JP3299083B2 - Method for producing carbon-based conductive paste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermosetting carbon-based conductive paste for forming a conductive circuit comprising a carbon film on a printed circuit board.

[0002]

2. Description of the Related Art A conductive paste is applied to the inner surface of a housing forming member of a printed wiring board or an electronic device, and is cured by heat or an electron beam to form a film. A technique for forming a conductive film is known. In such conductive paste,
Some of the conductive particles use metal powder such as silver or copper, and some use carbonaceous powder such as graphite or carbon black. Sheet resistance is about 0.1 to 1 Ω / □, but in the case of silver powder, migration may occur depending on the usage environment.
In the case of copper powder, there is a concern that the resistance value may change due to oxidation.

On the other hand, a carbon-based conductive paste containing carbonaceous powder as conductive particles uses a carbonaceous powder such as graphite or carbon black alone or in combination with a phenolic resin, an epoxy resin, or an alkyd resin. Along with a binder and dispersant made of a curable resin such as, kneaded in a cellosolve or carbitol-based organic solvent,
It is dispersed. As the dispersant, thermoplastic natural or synthetic polymer materials such as ethyl cellulose, nitrocellulose, hydroxycellulose, polyvinyl butyral, and polyvinyl acetate are used, and silane-based, titanate-based, alumina-based coupling agents, and nonionic-based dispersants are used. A technique for improving dispersibility by adding a surfactant is known. This carbon-based conductive paste is
A carbon coating printed on a printed wiring board made of paper phenol or glass epoxy by a screen printing method and subjected to a curing treatment is used for a key contact or a slide switch of a printed circuit board. These applications utilize the sliding characteristics of the graphite contained.

The average thickness (film thickness) of a carbon film formed on a printed wiring board by a screen printing method is about 2
The sheet resistance value representing the electric conductivity of the film is 20 to 50 Ω / □, that is, the specific resistance value is 0.04 to 0.1.
It is about Ωcm, electrical conductivity is inferior to the above-mentioned metal-based powder coating, but due to the properties of carbon-based conductive particles, migration that occurs when silver is used as conductive particles, and when copper is used. There is no concern about a change in the resistance value due to the generated oxidation, and the conductive property is stable. For this reason, methods for lowering the resistance value of a conductive film made of a carbon-based conductive paste have been studied for a long time. For example, Japanese Patent Application Laid-Open No. 60-30102 discloses a method using expanded graphite as conductive particles. . Also, Japanese Patent Application Laid-Open No.
No. 36343 discloses a method using carbon black having high conductivity.

[0005]

However, expanded graphite has an extremely low bulk density of 0.03 to 0.2 g / cm ^3, and it is difficult to handle powder such as material mixing and transportation. In addition, an extremely large amount of solvent is required to make a paint (paste) into a paste viscosity suitable for screen printing. Here, as a solvent, a cellosolve or carbitol-based organic solvent is mainly used. When screen printing is performed on a printed wiring board with a paste using a large amount of a solvent as described above, the coating film has a rough surface, and the heat-cured carbon coating causes powder dropout. The powder drop is a phenomenon in which a part of particles are peeled off from the surface of the coating film, and there is a possibility that unnecessary conduction may occur between insulating portions. Further, in a printed pattern after screen printing, bleeding occurs at an end of a desired pattern, and it is difficult to form a practical carbon film for forming a circuit. In addition, since a strong acid is used in the production process of the expanded graphite, the remaining acid may attack the copper foil on the printed wiring board, and in order to prevent this, at a high temperature before forming the expanded graphite alone into a paint. Heat treatment needs to be performed.

On the other hand, carbon black having a large specific surface area is known to exhibit high conductivity. However, such carbon black generally has a low binding force with a curable resin as a binder, and is hardened. This causes cracks in the coating. As a result, the electric resistance value of the conductive film increases.
Further, since an excess solvent is required to adjust the paste viscosity to be suitable for screen printing, the actual effective solid content in the paste is low, and the film thickness of the obtained film is small, so that the electric power of the wiring portion is reduced. The resistance value increases. As a countermeasure, it is conceivable to increase the ratio of the conductive particles to the thermosetting resin as a binder, but as a result, although the resistance value is slightly decreased, the amount of the binder is relatively insufficient. In addition, problems such as a decrease in the adhesion of the coating film to the printed wiring board and the generation of cracks in the coating film due to a change in thermal expansion during soldering in consideration of the mounting process occur.

An object of the present invention is to provide a method for producing a carbon-based conductive paste capable of obtaining a carbon film having improved electric conductivity by utilizing the stability of the carbonaceous powder as described above. .

[0008]

Means for Solving the Problems In view of the above problems, the present inventors have made intensive studies and, as a result, have completed the present invention. That is, the present invention relates to a resol type phenol resin dissolved in an organic solvent, a carbonaceous powder comprising carbon black and natural flaky graphite having an average particle diameter of 10 to 20 μm, polyvinyl butyral and a titanate coupling agent. In a method for producing a carbon-based conductive paste to be kneaded and dispersed together with dibutyl phthalate (hereinafter referred to as "DBP"), the oil absorption is 100 g.
Per liter of carbon black, and the titanate-based coupling agent
8 to 12 parts by weight per 100 parts by weight of carbon black
Is to provide a method for producing a carbon-based conductive paste, characterized in that the pressure. Further, in the above production method, (a) the weight-average molecular weight of the resol-type phenol resin is 1100 to 1530, and (b) the compounding amount of the natural flaky graphite and carbon black of the carbonaceous powder is 50 by weight. : 50-70: 30, and (c) the effective solid content of the carbonaceous powder and the resol-type phenolic resin is 50: 50-60: 40 by weight.
(D) mixing the polyvinyl butyral with the carbonaceous powder 10
There is provided a method for producing a carbon-based conductive paste, wherein 2-6 parts by weight added pressure to Rukoto by 0 part by weight.

According to the present invention, the carbon black has a DBP oil absorption of 115 to 170 cc per 100 g, which is a physical property indicating a specific surface area and a structural state (structure).
Of carbon black and natural flaky graphite having good electrical conductivity, in a predetermined blending ratio, in a resole phenolic resin of a specific molecular weight, polyvinyl butyral as a dispersant, a specific amount of a titanate coupling agent and This is a method for producing a carbon-based conductive paste which is kneaded with an organic solvent and dispersed to form a paste. The electrical conductivity of the carbon coating formed by the paste prepared by the production method of the present invention is good, and is expressed as a sheet resistance value by about 1/4 to 1/3 as compared with the coating obtained from the conventional carbon-based conductive paste. And shows a value of 10Ω / □ or less.

The DB of carbon black used in the present invention
P oil absorption is 115-170cc per 100g,
Preferably, it is 129 to 155 cc. When carbon black having a DBP oil absorption of more than 170 cc per 100 g is used, 50% by weight or more of an organic solvent is required in the paste as described above. In a coating film formed by such a paste, a rapid evaporation of an organic solvent occurs during a thermosetting process after printing, and a sufficient coating with a thermosetting binder is not performed because the specific surface area of carbon black is extremely large. As a result, the binding force decreases, and cracks occur in the coating. As a result, the electrical resistance of the coating increases, and the adhesion between the coating and the printed wiring board decreases. On the other hand, in the case of carbon black having a DBP oil absorption of less than 115 cc per 100 g, the number of contact points for electrical conduction in the coating becomes insufficient because the structure is immature, and the contact resistance becomes high. Can not get a good one.

Furthermore, from the viewpoint of preventing clogging of the screen mask, it is general that the maximum particle diameter of graphite, which is the other conductive particle, is 100 μm or less. The average particle size of the graphite used in the present invention is 10 to 20 μm.
m, preferably 12 to 18 μm, particularly preferably 14 to
16 μm. If the particle diameter is less than 10 μm, the particles are too fine, the contact resistance increases, and the electric resistance increases. Conversely, if the particle size is larger than 20 μm, the particles are too coarse,
The surface of the formed film becomes rough. In the case of a film having a large surface roughness, powder falling easily occurs, which may cause unnecessary conduction between insulating portions, which is a problem.

[0012] The weight average molecular weight of the resole type phenol resin is also a factor that affects the electric conductivity of the resulting coating. The weight average molecular weight of the resol type phenol resin used in the method of the present invention is 1100 to 1530, and the larger the molecular weight, the more preferable. If the weight average molecular weight is less than 1100, the resin coats the conductive particles because of high wettability between the phenolic resin and the conductive particles. The electric resistance increases. Furthermore, due to the large shrinkage stress at the time of thermal curing of the coating film, the adhesion of the formed coating film to the substrate is reduced, and when exposed to a high temperature atmosphere such as soldering in consideration of the mounting process on the printed circuit board, The change in the resistance value of the coating increases. Resins having a weight average molecular weight of more than 1530 are generally not available at present,
This was the upper limit.

The blending amount of natural flaky graphite and carbon black exhibiting a specific DBP oil absorption of the carbonaceous powder is 50:50 to 70:30, preferably 55:45 in weight ratio.
65:35, particularly preferably 58:42 to 62:38. The particle size of carbon black is about 1/1000 to 1/100 of that of natural flaky graphite, and carbon black is filled in the carbon coating so as to fill gaps between natural flaky graphite, thereby improving electric conductivity. Works.
Here, if the proportion of carbon black in the carbonaceous powder exceeds 50% by weight, a large number of fine conductive particles are present, the contact resistance increases, and the electrical conductivity of the formed film decreases. Also, when the content is less than 30% by weight, the gap between the graphite particles cannot be sufficiently filled with carbon black, so that the contact state between the conductive particles becomes insufficient and the electric conductivity decreases.

The resol-type phenol resin is handled as a liquid in which the above-mentioned resol-type phenol resin having a specific weight average molecular weight is dissolved in a cellosolve or carbitol-based organic solvent of the same kind as the organic solvent for forming the paste. For this reason, in order to mix an accurate amount of phenol resin, it is necessary to represent the solid content of the actual phenol resin in the liquid, that is, the “effective solid content”. In the present invention, the compounding amount of the carbonaceous powder and the effective solid content of the resol-type phenol resin is 50:50 to 60:40 by weight ratio, preferably 55: 4.
5:60:40, particularly preferably 57:43 to 60: 4
Set to 0. When the compounding amount of the effective solid content of the phenolic resin exceeds 50% by weight based on the carbonaceous powder, the amount of the resin covering the carbonaceous powder of the conductive particles increases. Since the phenol resin is an insulator, when formed into a film, the electrical conductivity between the conductive particles decreases, and the electrical resistance increases. On the other hand, if the blending amount of the phenolic resin is less than 40% by weight, the binding force between the conductive particles is reduced, the contact state of the conductive particles becomes insufficient, and a material having good electric conductivity cannot be obtained. Further, the adhesion of the carbon film to the printed wiring board is deteriorated.

Even if the specifications of the above-mentioned conductive particles, phenolic resin and the like and the amounts thereof are the same, the electric conductivity of the film changes depending on the dispersion state of the conductive particles in the paste. That is, when the paste in which the conductive particles are agglomerated and the paste in which the conductive particles are agglomerated are compared with each other when they are formed into a film, the film formed by the paste in which the conductive particles are agglomerated has a higher resistance value, and the mounting process is taken into consideration. The change in resistance value due to the applied heat history becomes large. Therefore, the better the dispersed state of the conductive particles in the paint (paste), the lower the resistance value of the coating film, which is preferable.

The present invention is characterized in that the amount of polyvinyl butyral, which is a dispersant for the carbon-based conductive paste, is 2 to 6 parts by weight based on 100 parts by weight of the carbonaceous powder. If the amount of the dispersant is less than 2 parts by weight, a good dispersion state cannot be obtained. On the other hand, if the amount exceeds 6 parts by weight, the dispersion state does not become better, and the insulating component increases. Therefore, the object of the present invention cannot be achieved.

In the present invention, the titanate coupling agent is added in an amount of 8 to 12 parts by weight based on 100 parts by weight of the carbon black having the specific DBP oil absorption. If the amount is less than 8 parts by weight, good dispersibility cannot be achieved, and if it exceeds 12 parts by weight, no change in the dispersibility is observed, and the adhesion of the coating to the substrate is extremely reduced. The titanate-based coupling agent forms a compound of titanium and carbon by thermal denaturation and solidifies. However, the boiling point of each coupling agent exceeds 200 ° C, and is limited at a temperature of about 150 ° C for forming a carbon film. Only a given amount is thermally denatured. Therefore, when the amount of the coupling agent added is increased, the coupling agent remains in a liquid state in the coating, and the adhesion of the carbon coating to the printed wiring board decreases.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In a resol type phenol resin dissolved in an organic solvent, dibutyl phthalate oil absorption is 115
~ 170cc carbon black and average particle size is 10 ~
Carbonaceous powder consisting of 20 μm natural flaky graphite,
By kneading and dispersing together with a dispersing agent polyvinyl butyral and a titanate coupling agent,
A carbon-based conductive paste capable of forming a carbon coating excellent in stability and electrical conductivity is manufactured.

[0019]

Next, the present invention will be described in more detail with reference to Examples. <Example 1> (Examples 1 to 4, Comparative Samples 1 to 3) Dependence of carbon black on DBP oil absorption (adjustment of paste) Natural scaly particles having an average particle diameter of 16 µm (particle diameter range of 2 to 85 µm) Graphite (trade name: BF-1
6A, manufactured by Chuetsu Graphite Co., Ltd.), carbon black and resole type phenol resin, and polyvinyl butyral (trade name: Esrec BH-S, Sekisui Chemical Co., Ltd.) as a dispersant.
) And a titanate-based coupling agent (trade name: Plenact KR9SA, manufactured by Ajinomoto Co., Ltd.) in the following mixing ratio, butyl cellosolve as an organic solvent is appropriately added and mixed with a raikai machine, and then kneaded with a three-roll mill. did. Finally, butyl cellosolve was added to adjust the viscosity of the paste, thereby producing a carbon-based conductive paste. The weight average molecular weight of the above-mentioned resol-type phenol resin is 1460. Combination component weight part graphite 60 carbon black 40 resole type phenolic resin (as solid) 67 polyvinyl butyral resin 4 titanate coupling agent 4 butyl cellosolve suitable (preparation of carbon coating) Made of steel wire, emulsion thickness 20μm
1 mm wide and 10 mm long on a paper phenolic printed wiring board using a 200 mesh screen mask
The wiring pattern was screen-printed and subjected to a thermosetting treatment at 150 ° C. for 15 minutes to form a carbon film. (Evaluation of sample) The electric resistance value of the coating film obtained as described above was measured with a digital multimeter, the coating film thickness was measured with a surface roughness meter, and the film thickness of 20 μm was calculated using the following formula [I]. The sheet resistance (Ω / □) at that time was determined.

(Equation 1) Here, R is the resistance value (Ω) of the wiring portion, and w is the coating film width (m).
m) and t indicate the coating thickness (μm), and 1 indicates the coating length (mm). The adhesion of the coating to the substrate was evaluated by forming a carbon coating on a copper foil, immersing the substrate in a solder bath (composition Sn-40Pb) at 260 ° C. for 10 seconds, and allowing the cellophane tape to cool. It was adhered and the presence or absence of peeling of the carbon film was confirmed. Table 1 shows the specifications of the seven carbon blacks used in the test and the characteristics of the carbon coatings obtained from the various pastes. In addition, there were four points in Examples and three points in Comparative Examples.

[0020]

[Table 1]

Samples 1 to 4 having a DBP oil absorption within the range of the present invention have good electric conductivity of not more than 10 Ω / □ and good adhesion to the substrate. Above all, DBP oil absorption is 129-155cc / 100g
(Samples 2 and 3) are particularly excellent in electric conductivity. On the other hand, Comparative Sample 1 having a low DBP oil absorption had a sheet resistance value of 30Ω / □, and had the same electrical conductivity as a carbon film formed by a conventional carbon-based conductive paste. This is considered to be because the contact between the conductive particles is not sufficient because the structure has not been sufficiently developed. On the other hand, among Comparative Samples 2 and 3 having a DBP oil absorption exceeding the range of the present invention, Comparative Sample 2 having a DBP oil absorption of 210 cc / 100 g has good adhesion, but has a low binding force due to a binder. Has a high contact resistance, and no good electrical conductivity can be obtained. Further, Comparative Sample 3 having a high DBP oil absorption and 360 cc / 100 g had poor adhesion due to poor adhesion. In addition, the amount of butyl cellosolve used as a solvent during the formation of the paste is 50 to 60% by weight of the paste.
After printing, bleeding was observed at the edge of the wiring pattern.

Example 2 (Samples 5 to 7, Comparative Samples 4 and 5) The dependence of the resole type phenolic resin on the weight average molecular weight will be examined. Note that carbon black having a DBP oil absorption of 129 cc / 100 g was used. The amount of each material used for making the paste was the same as in Example 1. Table 2 shows the specifications of the five resole phenolic resins used in the test and the properties of the carbon coatings obtained from the various pastes. Here, the number of working samples was three, and the number of comparative samples was two.
Is a point.

[0023]

[Table 2]

Samples 5 to 7 in which the weight average molecular weight of the resole type phenol resin is in the range of the present invention have a good electric conductivity of 10 Ω / □ or less and a good adhesion to the substrate. It is. Among them, 1460 having the highest weight average molecular weight (sample 7) is particularly excellent in electric conductivity. On the other hand, in Comparative Samples 4 and 5, in which the weight average molecular weight of the resol-type phenolic resin is low, the wettability of the resin to the carbonaceous powder as the conductive particles is high, and the resin coats the surface of the carbonaceous powder. Good electrical conductivity cannot be obtained. In addition, the adhesiveness of the coating to the printed wiring board is poor due to the large shrinkage stress during thermosetting.

<Example 3> (Examples 8 to 10, Comparative Examples 6 and 7) The dependence of the weight ratio of graphite and carbon black in the carbonaceous powder will be examined. In addition, natural flaky graphite (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.) having an average particle diameter of 16 μm (particle diameter range: 2 to 85 μm) is used as graphite, and DBP oil absorption is 129 cc / 100 as carbon black.
g, the total amount of the carbonaceous powder was 100 parts by weight, and the blending of other materials was the same as in Example 1. Five types of carbon powder were used for the test, of which three were for the working sample and two for the comparative sample. Table 3 shows these characteristics.

[0026]

[Table 3]

Samples 8 to 10 in which the weight ratio of graphite to carbon black in the carbonaceous powder is within the range of the present invention.
Has good electrical conductivity with a sheet resistance value of 10 Ω / □ or less, and has good adhesion to a printed wiring board. In particular, the weight ratio of graphite to carbon black is 6
The sample having a ratio of 0:40 (sample 9) is particularly excellent in electric conductivity. On the other hand, the electric conductivity of the film of Comparative Sample 6 in which the amount of carbon black in the carbonaceous powder is large is low. Conversely, Comparative Sample 7, which contains a large amount of graphite in the carbonaceous powder, also has low electrical conductivity.

Example 4 (Samples 11 to 13 and Comparative Samples 8 and 9) The dependency of the weight ratio of the effective solid content of the resol-type phenol resin to the carbonaceous powder (graphite and carbon black) will be examined. In addition, natural flaky graphite (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.) having an average particle diameter of 16 μm (particle diameter range: 2 to 85 μm) is used as graphite, and DBP oil absorption is used as carbon black. Is 129cc
/ 100 g, and a resol type phenol resin having a weight average molecular weight of 1460 was used. The total amount of the carbonaceous powder was set to 100 parts by weight, the amount of the phenol resin was changed, and the other materials were mixed in the same manner as in Example 1. Five kinds of blends were used for the test, three for the working sample, and two for the comparative sample.
Table 4 shows their characteristics.

[0029]

[Table 4]

The samples 11 to 13 in which the weight ratio of the effective solid content of the resol type phenol resin to the carbonaceous powder is within the range of the present invention have a sheet resistance value of 10 Ω / □.
It has the following good electrical conductivity and good adhesion to a substrate. Among them, those having a weight ratio of phenol resin to carbonaceous powder of 60:40 (sample 13) are particularly excellent in electric conductivity. On the other hand, Comparative Sample 8, which contains a larger amount of the phenolic resin than the carbonaceous powder, has good adhesion, but has a small amount of the carbonaceous powder, which is a conductive material, and has a high sheet resistance. On the other hand, in Comparative Sample 9, the sheet resistance is not so high, but the adhesion is not good.

Example 5 (Examples 14 to 16, Comparative Samples 10 and 11) The dependence of the amount of polyvinyl butyral added to the carbonaceous powder (graphite and carbon black) will be examined. Graphite has an average particle diameter of 16 μm (particle diameter range of 2 to 85).
μm) of natural flaky graphite (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.), and carbon black having a DBP oil absorption of 129 cc / 100 g was used. 60 /
40, and the resol type phenol resin used had a weight average molecular weight of 1460, the total amount of carbonaceous powder was 100 parts by weight, and the amount of polyvinyl butyral was changed. The composition was the same as in Example 1. Five kinds of blends were used for the test, three for the working sample and two for the comparative sample. Table 5 shows their characteristics.

[0032]

[Table 5]

Samples 14 to 16 in which the amount of polyvinyl butyral added to the carbonaceous powder is within the scope of the present invention.
Has good electrical conductivity with a sheet resistance value of 10 Ω / □ or less, and also has good adhesion to the printed wiring board. Among them, the sample (sample 15) in which the added amount of polyvinyl butyral was 4 parts by weight was particularly excellent in electric conductivity. On the other hand, in the comparative sample 10 containing no polyvinyl butyral, the dispersed state of the conductive carbonaceous powder, particularly the natural flaky graphite, is insufficient, and a good conductive material cannot be obtained. On the other hand, in Comparative Sample 11, the sheet resistance was further increased because the amount of polyvinyl butyral added was too large.

Example 6 (Examples 17 to 19, Comparative Samples 12 and 13) Among the carbonaceous powders, the dependence of the addition amount of a titanate coupling agent on carbon black will be examined.
In addition, graphite has an average particle diameter of 16 μm (particle diameter range of 2 to 85).
μm) of natural flaky graphite (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.), and carbon black having a DBP oil absorption of 129 cc / 100 g was used. 60 /
40, and the resol type phenol resin used had a weight average molecular weight of 1460. The total amount of the carbonaceous powder was 100 parts by weight, and the amount of the coupling agent was changed. The composition was the same as in Example 1. Five kinds of blends were used in the test, of which three were for the working sample and two for the comparative sample. Table 6 shows their characteristics.

[0035]

[Table 6]

Examples 17 to 19 in which the addition amount of the titanate-based coupling agent to the carbon black is within the range of the present invention have good electric conductivity with a sheet resistance of 10 Ω / □ or less, and Good adhesion. On the other hand, in Comparative Sample 12 in which the amount of the coupling agent added was small, the dispersion state of carbon black among the carbonaceous powders in particular was insufficient, and a film having good electrical conductivity without a dense coating was obtained. Absent. On the other hand, in Comparative Sample 13 in which the amount of the coupling agent added was large, the coupling agent remained in the film, and the electrical conductivity was still poor.
Even when a thermosetting treatment is performed at a temperature of 0 ° C., the coupling agent remains in a liquid state in a liquid state, so that the adhesion of the film to the substrate is reduced and the coating film is peeled off.

[0037]

The structure of the carbon-based conductive paste according to the production method of the present invention is as described above. However, the carbon film formed by this paste has a higher sheet resistance than the film formed by the conventional carbon-based conductive paste. Value is 1
It is as low as about ４ to ３ and shows high electric conductivity. Carbon-based conductive coatings do not have as good electrical conductivity as conductive coatings made of metallic powder, but they do not have problems such as migration in silver powder or oxidation in copper powder. Can replace a film made of metal powder with a carbon film, and a new use of a carbon-based conductive paste can be expected.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C09D 161/06 C09D 161/06 (56) References JP-A-7-41706 (JP, A) JP-A-54-50897 (JP) JP-A-54-36343 (JP, A) JP-A-64-26683 (JP, A) JP-A-58-167655 (JP, A) JP-A-60-93702 (JP, A) 61-101554 (JP, A) JP 60-58268 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 161/00-161/34 C09D 5/24 H01B 1 / 00-1/24

Claims (2)

(57) [Claims] A resol type phenol resin dissolved in an organic solvent contains carbon black and an average particle diameter of 10 to 20.
In a method for producing a carbon-based conductive paste in which carbonaceous powder composed of natural flaky graphite having a diameter of μm is kneaded and dispersed together with polyvinyl butyral and a titanate-based coupling agent, dibutyl phthalate (DBP) oil absorption is used as the carbon black. Is 115 to 100 g
Use the carbon black is a 170cc, the Chita
The nate-based coupling agent is replaced with the carbon black
A method for producing a carbon-based conductive paste, wherein 8 to 12 parts by weight is added to parts by weight . 2. The weight average molecular weight of (a) the resole type phenol resin is 1100 to 1530, and (b) the compounding amount of natural flaky graphite and carbon black of the carbonaceous powder is 50:50 by weight. ~ 70: 30,
(C) The compounding amount of the effective solid content of the carbonaceous powder and the resol-type phenol resin is 50:50 to 60: 4 by weight ratio.
0, and, (d) method for producing a carbon-based conductive paste according to claim 1, wherein 2 to 6 parts by weight added pressure to Rukoto said polyvinyl butyral to said carbonaceous powder 100 parts by weight.