JPH05107411A - Phase difference plate fixing structure - Google Patents

Abstract

PURPOSE:To obtain a phase difference plate fixing structure which incorporates an adhesive layer which hardly blisters and peels off even though it falls in a high temperature and high humidity condition, and in which the phase difference plate is firmly bonded. CONSTITUTION:In a phase difference plate fixing structure in which a phase difference plate is fixed to a translucent support member through the intermediary of an adhesive layer, the abovementioned adhesive layer is made of an acrylic group adhesive composition containing a radical copolymer which is obtained by radically copolymerizing, at least, 50 to 98wt.% of (metha) acrylic alkyl ester having an alkyl group carbon number of 1 to 12, 1 to 10wt.% of unsaturated carboxylate, and 0 to 30wt.% of a monomer which is other than the monomers of the above-mentioned substance and which may be polymerized with the latter, having the averaged molecular weight Mw of the radical copolymer which is greater than 500,000 while the ratio Mw/Mn between averaged molecular weight Mw and averaged molecular number Mn is less than 4.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate fixing structure in which a retardation plate is fixed to a translucent support such as glass via an adhesive layer, and particularly to a high temperature or high humidity environment. The present invention relates to a retardation plate fixing structure in which foaming or peeling of an adhesive layer is unlikely to occur below.

[0002]

2. Description of the Related Art In order to prevent coloration of a display in a birefringent liquid crystal display device, there has been proposed a structure in which a retardation plate is arranged between a polarizing plate and a glass surface of a liquid crystal cell (see, for example, Japanese Patent Laid-Open Publication No. Hei 10 (1999) -135242). 2-247602). That is, by utilizing the birefringence of the retardation plate, an elliptically polarizing plate is constituted by the polarizing film and the retardation plate, thereby preventing the display coloration of the birefringent liquid crystal display device. Conventionally, the retardation plate has been attached to the cell surface, that is, the glass surface of a liquid crystal display device via an acrylic pressure-sensitive adhesive layer.

On the other hand, the retardation plate is made of a birefringent film, and is generally made of a polycarbonate-based resin as a main raw material. However, the polycarbonate-based resin is a non-adhesive material, and therefore the reliability of adhesion is high. There was a problem with. Further, when the above retardation plate is attached to a glass plate or the like using a general-purpose acrylic pressure-sensitive adhesive, a phenomenon such as peeling or foaming of the pressure-sensitive adhesive layer tends to occur under high temperature and high humidity.

[0004]

The object of the present invention is to maintain the state in which the retardation plate is reliably bonded to the translucent support such as glass even under high temperature and high humidity. Another object of the present invention is to provide a retardation plate fixing structure in which peeling or foaming of the pressure-sensitive adhesive layer is unlikely to occur.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, as a pressure-sensitive adhesive layer for bonding a retardation plate and a translucent support, a specific acrylic pressure-sensitive adhesive It was found that the above-mentioned problems can be achieved by using an agent composition, and the present invention has been completed. That is, the invention according to claims 1 and 2 is a retardation plate fixing structure in which a retardation plate is fixed to a translucent support through an adhesive layer, and the adhesive layer has the following specificity. It is characterized by comprising the acrylic pressure-sensitive adhesive composition. In the invention according to claim 1, the pressure-sensitive adhesive layer has at least 50 to 98% by weight of a (meth) acrylic acid alkyl ester whose alkyl group has 1 to 12 carbon atoms, 1 to 10% by weight of an unsaturated carboxylic acid, An acrylic pressure-sensitive adhesive composition containing a copolymer obtained by radically copolymerizing 1 to 10% by weight of an unsaturated acid anhydride and 0 to 30% by weight of another monomer copolymerizable with these monomers, The copolymer has a weight average molecular weight (Mw) of 500,000 or more, and a ratio of the weight average molecular weight to the number average molecular weight (Mn), that is, a dispersion ratio Mw / Mn is 4.0 or less. ..

Further, in the invention according to claim 2, the acrylic pressure-sensitive adhesive composition has at least 40 to 98% by weight of a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms, and unsaturated. 1 to 10% by weight of carboxylic acid,
An acrylic pressure-sensitive adhesive composition comprising a copolymer obtained by radically copolymerizing 1 to 20% by weight of N-vinylpyrrolidone and 0 to 30% by weight of another monomer copolymerizable with these monomers. Weight average molecular weight of polymer (Mw)
Is 500,000 or more, and the ratio of the weight average molecular weight to the number average molecular weight (Mn), that is, the dispersion ratio Mw / Mn is 4.0 or less. Hereinafter, the details of the retardation plate fixing structure according to the first and second aspects of the invention will be described.

In the retardation plate fixing structure according to claims 1 and 2, (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms is used as a main component of the acrylic pressure-sensitive adhesive composition. Be done. Examples of such an alkyl (meth) acrylate ester include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, octyl (meth) acrylate, Decyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and the like are preferably used.

Further, in the above acrylic pressure-sensitive adhesive composition,
The unsaturated carboxylic acid is radically copolymerized in the proportion of 1 to 10% by weight as described above. Examples of the unsaturated carboxylic acid that can be used include acrylic acid and methacrylic acid.
When the polymerization ratio of this unsaturated carboxylic acid is less than 1% by weight, sufficient adhesive strength and heat resistance cannot be obtained. On the other hand, when the polymerization ratio exceeds 10% by weight, the glass transition point Tg of the acrylic pressure-sensitive adhesive becomes high, the followability to the irregularities of the translucent support as an adherend becomes poor, and the translucent support is obtained. For example, when it is attached to glass, it becomes easy for air to be entrapped, which causes foaming. Therefore, the polymerization ratio of the unsaturated carboxylic acid needs to be in the range of 1 to 10% by weight as described above.

In the invention described in claim 1, the above (meta)
In addition to the acrylic acid alkyl ester and the unsaturated carboxylic acid, 1 to 1 of the unsaturated acid anhydride is added in order to enhance the adhesiveness.
Radical copolymerization is carried out in the range of 0% by weight. As the unsaturated acid anhydride, for example, maleic anhydride, itaconic anhydride, citraconic anhydride, etc. can be used. When the polymerization ratio of the unsaturated acid anhydride is less than 1% by weight, the effect of enhancing the adhesiveness to the retardation plate is not sufficient, while when it exceeds 10% by weight, the acrylic pressure-sensitive adhesive is similar to the case of unsaturated carboxylic acid. The glass transition point Tg of the composition becomes high, the followability to irregularities on the surface of the translucent support is lowered, and air is entrapped during sticking, which causes foaming. Therefore, the polymerization ratio of the unsaturated acid anhydride needs to be 1 to 10% by weight as described above.

On the other hand, in the invention described in claim 2, N-vinylpyrrolidone is contained in the amount of 1 to 2 in place of the unsaturated acid anhydride.
Radical-copolymerized at a rate of 0% by weight. N-vinylpyrrolidone is copolymerized to enhance the adhesiveness to the retardation plate, and the copolymerization ratio is 1% by weight.
If it is less than the above, the effect of enhancing the adhesiveness to the retardation plate is not sufficient, while if the copolymerization ratio exceeds 20% by weight, the glass transition point Tg of the acrylic pressure-sensitive adhesive composition is the same as in the case of unsaturated carboxylic acid. Becomes higher, the followability to irregularities on the surface of the translucent support is lowered, and air is entrapped during sticking, which causes foaming. Therefore, the copolymerization ratio of N-vinylpyrrolidone needs to be 1 to 20% by weight as described above.

In the acrylic pressure-sensitive adhesive composition used in the invention described in claims 1 and 2, the copolymer obtained by radical copolymerizing each of the monomers has a weight average molecular weight Mw of 500,000 or more. Yes, dispersion ratio Mw / Mn is 4.0
It must be: Weight average molecular weight Mw is 5
When it is less than 0,000 or when the dispersion ratio Mw / Mn exceeds 4.0, the heat resistance decreases. In addition, claim 1,
The other copolymerizable monomer in the invention described in 2 includes an ethylenically unsaturated group-containing monomer, and by copolymerizing the ethylenically unsaturated group-containing monomer, the cohesive force of the acrylic pressure-sensitive adhesive composition is increased. It can be further enhanced. Examples of the ethylenically unsaturated group-containing monomer that can be used include vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, and styrene. However, when the copolymerization ratio of the ethylenically unsaturated group-containing monomer becomes high, the tackiness is impaired,
The copolymerization ratio of the above ethylenically unsaturated group-containing monomer is 3
It is necessary to make it 0% by weight or less.

The method for producing the above radical copolymer used in the inventions described in claims 1 and 2 is not particularly limited, and any of the above monomers may be subjected to any method such as solution polymerization, bulk polymerization or emulsion polymerization. It can be obtained by polymerizing. As the polymerization initiator, a conventionally known polymerization initiator such as a peroxide such as benzoyl peroxide or an azo compound such as azobisisobutyronitrile can be appropriately used. Further, the polymerization may be initiated by irradiating light or radiation.

Further, in the inventions according to claims 1 and 2, a cross-linking agent is added to the obtained copolymer in order to increase cohesive force and heat resistance in each acrylic pressure-sensitive adhesive composition. Often, as such a cross-linking agent, polyisocyanate, epoxy resin, melamine resin, polyvalent metal salt, metal chelate or aziridine compound can be used. Further, in order to adjust the molecular weight, a suitable chain transfer agent such as lauryl mercaptan may be added during radical polymerization. Further, a plasticizer, a tackifier, a deterioration inhibitor and the like may be added to the acrylic pressure-sensitive adhesive composition as needed in order to obtain a wide range of pressure-sensitive adhesive properties.

In the invention described in claims 1 and 2, a pressure-sensitive adhesive layer is constituted by the above specific acrylic pressure-sensitive adhesive composition, and the retardation plate and the light-transmitting support are interposed via the pressure-sensitive adhesive layer. And are pasted together. The retardation plate that can be used is not particularly limited. However, when the retardation plate is made of a material that is made of a polycarbonate resin, which is a difficult-to-adhere material, the acrylic pressure-sensitive adhesive layer of the invention according to claims 1 and 2 exhibits excellent adhesion. Therefore, the invention described in claims 1 and 2 can be preferably used.

The material of the translucent support is not particularly limited, but glass or a resin such as polyethylene terephthalate or polyether sulfone is used. The translucent support may be a member forming a part of an optical device or an electronic device such as a glass plate exposed on the surface of the liquid crystal display device. That is, the retardation plate fixing structure according to the present invention may be configured by using a translucent support integrally incorporated in an optical device or an electronic device.

[0016]

In the retardation plate fixing structure according to the invention described in claim 1, the above-mentioned specific (meth) acrylic acid alkyl ester, unsaturated carboxylic acid, unsaturated acid anhydride and the like are radical-copolymerized in the above-mentioned specific ratio. Since the acrylic pressure-sensitive adhesive composition containing a copolymer that has been polymerized and has a weight average molecular weight of 500,000 or more and a dispersion ratio of 4.0 or less, the position of the pressure-sensitive adhesive layer is used. Adhesiveness to the phase difference plate is enhanced, and foaming and peeling of the pressure-sensitive adhesive layer are not likely to occur under high temperature and high humidity.

Similarly, also in the retardation plate fixing structure according to the invention described in claim 2, (meth) acrylic acid alkyl ester, unsaturated carboxylic acid, N-vinylpyrrolidone and the like are radicals at the above specific ratios. Copolymerized, weight average molecular weight of 500,000 or more, dispersion ratio of 4.0
Since the acrylic adhesive containing the following copolymer is used, the adhesiveness of the adhesive layer to the retardation plate is enhanced, and foaming or peeling of the adhesive layer under high temperature and high humidity occurs. hard.

[0018]

EXAMPLES The present invention will be clarified by giving Examples and Comparative Examples of the present invention. Examples 1 to 3 and Comparative Examples 1 and 2 Examples 1 to 3 and Comparative Examples 1 and 2 of the invention described in claim 1 will be described. (1) Preparation of acrylic copolymer solution In a flask equipped with a reflux condenser and a stirrer, a predetermined amount of n-butyl acrylate (BA) shown in Table 1 below,
Ethyl acrylate (EA), acrylic acid (AAc), maleic anhydride (AMAc) and ethyl acetate (EtAc)
Was charged and mixed uniformly. Then, while stirring in a nitrogen stream, azobisisobutyronitrile (AIB) as a polymerization initiator was added to 100 parts by weight of the monomer.
N) 0.01 part by weight was added and radical copolymerization was carried out at 70 ° C. for 10 hours to prepare respective acrylic copolymer solutions of Examples 1 to 3 and Comparative Examples 1 and 2.

[0019]

[Table 1]

(2) Preparation of Acrylic Pressure-Sensitive Adhesive Composition Each of the above acrylic copolymer solutions has a solid content of 25% by weight.
To 100 parts by weight of the solid content of the copolymer, the aziridine-based crosslinking agent (N, N
'-Hexamethylene-1,6-bis (1-aziridinecarboxamide)) was added in an amount of 0.15 part by weight, and the mixture was stirred.
Each acrylic pressure-sensitive adhesive composition of Examples 1 to 3 and Comparative Examples 1 and 2 was prepared.

(3) Preparation of Acrylic Pressure-Sensitive Adhesive Laminates Each of the acrylic pressure-sensitive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 and 2 prepared in (2) was surface-treated with silicon to a thickness of 38 μm. It was coated on a polyester film with an applicator so that the thickness of the dried adhesive layer was 25 μm, and dried in an oven for 4 minutes. Thereafter, a retardation plate having a thickness of 85 μm was attached to the polyester film with a laminator to prepare an acrylic pressure-sensitive adhesive laminate (a). A corona discharge-treated polyester film having a thickness of 38 μm was bonded to the polyester film with a laminator instead of the retardation plate to prepare an acrylic pressure-sensitive adhesive laminate (b).

(4) Measurement of physical properties Appearance test for foaming resistance and peeling resistance at high temperature; Examples 1 to 3 and Comparative Examples 1 and 2 prepared in (3)
After leaving each acrylic pressure-sensitive adhesive laminate (a) for 1 week at a temperature of 40 ° C. for 1 week, it is cut into a size of 75 × 150 mm, and the siliconized polyester film is peeled off, and then 100 × is applied to the adhesive surface. A 200 mm glass plate was attached with a laminator so as to prevent air bubbles from entering, to give a test piece.

The evaluation of foaming resistance was carried out by standing the above test piece on a glass stand, leaving it in a thermostat at 80 ° C. for 500 hours, and then observing the change in appearance due to foaming with the naked eye. Further, the peel resistance was evaluated by leaving the test piece in a constant temperature / humidity bath at 60 ° C. and a relative humidity of 90% for 500 hours, and then visually observing a change in appearance due to peeling. The evaluation of the change in appearance due to the foaming and peeling is shown in Table 4 described later according to the evaluation criteria based on Tables 2 and 3 below.

[0024]

[Table 2]

[0025]

[Table 3]

80 ° C. constant load test: After each acrylic pressure-sensitive adhesive laminate (b) of Examples 1 to 3 and Comparative Examples 1 and 2 prepared in (3) was left at 40 ° C. for one week,
Acrylic adhesive laminate after cutting into a size of 20 × 150 mm and peeling off the corona discharge treated polyester film, and then preventing bubbles from entering the glass plate with the retardation plate fixed by double-sided adhesive tape The pressure-sensitive adhesive surface of (b) and the retardation plate were adhered to each other, and a roller having a weight of 2 kg was reciprocated once to perform pressure bonding to obtain a test piece. The test piece above 80
After leaving it for 20 minutes or more in a constant temperature bath at ℃, the test piece was kept horizontal so that the acrylic pressure sensitive adhesive laminate (b) faced down, and 50 g at one end of the acrylic pressure sensitive adhesive laminate (b).
The suspension load was applied and the distance (peeling speed) of peeling per unit time was measured. The results are shown in Table 4 below.

[0027]

[Table 4]

The unit of 80 ° C. constant load peeling in Table 4 is mm / hour. As is clear from Table 4, in the foaming resistance test, in Examples 1 to 3, all 20
In the comparative examples 1 and 2, air bubbles of 20 to 40 μm were generated, while air bubbles of μm or more were not recognized. Further, in the peeling resistance test, peeling was not observed in Examples 1 to 3, while in Comparative Examples 1 and 2, 0.5
Peeling with a size of ˜1 mm was observed. Furthermore, 80 ℃
In the constant load peeling test, it is understood that the peeling rate of Examples 1 to 3 is considerably smaller than that of Comparative Examples 1 and 2, and thus the adhesiveness to the retardation plate at high temperature is high.

Examples 4 to 6 and Comparative Examples 3 and 4 Examples 4 to 6 and Comparative Examples 3 and 4 according to the invention of claim 2.
Will be described. (1) Preparation of acrylic copolymer In a flask equipped with a reflux condenser and a stirrer, a predetermined amount of n-butyl acrylate (BA) shown in Table 5 below,
Ethyl acrylate (EA), acrylic acid (AAc), N
-Vinylpyrrolidone (Vp) and ethyl acetate (EtA
c) was added and mixed uniformly. Then, while stirring the above monomer solution in a nitrogen stream, the amount of the above monomer 1
0.01 part by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator was added to 7 parts by weight of
Radical copolymerization was carried out at 0 ° C. for 10 hours to prepare respective acrylic copolymer solutions of Examples 4 to 6 and Comparative Examples 3 and 4.

[0030]

[Table 5]

(2) Preparation of Acrylic Pressure-Sensitive Adhesive Composition The acrylic copolymer solutions of Examples 4 to 6 and Comparative Examples 3 and 4 obtained as described above were used in Examples 1 to 3 and Comparative Examples. The same treatment as in the cases of 1 and 2 was performed to prepare each acrylic pressure-sensitive adhesive composition of Examples 4 to 6 and Comparative Examples 4 and 5. (3) Preparation of acrylic pressure-sensitive adhesive laminate The acrylic pressure -sensitive adhesive compositions of Examples 4 to 6 and Comparative Examples 3 and 4 prepared in (2) were used in Examples 1 to 3 and Comparative Examples 1 and 2, respectively. Acrylic adhesive laminates (a) and (b) were prepared in the same manner as in (3).

(4) Measurement of physical properties Appearance test for foaming resistance and peeling resistance under high humidity; Examples 4 to 6 and Comparative Examples 3 and 4 prepared in (3)
Using each of the acrylic pressure-sensitive adhesive laminates (a), the same as the appearance test for foaming resistance and peeling resistance performed in Examples 1 to 3 and Comparative Examples 1 and 4 (4), Changes in appearance due to foaming at high temperature and changes in appearance due to peeling were observed. The results are shown in Table 6 below according to the evaluation criteria shown in Tables 2 and 3.

80 ° C. constant load test; using the acrylic pressure-sensitive adhesive laminates (b) of Examples 4 to 6 and Comparative Examples 3 and 4 prepared in (3), Examples 1 to 3 and Comparative Examples 1 and 1 were used. Two
Adhesion at 80 ° C. to the retardation plate was evaluated in the same manner as in (4) 80 ° C. constant load test. The results are shown in Table 6 below.

[0034]

[Table 6]

As is clear from Table 6, in the foaming resistance test, no bubbles of 20 μm or more were observed in Examples 4 to 6, whereas in Comparative Examples 3 and 4, 20 to 40 μm were obtained. A small number and a large number of bubbles were observed.
In the peeling resistance test, peeling was not observed in Examples 4 to 6, while in Comparative Examples 3 and 4, 0.5 mm to
A peeling of 1 mm was observed. Further, as a result of the constant load peeling test at 80 ° C., in Examples 4 to 6, the peeling speeds are Comparative Examples 3 and 4.
It was quite small compared to. That is, in the acrylic pressure-sensitive adhesive laminates (b) of Examples 4 to 6, Comparative Examples 3 and 4 were used.
It can be seen that the adhesiveness to the retardation plate at a high temperature is much higher than that of the above.

[0036]

As described above, in the invention described in claim 1, the acrylic pressure-sensitive adhesive composition contains the (meth) acrylic acid alkyl ester, the unsaturated carboxylic acid, the unsaturated acid anhydride and the monomers thereof. The other copolymerizable monomer is radically copolymerized in the above-mentioned specific ratio, and the weight average molecular weight of the copolymer is 500,000 or more and the dispersion ratio is 4.0 or less. In the invention described in (1), (meth) acrylic acid alkyl ester, unsaturated carboxylic acid,
N-vinylpyrrolidone and other monomers copolymerizable with these monomers are copolymerized in the above specific range, and the copolymer has a weight average molecular weight of 500,000 or more and a dispersion ratio of 4.0 or less. Therefore, the adhesiveness between the retardation plate and the translucent support, the heat resistance and the moisture resistance of the adhered portion are enhanced, and the foaming and peeling of the pressure-sensitive adhesive layer at high temperature and high humidity are prevented. It is possible to provide a retardation plate fixing structure that is unlikely to occur.

Claims (2)

[Claims] 1. A retardation plate fixing structure in which a retardation plate is fixed to a translucent support through an adhesive layer, wherein the adhesive layer has at least carbon atoms of an alkyl group. 1
~ 12 (meth) acrylic acid alkyl ester 50 ~ 9
Radical copolymerization of 8% by weight, 1-10% by weight of unsaturated carboxylic acid, 1-10% by weight of unsaturated acid anhydride, and 0-30% by weight of another monomer copolymerizable with these monomers. And a weight average molecular weight (Mw) of the copolymer is 500,000 or more, and a ratio M of the weight average molecular weight to the number average molecular weight (Mn).
A retardation plate fixing structure, wherein w / Mn is 4.0 or less. 2. A retardation plate fixing structure in which a retardation plate is fixed to a translucent support via an adhesive layer, wherein the adhesive layer has at least carbon atoms of an alkyl group. 1
To (meth) acrylic acid alkyl ester 40 to 9
8% by weight, unsaturated carboxylic acid 1 to 10% by weight, N-
An acrylic pressure-sensitive adhesive composition comprising a copolymer obtained by radically copolymerizing 1 to 20% by weight of vinylpyrrolidone and 0 to 30% by weight of another monomer copolymerizable with these monomers. The weight average molecular weight (Mw) of the coalescence is 500,000 or more, and the ratio M between the weight average molecular weight and the number average molecular weight (Mn).
A retardation plate fixing structure, wherein w / Mn is 4.0 or less.