ANISOTROPIC EXOTHERMIC SHEET, INTERMEDIATE FILM FOR LAMINATED GLASS, AND LAMINATED GLASS

Abstract

The present invention aims to provide an anisotropic heating sheet which is capable of emitting generated heat in a specific direction to efficiently utilize its energy, and which has excellent handleability. The present invention also aims to provide an interlayer film for a laminated glass and a laminated glass each including the anisotropic heating sheet. Provided is an anisotropic heating sheet including: a laminate including an aerogel layer containing an aerogel and a heating layer, the aerogel layer having a tensile strain at break of 0.1% or higher as determined by a tensile test in conformity with JIS C 2151.

Claims

1. An anisotropic heating sheet comprising: a laminate including an aerogel layer containing an aerogel and a heating layer, the aerogel layer having a tensile strain at break of 0.1% or higher as determined by a tensile test in conformity with JIS C 2151.

2. The anisotropic heating sheet according to claim 1, wherein the aerogel is a polymer aerogel.

3. The anisotropic heating sheet according to claim 2, wherein the polymer aerogel contains at least one organic polymer material selected from the group consisting of resorcinol-formalin resins, cellulose nanofibers, polyimides, polyurethanes, and epoxy resins.

4. The anisotropic heating sheet according to claim 1, wherein the aerogel layer has a thickness of 10 m or more and 3 mm or less.

5. The anisotropic heating sheet according to claim 1, wherein the aerogel layer has a tensile strain at break of 0.3% or higher.

6. The anisotropic heating sheet according to claim 1, comprising a resin layer containing a thermoplastic resin on one or both surfaces of the laminate.

7. The anisotropic heating sheet according to claim 6, wherein the thermoplastic resin is a polyvinyl acetal or an ethylene-vinyl acetate copolymer.

8. An interlayer film for a laminated glass, the interlayer film comprising: the anisotropic heating sheet according to claim 1.

9. A laminated glass comprising: a pair of glass plates; and the interlayer film for a laminated glass according to claim 8 interposed between the pair of glass plates.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0105] FIG. 1 is a schematic view showing an exemplary cross section in the thickness direction of the anisotropic heating sheet of the present invention.

DESCRIPTION OF EMBODIMENTS

[0106] Embodiments of the present invention are specifically described in the following with reference to, but not limited to, examples.

Example 1

(1) Preparation of Aerogel Layer

[0107] TEMPO-oxidized cellulose nanofibers were dispersed in pure water to prepare a 0.9% by weight dispersion of the TEMPO-oxidized cellulose nanofibers. To 20 mL of the dispersion was dripped 10 mL of 0.1 M hydrochloric acid. The dispersion was then left to stand at room temperature for one hour to give a hydrogel. The obtained hydrogel was freeze-dried to give a 250-m-thick aerogel layer containing a polymer aerogel containing cellulose nanofibers.

[0108] The obtained polymer aerogel containing cellulose nanofibers had a tensile strain at break of 1.2% as determined by a tensile test under the conditions of a temperature of 23 C. and a humidity of 30% in conformity with JIS C 2151.

(2) Preparation of Heating Layer

[0109] On the obtained aerogel layer was formed a 20-nm-thick heating layer containing silver by sputtering under the conditions of a sputtering power of a 1,000 W direct current (DC), an atmospheric gas of argon, a gas flow rate of 50 sccm, and a sputtering pressure of 0.5 Pa.

[0110] The obtained heating layer had a surface resistivity of 3.3 /.

(3) Preparation of Resin Layer

[0111] To 100 parts by weight of polyvinyl butyral were added 40 parts by weight of a plasticizer, 0.5 parts by weight of a UV blocking agent, and 0.5 parts by weight of an antioxidant. They were sufficiently kneaded with a mixing roll to prepare a composition. The obtained composition was extruded from an extruder to give a single-layer resin layer having a thickness of 380 m.

[0112] The polyvinyl butyral had a hydroxy group content of 30 mol %, a degree of acetylation of 1 mol %, a degree of butyralization of 69 mol %, and an average degree of polymerization of 1,700. The plasticizer used was triethylene glycol di-2-ethylhexanoate (3GO). The UV blocking agent used was 2-(2-hydroxy-3-t-butyl-5-methylphenyl)-5-chlorobenzotriazole (Tinuvin 326 available from BASF SE). The antioxidant used was 2,6-di-t-butyl-p-cresol (BHT).

(4) Production of Anisotropic Heating Sheet

[0113] Two sheets of the obtained resin layer were provided, and the aerogel layer on which the heating layer was formed was interposed between the two sheets. The laminate was thermally pressure bonded to produce an anisotropic heating sheet having a laminated structure (first resin layer/heating layer/aerogel layer/second resin layer). The thermal pressure bonding was performed by a roll-to-roll method using a thermal pressure bonding laminator (MRK-650Y type available from MCK Co., Ltd.) under the conditions of a heating temperature of 90 C., a linear pressure in pressure bonding of 0.05 kN, and a feed tension of 20 N. The laminating rolls used for the thermal pressure bonding had upper and lower rolls both formed of rubber.

(5) Production of Laminated Glass

[0114] The obtained anisotropic heating sheet was cut into a size of 120 mm in length100 mm in width. The cut anisotropic heating sheet as an interlayer film for a laminated glass was interposed between two clear glass plates (100 mm in length100 mm in width2.5 mm in thickness) to give a laminate. Here, the cut anisotropic heating sheet was interposed such that it protruded from the ends of the clear glass plates by 10 mm in length respectively. The obtained laminate was put in a rubber bag and the pressure inside the rubber bag was reduced to 0.1 MPa. The laminate was then held at 90 C. for five minutes to be temporarily pressure-bonded while the air remaining between the glass plates and the interlayer film was removed. Subsequently, the temporarily pressure-bonded laminate was pressure-bonded in an autoclave for 20 minutes under the conditions of 150 C. and a pressure of 1.01 MPa. Thus, a laminated glass was produced. Thereafter, the resin layer was cut off from the anisotropic heating sheet protruding from the glass plates to expose the heating layer. Single-sided copper foil tape STS-CU42S (available from Sekisui Techno Shoji Nishi Nihon Co., Ltd.) was attached as an electrode such that the heating layer contacted the copper foil of the copper foil tape. The copper foil tape was further fixed by attaching a binder clip thereto.

Example 2

[0115] TEMPO-oxidized cellulose nanofibers were dispersed in pure water to prepare a 0.6% by weight dispersion of the TEMPO-oxidized cellulose nanofibers. To 20 mL of the dispersion was dripped 10 mL of 0.1 M hydrochloric acid. The dispersion was then left to stand at room temperature for one hour to give a hydrogel. The obtained hydrogel was freeze-fried to give a 250-m-thick aerogel layer containing a polymer aerogel containing cellulose nanofibers. The obtained aerogel layer had a tensile strain at break of 1.0%.

[0116] An anisotropic heating sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used.

Example 3

[0117] An amount of 1 g of Chitosan 10 (available from Wako Pure Chemical Industries, Ltd.) was dissolved in 50 mL of a 2% by volume aqueous acetic acid solution to prepare a chitosan solution. The chitosan solution was diluted in ultrapure water to a 10 g/L solution. To the 10 g/L aqueous chitosan solution was added 1.5 mL of a 9% by weight aqueous butyraldehyde solution. The solution was transferred into a petri dish. The petri dish was sealed and left to stand at 60 C. for 12 hours to prepare a hydrogel. After slow cooling at room temperature, the hydrogel was washed by repeating five-hour immersion in ultrapure water five times, and washed by immersion in methanol at a frequency of three times/day for three days. The obtained gel was dried at room temperature to give a 250-m-thick aerogel layer containing a polymer aerogel containing chitosan.

[0118] An anisotropic heating sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used.

[0119] The obtained aerogel layer had a tensile strain at break of 1.0%.

Example 4

[0120] A 3,000-m-thick aerogel layer was obtained as in Example 3 except that in preparation of the aerogel layer, the method for drying the aerogel was changed from drying at room temperature to supercritical drying with carbon dioxide.

[0121] A heat insulation sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used.

[0122] The obtained aerogel layer had a tensile strain at break of 1.2%.

Example 5

[0123] An amount of 2 g of Chitosan 10 (available from Wako Pure Chemical Industries, Ltd.) was dissolved in 100 mL of a 2% by volume aqueous acetic acid solution to prepare a chitosan solution. The chitosan solution was diluted in ultrapure water to a 10 g/L solution. To the 10 g/L aqueous chitosan solution was added 3.0 mL of a 9% by weight aqueous butyraldehyde solution. The solution was transferred into a petri dish. The petri dish was sealed and left to stand at 60 C. for 12 hours to prepare a hydrogel. After slow cooling at room temperature, the hydrogel was washed by repeating five-hour immersion in ultrapure water five times, and washed by immersion in methanol at a frequency of three times/day for three days. The obtained gel was dried by supercritical drying with carbon dioxide to give a 7,000-m-thick aerogel layer containing a polymer aerogel containing chitosan.

[0124] A heat insulation sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used.

[0125] The obtained aerogel layer had a tensile strain at break of 1.5%.

Example 6

[0126] A 2,000-m-thick aerogel layer was obtained as in Example 3 except that in preparation of the aerogel layer, the method for drying the aerogel was changed from drying at room temperature to supercritical drying with carbon dioxide.

[0127] A heat insulation sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used, and an ethylene-vinyl acetate copolymer resin (EVA, vinyl acetate content 30% by mass) was used as the resin constituting the resin layers instead of polyvinyl butyral.

[0128] The obtained aerogel layer had a tensile strain at break of 1.0%.

Example 7

[0129] A 1,000-m-thick aerogel layer was obtained as in Example 3 except that in preparation of the aerogel layer, the method for drying the aerogel was supercritical drying with carbon dioxide.

[0130] A heat insulation sheet and a laminated glass were obtained as in Example 3 except that the obtained aerogel layer was used, and the first resin layer and the second resin layer each had a thickness of 800 m.

[0131] The obtained aerogel layer had a tensile strain at break of 1.0%.

Example 8

[0132] In 50 g of a 0.01 M acetic acid solution were dissolved 2.5 g of urea and 2.5 g of a surfactant (hexadecyltrimethylammonium bromide). With stirring at room temperature, 5.0 g of pentaerythritol was dissolved in the solution. Then, 20.0 mL of silica alkoxide (methyltrimethoxysilane: MTMS) was added. To allow hydrolysis to proceed, stirring was continued for 30 minutes. The height of the stirred liquid was adjusted such that the dried gel had a thickness of 2.0 mm. Thereafter, the solution was left to stand in a 60 C. thermostat and allowed to gel for 96 hours under sealed conditions. The gel was then washed with methanol at a frequency of three times/day for at least three days to remove unreacted matter and the surfactant. The gel was dried by supercritical drying to give a 2,000-m-thick aerogel layer (organic-inorganic hybrid silica aerogel A layer).

[0133] An anisotropic heating sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used. When the obtained anisotropic heating sheet was cut into a size of 120 mm in length100 mm in width, the aerogel layer was sanded to a size of 120 mm in length100 mm in width to avoid breaking the aerogel layer. The obtained aerogel layer had a tensile strain at break of 0.20%.

Example 9

[0134] In 50 g of a 0.01 M acetic acid solution were dissolved 2.5 g of urea and 5.0 g of a surfactant (hexadecyltrimethylammonium bromide). With stirring at room temperature, 20.0 mL of silica alkoxide (methyltrimethoxysilane: MTMS) and 5.0 mL of diethylene glycol were added. To allow hydrolysis to proceed, stirring was continued for 30 minutes. The height of the stirred liquid was adjusted such that the dried gel had a thickness of 2.0 mm. Thereafter, the solution was left to stand in a 60 C. thermostat and allowed to gel for 96 hours under sealed conditions. The gel was then washed with methanol at a frequency of three times/day for at least three days to remove unreacted matter and the surfactant. The gel was dried by supercritical drying to give a 2,000-m-thick aerogel layer (organic-inorganic hybrid silica aerogel B layer).

[0135] A heat insulation sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used. When the obtained anisotropic heating sheet was cut into a size of 120 mm in length100 mm in width, the aerogel layer was sanded to a size of 120 mm in length100 mm in width to avoid breaking the aerogel layer.

[0136] The obtained aerogel layer had a tensile strain at break of 0.30%.

Comparative Example 1

[0137] A polyethylene terephthalate (PET) film having a thickness of 250 m (available from Toyobo Co., Ltd., COSMOSHINE A4300) was used as a substrate. On the substrate was formed a 20-nm-thick heating layer containing silver by sputtering with use of silver as a target under the conditions of a sputtering power of a 1,000 W direct current (DC), an atmospheric gas of argon, a gas flow rate of 50 sccm, and a sputtering pressure of 0.5 Pa.

[0138] The obtained heating layer had a surface resistivity of 3.3 /.

[0139] Two sheets of a resin layer were prepared as in Example 1, and the substrate on which the heating layer was formed was interposed between the two sheets. The laminate was thermally pressure bonded to produce a heating sheet having a laminated structure (first resin layer/heating layer/substrate/second resin layer). The thermal pressure bonding was performed by a roll-to-roll method using a thermal pressure bonding laminator (MRK-650Y type available from MCK Co., Ltd.) under the conditions of a heating temperature of 90 C. and a linear pressure in pressure bonding of 0.05 kN. Laminating rolls used for the thermal pressure bonding had upper and lower rolls both formed of rubber.

[0140] The obtained anisotropic heating sheet was cut into a size of 120 mm in length100 mm in width. The cut anisotropic heating sheet as an interlayer film for a laminated glass was interposed between two clear glass plates (100 mm in length100 mm in width2.5 mm in thickness) to give a laminate. Here, the cut anisotropic heating sheet was interposed such that it protruded from the ends of the clear glass plates by 10 mm in length respectively. The obtained laminate was put in a rubber bag and the pressure inside the bag was reduced to 0.1 MPa. Then, the laminate was held at 90 C. for five minutes to be temporarily pressure-bonded while the air remaining between the glass plates and the interlayer film was removed. Subsequently, the temporarily pressure-bonded laminate was pressure-bonded in an autoclave for 20 minutes under the conditions of 150 C. and a pressure of 1.01 MPa. Thus, a laminated glass was produced. Thereafter, the resin layer was cut off from the anisotropic heating sheet protruding from the glass plates to expose the heating layer. Single-sided copper foil tape STS-CU42S (available from Sekisui Techno Shoji Nishi Nihon Co., Ltd.) was attached as an electrode such that the heating layer contacted the copper foil of the copper foil tape. The copper foil tape was further fixed by attaching a binder clip thereto.

Comparative Example 2

[0141] In 50 g of a 0.01 M acetic acid solution were dissolved 2.5 g of urea and 5.0 g of a surfactant (hexadecyltrimethylammonium bromide). With stirring at room temperature, 25.0 mL of silica alkoxide (methyltrimethoxysilane: MTMS) was added. To allow hydrolysis to proceed, stirring was continued for 30 minutes. Thereafter, the solution was left to stand in a 60 C. thermostat and allowed to gel for 96 hours under sealed conditions. At this time, the height of the stirred liquid was adjusted such that the dried gel had a thickness of 2 mm. The gel was then washed with methanol at a frequency of three times/day for at least three days to remove unreacted matter and the surfactant. The gel was dried by supercritical drying to give a 2,000-m-thick aerogel layer (inorganic silica aerogel layer).

[0142] A heat insulation sheet and a laminated glass were obtained as in Example 1 except that the obtained aerogel layer was used. When the obtained anisotropic heating sheet was cut into a size of 120 mm in length100 mm in width, the silica gel was sanded to a size of 120 mm in length100 mm in width to avoid breaking the silica gel.

[0143] The obtained aerogel layer had a tensile strain at break of 0.08%.

(Evaluation)

[0144] The anisotropic heating sheets and laminated glasses obtained in the examples and comparative examples were evaluated by the following methods.

[0145] Tables 1 and 2 show the results.

(1) Evaluation of Handleability of Anisotropic Heating Sheet

[0146] Each of the anisotropic heating sheets obtained in the examples and comparative examples was cut into a size of 3 cm in width and 30 cm in length to prepare a specimen. The obtained specimen was put on a horizontal table. The specimen was warped such that an angle of 30 was formed by the table and a straight line connecting the center in the thickness direction of one longitudinal end of the specimen and the center in the thickness direction of the other longitudinal end. The handleability was evaluated from the state of the anisotropic heating sheet at this time according to the following criteria.

(Excellent): Neither the surface layers nor the aerogel broke, and no wrinkles or fold marks were formed.
(Good): Neither the surface layers nor the aerogel broke, but wrinkles or fold marks were formed.
(Fair): Only the aerogel broke.
x (Poor): The surface layer and the aerogel broke.

(2) Evaluation of Anisotropic Heating Properties

[0147] An alligator cable was attached to the electrode of each of the laminated glasses obtained in the examples and comparative examples. A thermocouple was attached, with adhesive tape, to the center of the glass surface on the first resin layer side and the center of the glass surface on the second resin layer side. The laminated glass in this state was left to stand in a low temperature chamber (available from Espec Corp. PU-2J) kept at 18 C.2 C. for 12 hours, and the glass surface temperature was recorded with a data logger (available from Keyence Corporation, NR-1000).

[0148] The alligator cable was connected to a DC power supply PWR800L (available from Kikusui Electronics Corp.). A voltage of 14 V was applied to measure the time t1 required for the temperature of the glass surface on the first resin layer side to reach 0 C. and the time t2 required for the temperature of the glass surface on the second resin layer side to reach 0 C. In the laminated glass of Comparative Example 1, t1 was 600 seconds and t2 was 605 seconds. In the laminated glasses of the examples produced using the aerogel-containing anisotropic heating sheets, t1 was shorter and t2 was longer than in Comparative Example 1. This shows that the laminated glasses had anisotropic heating properties.

[0149] In the laminated glasses of the examples, when the temperature of the glass surface on the second resin layer side was unlikely to reach 0 C., energization was terminated when a sufficient time passed after the lapse of t2 of the laminated glass of Comparative Example 1, and t2 was determined to be longer than t2 of Comparative Example 1.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Sheet First resin layer Type PVB PVB PVB PVB PVB EVA Structure Thickness (m) 380 380 380 380 380 380 Heating layer Type Ag Ag Ag Ag Ag Ag Surface resistance value (/) 3.3 3.3 3.3 3.3 3.3 3.3 Aerogel layer Type Cellulose Cellulose Chitosan Chitosan Chitosan Chitosan nanofibers nanofibers Thickness (m) 250 250 250 3000 7000 2000 Second resin layer Type PVB PVB PVB PVB PVB EVA Thickness (m) 380 380 380 380 380 380 Tensile strain at break of aerogel layer (%) 1.2 1.0 1.0 1.2 1.5 1.0 Evaluation Sheet handleability Anisotropic heating properties of laminated glass Present Present Present Present Present Present

TABLE-US-00002 TABLE 2 Comparative Comparative Example 7 Example 8 Example 9 Example 1 Example 2 Sheet First resin layer Type PVB PVB PVB PVB PVB structure Thickness (m) 800 800 800 380 380 Heating layer Type Ag Ag Ag Ag Ag Surface resistance value (/) 3.3 3.3 3.3 3.3 3.3 Aerogel layer Type Chitosan Organic Organic (Polyethylene Inorganic inorganic inorganic terephthalate) silica silica A silica B Thickness (m) 1000 2000 2000 250 2000 Second resin layer Type PVB PVB PVB PVB PVB Thickness (m) 800 800 800 380 380 Tensile strain at break of aerogel layer (%) 1.0 0.20 0.30 0.08 Evaluation Sheet handleability Anisotropic heating properties of laminated glass Present Present Present Present

INDUSTRIAL APPLICABILITY

[0150] The present invention can provide an anisotropic heating sheet which is capable of emitting generated heat in a specific direction to efficiently utilize its energy, and which has excellent handleability. The present invention also can provide an interlayer film for a laminated glass and a laminated glass each including the anisotropic heating sheet.

REFERENCE SIGNS LIST

[0151] 1 anisotropic heating sheet

[0152] 2 aerogel layer

[0153] 3 heating layer

[0154] 4 first resin layer

[0155] 5 second resin layer