POLARIZING PLATE WITH TRANSPARENT ADHESIVE, AND TOUCH PANEL

Abstract

The present invention aims to provide a polarizing plate with a transparent adhesive which is incorporated in a touch panel used in a personal digital assistant or the like, which is less likely to cause adhesive deposits on a punching blade during a punching process, and which is also less likely to have bubbles formed on an adhering surface of the transparent adhesive to the polarizing plate even with exposure to high temperature and high humidity. The present invention also aims to provide a touch panel incorporating the polarizing plate with a transparent adhesive. The present invention relates to a polarizing plate with a transparent adhesive, including: a polarizing plate; and a transparent adhesive containing a plasticized polyvinyl acetal resin and adhering to the polarizing plate, the polarizing plate having a contact angle with water in conformity with JIS R-3257 of less than 50° on a surface to which the transparent adhesive adheres.

Claims

1. A polarizing plate with a transparent adhesive, comprising: a polarizing plate; and a transparent adhesive containing a plasticized polyvinyl acetal resin and adhering to the polarizing plate, the polarizing plate having a contact angle with water in conformity with JIS R-3257 of less than 50° on a surface to which the transparent adhesive adheres.

2. The polarizing plate with a transparent adhesive according to claim 1, wherein the surface to which the transparent adhesive adheres is preliminarily subjected to surface modification treatment.

3. The polarizing plate with a transparent adhesive according to claim 2, wherein the surface modification treatment is plasma treatment or corona treatment.

4. The polarizing plate with a transparent adhesive according to claim 1, wherein the plasticized polyvinyl acetal resin contains a polyvinyl acetal and a plasticizer, and the polyvinyl acetal is polyvinyl butyral.

5. A touch panel comprising: at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with touch panel wiring, and a resin film with touch panel wiring; and the polarizing plate with a transparent adhesive according to claim 1, the adherend and the polarizing plate being stacked on each other through the transparent adhesive.

6. The polarizing plate with a transparent adhesive according to claim 2, wherein the plasticized polyvinyl acetal resin contains a polyvinyl acetal and a plasticizer, and the polyvinyl acetal is polyvinyl butyral.

7. The polarizing plate with a transparent adhesive according to claim 3, wherein the plasticized polyvinyl acetal resin contains a polyvinyl acetal and a plasticizer, and the polyvinyl acetal is polyvinyl butyral.

8. A touch panel comprising: at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with touch panel wiring, and a resin film with touch panel wiring; and the polarizing plate with a transparent adhesive according to claim 2, the adherend and the polarizing plate being stacked on each other through the transparent adhesive.

9. A touch panel comprising: at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with touch panel wiring, and a resin film with touch panel wiring; and the polarizing plate with a transparent adhesive according to claim 3, the adherend and the polarizing plate being stacked on each other through the transparent adhesive.

10. A touch panel comprising: at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with touch panel wiring, and a resin film with touch panel wiring; and the polarizing plate with a transparent adhesive according to claim 4, the adherend and the polarizing plate being stacked on each other through the transparent adhesive.

11. A touch panel comprising: at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with touch panel wiring, and a resin film with touch panel wiring; and the polarizing plate with a transparent adhesive according to claim 6, the adherend and the polarizing plate being stacked on each other through the transparent adhesive.

12. A touch panel comprising: at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with touch panel wiring, and a resin film with touch panel wiring; and the polarizing plate with a transparent adhesive according to claim 7, the adherend and the polarizing plate being stacked on each other through the transparent adhesive.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0077] FIG. 1 is a cross-sectional view schematically illustrating an exemplary polarizing plate with a transparent adhesive of the present invention.

[0078] FIG. 2 is a cross-sectional view schematically illustrating an exemplary touch panel of the present invention.

DESCRIPTION OF EMBODIMENTS

[0079] The present invention is specifically described in the following with reference to, but not limited to, examples.

(Production of Polyvinyl Butyral Resin (1))

[0080] To a reactor equipped with a stirrer were charged 2700 mL of ion exchange water and 300 g of a polyvinyl alcohol having an average degree of polymerization of 1800 and a degree of saponification of 99.3 mol %. The mixture was stirred to be dissolved with heating, thereby preparing a solution. To the solution was added 35% by weight hydrochloric acid as a catalyst such that the hydrochloric acid concentration became 0.2% by weight. After adjustment of its temperature to 15° C., the mixture was blended with 21 g of n-butyraldehyde (n-BA) with stirring. Then, 145 g of n-butyraldehyde (n-BA) was further added, and a polyvinyl butyral resin in the form of white particles was precipitated. Fifteen minutes after the precipitation, 35% by weight hydrochloric acid was added such that the hydrochloric acid concentration became 1.8% by weight. The mixture was heated to 50° C. and matured at 50° C. for two hours. The solution was then cooled and neutralized. The polyvinyl butyral resin was washed with water and dried to give a polyvinyl butyral resin (1). The polyvinyl butyral resin (1) had a hydroxy group content of 31.0 mol %, an acetyl group content of 0.7 mol %, and a degree of butyralization (Bu degree) of 68.3 mol %.

(Production of Polyvinyl Butyral Resins (2) and (3))

[0081] Polyvinyl butyral resins (2) and (3) were produced in accordance with the formulations and conditions specified in Table 1 in the same manner as in the case of the polyvinyl butyral resin (1).

EXAMPLES 1 TO 25, COMPARATIVE EXAMPLES 1 TO 8

(1) Production of Transparent Adhesive

[0082] The following film formation was performed using the obtained polyvinyl butyral resins (1) to (3) in accordance with the composition of plasticized polyvinyl acetal resins specified in Table 2.

[0083] An amount of 100 parts by weight of the obtained polyvinyl butyral resin (having a degree of butyralization (Bu degree), a hydroxy group content, and an acetyl group content shown in Table 1) was blended with triethylene glycol-di-2-ethylhexanoate (3GO) as a plasticizer in an amount as shown in Table 2. The mixture was sufficiently kneaded to give a kneaded mass. The obtained kneaded mass was press-formed into a sheet shape using a press-molding machine, thereby preparing a transparent adhesive having a thickness as specified in Table 2.

(2) Surface Modification Treatment of Polarizing Plate

[0084] A polarizing plate (“SEG1425DU” from Nitto Denko Corporation) was subjected to surface modification treatment by a treatment method and at a treatment rate each specified in Table 2.

[0085] Plasma treatment was performed using an atmospheric pressure plasma treatment device (AP-T01) available from Sekisui Chemical Co., Ltd. under the condition of an oxygen concentration of 1000 ppm. Corona treatment was performed using a high frequency power source of AGI020 available from Kasuga Electric Works Ltd. and a ceramic electrode (17 mmφ>410 mm in length).

[0086] Five minutes after the plasma treatment or corona treatment, the contact angle with water on the treated surface of the polarizing plate was measured in conformity with JIS R-3257 using a contact angle measuring device (“CAM200” available from KSV Instruments Ltd.). Table 2 shows the measured contact angle.

(3) Production of Laminate

[0087] The adherend used was a glass plate, an ITO-PET film, or a glass plate with touch panel wiring (OGS in Table 2). The glass plate with touch panel wiring (OGS in Table 2) was subjected to surface modification treatment and measurement of the contact angle in the same manner as in

(2) Surface Modification Treatment of Polarizing Plate.

[0088] A transparent adhesive punched using a Thomson blade (50 mm×50 mm) was sandwiched between a polarizing plate (50 mm×50 mm) and an adherend (50 mm×50 mm). Next, they were placed with the adherend facing down, and the upper surface of the polarizing plate was pressed with a SN-rubber roller (size 1, 100 mm in width) so that the adherend and the polarizing plate were bonded to each other. The resulting subject was then heated in an autoclave at 70° C. and 0.5 MPa for 30 minutes, thereby preparing a laminate including the adherend (a glass plate, an ITO-PET film, or a glass plate with touch panel wiring (OGS in Table 2)), the transparent adhesive (PVB in Table 2), and the polarizing plate stacked in the stated order. At this time, the absence of bubbles on the adhering surface of the transparent adhesive to the polarizing plate was confirmed. In the case of the glass plate with touch panel wiring (OGS in Table 2), the absence of bubbles on the adhering surface of the transparent adhesive to the OGS was confirmed. The series of operations from the surface modification treatment of the polarizing plate to the production of the laminate was carried out within one hour.

[0089] After confirmation of the absence of bubbles on the adhering surface of the transparent adhesive to the polarizing plate, a glass plate was bonded to the rear surface of the polarizing plate with a transparent acrylic adhesive, thereby producing a laminate having a structure shown in Table 2.

COMPARATIVE EXAMPLES 9 to 26

(1) Production of Acrylic Copolymer Resin (4)

[0090] In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet, 65.0 parts by weight of n-butyl acrylate, 26.0 parts by weight of methyl methacrylate, 4.0 parts by weight of ethyl acrylate, 1.0 parts by weight of hydroxyethyl acrylate, 4.0 parts by weight of acrylic acid, and 0.2 parts by weight of 2,2’-azobisisobutyronitrile as a polymerization initiator were dissolved in 100 parts by weight of ethyl acetate. After nitrogen substitution, polymerization was performed at 80° C. for eight hours to provide an acrylic copolymer resin (4).

[0091] The obtained acrylic copolymer resin (4) was diluted 50-fold with tetrahydrofuran (THF), and the obtained diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore size: 0.2 μm), thereby preparing a measurement sample. The measurement sample was fed to a gel permeation chromatograph (2690 Separations Model from Waters Corporation), and GPC measurement was performed under the conditions of a sample flow rate of 1 ml/min and a column temperature of 40° C. to determine the polystyrene equivalent molecular weight of the acrylic copolymer resin (4). Based on the obtained value, the weight average molecular weight (Mw) of the acrylic copolymer resin (4) was determined. The acrylic copolymer resin (4) had a weight average molecular weight of 650,000.

[0092] The column used was GPC LF-804 (Showa Denko K.K.) and a detector used was a differential refractometer.

(2) Production of Transparent Adhesive

[0093] An amount of 100 parts by weight of the obtained acrylic copolymer resin was diluted with ethyl acetate to give an adhesive solution with a resin solids content of 45%. An amount of 100 parts by weight of the adhesive solution was blended with 1 part by weight of an isocyanate crosslinking agent (CORONATE L-45 from Nippon Polyurethane Industry Co., Ltd., solids content of 45%), and the mixture was stirred for 15 minutes. The resulting mixture was applied to a release-treated surface of a release PET film having a thickness of 50 μm in such a manner that the dried adhesive had a thickness of 200 μm, and the adhesive mixture was dried at 80° C. for 15 minutes. On the obtained adhesive layer, another release PET film was stacked in such a manner that the release-treated surface was in contact with the adhesive layer, thereby preparing a laminate. The resulting sheet was allowed to stand at 23° C. for five days to provide a transparent adhesive (thickness of 200 μm) with the release PET films attached to both surfaces.

(3) Surface Modification Treatment of Polarizing Plate

[0094] The polarizing plate was subjected to surface modification treatment in the same manner as in Example 1 by a treatment method and at a treatment rate each specified in Table 4.

(4) Production of Laminate

[0095] A laminate including an adherent (a glass plate or an ITO-PET film), a transparent adhesive (acrylic copolymer resin in Table 4), and a polarizing plate stacked in the stated order was produced in the same manner as in Example 1. At this time, the absence of bubbles on the adhering surface of the transparent adhesive to the polarizing plate was confirmed.

[0096] After confirmation of the absence of bubbles on the adhering surface of the transparent adhesive to the polarizing plate, a glass plate was bonded to the rear surface of the polarizing plate with a transparent acrylic adhesive, thereby preparing a laminate having a structure specified in Table 4.

<Evaluation>

[0097] The transparent adhesives and laminates obtained in the examples and comparative examples were evaluated for the following parameters. Tables 2 and 4 show the results.

(1) Formation of Bubbles

[0098] After the confirmation of the absence of bubbles on the adhering surface of the transparent adhesive to the polarizing plate, the laminate was left in an environment at 85° C. and 85%. Five hours later, the appearance of the laminate was visually checked. A state where visible bubbles with a size of 100 μmφ or larger were not present on the adhering surface of the transparent adhesive to the polarizing plate was rated “∘∘ (Excellent)”. A state where bubbles with a size of 500 μmφ or larger were not present was rated “∘ (Good)”. A state where bubbles with a size of 500 μmφ or larger were present was rated “× (Poor)”.

(2) Adhesive Deposits

[0099] The transparent adhesive was punched using a Thomson blade (50 mm×50 mm) 50 times, and whether or not the transparent adhesive adheres to the Thomson blade (adhesive deposits) was visually checked. A case where adhesive deposits were not found on the Thomson blade was rated “∘ (Good)”, and a case where adhesive deposits were found on the Thomson blade was rated “× (Poor)”.

TABLE-US-00001 TABLE 1 Resin Resin Resin (1) (2) (3) Formula- Ion exchange water (mL) 2700 2700 2700 tion and Average degree of polymer- 1800 1700 3200 condition ization Degree of saponification 99.3 99.2 88.0 (mol %) Weight of polyvinyl alcohol 300 300 300 (g) Concentration of catalyst, 0.2 0.2 0.6 35% by weight hydrochloric acid, after dilution with water (% by weight) Temperature (° C.) 15 15 15 n-BA first addition (g) 21 15 14.2 n-BA second addition (g) 145 130 186 Concentration of 35% by 1.8 1.8 3.9 weight hydrochloric acid, after dilution with water (% by weight) Heating temperature (matur- 50 60 45 ing) (° C.) Heating time (maturing) (hr) 2 2 3 Composi- Bu degree (mol %) 68.3 64.7 64.0 tion Acetyl group content (mol %) 0.7 0.8 12.0 Hydroxy group content (mol %) 31.0 34.5 24.0

TABLE-US-00002 TABLE 2 Polarizing plate OGS Surface Surface Transparent adhesive modification modification Polyvinyl treatment treatment Evaluation butyral Plasticizer Film Treatment Treatment 85° C.85% 5 h Type of Parts by thickness Treatment rate Contact angle Treatment rate Contact angle Formation of Adhesive resin Type weight (μm) method (m/min) (°) method (m/min) (°) Structure bubbles deposits Example 1 Resin (1) 3GO 35 200 Plasma 0.1 6 — — — Glass/PVB/polarizing plate/glass ⊚ ◯ Example 2 Resin (1) 3GO 35 200 Plasma 0.1 6 — — — ITO-PET/PVB/polarizing plate/glass ⊚ ◯ Example 3 Resin (2) 3GO 35 200 Plasma 0.1 6 — — — Glass/PVB/polarizing plate/glass ⊚ ◯ Example 4 Resin (2) 3GO 35 200 Plasma 0.1 6 — — — ITO-PET/PVB/polarizing plate/glass ⊚ ◯ Example 5 Resin (3) 3GO 35 200 Plasma 0.1 6 — — — Glass/PVB/polarizing plate/glass ⊚ ◯ Example 6 Resin (3) 3GO 35 200 Plasma 0.1 6 — — — ITO-PET/PVB/polarizing plate/glass ⊚ ◯ Example 7 Resin (1) 3GO 35 200 Plasma 0.15 13 — — — Glass/PVB/polarizing plate/glass ⊚ ◯ Example 8 Resin (1) 3GO 35 200 Plasma 0.15 13 — — — ITO-PET/PVB/polarizing plate/glass ⊚ ◯ Example 9 Resin (2) 3GO 35 200 Plasma 0.15 13 — — — Glass/PVB/polarizing plate/glass ⊚ ◯ Example 10 Resin (2) 3GO 35 200 Plasma 0.15 13 — — — ITO-PET/PVB/polarizing plate/glass ⊚ ◯ Example 11 Resin (3) 3GO 35 200 Plasma 0.15 13 — — — Glass/PVB/polarizing plate/glass ⊚ ◯ Example 12 Resin (3) 3GO 35 200 Plasma 0.15 13 — — — ITO-PET/PVB/polarizing plate/glass ⊚ ◯ Example 13 Resin (1) 3GO 35 200 Corona 0.3 21 — — — Glass/PVB/polarizing plate/glass ◯ ◯ Example 14 Resin (1) 3GO 35 200 Corona 0.3 21 — — — ITO-PET/PVB/polarizing plate/glass ◯ ◯ Example 15 Resin (1) 3GO 35 200 Plasma 0.25 25 — — — Glass/PVB/polarizing plate/glass ◯ ◯ Example 16 Resin (1) 3GO 35 200 Plasma 0.25 25 — — — ITO-PET/PVB/polarizing plate/glass ◯ ◯ Example 17 Resin (1) 3GO 35 200 Plasma 1 35 — — — Glass/PVB/polarizing plate/glass ◯ ◯ Example 18 Resin (1) 3GO 35 200 Plasma 1 35 — — — ITO-PET/PVB/polarizing plate/glass ◯ ◯ Example 19 Resin (1) 3GO 35 200 Plasma 1.5 42 — — — Glass/PVB/polarizing plate/glass ◯ ◯ Example 20 Resin (1) 3GO 35 200 Plasma 1.5 42 — — — ITO-PET/PVB/polarizing plate/glass ◯ ◯ Example 21 Resin (1) 3GO 35 200 Plasma 0.15 13 Plasma 0.5 7 OGS/PVB/polarizing plate/glass ◯ ◯ Example 22 Resin (1) 3GO 35 200 Plasma 0.15 13 Plasma 1.5 15 OGS/PVB/polarizing plate/glass ◯ ◯ Example 23 Resin (1) 3GO 35 200 Plasma 0.15 13 Plasma 2.0 28 OGS/PVB/polarizing plate/glass ◯ ◯ Example 24 Resin (1) 3GO 35 200 Plasma 1.7 48 — — — Glass/PVB/polarizing plate/glass ◯ ◯ Example 25 Resin (1) 3GO 35 200 Plasma 1.7 48 — — — ITO-PET/PVB/polarizing plate/glass ◯ ◯ Comparative Resin (1) 3GO 35 200 Plasma 2 58 — — — Glass/PVB/polarizing plate/glass X ◯ Example 1 Comparative Resin (1) 3GO 35 200 Plasma 2 58 — — — ITO-PET/PVB/polarizing plate/glass X ◯ Example 2 Comparative Resin (1) 3GO 35 200 Plasma 4 67 — — — Glass/PVB/polarizing plate/glass X ◯ Example 3 Comparative Resin (1) 3GO 35 200 Plasma 4 67 — — — ITO-PET/PVB/polarizing plate/glass X ◯ Example 4 Comparative Resin (1) 3GO 35 200 Corona 3.5 77 — — — Glass/PVB/polarizing plate/glass X ◯ Example 5 Comparative Resin (1) 3GO 35 200 Corona 3.5 77 — — — ITO-PET/PVB/polarizing plate/glass X ◯ Example 6 Comparative Resin (1) 3GO 35 200 Not — 95 — — — Glass/PVB/polarizing plate/glass X ◯ Example 7 performed Comparative Resin (1) 3GO 35 200 Not — 95 — — — ITO-PET/PVB/polarizing plate/glass X ◯ Example 8 performed

TABLE-US-00003 TABLE 3 Resin (4) Composition Monomer n-Butyl acrylate 65.0 of acrylic composition Methyl methacrylate 26.0 copolymer (% by Ethyl acrylate 4.0 resin weight) Hydroxyethyl acrylate 1.0 Acrylic acid 4.0 Weight average molecular weight (Mw/10,000) 65.0 Isocyanate CORONATE L-45 from Nippon 1.0 crosslinking Polyurethane Industry Co., Ltd. agent Solids content of 45%

TABLE-US-00004 TABLE 4 Polarizing plate Transparent adhesive Surface Acrylic modification Evaluation copolymer treatment 85° C. resin Film Treatment Contact 85% 5 h Type of thickness Treatment rate angle Formation Adhesive resin (μm) method (m/min) (°) Structure of bubbles deposits Comparative Resin (4) 200 Plasma 0.15 13 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 9 Comparative Resin (4) 200 Plasma 0.15 13 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 10 Comparative Resin (4) 200 Corona 0.3 21 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 11 Comparative Resin (4) 200 Corona 0.3 21 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 12 Comparative Resin (4) 200 Plasma 0.25 25 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 13 Comparative Resin (4) 200 Plasma 0.25 25 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 14 Comparative Resin (4) 200 Plasma 1 35 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 15 Comparative Resin (4) 200 Plasma 1 35 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 16 Comparative Resin (4) 200 Plasma 1.5 42 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 17 Comparative Resin (4) 200 Plasma 1.5 42 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 18 Comparative Resin (4) 200 Plasma 2 58 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 19 Comparative Resin (4) 200 Plasma 2 68 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 20 Comparative Resin (4) 200 Plasma 4 67 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 21 Comparative Resin (4) 200 Plasma 4 67 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 22 Comparative Resin (4) 200 Corona 3.5 77 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 23 Comparative Resin (4) 200 Corona 3.5 77 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 24 Comparative Resin (4) 200 Not — 95 Glass/acrylic copolymer resin/polarizing plate/glass X X Example 25 performed Comparative Resin (4) 200 Not — 95 ITO-PET/acrylic copolymer resin/polarizing plate/glass X X Example 26 performed

INDUSTRIAL APPLICABILITY

[0100] The present invention can provide a polarizing plate with a transparent adhesive which is incorporated in a touch panel used in a personal digital assistant or the like, which is less likely to cause adhesive deposits on a punching blade during a punching process, and which is also less likely to have bubbles formed on an adhering surface of the transparent adhesive to the polarizing plate even with exposure to high temperature and high humidity. The present invention also can provide a touch panel incorporating the polarizing plate with a transparent adhesive.

REFERENCE SIGNS LIST

[0101] 1: Transparent adhesive [0102] 2: Polarizing plate [0103] 2a: Polyvinyl alcohol layer [0104] 2b: Protection film [0105] 2c: Hard coat layer [0106] 2x: Surface to which transparent adhesive adheres of polarizing plate [0107] 3: Polarizing plate with transparent adhesive [0108] 4: Glass plate with touch panel wiring [0109] 4a: Glass plate [0110] 4b: Touch panel wiring [0111] 4c: Hard coat layer [0112] 5: Liquid crystal display module