JP2005259546A - Conductive paste for rotary screen printing apparatus and conductor circuit using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain conductive paste for a rotary screen printing apparatus excellent in successive printing without running, providing mass-productive conductor circuits. <P>SOLUTION: This is related to a conductive paste containing a conductive fine powder (A), a binder (B), an organic solvent (C) and/or water, with 5.0 or less thixotropy; and to a conductor circuit using the paste. Preferably, the conductive fine powder (A) contains a carbon black and/or a graphite fine powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductive paste. More specifically, the conductive paste is applied, printed, or cured on a film or a substrate to impart conductivity, thereby forming a circuit, or a terminal or lead wire of an electronic component. The present invention relates to a conductive paste used for bonding or protecting an electronic device from electromagnetic interference (EMI), and particularly relates to a conductive paste suitable for rotary screen printing and excellent in printability.

  A membrane circuit obtained by printing a conductive paste on a PET film or the like is low-cost and lightweight, and is widely used for keyboards, transparent touch panels, switches, EL light emitters, planar heating elements, and the like. Normally, a circuit is formed by screen printing, but rotary screen printing that can be printed in a long size is used for large-sized ones such as a large EL light emitter and a planar heating element for floor heating. However, rotary screen printing has poor printability compared to normal screen printing. In recent years, finer print patterns, resistance value and film thickness control during continuous printing for a long time, surface smoothness, etc. The required properties are becoming stricter, and conventional inks cannot cope with them, and there is a strong demand for conductive pastes with good printability. For example, Patent Document 1 discloses a conductive paste for rotary screen printing, but there is a problem in continuous productivity.

JP 2003-110225 A

  In a rotary screen printing method in which a long and continuous screen plate is formed into a cylindrical shape, the rotary screen plate has a smaller aperture ratio and a smaller hole diameter than a normal flat screen due to its configuration. It is difficult to print a fine pattern with a thick film, and the conductive paste is rotated and stirred for a long time with the conductive paste in it. In the latter half of printing compared to the initial printing stage, the film thickness is lowered, the circuit resistance is increased, and there is a problem that blurring occurs. This characteristic becomes a problem particularly in printing of resistors in which the upper and lower limits of circuit resistance are set strictly. Accordingly, the present invention solves these problems, and uses a conductive paste excellent in circuit printability, which is used in a method of forming a conductor circuit by a rotary screen printing method, and a method of manufacturing a conductor circuit excellent in mass productivity using the same. Objective.

As a result of intensive studies to solve the above problems, the present inventors have found that a conductor circuit with less blurring and good continuous printability, that is, good mass productivity can be obtained.
That is, the present invention relates to the following conductive paste and a printed circuit using the same.
(1) A rotary characterized in that in a conductive paste containing a conductive fine powder (A), a binder (B), an organic solvent (C) and / or water, the degree of change is 5.0 or less. Conductive paste for screen printing machines.
(2) The conductive paste for a rotary screen printing machine according to claim 1, wherein the conductive fine powder (A) contains carbon black and / or graphite fine powder.
(3) A conductor circuit produced by using the conductive paste according to claim 1 or 2 using a rotary screen printer.

  The conductive paste of the present invention has very high continuous printability when a conductor circuit is formed by a rotary screen printing method by setting the fluctuation degree to 5.0 or less, and in particular, a conductor such as a resistor. Suitable for circuit manufacturing.

  The fluctuation degree of the conductive paste of the present invention needs to be 5.0 or less. Preferably it is 4.0 or less, More preferably, it is 3.0 or less. By reducing the degree of fluctuation, the decrease in paste viscosity during continuous printing is reduced and the film thickness is stabilized. That is, the circuit resistance is stabilized. When the degree of change exceeds 5.0, the viscosity is lowered due to the share during printing, causing blurring, and the film thickness is reduced during continuous printing, resulting in an increase in resistance.

In the present invention, the fluctuation degree is measured by the following procedure. A conductive paste is put into a wide-mouthed light-shielding bottle (100 ml) manufactured by Nikko Corporation, and the liquid temperature is adjusted to 25 ° C. ± 0.5 ° C. using a constant temperature water bath. Next, stirring was performed 40 times using a glass rod for 12 to 15 seconds, and a predetermined rotor of a Brookfield BH type rotational viscometer was set and left standing for 5 minutes, and then rotated at 20 rpm for 3 minutes. Read the scale. In addition, the measurement is performed at 2 rpm in the same manner. The viscosity is calculated by multiplying this scale by the coefficient in the conversion table. From the viscosity value measured at 2 rpm after the measurement is completed and the viscosity value measured at 20 rpm, the following formula is used.
Deflection = viscosity (2 rpm) / viscosity (20 rpm)

  In order to reduce the degree of fluctuation, there is a method of reducing the blending amount of the conductive fine powder (A), but simply reducing the blending amount of the conductive fine powder (A) reduces the conductivity, Since there exists a problem which deteriorates storage stability, it is especially preferable to mix | blend a dispersing agent.

  As the dispersant, known ones such as silicone-based, organic polymer-based, fatty acid salt-based, silane coupling agent, aluminum-based coupling agent, polyamide, amino group-containing polymer, sulfonate metal group-containing polymer can be used. Among these, when carbon black is used for the conductive fine powder, a polyamide type or tertiary amine-containing polymer type dispersant is particularly preferable. By using these dispersants, the fluctuation degree can be reduced to an appropriate value without reducing the blending amount of the conductive fine powder.

  As the conductive fine powder (A) used for the conductive paste of the present invention, flaky silver powder, spherical silver powder, three-dimensional higher order silver powder, dendritic silver powder, graphite powder, carbon powder, nickel powder, copper powder, Examples thereof include gold powder, palladium powder, aluminum powder, and indium powder. Among these, preferable conductive fillers include known flaky silver powder, graphite powder, and conductive carbon black. In addition, a small amount of non-conductive filler such as silica powder, fumed silica, colloidal silica, talc, and barium sulfate may be blended for the purpose of adjusting paste viscosity.

  In the conductive paste of the present invention, the binder (B) is used as a binder resin in combination with the conductive fine powder (A). The type of the binder (B) is not limited, but the number average molecular weight is preferably 3000 or more, more preferably 8000 or more from the viewpoint of bending resistance. If the number average molecular weight is less than 3000, good flex resistance is difficult to obtain, and the paste viscosity tends to decrease. The upper limit is preferably 100,000 or less.

  The types of binder (B) include polyester resins, urethane-modified polyester resins, epoxy-modified polyester resins, various modified polyester resins such as acrylic-modified polyester, polyether urethane resins, polycarbonate urethane resins, vinyl chloride / vinyl acetate. Examples thereof include polymers, epoxy resins, phenol resins, acrylic resins, polyamideimides, nitrocellulose, modified celluloses such as cellulose acetate acetate butyrate (CAB), cellulose acetate acetate propionate (CAP), and the like.

  Of these, epoxy resin and phenolic resin can be used for applications such as flexible conductive adhesives, rigid circuit board conductive pastes, and through-hole conductive pastes. In the case of using a flexible and relatively difficult-to-adhere base material such as polyimide film, polyester resin, the above modified polyester resin, vinyl chloride / vinyl acetate copolymer from the viewpoint of flex resistance and adhesion to the base material The most preferred is a copolyester resin and / or a modified polyester resin (D), and the characteristics can be exhibited particularly when used for such a flexible substrate.

  More specifically, as the binder (B), it is preferable to use a polyester resin having a number average molecular weight of 3000 or more and / or a modified polyester resin (D), and has extremely excellent bending resistance and adhesion to a substrate. Sex is obtained. The number average molecular weight is preferably 8000 or more, more preferably 10,000 or more. The upper limit is preferably 50000 or less.

  When the number average molecular weight is less than 3,000, good bending resistance cannot be obtained, and the paste viscosity tends to decrease. The glass transition temperature is preferably −20 ° C. or higher, more preferably −5 ° C. or higher, in terms of bending resistance and hardness. A preferable upper limit is 70 degrees C or less.

  As the polyester resin used in the present invention, those obtained by polycondensation by a known method under normal pressure or reduced pressure can be used. The polyester resin is preferably a saturated polyester. In addition, after polymerizing the polyester resin, the cyclic ester such as ε-caprolactone is post-added (ring-opening addition) at 180 to 230 ° C. to block, or the acid anhydride such as trimellitic anhydride or phthalic anhydride is terminated. An acid value may be given by an addition reaction later.

  Dicarboxylic acids copolymerized with polyester are aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, azelaic acid. Aliphatic dicarboxylic acids such as C12-28 dibasic acids, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxy hydrogenated bisphenol A, dicarboxy hydrogenated bisphenol S, dimer acid, hydrogenated dimer acid, hydrogenated naphthalene dicarboxylic acid, tricyclodecane dicarboxylic acid Fats such as acids It is family dicarboxylic acid. In addition, within the scope of not impairing the content of the invention, polyvalent carboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and 5-sulfo A sulfonic acid metal base-containing dicarboxylic acid such as sodium isophthalate may be used in combination.

  The alkylene glycol used in the polyester used as the polyester resin and modified polyester resin (D) of the present invention is ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol. , Neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 2-butyl 2-ethyl-1,3-propanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, Dimer diol etc. are mentioned. Moreover, you may use together polyhydric polyols, such as a trimethylol ethane, a trimethylol propane, glycerol, a pentaerythritol, a polyglycerol, in the range which does not impair the content of invention. Among these, from the viewpoint of durability, the acid component is preferably a combination of aromatic dicarboxylic acid, alicyclic dicarboxylic acid, and aliphatic dicarboxylic acid having 9 or more carbon atoms, and the glycol component is neopentyl glycol, having 5 to 10 carbon atoms. Long chain aliphatic diols are particularly preferred.

  Moreover, the polyester resin used for the electrically conductive paste of this invention can be modified | denatured and used by well-known methods, such as urethane modification, epoxy modification, (meth) acrylate modification, and (meth) acryl graft modification. Of these, urethane modification is particularly preferred from the viewpoint of bending resistance and adhesion. A urethane-modified resin synthesized by a known method by reacting a polyester polyol and, if necessary, a chain extender with an isocyanate compound can be used.

  The above-described polyester polyol is used as the polyol having a molecular weight of 500 or more used in the urethane-modified polyester resin. In addition, a polyether polyol, a (meth) acryl polyol, a polycarbonate diol, a polybutadiene polyol, and other polyols may be used in combination. Good. As other polyols, polycarbonate diol is particularly preferable in view of adhesiveness, flex resistance, and durability. As polyols having a molecular weight of less than 500 used as chain extenders, known polyols such as neopentyl glycol, 1,6-hexanediol, ethylene glycol, HPN (hydroxypivalate ester of neopentyl glycol), trimethylolpropane, and glycerin are available. Can be mentioned. Furthermore, carboxyl group-containing polyols such as dimethylolpropionic acid can also be used as chain extenders.

Examples of the diisocyanate compound used for urethane modification include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate.
The urethane group concentration of the polyester urethane resin as the modified polyester resin (D) is preferably 500 equivalents / 10 ⁶ g or more and 4000 equivalents / 10 ⁶ g or less in terms of adhesion and bending resistance. The upper limit is preferably 6000 equivalents / 10 ⁶ g or less from the viewpoint of solubility. The number average molecular weight is required to be 3000 or more, preferably 8000 or more, more preferably 10,000 or more in view of flex resistance and paste viscosity. The upper limit is not particularly defined, but is preferably 100,000 or less from the reactivity and paste viscosity.

  The polyester resin and / or modified polyester resin (D) may be used in combination with other resins. As other resins, vinyl chloride / vinyl acetate copolymers are particularly preferable, and known commercially available products can be used. The content of vinyl chloride in the polymer is preferably 85 to 95% in view of solubility and physical properties of the coating film. Further, a polar group may be introduced by copolymerizing a small amount of maleic acid, vinyl alcohol or the like as a monomer other than vinyl chloride or vinyl acetate. When a carboxyl group is introduced with maleic acid, adhesion to a metal is improved, and when a hydroxyl group is introduced with vinyl alcohol, an isocyanate compound can be used as a curing agent.

  The binder (B), polyester resin and / or modified polyester resin (D) used in the present invention may be used in combination with a curing agent. The curing agent capable of reacting with these resins is not particularly limited, but an isocyanate compound is particularly preferable from the viewpoint of adhesion, flex resistance, curability, and the like. Further, these isocyanate compounds are preferably used after being blocked from the viewpoint of storage stability. Examples of curing agents other than isocyanate compounds include known compounds such as amino resins such as methylated melamine, butylated melamine, benzoguanamine, and urea resin, acid anhydrides, imidazoles, epoxy resins, and phenol resins.

  Examples of the isocyanate compound include aromatic and aliphatic diisocyanates and trivalent or higher polyisocyanates, which may be either low molecular compounds or high molecular compounds. For example, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate or trimers of these isocyanate compounds, and excess of these isocyanate compounds Amount of low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine or various polyester polyols, polyether polyols, polyamides Obtained by reacting with polymer active hydrogen compounds Terminal isocyanate group-containing compounds to be.

  Examples of the isocyanate compound blocking agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol, oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime, Alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol; -Lactams such as caprolactam, [delta] -valerolactam, [gamma] -butyrolactam, [beta] -propylactam, and others, and aromatic amines, imides, acetyl Acetone, acetoacetic ester, active methylene compounds such as malonic acid ethyl ester, mercaptans, imines, imidazoles, ureas, diaryl compounds, sodium bisulfite, etc. can be mentioned. Of these, oximes, imidazoles, and amines are particularly preferable from the viewpoint of curability.

  These crosslinking agents may be used in combination with known catalysts or accelerators selected according to the type.

  Furthermore, an active energy ray-curable resin can be used for the binder (B). An active energy ray-curable compound is a compound that is polymerized by irradiation with active energy rays, and a compound having an ethylenically unsaturated group is preferably used. Examples of the compound having an ethylenically unsaturated group include (meth) acrylic acid, (meth) acrylate compounds, vinyl ether compounds, polyallyl compounds, and the like. These compounds are used alone or in combination of two or more.

  The type of the organic solvent (C) used in the present invention is not limited, and examples thereof include ester type, ketone type, ether ester type, chlorine type, alcohol type, ether type, and hydrocarbon type. Among these, in the case of screen printing, a high boiling point solvent such as ethyl carbitol acetate, butyl cellosolve acetate, ethyl carbitol, butyl cellosolve, isophorone, cyclohexanone, and γ-butyrolactone is preferable. Further, water may be used alone or in combination with an organic solvent.

  In the conductive paste of the present invention, the viscosity is important in addition to the degree of fluctuation. The preferred viscosity is 50 dPa · s or more, more preferably 100 dPa · s or more, when measured at Brookfield BH type, 20 rpm, 25 ° C. The upper limit is preferably 1000 dPa · s or less, and more preferably 800 dPa · s or less. If it is less than 50 dPa · s, blurring occurs and the film thickness tends to be low. If it exceeds 1000 dPa · s, there is a tendency for blurring to occur.

  The content of the conductive fine powder (A) contained in the conductive paste of the present invention, when using a metal powder such as silver powder, from the conductive aspect, based on the total solid content of the conductive paste, It is preferably 60% by weight or more, more preferably 80% by weight or more. The upper limit is preferably 90% by weight or less. If it is less than 60% by weight, good conductivity may not be obtained, and if it exceeds 90% by weight, the degree of fluctuation tends to increase. When carbon black and / or graphite is used for the conductive fine powder (A), it is preferably 40% by weight or more, more preferably 45% by weight or more. The upper limit is preferably 70% by weight or less, and more preferably 65% by weight or less. If it is less than 30% by weight, the conductivity tends to deteriorate or the storage stability tends to deteriorate. If it exceeds 70% by weight, the degree of fluctuation tends to increase.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to this. In the examples, parts are parts by weight.

1. Molecular weight The number average molecular weight in terms of polystyrene was measured by GPC. Tetrahydrofuran was used as a measurement solvent.

2. Glass transition temperature (Tg)
It measured with the temperature increase rate of 20 degree-C / min using the differential scanning calorimeter (DSC). As a sample, 5 mg of a sample was placed in an aluminum press-lid container and crimped.

3. Acid value 0.2 g of a sample was precisely weighed and dissolved in 20 ml of chloroform. Subsequently, it titrated with 0.01N potassium hydroxide (ethanol solution). A phenolphthalein solution was used as an indicator.

4). Viscosity of conductive paste Using a Brookfield BH type rotational viscometer, the viscosity was measured by the following procedure. The conductive paste was put into a wide-mouthed light-shielding bottle (100 ml) manufactured by Nikko Corporation, and the liquid temperature was adjusted to 25 ° C. ± 0.5 ° C. using a constant temperature water bath. Subsequently, it stirred 40 times over 12-15 seconds using the glass rod, and after setting a predetermined rotor and leaving still for 5 minutes, the scale when it rotated for 3 minutes at 20 rpm was read. The viscosity was calculated by multiplying this scale by the coefficient in the conversion table.

5). 3. Fluctuation degree of conductive paste In the same manner as above, a Brookfield BH rotational viscometer was used, and the following formula was calculated from the viscosity value measured at 25 ° C. and 2 rpm and the viscosity value measured at 20 rpm.
Deflection = viscosity (2 rpm) / viscosity (20 rpm)

6). Specific resistance Using a far-infrared conveyor furnace, the sheet resistance of the conductive paste film cured by heating at 150 ° C. for 3 minutes is a digital multimeter in the case of carbon paste, and a 4 deep needle resistance measuring instrument in the case of silver paste. The specific resistance was calculated from the sheet resistance and film thickness.

7). Adhesiveness It evaluated according to JIS K5400 8.5. Cellophane tape CT-12 (manufactured by Nichiban Co., Ltd.) was used as the adhesive tape.

8). Evaluation of printability A 215 mesh screen plate (RotaMesh RM215) is mounted on a rotary screen printer (STORK: RSC-10) that continuously feeds a web-like PET film with a thickness of 100 μm that has been annealed from an unwinder. Then, the conductive paste was printed on the web-like PET film. Further, the PET film was continuously dried and cured in a far infrared furnace at a surface temperature of 150 ° C. for 3 minutes to obtain a web-like PET film on which a conductor circuit having a dry film thickness of 20 to 25 μm was printed. A printing pattern having a size of 25 × 150 mm was used. For evaluation of continuous printability, this pattern was continuously printed, the circuit resistance value R1 of the fifth printing and the circuit resistance R2 of the 3000th printing were measured, and the resistance change rate was obtained by the following equation. The lower the absolute value of the resistance change rate, the better the printability. In addition, the blurring was evaluated based on the appearance of the 3000th coating film.
Resistance change rate (%) = {(R2-R1) / R1} × 100 (%)

Synthesis example. 1 (Polyester resin a)
A four-necked flask equipped with a Gubileu fractionator is charged with 101 parts of dimethyl terephthalate, 72 parts of dimethyl isophthalate, 93 parts of ethylene glycol, 73 parts of neopentyl glycol, and 0.068 parts of tetrabutyl titanate. Exchange was performed. Next, 22 parts of sebacic acid was charged and further esterification was performed. Next, the pressure was gradually reduced to 1 mmHg or less, and polymerization was performed at 240 ° C. for 1 hour. The composition of the obtained copolyester was terephthalic acid / isophthalic acid / sebacic acid // ethylene glycol / neopentyl glycol = 52/37/11 // 55/45 (molar ratio) / g, number average molecular weight 22,000. The acid value was 1.5 mgKOH / g and Tg = 45 ° C.

Synthesis example. 2 (urethane-modified polyester resin b)
Synthesis example. 1, terephthalic acid / isophthalic acid / sebacic acid // ethylene glycol / neopentyl glycol = 52/18/30 // 55/45 (molar ratio) / g, number average molecular weight 2,000, acid value 1 A polyester oligomer of .8 mg KOH / g and Tg = −5 ° C. was synthesized. In a reaction vessel equipped with a thermometer, stirrer, and cooler, 100 parts of this polyester oligomer, 3 parts of neopentyl glycol as a chain extender and ethyl carbitol acetate were charged, dissolved at 80 ° C., and then diphenylmethane diisocyanate (MDI). 19.4 parts and 0.05 part of dibutyltin dilaurate were added and reacted at a solid content of 50% at 70 to 80 ° C. for 3 hours or more until there was no residual isocyanate, and then a solid content of 30 with ethyl carbitol. % To obtain a urethane-modified polyester resin b. The number average molecular weight was 25000, the acid value was 1.0 mgKOH / g, and the glass transition temperature was 15 ° C.

Example. 1
Polyester resin a is dissolved in ethyl carbitol acetate (diethylene glycol monoethyl ether acetate) in advance, and 5.0 parts by weight of Ketjen Black ECP 600JD (manufactured by Lion Corporation) as a conductive carbon black in a solid part of this varnish 58.1. , 10.0 parts by weight of Raven 1255 (Colombian Carbon Japan Co., Ltd.), 25.0 parts by weight of graphite BF (manufactured by Chuetsu Graphite Industries Co., Ltd.), biuret trimer of hexamethylene diisocyanate as a curing agent 1.9 solid parts of methyl ethyl ketoxime, 0.5 parts by weight of polyflow S (manufactured by Kyoeisha Chemical Co., Ltd.) as a leveling agent, 5.0 parts by weight of Dispavic 161 (manufactured by BYK Chemie) as a dispersing agent, curing Contains 0.02 parts by weight of dibutyltin dilaurate as a catalyst Then, after sufficient premixing, it was dispersed three times with three rolls to obtain a carbon paste. When the viscosity was adjusted to 300 dPa · s by diluting with ethyl carbitol acetate, the degree of fluctuation was 1.2. The specific resistance was 3.5 Ω · cm. When continuous printability was evaluated, the resistance change after 3000 printing showed a low value of + 2.1%, and the coating film appearance was good with no blurring or blurring. . The results are shown in Table 1.

Example. 2-4
Example. Evaluation was performed in the same manner as in 1. Example. 3 is an example in which an aluminum coupling agent is used in place of the dispersant. Example. No. 4 is an example of a silver paste, but all achieved a low degree of fluctuation and the continuous printability was very good. The results are shown in Table 1.

Comparative Examples 1-4
Evaluation was performed in the same manner as in Example 1. Both are examples of high fluctuation, but a large resistance change was observed in continuous printing, and the appearance of the coating film was blurred. Comparative example. Examples 1 and 2 are examples in which no dispersant or coupling agent is used, and the degree of tremor is very high. Comparative example. No. 3 used an aluminum-based coupling agent, but a large amount of ketjen black having a large oil absorption amount was blended, so that the degree of fluctuation was high. Comparative example. Although 4 is an example of silver paste, a dispersant is used, but the amount of silver powder is large, and the amount of ketjen black with a large oil absorption is also large, so that the degree of fluctuation is high. In any of the comparative examples, the film thickness decreases and the circuit resistance increases due to continuous printability. The results are shown in Table 2.

  With the conductive paste of the present invention, it is possible to reduce the reduction in film thickness by continuous printing with a rotary screen printer, and it is possible to create a circuit material with good printability without blurring or blurring. As a result, a stable circuit resistance can be obtained even in continuous printing.

Claims (3)

  A rotary screen printing machine characterized in that in a conductive paste containing a conductive fine powder (A), a binder (B), an organic solvent (C) and / or water, the degree of change is 5.0 or less. Conductive paste.   The conductive paste for a rotary screen printing machine according to claim 1, wherein the conductive fine powder (A) contains carbon black and / or fine graphite powder.   A conductor circuit prepared by using a rotary screen printer using the conductive paste according to claim 1.