic group. In this case, the content ratio of the structural unit derived from the monomer having an acidic group in the (meth) acrylic copolymer is 0.5% by mass or less in the total mass of the (meth) acrylic copolymer. It is preferable that it is present, more preferably 0.2% by mass or less, and further preferably substantially not contained. Here, “substantially free” means allowing the presence of a structural unit derived from a monomer having an acidic group which is inevitably mixed. When the content ratio of the structural unit derived from the monomer having an acidic group is within the above range, the corrosion of the metal oxide or the metal does not become a problem. For example, the display device equipped with the touch panel is not corroded. This is preferable because it can be used for problematic applications.

  The weight average molecular weight (Mw) of the (meth) acrylic copolymer is 800,000 to 1,800,000, more preferably 1,000,000 to 1,800,000, and still more preferably 1,300,000 to 1,800,000. When the weight average molecular weight is 800,000 or more, the cohesive force of the pressure-sensitive adhesive is maintained, and the durability is excellent. Further, when the weight average molecular weight is 1,800,000 or less, the handling property at the time of coating of the pressure-sensitive adhesive composition for polarizing plates is improved.

  The degree of dispersion of the (meth) acrylic copolymer (the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth) acrylic copolymer (Mw)) is 4 to 9. It is preferably 4 to 8.5, and more preferably 5 to 8. When the degree of dispersion is 4 or more, it is easy to reduce unreacted monomers and is advantageous in suppressing the generation of odor. Further, when the dispersity is 9 or less, the low molecular weight component can be suppressed to be small, and the durability is excellent.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the (meth) acrylic copolymer can be measured using gel permeation chromatography (GPC) under the following normal conditions.
<Condition>
・ GPC: HLC-8220 GPC (manufactured by Tosoh Corporation)
・ Column: 4 TSK-GEL GMHXL used (manufactured by Tosoh Corporation)
-Mobile phase solvent: Tetrahydrofuran-Standard sample: Standard polystyrene-Flow rate: 0.6 ml / min.
-Column temperature: 40 ° C

  The (meth) acrylic copolymer can be produced by polymerizing a monomer composition containing a monomer having a cyclic group, a monomer having a hydroxyl group, and an alkyl (meth) acrylate. The polymerization method of the monomer composition is not particularly limited and can be appropriately selected from commonly used polymerization methods. Examples of the polymerization method include solution polymerization, emulsion polymerization, suspension polymerization and the like. Among these, solution polymerization is preferable because the treatment process is relatively simple and can be performed in a short time.

In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, and stirred in a nitrogen stream or under reflux of the organic solvent. Heat the reaction for several hours. The polymerization initiator is not particularly limited, and for example, an azo compound can be used.
In addition, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic copolymer are adjusted to a desired molecular weight by adjusting the acrylic reaction temperature, time, solvent amount, and type and amount of the catalyst. be able to.

  The content of the (meth) acrylic copolymer in the pressure-sensitive adhesive composition for polarizing plates is not particularly limited. The content of the (meth) acrylic copolymer is preferably 70% by mass or more, and more preferably 80% by mass or more in the total mass of the pressure-sensitive adhesive composition for polarizing plates.

(B) Polyvalent isocyanate compound The pressure-sensitive adhesive composition for polarizing plates of the present invention contains at least one polyisocyanate compound. The polyvalent isocyanate compound acts as a crosslinking agent for the (meth) acrylic copolymer in the pressure-sensitive adhesive composition for polarizing plates.
As the polyvalent isocyanate compound, a compound having two or more isocyanate groups in the molecule is preferable. For example, tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, Diisocyanate compounds such as hydrogenated diphenylmethane diisocyanate; diisocyanates or dimers of diisocyanate compounds; isocyanate compounds or isocyanurates obtained by addition reaction of diisocyanate compounds with various divalent or higher alcohol compounds, etc. .

  Among these, from the viewpoint of durability and shortening of the curing time, the polyvalent isocyanate compound is a partial structure derived from an aromatic diisocyanate compound and a polyvalent isocyanate compound having an isocyanurate ring structure (hereinafter simply referred to as “polyvalent isocyanate compound”). It is preferable to contain at least one of (also referred to as). Among these, the polyvalent isocyanate compound is preferably a polyvalent isocyanate compound in which each isocyanate group forms an isocyanurate ring structure by an addition reaction in a plurality of aromatic diisocyanate compounds. In this case, the aromatic diisocyanate compound forming the polyvalent isocyanate compound may be only one kind or a mixture of two or more kinds.

  The aromatic diisocyanate compound may be a compound having two isocyanate groups on the aromatic ring, preferably a compound having two isocyanate groups on the benzene ring, and more preferably tolylene diisocyanate. More preferably, it is at least one selected from 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate.

Specific examples of the polyvalent isocyanate compound include a compound that is a trimer of an aromatic diisocyanate compound represented by the following general formula (I), and a pentamer of an aromatic diisocyanate compound represented by the following general formula (II): Or a dimer of an aromatic diisocyanate compound. Furthermore, the polyvalent isocyanate compound may be a compound having an isocyanurate ring structure formed from an aromatic diisocyanate compound and an alkylene diisocyanate compound, or a compound having an isocyanurate ring structure formed from tolylene diisocyanate and hexamethylene diisocyanate. It is also preferred that it be.
The polyvalent isocyanate compound may be used alone or in combination of two or more.

In general formula (I) and general formula (II), R < ¹¹ > -R < ²⁵ > shows a hydrogen atom or a methyl group each independently. Among R ^{11 to} R ¹³ , any one group is preferably a methyl group, and the other group is preferably a hydrogen atom. Of R ^{14 to} R ¹⁶ , any one group is preferably a methyl group, and the other group is preferably a hydrogen atom. Among R ^{17 to} R ¹⁹ , one group is preferably a methyl group, and the other group is preferably a hydrogen atom. Of R ^{20 to} R ²² , one group is preferably a methyl group, and the other group is preferably a hydrogen atom. Among R ^{23 to} R ²⁵ , any one group preferably represents a methyl group, and the other group preferably represents a hydrogen atom.

The partial structure derived from the aromatic diisocyanate compound and the polyvalent isocyanate compound having an isocyanurate ring structure may be prepared by a conventional method or commercially available.
Examples of commercially available polyisocyanate compounds include trade names “Desmodur ILBA”, “Desmodur IL1451CN”, “Desmodur HL”, “Sumijoule FL-2”, “Sumijoule” manufactured by Sumitomo Bayer Urethane Co., Ltd. Name FL-3 ”and“ SBU Isocyanate 0817 ”, trade names“ Coronate 2030 ”and“ Coronate 2037 ”manufactured by Nippon Polyurethane Industry Co., Ltd. and trade names“ Pollene KC ”and“ Polurene HR ”manufactured by SAPCI. Can do.

  In the pressure-sensitive adhesive composition for polarizing plate, the content of the polyvalent isocyanate compound is preferably in the range of 0.01 parts by mass to 1.0 part by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. More preferably, it is the range of 0.01 mass part-0.5 mass part, More preferably, it is the range of 0.05 mass part-0.3 mass part. When the content of the polyvalent isocyanate compound is 0.01 parts by mass or more, the crosslinking reaction proceeds better, the cohesive force becomes better, and the adhesiveness and durability tend to be better. Further, when the content of the polyvalent isocyanate compound is 1.0 part by mass or less, it becomes more excellent in pot life. For example, when the pressure-sensitive adhesive composition for polarizing plate is coated, the viscosity increases. Occurrence of poor coating is prevented and the coating workability is excellent.

In addition to the polyvalent isocyanate compound, the pressure-sensitive adhesive composition for polarizing plates may further contain other cross-linking agents. Examples of other crosslinking agents include epoxy crosslinking agents, aziridine crosslinking agents and the like.
In the case where the pressure-sensitive adhesive composition for polarizing plates contains other crosslinking agents, the content is not particularly limited as long as the effects of the present invention are not impaired. The content of the other crosslinking agent is, for example, preferably 5 parts by mass or less and more preferably 1 part by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer.

(C) Silane coupling agent It is preferable that the adhesive composition for polarizing plates further contains at least 1 type of a silane coupling agent. When the pressure-sensitive adhesive composition for polarizing plate contains a silane coupling agent, the pressure-sensitive adhesive layer and the polarizing plate or liquid crystal even when a display device (for example, a liquid crystal display device) incorporating the polarizing plate is exposed to a high temperature and high humidity environment. There is a tendency that peeling is less likely to occur between the cells. Furthermore, there exists a tendency for the adhesive composition for polarizing plates to show the adhesiveness outstanding with respect to smooth glass.

  Examples of the silane coupling agent include silane coupling agents having a polymerizable unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane; 3-mercaptopropyltrimethoxysilane, Silane coupling agents having a thiol group, such as 3-mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane; 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Coupling agents having an epoxy group, such as silane; 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyl Methyldimethoxy Such as orchids, a silane coupling agent having an amino group; tris - (3-trimethoxysilylpropyl) isocyanurate and the like. These may be used alone or in combination of two or more.

  As the silane coupling agent, commercially available products may be used. Examples of commercially available products include trade names “KBM-803”, “KBM-802”, and “X-41” manufactured by Shin-Etsu Chemical Co., Ltd. Silane coupling agents having a thiol group such as “-1810”, “X-41-1805”, “X-41-1818”, “KBM-403”, “KBM-303” manufactured by Shin-Etsu Chemical Co., Ltd., “ A silane coupling agent having an epoxy group such as KBM-402, KBE-402, and KBE-403 (trade name) can be preferably used.

  Among silane coupling agents, it has a thiol group from the viewpoint of durability and imparting re-peelability (reworkability) that can be easily peeled without causing adhesive residue or destruction of the adherend after adhesion. It is preferable to use at least one selected from silane coupling agents, and it is more preferable to use at least one selected from oligomer-type silane coupling agents having a thiol group. Here, the oligomer type silane coupling agent having a thiol group is preferably a silane coupling agent composed of a silane coupling agent having a thiol group and a silane coupling agent not having a thiol group. Examples include trade names “X-41-1810”, “X-41-1805”, and “X-41-1818” manufactured by Chemical Industry Co., Ltd.

  When the pressure-sensitive adhesive composition for polarizing plates contains a silane coupling agent, the content of the silane coupling agent in the pressure-sensitive adhesive composition for polarizing plates is based on 100 parts by weight of the (meth) acrylic copolymer. The range of 0.05 mass part-5.0 mass parts is preferable, the range of 0.1 mass part-3.0 mass parts is more preferable, The range of 0.1 mass part-1.5 mass parts is still more preferable.

(D) Imidazole compound It is preferable that the adhesive composition for polarizing plates contains at least 1 type of an imidazole compound. The imidazole compound functions as, for example, a curing accelerator in the pressure-sensitive adhesive composition for polarizing plates. When the pressure-sensitive adhesive composition for polarizing plate contains an imidazole compound, the curing time can be further shortened while maintaining excellent durability and sufficient pot life.

The imidazole compound is not particularly limited as long as it is a compound having at least one imidazole skeleton in the molecule, and can be appropriately selected from commonly used imidazole curing accelerators. Among these, the imidazole compound is preferably an N-substituted imidazole compound from the viewpoint of shortening the curing time and pot life. The N-substituted imidazole compound is not particularly limited as long as it has at least one imidazole ring in the molecule and does not have a hydrogen atom on the nitrogen atom of the imidazole ring.
Specific examples of the N-substituted imidazole compound include compounds represented by the following general formula (III).

In the general formula (III), R ¹ represents an alkyl group, an aryl group, or an aralkyl group. R ^{2 to} R ⁴ each independently represent a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group. R ¹ and R ² may be connected to each other to form a ring with the carbon atom and nitrogen atom to which they are bonded, and R ³ and R ⁴ may also be connected to each other to form a ring with the carbon atom to which they are bonded. May be formed.

  The alkyl group in general formula (III) may be linear or branched. Moreover, it is preferable that carbon number of an alkyl group is 1-2. The aryl group in general formula (III) preferably has 6 to 10 carbon atoms, and more preferably a phenyl group or a naphthyl group. The aralkyl group in the general formula (III) is preferably composed of an alkylene group having 1 to 2 carbon atoms and an aryl group having 6 to 10 carbon atoms, and more preferably a benzyl group or a phenylethyl group.

In the N-substituted imidazole compound represented by the general formula (III), R ¹ is an alkyl group or an aralkyl group, and R ^{2 to} R ⁴ are each independently a hydrogen atom from the viewpoint of shortening pot life and curing time. An alkyl group or an aryl group, preferably from the group consisting of 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 2-ethyl-4-methylimidazole, and 1-benzyl-2-phenylimidazole. More preferably, it is at least one selected, and more preferably 1-benzyl-2-phenylimidazole.
Further, R ¹ and R ² are connected to each other to form a 5-membered to 6-membered saturated aliphatic ring, and R ³ and R ⁴ are connected to each other to form a 6-membered aromatic ring. It is also preferable that it is 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole.

  When the adhesive composition for polarizing plates contains an imidazole compound, content of the imidazole compound in the adhesive composition for polarizing plates is 0.005 mass with respect to 100 mass parts of (meth) acrylic copolymers. Part to 0.5 parts by weight is preferable, 0.01 part to 0.3 parts by weight is more preferable, and 0.01 part to 0.2 parts by weight is even more preferable.

(E) Other components In addition to the above-mentioned components, the pressure-sensitive adhesive composition for polarizing plate further comprises a weather resistance stabilizer such as a solvent and an ultraviolet absorber, a tackifier, a plasticizer, a softener, and an antistatic agent. , Dyes, pigments, inorganic fillers and the like. When the polarizing plate pressure-sensitive adhesive composition contains other components, the content of the other components can be appropriately selected within a range not impairing the effects of the present invention.

<Polarizing plate with adhesive>
The polarizing plate with pressure-sensitive adhesive of the present invention has at least a polarizer and a pressure-sensitive adhesive layer formed on the polarizer by applying the above-described pressure-sensitive adhesive composition for polarizing plate of the present invention.

  In general, for example, a polyvinyl alcohol (PVA) film is used as the polarizer. The polarizer is, for example, polarized light having a three-layer structure (for example, TAC / polarizer / TAC) held between protective sheets such as triacetyl cellulose (TAC), polycycloolefin (COP), and an acrylic film. It can be used as a plate.

For example, by providing the pressure-sensitive adhesive composition for a polarizing plate of the present invention described above on at least one surface of a polarizing plate having a three-layer structure of TAC / polarizer / TAC, polarizing with pressure-sensitive adhesive A plate is made. In this case, the pressure-sensitive adhesive composition for polarizing plate may be applied on the polarizing plate, but preferably the pressure-sensitive adhesive composition for polarizing plate is applied on a protective sheet (peeling sheet) that is peeled off during use. . The application of the pressure-sensitive adhesive composition for a polarizing plate can be suitably performed by a coating method such as a dipping method, a coating method, or an ink jet method using a liquid pressure-sensitive adhesive composition for a polarizing plate. Among these, the application method is preferable.
Specifically, the pressure-sensitive adhesive composition for polarizing plate of the present invention is applied on a protective sheet (release sheet) and dried to form a pressure-sensitive adhesive layer on the protective sheet, and then the pressure-sensitive adhesive layer is polarized. A polarizing plate with an adhesive is produced by transferring and curing on a plate. Moreover, after apply | coating the adhesive composition for polarizing plates of this invention on a protective sheet (peeling sheet), and making it dry and forming an adhesive layer on a protective sheet, it further protects on the exposed surface of an adhesive layer. A double-sided pressure-sensitive adhesive tape without a support is prepared by closely attaching a protective sheet, and after curing the pressure-sensitive adhesive layer, one protective sheet is peeled off, and the exposed pressure-sensitive adhesive layer is transferred onto the polarizing plate. The polarizing plate with an adhesive may be produced.

  The polarizing plate pressure-sensitive adhesive composition applied on the protective sheet (release sheet) is preferably dried at 70 ° C. to 120 ° C. under a drying condition of about 1 minute to 3 minutes using a hot air dryer or the like. .

Further, a protective sheet (peeling sheet) for protecting the exposed surface is provided in close contact with the exposed surface of the pressure-sensitive adhesive layer provided on the polarizing plate from the viewpoint of protecting the contact surface with the adherend. It is preferable to keep. As this protective sheet, a synthetic resin sheet such as polyester subjected to a release treatment with a release agent such as a fluororesin, paraffin wax, silicone or the like so that it can be easily separated from the adhesive layer. Preferably used. When affixing to a glass plate or the like of the display panel, the protective sheet is peeled off, and the exposed surface of the pressure-sensitive adhesive layer is adhered to the glass substrate or the like.
Moreover, you may further provide the surface protection sheet which protects the surface (exposed surface) of the side in which the adhesive layer of a polarizing plate is not provided. As the surface protective sheet, a protective film or the like that is adhesively processed on one side of a PET film is preferably used.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and still more preferably 15 μm or more and 30 μm or less.

<Display device>
The display device of the present invention is provided with a display panel for displaying an image, and the above-described polarizing plate with an adhesive of the present invention disposed on at least one surface of the display panel.
Examples of the display panel include a liquid crystal display panel in which a liquid crystal compound is sealed, an organic electroluminescence display panel, and the like.

  As an example of the display device of the present invention, the polarizing plate with the pressure-sensitive adhesive of the present invention is arranged on both sides of the liquid crystal display panel so that the pressure-sensitive adhesive layer is in contact with the surface of the liquid crystal display panel (for example, the surface of the glass substrate). And a liquid crystal display device having a structure (polarizing plate / adhesive layer / liquid crystal display panel / adhesive layer / polarizing plate structure) in which polarizing plates are bonded to both surfaces of the liquid crystal display panel via an adhesive layer. Can do.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

(Production Example 1)
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 87 parts by mass of n-butyl acrylate (BA), 9 parts by mass of phenoxyethyl acrylate (PHEA), 2-hydroxyethyl acrylate ( 2 parts of HEA) and 90 parts by weight of ethyl acetate (EAc) were added and mixed, and then the inside of the reaction vessel was replaced with nitrogen. Thereafter, the temperature of the mixture in the reaction vessel was raised to 70 ° C. in a nitrogen atmosphere with stirring, and then 0.02 parts by mass of azobisdimethylvaleronitrile (ABVN) and 200 parts by mass of ethyl acetate (EAc) were sequentially added. The reaction was performed for 6 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain a solution of (meth) acrylic copolymer 1.
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the obtained (meth) acrylic copolymer were measured using gel permeation chromatography (GPC) under the following conditions. As a result, the weight average molecular weight (Mw) was 1.4 million, and the dispersity (Mw / Mn) was 7.5.
[conditions]
・ GPC: HLC-8220 GPC (manufactured by Tosoh Corporation)
・ Column: 4 TSK-GEL GMHXL used (manufactured by Tosoh Corporation)
-Mobile phase solvent: Tetrahydrofuran-Standard sample: Standard polystyrene-Flow rate: 0.6 ml / min.
-Column temperature: 40 ° C

(Production Examples 2 to 18)
In Production Example 1, the same manner as in Production Example 1 except that the types and ratios of the monomers used for the synthesis of (meth) acrylic copolymer 1 were changed as shown in Tables 1 and 2 below. , (Meth) acrylic copolymers 2 to 18 were obtained.
Moreover, about each obtained (meth) acrylic-type copolymer, it carried out similarly to manufacture example 1, and measured Mw and Mn. The results are shown in Table 1 and Table 2 below.

  In Tables 1 and 2, “BA” is n-butyl acrylate, “MA” is methyl acrylate, “t-BA” is t-butyl acrylate, “PHEA” is phenoxyethyl acrylate, and “BZA” is benzyl acrylate. "2HEA" indicates 2-hydroxyethyl acrylate, "4HBA" indicates 4-hydroxybutyl acrylate, and "-" indicates that it is not blended.

<Example 1>
-Preparation of adhesive composition-
As a (meth) acrylic copolymer (in the table, simply expressed as “copolymer”), 100 parts by mass (solid content) of the (meth) acrylic copolymer 1 obtained in Production Example 1 above. 0.15 parts by mass (solid content) of Coronate 2037 (manufactured by Nippon Polyurethane Industry Co., Ltd.) as the polyvalent isocyanate compound (crosslinking agent), and Curazole 1B2PZ (Shikoku Kasei Co., Ltd.) as the N-substituted imidazole compound (curing accelerator) Manufactured by 1-benzyl-2-phenylimidazole) and 0.3 part by mass of X-41-1810 (manufactured by Shin-Etsu Chemical Co., Ltd., oligomer type having a thiol group) as a silane coupling agent. Were sufficiently mixed with stirring to obtain a pressure-sensitive adhesive composition.

-Production of optical film sample-
The pressure-sensitive adhesive composition was applied to the release agent-treated surface of the release film surface-treated with the silicone release agent so that the coating amount after drying was 20 g / cm ² . Next, this was dried at 100 ° C. for 90 seconds using a hot-air circulating dryer to form an adhesive layer on the release film. Subsequently, a polarizing base film (a laminated structure of TAC film / PVA film / TAC film by laminating cellulose triacetate (TAC) films on both sides of a polarizer mainly composed of polyvinyl alcohol (PVA) film; about 190 μm) The back surface of the adhesive layer and the surface of the pressure-sensitive adhesive layer were overlapped and bonded together, and pressed through a pressure nip roll. After the pressure bonding, the film was cured for 7 days under an environmental condition of 23 ° C. and 65% RH, and a polarizing film having a laminate structure of release film / adhesive layer / polarizing base film was produced as an optical film sample.

-Evaluation-
The following evaluation was performed using the (meth) acrylic copolymer, the pressure-sensitive adhesive composition and the polarizing film prepared above. The evaluation results are shown in Tables 3 to 5 below.

(durability)
The optical film sample obtained as described above was cut into a 140 mm × 260 mm rectangular shape so that the long side was 0 ° with respect to the absorption axis, and the release film was peeled off. Thereafter, the surface of the pressure-sensitive adhesive layer of the optical film sample was attached to one surface of a 0.7 mm-thick non-alkali glass plate “Eagle XG” (manufactured by Corning) using a laminator to prepare a test piece. The obtained test piece was autoclaved (50 ° C., 5 kg / cm ² (490 kPa), 20 minutes) and then allowed to stand for 24 hours at 23 ° C. and 50% RH. Then, after standing for 500 hours under heat-resistant conditions (Dry conditions) at 80 ° C. or wet-heat resistant conditions (Wet conditions) at 60 ° C. and 90% RH, the state of foaming or peeling was confirmed visually. Evaluation was performed according to the evaluation criteria.
Further, using a thermal shock apparatus TSA-301L-W (manufactured by Espec Corp.), a heat shock (H / H) was repeated for 200 cycles of a cycle of leaving at -40 ° C for 0.5 hours and then leaving at 85 ° C for 0.5 hours. S) After processing under the conditions, the evaluation was made in the same manner.
<Evaluation criteria>
A: No foaming was observed. Further, no peeling was observed at a position of 0.5 mm or more inward from the outer peripheral portion on the two sides.
B: Almost no foaming was observed. Further, peeling was not observed at a position of 0.8 mm or more inward from the outer peripheral portion on the two sides.
C: Remarkable foaming was observed. Alternatively, peeling was observed at a position of 1.0 mm or more inward from the outer peripheral portion on the two sides.

(Light leakage)
Two optical film samples obtained as described above were prepared, cut into a rectangular shape of 140 mm × 260 mm, and the release films of both samples were peeled off. Thereafter, the surfaces of the pressure-sensitive adhesive layers of the two optical film samples were attached to both surfaces of the VA liquid crystal panel using a laminator so that the polarization axes thereof were orthogonal to each other, thereby preparing test pieces. The obtained test piece was autoclaved (50 ° C., 5 kg / cm ² (490 kPa), 20 minutes), then left at 23 ° C. and 50% RH for 24 hours, and then left at 70 ° C. for 250 hours. did. Thereafter, the test piece was left for 1 hour under the conditions of 23 ° C. and 50% RH. Using a uniform light source, the state of light leakage was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Almost no light leakage was observed.
B: Light leakage was slightly observed.
C: Remarkable light leakage was observed.

(Odor)
In the said manufacture example, each of the obtained (meth) acrylic-type copolymer was diluted with ethyl acetate, the density | concentration was adjusted to 15% of solid content, and the measurement sample was prepared. The density | concentration of the monomer which has a cyclic group in the obtained measurement sample was measured on condition of the following using gas chromatography (GC). The odor was evaluated according to the following evaluation criteria using the concentration of the monomer having a cyclic group in the measurement sample.
<Condition>
-GC device: GC-17A manufactured by Shimadzu Corporation
・ Column: ZB-5 60 × 0.53φ
Inj: 150 ° C.
Det: 260 ° C
・ Temperature: 40 ° C. (5 min) → 10 ° C./min→240° C. (10 min)
・ Injection volume: 1.0 μL
<Evaluation criteria>
A: The concentration is less than 2000 ppm.
B: The concentration is 2000 ppm or more and less than 4000 ppm.
C: The concentration is 4000 ppm or more.

(Pot life)
The pot life of the pressure-sensitive adhesive composition obtained above was evaluated by measuring the viscosity as follows and calculating the rate of increase in viscosity.
The viscosity of the pressure-sensitive adhesive composition was adjusted using ethyl acetate so as to be 1500 mPa · s. At this time, the viscosity immediately after the adjustment was measured at 25 ° C., 1 minute, and 10 rpm with a BH type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd .; the same shall apply hereinafter) to obtain viscosity (a). Further, after being allowed to stand in a sealed container for 24 hours under conditions of 25 ° C. and 50% RH, the viscosity (b) at 25 ° C., 1 minute, and 10 rpm was measured with a BH type rotational viscometer. Using the obtained viscosity (a) and viscosity (b), the rate of increase in viscosity (%) was calculated according to the following formula.
Viscosity increase rate (%) = viscosity after standing for 24 hours (b) / viscosity immediately after blending (a) × 100
<Evaluation criteria>
A: The viscosity increase rate (%) is less than 110%.
B: The viscosity increase rate (%) is 110% or more and less than 130%.
C: Viscosity increase rate (%) is 130% or more.

(Curing time)
The time required for curing of the pressure-sensitive adhesive composition obtained above (curing time) was evaluated by measuring the gel fraction as follows.
The pressure-sensitive adhesive composition was applied on a release film surface-treated with a silicone release agent, and a pressure-sensitive adhesive layer was formed so that the thickness after drying was 25 μm, thereby obtaining a pressure-sensitive adhesive film. Next, the obtained pressure-sensitive adhesive film was stored in an environment of 23 ° C. and 50% RH, and after a predetermined storage time from the start of storage, the gel fraction (after 24 hours, 48 hours, 72 hours, The gel fraction after 96 hours) and the gel fraction after 168 hours were measured as follows. The gel fraction after the predetermined storage time has elapsed and the gel fraction after 168 hours are compared, and the initial storage time required for the difference between the gel fractions to be 3% or less is cured. It was time.

The gel fraction was measured by the following method.
(1) Apply about 0.25 g of the pressure-sensitive adhesive layer to a precisely weighed 250-mesh wire mesh (100 mm × 100 mm) and wrap so that the gel content does not leak. Thereafter, the mass is accurately measured with a precision balance to prepare a sample.
(2) The obtained sample is immersed in 80 ml of ethyl acetate for 3 days.
(3) A sample is taken out, washed with a small amount of ethyl acetate, and dried at 120 ° C. for 24 hours. Thereafter, the mass is measured with a precision balance.
(4) Calculate the gel fraction by the following formula.
Gel fraction (mass%) = (Z−X) / (Y−X) × 100
However, X is the mass (g) of the wire mesh, Y is the mass of the wire mesh with the adhesive layer attached (mass of the adhesive layer) (g), Z is the mass of the wire mesh (gel resin mass) that is dried after dipping ( g).
<Evaluation criteria>
A: Curing time is 24 hours.
B: Curing time is 48 hours or 72 hours.
C: Curing time is 96 hours or more.

(Reworkability)
The optical film sample obtained above was cut into a 120 mm × 25 mm rectangle so that the long side was 180 ° with respect to the absorption axis, and the release film was peeled off. Thereafter, the surface of the pressure-sensitive adhesive layer of the optical film sample was attached to one surface of a 0.7 mm-thick non-alkali glass plate “Eagle XG” (manufactured by Corning) using a laminator to prepare a test piece.
The obtained test piece was autoclaved (50 ° C., 5 kg / cm ² (490 kPa), 20 minutes) and then allowed to stand for 24 hours at 23 ° C. and 50% RH. Thereafter, it was left for 48 hours in an environment of 50 ° C., and then left for 1 hour in an environment of 23 ° C. and 50% RH. Using this test piece, the adhesive strength at 180 ° peeling at 23 ° C. and 50% RH was measured at a peeling speed of 300 mm / min, and the reworkability was evaluated according to the following evaluation criteria.
The reworkability is an evaluation assuming that the adhesive layer is attached to an adherend such as a liquid crystal cell. In this evaluation, when the adhesive layer is applied to a glass plate and then peeled off, for example, a liquid crystal The performance of easily peeling from the adherend is evaluated without causing a load on the cell adherend (here, a glass plate) or causing adhesive residue or contamination on the adherend.
<Evaluation criteria>
A: Adhesive strength is 5 N / 25 mm or less.
B: Adhesive strength is greater than 5 N / 25 mm and not greater than 10 N / 25 mm.
C: Adhesive strength is greater than 10 N / 25 mm and not greater than 20 N / 25 mm.
D: Adhesive strength is greater than 20 N / 25 mm.

<Examples 2 to 15 and Comparative Examples 1 to 8>
In Example 1, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the composition of the pressure-sensitive adhesive composition was changed as shown in Tables 3 to 5 below, and an optical film sample was prepared using this. Were prepared.
The used (meth) acrylic copolymer, the obtained pressure-sensitive adhesive composition, and the optical film sample were evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 3 to 5.

In addition, the symbol in a table | surface is as showing below, and a compounding quantity is a value of solid content conversion.
(Crosslinking agent)
C-2037: Nippon Polyurethane Industry Co., Ltd., coronate 2037, isocyanurate of tolylene diisocyanate C-2030: Nippon Polyurethane Industry Co., Ltd., coronate 2030, isocyanurate of tolylene diisocyanate CL: Japan Made by Polyurethane Industry Co., Ltd., Coronate L, Trimethylolpropane adduct of tolylene diisocyanate (silane coupling agent)
・ X-41-1810: manufactured by Shin-Etsu Chemical Co., Ltd., oligomer type having a thiol group ・ KBM-803: manufactured by Shin-Etsu Chemical Co., Ltd., monomer type having a thiol group ・ KBM-403: manufactured by Shin-Etsu Chemical Co., Ltd. Monomer type with epoxy group (curing accelerator)
1B2PZ: 1-benzyl-2-phenylimidazole manufactured by Shikoku Chemicals Co., Ltd. 1B2MZ: 1-benzyl-2-methylimidazole manufactured by Shikoku Chemicals Co., Ltd.

[Production and Evaluation of Liquid Crystal Display]
The optical film sample (polarizing film) produced using the adhesive composition produced in Examples 1-15 was incorporated, and the liquid crystal display device was produced, respectively.
When the optical characteristics of the obtained liquid crystal display device were visually confirmed, it was confirmed that there was no light leakage and optically excellent performance was exhibited.

The entire disclosure of Japanese Application 2013-178861 is incorporated herein by reference.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims (7)

A structural unit derived from a monomer having a cyclic group and having a content ratio of 2% by mass to 9% by mass with respect to the total mass of the copolymer, a structural unit derived from a monomer having a hydroxyl group, and alkyl (meth) A (meth) acrylic copolymer containing a structural unit derived from acrylate;
A polyvalent isocyanate compound;
At least one curing accelerator selected from the group consisting of 1-benzyl-2-methylimidazole and 1-benzyl-2-phenylimidazole;
Containing
The content ratio of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer is 3.5% by mass to 6% by mass,
The (meth) acrylic copolymer has a weight average molecular weight of 800,000 to 1,800,000 and a dispersity (ratio of the weight average molecular weight to the number average molecular weight of the (meth) acrylic copolymer) is 4 to. A pressure-sensitive adhesive composition for a polarizing plate, which is 9. Furthermore, containing a silane coupling agent having a thiol group,
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the content of the silane coupling agent with respect to 100 parts by mass of the (meth) acrylic copolymer is 0.01 parts by mass to 1.5 parts by mass. The pressure-sensitive adhesive composition for a polarizing plate according to claim 2 , wherein the silane coupling agent having a thiol group is an oligomer type silane coupling agent. The content ratio of the structural unit derived from the monomer having a cyclic group to the structural unit derived from the monomer having a hydroxyl group is 0.3 to 2.57 on a mass basis. The pressure-sensitive adhesive composition for a polarizing plate according to any one of 3 . 4. The total content of the structural unit derived from the monomer having a cyclic group and the structural unit derived from the monomer having a hydroxyl group is based on the total mass of the (meth) acrylic copolymer . It is 5 mass% -15 mass%, The adhesive composition for polarizing plates of any one of Claims 1-4 . A polarizer,
On the said polarizer, the adhesive layer formed by provision of the adhesive composition for polarizing plates of any one of Claims 1-5 ,
A polarizing plate with an adhesive. The display apparatus provided with the display panel which displays an image, and the polarizing plate with an adhesive of Claim 6 arrange | positioned on the at least one surface of the display panel.