Adhesive sheet

Abstract

The present device is an adhesive sheet having an adhesive layer consisting of an adhesive composition containing a thermosetting resin and a thermal foaming agent and a coating layer. The coating layer having a resin and provided on the adhesive layer. The coating layer is characterized in that it does not exhibit tackiness at room temperature. In addition, at least a part of the coating layer disappears in a region ranging from an interface between the adhesive layer and the coating layer to a surface of the coating layer by heating the adhesive sheet at a temperature not lower than a curing starting temperature of the adhesive layer and wherein the following inequation is satisfied: T3<T1, T1 is a thermal foaming temperature of the thermal foaming agent, and T3 is a glass transition temperature of the coating layer.

Claims

1. An adhesive sheet comprising: an adhesive layer consisting of an adhesive composition containing a thermosetting resin and a thermal foaming agent; and a coating layer comprising a resin and provided on the adhesive layer; characterized in that the coating layer does not exhibit tackiness at room temperature; the coating layer forming resin has a glass transition temperature (T3) thereof is at least 60 C. and not more than 92 C.; and at least a part of the coating layer disappears in a region ranging from an interface between the adhesive layer and the coating layer to a surface of the coating layer by heating the adhesive sheet at a temperature not lower than a curing starting temperature of the adhesive layer, wherein the following equation is satisfied:
T3<T1, wherein T1 is a thermal foaming temperature of the thermal foaming agent, and T3 is a glass transition temperature of the coating layer.

2. The adhesive sheet according to claim 1, characterized in that the thermosetting resin has a softening temperature of not higher than 105 C.

3. The adhesive sheet according to claim 1, characterized in that: an equation T1T2 is satisfied where T2 is a curing starting temperature of the adhesive layer.

4. The adhesive sheet according to claim 3, characterized in that T1 is 100 C. or higher to 200 C. or lower and T2 is 110 C. or higher to 250 C. or lower.

5. The adhesive sheet according to claim 1, characterized in that: an equation t20.6t1 is satisfied where t1 is a thickness of the adhesive layer prior to heating, and t2 is a thickness of the coating layer.

6. The adhesive sheet according to claim 5, characterized in that t2 is 0.5 m or more to 600 m or less.

7. The adhesive sheet according to claim 5, characterized in that t1 is 20 m or more to 1000 m or less.

8. The adhesive sheet according to claim 1, characterized in that the thermosetting resin contained in the adhesive composition has a weight average molecular weight of 450 or more to 1650 or less.

9. The adhesive sheet according to claim 8, characterized in that the thermosetting resin is an epoxy resin.

10. The adhesive sheet according to claim 9, wherein the epoxy resin is a semi-solid or solid at room temperature.

11. The adhesive sheet according to claim 1, characterized in that the thermal foaming agent is thermally expandable microspheres.

12. The adhesive sheet according to claim 1, characterized in that the thermal foaming agent is contained in an amount of 1 part to 30 parts by mass relative to 100 parts by mass of the thermosetting resin contained in the adhesive composition.

13. The adhesive sheet according to claim 1, further comprising a substrate on which the adhesive layer is formed.

14. The adhesive sheet according to claim 1, characterized in that the adhesive sheet is used to fill a void.

15. An image display device, portable electronic device, or automobile component, comprising the adhesive sheet according to claim 1.

Description

EXAMPLES

(1) The present invention will be illustrated in detail by way of the Examples (including Examples and Comparative Examples) below, but the present invention shall be not limited to those specific Examples. Note that unless otherwise specified in Examples, % and parts refers to mass % and parts by mass, respectively.

Examples 1-23 and Comparative Examples 1-3

(2) 1. Preparation of the Adhesive Layer Forming Coating Solution

(3) The following constituent components were homogeneously mixed at a solid content ratio (mass based) shown in Table 1 to prepare adhesive layer forming coating solution (a to k). The total solid content in each coating solution was 30 mass % to 50 mass %. The particularities of the thermosetting resins (A1 to A11) contained in each coating solution are shown in Table 2. Note that the compositions of Examples 1 and 2, and Comparative Examples 1-3 shown in Table 5 are compositions that do not contain thermally expandable microspheres, i.e. a thermal foaming agent, in the adhesive layer forming coating solution, and the compositions of all of the other examples are compositions that contain a thermal foaming agent.

(4) <<Constituent Components of Adhesive Layer Forming Coating Solution a to k>>

(5) Thermosetting resin (epoxy resin): Types described in Table 2 and parts by mass described in Table 1 Curing agent (solid content of 100%): Parts by mass described in Table 1 (dicyandiamide (DICY), from Japan Epoxy Resins Co., Ltd.) Curing accelerator (solid content of 100%): Parts by mass described in Table 1 (Curezol 2MZ-A, 2,4-diamine-6-[2-methylimidazolyl-(1)]-ethyl-s-triazine, from Shikoku Chemicals Corp.) Thermally expandable microspheres (thermal foaming agent): Parts by mass described in Table 1 (Matsumoto Microspheres, F100M, thermally expandable microspheres, mass average particle diameter: 17 to 23 m, thermal expansion temperature (same as the thermal foaming temperature T1): 120 C., maximum thermal expansion temperature: 160 C., expansion ratio: 10 times, from Matsumoto Yushi-Seiyaku Co., Ltd.)

(6) TABLE-US-00001 TABLE 1 Adhesive Layer Forming Adhesive Composition (Solid Content Ratio) Thermally Curing Starting Coating Thermosetting Resin Curing Curing Expandable Temperature Solution A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 Agent Accelerator Microspheres*.sup.1) (T2) C. a 100 11.1 0.5 10 148 b 100 8.4 0.5 10 150 c 100 8.9 0.5 10 151 d 100 4.4 0.5 10 152 e 100 10.0 0.5 10 155 f 100 11.1 0.5 10 155 g 100 3.2 0.5 10 158 h 100 11.1 0.5 10 155 i 100 11.1 0.5 10 155 j 100 2.3 0.5 10 158 k 100 2.1 0.5 10 159 *.sup.1)Not added to Example 1 and Comparative Examples 1 to 3.

(7) TABLE-US-00002 TABLE 2 Weight Softening Average Viscosity Epoxy Equivalent Temperature Molecule (190 C.) Type Product Name (g/eq) ( C.) Weight (dPa .Math. s) A1 Bis A liquid jER 828 184~194 liquid at room 370 (Mitsubishi temperature Chemical) A2 Bis A solid jER 834 230~270 Semi-solid at 470 0.05 (Mitsubishi room Chemical) temperature A3 Novolac NC-2000L 229~244 47~57 700~800 0.11 (Nippon Kayaku) A4 Bis A solid jER 1001 450~500 64 900 0.34 (Mitsubishi Chemical) A5 Novolac jER 157S70 200~220 70 900~1,000 0.28 (Mitsubishi Chemical) A6 Phenol N-775 184~194 75 1,100 0.78 novolac (DIC) A7 Bis A solid jER 1002 600~700 78 1,200 0.59 (Mitsubishi Chemical) A8 Cresol N-680 184~194 85 novolac (DIC) A9 Cresol N-695 184~194 95 novolac (DIC) A11 Bis A solid jER 1004 875~975 97 1,650 1.92 (Mitsubishi Chemical) A12 Bis A solid jER 1006FS 900~1,100 112 5.85 (Mitsubishi Chemical)
2. Preparation of the Coating Layer Forming Coating Solution

(8) The following constituent components were homogeneously mixed at the solid content ratios (mass based) shown in Table 3 to prepare coating layer forming coating solutions (A to G). The total solid content in each coating solution was 30 mass % to 50 mass %. The particularities of the thermoplastic resins (B1 to B7) contained in each coating solution are shown in Table 4.

(9) <<Constituent Components of the Coating Layer Forming Coating Solutions A to G>>

(10) Thermoplastic resin: Types described in Table 4 and parts by mass described in Table 3 Curing agent (solid content of 75%): Parts by mass described in Table 3 (Takenate 600, from Mitsui Takeda Chemicals, Inc., NCO content: 43.3%)

(11) TABLE-US-00003 TABLE 3 Coating Layer Forming Coating Agent Composition (Solid Content Ratio) Coating Thermoplastic Resin Curing Solution B1 B2 B3 B4 B5 B6 B7 Agent A 100 10 B 100 10 C 100 10 D 100 10 E 100 10 F 100 10 G 100 10

(12) TABLE-US-00004 TABLE 41 Glass Transition Temperature Category Type Product Name (T3) ( C.) B1 Polyester resin Vylon 200 67 (Toyobo) B2 Phenoxy resin Bisphenol A PKHH 92 (InChem) B3 Phenoxy resin flexible YL7174 15 backbone (Mitsubishi Chemical) B4 Phenoxy resin rigid YX6954 130 backbone A (Mitsubishi Chemical) B5 Phenoxy resin rigid YX8100 150 backbone B (Mitsubishi Chemicals) B6 Ethylene-vinyl EV250 23 acetate (DuPont-Mitsui copolymer Polychemicals) B7 Polyvinyl BM-S 60 butyral (Sekisui Chemical)
3. Preparation of the Adhesive Sheet

(13) Using the coating layer forming coating solutions and the adhesive layer forming coating solutions shown in Tables 5 to 8, a prescribed coating layer forming coating solution was coated onto a treated release surface of a release film (thickness of 38 m, Byna No. 23: from Fujimori Kogyo Co., Ltd.) using a Baker-type applicator. A coating layer with a prescribed thickness (5 m for Examples 1 to 17 and Comparative Examples 1 to 3, and the values shown in the Coating Layer Film Thickness section of Table 8 for Examples 18 to 23) was then formed by drying for 1 minute at 140 C. Next, a prescribed adhesive layer forming coating solution was applied onto the coating layer surface in the same manner as described above. Then the adhesive layer with a prescribed thickness (50 m for Examples 1 to 17 and Comparative Examples 1 to 3, and the values shown in the Pre-Heating Film Thickness section of Table 8 for Examples 18 to 23) was formed by drying at 120 C. for 1 to 2 minutes. After the adhesive layer surface and a substrate (thickness of 25 m, polyimide film: Kapton 100H, from DuPont-Toray Co., Ltd.) were laminated while applying heat of 80 C., the release film was peeled off to obtain the adhesive sheets of Examples 1 to 23 and Comparative Examples 1 to 3.

(14) 4. Evaluation

(15) The adhesive sheets obtained from the examples and comparative examples were measured or evaluated the following items using the following methods. The results are shown collectively in Tables 5 to 8.

(16) [Thermal Foaming Temperature (T1)]

(17) A dynamic viscoelasticity measuring device (model DMA Q800, from TA Instruments) was used for a measuring device, and 0.5 mg of thermally expandable microspheres were placed into an aluminum cup having a diameter of 6.0 mm (inner diameter of 5.65 mm) and a depth of 4.8 mm, and then an aluminum lid (5.6 mm, thickness of 0.1 mm) was placed at the top of a thermally expandable microspheres layer to prepare the sample. The sample height was measured by applying 0.01 N of force from above the sample using a pressure applicator. The sample was heated from 20 C. to 300 C. at a temperature increase rate of 10 C./min in a pressurized state with 0.01 N force, and the amount of displacement in the vertical direction of the pressure applicator was measured. The temperature at which displacement started in the positive direction was used as the thermal foaming temperature (T1).

(18) [Curing Starting Temperature (T2) of the Adhesive Layer]

(19) A differential scanning calorimeter (DSC3200, from Mac Science) was used as the measuring device. The sheet-shaped adhesive layer resin prepared above was heated from room temperature to 300 C. at a rate of 10 C./min, and the cross point of a DSC baseline in a normal range and a DSC rising line during the curing reaction was used as a curing starting temperature (T2).

(20) [Glass Transition Temperature (T3)] of the Coating Layer]

(21) The differential scanning calorimeter (DSC3200, from Mac Science) was used as the measuring device. The sheet-shaped coating layer resin prepared above was heated from room temperature to 300 C. at a rate of 10 C./min, and the DSC baseline change point was used as a glass transition point (T3).

(22) [Film Thickness (t2) of the Coating Layer]

(23) The total thickness of the release film and coating layer of laminate 2 prior to the formation of the adhesive layer (laminated article of the release film and coating layer) was measured for the adhesive sheets obtained from examples and comparative examples using a micrometer, and the film thickness (t2) of the coating layer was calculated by subtracting the thickness of the release film from the measurements. Note that as for the thickness of the release film, a measurement measured using a micrometer was used.

(24) [Film Thickness (t1) (Prior to Heating) of the Adhesive Layer]

(25) The total thickness of the release film, coating layer and adhesive layer of laminate 1 prior to the lamination of a substrate (laminated article of the release film, coating layer and adhesive layer) was measured for the adhesive sheets obtained from examples and comparative examples using a micrometer, and the film thickness (t1) of the adhesive layer was calculated by subtracting the thickness of the laminate 2 prior to the formation of the adhesive layer (laminated article of the release film and coating layer) from the measurements.

(26) [Film Thickness of the Adhesive Layer (After Heating)]

(27) For the adhesive sheets from examples and comparative examples, laminate 1 prior to the lamination of a substrate (polyimide film) (laminated article of the release film, coating layer and adhesive layer) was cut into a size of 5 cm5 cm, placed on a 1 mm thick SPCC steel plate such that the adhesive layer was contacted with the plate, and the release film was removed from the laminate 1. After placed in an oven heated to 190 C. for 30 minutes, it was taken out from the oven. Then the total thickness of the SPCC steel plate and adhesive layer (and coating layer) was measured, and the film thickness after heating of the adhesive layer was calculated by subtracting the thickness of the release film from the measurements.

(28) [Cracking of the Adhesive Layer (Cracks 1, 2)]

(29) For the samples from the examples and comparative examples, an arbitrary point on the side of adhesive layer was bent 180 degrees before heating and foaming either without coating layer or with a coating layer, and the conditions of each adhesive layer were visually observed. As a result, the samples for which any cracking of the adhesive layer itself (including the falling off of the adhesive layer from the substrate, the same shall apply hereinafter) was not observed were considered to be good and were marked , and the samples for which cracking was observed or which could not be bent 180 degrees were considered to be poor and were marked x. The absence of a coating layer was indicated by crack 1, and the presence of a coating layer was indicated by crack 2.

(30) [Tackiness of the Adhesive Layer (Tackiness 1, 2)]

(31) The adhesive sheets before heating, or heating and foaming from each examples and comparative examples were cut into a size of 5 cm5 cm, and six sheets were stacked such that the coating layers were opposed to each other, and then sandwiched between 1 mm thick glass plates. A 100 g load was applied on the top thereof, and then left for 24 hours in a room temperature (25 C.) and in a 30 C. environment, respectively, then the load was removed, and the samples were left for 30 minutes or longer at room temperature. After which the distance between glass plates were increased in vertical direction and the peeling condition was confirmed, and the adherence between the coating layers was evaluated. Note that when a coating layer was not present, the sheets were stacked such that the adhesive layers were opposed to each other, and the adherence between the adhesive layers was evaluated according the same method.

(32) Here, the state in which there existed delamination between an adhesive layer and a substrate of the adhesive sheet while the coating layers of respective adhesive sheets were adhered each other was considered that an adhesion existed, in other words, that the coating layer exhibited tackiness at room temperature. In contrast, when the distance between glass plates were increased in vertical direction and there observed the peeling occurred between the coating layers in contact with each other, it was considered that adherence did not exist, in other words, that the coating layer did not exhibit tackiness. The samples for which adherence was not observed in both environments were evaluated as , the samples that exhibited adherence only in the 30 C. environment were evaluated as , and the samples that exhibited adherence in both environments were evaluated as x. Note that the absence of a coating layer was indicated by tackiness 1, and the presence of a coating layer was indicated by tackiness 2.

(33) [Disappearance of the Coating Layer]

(34) For the adhesive sheets from examples and comparative examples, the laminate 1 prior to the lamination of a substrate (laminated article of the release film, coating layer and adhesive layer) was placed on a 1 mm thick SPCC steel plate such that the adhesive layer was contacted with the plate, and the release film was removed. Further 1 mm thick SPCC steel plate was stacked and fixed so as to form a gap that was twice the size of the total thickness of the adhesive layer and the thickness of the coating layer. After placed in an oven heated to 190 C. for 30 minutes, it was taken out from the oven. This was then cut vertically such that top of the SPCC steel plate and a cross section of the adhesive layer (and coating layer) can be observed, and the cross-section was observed using a microscope to determine the presence or absence of the coating layer. As a result, the samples for which the coating layer had disappeared and which had affixed to the SPCC steel plate were evaluated as , the samples for which the coating layer partially remained but which had affixed to the SPCC steel plate were evaluated as , and the samples for which the coating layer remained and which were not affixed to the SPCC steel plate were evaluated as x.

(35) [Foaming Scale Factor and Foaming Property of the Adhesive Sheets]

(36) The foaming scale factor of the adhesive sheets obtained from examples and comparative examples was calculated by dividing the above film thickness (after heating) of the adhesive layer by the sum of the film thickness (t2) of the coating layer and the film thickness (t1) (prior to heating) of the adhesive layer. As a result, samples with a foaming scale factor of 3 times or greater were considered as good and were indicated by , samples with a foaming scale factor of at least 2 times but less than 3 times were considered as good and were indicated by , and the samples for which foaming was not possible due to the increase in viscosity were considered as poor and were indicated by x.

(37) [Measuring the Adhesive Strength of the Adhesive Sheet]

(38) For the adhesive sheets from examples and comparative examples, laminate 1 prior to the lamination of a substrate (laminated article of the release film, coating layer, and adhesive layer) prior to lamination of the substrate were placed on a 1 mm thick SPCC steel plate (steel plate A) such that the adhesive layer was contacted with the plate, and the release film was removed. Further 1 mm thick SPCC steel plate (steel plate B) was stacked on the side of the coating layer and fixed (laminated article of the steel plate A, adhesive layer, coating layer and steel plate B). Next, this laminated article was placed in an oven heated to 190 C. for 30 minutes, and then it was taken out from the oven. The UTM-5T Tensilon Universal Testing Machine (from A&D Co., Ltd.) was used to measure the shear bond strength (units: MPa) by pulling the steel plate A and the steel plate B of the laminated article after heating in a direction parallel to the adhesion surface and opposite each other (a shearing direction).

(39) Note that, as described above, the disappearance of the coating layer was determined by observing a cross-section of the adhesive sheet using a microscope, but, depending on the sample, determining the disappearance of the coating layer using the above method was difficult when both the adhesive layer and the coating layer were transparent. In such a case, disappearance of the coating layer may be determined according to the following method. When the coating layer disappears, and the adhesive layer adheres to the steel plate A and the steel plate B, the shear bond strength increases comparing when only the coating layer is adhered to the steel plates. Therefore, a laminated article provided with a coating layer on the release film is provided between the steel plate A and the steel plate B in the same manner as above, and the shear bond strength (Pc) of the coating layer alone is measured.

(40) Note that the Pc values for the coating layers made from the coating layer forming coating solutions A, B, C, D, E, F and G shown in Table 3 were respectively 11 MPa, 16 MPa, 16 MPa, 15 MPa, 13 MPa, 7 MPa and 8 MPa.

(41) Furthermore, based on a ratio (Pm/Pc) of the shear bond strength measurement value (Pm) for the steel plate A and the steel plate B of the laminated article after heating to the shear bond strength (Pc) of the coating layer alone, the disappearance of the coating layer was evaluated. Here, the samples for which the (Pm/Pc) value was more than 110% were indicated by , the samples with more than 100% but at or below 110% were indicated by , and the samples with 100% or less were indicated by x. Note that the samples for which the shape of the adhesive layer was not maintained and measurement was not possible were indicated by -.

(42) TABLE-US-00005 TABLE 5 Adhesive Layer Evaluation Type of Coating Film Coating Layer Adhesive Including Disap- Solution Thickness Curing Glass Layer Coating pearance Adhesive Coating (m) Softening Starting Transition Film Alone Layer of the Layer Layer t1 (Before Tem- Tempera- Temperature Thickness Crack Tack Crack Tack Coating Pm Forming Forming Heating) perature ture (T2) (T3) ( C.) t2 (m) 1 1 2 2 Layer (Mpa) Comparative c F 50 47-57 151 23 5 X X 19 Example 1 Comparative c C 50 47-57 15 5 X X 19 Example 2 Example 1 c B 50 47-57 92 5 X 19 Example 2 c A 50 47-57 67 5 X 19 Comparative k B 50 112 159 92 5 X X 16 Example 3

(43) As shown in Table 5, Comparative Examples 1 and 2 and Examples 1 and 2, which used novolac with a softening temperature of 47 C. to 57 C. in the adhesive layer, exhibited tackiness by the adhesive layer alone. In Comparative Examples 1 and 2, in which a phenoxy resin with a glass transition temperature of 92 C. and a polyester resin with a glass transition temperature of 67 C. was used as a coating layer respectively, the coating layer exhibited tackiness at room temperature, and tackiness of the adhesive sheet in which the coating layer was laminated on the contact layer, could not be prevented. In contrast, in Examples 1 and 2, in which an ethylene-vinyl acetate copolymer with a glass transition temperature of 23 C. and a phenoxy resin with a glass transition temperature of 15 C. was used as the coating layer respectively, the coating layer did not exhibit tackiness at room temperature, demonstrating that the tackiness was suppressed in the adhesive sheet in which the coating layer was laminated on the contact layer, providing an improved workability.

(44) Further, in Comparative Example 3, in which a solid bisphenol A type epoxy resin with a softening temperature of 112 C. was used as the adhesive layer, the adhesive layer alone did not exhibit tackiness at room temperature, but cracking occurred. In an adhesive sheet for which a phenoxy resin with a glass transition temperature of 92 C. was laminated on this adhesive layer as a coating layer, no tackiness was observed and the occurrence of cracking was suppressed, but disappearance of the coating layer after heating was not observed, demonstrating that the adhesive strength was low.

(45) From the those results, an advantageous effect from the configuration of the present invention was confirmed, which is, the coating layer does not exhibit tackiness at room temperature, and at least a part of the coating layer disappears in the region ranging from an interface between the adhesive layer and the coating layer to a surface of the coating layer by heating the adhesive sheet at a temperature not lower than the curing starting temperature of the adhesive layer.

(46) TABLE-US-00006 TABLE 6 Adhesive Layer Type of Costing Film Coating Layer Solution Thickness (m) Curing Glass Adhesive Coating t1 Thermal Starting Transition Film Layer Layer (Before After Foaming Softening Temp. Temp. Thickness Forming Forming Heating) Heating Temp. Temp. (T2) (T3) ( C.) t2 (m) Example 3 c G 50 >300 120 47-57 151 60 5 Example 4 c B 50 >300 47-57 67 5 Example 5 c A 50 >300 47-57 92 5 Example 6 c D 50 227 47-57 130 5 Example 7 c E 50 245 47-57 150 5 Foaming Evaluation Scale Adhesive Layer Including Coating Disappearance Factor Alone Layer Foaming of the Coating t2/t1 (times) Crack 1 Tack 1 Crack 2 Tack 2 Performance Layer Example 3 0.1 >5.5 X Example 4 0.1 >5.5 X Example 5 0.1 >5.5 X Example 6 0.1 4.1 X Example 7 0.1 4.5 X

(47) In Examples 3 to 7, novolac epoxy resins having a softening temperature of from 47 to 57 C. were used in each example as an adhesive layer, on which different kinds of coating layers were laminated to form an adhesive sheets. The adhesive layer alone exhibited tackiness, but the adhesive layers of Examples 3 to 7, in which the coating layer that did not exhibit tackiness at room temperature and has a glass transition temperature of from 60 C. to 150 C. was used, suppressed tackiness. Also, an excellent foaming characteristic was obtained in each Examples 3 to 7.

(48) While the coating layer completely disappeared in Examples 3 to 6 in which a glass transition temperature of the coating layer was from 60 C. to 130 C., only a partial disappearance of the coating layer was observed in Example 7, in which a glass transition temperature of the coating layer was 150 C., and it was also observed decreasing adhesive strength.

(49) From those results, it may be preferable that the glass transition temperature of the coating layer is at least 60 C. to not more than 140 C.

(50) TABLE-US-00007 TABLE 7 Evaluation Type of Coating Adhesive Layer Coating Adhesive Including Solution Film Layer Foaming Layer Coating Adhesive Coating Thickness (m) Film Scale Alone Layer Disappearance Layer Layer t1 (Before After Thickness Factor Crack Tack Crack Tack Foaming of the Coating Forming Forming Heating) Heating t2 (m) t2/t1 (times) 1 1 2 2 Performance Layer Example 8 b B 50 165 5 0.1 3.0 X Example 4 c B 50 >300 5 0.1 >5.5 X Example 5 c A 50 >300 5 0.1 >5.5 X Example 9 d B 50 >300 5 0.1 >5.5 X Example 10 e B 50 >300 5 0.1 >5.5 X Example 11 f B 50 >300 5 0.1 >5.5 X Example 12 g B 50 180 5 0.1 3.3 X Example 13 h B 50 215 5 0.1 3.9 X Example 14 i B 50 185 5 0.1 3.4 X Example 15 j B 50 120 5 0.1 2.2 X

(51) As shown in Table 7, in the case of the Adhesive Layer Alone, there were no examples which were excellent in all of Crack 1, Tackiness 1 and foaming property (every example has at least one x). Nevertheless, in the case of the Including Coating Layer, in which a coating layer was added, Tackiness 2 was improved. From this result, examples which were excellent in all of Crack 2, Tackiness 2 and the foaming property were obtained (Examples 4, 5, and 9 to 15).

(52) Note that it is not described in the tables, but it was found that when the adhesive layer-forming coating solution a, in which A1 was used as thermosetting resin in the adhesive composition, an excellent properties, such as foaming property, was hard to obtain. Based on those results, it was suggested that a semi-solid or solid resin was preferable to be used as the thermosetting resin to be added to the adhesive composition.

(53) From the results in Examples 4, 5, and 8 it was found that even if Adhesive Layer Alone itself was sticky, it shall be covered with the existing coating layer, and thus it could play an important role in preventing a decrease in workability even without a separator (Tackiness 2 was marked ). Further, it was determined from the results in Examples 9 to 15 that even when cracking occurred within the Adhesive Layer Alone, the cracked film was held in place because of the existing coating layer, and thus the coating layer disappeared by heating (incorporated into the adhesive layer) and did not impair the working efficiency (Crack 2 was marked and the Coating Layer Disappearance was marked ).

(54) TABLE-US-00008 TABLE 8 Type of Coating Adhesive Layer Coating Solution Film Thickness (m) Layer Evaluation Adhesive Coating t1 Film Foaming Including Disappearance Layer Layer (Before After Thickness t2 Scale Factor Coating Layer Foaming of the Coating Forming Forming Heating) Heating (m) t2/t1 (times) Crack 2 Tack 2 Performance Layer Example 4 50 >300 5 0.1 >6.0 Example 18 c B 35 225 20 0.6 6.4 Example 19 50 >300 25 0.5 >6.0 Example 20 30 145 25 0.8 4.8 Example 21 36 >300 4 0.1 >7.5 Example 5 c A 50 >300 5 0.1 >5.5 Example 22 34 >300 6 0.2 >7.5 Example 23 30 270 10 0.3 6.8

(55) As shown in Table 8, the examples in which the film thickness t2 of the coating layer was 60% or less of the film thickness t1 of the adhesive layer (Examples 4, 18, 19, 21, 5, 22 and 23) exhibited excellent disappearance of the coating layer, compared to the ones in which the film thickness t2 of the coating layer was 83% of the film thickness t1 of the adhesive layer (Example 20). However, the evaluation of Example 20 shows that it shall be sufficient for practical use.