POLY(VINYL ACETAL) RESIN COMPOSITION, ADHESIVE SHEET, INTERLAMINAR FILLING MATERIAL FOR TOUCH PANEL, AND LAMINATE

Abstract

The present invention aims to provide a polyvinyl acetal resin composition that is excellent in thermal stability and moldable by an extrusion method and can exhibit a high storage modulus even under high temperature, an adhesive sheet prepared from the polyvinyl acetal resin composition, an interlayer filling material for a touch panel prepared from the polyvinyl acetal resin composition, and a laminate produced using the interlayer filling material for a touch panel. The present invention relates to a polyvinyl acetal resin composition containing: a polyvinyl acetal; a photoradical polymerization initiator; and a monomer or oligomer having a radical polymerizable double bond.

Claims

1-7. (canceled)

8. An adhesive sheet comprising a polyvinyl acetal resin composition, wherein the polyvinyl acetal resin composition comprises: a polyvinyl acetal; a photoradical polymerization initiator; a monomer or oligomer having a radical polymerizable double bond; and optionally, a plasticizer, wherein a total amount of the polyvinyl acetal and, optionally, the plasticizer in the polyvinyl acetal resin composition is 50% by weight or more, and wherein the amount of the monomer or oligomer having a radical polymerizable double bond relative to 100 parts by weight of the polyvinyl acetal is 0.1 to 40 parts by weight, and wherein the polyvinyl acetal resin composition is capable of being molded into an article by an extrusion method.

9. An interlayer filling material for a touch panel 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, the interlayer filling material for a touch panel comprising the adhesive sheet according to claim 8.

10. The interlayer filling material for a touch panel according to claim 9, wherein the total amount of the polyvinyl acetal and the plasticizer is 50% by weight or more.

11. A laminate comprising: a touch panel; and the interlayer filling material for a touch panel according to claim 9, the interlayer filling material for a touch panel 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 interlayer spaces between transparent conductive films included in the touch panel.

12. The adhesive sheet according to claim 8, wherein the polyvinyl acetal is polyvinyl butyral.

13. The adhesive sheet according to claim 8, wherein the photoradical polymerization initiator is benzophenone.

14. The adhesive sheet according to claim 8, wherein the amount of the photoradical polymerization initiator relative to 100 parts by weight of the polyvinyl acetal is 0.1 to 5 parts by weight.

15. The adhesive sheet according to claim 8, wherein the monomer or oligomer having a radical polymerizable double bond is a polyfunctional monomer or oligomer having two or more radical polymerizable double bonds in a molecule.

16. The adhesive sheet according to claim 8, wherein the polyvinyl acetal resin composition comprises the plasticizer, and wherein the amount of the plasticizer relative to 100 parts by weight of the polyvinyl acetal is 30 parts by weight or lower.

17. The adhesive sheet according to claim 8, wherein the polyvinyl acetal resin composition comprises the plasticizer, and wherein the total amount of the polyvinyl acetal and the plasticizer in the polyvinyl acetal resin composition is 80% by weight or more.

18. The adhesive sheet according to claim 8, wherein the adhesive sheet is formed by an extrusion method.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0085] 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.

DESCRIPTION OF EMBODIMENTS

[0086] Embodiments of the present invention will be specifically described in the following with reference to, but not limited to, the examples.

Example 1

(1) Preparation of Polyvinyl Butyral

[0087] 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 1,800 and a degree of saponification of 99.3 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 0.2% by weight. The temperature of the mixture was adjusted to 15° C., and 21 g of n-butyraldehyde (n-BA) was added thereto with stirring. Then, 145 g of n-butyraldehyde (n-BA) was further added, so that 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 was set to 1.8% by weight. The mixture was heated to 50° C. and aged at 50° C. for two hours. After cooling and neutralization of the solution, the polyvinyl butyral resin was washed with water and then dried, thereby preparing polyvinyl butyral (PVB).

[0088] The obtained polyvinyl butyral 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 %.

(2) Preparation of a Polyvinyl Butyral Resin Composition

[0089] To 100 parts by weight of the obtained polyvinyl butyral were added 30 parts by weight of triethylene glycol-di-2-ethylhexanoate (3GO) as a plasticizer, 1 part by weight of benzophenone as a photoradical polymerization initiator, and 4 parts by weight of trimethylolpropane triacrylate as a monomer having a radical polymerizable double bond. They were sufficiently kneaded to give a polyvinyl butyral resin composition.

(3) Preparation of an Interlayer Filling Material for a Touch Panel

[0090] To 100 parts by weight of the obtained polyvinyl butyral were added 30 parts by weight of triethylene glycol-di-2-ethylhexanoate (3GO) as a plasticizer, 1 part by weight of benzophenone as a photoradical polymerization initiator, and 4 parts by weight of trimethylolpropane triacrylate as a monomer having a radical polymerizable double bond. They were sufficiently kneaded to give a mixture. The obtained mixture was press-molded into a sheet using a press-molding machine, thereby preparing an interlayer filling material for a touch panel having a thickness of 150 μm.

[0091] The obtained interlayer filling material for a touch panel was irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 1,200 seconds using an ultra-high pressure mercury lamp.

[0092] The storage modulus G′ at 200° C. of the sheet-shaped molded article before and after the irradiation was measured using a dynamic viscoelastometer such as ARES-G2 (TA Instruments) or ADVA-200 (IT Measurement Co., Ltd.) under the conditions of a temperature decreasing rate of 3° C./min, a frequency of 1 Hz, and a strain of 1%. The storage modulus G′ before the irradiation was 14,700 Pa and the storage modulus G′ after the irradiation was 127,000 Pa.

Example 2

[0093] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 1 part by weight of thioxanthone was used as the photoradical polymerization initiator. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 3

[0094] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 0.5 parts by weight of benzophenone was used as the photoradical polymerization initiator. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 4

[0095] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 10 parts by weight of ethoxy trimethylolpropane triacrylate was used as the monomer having a radical polymerizable double bond. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 5

[0096] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 4 parts by weight of ditrimethylolpropane tetraacrylate was used as the oligomer having a radical polymerizable double bond, instead of the monomer having a radical polymerizable double bond. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 6

[0097] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 4 parts by weight of dipentaerythritol hexaacrylate was used as the oligomer having a radical polymerizable double bond, instead of the monomer having a radical polymerizable double bond. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 7

[0098] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 10 parts by weight of trimethylolpropane triacrylate was used as the monomer having a radical polymerizable double bond. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 8

[0099] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that no plasticizer was used and 30 parts by weight of trimethylolpropane triacrylate was used as the monomer having a radical polymerizable double bond. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Example 9

[0100] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that 0.5 parts by weight of trimethylolpropane triacrylate was used as the monomer having a radical polymerizable double bond. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Comparative Example 1

[0101] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that the photoradical polymerization initiator and the monomer having a radical polymerizable double bond were not added. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Comparative Example 2

[0102] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that the monomer having a radical polymerizable double bond was not added. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Comparative Example 3

[0103] A polyvinyl butyral resin composition was obtained in the same manner as in Example 1 except that the photoradical polymerization initiator was not added. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Comparative Example 4

[0104] A polyvinyl butyral resin composition was obtained by adding 30 parts by weight of triethylene glycol-di ethylhexanoate (3GO) as the plasticizer and 0.05 parts by weight of boric acid to 100 parts by weight of polyvinyl butyral prepared by the same method as in Example 1 and kneading them sufficiently. An interlayer filling material for a touch panel was obtained in the same manner as in Example 1.

Comparative Example 5

(1) Preparation of an Acrylic Copolymer

[0105] An amount of 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 part by weight of hydroxy ethyl 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 in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet. After the air inside the reaction vessel was substituted with nitrogen, the solution was polymerized at 80° C. for eight hours to give an acrylic copolymer.

[0106] The obtained acrylic copolymer was diluted with tetrahydrofuran (THF) by a factor of 50 times. The resulting diluted solution was passed through a filter (material: polytetrafluoroethylene, pore size: 0.2 μm) to prepare a measurement sample. The obtained measurement sample was placed in a gel permeation chromatograph (produced by Waters, 2690 Separations Model) and subjected to GPC measurement under the conditions of a sample flow rate of 1 ml/min and a column temperature of 40° C. The molecular weight of the acrylic copolymer in terms of polystyrene was thus determined. Based on the measurement result, the weight average molecular weight (Mw) was obtained.

[0107] The obtained acrylic copolymer had a weight average molecular weight of 650,000.

[0108] The column used was GPC LF-804 (Showa Denko K.K.) and the detector used was a differential refractometer.

(2) Preparation of an Interlayer Filling Material for a Touch Panel

[0109] An amount of 100 parts by weight of the obtained acrylic copolymer was diluted with ethyl acetate to give an adhesive solution with a resin solid 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 available from Nippon Polyurethane Industry Co., Ltd., solid content: 45%), stirred for 15 minutes, applied to a mold release-treated surface of a mold release PET film (thickness: 50 μm) to a dry thickness of 150 μm, and dried at 80° C. for 15 minutes. On the obtained adhesive layer was placed another mold release PET film in such a manner that the mold release-treated surface thereof was in contact with the adhesive layer, thereby preparing a laminate. The resulting sheet was left to stand at 23° C. for five days to give an interlayer filling material for a touch panel (thickness: 150 μm) having a mold release PET film attached to each surface.

(Evaluation)

[0110] The polyvinyl butyral resin compositions and interlayer filling materials for a touch panel obtained in the examples and comparative examples were evaluated by the following methods.

[0111] Tables 1 and 2 show the results.

(1) Evaluation of the Thermal Stability of the Polyvinyl Butyral Resin Composition

[0112] The obtained polyvinyl butyral resin composition was subjected to heat treatment at 180° C. for one hour. The polyvinyl butyral resin composition after the heat treatment was visually observed. The case where gelling was not at all observed was rated “∘ (Good)” and the case where gelling was observed even in a part was rated “x (Poor)”.

(2) Measurement of the Gel Fraction Before and After Irradiation of the Polyvinyl Butyral Resin Composition with Light

[0113] Each of the polyvinyl butyral resin compositions obtained in the examples and comparative examples was extrusion-molded under the temperature condition of 200° C. into sheet-shaped molded articles having a thickness of 200 μm.

[0114] A sheet-shaped molded article obtained above was irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 1,200 seconds using an ultra-high pressure mercury lamp.

[0115] The sheet-shaped molded articles before and after the irradiation were immersed in ethyl acetate at 23° C. for 24 hours, taken out from the ethyl acetate, and dried under the condition of 110° C. for one hour. The weights of the dried test pieces were measured, and the gel fraction was calculated using the following equation.

Gel fraction (% by weight)=100×W.sub.2/W.sub.1

(W.sub.1: weight of the test piece before immersion, W.sub.2: weight of the test piece after the immersion and drying)
(3) Measurement of the Storage Modulus of the Polyvinyl Butyral Resin Composition Before and After Irradiation with Light

[0116] Each of the polyvinyl butyral resin compositions obtained in the examples and comparative examples was extrusion-molded at the temperature condition of 200° C. into sheet-shaped molded articles having a thickness of 200 μm.

[0117] Four sheet-shaped molded articles obtained above were stacked to give a laminate having a thickness of 800 μm. The laminate was used as a sample for measuring the storage modulus before UV irradiation.

[0118] Separately, the obtained sheet-shaped molded articles were irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 500 seconds using an ultra-high pressure mercury lamp. Four UV-irradiated sheet-shaped molded articles were stacked to give a laminate having a thickness of 800 μm. The laminate was used as a sample for measuring the storage modulus after UV irradiation.

[0119] The storage moduli G′ at 200° C. of the sample for measuring the storage modulus before UV irradiation and the sample for measuring the storage modulus after UV irradiation were measured using a dynamic viscoelastometer ARES-G2 (TA Instruments) under the conditions of a temperature decreasing rate of 3° C./min, a frequency of 1 Hz, and a strain of 1%.

(4) Evaluation of Adhesiveness of the Interlayer Filling Material for a Touch Panel

[0120] The interlayer filling material for a touch panel was cut to a size of 25 mm×100 mm and attached to a glass. A plasma-treated PET film (25 mm×100 mm) was attached thereto and the laminate was vacuum-laminated at 25° C., followed by pressure bonding with heat in an autoclave at 75° C. and 0.5 MPa for 30 minutes. An evaluation sample was thus prepared. The obtained evaluation sample was subjected to 180° peel test at 300 mm/min in conformity with JIS K 6854:1994 for determining the peel strength. The case where the peel strength was 5 N/25 mm or more was rated “∘ (Good)” and the case where the peel strength was less than 5 N/25 mm was rated “x (Poor)”.

(5) Evaluation of Adhesive Deposition of the Interlayer Filling Material for a Touch Panel

[0121] The interlayer filling material for a touch panel was punched out 50 times using a thomson blade (50 mm×50 mm), and whether or not adhesion of the interlayer filling material for a touch panel (adhesive deposits) to the thomson blade occurs was visually observed. The case where no adhesive deposits were observed on the thomson blade was rated “0 (Good)” and the case where adhesive deposits were observed was rated “x (Poor)”.

(6) Evaluation of Scattering Prevention Properties of the Interlayer Filling Material for a Touch Panel

[0122] One surface of the interlayer filling material for a touch panel was attached to a glass (15.0 cm×7.5 cm, thickness of 0.7 mm), and to the other surface of the interlayer filling material for a touch panel was attached an ITO-coated polyethylene terephthalate film (ITO-PET), thereby preparing a glass/interlayer filling material for a touch panel/ITO-PET film structure. The structure was pressure-bonded using a vacuum laminator at 70° C. and 1 atm for 30 minutes, treated in an autoclave at 85° C. and 0.5 MPa for 30 minutes, and decompressed after being cooled to 30° C. or lower. Then, the laminate was irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 1,200 seconds using an ultra-high pressure mercury lamp, thereby obtaining a laminate in which the interlayer space between the glass and the ITO-PET film was filled with the interlayer filling material for a touch panel.

[0123] To the obtained laminate was dropped an iron ball (130 g) from the height of 1 m in an environment of 23° C. The case where the laminate was not broken was scored 1. The case where the laminate was broken but glass fragments were not scattered and no fracture or cohesive failure was observed in the interlayer filling material for a touch panel was scored 2. The case where the laminate was broken and glass fragments were not scattered but a partial fracture was observed in the interlayer filling material for a touch panel was scored 3. The case where a small amount of glass fragments was scattered and a fracture or cohesive failure was observed in the interlayer filling material for a touch panel was scored 4. The case where glass fragments were scattered and a fracture or cohesive failure was observed in the interlayer filling material for a touch panel was scored 5. The scores 1 to 3 were rated “∘ (Good)” and the scores 4 and 5 were rated “x (Poor)”.

[0124] It is to be noted that glass powder generated from the glass itself at the part where the ball hit and glass pieces generated by breakage of the glass itself were not included in the glass fragments. The glass fragments evaluated were glass pieces generated by detachment of the glass from the interlayer filling material for a touch panel at the interface between the glass and the interlayer filling material for a touch panel and glass pieces to which the filling material adheres generated by the cohesive failure of the interlayer filling material for a touch panel.

(7) Evaluation of Defoaming Properties of the Interlayer Filling Material for a Touch Panel

[0125] To a white plate glass (76 mm×52 mm, thickness of 1.0 to 1.2 mm, 59112 available from Matsunami Glass Ind., Ltd.) was attached one surface of the interlayer filling material for a touch panel cut to the same size as the white plate glass, and 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 plate glass, thereby preparing a glass/interlayer filling material for a touch panel/ITO-PET film structure. In this process, bubbles were made to be entrapped at the interface between the glass and the interlayer filling material for a touch panel. Next, the structure was pressure-bonded using a vacuum laminator at 70° C. and 1 atm for 30 minutes, treated in an autoclave at 85° C. and 0.5 MPa for 30 minutes, and decompressed after being cooled to 30° C. or lower. Then, the resulting structure was irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 1,200 seconds using an ultra-high pressure mercury lamp, thereby obtaining a laminate in which the interlayer space between the glass and the ITO-PET film was filled with the interlayer filling material for a touch panel.

[0126] The obtained laminate was observed using a digital microscope (Keyence Corporation). The case where remaining bubbles were not observed was rated “∘ (Good)” and the case where remaining bubbles were observed was rated “x (Poor)”.

(8) Evaluation of Followability to Steps of the Interlayer Filling Material for a Touch Panel

[0127] A single-sided adhesive tape having a thickness of 75 μm in the shape of a square frame (outer frame: 76 mm×52 mm, inner frame: 56 mm×32 mm) was attached to a white plate glass (S9112 available from Matsunami Glass Ind., Ltd, size: 76 mm×52 mm, thickness: 1.0 to 1.2 mm) to form a step.

[0128] The interlayer filling material for a touch panel was cut to a size of 76 mm×52 mm and attached to the surface with a square frame-shaped step of the white plate glass. An ITO-coated polyethylene terephthalate film (ITO-PET available from Sekisui Nano Coat Technology) was cut to a size of 76 mm×52 mm and attached to the interlayer filling material for a touch panel. They were each attached in such a manner that entering of bubbles was avoided as far as possible. The resulting structure was pressure-bonded using a vacuum laminator at 70° C. and 1 atm for 30 minutes, treated in an autoclave at 85° C. and 0.5 MPa for 30 minutes, and decompressed after being cooled to 30° C. or lower. Next, the structure was irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 1,200 seconds using an ultra-high pressure mercury lamp, thereby obtaining a laminate in which the interlayer space between the glass and the ITO-PET film was filled with the interlayer filling material for a touch panel.

[0129] The obtained laminate was observed using a digital microscope (Keyence Corporation). The case where bubbles remaining at the interface with the step was observed was rated “x (Poor)” and the case where remaining bubbles were not observed was rated “∘ (Good)”.

(9) Evaluation of Foaming after High Temperature and High Humidity Treatment of the Interlayer Filling Material for a Touch Panel

[0130] Over the surface of a white plate glass (S9112 available from Matsunami Glass Ind., Ltd., size: 76 mm×52 mm, thickness: 1.0 to 1.2 mm) were uniformly dispersed particles (Micropearl available from Sekisui Chemical Co., Ltd.) formed of a divinylbenzene compound with a particle size of 40 μm as model contaminants at a density of 30 pcs/cm.sup.2.

[0131] The interlayer filling material for a touch panel was cut to a size of 76 mm×52 mm and attached to the surface where the model contaminants were dispersed of the white plate glass. An ITO-coated polyethylene terephthalate film (ITO-PET available from Sekisui Nano Coat Technology) was cut to a size of 76 mm×52 mm and attached to the interlayer filling material for a touch panel. They were each attached in such a manner that entering of bubbles was avoided as far as possible. The resulting structure was pressure-bonded using a vacuum laminator at 70° C. and 1 atm for 30 minutes, treated in an autoclave at 85° C. and 0.5 MPa for 30 minutes, and decompressed after being cooled to 30° C. or lower. Next, the structure was irradiated with light having a wavelength of 365 nm at an illuminance of 10 mW/cm.sup.2 for 1,200 seconds using an ultra-high pressure mercury lamp, thereby obtaining a laminate in which the interlayer space between the glass and the ITO-PET film was filled with the interlayer filling material for a touch panel.

[0132] Then, the resulting laminate was left to stand under high temperature and high humidity condition at a temperature of 85° C. and a humidity of 85% for 250 hours. The high temperature and high humidity treatment was thus carried out.

[0133] The structure after the high temperature and high humidity treatment was observed using a digital microscope (Keyence Corporation). The case where no foaming was observed was rated “∘ (Good)” and the case where foaming was observed was rated “x (Poor)”.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Interlayer Resin type Polyvinyl Polyvinyl Polyvinyl Polyvinyl Polyvinyl Polyvinyl Polyvinyl filling butyral butyral butyral butyral butyral butyral butyral material Plasticizer (parts by weight) 30 30 30 30 30 30 30 Hydrogen Type Benzo- Thio- Benzo- Benzo- Benzo- Benzo- Benzo- abstraction type phenone xanthone phenone phenone phenone phenone phenone photoinitiator Numer of parts 1 1 0.5 1 1 1 1 Monomer Type Trimeth- Trimeth- Trimeth- Ethoxy Ditrimeth- Dipenta- Trimeth- having ylolpropane ylolpropane ylolpropane trimeth- ylolpropane eryth- ylolpropane a radical triacrylate triacrylate triacrylate ylolpropane tetraacrylate ritol triacrylate polymerizable triacrylate hexaacrylate double bond Number of parts 4 4 4 10 4 4 10 Boric acid Number of parts — — — — — — — Evaluation Thermal stability ∘ ∘ ∘ ∘ ∘ ∘ ∘ (resin Gel fraction (%) Before irradiation 0 0 0 0 0 0 0 compo- with light sition) After irradiation 56.1 50.9 54.9 39.9 59.3 58.5 67.1 with light Storage modulus Before irradiation 14700 14100 14700 10600 14300 14100 13700 (Pa) at 200° C. with light After irradiation 127000 117000 125000 72600 132000 129000 200300 with light Evaluation Adhesiveness ∘ ∘ ∘ ∘ ∘ ∘ ∘ (interlayer Adhesive deposition ∘ ∘ ∘ ∘ ∘ ∘ ∘ filling Scattering prevention properties ∘ ∘ ∘ ∘ ∘ ∘ ∘ material) Defoaming properties ∘ ∘ ∘ ∘ ∘ ∘ ∘ Followability to steps ∘ ∘ ∘ ∘ ∘ ∘ ∘ Foaming after high-temperature, ∘ ∘ ∘ ∘ ∘ ∘ ∘ high-humidity treatment

TABLE-US-00002 TABLE 2 Compar- Compar- Compar- Compar- Compar- ative ative ative ative ative Example 8 Example 9 Example 1 Example 2 Example 3 Example 4 Example 5 Interlayer Resin type Polyvinyl Polyvinyl Polyvinyl Polyvinyl Polyvinyl Polyvinyl Acrylic filling butyral butyral butyral butyral butyral butyral copolymer material Plasticizer (parts by weight) 0 30 30 30 30 30 — Hydrogen Type Benzophenone Benzophenone — Benzophenone — — — abstraction type Numer of parts 1 1 — 1 — — — photoinitiator Monomer having Type Trimeth- Trimeth- — — Trimeth- — — a radical ylolpropane ylolpropane ylolpropane polymerizable triacrylate triacrylate triacrylate double bond Number of parts 30 0.5 — — 4 — — Boric acid Number of parts — — — — — 0.05 Evaluation Thermal stability ∘ ∘ ∘ ∘ ∘ x — (resin Gel fraction (%) Before irradiation 0 0 0 0 0 — — compo- with light sition) After irradiation 69.6 56.1 0 0.9 0.4 — — with light Storage modulus Before irradiation 39200 15200 15400 14900 14400 — — (Pa) at 200° C. with light After irradiation 1150000 51000 15400 15500 15000 — — with light Evaluation Adhesiveness ∘ ∘ ∘ ∘ ∘ ∘ ∘ (interlayer Adhesive deposition ∘ ∘ ∘ ∘ ∘ ∘ x filling Scattering prevention properties ∘ ∘ ∘ ∘ ∘ ∘ x material) Defoaming properties ∘ ∘ ∘ ∘ ∘ x x Followability to steps ∘ ∘ ∘ ∘ ∘ x x Foaming after high-temperature, ∘ ∘ x x x ∘ x high-humidity treatment

INDUSTRIAL APPLICABILITY

[0134] The present invention can provide a polyvinyl acetal resin composition that is excellent in thermal stability and moldable by an extrusion method and can exhibit a high storage modulus even under high temperature, an adhesive sheet prepared from the polyvinyl acetal resin composition, an interlayer filling material for a touch panel prepared from the polyvinyl acetal resin composition, and a laminate produced using the interlayer filling material for a touch panel.

REFERENCE SIGNS LIST

[0135] 1: Interlayer filling material for a touch panel of the present invention [0136] 2: Touch panel [0137] 3: Surface protection panel [0138] 4: Polarizing film [0139] 5: Decorative printing portion