RESIN COMPOSITION, BONDING FILM, LAYERED BODY INCLUDING RESIN COMPOSITION LAYER, LAYERED BODY, AND ELECTROMAGNETIC WAVE SHIELDING FILM

Abstract

Provided are: a resin composition, containing a polyester polyurethane resin (A), an epoxy resin (B), and a polyamide resin (C); as well as a bonding film, a layered body including a resin composition layer, a layered body, and an electromagnetic wave shielding film, each using the resin composition.

Claims

1. A resin composition, comprising: a polyester polyurethane resin (A); an epoxy resin (B); and a polyamide resin (C).

2. The resin composition according to claim 1, wherein a content of the polyester polyurethane resin (A) is from 10% by mass to 70% by mass, and a content of the polyamide resin (C) is from 10% by mass to 70% by mass, each with respect to a total amount of the polyester polyurethane resin (A), the epoxy resin (B), the polyamide resin (C), and an imidazole silane compound (E) that may be included as an optional component in the resin composition.

3. The resin composition according to claim 1, further comprising an organic filler (D).

4. The resin composition according to claim 3, wherein a content of the organic filler (D) is from 5 parts by mass to 40 parts by mass with respect to the total amount, of 100 parts by mass, of the polyester polyurethane resin (A), the epoxy resin (B), the polyamide resin (C), and the imidazole silane compound (E) that may be included as an optional component in the resin composition.

5. The resin composition according to claim 1, further comprising the imidazole silane compound (E).

6. The resin composition according to claim 5, wherein a content of the imidazole silane compound (E) is from 0.1% by mass to 10% by mass with respect to the total amount of the polyester polyurethane resin (A), the epoxy resin (B), the polyamide resin (C), and the imidazole silane compound (E) in the resin composition.

7. The resin composition according to claim 1, wherein the epoxy resin (B) comprises at least one of a bisphenol A type epoxy resin or a novolak type epoxy resin.

8. The resin composition according to claim 1, wherein a number average molecular weight of the polyester polyurethane resin (A) is from 10,000 to 80,000, and a molecular weight per urethane bond in the polyester polyurethane resin (A) is 200 to 8,000.

9. The resin composition according to claim 1, wherein an acid value of the polyester polyurethane resin (A) is from 0.1 mgKOH/g to 20 mgKOH/g.

10. The resin composition according to claim 1, wherein a diol component configuring the polyester polyurethane resin (A) comprises a diol having a side chain.

11. The resin composition according to claim 1, wherein the polyester polyurethane resin (A) comprises a polyester polyurethane resin having a polyester structure that has a number average molecular weight of from 8,000 to 30,000.

12. The resin composition according to claim 1, comprising, when a total amount of a diamine component configuring the polyamide resin (C) is 100 mol %, 20 mol % or more of piperazine as the diamine component.

13. The resin composition according to claim 1, further comprising a metal filler (F).

14. The resin composition according to claim 13, wherein a content of the metal filler (F) is from 10 parts by mass to 350 parts by mass with respect to the total amount of 100 parts by mass of the polyester polyurethane resin (A), the epoxy resin (B), the polyamide resin (C), and the imidazole silane compound (E) that may be included as an optional component in the resin composition.

15. The resin composition according to claim 13, wherein the metal filler (F) is a conductive filler.

16. A bonding film, comprising: a resin composition layer that consists of the resin composition according to claim 1; and a release film that is in contact with at least one surface of the resin composition layer, wherein the resin composition layer is in a B-stage state.

17. A layered body including a resin composition layer, the layered body comprising: a resin composition layer that consists of the resin composition according to claim 1; and a base film that is in contact with at least one surface of the resin composition layer, wherein the resin composition layer is in a B-stage state.

18. A layered body, comprising a cured layer obtained by curing the resin composition according to claim 1.

19. An electromagnetic wave shielding film, comprising a resin composition layer that consists of the resin composition according to claim 1.

Description

EXAMPLES

[0255] Hereinafter, the present invention will be more specifically described based on Examples. The present invention is not limited to these Examples. Further, “parts” and “%” indicated below mean “parts by mass” and “% by mass”, respectively, unless otherwise specified.

[0256] 1. Raw Materials

[0257] 1-1. Polyester Resin

[0258] Commercial products and synthetic products were used as polyesters to be used in the production of polyester polyurethanes.

[0259] <Commercial Product>

[0260] As a commercial product, Aronmelt PES-360HVXM30 (trade name; number average molecular weight 20,000) manufactured by Toagosei Co., Ltd. was used.

[0261] <Synthesis of Polyester>

[0262] In a flask equipped with a stirrer, a nitrogen introduction tube, a distillation tube, and a thermometer, 201 parts by mass of dimethyl terephthalate, 86 parts by mass of ethylene glycol, 140 parts by mass of neopentyl glycol, 0.9 parts by mass of trimethylolpropane, and 0.22 parts by mass of zinc acetate as a catalyst were charged, the temperature was raised while introducing nitrogen to distill off methanol at from 150° C. to 180° C. Then, 183 parts by mass of isophthalic acid, 0.6 parts by mass of trimethylolpropane, and 0.12 parts by mass of antimony trioxide as a catalyst were added, and water was distilled off at from 180° C. to 210° C. Thereafter, while gradually reducing the pressure, the reaction was continued for 6 hours at 230° C. under the reduced pressure of 200 Pa. The number average molecular weight of the obtained polyester resin was 7,000. Then, 180 parts by mass of the synthesized polyester resin was taken and 378 parts by mass of toluene and 42 parts by mass of methyl isobutyl ketone were added thereto, to prepare a polyester solution (PES-1).

[0263] 1-2. Polyester Polyurethane Resin

[0264] Polyester urethane resins a1 to a7 were obtained by the following methods.

[0265] (1) Polyester Urethane Resin a1

[0266] in a flask equipped with a stirrer, a reflux dehydrator, and a distillation tube, 600 parts by mass of PES-360HVXM30, 100 parts by mass of toluene, and 20 parts by mass of neopentyl glycol were charged. After raising the temperature to 120° C. to distill off 100 parts by mass of the solvent containing water, the temperature was lowered to 105° C., and 0.4 parts by mass of 2,2-dimethylolpropionic acid was charged and dissolved therein. Thereafter, 34 parts by mass of hexamethylene diisocyanate was added and, after 30 minutes, 0.2 parts by mass of dibutyl tin dilaurate was added. After continuing the reaction for 6 hours, a solution of polyester urethane resin a1 was obtained by diluting with toluene/2-propanol to adjust the solid content concentration to 30%. The number average molecular weight of the resin was 36,000 and the acid value was 2 mgKOH/g.

[0267] (2) Polyester Urethane Resins a2 to a8

[0268] Polyester urethane resins a2 to a1 were each obtained by synthesizing under the same conditions as polyester urethane resin a1, except that the polyester, the diol, and the diisocyanate as the raw materials were changed as shown in Table 1.

TABLE-US-00001 TABLE 1 Polyester urethane resin a1 a2 a3 a4 a5 a6 a7 a8 Polyester PES-360HVXM30 600 600 600 600 600 — — 600 PES-1 — — — — — 600 600 — Diol component Neopentyl glycol 20 — — 133 — 65 — — 2-Butyl-2-ethyl-1,3-propanediol — 30 — — — — — — 1,4-Butandiol — — — — 17 — — — 2,2-Dimethylolpropionic acid 0.4 0.4 0.5 0.5 0.4 1.4 0.4 26 Isocyanate component Hexamethylene diisocyanate 34 34 3 216 34 106 1.5 34 Glass transition temperature of polyester (° C.) 65 65 65 65 65 62 62 65 Number average molecular weight Mn 36,000 35,000 32,000 40,000 40,000 15,000 9,000 19,000 Molecular weight per urethane bond 920 920 10,700 160 1,030 380 3,000 490 Acid value (mg KOH/g) 2 2 2 2 2 3 11 42

[0269] The unit of the numerical value in each component column shown in Table 1 is parts by mass.

[0270] 1-3. Epoxy Resin (B)

[0271] The following commercial products were used.

[0272] (1) Epoxy Resin b1

[0273] Bisphenol A novolak type epoxy resin “EPICLON N-865” (trade name) manufactured by DIC Corporation

[0274] (2) Epoxy Resin b2

[0275] Bisphenol A type epoxy resin “jER 1055” (trade name) manufactured by Mitsubishi Chemical Corporation

[0276] 1-4. Polyamide Resin (C)

[0277] (1) Polyamide Resin c1

[0278] Polyamide resin c1 was synthesized as follows.

[0279] In a flask equipped with a stirrer, a reflux dehydrator, and a distillation tube, 65 parts by mass of azelaic acid, 190 parts by mass of dodecanedioic acid, 100 parts by mass of piperazine, and 120 parts by mass of distilled water were charged. After raising the temperature to 120° C. to distill off water, the temperature was raised to 240° C. at a rate of 20° C./hour, and the reaction was continued for 3 hours to obtain polyamide resin ci. The amine value of this resin was 4.5 mgKOH/g.

[0280] (2) Polyamide Resin c2

[0281] Polyamide resin c2 was synthesized as follows.

[0282] In a flask equipped with a stirrer, a reflux dehydrator, and a distillation tube, 485 parts by mass of dimer acid, 100 parts by mass of hexamethylenediamine, and 120 parts by mass of distilled water was charged. After raising the temperature to 120° C. to distill off water, the temperature was raised to 240° C. at a rate of 20° C./hour, and the reaction was continued for 3 hours to obtain polyamide resin c2. The amine value of this resin was 4.5 mgKOH/g.

[0283] 1-5. Organic Filler (D)

[0284] (1) Organic Filler d1

[0285] Urethane beads “TK-800T” (trade name; average particle diameter 8 μm) manufactured by Negami Kogyo Co., Ltd.

[0286] (2) Organic Filler d2

[0287] Acrylic beads “J-4P” (trade name; average particle diameter 2.2 μm) manufactured by Negami Kogyo Co., Ltd.

[0288] 1-6. Imidazole Silane Compound (E)

[0289] 1-(2-Hydroxy-3-trimethoxysilylpropoxypropyl)imidazole

[0290] 1-7. Metal Filler (F)

[0291] Copper powder “FCC-115A” (trade name; in particle size distribution, the amount of particles of 45 μm or less is more than 90% by mass, the amount of particles of from 45 μm to 63 μm is less than 10% by mass, and the amount of particles of from 63 μm to 75 μm is less than 3% by mass), manufactured by Fukuda Metal Foil Powder Industry Co., Ltd,

[0292] 1-8. Flame Retardant

[0293] Aluminum dimethylphosphinate “Exolit OP935” (trade name) manufactured by Clariant

[0294] 1-9. Curing Promoter

[0295] Imidazole-based curing promoter “Curesol C11-Z” (trade name) manufactured by Shikoku Kasei Kogyo Co., Ltd.

[0296] 1-10. Carbon Black

[0297] Carbon black “MA-100” (trade name, arithmetic mean particle diameter 24 nm) manufactured by Mitsubishi Chemical Corporation

[0298] 1-11. Solvent

[0299] A mixed solvent consisting of toluene, methyl isobutyl ketone, and 2-propanol (mass ratio=100:20:20)

Examples 1 to 21 and Comparative Examples 1 to 3

[0300] To a flask equipped with a stirrer, the raw materials were added at the ratio shown in Table 2, and stirred under heating at 60° C. for 6 hours to dissolve the component (A), the component (B), the component (C), the component (E) and the curing promoter in the solvent and then disperse the component (D), the component (F), carbon black and the flame retardant, thereby producing the respective liquid resin compositions.

[0301] These liquid resin compositions were used to prepare coverlay films, bonding sheets, and adhesion test pieces A and B as follows.

[0302] (1) Preparation of Coverlay Film

[0303] The liquid resin composition is roll-coated onto the surface of a polyimide film having a thickness of 25 μm so that the thickness after drying was 15 μm, and dried at 120° C. for 2 minutes to obtain a coverlay film that includes a resin composition layer,

[0304] (2) Preparation of Adhesive Test Piece A

[0305] A gold-plated copper foil with a thickness of 35 μm was prepared. Then, the gold-plated surface was layered so as to be brought into contact with the surface of the resin composition layer of the coverlay film, and laminating was performed under the conditions of 150° C., 0.3 MPa, and 1 m/min. The obtained layered body (polyimide film/resin composition layer/gold-plated copper foil) was subject to thermal compression bonding for 5 minutes under the conditions of 150° C. and 3 MPa, and then further underwent after-cure (post-curing) at 160° C. for 2 hours in an oven, by which an adhesion test piece A was obtained.

[0306] (3) Preparation of Bonding Sheet

[0307] A releasable PET film with a thickness of 35 μm was prepared. Then, the liquid resin composition was roll-coated onto the surface thereof so that the thickness after drying was 25 μm, and dried at 140° C. for 2 minutes to obtain a bonding sheet that includes a resin composition layer.

[0308] (4) Preparation of Adhesion Test Piece B

[0309] A nickel-plated SUS (stainless steel) 304 plate with a thickness of 300 μm, and a flexible printed wiring board in which a copper wiring pattern is formed on the surface of a polyimide film with a thickness of 25 μm and a coverlay film with a thickness of 37.5 μm having a through hole with a diameter of 1 mm was layered on the copper wiring pattern, were prepared. First, the nickel-plated surface of the SUS304 plate was layered so as to be brought into contact with the surface of the resin composition layer of the bonding sheet, and laminating was performed under the conditions of 150° C., 0.3 MPa, and 1 m/min to obtain a layered body (SUS plate/resin composition layer/releasable PET film). Then, the releasable PET film was peeled off, and the flexible printed wiring board was bonded to the surface of the exposed resin composition layer by thermal compression bonding for 5 minutes under the conditions of 150° C. and 3 MPa, and then further underwent after-cure at 160° C. for 2 hours in an oven, by which an adhesion test piece B (SUS plate/resin composition layer/flexible printed wiring board) was produced.

[0310] These coverlay film, bonding sheet, and adhesion test pieces A and B were prepared and evaluated in accordance with (i) to (vii) below. The results are shown in Table 2.

[0311] (i) Peel Adhesion Strength (Adhesive Force)

[0312] In order to evaluate the adhesiveness, the 180° peel adhesion strength (N/mm) when the gold-plated copper foil of each adhesion test piece A was peeled off from the polyimide film under the conditions of the temperature of 23° C. and the tensile speed of 50 min/min in accordance with JIS C 6481 (1996) “Test methods of copper-clad laminates for printed. wiring boards” was measured. The width of the adhesion test piece during the measurement was 10 mm.

[0313] (ii) Solder Heat Resistance (Appearance at the Time of Soldering)

[0314] The test was conducted under the following conditions in accordance with JIS C 6481 (1996).

[0315] The adhesion test piece A was floated in a solder bath at 260° C. for 60 seconds with the surface of the polyimide film up, and the presence or absence of appearance abnormalities such as swelling or peeling of the adhesive layer was visually evaluated. As a result, those in which appearance abnormalities such as microvoids, swelling, or peeling were not confirmed were indicated as “A”, those in which slight microvoids were observed were indicated as “B”, and those in which appearance abnormalities such as swelling and peeling were confirmed were indicated as “C”.

[0316] Further, the test piece taken out from the solder bath was measured in terms of 180° peel adhesion strength (N/cm) when the gold-plated copper foil was peeled off from the polyimide film at 23° C. in accordance with HS C 6481 (1996). The width of the adhesion test piece during the measurement was 10 mm, and the tensile speed was 50 min/min,

[0317] (iii) Flame Retardancy

[0318] The coverlay film was heat-cured at 160° C. for 2 hours, and the flame retardancy was evaluated in accordance with UL-94. Those that passed the test (VTM-0 class) were indicated as “A”, and those that failed were indicated as “F”.

[0319] (iv) Conductivity (Connection Resistance)

[0320] The connection resistance value between the SUS plate and the copper foil wiring of the flexible printed wiring board of the adhesion test piece B (SUS plate/resin composition layer/flexible printed wiring board) was measured with a resistance value measuring instrument. As a result, those in which the connection resistance value was less than 0.5Ω were indicated as “A”, those in which the connection resistance value was 0.5Ω or more but less than 1Ω were indicated as “B”, those in which the connection resistance value was 1Ω or more but 3Ω or less were indicated as “C”, and those in which the connection resistance value was more than 3Ω were indicated as “D”.

[0321] (v) Conductivity (Connection Resistance) After Soldering

[0322] The adhesion test piece B was floated in a solder bath at 260° C. for 60 seconds. Thereafter, the connection resistance value between the SUS plate and the copper foil wiring of the flexible printed wiring board of the adhesion test piece B taken out from the solder bath was measured with a resistance value measuring instrument. As a result, those in which the connection resistance value was less than 0.5Ω were indicated as “A”, those in which the connection resistance value was 0.5Ω or more but less than 1Ω were indicated as “B”, those in which the connection resistance value was 1Ω or more but 3Ω or less were indicated as “C”, and those in which the connection resistance value was more than 3Ω were indicated as “D”.

[0323] (vi) Conductivity (Connection Resistance) After Long-Term Reliability Test

[0324] The adhesion test piece B was left in a constant temperature and humidity chamber at 85° C. and 85% RH for 1,000 hours. Thereafter, the connection resistance value between the SUS plate and the copper foil wiring of the flexible printed wiring board of the adhesion test piece B was measured with a resistance value measuring instrument. As a result, those in which the connection resistance value was less than 0.5Ω were indicated as “A”, those in which the connection resistance value was 0.5Ω or more but less than 1Ω were indicated as “B”, those in which the connection resistance value was 1Ω or more but 3Ω or less were indicated as “C”, and those in which the connection resistance value was more than 3Ω were indicated as “D”.

[0325] (viii) Storage Stability of Resin Composition

[0326] Each of the resin compositions of Examples 1 to 20 and Comparative Examples 1 to 3 having the compositions shown in Table 2 was put in a glass bottle, sealed, stored at 5° C. for a predetermined period, and observed in terms of crystallinity of the composition. Those in which gelation of the resin composition or liquid separation was confirmed after storage for the predetermined period were regarded as poor in storage stability and evaluated. Even a resin composition that is evaluated as F can be used without any problem by using it immediately after preparation or by avoiding a long-term storage at low temperature.

[0327] <Evaluation Criteria>

[0328] A: Gelation or liquid separation was not confirmed even after storage for 1 week.

[0329] F: At least one of gelation or liquid separation was confirmed after storage for less than 1 week.

TABLE-US-00002 TABLE 2 Examples 1 2 3 4 5 6 7 8 Composition Polyester a1 50 82 8 50 50 50 50 50 of resin polyurethane a2 — — — — — — — — composition resin (A) a3 — — — — — — — — a4 — — — — — — — — a5 — — — — — — — — a6 — — — — — — — — a7 — — — — — — — — a8 — — — — — — — — Epoxy b1 5 5 5 5 5 5 5 5 resin (B) b2 5 5 5 5 5 5 5 5 Polyamide c1 40 8 82 40 40 40 40 40 resin (C) c2 — — — — — — — — Organic d1 — — — 15 — 45 5 15 filler (D) d2 — — — — 15 — — — Imidazole silane compound (E) 3 3 3 3 3 3 3 — Metal filler (F) 20 20 20 20 20 20 20 20 Carbon black — — — — — — — — Curing promoter 1 1 1 1 1 1 1 1 Flame retardant 5 5 5 5 5 5 5 5 Solvent (mixed solvent) 200 200 200 200 200 200 200 200 Evaluation Peel adhesion Initial 6 5 10 6 6 4 6 4 result strength (N/mm) After soldering 8 7 12 8 8 5 8 6 Appearance at the time of A B A A A A A A soldering (heat resistance) Flame retardancy A A A A A A A A Conductivity Initial B B B A A A B C After soldering B C B A A B B C After storage at 85° C., B C C A B B B C 85% RH, for 1,000 hrs Storage stability A A A A A A A A Examples 9 10 11 12 13 14 15 16 Composition Polyester a1 50 50 — — — — — — of resin polyurethane a2 — — 50 — — — — — composition resin (A) a3 — — — 50 — — — — a4 — — — — 50 — — — a5 — — — — — 50 — — a6 — — — — — — 50 — a7 — — — — — — — 50 a8 — — — — — — — — Epoxy b1 — 5 5 5 5 5 5 5 resin (B) b2 10 5 5 5 5 5 5 5 Polyamide c1 40 40 40 40 40 40 40 40 resin (C) c2 — — — — — — — — Organic d1 15 15 15 15 15 15 15 15 filler (D) d2 — — — — — — — — Imidazole silane compound (E) 3 15 3 3 3 3 3 3 Metal filler (F) 20 20 20 20 20 20 20 20 Carbon black — — — — — — — — Curing promoter 1 1 1 1 1 1 1 1 Flame retardant 5 5 5 5 5 5 5 5 Solvent (mixed solvent) 200 200 200 200 200 200 200 200 Evaluation Peel adhesion Initial 6 6 6 5 7 5 6 6 result strength (N/mm) After soldering 8 8 8 7 9 7 8 8 Appearance at the time of A A A B A A B B soldering (heat resistance) Flame retardancy A A A A A A A A Conductivity Initial B A A C A B C C After soldering B A A C A B C C After storage at 85° C., B A A C C B C C 85% RH, for 1,000 hrs Storage stability A F A A F F A A Comparative Examples Examples 17 18 19 20 21 1 2 3 Composition Polyester a1 — 50 50 50 50 90 — 50 of resin polyurethane a2 — — — — — — — — composition resin (A) a3 — — — — — — — — a4 — — — — — — — — a5 — — — — — — — — a6 — — — — — — — — a7 — — — — — — — — a8 50 — — — — — — — Epoxy b1 5 5 5 5 5 5 5 — resin (B) b2 5 5 5 5 5 5 5 — Polyamide c1 40 40 40 — — — 90 40 resin (C) c2 — — — 40 40 — — — Organic d1 15 — — 15 15 10 10 10 filler (D) d2 — — — — — — — — Imidazole silane compound (E) 3 3 3 — — 3 3 3 Metal filler (F) 20 9 360 20 20 20 20 20 Carbon black — — — — 5 — — — Curing promoter 1 1 1 1 1 1 1 1 Flame retardant 5 5 5 5 5 5 5 5 Solvent (mixed solvent) 200 200 200 200 200 200 200 200 Evaluation Peel adhesion Initial 6 6 3 4 6 2 12 4 result strength (N/mm) After soldering 8 8 5 6 8 3 15 5 Appearance at the time of B A B B A C A C soldering (heat resistance) Flame retardancy A A A A A A A A Conductivity Initial B C B C B D B D After soldering B C B C B D B D After storage at 85° C., B C B C B D D D 85% RH, for 1,000 hrs Storage stability F A F A A A A A

[0330] The unit of the numerical value of each component column in composition of the resin composition shown in Table 2 is parts by mass.

[0331] As is clear from the results shown in Table 2, the resin compositions of Examples 1 to 21 were superior in conductivity compared to the resin compositions of Comparative Examples 1 to 3, even after the long-term storage under environment of high temperature and high humidity.

[0332] Further, Comparative Example 2, which did not contain the polyester polyurethane resin (A), was poor in moist heat resistance. Comparative Example 3, which did not contain the epoxy resin (B), was poor in solder heat resistance and conductivity. Comparative Example 1, which did not contain the polyimide resin (C), was poor particularly in peel strength and was also poor in solder heat resistance and conductivity.

[0333] Further, compared to Example 3, in which the content of the polyester polyurethane resin (A) was 8% by mass, Example 1 or the like, in which the content thereof was 10% by mass or more, was superior in moist heat resistance. Compared to Example 2, in which the content of the polyester polyurethane resin (A) was 82% by mass, Example 1 or the like, in which the content thereof was 70% by mass or less, was superior in peel strength and solder heat resistance

[0334] Further, compared to Examples 1 to 3, which did not contain the organic filler (D), or Example 7, in which the content thereof was less than 5 parts by mass, Example 4 or the like, in which the content of the organic filler (D) was 5 parts by mass or more, was superior in moist heat resistance and conductivity. Compared to Example 6, in which the content of the organic filler (D) was 45 parts by mass, Example 4 or the like, in which the content thereof was 40 parts by mass or less, was superior in peel strength. In particular, the addition of the urethane filler resulted in better affinity with the resin, and superior conductivity and liquid stability.

[0335] Further, compared to Example 8, which did not contain the imidazole silane compound (E), Example 1 or the like, in which the content thereof was 0.1% by mass or more, was superior in peel strength, moist heat resistance, or conductivity. Compared to Example 10, in which the content of the imidazole silane compound (E) was 15% by mass, Example 1 or the like, in which the content thereof was 10% by mass or less, was superior in liquid stability.

[0336] Compared to Example 9, in which only the bisphenol A type epoxy resin was formulated as the epoxy resin (B), Example 1 or the like, which contained both the bisphenol A type epoxy resin and the novolac type epoxy resin, was superior in conductivity.

[0337] Compared to Example 16, which used a7 having a number average molecular weight of 9,000 as the polyester polyurethane resin (A), Example 1 or the like, which used a polyester polyurethane resin (A) having a number average molecular weight of 10,000 or more, was superior in solder heat resistance and moist heat resistance.

[0338] Further, compared to Example 13, which used a4 having a molecular weight per urethane bond in the polyester polyurethane resin (A) of 160, Example 1 or the like, which used one having a molecular weight per urethane bond of from 200 to 8,000, was superior in liquid stability and moist heat resistance. Compared to Example 12, which used a3 having a molecular weight per urethane bond of 10,700, Example 1 or the like was superior in peel strength, solder heat resistance, and conductivity.

[0339] The use of a polyester polyurethane with lower acid value resulted in superior solder heat resistance to the use of a polyester polyurethane with higher acid value.

[0340] Further, compared to Example 18, in which the content of the metal filler (F) was 9 parts by mass, Example 1 or the like, in which the content of the metal filler was from 10 parts by mass to 350 parts by mass, was superior in conductivity.

[0341] Compared to Example 19, in which the content of the metal filler (F) was 360 parts by mass, Example 1 or the like, in which the content of the metal filler was from 10 parts by mass to 350 parts by mass, was superior in liquid stability.

[0342] The disclosure of Japanese Patent Application No. 2019-085255, filed Apr. 26, 2019, is incorporated herein by reference in its entirety.

[0343] All publications, patent applications, and technical standards described in present specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.