JP2001319524A - Conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit material using a conductive paste having improved heat resistance, moisture resistance, thermal shock resistance and bending resistance and showing improved adhesion to an organic film, a metal substrate or a glass substrate. SOLUTION: The conductive paste comprises a conductive powder (A), a binder (C) containing a polyester resin (B) having a number-average molecular weight of 3000 or more and a solvent (D), as main components. The polyester resin (B) contains 70 mol% or more aromatic dicarboxylic acid in terms of all acidic components and a glycol component containing aliphatic glycol and/or alicyclic glycol having principal chains with the number of carbon atoms being 5 or more and aliphatic polycarbonate diol. The resin contains 5-60% by weight of polycarbonate diol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste, and more particularly, to coating or printing a conductive paste on a film such as polyethylene terephthalate, vinyl chloride or nylon, a metal substrate, or a glass substrate.
By giving conductivity by curing, to form a circuit,
It relates to conductive paste used for bonding terminals and lead wires of electronic parts and protecting electronic devices from electromagnetic interference (EMI). Particularly, high conductivity and low temperature bending resistance, 85 ° C. Above and / or 85 ° C, 85
The present invention relates to a conductive paste suitable for circuit formation and adhesives of parts such as automobiles and OA equipment that require heat resistance, humidity resistance, and thermal shock resistance at% RH or higher.

[0002]

2. Description of the Related Art A membrane circuit formed by printing a conductive paste on a PET film or the like is lightweight and widely used for keyboards and switches. However, the required characteristics are becoming stricter year by year, and in a higher environment than before, that is, 85 ° C. or higher and / or 85 ° C., 85% RH
With the above conductivity and low temperature bending resistance, and heat resistance,
There is a strong demand for compatibility with both moisture resistance and thermal shock resistance.

A known conductive paste is disclosed in
No. 9-206449. This is a silver paste for a membrane circuit using a polybutadiene resin and a blocked isocyanate compound obtained by blocking an isocyanate group with an oxime compound or caprolactam as a binder, but has a relatively good bending resistance. However, the durability in heat resistance, moisture resistance, and thermal shock resistance is poor.

Japanese Patent Application Laid-Open No. 1-159906 discloses a silver paste having excellent flexing resistance using flake-like (flake-like) silver powder, a copolymerized polyester resin and a blocked isocyanate compound as a binder. However, durability in heat resistance, moisture resistance, and thermal shock resistance is poor.

[0005] Japanese Patent Application Laid-Open No. 60-223871 discloses a known conductive paste of the fast-curing type. Although it is a conductive paste using a blocked isocyanate blocked with imidazole as a curing agent, it has a drawback in pot life, and further has poor heat resistance, moisture resistance, and heat shock resistance.

[0006] Epoxy resins, phenol resins, and the like are examples of resins that exhibit good adhesiveness to films such as polyethylene terephthalate, vinyl chloride, and nylon, and metals. JP-A-8-245754, JP-A-7-245
JP-A-278274 is a conductive paste having excellent moisture resistance comprising an epoxy resin and a phenol resin, and JP-A-9-259636 discloses a conductive paste comprising an epoxy resin and a sulfonium salt and having excellent heat resistance and moisture resistance. It is. These conductive pastes are unsatisfactory in severe bending properties such as 360 ° where R of the bent portion is 0 mm. Also, good adhesion to metal foils and films cannot be obtained.

Japanese Patent Application Laid-Open No. 55-149356 discloses a conductive paste made of an acrylic resin and having excellent heat resistance, but has a drawback that its reliability under high temperature and high humidity is poor.

JP-A-6-116517 discloses a heat-resistant and moisture-resistant conductive paste made of a polyamide-imide silicone polymer. JP-A-6-136300 discloses a polyamide-imide silicone polymer and an epoxy resin. It is a conductive paste which is excellent in heat resistance and moisture resistance. Also in these conductive pastes, the R at the bent portion is 0 m.
A severe bending property such as m of 360 ° is not good.

JP-A-7-41706 discloses a resol type phenol resin and an epoxy resin, a polyester resin,
The conductive paste is made of at least one resin selected from polyvinyl butyral resins and has excellent moisture resistance and temperature cycle resistance.
A severe bending property such as 360 ° in mm is bad.

[0010]

In order to obtain good adhesiveness and flexibility in the resin composition used for the conductive paste, the glass transition temperature usually needs to be 10 ° C. or less. Performance deteriorates in durability of moisture resistance. On the other hand, when trying to obtain durability, there is a problem that sufficient flexibility cannot be obtained.

[0011]

In order to solve these problems, the present inventors have excellent adhesiveness and low-temperature flexibility, and have durability such as heat resistance, moisture resistance and thermal shock resistance. As a result of diligent study of a resin composition suitable for a conductive paste having both, the number average molecular weight is 3000 or more, the aromatic dicarboxylic acid is 70 mol% or more, and the glycol component has 5 or more carbon atoms in the main chain. The polyester resin mainly composed of an aliphatic glycol and / or an alicyclic glycol and an aliphatic polycarbonate diol and containing the polycarbonate diol in an amount of 5 to 80% by weight has excellent adhesiveness and low-temperature flexibility. The present invention has been found to have surprising physical properties that combine heat resistance, moisture resistance, thermal shock resistance, and other durability, and have reached the present invention. The conductive paste of the present invention has high conductivity and low-temperature bending resistance, and also has durability such as heat resistance, moisture resistance and thermal shock resistance, and can overcome the problems of the prior art.

[0012] That is, the present invention relates to a conductive paste comprising a conductive powder (A), a binder (C) containing a polyester resin (B) having a number average molecular weight of 3,000 or more and a solvent (D) as main components. (B) a polyester resin containing an aliphatic diglycol and / or an alicyclic glycol having an acid component of 70 mol% or more of aromatic dicarboxylic acid and a glycol component having a main chain of 5 or more carbon atoms and an aliphatic polycarbonate diol; And a polyester resin containing the polycarbonate diol in an amount of 5 to 80% by weight in the resin.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Conductive powder (A) used in the present invention
Is preferably silver powder alone or one mainly composed of silver powder.
The silver content in the conductive powder is preferably at least 50%, more preferably at least 70%. Examples of the shape of the conductive powder include known flakes (flakes), spheres, dendrites (dendrites), and three-dimensionally aggregated spherical primary particles described in JP-A-9-306240. Among them, there are shapes and the like, and among them, flake silver powder and silver powder having a shape in which the spherical primary particles are three-dimensionally aggregated are particularly preferable. The flake silver powder has an average particle size (50%
D) is preferably from 1 to 15 μm, more preferably from 2 to 8 μm.
μm, and more preferably 2 to 5 μm. In addition to silver powder, conductive powders include carbon fillers such as carbon black and graphite powder, precious metal powders such as gold powder, platinum powder and palladium powder, base metal powders such as copper powder, nickel powder, aluminum powder and brass powder, and silver. Base metal powder plated or alloyed with a noble metal such as the above can be used alone or in combination with silver powder. In addition, silica, talc, mica, inorganic fillers such as barium sulfate, etc. can be mixed with silver powder and used, but from the viewpoint of environmental properties such as conductivity and moisture resistance, and cost,
20 carbon black and graphite powder in all conductive powder
Wt% or less, more preferably 10 wt% or less 0.01
It is preferable to mix it by weight percent or more.

The mixing ratio of the conductive powder (A) and the binder (C) used in the present invention is such that the ratio (A) / (C) is 60 / 40-9.
5/5 (weight ratio) is preferred, and 80/2 is more preferred.
0 to 90/10. When the ratio (A) is less than 60/40 in the ratio (A) / (C), good conductivity, bending resistance, heat resistance, moisture resistance, thermal shock resistance and the like cannot be obtained, and
If it exceeds 5, the bending resistance and the adhesion are undesirably reduced.

The binder (C) used in the present invention comprises at least 70 mol% of an aromatic dicarboxylic acid in the total acid component, and the glycol component is an aliphatic glycol and / or alicyclic ring having a main chain of 5 or more carbon atoms. A polyester resin containing an aliphatic glycol and an aliphatic polycarbonate diol, wherein the polycarbonate diol is 5 to 80% by weight in the resin.
Contains the included polyester resin (B). The use of this polyester as a binder results in surprisingly good flex resistance and high environmental properties. The number average molecular weight of the polyester resin (B) is at least 3,000, preferably at least 8,000, more preferably at least 15,000. If the number average molecular weight is less than 3,000, the bending resistance is reduced. Further, the paste viscosity is undesirably reduced. The reduced viscosity of the polyester resin (B) is preferably at least 0.2 dl / g, more preferably at least 0.4 dl / g.
dl / g or more, more preferably 0.5 dl / g or more. In the polyester resin (B), the aromatic dicarboxylic acid accounts for 70 mol% or more of all the acid components, preferably 80 mol%.
Mol% or more, more preferably 90 mol% or more.
If the amount of the aromatic dicarboxylic acid is less than 70 mol%, the strength of the coating film is reduced, and the low-temperature bending resistance, heat resistance, moisture resistance, thermal shock resistance and other durability are reduced.

The polyester resin (B) used in the present invention
It is necessary that the glycol component to be copolymerized contains an aliphatic glycol having a main chain of 5 or more carbon atoms and / or an alicyclic glycol and an aliphatic polycarbonate diol. By using these glycols, it becomes a resin that has low-temperature bending resistance, and also has durability such as heat resistance, moisture resistance, and thermal shock resistance.The conductive paste using this resin has high conductivity and high conductivity. It has low-temperature bending resistance and durability such as heat resistance, moisture resistance, and thermal shock resistance. The glass transition point temperature of the polyester resin (B) is preferably 15 ° C. or lower, more preferably 0 ° C. or lower, and further preferably -10 ° C. to −30 ° C. Examples of the aliphatic glycol having a main chain having 5 or more carbon atoms copolymerized with the polyester resin (B) include 1,5-pentanediol and 1,6-pentanediol.
Hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 1,9
-Nonanediol, 1,10-decanediol and the like are used alone or in combination of two or more. By using these long-chain glycols,
Good adhesion, flexibility and heat resistance are obtained, and surprisingly the moisture resistance is significantly improved. Particularly, 1,5-pentanediol and 1,6-hexanediol are preferred.

Examples of the alicyclic glycol include 1,4-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,2-cyclohexane dimethanol, tricyclodecane glycol, dimer diol and the like. Of these, 1,4-cyclohexanedimethanol is preferred from the viewpoint of moisture resistance, but is preferably used in an amount of 20 mol% or less because the glass transition temperature increases.

As the aliphatic polycarbonate diol, the starting material glycol is ethylene glycol, neopentyl glycol, propylene glycol, 1,3-
Propanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-propyl-2-methyl-1,3propanediol, 1,4-butane Diol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-
An aliphatic polycarbonate diol composed of one or more of 1,5-pentanediol, 2-methyl-1,5 pentanediol, 1,9-nonanediol, 1,10-decanediol and the like, alone or in combination of two or more. To use.

Of these, polycarbonate diols composed of an aliphatic glycol having less than 5 carbon atoms in the main chain are not preferred because the polycarbonate diols are decomposed during polymerization and flow out of the system, and 1,5-pentanediol and 1,6-hexanediol are not preferred. Polycarbonate diols composed of aliphatic glycols having 5 or more carbon atoms, such as, for example, are preferred.

Other polycarbonate diols include 1,4-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,2-cyclohexane dimethanol, TCD glycol, hydrogenated bisphenol A, and other polycarbonate resins (Mikio Matsugane et al.) Alicyclic diols described in Nikkan Kogyo Shimbun), 1,6-dimethylolbenzene, bisphenol A alkylene oxide, bisphenol A, bisphenol F, bisphenol S, 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, Other polycarbonate diols include aromatic diols described in polycarbonate resins (Mikio Matsugane et al., Nikkan Kogyo Shimbun).
These polycarbonate diols may be used as long as the content of the invention is not impaired.

Other glycols include ethylene glycol, neopentyl glycol, propylene glycol, 1,3-propanediol, 2,2-diethyl-
1,3-propanediol, 2-butyl-2-ethyl-
Aliphatic glycols having less than 5 carbon atoms in the main chain, such as 1,3-propanediol and 1,4-butanediol;
Examples thereof include polyether diols such as polyethylene glycol and polytetramethylene glycol. Aliphatic glycols having less than 5 carbon atoms in the main chain are not preferred because polycarbonate diol is decomposed during polymerization, and polyether-based diols are not preferred because heat resistance and moisture resistance become insufficient. In addition, trimethylolethane, trimethylolpropane, and so on as long as the content of the invention is not impaired.
Polyhydric polyols such as glycerin, pentaerythritol and polyglycerin may be used in combination.

Examples of the aromatic dicarboxylic acid copolymerized with the polyester resin (B) include terephthalic acid, isophthalic acid, orthophthalic acid and 2,6-naphthalenedicarboxylic acid. Of these, terephthalic acid and isophthalic acid are preferably used in combination from the viewpoint of physical properties and solvent solubility.
Other dicarboxylic acids include succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid,
Aliphatic dicarboxylic acids such as azelaic acid, having 12 to 12 carbon atoms
28 dibasic acids, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2
Alicyclic dicarboxylic acids such as methylhexahydrophthalic anhydride, dicarboxy hydrogenated bisphenol A, dicarboxy hydrogenated bisphenol S, dimer acid, hydrogenated dimer acid, hydrogenated naphthalenedicarboxylic acid, tricyclodecanedicarboxylic acid, hydroxy Hydroxycarboxylic acids such as benzoic acid and lactic acid.

In addition, polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and sodium 5-sulfoisophthalate may be used within the scope of the invention. May be used in combination. Also, after polymerizing the polyester resin, trimellitic anhydride,
An acid anhydride such as phthalic anhydride may be added later to give an acid value.

It is preferable that the polyester resin (B) of the present invention does not have a melting point (amorphous) from the viewpoint of adhesiveness, flexibility and solvent solubility.

The polyester resin (B) of the present invention may be a polyester resin other than the polyester resin (B) of the present invention, a polyester urethane resin, a polyether urethane resin, a polycarbonate urethane resin, a vinyl chloride resin. Vinyl acetate copolymer, epoxy resin, phenol resin, acrylic resin, polyacrylonitrile resin, polybutadiene resin, hydrogenated polybutadiene resin, nitrocellulose, cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP) Such modified celluloses and polyamide-imide resins may be blended as long as the properties are not deteriorated.

The polyester resin (B) is polymerized by a known method such as a transesterification method and a direct polymerization method. Further, a curing agent capable of reacting with the polyester resin (B) may be blended. The preferred amount of the curing agent is 1 to 10 parts by weight based on 100 parts by weight of the polyester resin (B). Although the kind of the curing agent is not limited, an isocyanate compound is particularly preferable in terms of adhesiveness and low-temperature bending resistance. Further, it is preferable that these isocyanate compounds are used after being blocked, from the viewpoint of storage stability. Examples of the curing agent other than the isocyanate compound include known compounds such as methylated melamine, butylated melamine, benzoguanamine, amino resins such as urea resins, acid anhydrides, imidazoles, epoxy resins, and phenol resins. These may be used alone or in combination.

As the isocyanate compound, aromatic,
There are aliphatic diisocyanate and trivalent or higher polyisocyanate, and either low molecular weight compound or high molecular weight compound may be used. 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 The amount and, for example, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, low molecular active hydrogen compounds such as triethanolamine or various polyester polyols, polyether polyols, polyamides By reacting with a high molecular weight active hydrogen compound, etc. Terminal isocyanate group-containing compounds to be.

Examples of the blocked isocyanate agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol and chlorophenol, and oximes such as acetoxime, methylethylketoxime and cyclohexanone oxime. Alcohols such as methanol, ethanol, propanol and butanol, ethylene chlorohydrin,
Halogen-substituted alcohols such as 1,3-dichloro-2-propanol, tertiary alcohols such as t-butanol and t-pentanol, ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propyrolactam And other active amines such as aromatic amines, imides, acetylacetone, acetoacetate, and malonic acid ethyl ester, mercaptans, imines, imidazoles, ureas, and diaryl compounds. And sodium bisulfite. Of these, oximes, imidazoles, and amines are particularly preferred over curability. These crosslinkers include:
A well-known catalyst or promoter selected according to the type can be used in combination.

The type of the solvent (D) used in the present invention is not limited, and examples thereof include ester, ketone, ether ester, chlorine, alcohol, ether, and hydrocarbon solvents. Among them, when screen printing is performed, a high boiling point solvent such as ethyl carbitol acetate, butyl cellosolve acetate, isophorone, cyclohexanone, and γ-butyrolactone is preferable.

The conductive paste of the present invention may contain known additives such as an antifoaming agent, a leveling agent, and a dispersant.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. In the examples, “parts” simply means “parts by weight”. Each measurement item followed the following method.

1. Reduced viscosity, ηsp / c (dl / g) 0.10 g of a polyester resin was dissolved in 25 cc of a mixed solvent of phenol / tetrachloroethane (weight ratio: 6/4) and measured at 30 ° C.

2. Molecular weight The number average molecular weight in terms of polystyrene was measured by GPC.

3. Glass transition point temperature (Tg) Measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC). As a sample, 5 mg of the sample was placed in an aluminum holding lid type container and crimped.

4. Acid value (mgKOH / g) 0.2 g of a sample was precisely weighed and dissolved in 20 ml of chloroform. Then, it was determined by titration with 0.01 N potassium hydroxide (ethanol solution). A phenolphthalein solution was used as an indicator.

5. Preparation of test piece Conductive paste with 100 μm thickness annealed PET
A pattern with a line width of 0.5 mm and a length of 75 mm (for bending resistance test) and a pattern with a width of 25 mm and a length of 50 mm (for specific resistance measurement, heat resistance measurement so that the film thickness after drying becomes 8 to 10 μm) , Moisture resistance measurement, and thermal shock resistance) were screen printed. Using a conveyor type far-infrared oven, the surface temperature of the
What was dried under the conditions of minutes was used as a test piece.

6. Specific resistance5. Using the test piece prepared in the above section, the film thickness and the sheet resistance film thickness were measured using a 4-deep needle resistance measuring instrument, and the specific resistance was calculated from these.

7. 4. Flex resistance The test piece prepared in the above was used at a low temperature of -30 ° C and a weight of 50.
Under the conditions of g / cm ² and R = 0, bending at 360 ° at the same location was repeated 5 times, and the resistance change rate of the conductor was evaluated. Flex resistance (%) = {(R−R ○) / R｝} × 100 where RＲ = initial circuit resistance R = resistance after flex test

8. Heat resistance 5. After heat-treating the test piece prepared in the above at 100 ° C. for 1,000 hours in a hot air oven, the adhesion of the conductor, the pencil hardness, and the low-temperature flexibility were evaluated.

9. 4. Moisture resistance 85% relative humidity 85%
After heat treatment in a thermo-hygrostat at RH for 1,000 hours, the adhesiveness of the conductor, pencil hardness and low-temperature flexibility were evaluated.

10. 4. Thermal shock resistance Test pieces prepared at -40 ° C and 85 ° C for 1 each
After being left alternately for a total of 1,000 hours, the adhesion of the conductor, pencil hardness, and low-temperature flexibility were evaluated.

11. Adhesion 5. The test piece created in Step 2 is a cellotape (registered trademark)
It was evaluated by a peel test.

12. Pencil hardness5. SUS30 2mm thick test piece
The sample was placed on four plates, measured using a high-grade pencil specified in JIS-6006 in accordance with JIS K-5400, and judged by the presence or absence of scratches.

Synthesis Example 1 (polyester resin I) 97 parts of dimethyl terephthalic acid, 97 parts of dimethyl isophthalic acid, 200 parts of polyhexamethylene carbonate (molecular weight 2,000) as an aliphatic polycarbonate diol, 1.5 parts −
198 parts of pentanediol and 0.102 parts of tetrabutyl titanate were charged and subjected to S-E exchange for 3 hours at 180 ° C. Next, the pressure is gradually reduced to 1 mmHg or less,
Polymerization was performed at 240 ° C. for 2 hours. The composition of the obtained polyester resin was as follows: terephthalic acid / isophthalic acid // 1,5-pentanediol / polyhexamethylene carbonate = 5
0/50 // 90/10 (molar ratio), the content of polyhexamethylene carbonate in the resin was 47% by weight, the reduced viscosity was 0.75 dl / g, the number average molecular weight was 25,000, and the acid value was 0.7 mg KOH / g. And a glass transition temperature of −18 ° C. The results are shown in Table 1.

Synthesis Example 2 (Polyester resin II) Synthesis example. In the same manner as in Example 1, a polyester resin II was synthesized.
The composition of the obtained polyester resin is terephthalic acid / isophthalic acid / 1,4-cyclohexanedicarboxylic acid //
1,6-hexanediol / polyhexamethylene carbonate = 50/30/20 // 93/7 (molar ratio), and the content of polyhexamethylene carbonate in the resin is 37.
0.55 dl / g reduced viscosity in weight%, number average molecular weight 1
It was 8,000, the acid value was 0.8 mg KOH / g, and the glass transition temperature was -21 ° C. The results are shown in Table 1.

Synthesis Example 3 (Polyester resin III) 97 parts of dimethyl terephthalic acid, 87 parts of dimethyl isophthalic acid, 140 parts of polyhexamethylene carbonate (molecular weight: 2,000) as an aliphatic polycarbonate diol, 140 parts, 1,6 −
228 parts of hexanediol and 0.102 parts of tetrabutyl titanate were charged and subjected to S-L exchange at 180 ° C. for 3 hours. Next, 10 parts of sebacic acid was charged, and transesterification was further performed. Next, the pressure was gradually reduced to 1 mmHg or less, and polymerization was performed at 240 ° C. for 2 hours. The composition of the obtained polyester resin is terephthalic acid / isophthalic acid /
Sebacic acid // 1,6-hexanediol / polyhexamethylene carbonate = 50/45/5 // 93/7
(Molar ratio), the content of polyhexamethylene carbonate in the resin was 36% by weight, the reduced viscosity was 0.65 dl / g, the number average molecular weight was 21,000, the acid value was 0.9 mg KOH / g,
Glass transition temperature was -29 ° C. The results are shown in Table 1.

Synthesis Example 4 (Polyester resin IV) Synthesis example. In the same manner as in Example 1, a polyester resin IV was synthesized.
The composition of the obtained polyester resin was terephthalic acid / isophthalic acid // 1,5-pentanediol / 1,6-hexanediol / polyhexamethylene carbonate /
1,4-cyclohexanedimethanol = 50/50 //
35/30/10/25 (molar ratio), the content of polyhexamethylene carbonate in the resin was 46% by weight, the reduced viscosity was 0.70 dl / g, the number average molecular weight was 25,000, the acid value was 0.7 mg KOH / g, Glass transition temperature was −11 ° C. Table 1 shows the results.

Comparative synthesis example. 1 (Comparative polyester resin V) Synthesis example. Comparative polyester resin V was synthesized in the same manner as in Comparative Example 2. The composition of the obtained polyester resin is as follows: terephthalic acid / isophthalic acid / sebacic acid // neopentyl glycol / 1,6-hexanediol = 50/20/30 //
14/86 (molar ratio), reduced viscosity 0.70 dl / g, number average molecular weight 24,000, acid value 1.1 mgKOH / g,
Glass transition temperature was -26 ° C. Table 2 shows the results.

Comparative synthesis example. 2 (Comparative polyester ether resins VI and VII) Comparative polyester resins VI and VII were synthesized in the same manner as the polyester resin I of Synthesis Example 1. Table 2 shows the results.

Comparative Synthesis Example 3 (Comparative polyester urethane resin VIII) Aliphatic polyester diol OD-X in a four-necked flask
100 parts of -688 (manufactured by Dainippon Ink and Chemicals, Inc.), 6 parts of neopentyl glycol as a chain extender, 2 parts of 1,6-hexanediol, 105 parts of methyl ethyl ketone, and 105 parts of toluene are charged, and the mixture is charged with nitrogen gas to 60 parts. C., 31 parts of diphenylmethane diisocyanate was further charged, and the mixture was slowly heated to 80.degree. C. and reacted for 5 hours until no residual isocyanate was detected. The resulting polyurethane resin had a reduced viscosity of 1.10 dl / g, a number average molecular weight of 38,000, an acid value of 0.2 mgKOH / g, and a glass transition temperature of -25 ° C. Table 3 shows the results.

Preparation of Silver Powder A-1 Commercial flake silver powder was used as it was. The average particle diameter (50% D) by a light scattering method is 4.5 μm, and the specific surface area is 0.4 μm.
It was 7 m ² / g.

Preparation of Silver Powder A-2 275 parts of a 37% aqueous silver nitrate solution and 220 parts of an 18% aqueous sodium hydroxide solution were reacted with stirring at 40 to 50 ° C., and after the reaction was completed, 70 parts of distilled water was added. did. Then, 60 parts of a formalin aqueous solution having a concentration of 23% was added thereto and reacted at 30 to 40 ° C. PH after the reaction is 8
Met. The obtained silver powder was filtered, washed and dehydrated repeatedly, replaced with methanol, and filtered.
It dried under reduced pressure for 4 hours. The obtained silver powder has a shape in which the spherical primary particles shown in FIG. 1 are three-dimensionally aggregated, the average particle diameter of the primary particles is 0.5 μm from a scanning electron micrograph, and The average particle size measured by a light scattering method was 11 μm, and the specific surface area was 1.62 m ² / g. The secondary particles are not destroyed in the three-roll dispersing step, and can maintain their structure.

Example 1 89 parts of silver powder A-1, 9.6 solids of butyl cellosolve acetate solution of polyester resin I, 1.4 solids of hardener, and 0.5 part of leveling agent were mixed and sufficiently premixed. Thereafter, the mixture was dispersed three times with a chilled three-roll kneader. 4. The obtained silver paste is Printed, dried and evaluated by the method described in (1). Specific resistance is 5.0 × 10 ⁻⁵ Ω · cm
Was good. Flex resistance is low temperature -30 ° C, R = 0,
The rate of change in resistance after five 360-degree bends was + 83%, and no disconnection was observed, which was very good. Also, heat resistance,
The moisture resistance and thermal shock resistance were also good. Table 4 shows the results.

In the same manner as in Example 1, the conductive pastes of Examples 2 to 5 were prepared and evaluated. Table 4 shows the results.

In the same manner as in Example 1, the conductive pastes of Comparative Examples 1 to 5 were prepared and evaluated. Table 5 shows the results.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

[Table 3] 1) OD-X-688 (manufactured by Dainippon Ink Industries, Ltd.)

[0059]

[Table 4] 1) Conductive carbon black (Lion Akzo Co., Ltd.)
2) Methyl ethyl ketoxime block of hexamethylene diisocyanate biuret trimer 3) Methyl ethyl ketoxime block of hexamethylene diisocyanate isocyanurate adduct

[0060]

[Table 5] 1) Methylethylketoxime block of hexamethylenediisocyanate biuret trimer 2) Methylethylketoxime block of hexamethylenediisocyanate isocyanurate adduct 3) Vinyl chloride / vinyl acetate copolymer (Union Carbide Co., Ltd.)

[0061]

The conductive paste of the present invention has excellent adhesion and flexibility to films such as polyethylene terephthalate, vinyl chloride, nylon, etc., metal substrates, glass substrates, etc., and cannot be obtained by conventional techniques. Has excellent durability such as excellent heat resistance, moisture resistance and thermal shock resistance. As a result, it is possible to meet high required quality in extremely severe fields such as electric products, electronic components, and applications between automobiles.

Continued on the front page F term (reference) 4J002 CF001 CG041 FA086 FD116 FD207 5G301 DA03 DA18 DA53 DD01 DD03

Claims (1)

[Claims] A conductive paste comprising a conductive powder (A), a binder (C) containing a polyester resin (B) having a number average molecular weight of 3,000 or more and a solvent (D) as main components, the polyester resin (B) Is a polyester resin containing an aliphatic diglycol and / or an alicyclic glycol having an aromatic dicarboxylic acid of 70 mol% or more of the total acid component and having a main chain carbon number of 5 or more and an aliphatic polycarbonate diol. A conductive paste, wherein the resin contains a polyester resin containing the polycarbonate diol in an amount of 5 to 80% by weight.