JPH09292518A - Elliptical polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong time allowed to elapse before the sticking of a polarizing plate to a phase difference plate and to obtain an elliptical polarizing plate less liable to cause the peeling of the polarizing plate from an adhesive layer. SOLUTION: A polarizing plate 16 is laminated to an adhesive layer 13 on one side of a phase difference plate 11 to obtain the objective elliptical polarizing plate. The adhesive layer 13 is made of an adhesive compsn. obtd. by copolymerizing a monomer compsn. based on alkyl (meth)acrylate having a 2-12C alkyl group and contg. 0.1-10wt.% vinyl monomer having a sec. or tert. hydroxyl group and copolymerizable with the alkyl (meth)acrylate and 0-5wt.% vinyl monomer having a carboxyl group but not practically contg. a vinyl monomer having a prim. hydroxyl group and then crosslinking the resultant acrylic polymer with a polyisocyanate compd. as a crosslinking agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elliptically polarizing plate obtained by laminating a polarizing plate on a retardation plate with an adhesive layer interposed between the retardation plate and the retardation plate. The present invention relates to an elliptically polarizing plate which is integrated by laminating a polarizing plate on a sheet and has excellent adhesion between the pressure-sensitive adhesive layer and the polarizing plate.

[0002]

2. Description of the Related Art In recent years, Super Twisted Nematic (STN) has been used as a liquid crystal display device having excellent contrast.
A liquid crystal display device utilizing the birefringence of liquid crystal is generally used. However, since this liquid crystal display device utilizes the birefringence of STN liquid crystal, there is a problem in that when only a polarizing plate is used, the display is colored and color display cannot be performed.

Therefore, as shown in FIG. 1, a structure in which an elliptically polarizing plate is attached to a glass plate 2 constituting a liquid crystal display cell of a liquid crystal display device is generally used. The elliptically polarizing plate 3 has a structure in which a pressure-sensitive adhesive layer 4, a retardation plate 5, a pressure-sensitive adhesive layer 6, and a polarizing plate 7 for laminating the glass plate 2 of the liquid crystal display device are laminated. This is to form an elliptically polarizing plate by bonding the retardation plate 5 and the polarizing plate 7 together, thereby preventing coloring due to the birefringence of the STN liquid crystal.

In manufacturing the elliptically polarizing plate 3, a polarizing plate 7 having a pressure-sensitive adhesive layer 6 provided on one side is conventionally used, and the pressure-sensitive adhesive layer 6 is provided on the side where the pressure-sensitive adhesive layer 4 of the retardation plate 5 is provided. It was done by adhering to the surface opposite to.

However, the retardation plate 5 is generally made of a hydrophobic plastic such as polycarbonate. Therefore, the above manufacturing method has a problem that it is difficult to obtain a sufficient adhesive force at the interface between the retardation plate 5 and the pressure-sensitive adhesive layer 6.

Therefore, in order to enhance the adhesive force at the interface between the retardation plate 5 and the pressure-sensitive adhesive layer 6, a surface of the retardation plate 5 to which the pressure-sensitive adhesive layer 6 is closely adhered is subjected to a corona treatment in advance (Japanese Patent Laid-Open No. Hei. No. 347802), or a method of forming a pressure-sensitive adhesive layer on both surfaces of a retardation plate and then attaching a polarizing plate to one pressure-sensitive adhesive layer (Japanese Patent Laid-Open No. 2-197819).

[0007]

However, in the method of subjecting the surface of the retardation plate on the polarizing plate side to corona treatment, the number of steps is increased due to the corona treatment, resulting in a high cost. was there.

Further, in the method of forming the pressure-sensitive adhesive layer on both surfaces of the retardation plate and then laminating the polarizing plates, the anchor effect of the pressure-sensitive adhesive to the retardation plate can be obtained,
The adhesive force at the interface between the retardation plate and the pressure-sensitive adhesive layer can be increased.

However, when a general acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, the gel fraction of the pressure-sensitive adhesive increases in about 1 to 2 days, the cohesive force becomes too high, and the polarized light There is a problem that the time during which the plates can be stuck together is limited to a short time. That is, the pressure-sensitive adhesive layer, the gel fraction increases with time after being applied to the retardation plate,
The cohesive force becomes high. Therefore, before the gel fraction of the pressure-sensitive adhesive layer becomes too high, specifically, if the polarizing plate is not attached in a state of 70% or less of the saturated gel fraction, the adhesive force between the polarizing plate and the pressure-sensitive adhesive layer will be increased. Cannot be increased.

Therefore, when the retardation plate is provided with the pressure-sensitive adhesive layer as described above and the polarizing plates are not attached in a short time, and the polarizing plates are attached after a considerable period of time, Since the anchor effect between the adhesive layer and the polarizing plate cannot be expected, the obtained elliptical polarizing plate has a problem that peeling easily occurs at the interface between the adhesive layer and the polarizing plate.

Further, since the elliptically polarizing plate is required to have a light-transmitting property, an acrylic pressure-sensitive adhesive having excellent transparency is usually used as the pressure-sensitive adhesive layer, and the functional monomer is (meth) acrylate. Cohesion is enhanced by copolymerization and crosslinking of the resulting acrylic copolymer, and a tackifier is added as necessary to adjust the tackiness.

However, as the functional monomer, a carboxyl group-containing vinyl monomer such as acrylic acid and a vinyl monomer having a primary hydroxyl group are often used, and a polyisocyanate compound is usually used as a crosslinking agent. Since the crosslinking rate of the vinyl-based monomer having a primary hydroxyl group is high, the rise of the gel fraction rises quickly, and if the polarizing plate is not attached in a short time, it peels at the interface between the pressure-sensitive adhesive layer and the polarizing plate as described above. There is a problem that is likely to occur.

The object of the present invention is to solve the problems of the conventional elliptically polarizing plate obtained by laminating a polarizing plate on a retardation plate having adhesive layers on both sides, and to reduce the time until the polarizing plate is laminated. An object of the present invention is to provide an elliptically polarizing plate which can be extended and is therefore easy to manufacture and in which the adhesive force between the pressure-sensitive adhesive layer and the polarizing plate is effectively enhanced.

[0014]

Means for Solving the Problems The inventor of the present application produced various elliptically polarizing plates by laminating polarizing plates on a retardation plate having adhesive layers on both sides, and conducted durability tests thereof.
At the interface between the polarizing plate and the pressure-sensitive adhesive layer in contact with the polarizing plate, it was found that peeling is likely to occur particularly during the heat resistance test, and the degree of peeling varies depending on the time until the polarizing plate is bonded after coating the pressure-sensitive adhesive. It was Therefore, as a result of various studies to obtain a stable interfacial adhesion even after extending the time from applying the pressure-sensitive adhesive to laminating the polarizing plate, a specific alkyl (meth) acrylate as a main component and a specific functional The inventors have found that the above problems can be achieved by using an acrylic pressure-sensitive adhesive obtained by crosslinking an acrylic polymer obtained by copolymerizing a monomer having a group with a specific crosslinking agent, and have completed the present invention.

That is, the present invention is an elliptical polarizing plate in which a polarizing plate is laminated on a retardation plate via an adhesive layer provided on the retardation plate, and the adhesive layer has 2 carbon atoms.
A vinyl-based monomer having a secondary or tertiary hydroxyl group, which does not substantially include a vinyl-based monomer having a primary hydroxyl group, and which contains an alkyl (meth) acrylate having an alkyl group of 12 to 0.1 as a main component. An acrylic polymer obtained by copolymerizing 10% by weight and a monomer composition containing 0 to 5% by weight of a vinyl monomer having a carboxyl group,
It is characterized by being constituted by a pressure-sensitive adhesive composition containing a polyisocyanate compound as a crosslinking agent.

The details of the present invention will be described below. Adhesive layer The alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms is not particularly limited, and ethyl acrylate, butyl acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth ) Acrylate etc. can be mentioned.

As the vinyl monomer having a secondary or tertiary hydroxyl group, an appropriate vinyl monomer having a secondary or tertiary hydroxyl group which is copolymerizable with the above-mentioned alkyl (meth) acrylate can be used. -Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxypentyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate and the like. be able to.

The vinyl monomer having a secondary or tertiary hydroxyl group is used in an amount of 0.1 to 10% by weight, preferably 1 to 5% by weight, based on the whole monomer composition.
When it is less than 0.1% by weight, the cohesive force of the pressure-sensitive adhesive layer is insufficient, and when it exceeds 10% by weight, the cohesive force becomes too high.
This is because peeling easily occurs at the interface between the pressure-sensitive adhesive layer and the polarizing plate.

As for the vinyl monomer having a carboxyl group, an appropriate carboxyl group-containing vinyl monomer copolymerizable with the alkyl (meth) acrylate may be used. For example, (meth) acrylic acid,
Examples thereof include those having crotonic acid, maleic acid, fumaric acid, itaconic acid and the like. The vinyl monomer having a carboxyl group may not be used to obtain the acrylic polymer, but when the cohesive force of the pressure-sensitive adhesive is insufficient only with the vinyl monomer having a secondary or tertiary hydroxyl group, When it is used in an amount of 5% by weight or less as described above, the cohesive force can be supplemented and other performances of the pressure-sensitive adhesive are not deteriorated.

The amount of the vinyl monomer having a carboxyl group used is 5% by weight or less based on the whole monomer composition. If it exceeds 5% by weight, the cohesive strength becomes too high,
This is because peeling easily occurs at the interface between the pressure-sensitive adhesive layer and the polarizing plate.

In the present invention, a vinyl-based monomer having a primary hydroxyl group should not be used substantially because it has a high crosslinking rate, but it is used within a range that does not impair the gist of the present invention in terms of adjusting the crosslinking rate. That is not a hindrance. However, in this case as well, the total monomer content of
It should be up to 1% by weight.

To obtain the above-mentioned acrylic polymer, monomers having a high glass transition point such as vinyl acetate, styrene, N-vinylpyrrolidone and acrylonitrile, and those having a low glass transition point such as tetrafurfuryl acrylate and polyethylene glycol acrylate are used. May be copolymerized, whereby the hardness of the acrylic polymer can be adjusted.

In the elliptically polarizing plate according to the present invention, a tacky acrylic polymer is obtained by copolymerizing the above monomer components. The polymerization method is not particularly limited, and solution polymerization, bulk polymerization, emulsion polymerization, and other radical polymerization methods are common, and the polymerization initiator in this case is known as benzoyl peroxide, azobisisobutyronitrile, or the like. Any thing can be used. Moreover, you may perform the said superposition | polymerization by irradiating light, a radiation, etc.

The acrylic polymer is cross-linked with the above-mentioned specific cross-linking agent, whereby the cohesive force can be adjusted to an optimum range. Examples of the polyisocyanate compound as a cross-linking agent include, for example, tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and the like, and addition products such as tolylene diisocyanate adducts of trimethylolpropane. It may be.

Usually, the polarizing plate has a protective layer made of saponified triacetyl cellulose on its surface. Therefore, the isocyanate group of the polyisocyanate compound as the cross-linking agent reacts with the hydroxyl group of the saponified triacetyl cellulose, thereby effectively increasing the adhesion at the interface between the pressure-sensitive adhesive layer and the polarizing plate. In particular, in the pressure-sensitive adhesive layer on the side where the polarizing plate is laminated, since the time until the acrylic polymer and the isocyanate group react is relatively long, the isocyanate group is a hydroxyl group of saponified triacetyl cellulose on the polarizing plate surface. Since there are many opportunities to react with, the adhesion effect between the pressure-sensitive adhesive layer and the polarizing plate can be more effectively enhanced by the anchor effect of the pressure-sensitive adhesive itself.

In the present invention, when the carboxyl group-containing vinyl monomer is copolymerized, other crosslinking agent may be used in combination with the above polyisocyanate compound as a crosslinking agent. An organic cross-linking agent,
One or more selected from the group consisting of organometallic compounds and metal salts can be used in combination.

Specific examples of the compound used in combination include N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and N, N'-diphenylmethane-1,6-. Bifunctional or higher functional aziridine compounds such as bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, epoxy resins such as bisphenol A, ethylene glycol diglycidyl ether, triglycidyl ether, di- Organic compounds such as epoxy compounds such as glycidyl aniline and diglycidyl amine; aluminum,
Coordination compounds of acetylacetone or acetoacetic acid ester of polyvalent metal such as titanium and iron; metal salts such as cupric chloride, aluminum chloride, ferric chloride and aluminum sulfate can be mentioned.

The above polyisocyanate compound is used in an amount suitable for cross-linking the acrylic polymer, and is, for example, 0.5 to 10 with respect to 100 parts by weight of the acrylic polymer.
It is blended in a ratio of parts by weight. Crosslinking agent content is 0.5
If it is less than parts by weight, the acrylic polymer cannot be sufficiently crosslinked, and adhesive residue may occur, or the unreacted isocyanate group may decrease and the adhesion with the polarizing plate may decrease. If the amount is more than 10 parts by weight, the crosslinking will proceed rapidly and the cohesive force of the pressure-sensitive adhesive layer will be too high by the time the polarizing plates are bonded together. You may not be able to

Other Configuration of Elliptic Polarizing Plate The elliptic polarizing plate according to the present invention is characterized in that the above-mentioned specific adhesive layer is used on the side where the polarizing plate is laminated. It is not limited. That is, in the elliptically polarizing plate according to the present invention, the pressure-sensitive adhesive layer is provided on both surfaces of the retardation plate, the polarizing plate is laminated on one pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer on which the polarizing plate is laminated. Is composed of the above specific adhesive. Therefore, as the retardation plate, those made of polycarbonate, polysulfone, etc., which are commonly used in this type of elliptically polarizing plate, can be used.

The pressure-sensitive adhesive layer on the side opposite to the side where the polarizing plate is laminated is not particularly limited, and a commonly used acrylic pressure-sensitive adhesive can be used.
In particular, when sticking to the glass surface of a liquid crystal display device, it is preferable to use an acrylic pressure-sensitive adhesive layer having excellent transparency, and its molecular weight and molecular weight distribution so that foaming and peeling do not occur under high temperature and high humidity. , Those optimized by a crosslinking agent, a tackifier, a coupling agent and the like are used.

The method of applying the pressure-sensitive adhesive to the retardation plate is not particularly limited, and for example, each of the pressure-sensitive adhesives on both sides of the separator may have a thickness after drying of 10 to 40 μm, preferably about 20 to 30 μm. It is possible to generally use a transfer method in which the above is applied, and these are dried and then attached to both surfaces of the retardation plate.

When the thickness of the pressure-sensitive adhesive layer is less than 10 μm, the adhesion may be insufficient when the polarizing plates are bonded together, and when it exceeds 40 μm, foaming is likely to occur in the pressure-sensitive adhesive layer when heated. is there.

As the polarizing plate, one made of an appropriate material conventionally used in optical parts such as liquid crystal display devices can be used, and one having a triacetyl cellulose protective layer formed on both surfaces of polyvinyl alcohol is exemplified. can do.

In the production of the elliptically polarizing plate of the present invention, the retardation plate having the pressure-sensitive adhesive layer formed on both sides as described above is applied to the pressure-sensitive adhesive layer side formed of the above-mentioned specific pressure-sensitive adhesive layer. It suffices if the polarizing plates are attached to each other, whereby the elliptically polarizing plate can be completed.

Action In the elliptically polarizing plate according to the present invention, the pressure-sensitive adhesive layer on the side on which the polarizing plate is laminated is mainly composed of an alkyl (meth) acrylate having an alkyl group having 2 to 12 carbon atoms,
Containing substantially no vinylic monomer having a primary hydroxyl group, 0.1 to 10% by weight of the vinylic monomer having a secondary or tertiary hydroxyl group, and 0 to 10% of the vinylic monomer having a carboxyl group. Since the main component is a pressure-sensitive adhesive composition obtained by crosslinking an acrylic polymer obtained by copolymerizing a monomer composition containing 5% by weight with a polyisocyanate compound, the progress of gelation in the pressure-sensitive adhesive layer is slow and cross-linking occurs. The polyisocyanate compound as an agent may remain unreacted in the pressure-sensitive adhesive layer for a long time.

Therefore, even when the polarizing plate is adhered after a certain amount of time has passed after the adhesive has been applied, the anchor effect of the adhesive layer itself and the above-mentioned isocyanate groups and hydroxyl groups on the surface of the polarizing plate By the reaction, the polarizing plate is sufficiently adhered to the pressure-sensitive adhesive layer, and peeling between the pressure-sensitive adhesive layer and the polarizing plate after adhesion is unlikely to occur.

[0037]

EXAMPLES The present invention will be clarified below by giving Examples and Comparative Examples of the present invention.

1) A five-necked flask equipped with an acrylic polymer polymerization stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet was prepared, and the composition shown in Table 1 below (unit: parts by weight). ), The monomer component,
Ethyl acetate and dodecyl mercaptan as a chain transfer agent dissolved in 30 ml of ethyl acetate were added and mixed uniformly by stirring, and then dissolved in the system by purging with nitrogen gas for 30 minutes while heating. Oxygen was removed. Then, 0.03 while keeping the system at 70 ° C
30 parts by weight of azobisisobutyronitrile was added to ethyl acetate
What was dissolved in ml was added dropwise, and under nitrogen atmosphere, 1
By maintaining for 0 hours, acrylic polymers A to C were obtained.

In the following Table 1, 2EHA is 2-ethylhexyl acrylate, 2-HPMA is 2-hydroxypropyl methacrylate, 2-HBMA is 2-hydroxybutyl methacrylate, AAc is acrylic acid, DD.
M is dodecyl mercaptan, and AIBN is azobisisobutyronitrile.

The molecular weights of the acrylic polymers A to C obtained as described above were measured by gel permeation chromatography. Table 1 also shows the weight average molecular weight and the weight average molecular weight (Mw) / number average molecular weight (Mn).

[0041]

[Table 1]

2) Preparation of acrylic pressure-sensitive adhesive composition Using any of the acrylic polymers A to C obtained as described above, diluted with ethyl acetate so that the resin content becomes 30% by weight, and further crosslinked. Tolylene diisocyanate adduct of trimethylolpropane as an agent (manufactured by Nippon Polyurethane Company, trade name: Coronate L) 1.0 part by weight or epoxy-based crosslinking agent (manufactured by Soken Chemical Co., Ltd., trade name: E-AX)
0.05 parts by weight was added dropwise, and the mixture was sufficiently stirred, and
And each acrylic adhesive composition of Comparative Examples 1 and 2 was obtained.
Table 2 shows combinations of the acrylic polymer and the crosslinking agent used. It should be noted that the ◯ mark in Table 2 means that a crosslinking agent marked with a ◯ mark was used.

[0043]

[Table 2]

3) Application of Adhesive to Phase Difference Plate A phase difference plate obtained by stretching polycarbonate was prepared and the surface was subjected to corona discharge treatment of 500 W.

The pressure-sensitive adhesive layer on the side of the retardation plate to be adhered to the polarizing plate is the above-mentioned Examples 1 to 4, Comparative Examples 1 and 2.
Either of these was used. In addition, regarding the pressure-sensitive adhesive layer on the other surface side of the retardation plate, that is, the side bonded to the glass plate of the liquid crystal display device, in any case, the pressure-sensitive adhesive composition of Comparative Example 2 was added to glycidoxypropyltrimethoxy. What added 0.5 weight part of silanes was prepared.

In applying the pressure-sensitive adhesive, the pressure-sensitive adhesive on the side to be bonded to the glass plate of the liquid crystal display device is 3
Apply 8 μm thick silicone separator (Lintec Co., Ltd., trade name: 38PF) to the silicone treated surface so that the thickness after drying is 25 μm, and dry in a 100 ° C. oven for 5 minutes, and then on the retardation plate. Laminated.

By the same operation as above, the pressure-sensitive adhesive layer on the side to be adhered to the polarizing plate is also laminated on the retardation plate, and as shown in FIG. , 13 was formed to obtain a double-sided pressure-sensitive adhesive tape for retardation plate. In addition, 14 and 15 show a separator.

4) Polarizing Plate A polarizing plate having a three-layer structure in which a triacetyl cellulose protective layer was provided on both surfaces of a commonly used polyvinyl alcohol was prepared. In the prepared polarizing plate, the polyvinyl alcohol layer has a thickness of 20 μm, and the triacetyl cellulose protective layer has a thickness of 50 μm.

After applying the pressure-sensitive adhesive on the side of the retardation plate double-sided pressure-sensitive adhesive tape prepared in Evaluation Method 3) on the side to be laminated on the polarizing plate, 2 kg without heating the double-sided pressure-sensitive adhesive tape after a lapse of a certain time.
The above polarizing plate was laminated while applying a pressure of / cm ² to produce an elliptically polarizing plate. As the above-mentioned fixed time, as shown in Table 3, seven kinds of time, 1 day later, 2 days later ... 7 days later, were set. After the bonding, the adhesive was cured by heating in an oven at 40 ° C. for 3 days to cure the adhesive.

The elliptically polarizing plate thus cured is a glass cell (Asahi Glass Co., Ltd., trade name: ASAHI AS).
20 ° C in an autoclave under conditions of 50 ° C and 5 atm to remove entrapped air during bonding.
Pressurize for 10 minutes and then put in an oven at 90 ° C for 10
The foamed state and the peeled state after 0 hour was observed.
FIG. 3 shows a state in which an elliptically polarizing plate is attached to a glass cell. In addition, 16 shows a polarizing plate and 17 shows a glass cell.

In the same manner as above, the elliptically polarizing plate was attached to a glass cell and pressed by an autoclave,
It was placed in an oven at 60 ° C. and 90% relative humidity instead of 90 ° C., and the foaming state and peeling state after 100 hours were similarly observed. The results are shown in Table 3 below.

[0052]

[Table 3]

In Table 3, peeling a, peeling b, peeling c
Indicates the following contents, respectively. Peeling a: Peeling within 5 mm at the edge between the polarizing plate and the pressure-sensitive adhesive layer. Peeling b: Peeling within 10 mm of the edge between the polarizing plate and the pressure-sensitive adhesive layer. Peeling c: Peeling between the polarizing plate and the pressure-sensitive adhesive layer beyond the end portion of 10 mm. Moreover, the above-mentioned peeling occurs after 100 hours have passed in an oven at 90 ° C., and when placed in an oven at 60 ° C. and a relative humidity of 90%, Examples 1 to 4 and Comparative Example 1,
No abnormality was observed in any of the two.

As is clear from Table 3, in Comparative Examples 1 and 2, the acrylic polymer C did not contain a vinyl-based monomer having a secondary or tertiary hydroxyl group. Peeling occurred between the pressure-sensitive adhesive layer and the polarizing plate after the lapse of 2 days, and the peeled state increased with the passage of days.

On the other hand, in Examples 1 to 4, no peeling was observed even after 5 days had passed after the polarizing plate-side pressure-sensitive adhesive was applied, and peeling occurred even after 6 days and 7 days had passed. The degree was small.

Therefore, in the pressure-sensitive adhesive layers of Examples 1 to 4 constructed by crosslinking the acrylic polymers A and B with the above-mentioned cross-linking agent, the time until the lamination of the polarizing plates was significantly extended. Even in the case, it is found that peeling at the interface between the pressure-sensitive adhesive layer and the polarizing plate can be effectively prevented.

[0057]

As described above, in the elliptically polarizing plate according to the present invention, the pressure-sensitive adhesive layer on the side where the polarizing plate is laminated has an alkyl (meth) having an alkyl group having 2 to 12 carbon atoms.
Vinyl containing acrylate as a main component and substantially not containing vinyl monomer having primary hydroxyl group, 0.1 to 10% by weight of vinyl monomer having secondary or tertiary hydroxyl group, and carboxyl group It is composed of a pressure-sensitive adhesive composition obtained by crosslinking an acrylic polymer obtained by copolymerizing a monomer composition containing 0 to 5% by weight of the total amount of a system monomer with the polyisocyanate compound. Therefore, the copolymerization of the vinyl monomer having a secondary or tertiary hydroxyl group can slow the progress of gelation of the pressure-sensitive adhesive, and the isocyanate group of the polyisocyanate compound can remain unreacted for a long time. , Even if the time until the polarizing plate is attached is increased, the adhesiveness between the pressure-sensitive adhesive layer and the polarizing plate can be effectively enhanced, and the pressure-sensitive adhesive layer and the polarizing plate in the obtained elliptically polarizing plate are The peeling between them can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a conventional elliptically polarizing plate is attached to a glass surface of a liquid crystal display device.

FIG. 2 is a cross-sectional view showing double-sided pressure-sensitive adhesive retardation plates prepared in Examples 1 to 4 and Comparative Examples 1 and 2.

FIG. 3 is a cross-sectional view showing a state in which an elliptical polarizing plate is bonded to a glass cell after bonding the polarizing plates in Examples 1 to 4 and Comparatives 1 and 2, and is used for durability evaluation after bonding the polarizing plates. FIG.

[Explanation of symbols]

 11 ... Retardation plate 12 ... Adhesive layer 13 ... Adhesive layer 16 ... Polarizing plate

Claims (1)

[Claims] 1. An elliptically polarizing plate obtained by laminating a polarizing plate on a retardation plate via an adhesive layer provided on the retardation plate, wherein the adhesive layer contains an alkyl group having 2 to 12 carbon atoms. 0.1 to 10% by weight based on the total amount of the vinyl-based monomer having a secondary or tertiary hydroxyl group, which does not substantially include a vinyl-based monomer having a primary hydroxyl group and which has an alkyl (meth) acrylate as a main component. A pressure-sensitive adhesive composition containing an acrylic polymer obtained by copolymerizing a monomer composition containing 0 to 5% by weight of a vinyl-based monomer having a carboxyl group, and a polyisocyanate compound as a crosslinking agent. An elliptically polarizing plate characterized by the above.