ELECTROCONDUCTIVE INK COMPOSITIONS AND ELECTROCONDUCTIVE FILM

Abstract

A conductive ink composition contains a (meth)acrylic polymer (A) and silver particles (B). The (meth)acrylic polymer (A) has a glass transition temperature of 0 C., a weight average molecular weight of 500,000, and a hydroxyl value of more than 50 mgKOH/g. The silver particles (B) have a specific surface area of 0.5 to 3.0 m.sup.2/g, a 50% average particle diameter of 0.5 to 14.0 m, a maximum particle diameter of 8 m, and a solid content from 50 to 80% by mass. Another conductive ink composition contains a (meth)acrylic polymer (A) and carbon black (CB). The (meth)acrylic polymer (A) has a glass transition temperature of 0 C., a weight average molecular weight of 500,000, and a hydroxyl value of more than 50 mgKOH/g. The carbon black (CB) has a specific surface area of 50 m.sup.2/g, an aggregate diameter of 400 nm, and a solid content from 15 to 30% by mass.

Claims

1. A conductive ink composition comprising: a (meth)acrylic polymer (A) and silver particles (B), wherein the (meth)acrylic polymer (A) has a glass transition temperature of 0 C. or less, a weight average molecular weight of 500,000 or more, and a hydroxyl value of more than 50 mgKOH/g, the silver particles (B) have a specific surface area of 0.5 to 3.0 m.sup.2/g, a 50% average particle diameter of 0.5 to 14.0 m, and a maximum particle diameter of 8 m or more, and a solid content is from 50 to 80% by mass.

2. The conductive ink composition according to claim 1, wherein the (meth)acrylic polymer (A) has a glass transition temperature of more than 50 C. and less than 30 C., and a weight average molecular weight of 500,000 to 990,000.

3. The conductive ink composition according to claim 1, wherein a content of a unit (a1) based on a hydroxyl group-containing monomer is from 20 to 40% by mass with respect to all units constituting said (meth)acrylic polymer (A).

4. The conductive ink composition according to claim 1, which has a viscosity at 23 C. of 20 to 50 Pa s.

5. A conductive film obtained by drying a coating film of the conductive ink composition according to claim 1.

6. The conductive film according to claim 5, which is used for an electrode or wiring that requires elasticity in an electronic device.

7. The conductive film according to claim 5, which is used for a detection part, electrode, or wiring of a variable resistance sensor.

8. A conductive ink composition comprising: a (meth)acrylic polymer (A) and carbon black (CB), wherein the (meth)acrylic polymer (A) has a glass transition temperature of 0 C. or less, a weight average molecular weight of 500,000 or more, and a hydroxyl value of more than 50 mgKOH/g, the carbon black (CB) has a specific surface area of 50 ma/g or more and an aggregate diameter of 400 nm or less, and a solid content is from 15 to 30% by mass.

9. The conductive ink composition according to claim 8, wherein the (meth)acrylic polymer (A) has a glass transition temperature of more than 50 C. and less than 30 C., and a weight average molecular weight of 500,000 to 990,000.

10. The conductive ink composition according to claim 8, wherein a content of a unit (a1) based on a hydroxyl group-containing monomer is from 20 to 40% by mass with respect to all units constituting said (meth)acrylic polymer (A).

11. The conductive ink composition according to claim 8, which has a viscosity at 23 C. of 20 to 100 Pa s.

12. A conductive film obtained by drying a coating film of the conductive ink composition according to claim 8.

13. The conductive film according to claim 12, which is used in an electronic device for an electrode or wiring that requires elasticity.

14. The conductive film according to claim 12, which is used for a detection part, electrode, or wiring of a variable resistance sensor.

15. The conductive ink composition according to claim 1, wherein a content of a unit (a2) based on a (meth)acrylate having an alkyl group of 4 to 12 carbon atoms is from 46 to 64% by mass with respect to all units constituting said (meth)acrylic polymer (A).

16. The conductive ink composition according to claim 1, wherein a content of a unit (a3) based on a (meth)acrylate having an alkyl group of 1 to 3 carbon atoms is from 6 to 19% by mass with respect to all units constituting said (meth)acrylic polymer (A).

17. The conductive ink composition according to claim 1, wherein a content of a unit (a4) based on a carboxy group-containing monomer is from 0.05 to 0.35% by mass with respect to all units constituting said (meth)acrylic polymer (A).

18. The conductive ink composition according to claim 8, wherein a content of a unit (a2) based on a (meth)acrylate having an alkyl group of 4 to 12 carbon atoms is from 46 to 64% by mass with respect to all units constituting said (meth)acrylic polymer (A).

19. The conductive ink composition according to claim 8, wherein a content of a unit (a3) based on a (meth)acrylate having an alkyl group of 1 to 3 carbon atoms is from 6 to 19% by mass with respect to all units constituting said (meth)acrylic polymer (A).

20. The conductive ink composition according to claim 8, wherein a content of a unit (a4) based on a carboxy group-containing monomer is from 0.05 to 0.35% by mass with respect to all units constituting said (meth)acrylic polymer (A).

Description

EXAMPLES

[0188] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following description. In the following description, the unit % of the content is % by mass unless otherwise specified.

<Production Example of (Meth)Acrylic Polymer Composition>

[0189] The monomers shown in Tables 1 and 7 are as follows.

[Hydroxyl Group-Containing Monomer (a1)] [0190] 2HPA: 2-hydroxypropyl acrylate [0191] 4HBA: 4-hydroxybutyl acrylate [0192] 2HEA: 2-hydroxyethyl acrylate [0193] 2HEMA: 2-hydroxyethyl methacrylate
[C4-12 Alkyl (Meth)Acrylate (a2)] [0194] BA: butyl acrylate [0195] 2EHA: 2-ethylhexyl acrylate
[C1-3 Alkyl (Meth)Acrylate (a3)] [0196] MA: methyl acrylate [0197] MMA: methyl methacrylate
[Carboxy Group-Containing Monomer (a4)] [0198] AA: acrylic acid
[Other Monomer (a5)] [0199] Vac: vinyl acetate

Production Example 1-1: Production of (Meth)Acrylic Polymer Composition (1-1)

[0200] A (meth)acrylic polymer was synthesized by polymerizing a monomer mixture shown in Table 1 in a polymerization solvent, and a solvent was further added thereto to adjust the solid content concentration to obtain a (meth)acrylic polymer composition.

[0201] More specifically, 29.8 parts by mass of 2HPA, 57.2 parts by mass of BA, 12.8 parts by mass of MA, and 0.2 parts by mass of AA as monomers, and 0.02 parts by mass of 2,2-azobisisobutyronitrile as a polymerization initiator and 43 parts by mass of ethyl acetate as a polymerization solvent were placed in a separable flask. After nitrogen gas was introduced to remove oxygen in the polymerization system, the temperature was raised to 70 C., and the reaction was carried out for 8 hours to obtain a (meth)acrylic polymer A1-1. Ethyl acetate was added thereto to adjust the solid content concentration to 33% by mass to obtain a (meth)acrylic polymer composition (1-1).

[0202] The glass transition temperature, weight average molecular weight, and hydroxyl value of the (meth)acrylic polymer are shown in Table 1 (the same applies hereinafter).

Production Examples 1-2 to 1-5: Production of (Meth)Acrylic Polymer Compositions (1-2) to (1-5)

[0203] The compositions of monomer mixtures were changed as shown in Table 1, and the monomer mixtures were polymerized in the same manner as in Production Example 1 to synthesize (meth)acrylic polymers A1-2 to A1-5. Ethyl acetate was added thereto to adjust the solid content concentrations as shown in Table 1 to obtain (meth)acrylic polymer compositions (1-2) to (1-5).

(Comparative Composition (1-6))

[0204] A polyester resin solution (Nichigo-Polyester LP-035 (product name) manufactured by Mitsubishi Chemical Corporation) was used as a comparative composition (1-6).

[0205] The glass transition temperature, weight average molecular weight, and hydroxyl value of the polyester resin (comparative resin P1-6) in the comparative composition (1-6) are shown in Table 1.

TABLE-US-00001 TABLE 1 Production Production Production Production Production Example Example Example Example Example 1-1 1-2 1-3 1-4 1-5 Monomer (a1) 2HPA 29.8 30.1 mixture 4HBA 0.1 (parts by 2HEA 0.4 mass) 2HEMA 13 (a2) BA 57.2 57.2 35.5 99.3 2EHA 54.9 65.3 (a3) MA 12.8 12.5 MMA 0.9 16.3 (a4) AA 0.2 0.2 2.0 0.3 1.1 (a5) Vac 6.6 4.3 Total 100 100 100 100 100 (Meth)acrylic Glass transition 36 36 57 55 36 20 polymer (A) temperature ( C.) Weight average 700,000 600,000 300,000 1,000,000 350,000 16,000 molecular weight Hydroxyl value 130 130 1 3 50 5 (mgKOH/g) Name of A1-1 A1-2 A1-3 A1-4 A1-5 Comparative (meth)acrylic resin P1-6 polymer Name of (meth)acrylic polymer (1-1) (1-2) (1-3) (1-4) (1-5) Comparative composition composition (1-6) Solid content (%) of (meth)acrylic 33 45 30 30 45 30 polymer composition

<Silver Particles (B)>

[0206] The following silver particles were used. The shape, specific surface area, 50% average particle diameter, and maximum particle diameter of each silver particle are shown in Table 2. [0207] Silver particles (B1): Silbest TC-12 (product name) manufactured by Tokuriki Honten Co., Ltd., flaky particles. [0208] Silver particles (B2): AgC-2011 (product name) manufactured by Fukuda Metal Foil & Powder Co., Ltd., flaky particles. [0209] Silver particles (B3): Silbest TC-725 (product name) manufactured by Tokuriki Honten Co., Ltd., flaky particles. [0210] Silver particles (B4): SLO2 (product name) manufactured by Mitsui Mining & Smelting Co., Ltd., spherical particles. [0211] Silver particles (B5): M612 (product name) manufactured by Tokusen Kogyo Co., Ltd., flaky particles.

<Solvent (C)>

[0212] The following solvents were used. [0213] Solvent (C1-1): diethylene glycol monoethyl ether acetate [0214] Solvent (C1-2): polyoxypropylene 2-ethylhexyl ether derivative (Blaunon EHP-4 (product name) manufactured by Aoki Oil Industrial Co., Ltd.)

<Optional Components>

[0215] The following optional components were used. [0216] Optional component (1-1): binder, terpene phenolic resin (YS Polyster T80 (product name) manufactured by Yasuhara Chemical Co., Ltd.) [0217] Optional component (1-2): ion scavenger (Toagosei IXEPLAS-A2 (product name) manufactured by Toagosei Co., Ltd.)

TABLE-US-00002 TABLE 2 Specific 50% average surface area particle diameter Maximum (m.sup.2/g) (m) particle diameter Silver B1 1.2 to 2.5 1.5 to 3.5 8 m or more particles B2 1.5 to 2.3 1.5 to 3.5 8 m or more (B) B3 2.0 to 4.0 0.5 to 1.5 Less than 8 m B4 2.1 0.29 Less than 8 m B5 0.8 to 1.2 6.0 to 12.0 8 m or more

Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-8

[0218] Silver particles and a solvent were blended into a (meth)acrylic polymer composition according to the proportions shown in Tables 3 to 6. In Example 1-5, the optional component (1-1), silver particles, and a solvent were blended into a (meth)acrylic polymer composition. In Comparative Example 1-4, silver particles and a solvent were blended into the comparative composition (1-6).

[0219] After premixing all the formulation ingredients using a stirrer, the resulting mixture was kneaded using a triple roll mill (BR-150VIII (product name), manufactured by Imex Co., Ltd.) to obtain a conductive ink composition. The kneading was performed under conditions in which a treatment was carried out twice at a rotational frequency of 120 rpm and a distance between the rolls of 40 m, and then a treatment was further carried out twice after reducing the distance between the rolls to 10 m.

[0220] The solid content, the content of the (meth)acrylic polymer (A), and the content of the silver particles (B) with respect to the total mass of the conductive ink composition of each example are shown in the table. Further, the content of the (meth)acrylic polymer (A) and the content of the silver particles (B) with respect to the solid content are shown in the table. The viscosity of the conductive ink composition is shown in the table.

[0221] It should be noted that a blank column in the table means that the formulation ingredient is not blended.

<<Evaluation Method>>

[0222] The obtained conductive film was evaluated using the following method.

[0223] The conductive ink composition obtained in each example was applied onto a base material and dried at 130 C. for 10 minutes to produce a laminate having a conductive film on the base material. An elastic polyurethane sheet (thickness: 100 m) was used as the base material. The dry film thickness of the conductive film was set to approximately 30 m.

[0224] The following properties were evaluated for the obtained conductive film. The results are shown in Tables 3 to 6.

(Measurement of Volume Resistivity)

[0225] Using the laminate obtained in each example as a sample, the volume resistance value (unit: .Math.cm) of the conductive film was measured using a four-terminal electrode of a resistivity meter (Loresta (product name) manufactured by Nittoseiko Analytech Co., Ltd.). The thickness of the conductive film was measured using a microgauge.

(Evaluation of Adhesion)

[0226] Using the laminate obtained in each example as a sample, a peel test was conducted using a cross-cut method based on JIS: K5600-5-6. More specifically, the conductive film of the laminate was cross-cut using a cutter knife so that 100 squares each having a side of 1 mm were formed on the conductive film. Cellotape (registered trademark) was attached to this conductive film and peeled off in the vertical direction, and the degree of peeling of the conductive film was evaluated using the following criteria.

[0227] The case where all 100 squares were not peeled off was evaluated as A, the case where 1 to 99 squares were peeled off was evaluated as B, and the case where all 100 squares were peeled off was evaluated as C.

(Stretching Test)

[0228] A sample was prepared by cutting the laminate obtained in each example into a No. 3 dumbbell shape, and the sample was set in a tensile testing machine. The distance between the marked lines (initial dimension) was set to 20 mm, the sample was stretched under a condition of 23 C. at a tensile speed of 10 mm/min, and the surface resistance value (unit: Q) between the marked lines was measured using a tester (CDM-2000D (product name) manufactured by Custom Corporation) at each specific elongation rate.

[0229] The elongation rate is a value calculated using the following calculation formula.

[00003]$\mathrm{Elongation}\mathrm{rate}\left(\%\right)=\left(\left(\mathrm{distance}\mathrm{between}\mathrm{marked}\mathrm{lines}\mathrm{after}\mathrm{elongation}\left(\mathrm{mm}\right)\right)-\left(\mathrm{initial}\mathrm{dimension}\right)\right)/\left(\mathrm{initial}\mathrm{dimension}\right)100$

[0230] The table shows a surface resistance value R.sup.1 when the elongation rate is 200% (at 200% elongation), that is, when the distance between the marked lines is 60 mm.

[0231] The table also shows a surface resistance value R.sup.2 when the elongation rate is 250% (at 250% elongation), that is, when the distance between the marked lines is 70 mm.

[0232] In addition, the table shows a logarithmic value of the amount of resistance change per 1% of elongation (unit: Q/%) when the elongation rate changes from 0% to 250%, which is calculated using the following formula (3). R.sup.0 in the formula (3) indicates a surface resistance value when the elongation rate is 0% (at 0% elongation).

[0233] The case where a crack or rupture occurred in the film when stretched is indicated as B (not achieved), and the case where the film could be elongated but the electrical conductivity could not be detected is indicated as B (unmeasurable).

[00004]$\begin{array}{cc}\left[\mathrm{Equation}3\right]& \\ \mathrm{Logarithmic}\mathrm{value}\mathrm{of}\mathrm{amount}\mathrm{of}\mathrm{resistance}\mathrm{change}\mathrm{per}1\%\mathrm{of}\mathrm{elongation}={\mathrm{Log}}_{10}\frac{\left(R^2-R^0\right)}{250}& \left(3\right)\end{array}$

(Cyclic Stretching Test)

[0234] A sample was prepared by cutting the laminate obtained in each example into a No. 3 dumbbell shape, and the sample was set in a tensile testing machine. The distance between the marked lines (initial dimension) was set to 20 mm, and cyclic stretching was carried out under conditions at a temperature of 23 C. and a tensile speed of 500 mm/min.

[0235] More specifically, an operation of stretching from the initial dimension at the start (0%, distance between marked lines: 20 mm) to an elongation rate of 100% (distance between marked lines: 40 mm), followed by returning to an elongation rate of 0% (distance between marked lines: 20 mm) was defined as a first cycle; then an operation of stretching from the elongation rate of 0% to an elongation rate of 100%, followed by returning to an elongation rate of 0% was defined as a second cycle; and the operation was carried out until the 100th cycle. The surface resistance value (unit: Q) between the marked lines was measured every 10 cycles using the resistivity meter described above.

[0236] The table shows the surface resistance value at the start (0%), the surface resistance value when stretched by 100% in the first cycle, the surface resistance value when stretched by 100% in the 100th cycle, and the surface resistance value when the elongation rate was returned to 0% after the 100th stretching (0% at the end).

[0237] In addition, the difference in surface resistance value before and after the cyclic stretching test was evaluated. The difference between the surface resistance value at the end (0% elongation) and the surface resistance value at the start (0% elongation) is shown in the table as an absolute value.

[0238] The case where a crack or rupture occurred in the film when stretched in the first stretching or the 100th stretching is indicated as B (not achieved).

TABLE-US-00003 TABLE 3 Ex. 1-1 Ex. 1-2 Ex. 1-3 Ex. 1-4 Proportion of (Meth)acrylic (1-1) 15 10 15 conductive ink polymer (1-2) 10 composition composition (1-3) (% by mass) (1-4) (1-5) Comparative composition (1-6) Silver B1 50 70 50 particles (B) B2 50 B3 B4 B5 Solvent (C) C1-1 35 20 35 40 C1-2 Optional Optional component component 1-1 Optional component 1-2 Total 100 100 100 100 Solid content (% by mass) 54.95 73.3 54.95 54.5 Content of (meth)acrylic polymer (A) (% by mass) 4.95 3.3 4.95 4.5 Content of silver particles (B) (% by mass) 50 70 50 50 (Meth)acrylic polymer (A) / solid content (% by mass) 9.01 4.50 9.01 8.26 Silver particles (B) / solid content (% by mass) 90.99 95.50 90.99 91.74 Viscosity (Pa .Math. s) 28 40 30 23 Evaluation of Volume resistivity ( .Math. cm) .sup.6.0 10.sup.5 .sup.1.3 10.sup.5 .sup.4.8 10.sup.5 .sup.5.6 10.sup.5 conductive Adhesion A A A A film Surface resistance value 11 .sup.8.9 10.sup.1 8.6 24 R.sup.0 () at 0% elongation Surface resistance value 1.5 10.sup.3 7.8 10.sup.2 8.9 10.sup.2 2.0 10.sup.3 R.sup.1 () at 200% elongation Surface resistance value 2.2 10.sup.4 8.2 10.sup.3 1.5 10.sup.4 5.8 10.sup.4 R.sup.2 () at 250% elongation Logarithmic value of amount 2.9 1.5 1.8 3.4 of resistance value change (/%) from 0 to 250% Surface resistance At the start (0%) 11 .sup.8.9 10.sup.1 8.6 24 value () during At the end (0%) 29 15 22 88 cyclic stretching Difference in 18 14 13 64 surface resistance value before and after cyclic stretching 1.sup.st cycle: at 1.5 10.sup.2 7.8 10.sup.1 8.2 10.sup.1 1.3 10.sup.2 100% elongation 100.sup.th cycle: at 4.2 10.sup.3 2.1 10.sup.3 1.5 10.sup.3 6.7 10.sup.3 100% elongation

TABLE-US-00004 TABLE 4 Ex. 1-5 Ex. 1-6 Ex. 1-7 Ex. 1-8 Proportion of (Meth)acrylic (1-1) 15 10 10 15 conductive ink polymer (1-2) composition composition (1-3) (% by mass) (1-4) (1-5) Comparative composition (1-6) Silver B1 60 53 40 particles (B) B2 B3 B4 B5 70 17 18 Solvent (C) C1-1 10 20 20 20 C1-2 10 Optional Optional 5 component component 1-1 Optional 2 component 1-2 Total 100 100 100 100 Solid content (% by mass) 69.95 73.3 73.3 64.95 Content of (meth)acrylic polymer (A) (% by mass) 4.95 3.3 3.3 4.95 Content of silver particles (B) (% by mass) 60 70 70 58 (Meth)acrylic polymer (A) / solid content (% by mass) 7.08 4.50 4.50 7.62 Silver particles (B) / solid content (% by mass) 85.78 95.50 95.50 89.29 Viscosity (Pa .Math. s) 39 31 36 41 Evaluation of Volume resistivity ( .Math. cm) .sup.2.3 10.sup.5 .sup.9.3 10.sup.6 .sup.7.8 10.sup.6 .sup.9.5 10.sup.5 conductive Adhesion A A A A film Surface resistance value 1.2 .sup.7.5 10.sup.1 .sup.5.5 10.sup.1 .sup.8.0 10.sup.1 R.sup.0 () at 0% elongation Surface resistance value 8.2 10.sup.2 8.9 10.sup.2 8.3 10.sup.2 7.6 10.sup.2 R.sup.1 () at 200% elongation Surface resistance value 9.8 10.sup.3 1.7 10.sup.4 1.4 10.sup.4 7.8 10.sup.3 R.sup.2 () at 250% elongation Logarithmic value of amount 1.6 1.8 1.8 1.5 of resistance value change (/%) from 0 to 250% Surface resistance At the start (0%) 1.2 .sup.7.5 10.sup.1 .sup.5.5 10.sup.1 .sup.8.0 10.sup.1 value () during At the end (0%) 20 21 19 19 cyclic stretching Difference in 19 20 18 18 surface resistance value before and after cyclic stretching 1.sup.st cycle: at 8.9 10.sup.1 9.4 10.sup.1 8.9 10.sup.1 9.7 10.sup.1 100% elongation 100.sup.th cycle: at 3.7 10.sup.3 7.7 10.sup.3 4.5 10.sup.3 3.2 10.sup.3 100% elongation

TABLE-US-00005 TABLE 5 Comp. Comp. Comp. Comp. Ex. 1-1 Ex. 1-2 Ex. 1-3 Ex. 1-4 Proportion of (Meth)acrylic (1-1) conductive ink polymer (1-2) composition composition (1-3) 15 (% by mass) (1-4) 15 (1-5) 10 Comparative composition (1-6) 15 Silver B1 50 50 50 50 particles (B) B2 B3 B4 B5 Solvent (C) C1-1 35 35 40 35 C1-2 Optional Optional component component 1-1 Optional component 1-2 Total 100 100 100 100 Solid content (% by mass) 54.5 54.5 54.5 54.5 Content of (meth)acrylic polymer (A) (% by mass) 4.5 4.5 4.5 4.5 Comparative resin Content of silver particles (B) (% by mass) 50 50 50 50 (Meth)acrylic polymer (A) / solid content (% by mass) 8.26 8.26 8.26 8.26 Silver particles (B) / solid content (% by mass) 91.74 91.74 91.74 91.74 Viscosity (Pa .Math. s) 16 37 21 10 Evaluation of Volume resistivity ( .Math. cm) 6.9 10.sup.5 5.3 10.sup.5 4.8 10.sup.5 2.3 10.sup.5 conductive Adhesion B C C C film Surface resistance value 66 41 22 8.6 R.sup.0 () at 0% elongation Surface resistance value B (not B (not B (not B (not R.sup.1 () at 200% elongation achieved) achieved) achieved) achieved) Surface resistance value B (not B (not B (not B (not R.sup.2 () at 250% elongation achieved) achieved) achieved) achieved) Logarithmic value of amount of resistance value change (/%) from 0 to 250% Surface resistance At the start (0%) 66 41 22 8.6 value () during At the end (0%) B (not B (not B (not B (not cyclic stretching achieved) achieved) achieved) achieved) Difference in surface resistance value before and after cyclic stretching 1.sup.st cycle: at 4.5 10.sup.2 9.8 10.sup.2 3.7 10.sup.3 7.3 10.sup.4 100% elongation 100.sup.th cycle: at B (not B (not B (not B (not 100% elongation achieved) achieved) achieved) achieved)

TABLE-US-00006 TABLE 6 Comp. Comp. Comp. Comp. Ex. 1-5 Ex. 1-6 Ex. 1-7 Ex. 1-8 Proportion of (Meth)acrylic (1-1) 15 15 20 10 conductive ink polymer (1-2) composition composition (1-3) (% by mass) (1-4) (1-5) Comparative composition (1-6) Silver B1 35 80 particles (B) B2 B3 50 B4 50 B5 Solvent (C) C1-1 35 35 45 10 C1-2 Optional Optional component component 1-1 Optional component 1-2 Total 100 100 100 100 Solid content (% by mass) 54.95 54.95 41.6 83.3 Content of (meth)acrylic polymer (A) (% by mass) 4.95 4.95 6.6 3.3 Content of silver particles (B) (% by mass) 50 50 35 80 (Meth)acrylic polymer (A) / solid content (% by mass) 9.01 9.01 15.87 3.96 Silver particles (B) / solid content (% by mass) 90.99 90.99 84.13 96.04 Viscosity (Pa .Math. s) 22 30 17 68 Evaluation of Volume resistivity ( .Math. cm) .sup.3.3 10.sup.5 1.2 10.sup.4 6.8 10.sup.4 1.2 10.sup.5 conductive Adhesion A B A C film Surface resistance value 35 78 240 7.5 10.sup.1 R.sup.0 () at 0% elongation Surface resistance value B (not B (not B B (not R.sup.1 () at 200% elongation achieved) achieved) (unmeasurable) achieved) Surface resistance value B (not B (not B B (not R.sup.2 () at 250% elongation achieved) achieved) (unmeasurable) achieved) Logarithmic value of amount of resistance value change (/%) from 0 to 250% Surface resistance At the start (0%) 35 78 240 7.5 10.sup.1 value () during At the end (0%) B (not B (not B (not B (not cyclic stretching achieved) achieved) achieved) achieved) Difference in surface resistance value before and after cyclic stretching 1.sup.st cycle: at 6.9 10.sup.2 1.5 10.sup.3 7.6 10.sup.3 B (not 100% elongation achieved) 100.sup.th cycle: at 1.5 10.sup.4 B (not B B (not 100% elongation achieved) (unmeasurable) achieved)

[0239] As shown in Tables 3 and 4, the conductive films of Examples 1-1 to 1-8 exhibited excellent electrical conductivity and adhesion to the base material, were elastic and exhibited excellent electrical conductivity when stretched, and the electrical conductivity could be detected even at 250% elongation.

[0240] The conductive films of Examples 1-1 to 1-8 also exhibited excellent resistance to cyclic stretching, and the electrical conductivity could be detected both in a stretched state (100%) and in a non-stretched state (0%) even after 100 cycles of repeated stretching at an elongation rate of 100%. Furthermore, the electrical conductivity was excellent in stability when repeatedly stretched, and the difference in surface resistance value before and after the cyclic stretching test was small.

[0241] Further, in Examples 1-1 to 1-8, it was observed that the surface resistance value tended to increase as the elongation rate increased.

[0242] On the other hand, as shown in Tables 5 and 6, in Comparative Examples 1-1 to 1-3 in which the glass transition temperature, weight average molecular weight, or hydroxyl value of the (meth)acrylic polymer (A) was outside the range of the present invention, and in Comparative Example 1-4 in which a comparative resin (polyester) was used in place of the (meth)acrylic polymer (A), a crack or rupture occurred in the film when stretched in the stretching test and the cyclic stretching test.

[0243] In Comparative Example 1-5 in which the maximum particle diameter of the silver particles was too small, a crack or rupture occurred in the film during the stretching test, and the surface resistance value could not be detected at an elongation of 200% or more.

[0244] In Comparative Example 1-6 in which the 50% average particle diameter and maximum particle diameter of the silver particles were too small, a crack or rupture occurred in the film during the stretching test and the cyclic stretching test.

[0245] In Comparative Example 1-7 in which the solid content of the conductive ink composition was too low, it was possible to elongate the conductive film by up to 250% in the stretching test, but the surface resistance value could not be detected. Also in the cyclic stretching test, it was possible to withstand a repeated elongation of 100%100 cycles, but no surface resistance value could be detected.

[0246] In Comparative Example 1-8 in which the solid content of the conductive ink composition was too high, a crack or rupture occurred in the film during the stretching test and the cyclic stretching test.

Production Example 2-1: Production of (Meth)Acrylic Polymer Composition (2-1)

[0247] A (meth)acrylic polymer was synthesized by polymerizing a monomer mixture shown in Table 7 in a polymerization solvent, and a solvent was further added thereto to adjust the solid content concentration to obtain a (meth)acrylic polymer composition.

[0248] More specifically, 29.8 parts by mass of 2HPA, 57.2 parts by mass of BA, 12.8 parts by mass of MA, and 0.2 parts by mass of AA as monomers, and 0.02 parts by mass of 2,2-azobisisobutyronitrile as a polymerization initiator and 43 parts by mass of ethyl acetate as a polymerization solvent were placed in a separable flask. After nitrogen gas was introduced to remove oxygen in the polymerization system, the temperature was raised to 70 C., and the reaction was carried out for 8 hours to obtain a (meth)acrylic polymer A2-1. Ethyl acetate was added thereto to adjust the solid content concentration to 33% by mass to obtain a (meth)acrylic polymer composition (2-1).

[0249] The glass transition temperature, weight average molecular weight, and hydroxyl value of the (meth)acrylic polymer are shown in Table 7 (the same applies hereinafter).

Production Examples 2-2 and 2-3: Production of (Meth)Acrylic Polymer Compositions (2-2) and (2-3)

[0250] The compositions of monomer mixtures were changed as shown in Table 7, and the monomer mixtures were polymerized in the same manner as in Production Example 2-1 to synthesize (meth)acrylic polymers A2-2 and A2-3. Ethyl acetate was added thereto to adjust the solid content concentrations as shown in Table 7 to obtain (meth)acrylic polymer compositions (2-2) and (2-3).

(Comparative Composition (2-4))

[0251] A polyester resin solution (Nichigo-Polyester LP-035 (product name) manufactured by Mitsubishi Chemical Corporation) was used as a comparative composition (2-4).

[0252] The glass transition temperature, weight average molecular weight, and hydroxyl value of the polyester resin (comparative resin P2-4) in the comparative composition (2-4) are shown in Table 7.

[Table 7]

TABLE-US-00007 TABLE 7 Production Production Production Example 2-1 Example 2-2 Example 2-3 Monomer (a1) 2HPA 29.8 mixture (parts 4HBA 0.1 by mass) 2IIEMA 13 (a2) BA 57.2 35.5 2EIIA 54.9 65.3 (a3) MA 12.8 MMA 0.9 16.3 (a4) AA 0.2 2.0 1.1 (a5) Vac 6.6 4.3 Total 100 100 100 (Meth)acrylic Glass transition 36 57 36 20 polymer (A) temperature ( C.) Weight average molecular 700,000 300,000 350,000 16,000 weight Hydroxyl value 130 1 50 5 (mgKOH/g) Name of (meth)acrylic A2-1 A2-2 A2-3 Comparative polymer resin P2-4 Name of (meth)acrylic polymer composition (2-1) (2-2) (2-3) Comparative composition (2-4) Solid content (%) of (meth)acrylic polymer 33 30 45 30 composition indicates data missing or illegible when filed

<Carbon Black (CB)>

[0253] The following (CB) particles were used. Table 8 shows the specific surface area and aggregate diameter of each (CB) particle. [0254] Carbon black (CB1): Ketjen Black EC300J (product name) manufactured by Lion Specialty Chemicals Co., Ltd., furnace black. [0255] Carbon black (CB2): Ensaco 250G (product name) manufactured by Imerys S.A., furnace black. [0256] Carbon black (CB3): Denka Black HS-100 (product name) manufactured by Denka Co., Ltd., acetylene black.

[0257] The following raw materials were used.

<Solvent (C)>

[0258] Solvent (C2-1): diethylene glycol monoethyl ether acetate.

<Graphite Material (D)>

[0259] Graphite (D2-1): BSP-20A (product name) manufactured by Shin-Etsu Kasei Kogyo Co., Ltd., expanded graphite, flaky form, average particle diameter: 20 m.

<Dispersant (E)>

[0260] Dispersant (E2-1): DA-1200 (product name) manufactured by Kusumoto Chemicals, Ltd., high molecular weight unsaturated polycarboxylic acid.

TABLE-US-00008 TABLE 8 Specific surface area (m.sup.2/g) Aggregate diameter (nm) Carbon CB1 780 300 black CB2 61 280 (CB) CB3 38 580

Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-7

[0261] Carbon black, a graphite material, a dispersant, and a solvent were blended into a (meth)acrylic polymer composition according to the proportions shown in Tables 9 to 11. In Comparative Examples 2-3 and 2-4, carbon black, a graphite material, a dispersant, and a solvent were blended into the comparative composition (2-4).

[0262] After premixing all the formulation ingredients using a stirrer, the resulting mixture was kneaded using a triple roll mill (BR-150VIII (product name), manufactured by Imex Co., Ltd.) to obtain a conductive ink composition. The kneading was performed under conditions in which a treatment was carried out twice at a rotational frequency of 120 rpm and a distance between the rolls of 40 m, and then a treatment was further carried out twice after reducing the distance between the rolls to 10 m.

[0263] The solid content, the content of the (meth)acrylic polymer (A), and the content of the carbon black (CB) with respect to the total mass of the conductive ink composition of each example are shown in the table. Further, the content of the (meth)acrylic polymer (A), the content of the carbon black (CB), and the content of the graphite material (D) with respect to the solid content are shown in the table. The viscosity of the conductive ink composition is shown in the table.

[0264] It should be noted that a blank column in the table means that the formulation ingredient is not blended.

<<Evaluation Method>>

[0265] The obtained conductive film was evaluated using the following method.

[0266] The conductive ink composition obtained in each example was applied onto a base material and dried at 130 C. for 10 minutes to produce a laminate having a conductive film on the base material. An elastic polyurethane sheet (thickness: 100 m) was used as the base material. The dry film thickness of the conductive film was set to approximately 30 m.

[0267] The following properties were evaluated for the obtained conductive film. The results are shown in Tables 9 to 11.

(Measurement of Volume Resistivity)

[0268] The volume resistivity was measured in the same manner as in Example 1-1 described above.

(Evaluation of Adhesion)

[0269] The adhesion was evaluated in the same manner as in Example 1-1 described above.

(Stretching Test (1))

[0270] A sample was prepared by cutting the laminate obtained in each example into a No. 3 dumbbell shape, and the sample was set in a tensile testing machine. The distance between the marked lines (initial dimension) was set to 20 mm, the sample was stretched under a condition of 23 C. at a tensile speed of 10 mm/min, and the surface resistance value (unit: Q) between the marked lines was measured using a tester (CDM-2000D (product name) manufactured by Custom Corporation) at each specific elongation rate.

[0271] The elongation rate is a value calculated using the following calculation formula.

Elongation rate (%) ((distance between marked lines after elongation (mm))(initial dimension))/(initial dimension)100

[0272] The table shows a surface resistance value R.sup.1 when the elongation rate is 200% (at 200% elongation), that is, when the distance between the marked lines is 60 mm.

[0273] The table also shows a surface resistance value R.sup.2 when the elongation rate is 300% (at 300% elongation), that is, when the distance between the marked lines is 80 mm.

[0274] In addition, the table shows a logarithmic value of the amount of resistance change per 1% of elongation (unit: Q/%) when the elongation rate changes from 0% to 300%, which is calculated using the following formula (4). R.sup.0 in the formula (4) indicates a surface resistance value when the elongation rate is 0% (at 0% elongation).

[0275] The case where a crack or rupture occurred in the film when stretched is indicated as B (not achieved), and the case where the film could be elongated but the electrical conductivity could not be detected is indicated as B (unmeasurable).

[00005]$\begin{array}{cc}\left[\mathrm{Equation}4\right]& \\ \mathrm{Logarithmic}\mathrm{value}\mathrm{of}\mathrm{amount}\mathrm{of}\mathrm{resistance}\mathrm{change}\mathrm{per}1\%\mathrm{of}\mathrm{elongation}={\mathrm{Log}}_{10}\frac{\left(R^2-R^0\right)}{300}& \left(4\right)\end{array}$

(Stretching Test (2))

[0276] Using the same measurement method as in the stretching test (1), the surface resistance value (unit: Q) was measured by increasing the elongation rate in a stepwise manner. The elongation rate was increased by 25% each time from 50% to 100%, and increased by 50% each time when it exceeded 100%. The maximum value of the elongation rate for which the surface resistance value could be measured within a detectable range of the measuring device (1.010.sup.7 or less) was recorded as the maximum value of the elongation rate (unit: %) at 1.010.sup.7 or less.

(Cyclic Stretching Test)

[0277] A cyclic stretching test was carried out in the same manner as in Example 1-1 described above, and the properties shown in the table were evaluated.

TABLE-US-00009 TABLE 9 Ex. 2-1 Ex. 2-2 Ex. 2-3 Ex. 2-4 Ex. 2-5 Proportion of (Meth)acrylic (2-1) 30 30 40 30 40 conductive ink polymer (2-2) composition composition (2-3) (% by mass) Comparative composition (2-4) Carbon black CB1 8 5 5 (CB) CB2 8 8 CB3 Graphite Graphite D2-1 5 5 5 material (D) Solvent (C) C2-1 54 52 42 49 44 Dispersant (E) E2-1 8 8 8 8 8 Total 100 100 100 100 100 Solid content (% by mass) 17.9 19.9 23.2 22.9 21.2 Content of (meth)acrylic polymer (A) (% by mass) 9.9 9.9 13.2 9.9 13.2 Content of carbon black (CB) (% by mass) 8 5 5 8 8 (Meth)acrylic polymer (A) / solid content (% by mass) 55.31 49.75 56.90 43.23 62.26 Carbon black (CB) / solid content (% by mass) 44.69 25.13 21.55 34.93 37.73 Graphite material (D) / solid content (% by mass) 0 25.13 21.55 21.83 0.00 Viscosity (Pa .Math. s) 96 72 81 25 21 Evaluation of Volume resistivity ( .Math. cm) .sup.2.4 10.sup.1 .sup.3.4 10.sup.2 .sup.8.9 10.sup.2 .sup.4.8 10.sup.2 .sup.6.8 10.sup.1 conductive Adhesion A A A A A film Surface resistance value 8.5 10.sup.3 1.2 10.sup.3 2.5 10.sup.3 4.6 10.sup.3 9.6 10.sup.3 R.sup.0 () at 0% elongation Surface resistance value 8.5 10.sup.4 4.5 10.sup.4 9.8 10.sup.4 1.3 10.sup.5 2.3 10.sup.5 R.sup.1 () at 200% elongation Surface resistance value 4.6 10.sup.6 7.8 10.sup.6 2.5 10.sup.6 1.3 10.sup.6 5.3 10.sup.6 R.sup.2 () at 300% elongation Logarithmic value of amount 4.2 4.4 3.9 3.6 4.2 of resistance value change (/%) from 0 to 300% Maximum value of elongation rate 400 350 400 450 450 (%) at 1.0 10.sup.7 or less Surface resistance At the start (0%) 8.5 10.sup.3 1.2 10.sup.3 2.5 10.sup.3 4.6 10.sup.3 9.6 10.sup.3 value () during At the end (0%) 2.8 10.sup.4 1.7 10.sup.3 3.5 10.sup.3 5.3 10.sup.3 2.3 10.sup.4 cyclic stretching Difference in 2.0 10.sup.4 5.0 10.sup.2 1.0 10.sup.3 7.0 10.sup.2 1.3 10.sup.4 surface resistance value before and after cyclic stretching 1.sup.st cycle: at 5.6 10.sup.4 2.0 10.sup.4 3.4 10.sup.4 2.4 10.sup.4 7.1 10.sup.4 100% elongation 100.sup.th cycle: at 1.0 10.sup.5 5.7 10.sup.4 6.6 10.sup.4 6.2 10.sup.4 9.2 10.sup.4 100% elongation

TABLE-US-00010 TABLE 10 Comp. Comp. Comp. Comp. Ex. 2-1 Ex. 2-2 Ex. 2-3 Ex. 2-4 Proportion of (Meth)acrylic (2-1) conductive ink polymer (2-2) 30 composition composition (2-3) 20 (% by mass) Comparative composition (2-4) 30 50 Carbon black CB1 8 8 8 5 (CB) CB2 CB3 Graphite Graphite 10 material (D) D2-1 Solvent (C) C2-1 54 64 54 27 Dispersant (E) E2-1 8 8 8 8 Total 100 100 100 100 Solid content (% by mass) 17.0 17.0 17.0 30.0 Content of (meth)acrylic polymer (A) (% by mass) 9.0 9.0 9.0 15.0 Comparative Comparative resin resin Content of carbon black (CB) (% by mass) 8 8 8 5 (Meth)acrylic polymer (A) / solid content (% by mass) 52.94 52.94 52.94 50.00 Carbon black (CB) / solid content (% by mass) 47.06 47.06 47.06 16.67 Graphite material (D) / solid content (% by mass) 0 0 0 33.33 Viscosity (Pa .Math. s) 82 64 38 33 Evaluation of Volume resistivity ( .Math. cm) 1.8 10.sup.1 2.3 10.sup.1 1.5 10.sup.1 2.2 10.sup.2 conductive Adhesion C C C C film Surface resistance value 2.6 10.sup.3 7.5 10.sup.4 9.4 10.sup.2 7.6 10.sup.2 R.sup.0 () at 0% elongation Surface resistance value 8.8 10.sup.6 B (not B (not B (not R.sup.1 () at 200% elongation achieved) achieved) achieved) Surface resistance value B (not B (not B (not B (not R.sup.2 () at 300% elongation achieved) achieved) achieved) achieved) Logarithmic value of amount of resistance value change (/%) from 0 to 300% Maximum value of elongation 250 100 75 75 rate (%) at 1.0 10.sup.7 or less Surface resistance At the start (0%) 2.6 10.sup.3 7.5 10.sup.4 9.4 10.sup.2 7.6 10.sup.2 value () during At the end (0%) B (not B (not B (not B (not cyclic stretching achieved) achieved) achieved) achieved) Difference in surface resistance value before and after cyclic stretching 1.sup.st cycle: at 3.7 10.sup.4 8.1 10.sup.6 B (not B (not 100% elongation achieved) achieved) 100.sup.th cycle: at B (not B (not B (not B (not 100% elongation achieved) achieved) achieved) achieved)

TABLE-US-00011 TABLE 11 Comp. Comp. Comp. Ex. 2-5 Ex. 2-6 Ex. 2-7 Proportion of (Meth)acrylic polymer (2-1) 15 50 30 conductive ink composition (2-2) composition (2-3) (% by mass) Comparative composition (2-4) Carbon black (CB) CB1 3 10 CB2 CB3 5 Graphite material (D) Graphite D2-1 5 10 5 Solvent (C) C2-1 72 22 52 Dispersant (E) E2-1 5 8 8 Total 100 100 100 Solid content (% by mass) 12.95 36.5 19.9 Content of (meth)acrylic polymer (A) (% by mass) 4.95 16.5 9.9 Content of carbon black (CB) (% by mass) 3 10 5 (Meth)acrylic polymer (A)/solid content (% by mass) 38.22 45.21 49.75 Carbon black (CB)/solid content (% by mass) 23.17 27.40 25.13 Graphite material (D)/solid content (% by mass) 38.61 27.40 25.13 Viscosity (Pa .Math. s) 66 100 24 Evaluation of Volume resistivity ( .Math. cm) .sup.8.9 10.sup.1 .sup.1.3 10.sup.2 .sup.4.4 10.sup.1 conductive Adhesion A C B film Surface resistance value R.sup.0 () at 0% elongation 1.2 10.sup.4 1.4 10.sup.3 3.3 10.sup.4 Surface resistance value R.sup.1 () at 200% elongation 7.7 10.sup.5 B (not 9.2 10.sup.6 achieved) Surface resistance value R.sup.2 () at 300% elongation B (not B (not B (not achieved) achieved) achieved) Logarithmic value of amount of resistance value change (/%) from 0 to 300% Maximum value of elongation rate (%) at 1.0 10.sup.7 275 75 200 or less Surface resistance At the start (0%) 1.2 10.sup.4 1.4 10.sup.3 3.3 10.sup.4 value () during cyclic stretching At the end (0%) B (not B (not B (not achieved) achieved) achieved) Difference in surface resistance value before and after cyclic stretching 1.sup.st cycle: at 100% 2.5 10.sup.5 B (not 7.8 10.sup.5 elongation achieved) 100.sup.th cycle: at 100% B (not B (not B (not elongation achieved) achieved) achieved)

[0278] As shown in Table 9, the conductive films of Examples 2-1 to 2-5 exhibited excellent electrical conductivity and adhesion to the base material. In addition, they were elastic and exhibited excellent electrical conductivity when stretched, the electrical conductivity was detectable even at 300% elongation, and the maximum value of the elongation rate was large at 1.010.sup.7 or less.

[0279] The conductive films of Examples 2-1 to 2-5 also exhibited excellent resistance to cyclic stretching, and the electrical conductivity could be detected both in a stretched state (100%) and in a non-stretched state (0%) even after 100 cycles of repeated stretching at an elongation rate of 100%. Furthermore, the electrical conductivity was excellent in stability when repeatedly stretched, and the difference in surface resistance value before and after the cyclic stretching test was small.

[0280] Further, in Examples 2-1 to 2-5, it was observed that the surface resistance value tended to increase as the elongation rate increased.

[0281] On the other hand, as shown in Tables 10 and 11, in Comparative Examples 2-1 and 2-2 in which the weight average molecular weight or hydroxyl value of the (meth)acrylic polymer (A) was outside the range of the present invention, and in Comparative Examples 2-3 and 2-4 in which a comparative resin (polyester) was used in place of the (meth)acrylic polymer (A), a crack or rupture occurred in the film when stretched in the stretching test and the cyclic stretching test.

[0282] In Comparative Example 2-5 in which the solid content of the conductive ink composition was too low, and in Comparative Example 2-6 in which the solid content was too high, a crack or rupture occurred in the film during the stretching test and the cyclic stretching test.

[0283] In Comparative Example 2-7 in which the specific surface area of carbon black (CB) was small and the aggregate diameter was large, a crack or rupture occurred in the film during the stretching test and the cyclic stretching test.