JP6422270B2 - 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 display devices for displaying images, such as liquid crystal display devices and organic electroluminescence display devices, devices of 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 supporting substrates such as glass, and an optical film such as a polarizing plate, a retardation film, and a brightness enhancement film. Are bonded together. An adhesive is used when laminating optical films or sticking an optical film to a liquid crystal cell.

  Liquid crystal display devices are widely used as display devices for personal computers, televisions, car navigation systems, etc. For example, various liquid crystal display devices such as harsh environmental conditions with a high amount of high temperature and high humidity and dry environmental conditions with low humidity. Used under environmental conditions. 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 that the pressure-sensitive adhesive layer has high durability such that bubbles are not easily generated.

  Many mobile devices such as mobile phones and personal digital assistants are equipped with a touch panel as well as a display device. It is required that the pressure-sensitive adhesive for polarizing plates used in a display device equipped with a touch panel does not contain an acid component so as not to corrode members of the touch panel.

  On the other hand, since the pressure-sensitive adhesive advances the cross-linking reaction, a long curing time of about one week is required at room temperature, and problems such as a decrease in productivity and an increase in inventory amount occur due to the long-term curing time. It was. Examples of a method for shortening the curing time include a method using a tin compound such as dibutyltin dilaurate. However, from the standpoint of environmental friendliness, regulations regarding the use of tin compounds are being studied, and there are concerns about safety. Therefore, there is a need for a curing shortening method other than the use of tin compounds. As another curing shortening method, there is a method of copolymerizing a monomer having a carboxyl group with a hydroxyl group-containing resin (see, for example, Patent Document 1). Furthermore, there is a method in which a resin having a hydroxyl group and a carboxyl group is combined with a tolylene diisocyanate compound having an isocyanurate structure as a crosslinking agent (see, for example, Patent Document 2).

JP 2004-91500 A International Publication No. 2011-0662127 Pamphlet

However, in the method for shortening the curing time as described above, since the resin constituting the pressure-sensitive adhesive contains an acid component, it is particularly difficult to apply to a display device equipped with a touch panel. In addition, in the case where the resin does not contain an acid component, sufficient durability may not be obtained. In addition, the adhesive composition with a short curing time, the crosslinking reaction proceeds even in the solution state, the solution viscosity tends to increase, and it is necessary to perform the coating work in a short time after mixing and mixing, and the coating film has a streak-like defect. May occur or may become a problem in the coating process.
The present invention provides a pressure-sensitive adhesive composition for a polarizing plate that can shorten the curing time while maintaining a sufficient pot life and has excellent durability, and a polarizing plate with a pressure-sensitive adhesive and a display device using the same. Is an issue.

  The present invention relates to a (meth) acrylic copolymer in which the content of a structural unit derived from a monomer having a hydroxyl group is in a specific range, an aromatic diisocyanate compound having an isocyanate structure, and a specific structure By combining N-substituted imidazole compounds having a specific content with a specific content, the curing time can be shortened while maintaining a sufficient pot life without containing an acid component, and excellent durability can be achieved. And has been completed based on such knowledge.

一般式（１）中、Ｒ^１は、アルキル基、アリール基、又はアラルキル基を示し、Ｒ^２はアリール基を示し、Ｒ^３〜Ｒ^４はそれぞれ独立に、水素原子、アルキル基、アリール基、又はアラルキル基を示す。またＲ^３及びＲ^４は互いに連結して、これらが結合する炭素原子とともに環を形成してもよい。 Specific means for solving the above problems are as follows.
<1> A (meth) acrylic copolymer comprising a structural unit derived from a monomer having a hydroxyl group and having a content of 0.5 to 8% by mass and a structural unit derived from an alkyl (meth) acrylate A compound, a partial structure derived from an aromatic diisocyanate compound, a polyvalent isocyanate compound having an isocyanurate ring structure, and an N-substituted imidazole compound represented by the following general formula (1): ) The content of the polyvalent isocyanate compound is 0.01 to 0.3 parts by mass and the content of the N-substituted imidazole compound is 0.02 to 0 parts by mass with respect to 100 parts by mass of the acrylic copolymer. It is an adhesive composition for polarizing plates which is 2 mass parts.

In General Formula (1), R ¹ represents an alkyl group, an aryl group, or an aralkyl group, R ² represents an aryl group, and R ^{3 to} R ⁴ each independently represent a hydrogen atom, an alkyl group, an aryl group, Or an aralkyl group is shown. R ³ and R ⁴ may be connected to each other to form a ring together with the carbon atom to which they are bonded.

<2> The (meth) acrylic copolymer is the pressure-sensitive adhesive composition for a polarizing plate according to <1>, further including a structural unit derived from a monomer having a cyclic group.

<3> A polarizing plate with an adhesive having a polarizer and an adhesive layer formed by applying the adhesive composition for a polarizing plate according to <1> or <2> on the polarizer.

<4> A display device comprising a display panel for displaying an image, and the polarizing plate with an adhesive according to <3> disposed on at least one surface of the display panel.

  According to the present invention, there are provided a pressure-sensitive adhesive composition for a polarizing plate, which can shorten the curing time while maintaining a sufficient pot life and has excellent durability, and a polarizing plate with a pressure-sensitive adhesive and a display device using the same. can do.

In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. . Moreover, the numerical 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. Furthermore, 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 hydroxyl group and has a content of 0.5% by mass to 8% by mass. (Meth) acrylic copolymer containing structural unit derived from unit and alkyl (meth) acrylate, partial structure derived from aromatic diisocyanate compound, polyisocyanate compound having isocyanurate ring structure, and specific structure An N-substituted imidazole compound having a content of 0.01 to 0.3 parts by mass of the polyvalent isocyanate compound with respect to 100 parts by mass of the (meth) acrylic copolymer, the N-substituted Content of an imidazole compound is 0.02 mass part-0.2 mass part. The polarizing plate pressure-sensitive adhesive composition may further contain other components such as a silane coupling agent and other additives as necessary.

  When the pressure-sensitive adhesive composition for polarizing plate has the above-described configuration, the curing time can be shortened while maintaining a sufficient pot life, and further, an appropriate crosslinking reaction rate, and excellent elasticity and viscosity. Therefore, it is possible to show excellent durability. In addition, the pressure-sensitive adhesive composition for polarizing plate has excellent durability even when the component (meth) acrylic copolymer does not have an acidic group, and has a shortened curing time. Since it becomes usable, it can be preferably applied to a display device including a touch panel.

  In the present invention, the (meth) acrylic copolymer contains a specific amount of a structural unit derived from a monomer having a hydroxyl group, and this is appropriately crosslinked with a polyvalent isocyanate compound having a specific structure. The (meth) acrylic copolymer containing a specific amount of a structural unit derived from a monomer having a hydroxyl group, a polyvalent isocyanate compound, and an N-substituted imidazole compound. It is considered that the adhesive composition for polarizing plate is excellent in durability because the crosslinking reaction rate is adjusted to an appropriate range by including a specific amount of the compound, and the adhesiveness to the substrate is excellent. Moreover, it is thought that a crosslinking reaction is accelerated | stimulated because a (meth) acrylic-type copolymer has a hydroxyl group and a polyvalent isocyanate compound has a specific structure, and curing time is shortened. Further, the (meth) acrylic copolymer contains a specific amount of a structural unit derived from a monomer having a hydroxyl group, and the polyvalent isocyanate compound and the N-substituted imidazole compound have a specific structure. While maintaining the pot life sufficiently, the crosslinking reaction is promoted, and it is considered that both the pot life and the shortening of the curing time can be achieved.

(A) (Meth) acrylic copolymer The pressure-sensitive adhesive composition for polarizing plate is derived from a monomer having a hydroxyl group, and the content is at least one of structural units of 0.5 mass% to 8 mass%. It contains at least one kind of (meth) acrylic copolymer (hereinafter also simply referred to as “copolymer”) containing a seed and at least one structural unit derived from alkyl (meth) acrylate. The (meth) acrylic copolymer further contains a monomer having a hydroxyl group, an alkyl (meth) acrylate, and, if necessary, another monomer, and the content of the monomer containing a hydroxyl group is 0. It is a copolymer obtained by copolymerizing a monomer composition of 0.5 mass% to 8 mass%.
When the monomer composition contains other monomers, the (meth) acrylic copolymer is added to the structural unit derived from a monomer containing a hydroxyl group and the structural unit derived from an alkyl (meth) acrylate. Constituent units derived from other monomers are included.

  The (meth) acrylic copolymer may be a random copolymer or a block copolymer, but is preferably a random copolymer.

  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 light leakage is suppressed when applied to a polarizing plate of a display device. it can.

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. Mention may be made of alcohol derivatives. Among them, the monomer having a hydroxyl group is preferably hydroxyalkyl (meth) acrylate, and more preferably 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. Moreover, 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.
Monomers having a hydroxyl group may be used alone or in combination of two or more.

  The content rate of the structural unit derived from the monomer which has a hydroxyl group in a (meth) acrylic-type copolymer is 0.5 mass%-8 mass% in the total mass of a (meth) acrylic-type copolymer, From the viewpoint of durability, shortening of the curing time and pot life, the content is preferably 2% by mass to 8% by mass, and more preferably 2% by mass to 6% by mass. If the content of the structural unit derived from the monomer having a hydroxyl group is less than 2% by mass, sufficient durability and shortening of the curing time cannot be achieved. Moreover, when the content rate of the structural unit derived from the monomer which has a hydroxyl group exceeds 8 mass%, there exists a tendency which cannot maintain the outstanding durability and sufficient pot life.

  The (meth) acrylic copolymer is a hydroxyalkyl having 2 to 6 carbon atoms in the alkyl group as a structural unit derived from a monomer having a hydroxyl group from the viewpoint of durability, shortening the curing time and pot life. It is preferable to contain 0.5% by mass to 8% by mass of a structural unit derived from (meth) acrylate, and 2% by mass of a structural unit derived from hydroxyalkyl (meth) acrylate having 2 to 4 carbon atoms in the alkyl group portion. It is more preferable to include 8% by mass, and it is further preferable to include 2% to 6% by mass of a structural unit derived from a hydroxyalkyl acrylate having 2 to 4 carbon atoms in the alkyl group portion.

  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 these, alkyl (meth) acrylates are preferably alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl group, and those having 1 to 12 carbon atoms in the alkyl group in that the cohesive force and adhesive strength of the pressure-sensitive adhesive can be easily adjusted. The alkyl (meth) acrylate is more preferable, and the alkyl acrylate having 1 to 6 carbon atoms in the alkyl group is more preferable.
An alkyl (meth) acrylate may be used individually by 1 type, or may be used in combination of 2 or more type.

  The structural unit derived from the alkyl (meth) acrylate is preferably contained as a main component constituting the (meth) acrylic copolymer, and the content thereof is in the total mass of the (meth) acrylic copolymer. 60% by mass or more, more preferably 80% by mass or more, and still more preferably 85% by mass or more. When the content ratio of 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.

  The (meth) acrylic copolymer includes a structural unit derived from a monomer having a cyclic group in addition to a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth) acrylate. It is preferable that it contains a structural unit derived from a monomer having an aromatic ring group. When the (meth) acrylic copolymer further includes a structural unit derived from a monomer having a cyclic group, 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 is a polymerizable compound having at least one cyclic group in the molecule and copolymerizable with 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 group. Or it is more preferable that it is (meth) acrylate ester-bonded via a polyoxyalkylene group, and it is especially preferable that the aromatic ring group is (meth) acrylate ester-bonded via an oxyalkylene group.

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, a monomer having a cyclic group has an aromatic ring group such as phenoxyethyl (meth) acrylate, phenoxypropyl (meth) acrylate, and β-naphthyloxyethyl (meth) acrylate, which is ester-bonded via an oxyalkylene group (meta). ) Acrylate is preferred.
The monomer which has a cyclic group may be used individually by 1 type, or may be used in combination of 2 or more type.

  When the (meth) acrylic copolymer includes a structural unit derived from a monomer having a cyclic group, the content is 1% by mass to 10% by mass in the total mass of the (meth) acrylic copolymer. %, More preferably 2% by mass to 9% by mass, and still more preferably 3% by mass to 7% by mass. When the content of the structural unit derived from the monomer having a cyclic group is within the above range, the problem of odor due to the monomer having a cyclic group hardly occurs, and light leakage occurs when applied to a polarizing plate of a display device. It can suppress more effectively.

The (meth) acrylic copolymer is composed of a monomer having a hydroxyl group, an alkyl (meth) acrylate, and a structural unit derived from a monomer having a cyclic group, if necessary, in addition to these other units. A structural unit derived from a monomer 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.

  It is preferable that the content rate of the structural unit derived from the monomer which has an acidic group in a (meth) acrylic-type copolymer is 0.5 mass% or less in the total mass of a (meth) acrylic-type copolymer. More preferably, it is 0.2 mass% or less, and it is still more preferable not to contain substantially. Here, “substantially free” means that the presence of a structural unit derived from a monomer having an acidic group that is inevitably mixed is allowed.

The weight average molecular weight (Mw) of the (meth) acrylic copolymer is not particularly limited, and can be, for example, 800,000 to 1,800,000, preferably 1,000,000 to 1,800,000, and 1.3 million to 1,800,000. More preferably. When the weight average molecular weight is in the above range, the handling property and durability at the time of coating of the adhesive composition for polarizing plate are excellent.
Moreover, the dispersity (Mw / Mn) of the (meth) acrylic copolymer is not particularly limited, and can be, for example, 2 to 10, preferably 4 to 9, and more preferably 5 to 8. preferable. When the dispersity is in the above range, the durability is excellent.

  The weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth) acrylic copolymer can be measured under normal conditions using gel permeation chromatography (GPC).

  The (meth) acrylic copolymer is produced by polymerizing a monomer composition containing a monomer having a hydroxyl group, an alkyl (meth) acrylate, and a monomer having a cyclic group that is included as necessary. be able to. 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) Polyisocyanate Compound The pressure-sensitive adhesive composition for polarizing plates of the present invention comprises a partial structure derived from an aromatic diisocyanate compound and a polyisocyanate compound having an isocyanurate ring structure (hereinafter simply referred to as “polyisocyanate compound”). At least one kind). For example, the polyvalent isocyanate compound acts as a crosslinking agent for the (meth) acrylic copolymer in the pressure-sensitive adhesive composition for polarizing plates. The (meth) acrylic copolymer includes a structural unit derived from a monomer having a hydroxyl group in a specific range, and the polyvalent isocyanate compound has a specific structure, so that excellent durability and shortening of the curing time can be achieved. Can be compatible.

  In the present invention, it is necessary to use a polyvalent isocyanate compound having a partial structure derived from an aromatic diisocyanate compound and an isocyanurate ring structure. For example, a polyvalent isocyanate compound having a partial structure derived from an aromatic diisocyanate and not having an isocyanurate ring structure, and a polyvalent isocyanate compound having no partial structure derived from an aromatic diisocyanate and having an isocyanurate ring structure In such cases, the effect of shortening the curing time tends not to be sufficiently obtained.

  The polyvalent isocyanate compound is not particularly limited as long as it is a compound having a partial structure derived from an aromatic diisocyanate compound and an isocyanurate ring structure. Among these, the polyvalent isocyanate compound is preferably a polyvalent isocyanate compound in which each isocyanate group in a plurality of aromatic diisocyanate compounds forms an isocyanurate ring structure by an addition reaction. 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, more preferably tolylene diisocyanate. More preferred is at least one selected from 1,4-tolylene diisocyanate and 2,6-tolylene diisocyanate.

Specifically as a polyvalent isocyanate compound, the compound which is a trimer of the aromatic diisocyanate compound represented by the following general formula (2), the pentamer of the aromatic diisocyanate compound represented by the following general formula (3) 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 (2) and General Formula (3), R ¹¹ to R ²⁵ each independently represent a hydrogen atom or a methyl group. One of R ^{11 to} R ¹³ is preferably a methyl group and the remainder is a hydrogen atom. One of R ^{14 to} R ¹⁶ is preferably a methyl group and the remainder is a hydrogen atom. One of R ^{17 to} R ¹⁹ is preferably a methyl group and the remainder is a hydrogen atom. One of R ^{20 to} R ²² is preferably a methyl group and the remainder is a hydrogen atom. One of R ^{23 to} R ²⁵ is preferably a methyl group and the remainder is 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 products of the polyvalent isocyanate compound include, for example, trade names “Desmodule IL1451CN”, “Desmodule ILBA”, “Desmodule HL”, “Sumijour FL-2”, “Sumijo” manufactured by Sumitomo Bayer Urethane Co., Ltd. "Joule FL-3" and "SBU Isocyanate 0817", trade names "Coronate 2030" and "Coronate 2037" manufactured by Nippon Polyurethane Industry Co., Ltd., and trade names "Polureen KC" and "Polurene HR" manufactured by SAPCI be able to.

  In the pressure-sensitive adhesive composition for polarizing plate, the content of the polyvalent isocyanate compound is preferably in the range of 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. Is in the range of 0.05 to 0.3 parts by weight, more preferably in the range of 0.05 to 0.2 parts by weight. When the content of the polyvalent isocyanate compound is less than 0.01 parts by mass, the crosslinking reaction does not proceed sufficiently, the cohesive force is insufficient, and the adhesiveness and durability tend not to be sufficiently obtained. Moreover, when content of a polyvalent isocyanate compound exceeds 0.3 mass part, there exists a tendency for durability to deteriorate or pot life not being fully obtained.

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 isocyanate-based crosslinking agents other than polyvalent isocyanate compounds having a partial structure derived from aromatic diisocyanate and having no isocyanurate ring structure, and epoxy-based crosslinking agents.
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. For example, it is 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) Imidazole compound The pressure-sensitive adhesive composition for polarizing plates contains at least one N-substituted imidazole compound represented by the general formula (1). The N-substituted imidazole compound represented by the general formula (1) functions as, for example, a curing accelerator in the polarizing plate pressure-sensitive adhesive composition. When the pressure-sensitive adhesive composition for polarizing plate contains the N-substituted imidazole compound represented by the general formula (1), the curing time can be further shortened while maintaining excellent durability and sufficient pot life. .

In General Formula (1), R ¹ represents an alkyl group, an aryl group, or an aralkyl group, R ² represents an aryl group, and R ^{3 to} R ⁴ each independently represent a hydrogen atom, an alkyl group, an aryl group, Or an aralkyl group is shown. R ³ and R ⁴ may be connected to each other to form a ring together with the carbon atom to which they are bonded.

  In general formula (1), the alkyl group may be linear or branched. Moreover, it is preferable that carbon number of an alkyl group is 1-2. The aryl group in the general formula (1) preferably has 6 to 10 carbon atoms, and more preferably a phenyl group or a naphthyl group. The aralkyl group in the general formula (1) 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 (1), R ¹ is an alkyl group or an aralkyl group, R ² is an aryl group, R ³ and R ⁴ are from the viewpoint of shortening pot life and curing time. Preferably each independently represents a hydrogen atom, an alkyl group or an aryl group, R ¹ is an aralkyl group, R ² is an aryl group, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group. More preferred is 1-benzyl-2-phenylimidazole, and even more preferred.

  In the pressure-sensitive adhesive composition for polarizing plate, the content of the N-substituted imidazole compound represented by the general formula (1) is 0.02 parts by mass to 100 parts by mass of the (meth) acrylic copolymer. It is the range of 0.2 mass part, and the range of 0.02 mass part-0.1 mass part is preferable. When the content of the N-substituted imidazole compound represented by the general formula (1) is 0.02 parts by mass or more, the effect of shortening the curing time is sufficient. Further, when the content of the N-substituted imidazole compound represented by the general formula (1) is within 0.2 parts by mass, the crosslinking reaction rate is appropriate, and excellent durability and sufficient pot life can be obtained. .

  In the pressure-sensitive adhesive composition for polarizing plate, 0.02 parts by mass to 0.2 parts by mass of 1-benzyl-2-phenylimidazole as an N-substituted imidazole compound with respect to 100 parts by mass of the (meth) acrylic copolymer. It is preferable to include within the range of parts.

(D) 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, the pressure-sensitive adhesive composition for polarizing plates tends to exhibit better adhesion 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, 3 Silane coupling agents having a thiol group such as mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane; 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like Coupling agent having epoxy group: 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane 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 the silane coupling agents, from the viewpoint of durability and reworkability, it is preferable to use at least one selected from silane coupling agents having a thiol group, and selected from oligomer-type silane coupling agents having a thiol group. More preferably, at least one kind is used. 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 mass parts is preferable, The range of 0.05 mass part-3 mass parts is more preferable, The range of 0.1 mass part-1.5 mass parts is still more preferable.

(E) Other components In addition to the above-mentioned components, the pressure-sensitive adhesive composition for polarizing plates further comprises weather resistance stabilizers such as solvents and ultraviolet absorbers, tackifiers, plasticizers, softeners, dyes, and pigments as necessary. In addition, an inorganic filler or the like may be contained. When the pressure-sensitive adhesive composition for polarizing plates contains other components, the content can be appropriately selected within a range that does not impair 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 composition may be applied on the polarizing plate, but is preferably applied on a protective sheet (release 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 an immersion method, a coating method, or an ink jet method using the 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 pressure-sensitive adhesive composition applied on the protective sheet (release sheet) is preferably dried at 70 ° C. to 120 ° C. under drying conditions 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 it. 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 configured by providing 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 surfaces of the liquid crystal display panel so that the pressure-sensitive adhesive layer contacts 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.
Example 8 is a reference example of the present invention.

(Production Example 1)
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 96 parts by mass of n-butyl acrylate (BA), 4 parts by mass of 2-hydroxyethyl acrylate (2HEA), ethyl acetate (EAc) ) After 90 parts by mass was added and mixed, the inside of the reaction vessel was purged 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.
When the weight average molecular weight (Mw) and number average molecular weight (Mn) of the obtained (meth) acrylic copolymer were measured under the following conditions using gel permeation chromatography (GPC), the weight average molecular weight (Mw) was measured. Was 1.52 million and the dispersity (Mw / Mn) was 6.8.
[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 6)
In Production Example 1, in 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 Table 1 below, ) Solutions of acrylic copolymers 2-6 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 Table 1, “BA” indicates n-butyl acrylate, “PHEA” indicates phenoxyethyl acrylate, “2HEA” indicates 2-hydroxyethyl acrylate, and “−” indicates that the compound is not blended.

<Example 1>
-Preparation of adhesive composition-
As a (meth) acrylic copolymer (in the table, “copolymer”), 100 parts by mass (solid content) of the (meth) acrylic copolymer 1 obtained in Production Example 1 and a polyvalent isocyanate 0.125 parts by mass (solid content) of Coronate 2037 (manufactured by Nippon Polyurethane Industry Co., Ltd.) as a compound (crosslinking agent) and Curesol 1B2PZ (manufactured by Shikoku Kasei Co., Ltd.) as a tertiary imidazole compound (curing accelerator) Benzyl-2-phenylimidazole) is 0.03 part by mass, and X-41-1810 (manufactured by Shin-Etsu Chemical Co., Ltd., oligomer type having a thiol group) is used as a silane coupling agent. The mixture was stirred and mixed to obtain an adhesive composition.

(Pot life)
The pot life of the pressure-sensitive adhesive composition obtained above was evaluated by measuring the viscosity as follows and calculating the viscosity increase rate.
The pressure-sensitive adhesive composition was adjusted with ethyl acetate so that the viscosity became 1500 mPa · s, and then the viscosity (a) at 25 ° C., 1 minute, and 10 rpm was measured with a BH type rotational viscometer. 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: Viscosity increase rate (%) is less than 110% B: Viscosity increase rate (%) is 110% or more and less than 120% C: Viscosity increase rate (%) is 120% or more

(Curing time)
The time required for curing (curing time) of the pressure-sensitive adhesive composition obtained above was evaluated by measuring the gel fraction as follows.
A film-like pressure-sensitive adhesive layer was prepared on a release film obtained by surface-treating the pressure-sensitive adhesive composition solution with a silicone-based release agent so that the thickness after drying was 25 μm. Next, the produced pressure-sensitive adhesive layer was stored in an environment of 23 ° C. × 50% RH, and the gel fraction after 24 hours, 48 hours, 72 hours, and 168 hours after the start of storage was measured as follows. did. The difference in gel fraction for each storage time was within 3%, and the first storage period when there was no change after 168 hours was judged as the end of curing.

The gel fraction was measured by the following method.
1. About 0.25 g of a film-like pressure-sensitive adhesive layer is applied to a precisely weighed 250-mesh wire mesh (100 mm × 100 mm) and wrapped 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 removed, 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). The gel fraction is calculated by the following formula.
Gel fraction (mass%) = (Z−X) / (Y−X) × 100
Where X is the mass of the wire mesh (g), Y is the mass of the wire mesh with the adhesive layer attached (weight of the adhesive layer) (g), Z is the mass of the wire mesh that has been immersed and dried (mass of gel resin) (g )

-Evaluation criteria-
A: Curing is completed for 24 hours.
B: Curing is completed for 48 hours.
C: Curing end is 72 hours or more.

(durability)
The pressure-sensitive adhesive composition obtained above was applied to the release agent-treated surface of the release film surface-treated with a silicone-based 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 one day under an environmental condition of 23 ° C. and 65% RH, and a polarizing film having a laminate structure of a release film / adhesive layer / polarizing base film was produced as an optical film sample.

About the polarizing film sample obtained by making it above, it cuts into the rectangular shape of 140 mm x 260 mm so that a long side may be set to 0 degrees with respect to an absorption axis, and a 0.7 mm-thick Corning non-alkali glass plate " A test piece was prepared by sticking to one side of “Eagle XG” using a laminator. 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 of 80 ° C. or 60 ° C. and 90% RH, the condition of foaming or peeling was confirmed and evaluated according to the following evaluation criteria.

-Evaluation criteria-
A: No foaming was observed. Further, no peeling was observed at a position of 0.2 mm or more inward from the outer peripheral portion.
B: Almost no foaming was observed. Alternatively, peeling was observed at a position of 0.2 mm or more inward from the outer peripheral portion, but peeling was not observed at a position of 0.5 mm or more.
C: Slight foaming was observed. Alternatively, peeling was observed at a position of 0.5 mm or more inward from the outer peripheral portion, but peeling was not observed at a position of 1.0 mm or more.
D: Foaming was recognized remarkably. Or peeling was recognized in the position of 1.0 mm or more inside from the outer peripheral part.

<Examples 2-8, Comparative Examples 1-9>
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 2 and 3 below, and an optical film sample was prepared using this. Were prepared.
The obtained adhesive composition was evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 2 and 3.
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)
Coronate 2037: made by Nippon Polyurethane Industry Co., Ltd., isocyanurate of tolylene diisocyanate Coronate L: made by Nippon Polyurethane Industry Co., Ltd., trimethylolpropane adduct of tolylene diisocyanate (silane coupling agent)
X-41-1810: manufactured by Shin-Etsu Chemical Co., Ltd., oligomer type having a thiol group (curing accelerator)
1B2PZ: Shikoku Kasei Kogyo Co., Ltd., 1-benzyl-2-phenylimidazole 1B2MZ: Shikoku Kasei Kogyo Co., Ltd., 1-benzyl-2-methylimidazole

  From Table 2 and Table 3, it can be seen that in the pressure-sensitive adhesive composition of the present invention, the curing time can be shortened as compared with the conventional one while maintaining a sufficient pot life. Moreover, it turns out that the optical film sample produced using this has the outstanding durability even after the curing time 1 day, and can be used with a short curing time.

Claims (4)

A (meth) acrylic copolymer derived from a monomer having a hydroxyl group and containing a structural unit having a content of 2 % by mass to 8% by mass and a structural unit derived from an alkyl (meth) acrylate;
A partial structure derived from an aromatic diisocyanate compound, and a polyvalent isocyanate compound having an isocyanurate ring structure;
An N-substituted imidazole compound represented by the following general formula (1):
A silane coupling agent having a thiol group ,
The content of the polyvalent isocyanate compound is 0.01 parts by mass to 0.3 parts by mass, and the content of the N-substituted imidazole compound is 0.01 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. part to 0.2 parts by weight of der is,
The said (meth) acrylic-type copolymer is an adhesive composition for polarizing plates which does not contain the structural unit derived from the monomer which has an acidic group substantially .

(In the formula, R ¹ represents an alkyl group, an aryl group, or an aralkyl group, R ² represents an aryl group, and R ^{3 to} R ⁴ each independently represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group. R ³ and R ⁴ may be connected to each other to form a ring together with the carbon atom to which they are bonded.)   The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the (meth) acrylic copolymer further includes a structural unit derived from a monomer having a cyclic group.   The polarizing plate with an adhesive which has a polarizer and the adhesive layer formed by provision of the adhesive composition for polarizing plates of Claim 1 or Claim 2 on the said polarizer. The display apparatus provided with the display panel which displays an image, and the polarizing plate with an adhesive of Claim 3 arrange | positioned on the at least one surface of the display panel.