INTERLAYER FILLER MATERIAL FOR TOUCH PANELS, AND LAMINATE

Abstract

An interlayer filling material for a touch panel which is used for filling an interlayer space between a touch panel and another component or an interlayer space between transparent conductive films included in the touch panel in production of a personal digital assistant, which is excellent in followability to steps of a decorative printing portion or wiring upon filling of an interlayer space (lamination) and also excellent in defoaming properties to release air bubbles entrapped during filling of an interlayer space (lamination) or air bubbles left near the steps, which is less likely to be whitened and less likely to deteriorate an ITO film even under a high-temperature and high-humidity environment. The present invention also aims to provide a laminate produced using the interlayer filling material for a touch panel. The interlayer filling material includes: a polyvinyl acetal; a plasticizer; and an organic acid.

Claims

1-5. (canceled)

6. A method of producing a laminate comprising, a touch panel; and an interlayer filling material for the touch panel comprising a polyvinyl butyral, a plasticizer, and an organic acid, the method comprising: 1) filling at least one interlayer space selected from the group consisting of an interlayer space between a surface protection panel and the touch panel, an interlayer space between the touch panel and a polarizing film, and an interlayer space between transparent conductive films included in the touch panel with the interlayer filling material to produce a stack, 2) performing preliminary heat-bonding of the stack at about 70° C., 3) followed by an autoclave treatment of the stack at 70° C. to 85° C. and 0.5 MPa or more for 30 minutes, 4) then decompressing the stack after cooling to 30° C. or lower to produce the laminate, wherein: the plasticizer is at least one selected from the group consisting of triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-pivalate, and di-(2-butoxyethyl)adipate, the organic acid is at least one selected from the group consisting of 2-ethylhexanoic acid, adipic acid, and phthalic acid, an amount of the plasticizer in the interlayer filling material for the touch panel is 5 to 45 parts by weight relative to 100 parts by weight of the polyvinyl butyral, an amount of the organic acid in the interlayer filling material for the touch panel is 0.01 to 5 parts by weight relative to 100 parts by weight of the polyvinyl butyral, and the polyvinyl butyral contains 16 to 45 mol % hydroxy groups, a degree of acetylation of 0.1 to 30 mol %, and a degree of butyralization of 50 to 85 mol %.

7. The method of producing a laminate according to claim 6, wherein the total amount of the polyvinyl butyral and the plasticizer is 50% by weight or more of the interlayer filling material.

8. The method of producing a laminate according to claim 6, comprising filling the interlayer filling material in at least one interlayer space selected from the group consisting of the interlayer space between the surface protection panel and the touch panel, and the interlayer space between the touch panel and the polarizing film to produce the stack.

9. The method of producing a laminate according to claim 7, comprising filling the interlayer filling material in at least one interlayer space selected from the group consisting of the interlayer space between the surface protection panel and the touch panel, and the interlayer space between the touch panel and the polarizing film to produce the stack.

10. The method of producing a laminate according to claim 6, wherein the interlayer filling material for the touch panel is in a sheet form having a thickness of 5 μm to 800 μm.

11. The method of producing a laminate according to claim 7, wherein the interlayer filling material for the touch panel is in a sheet form having a thickness of 5 μm to 800 μm.

12. The method of producing a laminate according to claim 6, wherein 3) the autoclave treatment is performed at 70° C. and 0.5 MPa for 30 minutes.

13. The method of producing a laminate according to claim 7, wherein 3) the autoclave treatment is performed at 70° C. and 0.5 MPa for 30 minutes.

14. The method of producing a laminate according to claim 6, wherein the method consists of the steps 1) to 4).

15. The method of producing a laminate according to claim 7, wherein the method consists of the steps 1) to 4).

16. The method of producing a laminate according to claim 10, wherein the thickness of the interlayer filling material for the touch panel in the sheet form is 300 μm to 400 μm.

17. The method of producing a laminate according to claim 11, wherein the thickness of the interlayer filling material for the touch panel in the sheet form is 300 μm to 400 μm.

18. The method of producing a laminate according to claim 6, wherein the interlayer filling material contacts an ITO film.

19. The method of producing a laminate according to claim 7, wherein the interlayer filling material contacts an ITO film.

20. The method of producing a laminate according to claim 18, wherein 3) the autoclave treatment is performed at 70° C. and 0.5 MPa for 30 minutes.

21. The method of producing a laminate according to claim 19, wherein 3) the autoclave treatment is performed at 70° C. and 0.5 MPa for 30 minutes.

22. The method of producing a laminate according to claim 18, wherein the method consists of the steps 1) to 4).

23. The method of producing a laminate according to claim 19, wherein the method consists of the steps 1) to 4).

24. The method of producing a laminate according to claim 18, wherein the interlayer filling material for the touch panel is in a sheet form having a thickness of 300 μm to 400 μm.

25. The method of producing a laminate according to claim 19, wherein the interlayer filling material for the touch panel is in a sheet form having a thickness of 300 μm to 400 μm.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0050] FIG. 1 is a cross-sectional view schematically illustrating an exemplary application of the interlayer filling material for a touch panel of the present invention.

[0051] FIG. 2 is a schematic view for explaining a method of testing the interlayer filling material for a touch panel obtained in each of the examples and comparative examples to evaluate the properties of suppressing deterioration of an ITO film (ITO deterioration properties) under a high-temperature and high-humidity environment.

DESCRIPTION OF EMBODIMENTS

[0052] Embodiments of the present invention will be specifically described in the following with reference to, but not limited to, the examples.

Examples 1 to 24, Comparative Examples 1 to 30

(1) Preparation of Polyvinyl Butyral

[0053] A reactor equipped with a stirrer was charged with 2,700 mL of ion exchange water and 300 g of polyvinyl alcohol having an average degree of polymerization of 3,200 and a degree of saponification of 88.0 mol %, and the contents were heated with stirring to be dissolved, thereby preparing a solution. To the obtained solution was added as a catalyst 35% by weight hydrochloric acid such that the hydrochloric acid concentration was set to 0.6% by weight. The temperature of the mixture was adjusted to 15° C., and 14.2 g of n-butyraldehyde (n-BA) was added thereto with stirring. Then, 186 g of n-butyraldehyde (n-BA) was further added, so that polyvinyl butyral 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 was set to 3.9% by weight. The mixture was heated to 45° C. and aged at 45° C. for three hours. After cooling and neutralization of the solution, the polyvinyl butyral was washed with water and then dried, thereby preparing polyvinyl butyral. The obtained polyvinyl butyral had a hydroxy group content of 24.0 mol %, an acetyl group content of 12.0 mol %, and a degree of butyralization (Bu degree) of 64.0 mol %.

(2) Production of Interlayer Filling Material for a Touch Panel

[0054] To 100 parts by weight of the obtained polyvinyl butyral were added a plasticizer and an organic acid each of the type and in an amount as specified in Table 1 or 2, and sufficiently mixed to give a mixture. The obtained mixture was press-molded using a press-molding machine into a sheet, thereby preparing an interlayer filling material for a touch panel with a thickness of 200 μm.

[0055] In the tables, “3G1” refers to triethylene glycol-di-acetate and “3GE” refers to triethylene glycol-di-propanoate.

<Evaluation>

[0056] The interlayer filling materials for a touch panel obtained in the examples and comparative examples were evaluated by the following methods.

[0057] Tables 1 and 2 show the results.

(1) Evaluation of Defoaming Properties

[0058] To a white glass sheet (76 mm×52 mm, thickness of 1.0 to 1.2 mm, S9112 available from Matsunami Glass Ind., Ltd.) was attached the interlayer filling material for a touch panel cut to the same size as the white glass sheet. To the other face of the interlayer filling material for a touch panel was attached an ITO-PET film (ITO-coated polyethylene terephthalate (PET) film) cut to the same size as the white glass sheet, thereby preparing a glass/interlayer filling material for a touch panel/ITO-PET film structure. At this time, air bubbles were intendedly included at the interface between the glass sheet and the interlayer filling material for a touch panel.

[0059] The structure was preliminarily heat-bonded in a vacuum laminator at 70° C. and 1 atm for 30 minutes, heated in an autoclave at 70° C. and 0.5 MPa for 30 minutes, and decompressed after cooling to 30° C. or lower. A laminate in which the interlayer space between the glass sheet and the ITO-PET film was filled with the interlayer filling material for a touch panel was thus prepared.

[0060] The obtained laminate was observed with a digital microscope (Keyence Corporation). The case where no residual air bubbles were observed was rated “0 (Good)”. The case where residual air bubbles were observed was rated “x (Poor)”.

(2) Evaluation of Followability to Steps

[0061] To a white glass sheet (76 mm×52 mm, thickness of 1.0 to 1.2 mm, 59112 available from Matsunami Glass Ind., Ltd.) was attached a frame-shaped one-sided adhesive (thickness of 100 μm) in the hollow square shape (outer frame: 76 mm×52 mm, inner frame: 56 mm×32 mm), thereby forming a step.

[0062] To the surface of the white glass sheet where the frame-shaped step in the hollow square shape was formed was applied the interlayer filling material for a touch panel cut to a size of 76 mm×52 mm. To the interlayer filling material for a touch panel was further attached an ITO-coated polyethylene terephthalate film (ITO-PET available from Sekisui Nano Coat Technology) cut to a size of 76 mm×52 mm. Upon each lamination, entrapment of air bubbles was avoided as far as possible.

[0063] The structure was preliminarily heat-bonded using a vacuum laminator at 70° C. and 1 atm for 30 minutes, heated in an autoclave at 70° C. and 0.5 MPa for 30 minutes, and decompressed after cooling to 30° C. or lower. A laminate in which the interlayer space between the glass sheet and the ITO-PET film was filled with the interlayer filling material for a touch panel was thus prepared.

[0064] The obtained laminate was observed with a digital microscope (available from Keyence Corporation). The case where no air bubbles were observed at the step was rated “o (Good)”. The case where air bubbles were observed at the step was rated “x (Poor)”.

(3) Evaluation of Properties of not Deteriorating ITO Film Under High-Temperature and High-Humidity Environment

[0065] FIG. 2 shows a schematic view for explaining a method of testing the interlayer filling material for a touch panel to evaluate the properties of suppressing deterioration of an ITO film (ITO deterioration properties) under a high-temperature and high-humidity environment.

[0066] As illustrated in FIG. 2, to a conductive film 6 (25 mm in width, 120 mm in length) with an ITO film formed on its surface was applied silver paste at both ends in the lengthwise direction each in a width of 15 mm. The applied silver paste was heated to be dried, thereby forming silver layers (silver electrodes) 7. The conductive film 6 with the silver layers 7 formed thereon was attached to a glass sheet 8. Then, an interlayer filling material for a touch panel (width of 30 mm, length of 100 mm) 9 was attached to contact the both silver layers 7, the obtained product was treated in an autoclave at 70° C. and 0.5 MPa for 30 minutes, thereby preparing an evaluation sample.

[0067] The evaluation sample includes, as illustrated in FIG. 2, the conductive film 6, the silver layers 7, the glass sheet 8, and the interlayer filling material for a touch panel 9.

[0068] The resistance value between the silver layers 7 of the evaluation sample was measured with a tester 10, and the obtained value was defined as the “ITO resistance value (initial)”. Then, the evaluation sample was left in an environment at a temperature of 85° C. and a humidity of 85% for a high-temperature and high-humidity treatment for 250 hours. After the treatment, the resistance value between the silver layers 7 of the evaluation sample was measured with the tester 10, and the obtained value was defined as the “ITO resistance value (after high-temperature and high-humidity treatment)”.

[0069] The value of “ITO resistance value (after high-temperature and high-humidity treatment)/“ITO resistance value (initial)” was calculated. The case where the calculated value was 10 or less was rated “o (Good)”. The case where the calculated value was more than 10 and 15 or less was rated “Δ (Average)”. The case where the calculated value was more than 15 was rated “x (Poor)”.

(4) Evaluation of Whitening Resistance Under a High-Temperature and High-Humidity Environment

[0070] To a white glass sheet (76 mm×52 mm, thickness of 1.0 to 1.2 mm, 59112 available from Matsunami Glass Ind., Ltd.) was attached the interlayer filling material for a touch panel cut to the same size as the white glass sheet. To the other surface of the interlayer filling material for a touch panel was attached an ITO-PET film (ITO-coated polyethylene terephthalate (PET) film) cut to the same size as the white glass sheet, thereby preparing a glass/interlayer filling material for a touch panel/ITO-PET film structure. Upon each lamination, entrapment of air bubbles was avoided as far as possible.

[0071] The structure was preliminarily heat-bonded using a vacuum laminator at 70° C. and 1 atm for 30 minutes, heated in an autoclave at 70° C. and 0.5 MPa for 30 minutes, and decompressed after cooling to 30° C. or lower. A laminate in which the interlayer space between the glass sheet and the ITO-PET film was filled with the interlayer filling material for a touch panel was thus prepared.

[0072] The obtained laminate was left in an environment at a temperature of 85° C. and a humidity of 85% for a high-temperature and high-humidity treatment for 250 hours. The laminate was taken out after the treatment and allowed to stand still for 30 minutes. Then, the haze value thereof was measured with a haze meter (Haze meter TC-HIIIDPK available from Tokyo Denshoku Co., Ltd.). The case where the haze value was 1.0% or less was rated “0 (Good)”. The case where the haze value was more than 1.0% was rated “x (Poor)”.

TABLE-US-00001 TABLE 1 Interlayer filling material for a touch panel Evaluation Plasticizer Organic acid Properties Parts Parts of not by by Follow- deterio- weight weight Defoaming ability rating Whitening Resin Type (phr) Type (phr) properties to steps ITO film resistance Example 1 Polyvinyl butyral 3GO 30 2-Ethylhexanoic acid 0.01 ∘ ∘ ∘ ∘ Example 2 Polyvinyl butyral 3GO 30 2-Ethylhexanoic acid 0.05 ∘ ∘ ∘ ∘ Example 3 Polyvinyl butyral 3GO 30 2-Ethylhexanoic acid 0.1 ∘ ∘ ∘ ∘ Example 4 Polyvinyl butyral 3GO 30 2-Ethylhexanoic acid 1 ∘ ∘ ∘ ∘ Example 5 Polyvinyl butyral 3GO 30 Adipic acid 0.01 ∘ ∘ ∘ ∘ Example 6 Polyvinyl butyral 3GO 30 Adipic acid 0.05 ∘ ∘ ∘ ∘ Example 7 Polyvinyl butyral 3GO 30 Adipic acid 0.1 ∘ ∘ ∘ ∘ Example 8 Polyvinyl butyral 3GO 30 Adipic aoid 1 ∘ ∘ ∘ ∘ Example 9 Polyvinyl butyral 3GO 30 Phthalic acid 0.01 ∘ ∘ ∘ ∘ Example 10 Polyvinyl butyral 3GO 30 Phthalic acid 0.05 ∘ ∘ ∘ ∘ Example 11 Polyvinyl butyral 3GO 30 Phthalic acid 0.1 ∘ ∘ ∘ ∘ Example 12 Polyvinyl butyral 3GO 30 Phthalic acid 1 ∘ ∘ ∘ ∘ Example 13 Polyvinyl butyral 3GO 30 2-Ethylhexanoic acid 3 ∘ ∘ Δ ∘ Example 14 Polyvinyl butyral 3GO 30 Adipic acid 3 ∘ ∘ Δ ∘ Example 15 Polyvinyl butyral 3GO 30 Phthalic acid 3 ∘ ∘ Δ ∘ Example 16 Polyvinyl butyral 4GO 30 2-Ethylhexanoic acid 0.05 ∘ ∘ ∘ ∘ Example 17 Polyvinyl butyral 4GO 30 Adipic acid 0.05 ∘ ∘ ∘ ∘ Example 18 Polyvinyl butyral 4GO 30 Phthalic acid 0.05 ∘ ∘ ∘ ∘ Example 19 Polyvinyl butyral 3GT 30 2-Ethylhexanoic acid 0.05 ∘ ∘ ∘ ∘ Example 20 Polyvinyl butyral 3GT 30 Adipic acid 0.05 ∘ ∘ ∘ ∘ Example 21 Polyvinyl butyral 3GT 30 Phthalic acid 0.05 ∘ ∘ ∘ ∘ Example 22 Polyvinyl butyral DBEA 30 2-Ethylhexanoic acid 0.05 ∘ ∘ ∘ ∘ Example 23 Polyvinyl butyral DBEA 30 Adipic acid 0.05 ∘ ∘ ∘ ∘ Example 24 Polyvinyl butyral DBEA 30 Phthalic acid 0.05 ∘ ∘ ∘ ∘

TABLE-US-00002 TABLE 2 Interlayer filling material for a touch panel Plasticizer Organic acid Evaluation Parts Parts Properties by by Follow- of not weight weight Defoaming ability deteriorating Whitening Resin Type (phr) Type (phr) properties to steps ITO film resistance Comparative Polyvinyl butyral 3GO 30 Hydrochloric 0.01 ∘ ∘ x x Example 1 acid Comparative Polyvinyl butyral 3GO 30 Hydrochloric 0.05 ∘ ∘ x x Example 2 acid Comparative Polyvinyl butyral 3GO 30 Hydrochloric 0.1 ∘ ∘ x x Example 3 acid Comparative Polyvinyl butyral 3GO 30 Hydrochloric 1 ∘ ∘ x x Example 4 acid Comparative Polyvinyl butyral 3GO 30 Phosphoric 0.01 ∘ ∘ x ∘ Example 5 acid Comparative Polyvinyl butyral 3GO 30 Phosphoric 0.05 ∘ ∘ x ∘ Example 6 acid Comparative Polyvinyl butyral 3GO 30 Phosphoric 0.1 ∘ ∘ x ∘ Example 7 acid Comparative Polyvinyl butyral 3GO 30 Phosphoric 1 ∘ ∘ x ∘ Example 8 acid Comparative Polyvinyl butyral 3GO 30 Acetic acid 0.01 ∘ ∘ x ∘ Example 9 Comparative Polyvinyl butyral 3GO 30 Acetic acid 0.05 ∘ ∘ x ∘ Example 10 Comparative Polyvinyl butyral 3GO 30 Acetic acid 0.1 ∘ ∘ x ∘ Example 11 Comparative Polyvinyl butyral 3GO 30 Acetic acid 1 ∘ ∘ x ∘ Example 12 Comparative Polyvinyl butyral 3GO 30 Propionic acid 0.01 ∘ ∘ x ∘ Example 13 Comparative Polyvinyl butyral 3GO 30 Propionic acid 0.05 ∘ ∘ x ∘ Example 14 Comparative Polyvinyl butyral 3GO 30 Propionic acid 0.1 ∘ ∘ x ∘ Example 15 Comparative Polyvinyl butyral 3GO 30 Propionic acid 1 ∘ ∘ x ∘ Example 16 Comparative Polyvinyl butyral 3GO 30 Butyric acid 0.01 ∘ ∘ x ∘ Example 17 Comparative Polyvinyl butyral 3GO 30 Butyric acid 0.05 ∘ ∘ x ∘ Example 18 Comparative Polyvinyl butyral 3GO 30 Butyric acid 0.1 ∘ ∘ x ∘ Example 19 Comparative Polyvinyl butyral 3GO 30 Butyric acid 1 ∘ ∘ x ∘ Example 20 Comparative Polyvinyl butyral 3GO 30 Oxalic acid 0.01 ∘ ∘ x ∘ Example 21 Comparative Polyvinyl butyral 3GO 30 Oxalic acid 0.05 ∘ ∘ x ∘ Example 22 Comparative Polyvinyl butyral 3GO 30 Oxalic acid 0.1 ∘ ∘ x ∘ Example 23 Comparative Polyvinyl butyral 3GO 30 Oxalic acid 1 ∘ ∘ x ∘ Example 24 Comparative Polyvinyl butyral 3GO 30 2-Ethylhexanoic 0.05 ∘ ∘ x ∘ Example 25 acid Comparative Polyvinyl butyral 3GO 30 Adipic acid 0.05 ∘ ∘ x ∘ Example 26 Comparative Polyvinyl butyral 3GO 30 Phthalic acid 0.05 ∘ ∘ x ∘ Example 27 Comparative Polyvinyl butyral 3GO 30 2-Ethylhexanoic 0.05 ∘ ∘ x ∘ Example 28 acid Comparative Polyvinyl butyral 3GO 30 Adipio acid 0.05 ∘ ∘ x ∘ Example 29 Comparative Polyvinyl butyral 3GO 30 Phthalic acid 0.05 ∘ ∘ x ∘ Example 30

INDUSTRIAL APPLICABILITY

[0073] The present invention can provide an interlayer filling material for a touch panel which is used for filling an interlayer space between a touch panel and another component or an interlayer space between transparent conductive films included in the touch panel in production of a personal digital assistant, which is excellent in followability to steps of a decorative printing portion or wiring upon filling of an interlayer space (lamination) and also excellent in defoaming properties to release air bubbles entrapped during filling of an interlayer space (lamination) or air bubbles left near the steps, which is less likely to be whitened and less likely to deteriorate an ITO film even under a high-temperature and high-humidity environment. The present invention can also provide a laminate produced using the interlayer filling material for a touch panel.

REFERENCE SIGNS LIST

[0074] 1: Interlayer filling material for a touch panel of the [0075] present invention [0076] 2: Touch panel [0077] 3: Surface protection panel [0078] 4: Polarizing film [0079] 5: Decorative printing portion [0080] 6: Conductive film [0081] 7: Silver layer (Silver electrode) [0082] 8: Glass sheet [0083] 9: Interlayer filling material for a touch panel (width of 30 mm, length of 100 mm) [0084] 10: Tester